Transplantation of HIV+ organs: from ban to HOPE

Organ donation from HIV positive patients has been prohibited in the USA since 1988. Pre-transplant screening for HIV is mandatory using nuclear amplification test (NAT), though false negative results during “window period” are a potential concern in donor selection.

Elmi Muller spoke at our Transplant Grand Rounds yesterday and told us about the challenge she faces in South Africa, where HIV infection affects more than 15% of the population, HIV patients frequently develop HIV-associated nephropathy (HIVAN) and progress to ESRD. Moreover, the availability of renal replacement therapy (hemodialysis) is limited.

In the early 90's, there were a number of uncertainties related to transplanting HIV positive patients including the worrisome concern about introducing a donor-derived virus that could lead to out of control HIV infection (resistant strain?); the effect on the immune system of HIV infection in combination with immunosuppression (worse immunodeficiency?); and the financial burden of expanding the services of transplantation to HIV+ patients in a country with limited health budget.

Against all the odds, Elmi performed four cases of HIV positive kidney donors to HIV positive recipients in South Africa in 2008. No IRB approval... Elmi reported having some intuition that it would work and she was in touch with other physicians around the world who shared her view. In her side, HIV resistance rate is very low in South Africa.

After performing those transplant, her colleagues and the hospital prosecuted her and banned her from performing surgery for more than 1 year. This past week, the HIV Organ Policy Equity (HOPE) Act was approved by the US Congress, permitting donation from HIV-positive organs to HIV-positive recipients. It took time but she is now recognized as a pioneer in the field and her courage to perform those surgeries were remarkable. The law that passed will help expand the availability of organ donors to HIV positive patients and will help with organ shortage.

Some challenges though still remain. HIV resistance is much higher in the States (~19%) and HIV+ transplant recipients experience a higher rate of rejection and significant difficulties with drug-drug interactions (P450 inhibitors). Details about a recent trial can be reviewed on this prior blog. In contrary to the idea of over-immunosuppression, recent paper suggests that ATG may be a better induction therapy choice for these patients. Closely monitoring of these patients will be essential as we learn more about HIV and transplantation. By bending rules, Elmi changed a transplant policy and made history.

Naoka Murakami
Leo Riella

Induction Therapy in Kidney Transplantation - Summary

Most kidney transplant centers in the United States utilize induction agents as part of their immunosupression protocols. The reasoning behind is that induction therapy has been shown to reduce the rate of acute rejection, however no trial has yet demonstrated an improvement in long-term graft survival.  Induction therapy has also expanded in centers using steroid-withdrawal protocols and in patients with expected delayed graft function due to prolong ischemia time (ECD/DCD kidneys), since calcineurin inhibitor initiation may be delayed (significant vasoconstriction from CNI may potentially delay recovery).

Rabbit antithymocyte globulin (rATG or Thymoglobulin) is the most common agent used in more than 55% of transplant cases in the USA, despite not being FDA-approved for this use (only for treatment of severe cellular rejection). Curiously, rATG is prepared by immunizing pathogen-free

rabbits with a cell suspension of human thymic tissue (thymocytes). After immunization, the serum is harvested from rabbits and immunoglobulins against thymocytes are isolated and subjected to a number of purification processes. Samples from more than 26,000 immunized rabbits are pooled to achieve a high level of batch-to-batch consistency!

Our center uses ATG for induction in high immunological risk patients and Basiliximab for low risk patients in combination with tacrolimus and MMF for maintenance. Steroid withdrawal is performed on most patients by the end of first week post-transplantation, with the exception of highly sensitized patients.

Below a summary table of the 3 most common induction agents in clinical use today, their target cells, dose, cost and side effects.

Antibody	Brand	Class	Lymphocyte depleting	Antigenic Target and Cells	Typical prescription	Side effects
Basiliximab	Simulect (Novartis)	Monoclonal	No	IL2 receptor (CD25)   Activated T cells	20mg x2 doses  U$4,254	Hypersensitivity reaction (rare)
Rabbit antithymocyte globulin	Thymoglobulin (Genzyme)	Polyclonal	Yes	Multiple Ag   Mainly T cells, to a lesser extent B and NK cells	1.5mg/kg 3-7 doses  U$7,824-18,256 Premedicate with steroids and Tylenol Decrease dose if WBC<3 or="" ptls="" span="">	Fever, chills, dyspnea, nausea, diarrhea, headache, general pain and pulmonary edema (cytokine release syndrome)
Alemtuzumab	Campath 1H (Berlex Laboratories)	Monoclonal	Yes (more prolonged)	CD52 Ag T, B and NK cells, monocytes, macrophages, dendritic cells, eosinophils, mast cells	30mg x1 dose  U$2,065	Generally none when given subcutaneously

More details about the use of induction therapy in transplantation on this prior blog

Renal transplant across an ABO barrier

A 24 year-old ESRD patient secondary to IgA nephropathy has been on HD for almost one year. His mother is a potential donor for living related kidney transplant. The condition seemed perfect—zero mismatch on HLA, no PRA, no DSA—except for ABO-incompatibility. Type O in the recipient and type A in the donor.

What are ABO antigens, and where are they expressed?
 ABO antigens, discovered by Karl Landsteiner in 1901, are glycoprotein antigens, expressed not only on the surface of red blood cells, but also on endothelial cells, and epithelial cells.

Why is ABO incompatibility a relative contraindication to transplantation? 
As noted above, ABO antigens are expressed on the donor kidney, and can be a target of antibody-mediated rejection. The first ABO-incompatible kidney transplant (ABOi KT) was performed in mid 1950s and ended up with hyperacute rejection (HAR). Therefore, this procedure was considered as a contraindication until recently. The concept of depleting anti-AB Abs was introduced in early 1980s, leading to successful ABOi KT by Alexandre et al., followed by great effort in Japan to improve outcomes, where ABOi KT now consists of 30% of living donor KT. Nowadays, ABOi KT is becoming a reasonable option in the US as well.

What is the usual immunosuppressive protocol to transplant these patients? Are ABO antibody titers important for determining the feasibility of transplant? 
Unfortunately, there are no randomized controlled trials for the pre-transplant conditioning regimens for ABOi KT. However, the basic idea of overcoming ABO-incompatibility is decreasing the circulating ABO antibodies via combination of (1) antibody depletion (e.g. plasmaphresis) (2) IVIG, (3) Rituximab or splenectomy. Pre-transplant ABO antibody titers should be taken into consideration, which generally should be 1:16 or lower, although the number is exclusively based on empirical evidence. Interestingly, there may be no correlation with baseline antibody titers and graft survivals. For maintenance immunosuppressive regimen, therapy, there is no need for higher intensity of immunosuppression compared to ABO compatible KT.

What are the potential complications?
Initially, HAR was the largest concern for ABOi KT, but is not major concern with the use of current desensitization protocols . Antibody-mediated hemolysis and delayed antibody-mediated rejection are potential complications. Therefore, post-transplant monitoring of AB antibody titers is usually recommended. Of note, however, in the setting of ABOi KT, peritubular capillary C4d deposition alone is not diagnostic as this can be observed even in 80% of fully functioning grafts, called “accommodation”, the mechanism of which is not fully understood.

How good are the long-term outcomes of transplants crossing an ABO barrier? 
Reports showed long-term graft survival of ABO-incompatible renal transplants are the same as those of ABO-matched transplants. One report from Japan showed that the overall patient survival rate was 97% for the first year and 95%, 93% and 90% for 3, 5 and 9 years after surgery, respectively. The 1-year graft survival rate was 93%, and that for 3, 5 and 9 years was 89%, 84%, and 72%, respectively. Of note, Montgomery et al.  reported no difference in long-term patient survival but suggested more graft loss in the first 14 days after transplantation.

Going back to our case, the patient went through plasmapheresis and two doses of rituximab injections (150 mg/m2, on POD #-14 and -1) as a pre-conditioning regimen. This was followed by a successful ABOi KT using Basiliximab as induction therapy, FK/MMF/Prednisone as maintenance regimen with excellent graft function months after transplant.

Naoka Murakami
Leonardo V. Riella

Retroperitoneal leak in PD patient

Ultrafiltration failure is a frequent clinical problem in PD patients. The most common etiologies are: fast peritoneal membrane transport, loss of peritoneal surface membrane and high lymphatic absorption. Mechanical and anatomical etiologies are occasionally seen.

Rule of 4's is used to diagnose membrane ultrafiltration failure: less than 400ml UF using 4.25% bag after 4 hours.

Sudden onset of ultrafiltration failure may occur in the setting of peritoneal leakage. Though sometimes associated with localized subcutaneous edema, it is generally difficult to detect clinically. Retroperitoneal leakage is likely to arise from a tear or a gap in the peritoneum precipitated by an increase in intra-abdominal pressure associated with walking, coughing, straining, or using a high instilled volume (2.5 L or 3 L). Red flags may include history of hernia, pleuroperitoneal communication and large infusion volumes. The acute onset of ultrafiltration failure is another suggestive finding.

Best diagnostic modality is MRI (PD fluid can be used as constrast medium).



Management: involves interruption of PD. But few reports have achieved success by using fast cycles (1hour/exchanges x8) twice a week and leaving abdominal cavity empty between sessions for 4-8 weeks.

Electrolyte Disorders involving Tubular Channels

Though adult nephrologists infrequently encounter these disorders in clinic, the Board Exam loves them. Below a short table describing some of these gain- and loss-of-function channel disorders that are worth remembering. The diuretic-targeted channels are shown under parenthesis as a reference.

MDRD vs CKD-EPI in Transplantation

With the results of the eAJKD brackets posted by Gearoid, I thought this article might be pertinent to stimulate further the debate... This article just came out on Transplantation and is a well designed study in which the performance of the CKD-EPI equation is compared with the MDRD Study equation in 825 stable kidney transplant recipients.
GFR was measured by urinary clearance of inulin (n=488) and plasma clearance of 51Cr-EDTA (n=337).
The results showed that bias was significantly lower for MDRD Study equation compared with CKD-EPI creatinine to estimate the GFR. This superiority translated into a better accuracy (80% and 74% for the MDRD and CKD-EPI creatinine, respectively). The best performance of the MDRD Study equation was confirmed both in the subgroups of patients with mGFR below 60 mL/min/1.73 m2 and between 60 and 90 mL/min/1.73 m2. For mGFR above 90 mL/min/1.73 m2, there were no significant differences between the two equations in terms of performance.
The data also bring us back to the main concern about using creatinine and how poor of a marker it is for renal function. About 30% are misclassified in the CKD stages...  The battle is far from over...

High Salt-Intake and Autoimmunity

The incidence of auto-immune diseases has dramatically increased in the past 50 years and the concern that environmental exposures have contributed to this increase is broadly suspected. However, it is very hard to pin-point to an individual factor. 

Very intriguing observations were just published at Nature linking a high-salt intake to increased auto-immunity. The authors demonstrate that a high-salt diet increased the severity of experimental autoimmune encephalomyelitis (*EAE) - a mouse model of multiple sclerosis . The authors proposed that high salt-intake induces serum glucocorticoid kinase 1 (SGK1), which than promotes IL-23R expression and enhances TH17 ** cell differentiation in vitro and in vivo. SGK1 has has been shown to govern Na transport and salt (NaCl) homeostasis in other cells. Mice lacking this kinase in their T cells have impaired expression of IL-17-family cytokines and of a receptor for another cytokine molecule, IL-23, which stabilizes the TH17 cell phenotype.

Though salt might not be the trigger of autoimmunity, the possibility that high-salt intake might exacerbate auto-immunity is very provoking and would encourage even more the emergent initiation of trials evaluating the efficacy of low salt-diet in the development of auto-immune diseases and other potential diseases related to inflammation, such as coronary heart disease. 

Based on recent computer-generated data suggesting all the potential benefits of lowering salt consumption, this discussion is very pertinent.  

Above the diagram from the Editorial of Nature discussing the findings and below some additional explanations about the mouse model and Th17 cells. One caveat is that effect of high sodium on human cells was only shown in vitro...

* EAE: Experimental autoimmune encephalomyelitis. An animal model of the human autoimmune disease multiple sclerosis. EAE is experimentally induced in animals by immunization with myelin or with peptides derived from myelin. The animals develop a paralytic disease with inflammation and demyelination in the brain and spinal cord.

** TH17 cells (T helper 17 cells). A subset of CD4+ T helper cells that produce interleukin-17 (IL-17) and that are thought to be important in inflammatory and autoimmune diseases. Their generation involves IL-6, IL-21 and IL-23, as well as the transcription factors RORgt (retinoic-acid-receptor-related orphan receptor-gt) and STAT3 (signal transducer and activator of transcription 3).

Vascular rejection – Reassessing its etiology

Vascular rejection has been traditionally considered a severe form of acute rejection characterized by infiltration of mononuclear cells beneath the endothelium or by the presence of arteritis. Though initially reported as an aggressive form of T-cell mediated rejection with poor response to T-cell targeted therapy, newer findings suggest a strong association with alloantibodies. 

 Study from France analyzed 302 patients with biopsy-proven rejection and identified 4 subtypes of acute rejection with different outcomes (Figure): T-cell-mediated vascular rejection (9%), antibody-mediated vascular rejection (21%), T-cell-mediated rejection without vasculitis (46%), and antibody-mediated rejection without vasculitis (24%). Antibody-mediated vascular rejection manifested a median of 1.1 months (0.4–4.4) post-transplant and had the worst prognosis of the four subtypes. Moreover, 71% of cases of vascular rejection, which were mostly graded as v1 and v2 arteritis by the Banff schema, were associated with donor-specific antibodies (DSA). 

Therefore, it seems that the majority of cases of vascular rejection are associated with DSA and therapies to remove and decrease alloantibody production may be warranted. Indeed, this study suggested that antibody-directed treatment involving plasmapheresis, IVIG and rituximab led to better outcomes in this subpopulation. As of today, v1 and v2 vascular lesions are not accounted by the Banff classification in the antibody-mediated rejection category. 

Alloantibodies may bind to endothelium antigens and activate complement, attracting mononuclear cells which express Fc and adherence receptors, initiating the process of vascular infiltration. 

How will this affect our practice? Whenever a biopsy shows a component of vascular rejection, one must send the serum for alloantibody testing, even if biopsy is not classic for antibody-mediated rejection. Furthermore, antibody-directed treatment strategies should be considered, in particular if no response to initial therapy and evidence of DSA. The ideal treatment of the different severities of vascular rejection still remain to be determined.

CNS mass and crystals after kidney transplantation

A gentleman with ESRD secondary to polycystic kidney disease comes in with vomiting and headache eight months after kidney transplantation. Brain MRI shows a small single enhancing lesion in the temporal lobe. Lumbar puncture reveals an elevated opening pressure (41), WBC 121 (77% lymphs), elevated total protein (210) and low glucose (41). Cultures are negative. 

The top 3 differentials of CNS masses in post-transplant kidney recipients are: neurotoxoplasmosis, lymphoma and tuberculoma. EBV negative status prior to transplantation increases your risk of post-transplant lymphoproliferative disorder (PTLD) and checking EBV VL could help with initial evaluation. Coming from endemic areas of tuberculosis (TB) raises the suspicion for tuberculosis. TB in kidney transplant recipients is a particular challenge both diagnostically and therapeutically. Atypical clinical presentations (extra-pulmonary) and negative tuberculin skin tests/sputum smears are frequent. The treatment of TB also has its own challenges, which include pharmacokinetic interactions between immunosuppressive and antituberculous medications (reduction of FK by more than 60% is required), allograft-related drug toxicities, and inadequate immune responses to Mycobacterium tuberculosis due to exogenous immunosuppression. 

In general, empirical therapy of neurotoxoplasmosis is instituted in immunosuppressed patients with an enhancing brain lesion, consisting of sulfadiazine, pyrimethamine and leucovorin. Reduction of immunosuppression is also indicated and follow up imaging is performed. Last resource if no improvement and negative work up is to perform a brain biopsy to obtain tissue specimen. 

Treatment of neurotoxo with high doses of sulfadiazine may precipitate acute kidney injury by crystal formation (~30% of patients), in particular if volume depletion is present and urine pH is 5.5 or less. Intra-renal crystalluria may be prevented by maintaining fluid intake above three liters per day (PO or IV). Monitoring of serial urinalyses for the development of crystalluria is recommended. For those developing crystalluria, intravenous bicarbonate solution to alkalinize the urine (goal pH above 7.15) is administered. The patient above developed significant AKI (creatinine increased from 1 to 4) after sulfadiazine treatment and crystals were identified in the urine (representative figure). 

Be aware of potential drugs/toxins** that might form intratubular crystals and precipiate AKI. Act pre-emptively with fluid hydration +/- alkalinization of urine depending on the toxin. 

 ** Acyclovir (IV), sulfonamides, ethylene glycol, high dose vitamin C, methotrexate, protease inhibitors, phophate enemas, orlistat 

 *** Remember that for MTX renal toxicity, there is glucarpidase as a last resource to quickly reduce MTX levels in patients with AKI and persistently high MTX levels 48 hrs after dosing.

Stress test for renal transplant candidates: select or screen all?

We have previously discussed cardiovascular mortality after transplantation. But one controversial aspect in the evaluation of potential kidney recipients is the performance of stress tests for risk stratification. With the cost of stress tests ranging from U$2,500-5,000 and the long waiting time for a kidney transplant on the deceased donor list, this is a particular important point for financial, medical and logistical reasons. 

To evaluate that, De Lima et al. studied the prognostic value of myocardial scintigraphy in 892 consecutive renal transplant candidates classified into four risk groups: very high (aged ≥50 years, diabetes and CV disease), high (two factors), intermediate (one factor) and low (no factor). After a median follow up of 22 months, 181 major CV events were observed (overall incidence = 20%): 12 (6.6%) in low-risk, 51 (28.2%) in intermediate-risk, 61 (33.7%) in high-risk and 57 (31.5%) in very high-risk patients (p below 0.0001; Figure below). This simple classification was able to nicely separate the different groups according to incidence of major CV events.

The prevalence of abnormal scan increased with the degree of risk, from 12.7% in low-risk patients to 50.8% among very high-risk subjects. Interestingly, only in patients with one risk factor (either age ≥50 years, diabetes or CV disease) was an altered myocardial stress test associated with an increased incidence of major CV events [30.3 versus 10%, hazard ratio (HR) = 2.37; p below 0.0001). Low-risk patients did well regardless of stress test results, while in patients with 2 or 3 risk factors, altered stress test did not add to the already increased risk for future CV events. 

The question that remains is whether an invasive intervention could lower the CV events in the high-risk groups and if coronary angiography should be considered instead of stress test, as proposed by some. The cost, invasiveness and risk of the procedure would likely be unwarranted until a randomized trial show benefits of revascularization in ESRD pts compared to medical management. It is important to remember that most clinical trials addressing this question excludes ESRD patients so we must extrapolate data from the general population, which do not support intervention in asymptomatic patients. An upcoming randomized controlled trial is addressing this question in transplantation: COST trial.

Until then, we have to base our decisions on observational/restrospective data and poor evidence-based guidelines. My personal approach has been not to screen low risk patients with stress test anymore but I am still performing stress tests for the intermediate and high risk patients. The reason to do a stress test on a high risk patient is not to assess for the presence or not of CV disease, but to attempt to identify a large defect, exercise-induced hypotension or angina that might warrant intervention prior to transplantation. Among the stress tests, I usually recommend a MIBI protocol with sequential exercise followed by pharmacological (if HR goal not achieved), which allows for evaluation of patient's exercise capacity and cardiac imaging to determine the burden of CV disease. For obese patients, PET may give you better images. 

To provoke even more the debate, Diamond et al. supports the approach of: "test no one and treat  everyone" for asymptomatic diabetic patients compared to "screen everyone and treat only those with an abnormal test". The authors believe that optimal medical interventions such as statins/beta blocker are sometimes ignored after a normal stress test (high false negative rate), missing an important point of intervention, which could be more cost-effective than the screening strategy. Definitely lots of fuel for more debate...

  

Medication Nonadherence in Renal Transplantation: Barriers and Consequences

It is surprising how high the nonadherence rates for immunosuppressants is among renal transplant recipients, ranging from 15 to 40%, despite the potential impact of nonadherence and the degree of education provided to transplant recipients.

Nonadherence to immunosuppressive medications is associated with increased incidences of allograft rejection and a seven-fold increased risk of graft failure as compared to adherent patients. Approximately 20-25% of nonadherent renal transplant recipients develop a late rejection at five years posttransplant, frequently antibody-mediated, as compared to 5-8% of adherent patients. Even a short period of nonadherence to immunosuppressive medications can initiate the rejection process.

Identifying possible barriers to adherence and intervening accordingly is necessary for improving transplant outcomes. One of the well-studied barriers is the complexity of the immunosuppressive regimen. Choosing a simpler regimen among possible effective regimens is likely to provide convenience to patients and; therefore, improve adherence. In addition, forgetfulness is one of the most common causes of missed doses. Nonadherence is more prevalent in patients with comorbidities that can cause impaired cognitive function. 

Some interventions to improve adherence include: associating medication administration times with a daily activity (such as meals, waking up, or going to bed), using pill boxes, and setting alarms or voice reminders that help patients remember to take their medications at the right times.

Ineffective communication may also increase the probability of intentional nonadherence due to a poor understanding of the benefits and risks associated with the patients’ prescribed medications. Most medications used in the transplant setting are preventive, and patients do not perceive the benefits of the medications immediately, which may facilitate nonadherence. Although fear of developing side effects can complicate patients’ nonadherence, patients are more likely to be adherent to a medication when they are aware of its possible adverse effects, which highlights the importance of educating patients. High drug costs can limit patients’ access to medications and increase nonadherence rates. Even with Medicare part B coverage, there are significant copays for patients without secondary insurance. Also, even if patients have prescription drug coverage, the high number of medications needed for some transplant patients can result in high monthly out-of-pocket expenses. This ongoing financial burden is substantial for most patients, and could act as a barrier to adherence when it is not addressed and adjusted. 

It is imperative for renal transplant recipients to adhere to medication regimens, as it can directly affect outcomes. Clinicians should assess adherence at every follow-up and keep in mind possible barriers to medication adherence, in particular, complexity of regimen, financial burden and lack of knowledge of potential consequences of nonadherence.

Miae Kim, PharmD, PGY2 Resident in Transplant Pharmacy

Steven Gabardi PharmD, FCCP, BCPS, Organ Transplant Clinical Specialist at BWH

Diagnosis and Management of Post-Transplant Fluid Collections

We were evaluating a kidney transplant recipient three weeks after surgery who presented with a rise in creatinine. We obtained an ultrasound which showed a large fluid collection and mild hydronephrosis. Prograf level was at goal. 

Peritransplant fluid collections may be produced by lymphoceles, urinomas, hematomas or abcesses. These collections may compress the ureter leading to hydronephrosis or may compress the renal vein causing a “compartment-like syndrome”. Since his creatinine was risen, we decided to drain the fluid collection. An important point is that mild hydronephrosis is reported in a large portion of kidney transplant ultrasounds and intervention is usually driven by the clinical setting. When in doubt, serial ultrasounds indicating progressive dilatation or the use of nuclear medicine imaging showing normal perfusion and parenchymal uptake but pooling of tracer in the renal pelvis with prolonged pelvic retention helps in confirming the diagnosis. 

His INR was 2.1 due to coumadin for a history of multiple clotted fistula. The interventional radiologist requested that we give FFP to reduce his INR to below 1.5 before considering the procedure. It was late Friday so we got 4U of FFP in and repeated INR. We were hoping that 4U of FFP would quickly reverse his mildly elevated INR. Interestingly, data supporting that is lacking. 

FFP can have an INR as high as 1.5 and transfusion of FFP will have little effect on minimally elevated INRs (Gearoid actually pointed that out in rounds). A study of the use of FFP in 121 patients with an INR in the range of 1.1 to 1.85, showed that correction of the INR to normal was achieved in only one patient (0.8 percent) and correction at least halfway to normal in only 15 percent. The median decrease in the PT and INR was 0.2 seconds and 0.07, respectively, and was independent of the number of units of FFP infused (median 2 units; range 1 to 20). Thus, available studies do not support the efficacy of FFP in treating bleeding or as prophylaxis for invasive procedures in patients with a mild coagulopathy (ie, INR below 2.0). 

After some discussion with IR, they agreed to go ahead with the procedure with an INR 1.9. About 600cc of yellow fluid was drained. Fluid creatinine was checked and was similar to serum level, ruling out an urinoma. This patient’s fluid collection was a lymphocele, which is the most common cause of peritransplant fluid collection due to disruption of renal lymphatics. It usually occurs weeks after surgery and drainage is required only in cases of suspected obstruction. With time, the amount of fluid collection tends to subside. Soon after drainage, his creatinine started to come down confirming the cause of his worsening renal function.

Figure: large peri-transplant fluid collection with associated hydronephrosis.

Acute rejection: what do the circulating cells have to say about it?

One of the frequent situations that we face in the renal transplant clinic is the patient in otherwise good condition who presents with a slight rise in serum creatinine. Although this is sometimes due to reversible causes, such as high CNI levels or dehydration, acute rejection is of course in the differential. 

The fact that we still rely on an invasive procedure – the graft biopsy – for formal diagnosis of rejection clearly limits our ability for repetitive monitoring and potentially delays treatment. There is no doubt that a simple, non-invasive assay to monitor the immune status would be of great help in the day-to-day practice. Indeed this is currently a field of intense research in transplantation. We recently provided new insights into this issue. We optimized a simple assay to determine the level of activation of circulating blood mononuclear cells in renal transplant recipients. The method is relatively straightforward: peripheral blood is collected, cells are isolated and incubated overnight; cytokine production by the cultured cells is measured in the cell supernatant. The main objective was to determine if this assay, when used in patients for whom a biopsy was performed for an acute rise in serum creatinine, could identify those that would show histological signs of rejection. We found that the measurement of a single cytokine, IL-6, can predict rejection with a sensitivity of 92% and specificity of 63%. This tool could thus potentially be used to exclude rejection, which would be particularly helpful for low-risk or remote patients. 

Where do we go now? 

This work is a first step towards the development of a clinically useful tool. Ideally, a non-invasive test would be able to identify acute rejection well before the serum creatinine starts to rise. To achieve this, we now need to collect blood samples and study cell activation serially post transplant. What we need to determine more precisely is when the cells become activated before the usual signs of graft dysfunction occur. This will allow us to identify rejection early and by doing so, to prevent further graft damage. Although this sounds simple, from a research perspective this next step implies an enormous investment of human and lab resources. 

Sacha De Serres
Leonardo Riella 

Antibody-Mediated Rejection: Choose your weapons

Acute humoral or antibody-mediated rejection (AMR) is attributed to the presence of alloantibodies against the graft, which could be either antibodies against human leukocyte antigens (HLAs) Class I and/or II , non-HLA antigens or endothelial antigens. Diagnosis of AMR is made through tissue biopsy and presence of alloantibodies. Early treatment is of paramount for the preservation of graft function. Treatment strategies include removal of alloantibodies, decreasing or stopping production of alloantibodies, or attenuating the immune systems response to alloantibodies. 

Plasmapheresis/Plasma Exchange 

Removal of alloantibodies is done through the use of plasmapheresis/plasma exchange or immunoadsorption. Plasmapheresis, or removal and replacement of one plasma volume, is effective at removing approximately 60% of the intravascular IgG which accounts for about 75% of the intravascular immune response. Extravascular IgG equilibrates in about 48 hours thus reducing total body IgG concentrations and reducing the effective immune response. Immunoadsorption works similarly to plasmapheresis except that plasma immune complexes and IgG are removed via protein A bound silica matrices. In the latter, the remaining plasma components are returned to the patient without the need for plasma exchange. FFP is needed even on the first run of plasmapheresis if recent biopsy was performed (prevention of bleeding). The cost of 5 treatments is about $4,600. 

Intravenous Immune Globulin 

Infusion of intravenous immunoglobulins (IVIG) has been studied at doses of 10 grams to 2 gm/kg as monotherapy or in conjunction with plasmapheresis or B-cell depleting agents. The mechanism of action is not entirely known but it is thought that neutralization of alloantibodies occurs when bound by the anti-idiotypic antibodies in IVIG as well as diminished plasma cell production by increasing total body concentrations of immunoglobulins and direct T-cell and complement cascade effects. Cost for IVIG is $77.06/gm resulting in $770.60 or $10,788.40 (dose intensity), based on a 70kg patient for each dose. 

Decreasing or stopping the production of alloantibodies requires therapies directed against mature plasma cells, memory B-cells or plasmablasts. Targeting memory B-cells or plasmablasts has a delayed onset of action as this therapy prevents new plasma cells from being formed but does not affect currently active ones. 

Rituximab 

A chimeric anti-CD20 monoclonal antibody, is dosed 375 mg/m2 or 1000 mg IV and given for one to two doses. The CD20 receptor is found on the surface of B-lymphocytes, including memory B-cells and immature plasmablasts, but not plasma cells. Rituximab has cytotoxic activity directly reducing B-lymphocyte and antibody levels. Cost for therapy ranges from $4,923.78 for dosing based on normal body surface area to $7,589.64 for a 1000mg dose. 

Bortezomib 

A proteasome inhibitor, is dosed 1.3 mg/m2 IV and given for four doses on days 1, 4, 8, and 11. Proteasome inhibition prevents protein biosynthesis resulting in apoptosis of the plasma cell and cessation of alloantibody production. Cost per dose based on a normal body surface area is $1,134.27. 

Eculizumab 

A humanized monoclonal antibody directed against C5, is dosed 600mg to 1200mg IV and administered weekly depending on alloantibody concentrations. Prevention of AMR is mediated by inhibition of membrane attack complex formation and halting activation of the complement cascade. Eculizumab is supplied as a 300mg vial for $6,638.40 or $13,276.80 to $26,553.60 per dose. 

Increasing the dose of maintenance immunosuppressive agents, including calcineurin inhibitors, antimetabolites, and steroids are also used to attenuate the immune system and help alleviate AMR. With all of the available treatment options, a multimodal approach is usually recommended to maximize chances of preventing graft injury. However, as you might see from the numbers above, careful clinical decision must be based on both efficacy and cost in order to responsibly avoid collapsing our already broken health care system. Instead of each center using its on protocol, our society should get together and perform a randomized trial with those interventions. Though I doubt this will happen any time soon, in particular with all the NIH budget cuts...

David Reardon, PharmD, PGY2 Critical Care Resident

Steve Gabardi, PharmD

Leonardo V Riella MD PhD (editing role)

Combined heart-kidney transplant - when less is enough

A 50 yo male with non-ischemic cardiomyopathy with ejection fraction of 15% presented with worsening dyspnea and renal failure (Cr 3 mg/dl). He was started on inotropes and was evaluated for heart transplantation.

Nephrology was called since the treating physician thought this patient might benefit from a combined heart-kidney transplant. The presented argument on the first phone call was that by doing a combined transplant, we would decrease the need for a repeat surgery in the near future for a kidney transplant and possibly benefit of the lower rejection rate provided by combined organ transplantation.

In the past, renal failure was considered a contraindication for heart transplantation. Nowadays, we realize that many of these patients have a considerable improvement in renal function once the cardiac output is optimized with the new heart. However, can we predict which patients might require a combined kidney/heart transplant rather than a heart alone?

There are no randomized trials but a nice retrospective analysis from Columbia University suggest that neither the cause of heart failure nor the level of creatinine or proteinuria could reliably predict the renal pathologic diagnosis or the degree of tubular atrophy/interstitial fibrosis (TA/IF) of the native kidneys. The figure below shows the absence of correlation between eGFR at time of transplant and extent of TA/IF.

For example, two patients with ischemic cardiomyopathy, minimal proteinuria (100 mg/24 hr) and eGFR of 27.0 and 29.0 mL/min had TA/IF of 50% and 5%, respectively. Therefore, it seems prudent to perform a kidney biopsy on these patients. Certainly, other factors such as a prior high creatinine value and chronic changes on imaging could help, but based on the scarcity of organs, I believe the more information you have, the best decision you will make regarding organ allocation.

Overall, patients that undergo combined heart-kidney transplant (HKT) do well and the rejection rate is lower than after a single transplant. The immunological explanation might be related to an increase number of circulating donor leukocytes that could induce a microchimerism and promote tolerance. However, this simplistic theory is not accepted by all. Patients with significant renal scarring are probably the ones who might benefit the most of combined HKT. In addition, a retrospective analysis of UNOS data suggested that low-risk heart transplant recipients with eGFR less than 30 ml/min would benefit the most (as an example, a younger patient not on LV assist device and not dialysis-dependent). More info here.

The patient above had a kidney biopsy that showed ischemic nephropathy with less than 5% fibrosis. He was listed for a single heart transplant. His creatinine went down to 1 mg/dl one month after his heart transplant.

The ABCs of ADME in AKI

The pharmacokinetics of a drug refers to the study of the absorption, distribution, metabolism and elimination of that drug (often referred to as ADME). Each of these characteristics can be greatly altered in a patient presenting with acute kidney injury (AKI). Historically, dosing in AKI has not been distinguished from that of chronic renal insufficiency (CRI). Newer evidence suggests that pharmacokinetic alterations differ between AKI and CRI, and; therefore, dose adjustments may also be different.

Absorption

The bioavailability of a drug can be influenced by GI transit time, gastric pH, and intestinal drug metabolism. Gastric pH can be increased in patients presenting with AKI, which may decrease dissolution and ionization of the oral drug and lead to reduced absorption. In CRI, intestinal metabolism can be reduced potentially resulting in increased absorption. The effect of AKI on intestinal metabolism has not been well-studied.

Distribution

Drug distribution is dictated by many factors, one of which is a medication’s ability to bind to plasma proteins, such as albumin. Patients with AKI may present with low serum albumin levels, leading to a higher free-fraction of albumin-bound drugs (e.g. warfarin, phenytoin, valproic acid, and salicylates) and consequently, increased biological effect.

Other factors affecting drug distribution include serum pH and fluid status. AKI is frequently associated with acidosis, which may affect the ionization and ultimately the distribution of the drug into the tissues. Lastly, increase in fluid volume in the blood can lead to low drug concentrations.

Metabolism

Many drugs undergo metabolism prior to elimination. A myriad of co-morbid conditions frequently associated with AKI may affect drug metabolism such as liver and cardiac dysfunction. Non-renal clearance can be decreased in the setting of CRI, possibly due to a chronic accumulation of uremic by-products causing an impairment of drug metabolic enzymes. As this is a chronic process, the same may not hold true in the early stages of AKI.

Elimination

AKI may have opposite effects on drug elimination. While significant nephrotic syndrome may increase the clearence rate of large molecules and highly protein-bound drugs, acids and bases may accumulate in AKI and compete for transporters, thus diminishing tubular secretion of drugs eliminated by anionic and cationic transport systems.

In sum, the pathophysiologic process in AKI is different from that of chronic CRI, and the pharmacokinetic parameters of medications may differ in the two disease states. Therefore, drug dosing principles studies in CRI may not hold true for patients presenting with AKI, and further research will be necessary to ensure proper dosing of medications in AKI and better guide us in our daily clinical decisions.

Craig A. Stevens PharmD, PGY1 Pharmacy Practice Resident

Steven Gabardi PharmD, BCPS, Organ Transplant Clinical Specialist at BWH

References

Zhang Y, Benet LZ. The gut as a barrier to drug absorption: combined role of cytochrome P450 3A and P-glycoprotein. Clin Pharmacokinet 2001;40:159-68.
Klotz U. Pathophysiological and disease-induced changes in drug distribution volume: pharmacokinetic implications. Clin Pharmacokinet 1976;1:204-18.
Power BM, Forbes AM, van Heerden PV, Ilett KF. Pharmacokinetics of drugs used in critically ill adults. Clin Pharmacokinet 1998;34:25-56.

Isolated C3 deposits on an inflammed glomeruli

Six months after a kidney transplant, a patient developed a rising creatinine, significant proteinuria (~2g/day), hematuria and low C3 levels. A kidney graft biopsy showed severe glomerulonephritis with mostly occluded capillary loops with immunofluorescence staining negative for immunoglobulins but strongly positive for C3 (representative picture on left). On EM, subendothelial and mesangial electron dense deposits were visualized. The features are characteristic of the so-called C3 glomerulonephritis (GN).

C3 GN is part of the same family as dense deposit disease (DDD) and fall into the new proposed classification of C3 glomerulopathy. Compared to C3 GN, DDD is characterized by extremely electro-dense intra-membranous deposits on EM. Both entities can present with features of MPGN, once significant chronic endothelium glomeruli damage occurs. These glomerular pathologies shared in common its pathogenesis, which involves complement dysregulation.

Classically, immunoglobulins that deposit in the glomeruli are the major triggers of glomeruli inflammation. In rare settings such as C3 GN, complement proteins are present in the glomerular lesions in the absence of immunoglobulins. Abnormal activation of the alternative pathway is implicated on this finding. Either an acquired or inherited defect in the control of alternative complement pathway should be investigated.

The following tests are generally recommended:

** Levels of C3 and complement factors B/H/I

** Presence of C3 nephritic factor (C3 NeF)

** Genotyping for certain complement mutations (common in kids)

Our patient underwent complement testing and was found to have circulating C3 nephritic factor. This factor is an IgG autoantibody that directly stabilizes the C3-convertase activating complex of the alternative pathway and thereby prevents the normal inhibitory action of complement factor H, leading to continuous activation of the complement cascade and consequent deposition of complement by-products in the glomeruli.

Although atypical hemolytic uremic syndrome (aHUS) is also strongly associated with a dysregulation of the alternative pathway, glomerular lesions in aHUS do not exhibit C3 deposits or electro-dense deposits on electron microscopy, differentiating from C3 glomerulopathies. How changes in complement regulation leads to very diverse presentations might be related to the underlying defect. Nonetheless, atypical HUS could be placed in one side of this spectrum of renal diseases associated with alternative complement dysregulation (figure below; adapted from Servais et al. 2007).

While the pathogenesis is complicated, even harder is the treatment challenge of C3 GN in our patient above. There are a couple of new promising approaches and markers that might help guide therapy. I will try to cover them on my next blog.

Handling anticoagulation peri-kidney biopsy

Kidney biopsy is considered the most invasive procedure nephrologists are involved. Though complication rates are small, bleeding requiring surgery has been reported to occur in 1 in 1,000 kidney biopsies. More commonly, patients may develop a decrease in hemoglobin by 1 point (~50% of cases) and/or gross hematuria (3-18%). The risk of bleeding complications become much higher in patients that require peri-biopsy anticoagulation.

A new evidence-based guideline was just published on Chest 2012, summarizing the best approach to anticoagulation in a number of different scenarios. Overall, the new recommendations are more conservative than before regarding anticoagulation peri-procedure.

To illustrate that, let’s use a theoretical patient on anticoagulation with coumadin (6mg daily) due to Factor of V Leiden mutation and prior history of thrombosis (more than 6mo ago).

In preparation for the procedure, the physician would recommend stopping coumadin 5 days prior to the kidney biopsy and bridging with either UFH or LMWH. This is usually started on day 3 prior to the procedure. The major difference in approach now is related to when should the bridging anticoagulation be stopped and restarted. The novel guidelines recommend the following:

* If on IV heparin, stop infusion 4-6 hours prior to procedure

* If on LMW, last dose should be 24 hours prior to procedure (rather than 12 hours before)

* Resuming coumadin should occur 12-24 hours after procedure if no evidence of bleeding

* Bridging anticoagulation with LMWH or UFH should be restarted 48-72 hours after the procedure (rather than 24 hours after surgery). Since most of the bleeding after kidney biopsy will occur in the first 24 hours, I believe delaying for another 24 hours would only be warrant in major surgeries with higher bleeding risks)

Most of these recommendations are grade 2C (weak), therefore individual interpretation is warranted.

My take-home summary of anticoagulation peri-kidney biopsy in high risk patients for thromboembolism would be:

Stop coumadin 5 days before procedure; admit the patient with renal failure 3 days prior to biopsy for bridging with UFH; stop UFH at least 4 hours prior to procedure; resume coumadin/UFH 6-24 hours after bx if no evidence of bleeding (stable Hb, vital signs and no significant hematuria).

Though this is a general suggested approach, remember to assess the thromboembolic risk for each individual patient before proceeding with a kidney biopsy. As an example, I would favor restarting anticoagulation much earlier after bx in a patient with history of multiple clots (6 hours after biopsy).

Below additional general recommendations about anticoagulants from the new guidelines:

- Dosing of UFH: 80U/kg bolus followed by 18U/kg/hour

- Dosing of coumadin: loading with 10mg daily for first 2 days [[personal opinion: this loading dose may be too high for elderly or cachetic patients]]

- Dosing of enoxaparin: 1mg/kg BID; if GFRb below 30 ml/min: 1mg/kg daily

- Dosing of fondaperinox: 5mg daily if less than 50kg; 7.5mg if 50-100kg and 10mg if more than 100kg. Avoid if GFR less than 30 ml/min.

- Dosing of dalterapin : 200 U/kg daily. Accumulation expected in renal failure but no specific dose adjustment has been recommended, so should likely be avoided until trials available.

- Despite recent publications about benefits of genotyping in predicting response to coumadin, the guidelines recommend against this practice.