De novo anti-HLA antibody after pandemic H1N1 and seasonal influenza immunization in kidney transplant recipients

Influenza vaccine strategies for solid organ transplant recipients

PURPOSE OF REVIEW

The aim of this study was to highlight recent evidence on important aspects of influenza vaccination in solid organ transplant recipients.

RECENT FINDINGS

Influenza vaccine is the most evaluated vaccine in transplant recipients. The immunogenicity of the vaccine is suboptimal after transplantation. Newer formulations such as inactivated unadjuvanted high-dose influenza vaccine and the administration of a booster dose within the same season have shown to increase response rates. Intradermal vaccination and adjuvanted vaccines did not show clear benefit over standard influenza vaccines. Recent studies in transplant recipients do not suggest a higher risk for allograft rejection, neither after vaccination with a standard influenza vaccine nor after the administration of nonstandard formulation (high-dose, adjuvanted vaccines), routes (intradermally) or a booster dose. Nevertheless, influenza vaccine coverage in transplant recipients is still unsatisfactory low, potentially due to misinterpretation of risks and benefits.

SUMMARY

Annual influenza vaccination is well tolerated and is an important part of long-term care of solid organ transplant recipients.

Effects of the influenza vaccine on pediatric kidney transplant outcomes

The influenza vaccine is critical for preventing influenza-related complications in transplant patients. Previous studies demonstrated de novo donor-specific antibody formation and rejection following the influenza vaccination. This risk has not been adequately assessed in the pediatric population. We performed a single-center retrospective analysis of 187 unique pediatric kidney transplant recipients, transplanted from January 1, 2006, to December 31, 2015, assessing for an association of the influenza vaccination with various transplant outcomes. The influenza vaccine was received by 125 of 187 patients within the first year post-transplant. Using log-rank tests and Kaplan-Meier curves, vaccinated patients had a significantly lower risk of mortality (P = 0.048). There were no differences in death-censored graft survival (P = 0.253), graft survival (P = 0.098), or rejection (P = 0.195) between vaccinated and unvaccinated groups. To address the problem of multiple exposures for a yearly vaccine, Cox proportional hazards regression was utilized with post-transplant vaccination status considered as a time-dependent covariate; analyses were performed using both a 360- and 180-day vaccination period following any post-transplant influenza vaccination. In this model, being vaccinated did not result in a significant difference in mortality (HR 0.90 [0.16, 5.15], P = 0.91), death-censored graft survival (HR 0.70 [0.31, 1.58], P = 0.39), graft survival (HR 0.69 [0.32, 1.49], P = 0.34), or rejection (HR 0.67 [0.37, 1.19], P = 0.17). Eight patients developed de novo donor-specific antibodies following the first post-transplant influenza vaccination; three then developed biopsy-proven rejection. These results suggest influenza vaccination is safe in pediatric kidney transplant recipients, and larger prospective studies are required to conclusively confirm our findings.

Case report: A transplant candidate with unexpected serum reactivity against the 45KE eplet on HLA-B alleles

This case report describes the serum antibody specificity against the 45KE eplet which had not been yet shown to be antibody-verified. This antibody was produced by a 41-year-old European male with Berger's disease. His serum had HLA class I antibody reactivity as determined in IgG binding assays with single allele panels (OneLambda, ThermoFisher, Lot 8 and Lot 9). The HLAMatchmaker analysis revealed reproducible serum reactivity only with alleles carrying the 45KE eplet. The cause of this 45KE-specific immunization is unknown because this male patient had never been transfused nor received a previous transplant, Moreover, his mother's HLA type did not have any 45KE-carrying allele. This finding might be related to observations reported in the literature about the appearance of HLA-reactive antibodies following influenza vaccination but this possibility could not be investigated.

Seasonal influenza vaccine in immunocompromised persons

Immunocompromised persons are at high risk of complications from influenza infection. This population includes those with solid organ transplants, hematopoietic stem cell transplants, solid cancers and hematologic malignancy as well as those with autoimmune conditions receiving biologic therapies. In this review, we discuss the impact of influenza infection and evidence for vaccine effectiveness and immunogenicity. Overall, lower respiratory disease from influenza is common; however, vaccine immunogenicity is low. Despite this, in some populations, influenza vaccine has demonstrated effectiveness in reducing severe disease. Various strategies to improve influenza vaccine immunogenicity have been attempted including two vaccine doses in the same influenza season, intradermal, adjuvanted, and high-dose vaccines. The timing of influenza vaccine is also important to achieve optimal immunogenicity. Given the suboptimal immunogenicity, family members and healthcare professionals involved in the care of these populations should be vaccinated. Health care professional recommendation for vaccination is an important factor in vaccine coverage.

Does vaccination in solid-organ transplant recipients result in adverse immunologic sequelae? A systematic review and meta-analysis

BACKGROUND

Clinical guidelines recommend vaccinations for solid-organ transplant recipients. However, concern exists that vaccination may stimulate adverse alloimmune responses.

METHODS

We systematically reviewed the published literature regarding this aspect of vaccine safety. Electronic databases were searched for interventional and observational studies assessing de novo donor-specific antibodies (DSA) and rejection episodes after vaccination against infectious pathogens. Graft loss was also assessed. A meta-analysis was conducted for prospective, controlled studies. PRISMA reporting guidelines were followed.

RESULTS

Ninety studies (15,645 vaccinated patients and 42,924 control patients) were included. Twelve studies included control groups. The incidence of de novo DSA (14 studies) was 23 of 1,244 patients (1.85%) at 21 to 94 days. The incidence of rejection (83 studies) was 107 episodes in 5,116 patients (2.1%) at 0.7 to 6 months. Meta-analysis of prospective controlled studies (n = 8) showed no increased rejection risk with vaccination compared with no vaccination (RR 1.12, 95% CI 0.75 to 1.70). This finding was supported by data from 3 registry analyses.

CONCLUSIONS

Although the current evidence lacks high-quality, controlled studies, the currently available data provide reassurance that clinicians should recommend appropriate vaccination for their transplant patients as the risk of de novo DSA and rejection is relatively low.

Adjuvanted (AS03) A/H1N1 2009 Pandemic Influenza Vaccines and Solid Organ Transplant Rejection: Systematic Signal Evaluation and Lessons Learnt

Introduction

We investigated a signal of solid organ transplant (SOT) rejection after immunisation with (AS03) A/H1N1 2009 pandemic influenza vaccines.

Methods

Potential immunological mechanisms were reviewed and quantitative analyses were conducted. The feasibility of pharmacoepidemiological studies was explored.

Results

Overall results, including data from a pharmacoepidemiological study, support the safety of adjuvanted (AS03) pandemic influenza vaccination in SOT recipients. The regulatory commitment to evaluate the signal through a stepwise investigation was closed in 2014.

Conclusion

Lessons learned highlight the importance of investigating plausible biological mechanisms between vaccines and potentially associated adverse outcomes, and the importance of selecting appropriate study settings and designs for safety signal investigations.

Electronic supplementary material

The online version of this article (doi:10.1007/s40264-017-0532-3) contains supplementary material, which is available to authorized users.

Two Doses of Inactivated Influenza Vaccine Improve Immune Response in Solid Organ Transplant Recipients: Results of TRANSGRIPE 1-2, a Randomized Controlled Clinical Trial

Background

Influenza vaccine effectiveness is not optimal in solid organ transplant recipients (SOTR). We hypothesized that a booster dose might increase it.

Methods

TRANSGRIPE 1-2 is a phase 3, randomized, controlled, multicenter, open-label clinical trial. Patients were randomly assigned (1:1 stratified by study site, type of organ, and time since transplantation) to receive 1 dose (control group) or 2 doses (booster group) of the influenza vaccine 5 weeks apart.

Results

A total of 499 SOTR were enrolled. Although seroconversion at 10 weeks did not meet significance in the modified intention-to-treat population, seroconversion rates were significantly higher in the booster arm for the per-protocol population (53.8% vs 37.6% for influenza A(H1N1)pdm; 48.1% vs 32.3% for influenza A(H3N2); and 90.7% vs 75% for influenza B; P < .05). Furthermore, seroprotection at 10 weeks was higher in the booster group: 54% vs 43.2% for A(H1N1)pdm; 56.9% vs 45.5% for A(H3N2); and 83.4% vs 71.8% for influenza B (P < .05). The number needed to treat to seroprotect 1 patient was <10. The clinical efficacy (99.2% vs 98.8%) and serious adverse events (6.4% vs 7.5%) were similar for both groups.

Conclusions

In SOTR, a booster strategy 5 weeks after standard influenza vaccination is safe and effective and induces an increased antibody response compared with standard influenza vaccination consisting of a single dose.

Clinical Trials Registration

EudraCT (2011-003243-21).

Infectious pathogens may trigger specific allo-HLA reactivity via multiple mechanisms

Transplant recipients can be sensitized against allo-HLA antigens by previous transplantation, blood transfusion, or pregnancy. While there is growing awareness that multiple components of the immune system can act as effectors of the alloresponse, the role of infectious pathogen exposure in triggering sensitization and allograft rejection has remained a matter of much debate. Here, we describe that exposure to pathogens may enhance the immune response to allogeneic HLA antigens via different pathways. The potential role of allo-HLA cross-reactivity of virus-specific memory T cells, activation of innate immunity leading to a more efficient induction of the adaptive alloimmune response by antigen-presenting cells, and bystander activation of existing memory B cell activation will be discussed in this review.

Decrease of blood anti-α1,3 Galactose Abs levels in multiple sclerosis (MS) and clinically isolated syndrome (CIS) patients

The etiology of multiple sclerosis (MS) remains elusive. Among the possible causes, the increase of anti-Neu5Gc antibodies during EBV primo-infection of Infectious mononucleosis (IMN) may damage the integrity of the blood-brain barrier facilitating the transfer of EBV-infected B cells and anti-EBV T cell clones in the brain. We investigated the change in titers of anti-Neu5Gc and anti-α1,3 Galactose antibodies in 49 IMN, in 76 MS, and 73 clinically isolated syndrome (CIS) patients, as well as age/gender-matched healthy individuals. Anti-Gal and anti-Neu5Gc are significantly increased during IMN (p=0.02 and p<1.10^-4 respectively), but not in acute CMV primo-infection. We show that, whereas there was no change in anti-Neu5Gc in MS/CIS, the two populations exhibit a significant decrease in anti-Gal (combined p=2.7.10^-3), in contrast with patients with non-MS/CIS central nervous system pathologies. Since anti-Gal result from an immunization against α1,3 Gal, lacking in humans but produced in the gut, our data suggest that CIS and MS patients have an altered microbiota or an altered response to this microbiotic epitope.

Clinical Characteristics and Outcomes of Influenza A Infection in Kidney Transplant Recipients: A Single-Center Experience

BACKGROUND

Influenza virus infection can cause severe illness in certain high-risk groups. Solid organ and hematopoietic stem cell transplant recipients have been shown to present a greater risk for severe influenza and complications than the general population.

METHODS

Retrospective descriptive cohort study of the features and outcomes of influenza infection in renal transplant recipients from July 2009 to May 2014.

RESULTS

Thirty-one patients were diagnosed with influenza A infection within the specified period. The incidence of influenza A was 26.5 cases/1,000 person-years. Hospital admission (68%), secondary bacterial pneumonia (68%), intensive care unit admission (14%), and mortality rate (14%) were higher than reported for immunocompetent patients.

CONCLUSIONS

Influenza diagnosis and treatment should be prompt in immunocompromised patients to reduce the risk of complications. Patients who require intensive care owing to respiratory and hemodynamic complications present high mortality rates.

Heterologous Immune Responses to Influenza Vaccine in Kidney Transplant Recipients

Influenza vaccine is known to have suboptimal immunogenicity in transplant recipients. Despite this, influenza vaccine may have the added benefit of inducing a cross-reactive immune response to viral strains not found in the vaccine. This is termed "heterologous immunity" and has not been assessed previously in transplant patients. Pre- and postvaccination sera from kidney transplant recipients (n = 60) immunized with the 2012-2013 adjuvanted or nonadjuvanted influenza vaccine underwent testing by hemagglutination inhibition assay for strains not present in vaccine: A/New Caledonia/20/99 (H1N1), A/Texas/50/2012 (H3N2) and B/Brisbane/60/2008. The geometric mean titer of antibody to heterologous strains increased after vaccine (H1N1: 80.0 to 136.1, p < 0.001; H3N2: 23.3 to 77.3, p < 0.001; B: 13.3 to 19.5, p < 0.001). Seroconversion rates were 16.7%, 41.7%, and 13.3%, respectively. No differences in heterologous response were seen in the adjuvanted versus nonadjuvanted groups. Patients were more likely to seroconvert for a cross-reactive antigen if they seroconverted for the specific vaccine antigen. Seroconversion to heterologous A/H3N2, for example, was 84.0% for homologous H3N2 seroconverters versus 11.4% for nonseroconverters (p < 0.001). This study provides novel evidence that transplant recipients are able to mount significant cross-protective responses to influenza vaccine that may be an additional, previously unknown benefit of immunization.

The risks of using allogeneic cell lines for vaccine production: the example of Bovine Neonatal Pancytopenia

INTRODUCTION

Bovine neonatal pancytopenia (BNP) is a hemorrhagic disease that emerged in calves across Europe in 2007. Its occurrence is attributed to immunization of the calf's mother with a vaccine produced using an allogeneic cell line. Vaccine-induced alloantibodies specific for major-histocompatibility class I antigens are transferred from the mother to the calf via colostrum, leading to profound depletion of peripheral blood and bone marrow cells that is often fatal. Areas covered: Pubmed and Web of Science were used to search for literature relevant to BNP and the use of allogeneic vaccine cell lines. Following a review of the pathology and pathogenesis of this novel condition, we discuss potential risks associated with the use of allogeneic vaccine cell lines. Expert commentary: Although BNP is associated with a specific vaccine, it highlights safety concerns common to all vaccines produced using allogeneic cell lines. Measures to prevent similar vaccine-induced alloimmune-mediated adverse events in the future are discussed.

Immunizations in solid organ and hematopoeitic stem cell transplant patients: A comprehensive review

The Solid Organ Transplantation (SOT) and Haematopoietic Stem Cell Transplantation (HSCT) population is continuously increasing as a result of broader indications for transplant and improved survival. Infectious diseases, including vaccine-preventable diseases, are a significant threat for this population, primarily after but also prior to transplantation. As a consequence, clinicians must ensure that patients are optimally immunized before transplantation, to provide the best protection during the early post-transplantation period, when immunosuppression is the strongest and vaccine responses are poor. After 3-6 months, inactivated vaccines immunization can be resumed. By contrast, live-attenuated vaccines are lifelong contraindicated in SOT patients, but can be considered in HSCT patients at least 2 years after transplantation, if there is no immunosuppression or graft-versus-host-disease. However, because of the advantages of live-attenuated over inactivated vaccines--and also sometimes the absence of an inactivated alternative--an increasing number of prospective studies on live vaccine immunization after transplantation are performed and give new insights about safety and immunogenicity in this population.

Randomized Controlled Trial of Adjuvanted Versus Nonadjuvanted Influenza Vaccine in Kidney Transplant Recipients

BACKGROUND

Influenza vaccine containing an oil-in-water emulsion adjuvant (MF-59) may lead to greater immunogenicity in organ transplant recipients. However, alloimmunization may be a concern with adjuvanted vaccines.

METHODS

We conducted a randomized trial comparing the safety and immunogenicity of adjuvanted versus nonadjuvanted influenza vaccine in adult kidney transplant patients. Patients were randomized 1:1 to receive 2012 to 2013 influenza vaccine with or without MF59 adjuvant. Preimmunization and postimmunization sera underwent strain-specific hemagglutination inhibition assay. HLA alloantibody was determined by Luminex single-antigen bead assay.

RESULTS

We randomized 68 patients and 60 (29 nonadjuvanted; 31 adjuvanted) had complete samples available at follow-up. Seroconversion to at least 1 of 3 influenza antigens was present in 71.0% versus 55.2% in adjuvanted versus nonadjuvanted vaccine respectively (P = 0.21). Geometric mean titers and seroprotection rates were similar between groups. Seroconversion rates were especially low in those on MMF of 2 g or greater daily (44.4% vs 71.4%; P = 0.047). In the subgroup of patients 18 to 64 years old, seroconversion was significantly greater with adjuvanted vaccine (odds ratio, 6.10; 95% confidence interval, 1.25-28.6). There were no increases in HLA alloantibodies in patients who received adjuvanted vaccine.

CONCLUSIONS

Adjuvanted vaccine was safe and had similar immunogenicity to standard vaccine in the overall transplant cohort but did show a potential immunogenicity benefit for the 18 to 64 years age group.

Immune mechanisms of acute and chronic rejection

With the currently available immunosuppression, severe T-cell mediated rejection has become a rare event. With the introduction of modern antibody-detection techniques, such as the L-SAB technology, acute or hyperacute antibody-mediated rejection of the kidney are also seen infrequently. In contrast, chronic antibody-mediated rejection is considered to be a major contributor to graft loss in the late posttransplant phase. Problems in the management of chronic antibody-mediated rejection are effective prevention of the development of alloantibodies against donor HLA and the early identification of patients at risk for this entity. Finally, today there is still noeffective strategy to treat this indolent and slowly progressing form of antibody-mediated rejection. Herein, we review the pathomechanisms of the different forms of rejection and the clinical significance of these entities in human kidney transplantation.

Effect of the adjuvanted (AS03) A/H1N1 2009 pandemic influenza vaccine on the risk of rejection in solid organ transplant recipients in England: a self-controlled case series

OBJECTIVE

To assess the risk of solid organ transplant (SOT) rejection after vaccination with the adjuvanted (AS03) A/H1N1 2009 pandemic influenza vaccine Pandemrix.

DESIGN

Self-controlled case series (SCCS) in the UK Clinical Practice Research Datalink (CPRD) and its linked component of the Hospital Episodes Statistics (HES) inpatient database. Analyses were conducted using the SCCS method for censored, perturbed or curtailed post-event exposure.

PARTICIPANTS

Of the 184 transplant recipients having experienced at least one SOT rejection (liver, kidney, lung, heart or pancreas) during the study period from 1 October 2009 to 31 October 2010, 91 participants were included in the main analysis, of which 71 had been exposed to Pandemrix.

MAIN OUTCOME MEASURES

Occurrence of SOT rejection during risk (30 and 60 days after any Pandemrix dose) and control periods. Covariates in the CPRD included time since transplantation, seasonal influenza vaccination, bacterial and viral infections, previous SOT rejections and malignancies.

RESULTS

The relative incidence (RI) of rejection of any one of the five transplanted organs, adjusted for time since transplantation, was 1.05 (95% CI 0.52 to 2.14) and 0.80 (95% CI 0.42 to 1.50) within 30 and 60 days after vaccination, respectively. Similar estimates were observed for rejection of a kidney only, the most commonly transplanted organ (RI within 30 days after vaccination: 0.85 (95% CI 0.38 to 1.90)). Across various models and sensitivity analyses, RI estimates remained stable and within a consistent range around 1.0.

CONCLUSIONS

These results suggest a reassuring safety profile for Pandemrix with regard to the risk of rejection in SOT recipients in England and contribute to inform the benefit-risk of AS03-adjuvanted pandemic influenza vaccines in transplanted patients in the event of future pandemics.

TRIAL REGISTRATION NUMBER

NCT01715792.

Pediatric deceased donor renal transplantation: An approach to decision making II. Acceptability of a deceased donor kidney for a child, a snap decision at 3 AM

Allocation of deceased donor kidneys is based on several criteria; however, the final decision to accept or reject the offered kidney is made by the potential recipient's transplant team (surgeon/nephrologist). Several considerations including assessment of the donor quality, the HLA match between the donor and the recipient, several recipient factors, the geographical location of the recipient, and the organ all affect the decision of whether or not to finally accept the organ for a particular recipient. This decision needs to be made quickly, often on the spot. Maximizing the benefit from this scarce resource raises difficult ethical issues. The philosophies of equity and utility are often competing. This article will discuss the several considerations for the pediatric nephrologist while accepting a deceased donor kidney for a particular pediatric patient.

Immunizations following solid-organ transplantation

PURPOSE OF REVIEW

To highlight the latest evidence for the use of key vaccines that are recommended in organ transplant candidates and recipients.

RECENT FINDINGS

Influenza vaccine is the best studied vaccine; factors affecting immunogenicity of this vaccine include time from transplant, use of mycophenolate mofetil and type of transplant. Newer formulations of influenza vaccine are available, but data for these are limited. Updated recommendations include giving conjugated pneumococcal vaccine to adult transplant candidates and recipients followed by the polysaccharide vaccine to increase serotype coverage. Human papillomavirus vaccine should also be given to transplant recipients, although the immunogenicity may be suboptimal. Quadrivalent meningococcal conjugate vaccine needs to be given in special circumstances such as to patients who are starting eculizumab therapy. Live vaccines in general are contraindicated, although increasing safety data are emerging for Varicella vaccine. Herpes Zoster vaccine may be offered prior to transplant, although the utility of this strategy regarding protection from shingles after transplant is not known. Newer vaccines such as inactivated zoster vaccine and vaccines for the prevention of cytomegalovirus are under study.

SUMMARY

Immunization for organ transplant recipients is an important part of pretransplant evaluation and the long-term care of the transplant recipient.

Whether or not to accept a deceased donor kidney offer for a pediatric patient

The expansion of the number of children on the deceased donor renal transplant waitlist has far outstripped the supply of organs in most countries, leading to numerous adjustments to increase supply and to maximize the utility of donor organs. The system for organ allocation varies by country based on local laws, priorities, and resources. Adjustments are made to optimize allocation, enhance post-transplant survival benefit, decrease unequal transplant access, and optimize utilization of donated kidneys. Allocation of deceased donor kidneys is based on several criteria; however, the final decision to accept or reject the offered kidney is made by the potential recipient's transplant team (surgeon/nephrologist). Several considerations including assessment of the donor quality, the human leukocyte antigen (HLA) match between the donor and the recipient, numerous recipient factors, the geographical location of the recipient, and the organ all affect the decision to accept the organ or not for a particular recipient. This decision must be made quickly, often on the spot. Maximizing the benefit from this scarce resource raises difficult ethical issues. The philosophies of equity and utility are often competing. In this manuscript, we highlight a representative case that helps to focus on important issues for the pediatric nephrologist to consider while making the decision to accept a deceased donor kidney offer for a particular pediatric patient.

Detecting the humoral alloimmune response: we need more than serum antibody screening

Whereas many techniques exist to detect HLA antibodies in the sera of immunized individuals, assays to detect and quantify HLA-specific B cells are only just emerging. The need for such assays is becoming clear, as in some patients, HLA-specific memory B cells have been shown to be present in the absence of the accompanying serum HLA antibodies. Because HLA-specific B cells in the peripheral blood of immunized individuals are present at only a very low frequency, assays with high sensitivity are required. In this review, we discuss the currently available methods to detect and/or quantify HLA-specific B cells, as well as their promises and limitations. We also discuss scenarios in which quantification of HLA-specific B cells may be of additional value, besides classical serum HLA antibody detection.

Influenza virus vaccination and kidney graft rejection: causality or coincidence

Influenza can cause significant morbidity and mortality in renal transplant recipients especially with a high rate of lower respiratory disease. Annual influenza vaccination is therefore recommended to renal transplant recipients. We report the first three cases of acute kidney injury in renal transplant recipients following influenza vaccination that all led to graft loss. They all had different native diseases and were all vaccinated in the same season of 2009-10. The time span from vaccination to decline of kidney function is shorter than the time to diagnosis since the three patients only had blood tests every 3 months or when symptoms became severe. These reports do not justify a change of current recommendations regarding influenza vaccination in renal transplant recipients, but they support the continued attention and registration of vaccinations to monitor side effects.

Red blood cell transfusions are associated with HLA class I but not H-Y alloantibodies in children with sickle cell disease

Blood transfusions can induce alloantibodies to antigens on red blood cells (RBCs), white blood cells and platelets, with these alloantibodies affecting transfusion and transplantation. While transfusion-related alloimmunization against RBC antigens and human leucocyte antigens (HLA) have been studied, transfusion-related alloimmunization to minor histocompatibility antigens (mHA), such as H-Y antigens, has not been clinically characterized. We conducted a cross-sectional study of 114 children with sickle cell disease (SCD) and tested for antibodies to 5 H-Y antigens and to HLA class I and class II. Few patients had H-Y antibodies, with no significant differences in the prevalence of any H-Y antibody observed among transfused females (7%), transfused males (6%) and never transfused females (4%). In contrast, HLA class I, but not HLA class II, antibodies were more prevalent among transfused than never transfused patients (class I: 33% vs. 13%, P = 0·046; class II: 7% vs. 8%, P = 0·67). Among transfused patients, RBC alloantibody history but not amount of transfusion exposure was associated with a high (>25%) HLA class I panel reactive antibody (Odds ratio 6·8, 95% confidence interval 2·1-22·3). These results are consistent with immunological responder and non-responder phenotypes, wherein a subset of patients with SCD may be at higher risk for transfusion-related alloimmunization.

HLA sensitisation: can it be prevented?

Human leukocyte antigen (HLA) sensitisation occurs after transfusion of blood products and transplantation. It can also happen spontaneously through cross-sensitisation from infection and pro-inflammatory events. Patients who are highly sensitised face longer waiting times on organ allocation programmes, more graft rejection and therefore more side effects of immunosuppression, and poorer graft outcomes. In this review, we discuss these issues, along with the limitations of modern HLA detection methods, and potential ways of decreasing HLA antibody development. We do not discuss the removal of antibodies after they have developed.

Utility of HLA Antibody Testing in Kidney Transplantation

HLA antigens are polymorphic proteins expressed on donor kidney allograft endothelium and are critical targets for recipient immune recognition. HLA antibodies are risk factors for acute and chronic rejection and allograft loss. Solid-phase immunoassays for HLA antibody detection represent a major advance in sensitivity and specificity over cell-based methods and are widely used in organ allocation and pretransplant risk assessment. Post-transplant, development of de novo donor-specific HLA antibodies and/or increase in donor-specific antibodies from pretransplant levels are associated with adverse outcomes. Although single antigen bead assays have allowed sensitive detection of recipient HLA antibodies and their specificities, a number of interpretive considerations must be appreciated to understand test results in clinical and research contexts. This review, which is especially relevant for clinicians caring for transplant patients, discusses the technical aspects of single antigen bead assays, emphasizes their quantitative limitations, and explores the utility of HLA antibody testing in identifying and managing important pre- and post-transplant clinical outcomes.

Clinical relevance of HLA antibody monitoring after kidney transplantation

In kidney transplantation, antibody-mediated allograft injury caused by donor HLA-specific antibodies (DSA) has recently been identified as one of the major causes of late graft loss. This paper gives a brief overview on the impact of DSA development on graft outcome in organ transplantation with a focus on risk factors for de novo alloantibody induction and recently published guidelines for monitoring of DSA during the posttransplant phase.

Washing red cells after leucodepletion does not decrease human leukocyte antigen sensitization risk in patients with chronic kidney disease

BACKGROUND

Standard leucodepleted blood transfusions can induce the production of human leukocyte antigen (HLA)-specific antibodies, which are associated with longer transplant waiting times and poorer graft outcomes. We hypothesized that additional washing of leucodepleted red cells might reduce antigenic stimulus by removal of residual leukocytes and soluble HLA.

METHODS

A retrospective review of HLA antibodies in children with chronic kidney disease stage 4-5 who had ≥ two HLA antibody screens between 2000 and 2009, pre- and post-transfusion, and were HLA antibody-negative at first testing. Patients were divided according to whether they received standard leucodepleted blood or "washed cells". To assess the efficacy of washing methods, total leukocytes were enumerated pre- and post- manual and automated washing of standard leucodepleted red cells that had been supplemented with whole blood to achieve measurable leukocyte levels pre-washing.

RESULTS

A total of 106 children were included: 23 received no blood transfusions (group 1), six had washed cells only (group 2), 59 had standard transfusions only (group 3), and 18 had both standard and washed cells (group 4). Sensitization rates were 26, 17, 44, and 44 % in groups 1-4 (p = 0.32). Patients in groups 3 and 4 had more transfusions with red cells, platelets, and plasma products. There was no difference in HLA sensitization risk with washed or standard red cells on analysis of co-variance controlling for platelets and plasma transfusions. The red cell washing study showed no significant reduction in leukocytes using manual methods. Although there was a statistically significant reduction (33 %) from baseline pre-washing using the automated method, from 6.54 ± 0.84 × 10(6) to 4.36 ± 0.67 × 10(6) leukocytes per unit, the majority of leukocytes still remained.

CONCLUSIONS

There was no evidence that using washed leucodepleted red cells reduced patient HLA sensitization rates. Washing leucodepleted red cells is unlikely to reduce the risk of HLA sensitization due to the limited effect on residual leukocytes.

Immunization after kidney transplantation-what is necessary and what is safe?

Many transplant recipients are not protected against vaccine-preventable illnesses, primarily because vaccination is still an underutilized tool both before and after transplantation. This missed opportunity for protection can result in substantial morbidity, graft loss and mortality. Immunization strategies should be formulated early in the course of renal disease to maximize the likelihood of vaccine-induced immunity, particularly as booster or secondary antibody responses are less affected by immune compromise than are primary or de novo antibody responses in naive vaccine recipients. However, live vaccines should be avoided in immunocompromised hosts. Although some concern has been raised regarding increased HLA sensitization after vaccination, no clinical data to suggest harm currently exists; overall, non-live vaccines seem to be immunogenic, protective and safe. In organ transplant recipients, some vaccines are indicated based on specific risk factors and certain vaccines, such as hepatitis B, can protect against donor-derived infection. Vaccines given to close contacts of renal transplant recipients can provide an additional layer of protection against infectious diseases. In this article, optimal vaccination of adult transplant recipients, including safety, efficacy, indication and timing, is reviewed.

Changing face of vaccination in immunocompromised hosts

Infection prevention is a key component of care and an important determinant of clinical outcomes in a diverse population of immunocompromised hosts. Vaccination remains a fundamental preventative strategy, and clear guidelines exist for the vaccination of immunocompromised individuals and close contacts. Unfortunately, adherence to such guidelines is frequently suboptimal, with consequent missed opportunities to prevent infection. Additionally, vaccination of immunocompromised individuals is known to produce responses inferior to those observed in immunocompetent hosts. Multiple factors contribute to this finding, and developing improved vaccination strategies for those at high risk of infectious complications remains a priority of care providers. Herein, we review potential factors contributing to vaccine outcomes, focusing on host immune responses, and propose a means for applying modern, innovative systems biology technology to model critical determinants of vaccination success. With influenza vaccine in solid organ transplants used as a case in point, novel means for stratifying individuals using a host "immunophenotype" are explored, and strategies for individualizing vaccine approaches tailored to safely optimize vaccine responses in those most at risk are discussed.

Impact of immunosuppression on recall immune responses to influenza vaccination in stable renal transplant recipients

BACKGROUND

The recommendation by the American Society of Transplantation for annual trivalent inactivated influenza vaccination greater than 3 to 6 months post-kidney transplantation provides a unique opportunity to test the in vivo impact of immunosuppression on recall T- and B-cell responses to influenza vaccination.

METHODS

This study took advantage of recent breakthroughs in the single-cell quantification of human peripheral blood B-cell responses to prospectively evaluate both B- and T-cell responses to the seasonal (2010 and 2011) influenza vaccine in 23 stable renal transplant recipients and 22 healthy controls.

RESULTS AND CONCLUSION

The results demonstrate that the early B-cell response to influenza vaccination, quantified by the frequency of influenza-specific antibody-secreting cells (ASC) in peripheral blood, was significantly reduced in stable transplant recipients compared to healthy controls. The magnitude of the seroresponse and the rate of seroconversion were also blunted. The influenza-specific interferon-gamma (IFNγ) T-cell response was significantly reduced in transplant recipients; however, there was no correlation between the magnitude of the influenza-specific IgG ASC and IFNγ responses. The induction of memory T- and B-cell responses to influenza vaccination supports the recommendation to vaccinate while the blunted responses demonstrate the efficacy of immunosuppression in controlling memory responses individual transplant recipients.

Influenza vaccination and humoral alloimmunity in solid organ transplant recipients

Annual influenza vaccination is recommended in solid organ transplant (SOT) recipients. However, concerns have been raised about the impact of vaccination on antigraft alloimmunity. We evaluated the humoral alloimmune responses to influenza vaccination in a cohort of SOT recipients between October 2008 and December 2011. Anti-HLA antibodies were measured before and 4-8 weeks after influenza vaccination using a solid-phase assay. Overall, 169 SOT recipients were included (kidney = 136, lung = 26, liver = 3, and combined = 4). Five (2.9%) of 169 patients developed de novo anti-HLA antibodies after vaccination, including one patient who developed donor-specific antibodies (DSA) 8 months after vaccination. In patients with pre-existing anti-HLA antibodies, median MFI was not significantly different before and after vaccination (P = 0.73 for class I and P = 0.20 for class II anti-HLA antibodies) and no development of de novo DSA was observed. Five episodes of rejection (2.9%) were observed within 12 months after vaccination, and only one patient had de novo anti-HLA antibodies. The incidence of development of anti-HLA antibodies after influenza vaccination in our cohort of SOT recipients was very low. Our findings indicate that influenza vaccination is safe and does not trigger humoral alloimmune responses in SOT recipients.

Immunogenicity of a prophylactic quadrivalent human papillomavirus L1 virus-like particle vaccine in male and female adolescent transplant recipients

Organ TX recipients are at an increased risk of developing cancers of the lower genital tract related to HPV. The quadrivalent HPV vaccine has high efficacy in preventing these diseases, but response to many vaccines is suboptimal after organ transplantation. Liver and kidney TX recipients received quadrivalent HPV vaccine. Serum samples were tested for anti-HPV levels. Of 20 renal transplant recipients screened, 14 received vaccine. Of these, seven completed the vaccine series and seven had incomplete vaccination. Of five liver TX children, three received vaccines (two complete and one incomplete). All eight kidney and liver TX children with complete vaccination and available results were seronegative at baseline and had seroconversion at month 7 for all four HPV types. Six of 14 (42.8%) kidney TX recipients developed AR. During the same time period, eight of 28 (28.5%) non-vaccine renal transplant recipients developed AR (p = ns). Transplant adolescents developed 100% seroconversion to all four HPV serotypes with HPV vaccine with serologic titers similar to historic controls. A non-significant increased incidence of AR was noted among kidney transplant vaccine recipients. A much larger study would be needed to evaluate whether HPV vaccination increases AR in transplant adolescents.

Influenza vaccination in immunocompromised patients: efficacy and safety

Yearly administration of the influenza vaccine is the main strategy to prevent influenza in immunocompromised patients. Here, we reviewed the recent literature regarding the clinical significance of the influenza virus infection, as well as the immunogenicity and safety of the influenza vaccine in HIV‑infected individuals, solid-organ and stem-cell transplant recipients and patients receiving biological agents. Epidemiological data produced during the 2009 influenza pandemic have confirmed that immunocompromised patients remain at high risk of influenza-associated complications, namely viral and bacterial pneumonia, hospitalization and even death. The immunogenicity of the influenza vaccine is overall reduced in immunocompromised patients, although a significant clinical protection from influenza is expected to be obtained with vaccination. Influenza vaccination is safe in immunocompromised patients. The efficacy of novel strategies to improve the immunogenicity to the vaccine, such as the use of adjuvanted vaccines, boosting doses and intradermal vaccination, needs to be validated in appropriately powered clinical trials.

Pneumococcal immunization in immunocompromised hosts: where do we stand?

Immunocompromised patients are all at risk of invasive pneumococcal disease, of different degrees and timings. However, considerable progress in pneumococcal immunization over the last 30 years should benefit these patients. The 23-valent polysaccharide vaccine has been widely evaluated in these populations, but due to its low immunogenicity, its efficacy is sub-optimal, or even low. The principle of the conjugate vaccine is that, through the protein conjugation with the polysaccharide, the vaccine becomes more immunogenic, T-cell dependent, and thus providing a better early response and a boost effect. The 7-valent conjugate vaccine has been the first one to be evaluated in different immunocompromised populations. We review here the efficacy and safety of the different antipneumococcal vaccines in cancer, transplant and HIV-positive patients and propose a critical appraisal of the current guidelines.