Innate and adaptive immune responses to SARS-CoV-2 in humans: relevance to acquired immunity and vaccine responses.

The factors responsible for the spectrum of coronavirus 19 (COVID-19) disease severity and the genesis and nature of protective immunity against COVID-19 remain elusive. Multiple studies have investigated the immune responses to COVID-19 in various populations, including those without evidence of COVID-19 infection. Information regarding innate and adaptive immune responses to the novel severe respiratory syndrome coronavirus 2 (SARS-CoV-2) has evolved rapidly. Data are accumulating defining disease phenotypes that aid in rational and informed development of new therapeutic approaches for the treatment of patients infected with SARS-CoV-2 and the development of novel vaccines. In this paper, data on important innate immune responses are summarized, including cytokines, specifically interleukin (IL)-6 and complement, and potential treatments are explored. Adaptive immune responses and derivative therapeutics such as monoclonal antibodies directed at spike proteins are also examined. Finally, data on real-time assessments of adaptive immune responses are explored, which include CD4+ /CD8+ T cells, natural killer (NK) T cells, memory B cells and T follicular cells with specificities for COVID-19 peptides in infected and normal individuals. Data of two novel vaccines have been released, both showing > 95% efficacy in preventing SARS-CoV-2 infection. Analysis of humoral and cellular responses to the vaccines will determine the robustness and durability of protection. In addition, long-term assessment of SARS-CoV-2 memory B and T cell-mediated immune responses in patients recovering from an infection or those with cross-reactive immunological memory will help to define risk for future SARS-CoV infections. Finally, patients recovering from SARS-CoV-2 infection may experience prolonged immune activation probably due to T cell exhaustion. This will be an important new frontier for study.

Assessment of Tocilizumab (Anti-Interleukin-6 Receptor Monoclonal) as a Potential Treatment for Chronic Antibody-Mediated Rejection and Transplant Glomerulopathy in HLA-Sensitized Renal Allograft Recipients.

Extending the functional integrity of renal allografts is the primary goal of transplant medicine. The development of donor-specific antibodies (DSAs) posttransplantation leads to chronic active antibody-mediated rejection (cAMR) and transplant glomerulopathy (TG), resulting in the majority of graft losses that occur in the United States. This reduces the quality and length of life for patients and increases cost. There are no approved treatments for cAMR. Evidence suggests the proinflammatory cytokine interleukin 6 (IL-6) may play an important role in DSA generation and cAMR. We identified 36 renal transplant patients with cAMR plus DSAs and TG who failed standard of care treatment with IVIg plus rituximab with or without plasma exchange. Patients were offered rescue therapy with the anti-IL-6 receptor monoclonal tocilizumab with monthly infusions and monitored for DSAs and long-term outcomes. Tocilizumab-treated patients demonstrated graft survival and patient survival rates of 80% and 91% at 6 years, respectively. Significant reductions in DSAs and stabilization of renal function were seen at 2 years. No significant adverse events or severe adverse events were seen. Tocilizumab provides good long-term outcomes for patients with cAMR and TG, especially compared with historical published treatments. Inhibition of the IL-6-IL-6 receptor pathway may represent a novel approach to stabilize allograft function and extend patient lives.

The Incremental Cost of Incompatible Living Donor Kidney Transplantation: A National Cohort Analysis.

Incompatible living donor kidney transplantation (ILDKT) has been established as an effective option for end-stage renal disease patients with willing but HLA-incompatible living donors, reducing mortality and improving quality of life. Depending on antibody titer, ILDKT can require highly resource-intensive procedures, including intravenous immunoglobulin, plasma exchange, and/or cell-depleting antibody treatment, as well as protocol biopsies and donor-specific antibody testing. This study sought to compare the cost and Medicare reimbursement, exclusive of organ acquisition payment, for ILDKT (n = 926) with varying antibody titers to matched compatible transplants (n = 2762) performed between 2002 and 2011. Data were assembled from a national cohort study of ILDKT and a unique data set linking hospital cost accounting data and Medicare claims. ILDKT was more expensive than matched compatible transplantation, ranging from 20% higher adjusted costs for positive on Luminex assay but negative flow cytometric crossmatch, 26% higher for positive flow cytometric crossmatch but negative cytotoxic crossmatch, and 39% higher for positive cytotoxic crossmatch (p < 0.0001 for all). ILDKT was associated with longer median length of stay (12.9 vs. 7.8 days), higher Medicare payments ($91 330 vs. $63 782 p < 0.0001), and greater outlier payments. In conclusion, ILDKT increases the cost of and payments for kidney transplantation.

Liver Transplantation in a Patient With CD40 Ligand Deficiency and Hyper-IgM Syndrome: Clinical and Immunological Assessments.

Monoclonal antibodies that disrupt CD40-CD40 ligand (CD40L) interactions are likely to have use in human transplantation. However, the extent of the immunosuppressive effects of CD40-CD40L blockade in humans is unknown. Hyper-IgM syndrome (HIGM) is a rare primary immunodeficiency syndrome characterized by defects in the CD40-CD40L pathway, severe immune deficiency (IgG), and high or normal IgM levels. However, the effects of CD40L deficiency on T- and natural killer (NK)-cell function is not established. Here, we present a patient with HIGM syndrome who underwent liver transplantation for hepatitis C virus infection. Posttransplantation, NK-cell antibody-dependent cytokine release (γ-interferon) to alloantigens and T cell responses to viral antigens and mitogens were assessed and showed normal CD4+ , CD8+ , and NK-cell responses. We also examined antibody-dependent cellular cytotoxicity against a CD40+ and HLA-expressing cell line. These experiments confirmed that the patient's NK cells were equivalent to those of normal subjects in mediating antibody-dependent cellular cytotoxicity despite the absence of CD40-CD40L interactions. Mitogenic stimulation of the patient's peripheral blood mononuclear cells showed no expression of CD40L on T and NK cells compared with increased expression in normal subjects. Taken together, these data suggest that absence of CD40L expression is responsible for aberrant B cell immunity but had little impact on NK- and T cell immune responses in vitro.

Genetic Interactions Between TRPC6 and NPHS1 Variants Affect Posttransplant Risk of Recurrent Focal Segmental Glomerulosclerosis.

Individuals with TRPC6 mutations have variable phenotypes, ranging from healthy carrier to focal segmental glomerulosclerosis (FSGS) leading to renal failure. Here, we describe a family where six members had a novel TRPC6 p.R68W (c.202C>T) mutation, two of whom had renal failure from FSGS, and one had proteinuria. One healthy carrier donated a kidney to her sister. Both donor and recipient had no proteinuria at 20 years posttransplant. Two synonymous NPHS1 polymorphisms, rs2285450 (c.294C>T) and rs437168 (c.2289C>T) segregated with renal failure in this family. These variants had higher allele frequencies in 97 unrelated patients with nephrotic syndrome or FSGS compared to 224 controls. Using patch-clamp experiments in HEK293 and podocytes, we showed that the p.R68W mutation increased TRPC6 current amplitudes, which may be explained by enhanced TRPC6 surface expression. Additionally, while wild-type nephrin suppressed TRPC6 currents, this ability was lost in the presence of NPHS1 c.294C>T polymorphism. When cells were transfected according to combined TRPC6 and NPHS1 genotypes in the family, those representing the donor had lower TRPC6 currents than cells representing the recipient, suggesting that interactions between TRPC6 and NPHS1 variants could possibly account for the variable penetrance of TRPC6 mutations and the absence of recurrence in the graft.

JC polyomavirus viremia and progressive multifocal leukoencephalopathy in human leukocyte antigen-sensitized kidney transplant recipients desensitized with intravenous immunoglobulin and rituximab.

BACKGROUND: Desensitization (DES) with intravenous immunoglobulin (IVIG) + rituximab is effective, safe, and increases the transplantation rate in human leukocyte antigen-sensitized patients. However, reports of progressive multifocal leukoencephalopathy (PML) caused by JC polyomavirus (JCPyV) in autoimmune patients treated with rituximab is concerning. Here, we report on the JCPyV viremia and PML status in kidney transplant patients with/without DES (non-DES). METHODS: In total 1195 and 699 DNA samples from plasma in 117 DES (78% lymphocyte-depleting [LyD] induction) and 100 non-DES patients (45% LyD), respectively, were submitted for JCPyV-polymerase chain reaction. Results were compared in both groups. RESULTS: No patients in either DES or non-DES developed PML or presented with any neurological symptoms. The JCPyV viremia rate was similar in DES and non-DES patients (3/117 vs. 9/100, P = 0.07). The JCPyV levels were low (median peak levels, 1025 copies/mL) and JCPyV viremia was observed only once during the study period in most patients. All 3 DES patients with JCPyV(+) received 1 dose rituximab and no DES patients with >1 dose rituximab showed JCPyV(+). All 3 JCPyV(+) DES patients received LyD induction, while only 2 of 9 JCPyV(+) non-DES patients did so, and the remaining 7 received non-LyD or no induction. JCPyV in leukocyte was mostly negative in DES and non-DES patients. Immunosuppression in patients with or without JCPyV(+) was similar. BK polyomavirus viremia was observed more commonly in patients with JCPyV(+) than in those without (P < 0.02). CONCLUSIONS: Patients with IVIG + rituximab DES followed by transplantation with LyD induction and additional rituximab rarely show JCPyV viremia and appear at low risk for PML.

Quantifying the risk of incompatible kidney transplantation: a multicenter study.

Incompatible live donor kidney transplantation (ILDKT) offers a survival advantage over dialysis to patients with anti-HLA donor-specific antibody (DSA). Program-specific reports (PSRs) fail to account for ILDKT, placing this practice at regulatory risk. We collected DSA data, categorized as positive Luminex, negative flow crossmatch (PLNF) (n = 185), positive flow, negative cytotoxic crossmatch (PFNC) (n = 536) or positive cytotoxic crossmatch (PCC) (n = 304), from 22 centers. We tested associations between DSA, graft loss and mortality after adjusting for PSR model factors, using 9669 compatible patients as a comparison. PLNF patients had similar graft loss; however, PFNC (adjusted hazard ratio [aHR] = 1.64, 95% confidence interval [CI]: 1.15-2.23, p = 0.007) and PCC (aHR = 5.01, 95% CI: 3.71-6.77, p < 0.001) were associated with increased graft loss in the first year. PLNF patients had similar mortality; however, PFNC (aHR = 2.04; 95% CI: 1.28-3.26; p = 0.003) and PCC (aHR = 4.59; 95% CI: 2.98-7.07; p < 0.001) were associated with increased mortality. We simulated Centers for Medicare & Medicaid Services flagging to examine ILDKT's effect on the risk of being flagged. Compared to equal-quality centers performing no ILDKT, centers performing 5%, 10% or 20% PFNC had a 1.19-, 1.33- and 1.73-fold higher odds of being flagged. Centers performing 5%, 10% or 20% PCC had a 2.22-, 4.09- and 10.72-fold higher odds. Failure to account for ILDKT's increased risk places centers providing this life-saving treatment in jeopardy of regulatory intervention.

7th International Immunoglobulin Conference: Transplantation.

In transplantation, harnessing the immune system is essential for allograft survival and function. This session explores different aspects of the immune system during transplantation, including the effect of donor-specific anti-human leucocyte antigen (HLA) antibodies (DSAs), antibody-mediated rejection (AMR), B cell modulation and the role of immunoglobulin (Ig) therapy. It is well known that DSAs play a key role in the failure of allografts. Identifying and characterizing DSAs provides information that can aid in risk stratification of transplant recipients. The ability to bind complement provides additional information regarding the cytotoxic potential of these antibodies and can therefore potentially guide individualized treatment strategies. AMR presents as several phenotypes, which vary in severity. As such, potentially different treatment strategies are required, emphasizing the importance of accurate diagnosis. In patients with elevated anti-HLA antibodies, waiting times for a compatible organ are often prolonged. Desensitization protocols using intravenous immunoglobulin (IVIg), in combination with other therapies, have been developed to enhance the availability of compatible donors. Another important aspect of transplantation is the role of B cells. While B cells may be involved in AMR and forms of cellular rejection, there is evidence to suggest that regulatory B cells may also have a positive impact upon long-term graft survival. Hypogammaglobulinaemia (HGG) has been reported after solid organ transplantation and is associated with an increased risk of infections. Monitoring immunoglobulin G (IgG) levels post-transplantation may identify patients at risk for infections who could potentially benefit from pre-emptive treatment with IVIg.

7th International Immunoglobulin Conference: Transplantation.

The data presented highlight the complexity of the immune response during transplantation. Early identification and characterization of donor-specific anti-HLA antibodies (DSAs) allows for identification of patients at high risk of transplant rejection and offers information regarding appropriate intervention strategies. The availability of new diagnostic tools can also detect the presence of complement-binding antibodies, providing further information as to the cytotoxic potential of these antibodies. It is particularly encouraging to note that monitoring transplant recipients for the presence of various immune cells or immunoglobulin G (IgG) levels can provide detailed information regarding those at high risk for complications and therefore increased morbidity and mortality. Intervention strategies, either before or after transplantation, may potentially increase the long-term survival of allografts, thus enhancing patient outcomes. Future trials are warranted to assess these strategies in more detail.

Clinical aspects of intravenous immunoglobulin use in solid organ transplant recipients.

Intravenous immunoglobulin products (IVIG) are derived from pooled human plasma from thousands of donors and have been used for the treatment of primary immunodeficiency disorders for nearly 30 years. IVIG products are also effective in the treatment of autoimmune and inflammatory disorders, however the precise mechanism(s) of immune modulation are unknown. Recent data suggests that IVIG has a much broader ability to regulate cellular immunity, including innate and adaptive components. IVIG is also a recently recognized modifier of complement activation and injury. These attributes suggests IVIG would have clinical applications in solid organ transplantation. Analysis of clinical studies examining the use of IVIG in desensitization protocols and for treatment of antibody-mediated rejection (AMR) are supportive for kidney transplant recipients, although no clinical trials using IVIG in sensitized patients were performed seeking an Federal Drug Administration indication. Data regarding the use of IVIG for desensitization and treatment of AMR in cardiac and lung allograft recipients is not conclusive. IVIG is useful in the treatment and prevention of posttransplant infectious complications including cytomegalovirus, parvovirus B19 and polyoma BK virus. In addition, we address the risk of adverse events associated with IVIG use in sensitized end-stage renal disease and transplant patients.

Analysis of subcutaneous (SQ) alemtuzumab induction therapy in highly sensitized patients desensitized with IVIG and rituximab.

Here we report on our experience with subcutaneous (SQ) Alemtuzumab in an uncontrolled study in highly HLA-sensitized patients (HS). From 3/05-4/07, 54 HS patients received Alemtuzumab 30 mg SQ as induction. Patient and graft survival, AR episodes, serum creatinines, absolute lymphocyte counts, monthly PCR monitoring for viruses, AE/SAEs and infectious complications were monitored. No patient to date has developed acute injection-related reactions after SQ Alemtuzumab; however, bone marrow suppression was occasionally seen requiring reduction or elimination of mycophenolate mofetil approximately 1-2 months posttransplant. Patient and graft survival at 12 M was 98%/96%, respectively. AR episodes occurred in 35% with 20% being C4d+ AMR. Mean SCrs at 12 M were 1.4 +/- 0.3 mg/dL. The nadir ALC was 0.17 +/- 0.19 within 24 h and sustained up to 365 days posttransplant. Infections occurred in eight patients (five with polyoma BK viremia [PBK], one CMV/PBK and two CMV viremia). SQ Alemtuzumab was well tolerated and resulted in prolonged lymphocyte depletion. Compared to our previous experience with daclizumab and rabbit ATG induction in HS patients, single-dose SQ Alemtuzumab was more cost effective, showed similar infection rates and did not reduce the AMR rates posttransplant. Although uncontrolled, these observations suggest that induction therapy with Alemtuzumab appears feasible and indeed promising, but awaits more definitive study.

Venovenous Extracorporeal Membrane Oxygenation for Acute Respiratory Failure in a Liver Transplant Patient: A Case Report.

Intraoperative extracorporeal membrane oxygenation (ECMO) support, both venoarterial and venovenous (VV), have been used sparingly and with limited success in the setting of liver transplantation. Here, we report the successful use of VV-ECMO in the resuscitation and pulmonary bridging support after severe systemic inflammatory response in a combined liver and kidney transplant recipient who suffered primary nonfunction of both allografts. Where conventional ventilator maneuvers may prove ineffective, the implementation of VV-ECMO should be considered as a therapeutic option in limited, short-lived acute pulmonary injury.

1 alpha,25-dihydroxyvitamin D3 suppresses proliferation and immunoglobulin production by normal human peripheral blood mononuclear cells.

Activated B and T lymphocytes from normal human subjects are known to have the specific high-affinity receptor for 1,25-dihydroxyvitamin D3 (1,25-(OH)2-D3). In an attempt to determine a functional role for the sterol in such cells, we studied the effect of 1,25-(OH)2-D3 on DNA synthesis and Ig production by normal human peripheral blood mononuclear (PBM) cells activated in vitro by the polyclonal lymphocyte activators pokeweed mitogen and phytohemagglutinin, and the specific antigen dermatophyton O. A dose-dependent inhibition of [3H]thymidine incorporation was observed in cells incubated with 1,25-(OH)2-D3 in concentrations ranging from 10(-10) to 10(-7) M. Production of IgG and IgM, determined by enzyme-linked immunosorbent assay, was similarly inhibited by increasing concentrations of 1,25-(OH)2-D3. Half-maximal inhibition of DNA and Ig synthesis was found at 10(-10) to 10(-9) M 1,25-(OH)2-D3. This suppressive effect was specific for 1,25-(OH)2-D3; of the other vitamin D metabolites examined, only 10(-7) M 24R,25 dihydroxyvitamin D3 (24,25-(OH)2-D3) had a similar inhibitory effect. 1,25-(OH)2-D3 was not cytotoxic and did not affect unactivated PBMs. These data demonstrate that 1,25-(OH)2-D3 is a potent inhibitor of human PBM Ig production in vitro and suggest that this action is mediated through the hormone's antiproliferative effect on Ig-producing B cells and/or helper T cells.

Outcomes of Highly Sensitized Patients Undergoing Simultaneous Liver and Kidney Transplantation: A Single-Center Experience With Desensitization.

BACKGROUND: Preformed donor-specific human leukocyte antigen antibodies (DSAs) in patients undergoing simultaneous liver and kidney transplantation (SLKT) are an independent risk factor for poorer patient and renal allograft survival. The outcomes of patients highly sensitized (HS) against HLA antigens undergoing SLKT and select HS SLKT recipients undergoing desensitization at a high-volume desensitization center were investigated. METHODS: Seventy-five patients undergoing SLKT at a high-volume desensitization center between January 1, 2001, and December 31, 2015, were retrospectively reviewed. HS patients were defined by panel-reactive antibody (PRA) >30% (n = 17 patients), 11 of whom received pre- or perioperative desensitization with high-dose intravenous immunoglobulin (IVIG) ± rituximab. RESULTS: HS patients had significantly higher class I and class II PRA (class I = 41.3% ± 40.0% vs 2.5% ± 6.3%; class II = 45.7% ± 36.4% vs 1.0% ± 2.9%; P < .001), were more likely to be female (P = .05), and more likely to have had a prior transplant (P = .03). HS patients demonstrated greater susceptibility to renal cell-mediated rejection (CMR) (23.5% vs 5.2%, P = .02) compared to nonsensitized patients. Higher renal antibody-mediated rejection (ABMR) was also observed in HS patients, 11.8% vs 3.4%, but did not reach significance (P = .18). Desensitization in select HS SLKT patients was well tolerated but did not improve patient and allograft survival or significantly curtail rejection. CONCLUSION: HS SLKT recipients demonstrated increased allograft rejection, particularly CMR, but patient and graft survival were not impacted in the first year post-transplant. Select HS SLKT patients tolerated desensitization with high-dose IVIG ± rituximab and may have received additional immunoprotection against ABMR but survival was not affected.

Progress in Desensitization of the Highly HLA Sensitized Patient.

The presence of HLA antibodies remains a significant and often impenetrable barrier to kidney transplantation, leading to increased morbidity and mortality for patients remaining on long-term dialysis. In recent years, a number of new approaches have been developed to overcome these barriers. Intravenous immunoglobulin (IVIG) remains the lynchpin of HLA desensitization therapy and has been shown in a prospective, randomized, placebo-controlled trial to improve transplantation rates. In addition, IVIG used in low doses with plasma exchange is a reliable protocol for desensitization. Another significant advancement was the addition of rituximab (anti-B-cell therapy) to IVIG and plasma exchange-based desensitization. This approach has significantly improved rates of transplantation and outcomes. There is limited experience with bortezomib (anti-plasma cell therapy) and eculizumab (complement inhibition) for desensitization. However, recent data from a completed trial of eculizumab failed to show a significant benefit for prevention of antibody-mediated rejection compared with standard therapy plus placebo, and bortezomib produced inconsistent results. There is a growing interest in developing new therapeutic agents for desensitization. Newer approaches that address antibody reduction with B-cell depletion are discussed.

Complement Inhibition for Prevention and Treatment of Antibody-Mediated Rejection in Renal Allograft Recipients.

Therapeutic interventions aimed at the human complement system are recognized as potentially important strategies for the treatment of inflammatory and autoimmune diseases because there is often evidence of complement-mediated injury according to pathologic assessments. In addition, there are a large number of potential targets, both soluble and cell bound, that might offer potential for new drug development, but progress in this area has met with significant challenges. Currently, 2 drugs are approved aimed at inhibition of complement activation. The first option is eculizumab (anti-C5), which is approved for the treatment of paroxysmal nocturnal hemoglobinuria and atypical hemolytic uremic syndrome. Eculizumab has also been studied in human transplantation for the treatment and prevention of antibody-mediated rejection (ABMR). Initial data from uncontrolled studies suggested a significant benefit of eculizumab for the prevention of ABMR in highly HLA-sensitized patients, but a subsequent randomized, placebo-controlled trial failed to meet its primary endpoint. Anecdotal data, primarily from case studies, showed benefits in treating complement-mediated ABMR. A second approved complement-inhibiting therapy is C1 esterase inhibitor (C1-INH), which is approved for use in patients with hereditary angioedema, a condition caused by mutations in the gene that codes for C1-INH. A recent placebo-controlled trial of C1-INH for prevention of ABMR in HLA-sensitized patients found that the drug was safe, with evidence for inhibition of systemic complement activation and complement-activating donor-specific antibodies. Other drugs are now under development.