Pre-existing Humoral Immunity Research Articles

196. Antibodies to Vaccine-preventable Infections After CAR-T Cell Immunotherapy for B Cell Malignancies

BackgroundChimeric antigen receptor-modified T (CAR-T) cell immunotherapy for B cell hematologic malignancies results in prolonged B cell depletion. Little is known about the effects of CAR-T cell therapy on pre-existing pathogen-specific humoral immunity.MethodsWe conducted a prospective, cross-sectional study of children and adults treated with CD19- or BCMA-CAR-T cell therapy. Eligible patients were ≥ 6 months post-CAR-T cell infusion and in remission without subsequent chemoimmunotherapy. We measured total immunoglobulin G (IgG), pathogen-specific IgG levels for 12 vaccine-preventable infections, and B cell subsets from blood. Seroprotective antibody titers were based on standard thresholds. We described the proportion of patients with seroprotective titers and tested for associations between clinical factors and seroprotection using generalized estimating equations.ResultsWe enrolled 65 patients who received CD19- (n=54) or BCMA- (n=11) CAR-T cell therapy. Seven patients were < 18 years old. Samples were collected a median of 20 months (range, 7–68) after CAR T cell infusion. Seroprotection to vaccine-preventable pathogens was generally comparable to the U.S. population (Fig 1) even though blood CD19+ B cell counts were low (< 20 cells/mm3) in 60% of patients. Among 30 patients without IgG replacement in the prior 16 weeks (4 half-lives of IgG), 27 (90%) had hypogammaglobulinemia. Despite this, these individuals had seroprotection to a median of 67% (IQR, 59%-73%) of tested pathogens (Fig 2A). The proportion of patients with seroprotection was lowest for mumps, hepatitis A and B, H. influenzae type B (Hib), S. pneumoniae, and B. pertussis. Patients receiving BCMA-CAR-T cells had seroprotection to fewer pathogens than those receiving CD19-CAR-T cells (Fig 2B), but the difference did not reach statistical significance (Fig 3). There were no significant differences by other variables.Figure 1. Proportion of CAR-T cell recipients with seroprotection to vaccine-preventable infections compared to the U.S. population, stratified by receipt of IgG replacement in the previous 16 weeks. Figure 2 A-B. Percentage of pathogens with seroprotective antibody titers among patients without IgG replacement in the previous 16 weeks. Figure 3. Association of clinical factors with seroprotection to vaccine-preventable infections among patients without IgG replacement in the previous 16 weeks (n=30) ConclusionSeroprotection for vaccine-preventable infections after CD19-CAR-T cell therapy was comparable to the general population. BCMA-CAR-T cell recipients may benefit most from replacement IgG. Vaccinations after CAR-T cell therapy should be considered and prioritized for S. pneumoniae, Hib, hepatitis viruses, and B. pertussis.Disclosures Justin J. Taylor, PhD, Vir Biotechnology (Grant/Research Support) Damian J. Green, MD, Cellectar Biosciences (Grant/Research Support)GSK (Advisor or Review Panel member)Juno Therapeutics (Grant/Research Support, Advisor or Review Panel member, Other Financial or Material Support, Royalities)Seattle Genetics (Grant/Research Support, Advisor or Review Panel member) Michael Boeckh, MD PhD, AlloVir (Consultant)EvrysBio (Advisor or Review Panel member, Other Financial or Material Support, share options)Gilead (Consultant, Grant/Research Support)GSK (Consultant)Helocyte (Advisor or Review Panel member, Shareholder)Lophius (Grant/Research Support)Merck (Consultant, Grant/Research Support)SymBio (Consultant)VirBio (Consultant, Grant/Research Support) David G. Maloney, MD, PhD, A2 Biotherapeutics (Consultant, Other Financial or Material Support, Stock Options)Bioline Rx (Consultant)Celgene (Consultant, Grant/Research Support)Gilead (Consultant)Juno Therapeutics (Consultant, Research Grant or Support, Other Financial or Material Support, four pending patents, not issued, licensed, no royalities, no licensees)Kite Pharma (Consultant, Grant/Research Support)Novartis (Consultant)Pharmacyclics (Consultant) Cameron J. Turtle, MBBS, PhD, Allogene (Other Financial or Material Support, Ad hoc advisory board (last 12 months))ArsenalBio (Advisor or Review Panel member, Other Financial or Material Support, Stock/options)AstraZeneca (Grant/Research Support, Other Financial or Material Support, Ad hoc advisory board (last 12 months))Caribou Biosciences (Advisor or Review Panel member, Other Financial or Material Support, Stock/options)Century Therapeutics (Advisor or Review Panel member)Eureka Therapeutics (Advisor or Review Panel member, Other Financial or Material Support, Stock/options)Juno Therapeutics (Grant/Research Support, Other Financial or Material Support, Patent: Licensed to Juno Therapeutics)Myeloid Therapeutics (Advisor or Review Panel member, Other Financial or Material Support, Stock/options)Nektar Therapeutics (Grant/Research Support, Other Financial or Material Support, Ad hoc advisory board (last 12 months))PACT Pharma (Other Financial or Material Support, Ad hoc advisory board (last 12 months))Precision Biosciences (Advisor or Review Panel member, Other Financial or Material Support, Stock/options)TCR2 Therapeutics (Grant/Research Support)T-CURX (Advisor or Review Panel member) Joshua A. Hill, MD, Allogene (Consultant)Allovir (Consultant)Gilead (Consultant)Karius (Grant/Research Support, Scientific Research Study Investigator)Takeda (Grant/Research Support, Scientific Research Study Investigator)

Evidence and implications of pre‐existing humoral cross‐reactive immunity to SARS‐CoV‐2

BackgroundSevere acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) has emerged throughout the world. Building knowledge around Covid‐19 is crucial to devise facts based approaches to respond efficiently against this pandemic.AimWe aimed to investigate pre‐existing humoral cross‐reactive immunity to SARS‐CoV‐2.MethodWe have tested the reactivity against SARS‐CoV‐2 nucleocapsid (N) antigen of sera collected from healthy healthcare volunteers in 2014. We assessed immunoglobulins reactive against SARS‐CoV‐2 N‐antigen using a well‐validated serological platform; Elecsys assay.ResultsSera from 32 subjects (out of 135 [23.7%]) were reactive to SARS‐CoV‐2 N‐antigen, suggesting the presence of anti‐SARS‐CoV‐2 N‐antigen antibodies.ConclusionAlthough the clinical relevance of the observed reactivity can only be speculated and needs to be investigated, the implication of this finding for coronavirus disease 2019 seroepidemiological survey and vaccines' clinical trials is critical.

Early Phase Clinical Immunogenicity of Valoctocogene Roxaparvovec, an AAV5-Mediated Gene Therapy for Hemophilia A

Evaluation of immune responses to adeno-associated virus (AAV)-mediated gene therapies prior to and following dose administration plays a key role in determining therapeutic safety and efficacy. This report describes up to 3 years of immunogenicity data following administration of valoctocogene roxaparvovec (BMN 270), an AAV5-mediated gene therapy encoding human B domain-deleted FVIII (hFVIII-SQ) in a phase 1/2 clinical study of adult males with severe hemophilia A. Patients with pre-existing humoral immunity to AAV5 or with a history of FVIII inhibitors were excluded from the trial. Blood plasma and peripheral blood mononuclear cell (PBMC) samples were collected at regular intervals following dose administration for assessment of humoral and cellular immune responses to both the AAV5 vector and transgene-expressed hFVIII-SQ. The predominant immune response elicited by BMN 270 administration was largely limited to the development of antibodies against the AAV5 capsid that were cross-reactive with other common AAV serotypes. No FVIII inhibitor responses were observed within 3 years following dose administration. In a context of prophylactic or on-demand corticosteroid immunosuppression given after vector infusion, AAV5 and hFVIII-SQ peptide-specific cellular immune responses were intermittently detected by an interferon (IFN)-γ and tumor necrosis factor (TNF)-α FluoroSpot assay, but they were not clearly associated with detrimental safety events or changes in efficacy measures.

Newcastle disease virus (NDV) expressing the spike protein of SARS-CoV-2 as a live virus vaccine candidate.

BackgroundDue to the lack of protective immunity of humans towards the newly emerged SARS-CoV-2, this virus has caused a massive pandemic across the world resulting in hundreds of thousands of deaths. Thus, a vaccine is urgently needed to contain the spread of the virus.MethodsHere, we describe Newcastle disease virus (NDV) vector vaccines expressing the spike protein of SARS-CoV-2 in its wild type format or a membrane-anchored format lacking the polybasic cleavage site. All described NDV vector vaccines grow to high titers in embryonated chicken eggs. In a proof of principle mouse study, the immunogenicity and protective efficacy of these NDV-based vaccines were investigated.FindingsWe report that the NDV vector vaccines elicit high levels of antibodies that are neutralizing when the vaccine is given intramuscularly in mice. Importantly, these COVID-19 vaccine candidates protect mice from a mouse-adapted SARS-CoV-2 challenge with no detectable viral titer and viral antigen in the lungs.InterpretationThe results suggested that the NDV vector expressing either the wild type S or membrane-anchored S without the polybasic cleavage site could be used as live vector vaccine against SARS-CoV-2.FundingThis work is supported by an NIAID funded Center of Excellence for Influenza Research and Surveillance (CEIRS) contract, the Collaborative Influenza Vaccine Innovation Centers (CIVIC) contract, philanthropic donations and NIH grants.

First-in-Human Gene Therapy Study of AAVhu37 Capsid Vector Technology in Severe Hemophilia A - BAY 2599023 has Broad Patient Eligibility and Stable and Sustained Long-Term Expression of FVIII

Background Gene therapy for hemophilia A has the potential to reduce the treatment burden for patients and their care providers by eliminating the need for regular factor VIII (FVIII) prophylaxis through long-term expression of endogenous FVIII at levels sufficient to provide bleed protection. Host immunity to the capsid serotype limits patients' eligibility and may impact the balance between vector dose and clinical outcome. BAY 2599023 (AAVhu37FVIII) is the first clinical-stage adeno-associated virus (AAV) gene therapy vector based on the AAVhu37 serotype. BAY 2599023 is a non-replicating AAV vector and contains a single-stranded DNA genome encoding a B-domain-deleted FVIII, under the control of a liver-specific promoter/enhancer combination optimized for transgenic expression. The AAVhu37 capsid is a member of the hepatotropic clade E family, and was selected based on preclinical studies demonstrating efficient liver-directed FVIII gene transfer, favorable biodistribution and durable FVIII expression. However, pre-existing humoral immunity against AAV capsids may limit patient eligibility. Here, we evaluate the seroprevalence and titer levels of pre-existing neutralizing antibodies (Nabs) against AAVhu37, and additional AAV capsids, using cell-based transduction inhibition assays. We also report current, preliminary, long-term safety and FVIII activity following a single intravenous infusion of BAY 2599023, in a phase 1/2 open-label, first-in-human, dose-finding study (NCT03588299). Methods Seroprevalence and titer distribution of Nabs against AAVhu37, AAV5 and AAV8 have been assessed in serum samples derived from 100 US patients with hemophilia A (African American and Caucasian male donors, 19-61 years). For AAVhu37, the clinical trial Nab assay was utilized to determine Nab titer levels according to cellular transduction inhibition. Additionally, we developed and fully validated Nab assays for AAV5 and AAV8. The ongoing BAY 2599023 phase 1/2 dose-finding study included male patients aged ≥18 years with severe hemophilia A, each receiving a single intravenous infusion of BAY 2599023. Patients were enrolled sequentially into three dose cohorts (0.5 × 1013 GC/kg, 1.0 × 1013 GC/kg and 2.0 × 1013 GC/kg), each comprising two patients. Patients had no history of FVIII inhibitors, no detectable neutralizing immunity against the AAVhu37 capsid above a Nab titer of 1:5, and ≥150 exposure days to FVIII products. Primary endpoints were adverse events (AEs), serious AEs (SAEs) and AEs/SAEs of special interest (S/AESIs). The secondary endpoint was change in FVIII activity from baseline. Informed patient consent and ethics committee approval were obtained. Results In the seroprevalence study, the lowest pre-existing Nab prevalence was found for AAVhu37, with a low maximum observed titer of 1:26. Based on our results, 86% of patients would be eligible for AAVhu37-based treatment (Table 1). To date, patients in the first (0.5 × 1013 GC/kg) and second cohort (1.0 × 1013 GC/kg) have completed ≥52 weeks of observation; patients in cohort 3 (2.0 × 1013 GC/kg) have at least 33 weeks of observation. Regardless of the level achieved and the assay used, 5 out of 6 of patients show sustained FVIII levels (all ≥5%) over time and up to 16 months. Patients in cohorts 2 and 3 have all been off prophylaxis since ~6 weeks after gene transfer. No spontaneous bleeds were reported after achieving protective FVIII levels (&amp;gt;15 IU/dL) and discontinuation of prophylaxis in the third cohort. No SAEs have been reported to date. Mild-to-moderate elevation in alanine aminotransferase/aspartate aminotransferase were recorded for one patient in the second cohort and both patients in the third cohort. All were treated with corticosteroids (one resolved, two in resolution). The latest follow-up data for up to 22 months will be presented. Conclusions BAY 2599023 has a broad patient eligibility due to low seroprevalence and low titers of pre-existing Nabs against AAVhu37 compared with other AAVs. BAY 2599023 has a good safety profile, with the potential to achieve endogenous expression of FVIII at therapeutic levels over an extended period. Successful proof-of-concept has been achieved, with measurable and sustained expression of endogenous FVIII. Disclosures Pipe: Apcintex, Bayer, BioMarin, Catalyst Biosciences, CSL Behring, HEMA Biologics, Freeline, Novo Nordisk, Pfizer, F. Hoffmann-La Roche Ltd/Genentech, Inc., Sangamo Therapeutics, Sanofi, Takeda, Spark Therapeutics, uniQure: Consultancy; Siemens: Research Funding; Medical and Scientific Advisory Council to the National Hemophilia Foundation; Medical Advisory Board to World Federation of Hemophilia: Membership on an entity's Board of Directors or advisory committees. Ferrante:Bayer: Current Employment. Reis:Bayer: Current Employment. Wiegmann:Bayer: Current Employment. Lange:Bayer: Current Employment, Current equity holder in private company. Braun:Bayer: Current Employment, Current equity holder in private company. Michaels:Bayer: Current Employment.

Memory Lapses—Winning the Slow Race

Pre-existing humoral immunity can impact immune responses to heterologous infections. In this issue of Immunity, Wong etal. reveal that memory B cells, while failing to re-enter the germinal center, create an affinity-restricted, diversified B cell repertoire for rapid plasma blast responses. Their findings have important implications to vaccine design.

The Effects of Genetic Variation on H7N9 Avian Influenza Virus Pathogenicity.

Since the H7N9 avian influenza virus emerged in China in 2013, there have been five seasonal waves which have shown human infections and caused high fatality rates in infected patients. A multibasic amino acid insertion seen in the HA of current H7N9 viruses occurred through natural evolution and reassortment, and created a high pathogenicity avian influenza (HPAI) virus from the low pathogenicity avian influenza (LPAI) in 2017, and significantly increased pathogenicity in poultry, resulting in widespread HPAI H7N9 in poultry, which along with LPAI H7N9, contributed to the severe fifth seasonal wave in China. H7N9 is a novel reassorted virus from three different subtypes of influenza A viruses (IAVs) which displays a great potential threat to public health and the poultry industry. To date, no sustained human-to-human transmission has been recorded by the WHO. However, the high ability of evolutionary adaptation of H7N9 and lack of pre-existing immunity in humans heightens the pandemic potential. Changes in IAVs proteins can affect the viral transmissibility, receptor binding specificity, pathogenicity, and virulence. The multibasic amino acid insertion, mutations in hemagglutinin, deletion and mutations in neuraminidase, and mutations in PB2 contribute to different virological characteristics. This review summarized the latest research evidence to describe the impacts of viral protein changes in viral adaptation and pathogenicity of H7N9, aiming to provide better insights for developing and enhancing early warning or intervention strategies with the goal of preventing highly pathogenic IAVs circulation in live poultry, and transmission to humans.

Formulation of the prefusion RSV F protein with a Th1/Th2-balanced adjuvant provides complete protection without Th2-skewed immunity in RSV-experienced young mice

Respiratory syncytial virus (RSV) is a leading cause of lower respiratory tract infections among infants with most infections occurring in the first year of life. Multiple RSV exposures are required for children to mount adult-like immune responses. Although adult RSV immunity is associated with less severe disease, the protection induced through natural infection is short-lived. Therefore, vaccination of RSV-experienced young children may accelerate immunity and provide long-term protection from RSV reinfection. However, the extent to which different Th-biased vaccine regimens influence pre-existing humoral and cellular immunity in RSV-experienced young children is unknown. To address this question, infant BALB/c mice were RSV-infected and subsequently immunized with the prefusion RSV F (PreF) antigen formulated with either a Th2-skewing (Alum) or Th1/Th2-balanced (Advax-SM) adjuvant. These studies show that both adjuvants boosted neutralizing antibody and protected from RSV reinfection, but Advax-SM adjuvant prevented the Th2-skewed immunity observed in RSV-experienced young mice immunized with PreF/Alum.

Adeno-associated virus-binding antibodies detected in cats living in the Northeastern United States lack neutralizing activity

Cats are a critical pre-clinical model for studying adeno-associated virus (AAV) vector-mediated gene therapies. A recent study has described the high prevalence of anti-AAV neutralizing antibodies among domestic cats in Switzerland. However, our knowledge of pre-existing humoral immunity against various AAV serotypes in cats is still limited. Here, we show that, although antibodies binding known AAV serotypes (AAV1 to AAV11) are prevalent in cats living in the Northeastern United States, these antibodies do not necessarily neutralize AAV infectivity. We analyzed sera from 35 client-owned, 20 feral, and 30 specific pathogen-free (SPF) cats for pre-existing AAV-binding antibodies against the 11 serotypes. Antibody prevalence was 7 to 90% with an overall median of 50%. The AAV-binding antibodies showed broad reactivities with other serotypes. Of 44 selected antibodies binding AAV2, AAV6 or AAV9, none exhibited appreciable neutralizing activities. Instead, AAV6 or AAV9-binding antibodies showed a transduction-enhancing effect. AAV6-binding antibodies were highly prevalent in SPF cats (83%), but this was primarily due to cross-reactivity with preventive vaccine-induced anti-feline panleukopenia virus antibodies. These results indicate that prevalent pre-existing immunity in cats is not necessarily inhibitory to AAV and highlight a substantial difference in the nature of AAV-binding antibodies in cats living in geographically different regions.

Characterizing Emerging Canine H3 Influenza Viruses.

The continual emergence of novel influenza A strains from non-human hosts requires constant vigilance and the need for ongoing research to identify strains that may pose a human public health risk. Since 1999, canine H3 influenza A viruses (CIVs) have caused many thousands or millions of respiratory infections in dogs in the United States. While no human infections with CIVs have been reported to date, these viruses could pose a zoonotic risk. In these studies, the National Institutes of Allergy and Infectious Diseases (NIAID) Centers of Excellence for Influenza Research and Surveillance (CEIRS) network collaboratively demonstrated that CIVs replicated in some primary human cells and transmitted effectively in mammalian models. While people born after 1970 had little or no pre-existing humoral immunity against CIVs, the viruses were sensitive to existing antivirals and we identified a panel of H3 cross-reactive human monoclonal antibodies (hmAbs) that could have prophylactic and/or therapeutic value. Our data predict these CIVs posed a low risk to humans. Importantly, we showed that the CEIRS network could work together to provide basic research information important for characterizing emerging influenza viruses, although there were valuable lessons learned.

Antibodies to coronaviruses are higher in older compared with younger adults and binding antibodies are more sensitive than neutralizing antibodies in identifying coronavirus-associated illnesses.

Human coronaviruses (HCoV) are common causes of respiratory illnesses (RI) despite preexisting humoral immunity. Sera were obtained near the onset of RI and 3 to 4 weeks later as part of a prospective study of 200 subjects evaluated for RI from 2009 to 2013. Antibodies against common HCoV strains were measured by enzyme‐linked immunosorbent assay and neutralization assay comparing older adults with cardiopulmonary diseases (99 subjects) to younger, healthy adults (101 subjects). Virus shedding was detected in respiratory secretions by polymerase chain reaction. Of 43 HCoV‐associated illnesses, 15 (35%) occurred in 14 older adults (aged ≥60 years) and 28 (65%) in 28 younger adults (aged 21‐40 years). Binding and neutralizing antibodies were higher in older adults. Only 16 (35.7%) of RI with increases in binding antibodies also had increases in neutralizing antibodies to HCoV. Increases in binding antibodies with RI were more frequent than increased neutralizing antibodies and virus shedding, and more frequent in younger compared to older adults. Functional neutralizing antibodies were not stimulated as often as binding antibodies, explaining in part a susceptibility to reinfection with HCoV. Monitoring binding antibodies may be more sensitive for the serologic detection of HCoV infections.

Oracle or false prophet? Can we predict AAV efficacy based on preexisting antibody titers?

Oracle or false prophet? Can we predict AAV efficacy based on preexisting antibody titers?

Characterization of swine-origin H1N1 canine influenza viruses

ABSTRACT Host switch events of influenza A viruses (IAVs) continuously pose a zoonotic threat to humans. In 2013, swine-origin H1N1 IAVs emerged in dogs soon after they were detected in swine in the Guangxi province of China. This host switch was followed by multiple reassortment events between these H1N1 and previously circulating H3N2 canine IAVs (IAVs-C) in dogs. To evaluate the phenotype of these newly identified viruses, we characterized three swine-origin H1N1 IAVs-C and one reassortant H1N1 IAV-C. We found that H1N1 IAVs-C predominantly bound to human-type receptors, efficiently transmitted via direct contact in guinea pigs and replicated in human lung cells. Moreover, the swine-origin H1N1 IAVs-C were lethal in mice and were transmissible by respiratory droplets in guinea pigs. Importantly, sporadic human infections with these viruses have been detected, and preexisting immunity in humans might not be sufficient to prevent infections with these new viruses. Our results show the potential of H1N1 IAVs-C to infect and transmit in humans, suggesting that these viruses should be closely monitored in the future.

The Effect of Preexisting Immunity on Virus Detection and Immune Responses in a Phase II, Randomized Trial of a Russian-Backbone, Live, Attenuated Influenza Vaccine in Bangladeshi Children

BackgroundIn a 2012 Phase II clinical trial, 300 Bangladeshi children aged 24 to 59 months with no prior influenza vaccine exposure were randomized to receive a single intranasally-administered dose of either trivalent, Russian-backbone, live, attenuated influenza vaccine (LAIV) or placebo. Protocol-defined analyses, presented in the companion manuscript, demonstrate decreased viral detection and immunogenicity for A/H1N1pdm09, relative to the A/H3N2 and B strains. This post hoc analysis of the trial data aims to investigate the LAIV strain differences by testing the hypothesis that preexisting humoral and mucosal immunity may influence viral recovery and immune responses after LAIV receipt.MethodsWe used logistic regressions to evaluate the relations between markers of preexisting immunity (ie, hemagglutination inhibition [HAI], microneutralization, and immunoglobulin G and immunoglobulin A (both serum and mucosal antibodies) and LAIV viral recovery in the week post-vaccination. We then tested for potential effect modification by baseline HAI titers (ie, <10 versus ≥10) and week 1 viral recovery on the LAIV-induced serum and mucosal immune responses, measured between days 0 and 21 post-vaccination.ResultsHigher levels of preexisting immunity to influenza A/H3N2 and B were strongly associated with strain-specific prevention of viral shedding upon LAIV receipt. While evidence of LAIV immunogenicity was observed for all 3 strains, the magnitudes of immune responses were most pronounced in children with no evidence of preexisting HAI and in those with detectable virus.ConclusionsThe results provide evidence for a bidirectional association between viral replication and immunity, and underscore the importance of accounting for preexisting immunity when evaluating virologic and immunologic responses to LAIVs.Clinical Trials RegistrationNCT01625689.

Assessment of Humoral Immunity to Hepatitis B, Measles, Rubella, and Mumps in Children After Chemotherapy.

Cancer survival rates and longevity of patients after therapy have significantly improved during the last few decades. Therefore, lasting protection against infections should be provided. A total of 162 children diagnosed with acute lymphoblastic leukemia, acute myelogenous leukemia, solid tumors, non-Hodgkin lymphoma, and Hodgkin lymphoma were enrolled in the study. Antibody levels against hepatitis B virus was assessed both at the time of diagnosis and within 6 months after completion of chemotherapy. However, measles, mumps, and rubella (MMR) antibodies levels were measured just within 6 months after completion of chemotherapy. Anti-HBs antibody titers had decreased below the protective level after treatment in 25 of 96 patients having protective antibody levels for hepatitis B virus before therapy. In 66 patients without pretreatment protective levels of antibody, in spite of the immunization during chemotherapy, only 6 of them were found to be anti-HBS positive after treatment. In 153 patients previously vaccinated with MMR, 19 had protective antibody titers after treatment. MMR seropositivities were negatively correlated to age as expected. Our data demonstrate that a significant number of children lose preexisting humoral immunity against MMR and hepatitis B after completion of chemotherapy.

Incomplete Memories: The Natural Suppression of Tissue-Resident Memory CD8 T Cells in the Lung.

The yearly, cyclic impact of viruses like influenza on human health and the economy is due to the high rates of mutation of traditional antibody targets, which negate any preexisting humoral immunity. However, the seasonality of influenza infections can equally be attributed to an absent or defective memory CD8 T cell response since the epitopes recognized by these cells are derived from essential virus proteins that mutate infrequently. Experiments in mouse models show that protection from heterologous influenza infection is temporally limited and conferred by a population of tissue-resident memory (TRM) cells residing in the lung and lung airways. TRM are elicited by a diverse set of pathogens penetrating mucosal barriers and broadly identified by extravascular staining and expression of the activation and adhesion molecules CD69 and CD103. Interestingly, lung TRM fail to express these molecules, which could limit tissue retention, resulting in airway expulsion or death with concomitant loss of heterologous protection. Here, we make the case that respiratory infections uniquely evoke a form of natural immunosuppression whereby specific cytokines and cell–cell interactions negatively impact memory cell programming and differentiation. Respiratory memory is not only short-lived but most of the memory cells in the lung parenchyma may not be bona fide TRM. Given the quantity of microbes humans inhale over a lifetime, limiting cellular residence could be a mechanism employed by the respiratory tract to preserve organismal vitality. Therefore, successful efforts to improve respiratory immunity must carefully and selectively breach these inherent tissue barriers.

Recent advances in vesicular stomatitis virus-based oncolytic virotherapy: a 5-year update.

Oncolytic virus (OV) therapy is an anti-cancer approach that uses viruses that preferentially infect, replicate in and kill cancer cells. Vesicular stomatitis virus (VSV, a rhabdovirus) is an OV that is currently being tested in the USA in several phase I clinical trials against different malignancies. Several factors make VSV a promising OV: lack of pre-existing human immunity against VSV, a small and easy to manipulate genome, cytoplasmic replication without risk of host cell transformation, independence of cell cycle and rapid growth to high titres in a broad range of cell lines facilitating large-scale virus production. While significant advances have been made in VSV-based OV therapy, room for improvement remains. Here we review recent studies (published in the last 5 years) that address 'old' and 'new' challenges of VSV-based OV therapy. These studies focused on improving VSV safety, oncoselectivity and oncotoxicity; breaking resistance of some cancers to VSV; preventing premature clearance of VSV; and stimulating tumour-specific immunity. Many of these approaches were based on combining VSV with other therapeutics. This review also discusses another rhabdovirus closely related to VSV, Maraba virus, which is currently being tested in Canada in phase I/II clinical trials.

Enhanced liver gene transfer and evasion of preexisting humoral immunity with exosome-enveloped AAV vectors

AbstractResults from clinical trials of liver gene transfer for hemophilia demonstrate the potential of the adeno-associated virus (AAV) vector platform. However, to achieve therapeutic transgene expression, in some cases high vector doses are required, which are associated with a higher risk of triggering anti-capsid cytotoxic T-cell responses. Additionally, anti-AAV preexisting immunity can prevent liver transduction even at low neutralizing antibody (NAb) titers. Here, we describe the use of exosome-associated AAV (exo-AAV) vectors as a robust liver gene delivery system that allows the therapeutic vector dose to be decreased while protecting from preexisting humoral immunity to the capsid. The in vivo efficiency of liver targeting of standard AAV8 or AAV5 and exo-AAV8 or exo-AAV5 vectors expressing human coagulation factor IX (hF.IX) was evaluated. A significant enhancement of transduction efficiency was observed, and in hemophilia B mice treated with 4 × 1010 vector genomes per kilogram of exo-AAV8 vectors, a staggering ∼1 log increase in hF.IX transgene expression was observed, leading to superior correction of clotting time. Enhanced liver expression was also associated with an increase in the frequency of regulatory T cells in lymph nodes. The efficiency of exo- and standard AAV8 vectors in evading preexisting NAbs to the capsid was then evaluated in a passive immunization mouse model and in human sera. Exo-AAV8 gene delivery allowed for efficient transduction even in the presence of moderate NAb titers, thus potentially extending the proportion of subjects eligible for liver gene transfer. Exo-AAV vectors therefore represent a platform to improve the safety and efficacy of liver-directed gene transfer.

P 2 Effect of ocrelizumab on humoral immunity markers in the phase iii, double-blind, double-dummy, IFN[formula omitted]-1a–controlled OPERA I and OPERA II studies

Background Ocrelizumab (OCR) is a humanized monoclonal antibody that targets CD20+B cells. Selective depletion of CD20+B cells may potentially preserve the capacity for B-cell reconstitution and preexisting humoral immunity. Objective To assess the effect of OCR on specific humoral immunity in 2 identical Phase III, randomized, double- blind, double-dummy, IFN-beta-1a (IFN β -1a)-controlled trials in relapsing multiple sclerosis (OPERA I and OPERA II). Methods In OPERA I and OPERA II, patients were randomized 1:1 to receive OCR 600 mg via intravenous infusion every 24 weeks or subcutaneous IFN β -1a 44 μ g three-times weekly over the 96-week study treatment period. Prior to study enrollment, physicians were advised to review patient immunization status and follow local guidance for vaccination; immunizations were to be completed ⩾ 6 weeks prior to treatment. Measurements of antibody (Ab) titers against mumps, rubella, varicella, and Streptococcus pneumoniae were taken at baseline and at Weeks 12, 24, 48, 72, and 96. The proportion of patients with Ab levels that could be considered protective was assessed for each treatment group over time. Results The pooled safety analysis of the OPERA I and OPERA II studies included 826 IFN β -1a-treated and 825 OCR-treated patients. At baseline, 94.1% and 93.6% of the IFN β -1a and OCR groups, respectively, had positive levels of mumps Ab; this proportion ranged (min–max) 92.7–94.8% and 91.8–93.5% over the 6 measurements taken during the 96-week study treatment period. Positive rubella Ab levels were seen among 87.9% and 89.0% of the IFN β -1a and OCR groups, respectively, at baseline and ranged 89.8–90.8% and 88.7–89.4% over the treatment period. Positive varicella Ab levels were seen in 95.5% of both treatment groups at baseline and ranged 96.2–97.5% and 94.8–95.6% over the treatment period in the IFN β -1a and OCR groups, respectively. Among the evaluable patients, the mean (standard deviation) level of S. pneumoniae Ab was 53.67 (54.13) mg/L and 55.35 (67.00) mg/L at baseline; at 96 weeks, the mean change from baseline was −1.13 (40.25) mg/L and −1.99 (59.60) mg/L in the IFN β -1a and OCR groups, respectively. Conclusions In OPERA I and OPERA II, Ab titers against common viral and bacterial antigens were similar between the IFN β -1a and OCR groups at baseline and were maintained during the 96-week study treatment period. Treatment with OCR does not appear to affect preexisting humoral immunity. This study is sponsored by F. Hoffmann-La Roche Ltd.

Replication and Oncolytic Activity of an Avian Orthoreovirus in Human Hepatocellular Carcinoma Cells.

Oncolytic viruses are cancer therapeutics with promising outcomes in pre-clinical and clinical settings. Animal viruses have the possibility to avoid pre-existing immunity in humans, while being safe and immunostimulatory. We isolated an avian orthoreovirus (ARV-PB1), and tested it against a panel of hepatocellular carcinoma cells. We found that ARV-PB1 replicated well and induced strong cytopathic effects. It was determined that one mechanism of cell death was through syncytia formation, resulting in apoptosis and induction of interferon stimulated genes (ISGs). As hepatitis C virus (HCV) is a major cause of hepatocellular carcinoma worldwide, we investigated the effect of ARV-PB1 against cells already infected with this virus. Both HCV replicon-containing and infected cells supported ARV-PB1 replication and underwent cytolysis. Finally, we generated in silico models to compare the structures of human reovirus- and ARV-PB1-derived S1 proteins, which are the primary targets of neutralizing antibodies. Tertiary alignments confirmed that ARV-PB1 differs from its human homolog, suggesting that immunity to human reoviruses would not be a barrier to its use. Therefore, ARV-PB1 can potentially expand the repertoire of oncolytic viruses for treatment of human hepatocellular carcinoma and other malignancies.