Virus-specific B-cell Research Articles

Asymmetric Cross-Protection is Elicited by Distinct Influenza B Lineages

Abstract The immune response to influenza B virus (IBV) infection is understudied compared to influenza A virus (IAV), despite IBV accounting for 20% of influenza-related hospitalizations annually. Influenza B was first isolated in the 1940s and subsequently diverged into two distinct lineages, Victoria (B/Vic) and Yamagata (B/Yam), defined by changes in the hemagglutinin (HA) and basic polymerase (PB1 and PB2) gene segments. The two IBV lineages are antigenically distinct, resulting in the development of influenza vaccines containing both B/Vic and B/Yam in addition to H1N1 and H3N2 IAVs. Differential epidemiologic dynamics of the IBV lineages and the recent proposed extinction of B/Yam suggests the lineages do not elicit equivalent immunity. Human studies have shown B/Yam-infected persons are susceptible to reinfection with the same lineage virus, suggesting B/Yam-elicited immunity is insufficient compared to B/Vic-elicited immunity, which prevents homotypic reinfection. Here we established a murine model of contemporary IBV infection that supports observational studies. We demonstrated immune responses elicited by B/Yam infection is insufficient to protect against a heterolineal infection (B/Vic challenge). Conversely, B/Vic-elicited immunity protected against homologous and heterolineal (B/Yam) challenge. We assessed virus-specific serum antibody (Ab) responses following primary infection and challenge. Serological data suggest B/Yam infection failed to elicit cross-reactive Ab, allowing B/Vic infection, while B/Vic elicited serum Ab against both lineages. Ongoing studies seek to define the virus-specific B-cell response to B/Yam and B/Vic infection and to confirm these results in a ferret model of IBV infection. Supported by grants from NIH Contract 75N93021C00018

Identification of virus-specific B-cell epitopes by convalescent plasma from COVID-19 patients

Identification of immunologic epitopes against SARS-CoV-2 is crucial for the discovery of diagnostic, therapeutic, and preventive targets. In this study, we used a pan-coronavirus peptide microarray to screen for potential B-cell epitopes and validated the results with peptide-based ELISA. Specifically, we identified three linear B-cell epitopes on the SARS-CoV-2 proteome, which were recognized by convalescent plasma from COVID-19 patients. Interestingly, two epitopes (S 809–823 and R1ab 909–923) strongly reacted to convalescent plasma collected at the early phase (< 90 days) of COVID-19 symptom onset, whereas one epitope (M 5–19) reacted to convalescent plasma collected > 90 days after COVID-19 symptom onset. Neutralization assays using antibody depletion with the identified spike (S) peptides revealed that three S epitopes (S 557–571, S 789–803, and S 809–823) elicited neutralizing antibodies in COVID-19 patients. However, the levels of virus-specific antibody targeting S 789–803 only positively correlated with the neutralizing rates at the early phase (<60 days) after disease onset, and the antibody titers diminished quickly with no correlation to the neutralizing activity beyond two months after recovery from COVID-19. Importantly, stimulation of peripheral blood mononuclear cells from COVID-19-recovered patients with these SARS-CoV-2 S peptides resulted in poor virus-specific B cell activation, proliferation, differentiation into memory B cells, and production of immunoglobulin G (IgG) antibodies, despite the B-cells being functionally competent as demonstrated by their response to non-specific stimulation. Taken together, these findings indicate that these newly identified SARS-CoV-2-specific B-cell epitopes can elicit neutralizing antibodies, with titers and/or neutralizing activities declining significantly within 2–3 months in the convalescent plasma of COVID-19 patients.

Association of envelope-specific B-cell differentiation and viral selective pressure signatures in HIV-1 CRF01_AE infection.

In HIV type 1 (HIV-1) infection, virus-specific B-cell and neutralizing antibody (NAb) responses are impaired but exert selective pressure on target viral Envelope (Env) resulting in prominent sequence diversification among geographical areas. The basal induction patterns of HIV Env-specific B cells and their interaction with HIV Env awaits clarification. We investigated the relationship of Env polymorphisms and Env-specific B-cell responses in treatment-naive HIV-1 CRF01_AE-infected Vietnamese. Samples of 43 HIV-1 CRF01_AE infection-identified individuals were divided into acute-phase ( n = 12) and chronic-phase ( n = 31) by combined criteria of serological recent-infection assay and clinical parameters. We quantified subcloning-based polymorphic residue site numbers in plasma-derived Env variable region 1-5 (V1-V5)-coding regions within each individual, designating their summation within each region as variant index. Peripheral blood Env gp 140-specific B-cell responses and plasma neutralizing activity of Env pseudoviruses were examined to analyze their relationship with variant index. HIV-1 CRF01_AE Env gp140-specific total B-cell and plasma cell (CD19 + IgD - CD27 + CD38 + CD138 + ) responses were determined. In chronic-phase samples, significant correlation of variant index in all Env V1-V5 regions with Env-specific plasma cell responses was shown, and V1-V5 total variant index correlated stronger with Env-specific plasma cell as compared with total Env-specific B-cell responses. Env V5 variant index was significantly higher in chronic-phase cross-neutralizers of V5-polymorphic/VRC01-insensitive CRF01_AE Env. Results revealed the association between circulating Env-specific plasma cell responses and Env polymorphisms, implicating selective pressure on Env by plasma cell-derived antibodies and conversely suggests that Env-specific B-cell induction alone is insufficient for exerting Env selective pressure in HIV infection.

A stereotyped light chain may shape virus-specific B-cell receptors in HCV-dependent lymphoproliferative disorders

Hepatitis C virus (HCV) causes B-cell lymphoproliferative disorders (LPDs) expressing stereotyped B-cell receptors (BCRs) endowed with rheumatoid factor (RF) activity and putatively recognizing the HCV E2 protein. To further untangle the shaping and function of these BCRs, we analyzed immunoglobulin gene rearrangements of monoclonal B cells from 13 patients with HCV-associated LPDs and correlated their features with the clinical outcomes of antiviral therapy. While only two patients shared a stereotyped heavy-chain complementarity determining region 3 (CDR3) sequence, two kappa chain CDR3 stereotyped sequences accounted for 77% of BCRs. Light chains were enriched in sequences homologous to anti-HCV E2 antibodies compared with heavy chains (7/13 vs. 0/13; p = 0.005). Anti-HCV E2 homology was uniquely associated (7/7 vs. 0/6; p = 0.0006) with a stereotyped CDR3 sequence encoded by IGKV3-20/3D-20 gene(s) accounting for 54% of BCRs. An IGKV3-15/IGKJ1-encoded stereotyped sequence homologous to WA RF accounted for 23% of BCRs. LPDs expressing KCDR3s homologous to anti-HCV E2 antibodies responded more frequently to the eradication of HCV by antiviral therapy (6/6 vs. 1/6; p = 0.015). These findings, although limited by the small sample size, suggest that a stereotyped KCDR3 may predominantly shape anti-HCV specificity of BCRs, possibly providing a signature that may help identifying bona fide HCV-dependent LPDs.

Residual LCMV antigen in transiently CD4+ Tcell-depleted mice induces high levels of virus-specific antibodies but only limited B-cell memory.

Infection of C57BL/6 mice with lymphocytic choriomeningitis virus (LCMV) strain Armstrong (Arm) induces an acute infection with rapid virus clearance by CD8+ Tcells independently of CD4+ Tcell help. Residual viral antigen may, however, persist for a prolonged time. Here, we demonstrate that mice that had been transiently depleted of CD4+ Tcells during acute LCMV Arm infection generated high levels of virus-specific IgG antibodies (Ab) after viral clearance. Robust induction of LCMV-specific IgG after transient CD4+ Tcell depletion was dependent on Fcγ receptors but not on the complement receptors CD21/CD35. In contrast to the potent production of LCMV-specific IgG, the generation of LCMV-specific isotype-switched memory Bcells after transient CD4+ Tcell depletion was considerably reduced. Moreover, mice depleted of CD4+ Tcells during acute infection were strongly impaired in generating a secondary LCMV-specific Bcell response upon LCMV rechallenge. In conclusion, our data indicate that LCMV antigen depots after viral clearance were capable of inducing high levels of virus-specific IgG. They failed, however, to induce robust virus-specific Bcell memory revealing a previously unappreciated dichotomy of specific Ab production and memory cell formation after priming with residual antigen.

Live Attenuated Influenza Vaccine in Children Induces B-Cell Responses in Tonsils.

Background. Tonsils play a key role in eliciting immune responses against respiratory pathogens. Little is known about how tonsils contribute to the local immune response after intranasal vaccination. Here, we uniquely report the mucosal humoral responses in tonsils and saliva after intranasal live attenuated influenza vaccine (LAIV) vaccination in children.Methods. Blood, saliva, and tonsils samples were collected from 39 children before and after LAIV vaccination and from 16 age-matched, nonvaccinated controls. Serum antibody responses were determined by a hemagglutination inhibition (HI) assay. The salivary immunoglobulin A (IgA) level was measured by an enzyme-linked immunosorbent assay. Antibody-secreting cell (ASC) and memory B-cell (MBC) responses were enumerated in tonsils and blood.Results. Significant increases were observed in levels of serum antibodies and salivary IgA to influenza A(H3N2) and influenza B virus strains as early as 14 days after vaccination but not to influenza A(H1N1). Influenza virus–specific salivary IgA levels correlated with serum HI responses, making this a new possible indicator of vaccine immunogenicity in children. LAIV augmented influenza virus–specific B-cell responses in tonsils and blood. Tonsillar MBC responses correlated with systemic MBC and serological responses. Naive children showed significant increases in MBC counts after LAIV vaccination.Conclusions. This is the first study to demonstrate that LAIV elicits humoral B-cell responses in tonsils of young children. Furthermore, salivary IgA analysis represents an easy method for measuring immunogenicity after vaccination.

Hepatitis C virus (HCV)-specific memory B-cell responses in transiently and chronically infected HIV positive individuals

BackgroundAntibody responses to hepatitis C virus (HCV) occur delayed and overly decline after viral clearance indicating that the B-cell response to HCV is abnormal. Virus-specific memory B-cells have recently been found in infected individuals, but the viral exposure requirements for the generation of these cells is unknown. ObjectivesThe primary goal of this study was to quantify and compare the HCV-specific memory B-cell response between chronic and resolved HCV-infected individuals. A secondary goal was to examine if HIV-specific memory B-cell responses are maintained during HCV co-infection. Study designHCV core protein- and HIV-specific memory B-cell responses were examined in HIV/HCV-infected individuals treated 4–30 weeks after HCV diagnosis. Memory B-cell frequencies were compared between chronically and transiently infected individuals. ResultsChronically infected individuals had vigorous HCV-specific memory B-cell responses and antibodies, whereas subjects with transient viremia showed low or undetectable virus-specific B-cell responses. In addition, chronically HIV/HCV-infected subjects had robust HIV-specific memory B-cell responses. ConclusionsWhereas chronic HCV infection induces virus-specific antibodies and memory B-cells, transient infection in individuals with sustained viral response to therapy does not stimulate a durable HCV-specific B-cell response indicating that the formation of long-lived virus-specific B-cells is suppressed in the early phase of infection. This may contribute to the inability to spontaneously clear HCV infection.

Virus-Specific Antibody Secreting Cell, Memory B-cell, and Sero-Antibody Responses in the Human Influenza Challenge Model

Antibodies play a major role in the protection against influenza virus in human. However, the antibody level is usually short-lived and the cellular mechanisms underlying influenza virus-specific antibody response to acute infection remain unclear. We studied the kinetics and magnitude of influenza virus-specific B-cell and serum antibody responses in relation to virus replication during the course of influenza infection in healthy adult volunteers who were previously seronegative and experimentally infected with seasonal influenza H1N1 A/Brisbane/59/07 virus. Our data demonstrated a robust expansion of the virus-specific antibody-secreting cells (ASCs) and memory B cells in the peripheral blood, which correlated with both the throat viral load and the duration of viral shedding. The ASC response was obviously detected on day 7 post-infection when the virus was completely cleared from nasal samples, and serum hemagglutination-inhibition antibodies were still undetectable. On day 28 postinfection, influenza virus-specific B cells were further identified from the circulating compartment of isotype-switched B cells. Virus-specific ASCs could be the earliest marker of B-cell response to a new flu virus infection, such as H7N9 in humans.

HIV-1 gp41 envelope IgA is frequently elicited after transmission but has an initial short response half-life.

Prevention of HIV-1 transmission at mucosal surfaces will likely require durable pre-existing mucosal anti-HIV-1 antibodies (Abs). Defining the ontogeny, specificities and potentially protective nature of the initial mucosal virus-specific B-cell response will be critical for understanding how to induce protective Ab responses by vaccination. Genital fluids from patients within the earliest stages of acute HIV-1 infection (Fiebig I–VI) were examined for multiple anti-HIV specificities. Gp41 (but not gp120) Env immunoglobulin (Ig)A Abs were frequently elicited in both plasma and mucosal fluids within the first weeks of transmission. However, shortly after induction, these initial mucosal gp41 Env IgA Abs rapidly declined with a t1/2 of ∼2.7 days. B-cell-activating factor belonging to the TNF family (BAFF) was elevated immediately preceding the appearance of gp41 Abs, likely contributing to an initial T-independent Ab response. HIV-1 transmission frequently elicits mucosal HIV-1 envelope-specific IgA responses targeted to gp41 that have a short half-life.

Primary and Secondary B-Cell Responses to Pulmonary Virus Infection

Viruses form particulate structures possessing high-density B-cell epitopes and viral RNA/DNA, which are ligands for multiple Toll-like receptors (TLRs). B cells are able to sense these viral antigenic signatures through B-cell antigen receptors (BCRs) and TLRs, both of which synergistically shape the magnitude and quality of virus-specific B-cell responses. In many viruses, B-cell recognition of these virus signatures is often hampered by tissue tropisms toward nonlymphoid organs. However, ectopic localizations of B cells at virus replication sites facilitate the efficient recognition of intact virus particles. Following pulmonary infection by influenza virus, virus-specific B-cell responses occur in the tertiary lymphoid organs of lungs near the sites of virus replication as well as in the draining lymph nodes. Lungs then begin to support the germinal center response and the formation of niches for plasma cells and memory B cells, thus potentiating B-cell intrinsic recognition of virus particles at these sites. In this review, we discuss how the anatomical location and virus- sensing properties of B cells coordinate protective B-cell responses against pulmonary virus infection.

Cytokine profiles and long-term virus-specific antibodies following immunization of CBA mice with equine herpesvirus 1 and viral glycoprotein D.

Equine herpesvirus 1 (EHV-1)-specific antibody-secreting cells (ASC) isolated from the lung and spleen of mice at 12 months after immunization with attenuated EHV-1 KyA, heat-killed KyA, or recombinant viral glycoprotein D (rgD) assessed by ELISPOT showed a three- to fivefold increase in three immunoglobulin isotypes at 3 days post-challenge with pathogenic EHV-1 RacL11 as compared to control mice. ELISPOT assays demonstrated a high frequency of cells secreting proinflammatory tumor necrosis factor-alpha (TNF-alpha), interferon gamma (IFN-gamma), and interleukin 4 (IL-4) in the lungs in response to infection with KyA or RacL11 or immunization with rgD. Cytokine production elicited by EHV-1 KyA or RacL11 infection revealed similar frequencies of EHV-1-specific IFN-gamma and IL-4 spot forming cells in the mediastinal lymph nodes and spleen. However, KyA induced significantly greater amounts of IFN-gamma producing cells in the lungs than did RacL11. Intranasal immunization with KyA or rgD induced long-term immunity that provided protection against pathogenic EHV-1 challenge infection at 12 months post-immunization. Overall, the data indicate that immunization with infectious KyA or rgD induces significant levels of cytokines, virus-specific ASC in the lungs and spleen, and long-term virus specific B-cell responses.

Neutralizing antibodies associated with viremia control in a subset of individuals after treatment of acute human immunodeficiency virus type 1 infection.

Immediate treatment of acute human immunodeficiency virus type 1 (HIV-1) infection has been associated with subsequent control of viremia in a subset of patients after therapy cessation, but the immune responses contributing to control have not been fully defined. Here we examined neutralizing antibodies as a correlate of viremia control following treatment interruption in HIV-1-infected individuals in whom highly active antiretriviral therapy (HAART) was initiated during early seroconversion and who remained on therapy for 1 to 3 years. Immediately following treatment interruption, neutralizing antibodies were undetectable with T-cell-line adapted strains and the autologous primary HIV-1 isolate in seven of nine subjects. Env- and Gag-specific antibodies as measured by enzyme-linked immunosorbent assay were also low or undetectable at this time. Despite this apparent poor maturation of the virus-specific B-cell response during HAART, autologous neutralizing antibodies emerged rapidly and correlated with a spontaneous downregulation in rebound viremia following treatment interruption in three subjects. Control of rebound viremia was seen in other subjects in the absence of detectable neutralizing antibodies. The results indicate that virus-specific B-cell priming occurs despite the early institution of HAART, allowing rapid secondary neutralizing-antibody production following treatment interruption in a subset of individuals. Since early HAART limits viral diversification, we hypothesize that potent neutralizing-antibody responses to autologous virus are able to mature and that in some persons these responses contribute to the control of plasma viremia after treatment cessation.

Inhibition of immune responses against rabies virus by monoclonal antibodies directed against rabies virus antigens

Treatment of mice with a cocktail of murine anti-rabies monoclonal antibodies (mAb-C) interfered with the ability of these animals to mount a virus-neutralizing antibody response to rabies vaccine. Administered mAb-C did not affect the induction of rabies virus-specific T-helper cells. The magnitude of the inhibition of rabies virus-specific B-cell response was dependent on the concentration of the mAb-C and the duration of the mAb-mediated interference was inversely proportional to the biological half-life of the mAb. As long as the serum titres were above a critical threshold, the suppression could not be overcome even by multiple vaccinations. Since injection of mice with immunocomplexes consisting of inactivated rabies virus and mAb rendered the animals non-responsive to a subsequent vaccination with inactivated rabies virus, it is concluded that the mAb-induced suppression might be caused by the formation of antigen-antibody complexes which exert a negative signalling effect to premature B cells.