Cross-reactive Memory Research Articles

SARS-CoV-2 will constantly sweep its tracks: a vaccine containing CpG motifs in 'lasso' for the multi-faced virus.

During the current COVID-19 pandemic, the global ratio between the dead and the survivors is approximately 1 to 10, which has put humanity on high alert and provided strong motivation for the intensive search for vaccines and drugs. It is already clear that if we follow the most likely scenario, which is similar to that used to create seasonal influenza vaccines, then we will need to develop improved vaccine formulas every year to control the spread of the new, highly mutable coronavirus SARS-CoV-2. In this article, using well-known RNA viruses (HIV, influenza viruses, HCV) as examples, we consider the main successes and failures in creating primarily highly effective vaccines. The experience accumulated dealing with the biology of zoonotic RNA viruses suggests that the fight against COVID-19 will be difficult and lengthy. The most effective vaccines against SARS-CoV-2 will be those able to form highly effective memory cells for both humoral (memory B cells) and cellular (cross-reactive antiviral memory T cells) immunity. Unfortunately, RNA viruses constantly sweep their tracks and perhaps one of the most promising solutions in the fight against the COVID-19 pandemic is the creation of 'universal' vaccines based on conservative SARS-CoV-2 genome sequences (antigen-presenting) and unmethylated CpG dinucleotides (adjuvant) in the composition of the phosphorothioate backbone of single-stranded DNA oligonucleotides (ODN), which can be effective for long periods of use. Here, we propose a SARS-CoV-2 vaccine based on a lasso-like phosphorothioate oligonucleotide construction containing CpG motifs and the antigen-presenting unique ACG-containing genome sequence of SARS-CoV-2. We found that CpG dinucleotides are the most rare dinucleotides in the genomes of SARS-CoV-2 and other known human coronaviruses, and hypothesized that their higher frequency could be responsible for the unwanted increased lethality to the host, causing a ‘cytokine storm’ in people who overexpress cytokines through the activation of specific Toll-like receptors in a manner similar to TLR9-CpG ODN interactions. Interestingly, the virus strains sequenced in China (Wuhan) in February 2020 contained on average one CpG dinucleotide more in their genome than the later strains from the USA (New York) sequenced in May 2020. Obviously, during the first steps of the microevolution of SARS-CoV-2 in the human population, natural selection tends to select viral genomes containing fewer CpG motifs that do not trigger a strong innate immune response, so the infected person has moderate symptoms and spreads SARS-CoV-2 more readily. However, in our opinion, unmethylated CpG dinucleotides are also capable of preparing the host immune system for the coronavirus infection and should be present in SARS-CoV-2 vaccines as strong adjuvants.

Characterization of the Type-Specific and Cross-Reactive B-Cell Responses Elicited by a Live-Attenuated Tetravalent Dengue Vaccine.

Dengue is caused by 4 antigenically distinct serotypes of dengue virus (DENV1-4). Takeda's live attenuated tetravalent dengue vaccine (TAK-003) candidate is composed of an attenuated DENV2 and chimeric viruses containing prM/E of DENV1, 3 and 4 on the DENV2 backbone. The multicolor FluoroSpot (MCF) assay enables quantitation of serotype-specific and cross-reactive individual memory B cells (MBCs) secreting DENV-specific antibodies in a polyclonal mixture. Using the MCF assay, we determined the type-specific and cross-reactive MBC response in peripheral blood mononuclear cells collected pre- and postvaccination from 7 macaques and 15 randomly selected individuals who received TAK-003 (8 DENV seronegative and 7 DENV seropositive) in a phase 2 clinical trial in Singapore (DEN-205 study). Preexisting DENV-specific MBC responses were detected only in seropositive vaccine recipients at day 0. Following vaccination, both type-specific and cross-reactive MBCs to all 4 DENV serotypes were observed in all macaques and clinical trial participants. The proportion of type-specific MBCs was higher than cross-reactive MBCs and remained stable between day 30 and 360 post vaccination. These results demonstrate that, unlike primary or secondary natural DENV infection, tetravalent vaccination elicits tetravalent type-specific MBCs, and thus all 4 components of TAK-003 contribute to the DENV-specific MBC response following vaccination. NCT02425098.

Antibody Dependent Enhancement Due to Original Antigenic Sin and the Development of SARS.

Human coronavirus (HCoV) is one of the most common causes of respiratory tract infections throughout the world. Two phenomena observed so far in the development of the SARS-CoV-2 pandemic deserve further attention. First, the relative absence of clinical signs of infections in children, second, the early appearance of IgG in certain patients. From the point of view of immune system physiology, such an early rise of specific IgG is expected in secondary immune responses when memory to a cross-reactive antigen is present, usually from an earlier infection with a coronavirus. It is actually typical for the immune system to respond, to what it already knows, a phenomenon that has been observed in many infections with closely related viruses and has been termed “original antigenic sin.” The question then arises whether such cross-reactive antibodies are protective or not against the new virus. The worst scenario would be when such cross-reactive memory antibodies to related coronaviruses would not only be non-protective but even enhance infection and the clinical course. Such a phenomenon of antibody dependent enhancement (ADE) has already been described in several viral infections. Thus, the development of IgG against SARS-CoV-2 in the course of COVID-19 might not be a simple sign of viral clearance and developing protection against the virus. On the contrary, due to cross-reaction to related coronavirus strains from earlier infections, in certain patients IgG might enhance clinical progression due to ADE. The patient's viral history of coronavirus infection might be crucial to the development of the current infection with SARS-CoV-2. Furthermore, it poses a note of caution when treating COVID-19 patients with convalescent sera.

Mixed origins: HIV vaccine induced Env-specific antibodies arise from naive and cross-reactive memory B cells

Abstract The most potent and broad HIV envelope (Env)-specific antibodies (Abs) often when reverted to their inferred germline versions representing the naïve B cell receptor, usually fail to bind Env. This may suggest that the primary B cell population that responds to the initial Env exposure is not exclusively comprised of a naïve population, but also a pre-existing cross-reactive antigen-experienced B cell pool that expands following Env exposure. Previously we isolated 66 gp120 reactive mAbs from participants from HVTN105, a phase I trial testing AIDSVAX B/E (gp120 protein) combined with a DNA immunogen. In order to determine the origin of these mAb producing B cells, we used Miseq-based VH lineage tracking approach and identified several of these mAb lineages in peripheral blood prior to vaccination (pre-immune). Further, several of these pre-immune lineages also persist in the bone marrow ~8 months after the final vaccination, including within in the CD138+ long-lived plasma cell compartment. When tested by ELISA, pre-immune mAbs bound to HIV Env, with relatively lower ability than their post-vaccination forms, but showed higher reactivity than their germline form. The majority of the pre-immune lineage members were IgM, however IgG and IgA members were predominant prior to vaccination and the majority of the pre-immune lineage members exhibited somatic hypermutation. These results may indicate that the vaccine-induced Env-specific antibody lineages originated from a mixed ancestor population of naïve and cross-reactive memory cells.

Assessment of enhanced influenza vaccination finds thatFluAdconveys an advantage in mice and older adults.

ObjectivesEnhanced inactivated influenza vaccines (eIIV) aim to increase immunogenicity and protection compared with the widely used standard IIV (S‐IIV).MethodsWe tested four vaccines in parallel, FluZone high dose, FluBlok and FluAd versus S‐IIV in a randomised controlled trial of older adults and in a mouse infection model to assess immunogenicity, protection from lethal challenge and mechanisms of action.ResultsIn older adults, FluAd vaccination stimulated a superior antibody profile, including H3‐HA antibodies that were elevated for up to 1 year after vaccination, higher avidity H3HA IgG and larger HA stem IgG responses. In a mouse model, FluAd also elicited an earlier and larger induction of HA stem antibodies with increased germinal centre responses and upregulation and long‐term expression of B‐cell switch transcription factors. Long‐term cross‐reactive memory responses were sustained by FluAd following lethal heterosubtypic influenza challenge, with reduced lung damage and viral loads, coinciding with increased T‐ and B‐cell recall. Advantages were also noted for the high‐dose FluZone vaccine in both humans and mice.ConclusionThe early, broadly reactive and long‐lived antibody response of FluAd indicates a potential advantage of this vaccine, particularly in years when there is a mismatch between the vaccine strain and the circulating strain of influenza viruses.

CTL-mediated immunotherapy can suppress SHIV rebound in ART-free macaques

A major barrier to human immunodeficiency virus (HIV) cure is the existence of viral reservoirs that lead to viral rebound following discontinuation of antiretroviral therapy (ART). We postulate that enhancing cytotoxic T lymphocytes (CTL) targeting conserved envelope (Env) regions can eliminate HIV infected cells in latency. Here, we evaluate the use of adoptively transferred HIV vaccine-induced subtype C Env-specific CTLs in a macaque subtype B simian-human immunodeficiency virus (SHIV) model to determine whether plasma viremia can be controlled after ART interruption. We demonstrate that adoptive cellular therapy (ACT) using autologous Env-specific T cells augmented by therapeutic vaccination can suppress ART-free viral rebound in the SHIV model. Furthermore, phenotypic and functional characterization of adoptively transferred cells in ACT-responsive and nonresponsive animals support a critical role for cross-reactive central memory T cells in viremia control. Our study offers an approach to potentiate immunological suppression of HIV in the absence of antiviral drugs.

Mouse Models of Heterologous Flavivirus Immunity: A Role for Cross-Reactive T Cells.

Most of the world is at risk of being infected with a flavivirus such as dengue virus, West Nile virus, yellow fever virus, Japanese encephalitis virus, tick-borne encephalitis virus, and Zika virus, significantly impacting millions of lives. Importantly, many of these genetically similar viruses co-circulate within the same geographic regions, making it likely for individuals living in areas of high flavivirus endemicity to be infected with multiple flaviviruses during their lifetime. Following a flavivirus infection, a robust virus-specific T cell response is generated and the memory recall of this response has been demonstrated to provide long-lasting immunity, protecting against reinfection with the same pathogen. However, multiple studies have shown that this flavivirus specific T cell response can be cross-reactive and active during heterologous flavivirus infection, leading to the question: How does immunity to one flavivirus shape immunity to the next, and how does this impact disease? It has been proposed that in some cases unfavorable disease outcomes may be caused by lower avidity cross-reactive memory T cells generated during a primary flavivirus infection that preferentially expand during a secondary heterologous infection and function sub optimally against the new pathogen. While in other cases, these cross-reactive cells still have the potential to facilitate cross-protection. In this review, we focus on cross-reactive T cell responses to flaviviruses and the concepts and consequences of T cell cross-reactivity, with particular emphasis linking data generated using murine models to our new understanding of disease outcomes following heterologous flavivirus infection.

Clonal selection of cross-reactive memory B cells dominates recall responses against heterologous flaviviruses without a requirement for secondary affinity maturation

Abstract Members of the flaviviridae family include a number of globally relevant pathogens such as West Nile (WNV), Japanese Encephalitis (JEV), Dengue, and Zika viruses. Upon clearance of a primary flavivirus infection, both neutralizing and non-neutralizing antibody specificities are generated and maintained. These antibodies can play protective or pathogenic roles after subsequent infection with heterologous flaviviruses. To define the cells capable of responding to secondary heterologous infections, we utilized a WNV and subsequent JEV vaccination model. Using tetramer reagents directed at the potently neutralizing lateral ridge epitope on envelope protein domain III (DIII) of WNV. We found that memory B cells were more antigenically diverse and cross-reactive than were long-lived plasma cells. To determine how this memory B cell diversity is generated and subsequently utilized, we generated a mouse model in which deletion of activation induced cytidine deaminase (AID) is temporally driven by hCD20-CreERT2. Deleting AID during ongoing germinal center reactions against WNV did not affect the antigen specificity or quantity of memory B cells or bone marrow plasma cells. Deletion of AID during the memory phase following WNV vaccination did not alter the cellular response to JEV compared to wild type mice. Thus, cross-reactive B cells selectively enter the memory B cell compartment and are excluded from the long-lived plasma cell compartment through a B cell receptor affinity maturation-independent mechanism. Analysis of germline-reverted monoclonal antibodies derived from DIII-specific memory B cells and long-lived plasma cells suggests that the fate of a B cell is imprinted at the naive state.

The Role of Pre-existing Cross-Reactive Central Memory CD4 T-Cells in Vaccination With Previously Unseen Influenza Strains.

Influenza vaccination is a common approach to prevent seasonal and pandemic influenza. Pre-existing antibodies against close viral strains might impair antibody formation against previously unseen strains–a process called original antigenic sin. The role of this pre-existing cellular immunity in this process is, despite some hints from animal models, not clear. Here, we analyzed cellular and humoral immunity in healthy individuals before and after vaccination with seasonal influenza vaccine. Based on influenza-specific hemagglutination inhibiting (HI) titers, vaccinees were grouped into HI-negative and -positive cohorts followed by in-depth cytometric and TCR repertoire analysis. Both serological groups revealed cross-reactive T-cell memory to the vaccine strains at baseline that gave rise to the majority of vaccine-specific T-cells post vaccination. On the contrary, very limited number of vaccine-specific T-cell clones was recruited from the naive pool. Furthermore, baseline quantity of vaccine-specific central memory helper T-cells and clonotype richness of this population directly correlated with the vaccination efficacy. Our findings suggest that the deliberate recruitment of pre-existing cross-reactive cellular memory might help to improve vaccination outcome.

Role of IL-10 in inhibiting protective immune responses against infection with heterologous Plasmodium parasites

Malaria is induced by infection with Plasmodium parasites, which are genetically diverse, and the immune response to Plasmodium infection has both allele-specific and cross-reactive components. To determine the role of the cross-reactive immune response in the protection and disease manifestation in heterologous Plasmodium infection, we used infection models of P. chabaudi chabaudi (Pcc) and P. berghei ANKA (PbA). CD4+ T cells primed with Pcc infection exhibited strong cross-reactivity to PbA antigens. We infected C57BL/6 mice with Pcc and subsequently treated them with an anti-Plasmodium drug. The Pcc-primed mice exhibited reduced parasitemia and showed no signs of experimental cerebral malaria after infection with PbA. CD4+ T cells from the Pcc-primed mice produced high levels of IFN-γ and IL-10 in response to PbA early after PbA infection. The blockade of IL-10 signaling with anti-IL-10 receptor antibody increased the proportion of activated CD4+ and γδ T cells and the IFN-γ production by CD4+ T cells in response to PbA antigens, while markedly reducing the levels of parasitemia. In contrast, IL-10 blockade did not have a significant effect on parasitemia levels in unprimed mice after PbA infection. These data suggest a potent regulatory role of IL-10 in the cross-reactive memory response to the infection with heterologous Plasmodium parasites leading to the inhibition of the protective immunity and pathogenesis.

Distinguishing naive‐ from memory‐derived human B cells during acute responses

ObjectivesA fundamental question in influenza research is whether antibody titre decline upon successive exposure to variant strains is consequent to recall of cross‐reactive memory B cells that competitively inhibit naive B‐cell responses. In connection, it is not clear whether naive and memory B cells remain phenotypically distinct acutely after activation such that they may be distinguished ex vivo.MethodsHere, we first compared the capacity of anti‐Ig and Toll‐like‐receptor (TLR) 7/8 and TLR9 agonists (R848 and CpG) to augment human B‐cell differentiation induced by IL‐21 and sCD40L. The conditions that induced optimal differentiation were then used to compare the post‐activation phenotype of sort‐purified naive and memory B‐cell subsets by FACS and antibody‐secreting cell (ASC) ELISPOT.ResultsSort‐purified naive and memory B cells underwent robust plasmablast and ASC formation when stimulated with R848, but not CpG, and co‐cultured with monocytes. This coincided with increased IL‐1β and IL‐6 production when B cells were co‐cultured with monocytes and stimulated with R848, but not CpG. Naive B cells underwent equivalent ASC generation, but exhibited less class‐switch and modulation of CD27, CD38 and CD20 expression than memory B cells after stimulation with R848 and monocytes for 6 days.ConclusionStimulation with R848, IL‐21 and sCD40L in the presence of monocytes induces robust differentiation and ASC generation from both naive and memory B‐cells. However, naive and memory B cells retain key phenotypic differences after activation that may facilitate ex vivo discrimination and better characterisation of acute responses to variant antigens.

Multiplexed FluoroSpot for the Analysis of Dengue Virus- and Zika Virus-Specific and Cross-Reactive Memory B Cells.

Dengue virus (DENV) and Zika virus (ZIKV) are mosquito-borne pathogens that have a significant impact on human health. Immune sera, mAbs, and memory B cells (MBCs) isolated from patients infected with one DENV type can be cross-reactive with the other three DENV serotypes and even more distantly related flaviviruses such as ZIKV. Conventional ELISPOTs effectively measure Ab-secreting B cells but because they are limited to the assessment of a single Ag at a time, it is challenging to distinguish serotype-specific and cross-reactive MBCs in the same well. We developed a novel multifunction FluoroSpot assay using fluorescently labeled DENV and ZIKV (FLVs) that measures the cross-reactivity of Abs secreted by single B cells. Conjugation efficiency and recognition of FLVs by virus-specific Abs were confirmed by flow cytometry. Using a panel of DENV immune, ZIKV immune, and naive PBMC, FLVs were able to simultaneously detect DENV serotype-specific, ZIKV-specific, DENV serotype cross-reactive, and DENV/ZIKV cross-reactive Abs secreted by individual MBCs. Our findings indicate that the FLVs are sensitive and specific tools to detect specific and cross-reactive MBCs. These reagents will allow the assessment of the breadth as well as the durability of DENV/ZIKV B cell responses following vaccination or natural infection. This novel approach using FLVs in a FluoroSpot assay can be applied to other diseases such as influenza in which prior immunity with homosubtype- or heterosubtype-specific MBCs may influence subsequent infections.

Virtual memory cells make a major contribution to the response of aged influenza-na\xefve mice to influenza virus infection

BackgroundA diverse repertoire of naïve T cells is thought to be essential for a robust response to new infections. However, a key aspect of aging of the T cell compartment is a decline in numbers and diversity of peripheral naïve T cells. We have hypothesized that the age-related decline in naïve T cells forces the immune system to respond to new infections using cross-reactive memory T cells generated to previous infections that dominate the aged peripheral T cell repertoire.ResultsHere we confirm that the CD8 T cell response of aged, influenza-naïve mice to primary infection with influenza virus is dominated by T cells that derive from the memory T cell pool. These cells exhibit the phenotypic characteristics of virtual memory cells rather than true memory cells. Furthermore, we find that the repertoire of responding CD8 T cells is constrained compared with that of young mice, and differs significantly between individual aged mice. After infection, these virtual memory CD8 T cells effectively develop into granzyme-producing effector cells, and clear virus with kinetics comparable to naïve CD8 T cells from young mice.ConclusionsThe response of aged, influenza-naive mice to a new influenza infection is mediated largely by memory CD8 T cells. However, unexpectedly, they have the phenotype of VM cells. In response to de novo influenza virus infection, the VM cells develop into granzyme-producing effector cells and clear virus with comparable kinetics to young CD8 T cells.

Flavivirus serocomplex cross-reactive immunity is protective by activating heterologous memory CD4 T cells.

How previous immunity influences immune memory recall and protection against related flaviviruses is largely unknown, yet encounter with multiple flaviviruses in a lifetime is increasingly likely. Using sequential challenges with dengue virus (DENV), yellow fever virus (YFV), and Japanese encephalitis virus (JEV), we induced cross-reactive cellular and humoral immunity among flaviviruses from differing serocomplexes. Antibodies against JEV enhanced DENV replication; however, JEV immunity was protective in vivo during secondary DENV1 infection, promoting rapid gains in antibody avidity. Mechanistically, JEV immunity activated dendritic cells and effector memory T cells, which developed a T follicular helper cell phenotype in draining lymph nodes upon secondary DENV1 infection. We identified cross-reactive epitopes that promote recall from a pool of flavivirus serocomplex cross-reactive memory CD4 T cells and confirmed that a similar serocomplex cross-reactive immunity occurs in humans. These results show that sequential immunizations for flaviviruses sharing CD4 epitopes should promote protection during a subsequent heterologous infection.

Simultaneous Presence of Non- and Highly Mutated Keyhole Limpet Hemocyanin (KLH)-Specific Plasmablasts Early after Primary KLH Immunization Suggests Cross-Reactive Memory B Cell Activation.

There are currently limited insights into the progression of human primary humoral immunity despite numerous studies in experimental models. In this study, we analyzed a primary and related secondary parenteral keyhole limpet hemocyanin (KLH) immunization in five human adults. The primary challenge elicited discordant KLH-specific serum and blood effector B cell responses (i.e., dominant serum KLH-specific IgG and IgM levels versus dominant KLH-specific IgA plasmablast frequencies). Single-cell IgH sequencing revealed early appearance of highly (>15 mutations) mutated circulating KLH-specific plasmablasts 2 wk after primary KLH immunization, with simultaneous KLH-specific plasmablasts carrying non- and low-mutated IgH sequences. The data suggest that the highly mutated cells might originate from cross-reactive memory B cells (mBCs) rather than from the naive B cell repertoire, consistent with previous reported mutation rates and the presence of KLH-reactive mBCs in naive vaccinees prior to immunization. Whereas upon secondary immunization, serum Ab response kinetics and plasmablast mutation loads suggested the exclusive reactivation of KLH-specific mBCs, we, however, detected only little clonal overlap between the peripheral KLH-specific secondary plasmablast IgH repertoire and the primary plasmablast and mBC repertoire, respectively. Our data provide novel mechanistic insights into human humoral immune responses and suggest that primary KLH immunization recruits both naive B cells and cross-reactive mBCs, whereas secondary challenge exclusively recruits from a memory repertoire, with little clonal overlap with the primary response.

Inability To Detect Cross-Reactive Memory T Cells Challenges the Frequency of Heterologous Immunity among Common Viruses.

Human memory T cells that cross-react with epitopes from unrelated viruses can potentially modulate immune responses to subsequent infections by a phenomenon termed heterologous immunity. However, it is unclear whether similarities in structure rather than sequence underpin heterologous T cell cross-reactivity. In this study, we aimed to explore the mechanism of heterologous immunity involving immunodominant epitopes derived from common viruses restricted to high-frequency HLA allotypes (HLA-A*02:01, -B*07:02, and -B*08:01). We examined EBV-specific memory T cells for their ability to cross-react with CMV or influenza A virus-derived epitopes. Following T cell immunoassays to determine phenotype and function, complemented with biophysical and structural investigations of peptide/HLA complexes, we did not detect cross-reactivity of EBV-specific memory T cells toward either CMV or influenza A virus epitopes presented by any of the selected HLA allomorphs. Thus, despite the ubiquitous nature of these human viruses and the dominant immune response directed toward the selected epitopes, heterologous virus-specific T cell cross-reactivity was not detected. This suggests that either heterologous immunity is not as common as previously reported, or that it requires a very specific biological context to develop and be clinically relevant.

Broad cross-reactive IgG responses elicited by adjuvanted vaccination with recombinant influenza hemagglutinin (rHA) in ferrets and mice.

Annual immunization against influenza virus is a large international public health effort. Accumulating evidence suggests that antibody mediated cross-reactive immunity against influenza hemagglutinin (HA) strongly correlates with long-lasting cross-protection against influenza virus strains that differ from the primary infection or vaccination strain. However, the optimal strategies for achieving highly cross-reactive antibodies to the influenza virus HA have not yet to be defined. In the current study, using Luminex-based mPlex-Flu assay, developed by our laboratory, to quantitatively measure influenza specific IgG antibody mediated cross-reactivity, we found that prime-boost-boost vaccination of ferrets with rHA proteins admixed with adjuvant elicited higher magnitude and broader cross-reactive antibody responses than that induced by actual influenza viral infection, and this cross-reactive response likely correlated with increased anti-stalk reactive antibodies. We observed a similar phenomenon in mice receiving three sequential vaccinations with rHA proteins from either A/California/07/2009 (H1N1) or A/Hong Kong/1/1968 (H3N2) viruses admixed with Addavax, an MF59-like adjuvant. Using this same mouse vaccination model, we determined that Addavax plays a more significant role in the initial priming event than in subsequent boosts. We also characterized the generation of cross-reactive antibody secreting cells (ASCs) and memory B cells (MBCs) when comparing vaccination to viral infection. We have also found that adjuvant plays a critical role in the generation of long-lived ASCs and MBCs cross-reactive to influenza viruses as a result of vaccination with rHA of influenza virus, and the observed increase in stalk-reactive antibodies likely contributes to this IgG mediated broad cross-reactivity.

Severity of Acute Infectious Mononucleosis Correlates with Cross-Reactive Influenza CD8 T-Cell Receptor Repertoires.

ABSTRACTFifty years after the discovery of Epstein-Barr virus (EBV), it remains unclear how primary infection with this virus leads to massive CD8 T-cell expansion and acute infectious mononucleosis (AIM) in young adults. AIM can vary greatly in severity, from a mild transient influenza-like illness to a prolonged severe syndrome. We questioned whether expansion of a unique HLA-A2.01-restricted, cross-reactive CD8 T-cell response between influenza virus A-M158 (IAV-M1) and EBV BMLF1280 (EBV-BM) could modulate the immune response to EBV and play a role in determining the severity of AIM in 32 college students. Only ex vivo total IAV-M1 and IAV-M1+EBV-BM cross-reactive tetramer+ frequencies directly correlated with AIM severity and were predictive of severe disease. Expansion of specific cross-reactive memory IAV-M1 T-cell receptor (TCR) Vβ repertoires correlated with levels of disease severity. There were unique profiles of qualitatively different functional responses in the cross-reactive and EBV-specific CD8 T-cell responses in each of the three groups studied, severe-AIM patients, mild-AIM patients, and seropositive persistently EBV-infected healthy donors, that may result from differences in TCR repertoire use. IAV-M1 tetramer+ cells were functionally cross-reactive in short-term cultures, were associated with the highest disease severity in AIM, and displayed enhanced production of gamma interferon, a cytokine that greatly amplifies immune responses, thus frequently contributing to induction of immunopathology. Altogether, these data link heterologous immunity via CD8 T-cell cross-reactivity to CD8 T-cell repertoire selection, function, and resultant disease severity in a common and important human infection. In particular, it highlights for the first time a direct link between the TCR repertoire with pathogenesis and the diversity of outcomes upon pathogen encounter.

Zika virus activates de novo and cross-reactive memory B cell responses in dengue-experienced donors.

Zika virus (ZIKV) shares a high degree of homology with dengue virus (DENV), suggesting that preexisting immunity to DENV could affect immune responses to ZIKV. We have tracked the evolution of ZIKV-induced B cell responses in three DENV-experienced donors. The acute antibody (plasmablast) responses were characterized by relatively high somatic hypermutation and a bias toward DENV binding and neutralization, implying the early activation of DENV clones. A DENV-naïve donor in contrast showed a classical primary plasmablast response. Five months after infection, the DENV-experienced donors developed potent type-specific ZIKV neutralizing antibody responses in addition to DENV cross-reactive responses. Because cross-reactive responses were poorly neutralizing and associated with enhanced ZIKV infection in vitro, preexisting DENV immunity could negatively affect protective antibody responses to ZIKV. The observed effects are epitope-dependent, suggesting that a ZIKV vaccine should be carefully designed for DENV-seropositive populations.

Unique influenza A cross-reactive memory CD8 T-cell receptor repertoire has a potential to protect against EBV seroconversion

Unique influenza A cross-reactive memory CD8 T-cell receptor repertoire has a potential to protect against EBV seroconversion