Nipah virus (NiV) is a pathogenic paramyxovirus that causes fatal encephalitis in humans. Two envelope glycoproteins, the attachment protein (G/RBP) and fusion protein (F), facilitate entry into host ...cells. Due to its vital role, NiV F presents an attractive target for developing vaccines and therapeutics. Several neutralization-sensitive epitopes on the NiV F apex have been described, however the antigenicity of most of the F protein's surface remains uncharacterized. Here, we immunize mice with prefusion-stabilized NiV F and isolate ten monoclonal antibodies that neutralize pseudotyped virus. Cryo-electron microscopy reveals eight neutralization-sensitive epitopes on NiV F, four of which have not previously been described. Novel sites span the lateral and basal faces of NiV F, expanding the known library of vulnerable epitopes. Seven of ten antibodies bind the Hendra virus (HeV) F protein. Multiple sequence alignment suggests that some of these newly identified neutralizing antibodies may also bind F proteins across the Henipavirus genus. This work identifies new epitopes as targets for therapeutics, provides a molecular basis for NiV neutralization, and lays a foundation for development of new cross-reactive antibodies targeting Henipavirus F proteins.
The development of a protective vaccine remains a top priority for the control of the HIV/AIDS pandemic. Here, we show that a messenger RNA (mRNA) vaccine co-expressing membrane-anchored HIV-1 ...envelope (Env) and simian immunodeficiency virus (SIV) Gag proteins to generate virus-like particles (VLPs) induces antibodies capable of broad neutralization and reduces the risk of infection in rhesus macaques. In mice, immunization with co-formulated env and gag mRNAs was superior to env mRNA alone in inducing neutralizing antibodies. Macaques were primed with a transmitted-founder clade-B env mRNA lacking the N276 glycan, followed by multiple booster immunizations with glycan-repaired autologous and subsequently bivalent heterologous envs (clades A and C). This regimen was highly immunogenic and elicited neutralizing antibodies against the most prevalent (tier-2) HIV-1 strains accompanied by robust anti-Env CD4
T cell responses. Vaccinated animals had a 79% per-exposure risk reduction upon repeated low-dose mucosal challenges with heterologous tier-2 simian-human immunodeficiency virus (SHIV AD8). Thus, the multiclade env-gag VLP mRNA platform represents a promising approach for the development of an HIV-1 vaccine.
CD4 T follicular helper (TFH) cells interact with and stimulate the generation of antigen-specific B cells. TFH cell interaction with B cells correlates with production of SIV-specific ...immunoglobulins. However, the fate of TFH cells and their participation in SIV-induced antibody production is not well understood. We investigated the phenotype, function, location, and molecular signature of TFH cells in rhesus macaques. Similar to their human counterparts, TFH cells in rhesus macaques represented a heterogeneous population with respect to cytokine function. In a highly differentiated subpopulation of TFH cells, characterized by CD150lo expression, production of Th1 cytokines was compromised while IL-4 production was augmented, and cells exhibited decreased survival, cycling, and trafficking capacity. TFH cells exhibited a distinct gene profile that was markedly altered by SIV infection. TFH cells were infected by SIV; yet, in some animals, these cells actually accumulated during chronic SIV infection. Generalized immune activation and increased IL-6 production helped drive TFH differentiation during SIV infection. Accumulation of TFH cells was associated with increased frequency of activated germinal center B cells and SIV-specific antibodies. Therefore, chronic SIV does not disturb the ability of TFH cells to help B cell maturation and production of SIV-specific immunoglobulins.
We present a technology to screen millions of B cells for natively paired human antibody repertoires. Libraries of natively paired, variable region heavy and light (V
:V
) amplicons are expressed in ...a yeast display platform that is optimized for human Fab surface expression. Using our method we identify HIV-1 broadly neutralizing antibodies (bNAbs) from an HIV-1 slow progressor and high-affinity neutralizing antibodies against Ebola virus glycoprotein and influenza hemagglutinin.
The quality assurance program presented here provides a means to maximize and maintain the performance of individual flow cytometers in a facility. To optimize performance, we recommend performing ...all three steps (optimization, calibration and standardization) in this program when a new flow cytometer is installed or whenever the flow cytometer's optical path is altered (e.g., lasers, filters or detectors are replaced). The complete process requires 3-4 h. On a more frequent basis, only a subset of these procedures need to be performed as a part of daily maintenance routines. The data generated can be tracked to monitor the instrument and determine whether service is needed. In addition, the data can provide a metric for whether repairs and upgrades have improved or harmed performance, and for future instrument-to-instrument comparisons. In sum, the procedures presented here represent an updated framework for optimizing, calibrating and standardizing a flow cytometer for daily use.
HIV‐2 is distinguished clinically and immunologically from HIV‐1 infection by delayed disease progression and maintenance of HIV‐specific CD4+ T cell help in most infected subjects. Thus, HIV‐2 ...provides a unique natural human model in which to investigate correlates of immune protection against HIV disease progression. Here, we report a detailed assessment of the HIV‐2‐specific CD4+ and CD8+ T cell response compared to HIV‐1, using polychromatic flow cytometry to assess the quality of the HIV‐specific T cell response by measuring IFN‐γ, IL‐2, TNF‐α, MIP‐1β, and CD107a mobilization (degranulation) simultaneously following Gag peptide stimulation. We find that HIV‐2‐specific CD4+ and CD8+ T cells are more polyfunctional that those specific for HIV‐1 and that polyfunctional HIV‐2‐specific T cells produce more IFN‐γ and TNF‐α on a per‐cell basis than monofunctional T cells. Polyfunctional HIV‐2‐specific CD4+ T cells were generally more differentiated and expressed CD57, while there was no association between function and phenotype in the CD8+ T cell fraction. Polyfunctional HIV‐specific T cell responses are a hallmark of non‐progressive HIV‐2 infection and may be related to good clinical outcome in this setting.
Targeted HIV cure strategies require definition of the mechanisms that maintain the virus. Here, we tracked HIV replication and the persistence of infected CD4 T cells in individuals with natural ...virologic control by sequencing viruses, T cell receptor genes, HIV integration sites, and cellular transcriptomes. Our results revealed three mechanisms of HIV persistence operating within distinct anatomic and functional compartments. In lymph node, we detected viruses with genetic and transcriptional attributes of active replication in both T follicular helper (TFH) cells and non-TFH memory cells. In blood, we detected inducible proviruses of archival origin among highly differentiated, clonally expanded cells. Linking the lymph node and blood was a small population of circulating cells harboring inducible proviruses of recent origin. Thus, HIV replication in lymphoid tissue, clonal expansion of infected cells, and recirculation of recently infected cells act together to maintain the virus in HIV controllers despite effective antiviral immunity.
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•In HIV controllers, both TFH and non-TFH lymph node CD4 T cells contain HIV•Lymph node viruses in both TFH and non-TFH have attributes of active replication•Rare, recently infected cells that produce virus upon stimulation circulate in blood•Archival proviruses predominant in clonally expanded blood cells can be inducible
HIV persistence in people who can spontaneously control the infection involves different mechanisms within distinct anatomic and functional compartments.
HIV-1 infection results in the progressive loss of CD4 T cells. In this study, we address how different pathogen-specific CD4 T cells are affected by HIV infection and the cellular parameters ...involved. We found striking differences in the depletion rates between CD4 T cells to two common opportunistic pathogens, cytomegalovirus (CMV) and Mycobacterium tuberculosis (MTB). CMV-specific CD4 T cells persisted after HIV infection, whereas MTB-specific CD4 T cells were depleted rapidly. CMV-specific CD4 T cells expressed a mature phenotype and produced very little IL-2, but large amounts of MIP-1β. In contrast, MTB-specific CD4 T cells were less mature, and most produced IL-2 but not MIP-1β. Staphylococcal enterotoxin B-stimulated IL-2-producing cells were more susceptible to HIV infection in vitro than MIP-1β-producing cells. Moreover, IL-2 production was associated with expression of CD25, and neutralization of IL-2 completely abrogated productive HIV infection in vitro. HIV DNA was found to be most abundant in IL-2-producing cells, and least abundant in MIP-1β-producing MTB-specific CD4 T cells from HIV-infected subjects with active tuberculosis. These data support the hypothesis that differences in function affect the susceptibility of pathogen-specific CD4 T cells to HIV infection and depletion in vivo, providing a potential mechanism to explain the rapid loss of MTB-specific CD4 T cells after HIV infection.
Pandemic live attenuated influenza vaccines (pLAIV) prime subjects for a robust neutralizing antibody response upon subsequent administration of a pandemic inactivated subunit vaccine (pISV). ...However, a difference was not detected in H5-specific memory B cells in the peripheral blood between pLAIV-primed and unprimed subjects prior to pISV boost. To investigate the mechanism underlying pLAIV priming, we vaccinated groups of 12 African green monkeys (AGMs) with H5N1 pISV or pLAIV alone or H5N1 pLAIV followed by pISV and examined immunity systemically and in local draining lymph nodes (LN). The AGM model recapitulated the serologic observations from clinical studies. Interestingly, H5N1 pLAIV induced robust germinal center B cell responses in the mediastinal LN (MLN). Subsequent boosting with H5N1 pISV drove increases in H5-specific B cells in the axillary LN, spleen, and circulation in H5N1 pLAIV-primed animals. Thus, H5N1 pLAIV primes localized B cell responses in the MLN that are recalled systemically following pISV boost. These data provide mechanistic insights for the generation of robust humoral responses via prime-boost vaccination.
We have previously shown that pandemic live attenuated influenza vaccines (pLAIV) prime for a rapid and robust antibody response on subsequent administration of inactivated subunit vaccine (pISV). This is observed even in individuals who had undetectable antibody (Ab) responses following the initial vaccination. To define the mechanistic basis of pLAIV priming, we turned to a nonhuman primate model and performed a detailed analysis of B cell responses in systemic and local lymphoid tissues following prime-boost vaccination with pLAIV and pISV. We show that the nonhuman primate model recapitulates the serologic observations from clinical studies. Further, we found that pLAIVs induced robust germinal center B cell responses in the mediastinal lymph node. Subsequent boosting with pISV in pLAIV-primed animals resulted in detection of B cells in the axillary lymph nodes, spleen, and peripheral blood. We demonstrate that intranasally administered pLAIV elicits a highly localized germinal center B cell response in the mediastinal lymph node that is rapidly recalled following pISV boost into germinal center reactions at numerous distant immune sites.
Vaccinia virus immunization provides lifelong protection against smallpox, but the mechanisms of this exquisite protection are unknown. We used polychromatic flow cytometry to characterize the ...functional and phenotypic profile of CD8(+) T cells induced by vaccinia virus immunization in a comparative vaccine trial of modified vaccinia virus Ankara (MVA) versus Dryvax immunization in which protection was assessed against subsequent Dryvax challenge. Vaccinia virus-specific CD8(+) T cells induced by both MVA and Dryvax were highly polyfunctional; they degranulated and produced interferon gamma, interleukin 2, macrophage inflammatory protein 1beta, and tumor necrosis factor alpha after antigenic stimulation. Responding CD8(+) T cells exhibited an unusual phenotype (CD45RO(-)CD27(intermediate)). The unique phenotype and high degree of polyfunctionality induced by vaccinia virus also extended to inserted HIV gene products of recombinant NYVAC. This quality of the CD8(+) T cell response may be at least partially responsible for the profound efficacy of these vaccines in protection against smallpox and serves as a benchmark against which other vaccines can be evaluated.
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