The latent viral reservoir is the critical barrier for the development of a cure for HIV-1 infection. Previous studies have shown direct antiviral activity of potent HIV-1 Env-specific broadly ...neutralizing antibodies (bNAbs) administered when antiretroviral therapy (ART) was discontinued, but it remains unclear whether bNAbs can target the viral reservoir during ART. Here we show that administration of the V3 glycan-dependent bNAb PGT121 together with the Toll-like receptor 7 (TLR7) agonist vesatolimod (GS-9620) during ART delayed viral rebound following discontinuation of ART in simian-human immunodeficiency virus (SHIV)-SF162P3-infected rhesus monkeys in which ART was initiated during early acute infection. Moreover, in the subset of monkeys that were treated with both PGT121 and GS-9620 and that did not show viral rebound after discontinuation of ART, adoptive transfer studies and CD8-depletion studies also did not reveal virus. These data demonstrate the potential of bNAb administration together with innate immune stimulation as a possible strategy for targeting the viral reservoir.
Pseudotyped viruses are valuable tools for studying virulent or lethal viral pathogens that need to be handled in biosafety level 3 (BSL-3) or higher facilities. With the explosive spread of the ...coronavirus disease 2019 (COVID-19) pandemic, the establishment of a BSL-2 adapted SARS-CoV-2 pseudovirus neutralization assay is needed to facilitate the development of countermeasures. Here we describe an approach to generate a single-round lentiviral vector-based SARS-CoV-2 pseudovirus, which produced a signal more than 2 logs above background. Specifically, a SARS-CoV-2 spike variant with a cytoplasmic tail deletion of 13 amino acids, termed SΔCT13, conferred enhanced spike incorporation into pseudovirions and increased viral entry into cells as compared with full-length spike (S). We further compared S and SΔCT13 in terms of their sensitivity to vaccine sera, purified convalescent IgG, hACE2-mIgG, and the virus entry inhibitor BafA1. We developed a SΔCT13-based pseudovirus neutralization assay and defined key assay characteristics, including linearity, limit of detection, and intra- and intermediate-assay precision. Our data demonstrate that the SΔCT13-based pseudovirus shows enhanced infectivity in target cells, which will facilitate the assessment of humoral immunity to SARS-CoV-2 infection, antibody therapeutics, and vaccination. This pseudovirus neutralization assay can also be readily adapted to SARS-CoV-2 variants that emerge.
SARS-CoV-2 is the etiologic agent of the COVID-19 pandemic. The development of a high throughput pseudovirus neutralization assay is critical for the development of vaccines and immune-based therapeutics. In this study, we show that deletion of the cytoplasmic tail of the SARS-CoV-2 spike leads to pseudoviruses with enhanced infectivity. This SΔCT13-based pseudovirus neutralization assay should be broadly useful for the field.
Zika virus (ZIKV) is a flavivirus that is responsible for the current epidemic in Brazil and the Americas. ZIKV has been causally associated with fetal microcephaly, intrauterine growth restriction, ...and other birth defects in both humans and mice. The rapid development of a safe and effective ZIKV vaccine is a global health priority, but very little is currently known about ZIKV immunology and mechanisms of immune protection. Here we show that a single immunization with a plasmid DNA vaccine or a purified inactivated virus vaccine provides complete protection in susceptible mice against challenge with a strain of ZIKV involved in the outbreak in northeast Brazil. This ZIKV strain has recently been shown to cross the placenta and to induce fetal microcephaly and other congenital malformations in mice. We produced DNA vaccines expressing ZIKV pre-membrane and envelope (prM-Env), as well as a series of deletion mutants. The prM-Env DNA vaccine, but not the deletion mutants, afforded complete protection against ZIKV, as measured by absence of detectable viraemia following challenge, and protective efficacy correlated with Env-specific antibody titers. Adoptive transfer of purified IgG from vaccinated mice conferred passive protection, and depletion of CD4 and CD8 T lymphocytes in vaccinated mice did not abrogate this protection. These data demonstrate that protection against ZIKV challenge can be achieved by single-shot subunit and inactivated virus vaccines in mice and that Env-specific antibody titers represent key immunologic correlates of protection. Our findings suggest that the development of a ZIKV vaccine for humans is likely to be achievable.
Human immunodeficiency virus type 1 (HIV-1)-specific monoclonal antibodies with extraordinary potency and breadth have recently been described. In humanized mice, combinations of monoclonal ...antibodies have been shown to suppress viraemia, but the therapeutic potential of these monoclonal antibodies has not yet been evaluated in primates with an intact immune system. Here we show that administration of a cocktail of HIV-1-specific monoclonal antibodies, as well as the single glycan-dependent monoclonal antibody PGT121, resulted in a rapid and precipitous decline of plasma viraemia to undetectable levels in rhesus monkeys chronically infected with the pathogenic simian-human immunodeficiency virus SHIV-SF162P3. A single monoclonal antibody infusion afforded up to a 3.1 log decline of plasma viral RNA in 7 days and also reduced proviral DNA in peripheral blood, gastrointestinal mucosa and lymph nodes without the development of viral resistance. Moreover, after monoclonal antibody administration, host Gag-specific T-lymphocyte responses showed improved functionality. Virus rebounded in most animals after a median of 56 days when serum monoclonal antibody titres had declined to undetectable levels, although, notably, a subset of animals maintained long-term virological control in the absence of further monoclonal antibody infusions. These data demonstrate a profound therapeutic effect of potent neutralizing HIV-1-specific monoclonal antibodies in SHIV-infected rhesus monkeys as well as an impact on host immune responses. Our findings strongly encourage the investigation of monoclonal antibody therapy for HIV-1 in humans.
A key challenge for the development of a cure to HIV-1 infection is the persistent viral reservoir established during early infection. Previous studies using Toll-like receptor 7 (TLR7) agonists and ...broadly neutralizing antibodies (bNAbs) have shown delay or prevention of viral rebound following antiretroviral therapy (ART) discontinuation in simian-human immunodeficiency virus (SHIV)-infected rhesus macaques. In these prior studies, ART was initiated early during acute infection, which limited the size and diversity of the viral reservoir. Here we evaluated in SHIV-infected rhesus macaques that did not initiate ART until 1 year into chronic infection whether the TLR7 agonist vesatolimod in combination with the bNAb PGT121, formatted either as a human IgG1, an effector enhanced IgG1, or an anti-CD3 bispecific antibody, would delay or prevent viral rebound following ART discontinuation. We found that all 3 antibody formats in combination with vesatolimod were able to prevent viral rebound following ART discontinuation in a subset of animals. These data indicate that a TLR7 agonist combined with antibodies may be a promising strategy to achieve long-term ART-free HIV remission in humans.
The ongoing pandemic of coronavirus disease 2019 (COVID-19), which is caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), is a major threat to global health
and the medical ...countermeasures available so far are limited
. Moreover, we currently lack a thorough understanding of the mechanisms of humoral immunity to SARS-CoV-2
. Here we analyse a large panel of human monoclonal antibodies that target the spike (S) glycoprotein
, and identify several that exhibit potent neutralizing activity and fully block the receptor-binding domain of the S protein (S
) from interacting with human angiotensin-converting enzyme 2 (ACE2). Using competition-binding, structural and functional studies, we show that the monoclonal antibodies can be clustered into classes that recognize distinct epitopes on the S
, as well as distinct conformational states of the S trimer. Two potently neutralizing monoclonal antibodies, COV2-2196 and COV2-2130, which recognize non-overlapping sites, bound simultaneously to the S protein and neutralized wild-type SARS-CoV-2 virus in a synergistic manner. In two mouse models of SARS-CoV-2 infection, passive transfer of COV2-2196, COV2-2130 or a combination of both of these antibodies protected mice from weight loss and reduced the viral burden and levels of inflammation in the lungs. In addition, passive transfer of either of two of the most potent ACE2-blocking monoclonal antibodies (COV2-2196 or COV2-2381) as monotherapy protected rhesus macaques from SARS-CoV-2 infection. These results identify protective epitopes on the S
and provide a structure-based framework for rational vaccine design and the selection of robust immunotherapeutic agents.
Passive administration of HIV neutralizing antibodies (nAbs) can protect macaques from hard-to-neutralize (tier 2) chimeric simian-human immunodeficiency virus (SHIV) challenge. However, conditions ...for nAb-mediated protection after vaccination have not been established. Here, we selected groups of 6 rhesus macaques with either high or low serum nAb titers from a total of 78 animals immunized with recombinant native-like (SOSIP) Env trimers. Repeat intrarectal challenge with homologous tier 2 SHIVBG505 led to rapid infection in unimmunized and low-titer animals. High-titer animals, however, demonstrated protection that was gradually lost as nAb titers waned over time. An autologous serum ID50 nAb titer of ∼1:500 afforded more than 90% protection from medium-dose SHIV infection. In contrast, antibody-dependent cellular cytotoxicity and T cell activity did not correlate with protection. Therefore, Env protein-based vaccination strategies can protect against hard-to-neutralize SHIV challenge in rhesus macaques by inducing tier 2 nAbs, provided appropriate neutralizing titers can be reached and maintained.
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•HIV Env trimer immunization protects from autologous tier 2 challenge in macaques•Neutralizing antibody (nAb) titers correlate with protection and peak viremia•T cell and ADCC functions do not correlate with protection•nAb titers of ∼1:500 (pseudovirus)/∼1:30 (live virus) required for ∼90% protection
Vaccine-induced immunity to HIV is a major research focus, but relevant correlates of protection remain controversial. Here, Pauthner et al. study protection from hard-to-neutralize SHIVBG505 challenge after immunization with native-like BG505 Envelope trimers in nonhuman primates and identify neutralizing antibodies, but not T cell or ADCC activity, as correlates of protection.
Preclinical studies of viral vector–based HIV-1 vaccine candidates have previously shown partial protection against neutralization-resistant virus challenges in rhesus monkeys. In this study, we ...evaluated the protective efficacy of adenovirus serotype 26 (Ad26) vector priming followed by purified envelope (Env) glycoprotein boosting. Rhesus monkeys primed with Ad26 vectors expressing SIVsmE543 Env, Gag, and Pol and boosted with AS01B-adjuvanted SIVmac32H Env gp140 demonstrated complete protection in 50% of vaccinated animals against a series of repeated, heterologous, intrarectal SIVmac251 challenges that infected all controls. Protective efficacy correlated with the functionality of Env-specific antibody responses. Comparable protection was also observed with a similar Ad/Env vaccine against repeated, heterologous, intrarectal SHIV-SF162P3 challenges. These data demonstrate robust protection by Ad/Env vaccines against acquisition of neutralization-resistant virus challenges in rhesus monkeys.
IMPORTANCE: Control of the global COVID-19 pandemic will require the development and deployment of safe and effective vaccines. OBJECTIVE: To evaluate the immunogenicity of the Ad26.COV2.S vaccine ...(Janssen/Johnson & Johnson) in humans, including the kinetics, magnitude, and phenotype of SARS-CoV-2 spike-specific humoral and cellular immune responses. DESIGN, SETTING, AND PARTICIPANTS: Twenty-five participants were enrolled from July 29, 2020, to August 7, 2020, and the follow-up for this day 71 interim analysis was completed on October 3, 2020; follow-up to assess durability will continue for 2 years. This study was conducted at a single clinical site in Boston, Massachusetts, as part of a randomized, double-blind, placebo-controlled phase 1 clinical trial of Ad26.COV2.S. INTERVENTIONS: Participants were randomized to receive 1 or 2 intramuscular injections with 5 × 1010 viral particles or 1 × 1011 viral particles of Ad26.COV2.S vaccine or placebo administered on day 1 and day 57 (5 participants in each group). MAIN OUTCOMES AND MEASURES: Humoral immune responses included binding and neutralizing antibody responses at multiple time points following immunization. Cellular immune responses included immunospot-based and intracellular cytokine staining assays to measure T-cell responses. RESULTS: Twenty-five participants were randomized (median age, 42; age range, 22-52; 52% women, 44% male, 4% undifferentiated), and all completed the trial through the day 71 interim end point. Binding and neutralizing antibodies emerged rapidly by day 8 after initial immunization in 90% and 25% of vaccine recipients, respectively. By day 57, binding and neutralizing antibodies were detected in 100% of vaccine recipients after a single immunization. On day 71, the geometric mean titers of spike-specific binding antibodies were 2432 to 5729 and the geometric mean titers of neutralizing antibodies were 242 to 449 in the vaccinated groups. A variety of antibody subclasses, Fc receptor binding properties, and antiviral functions were induced. CD4+ and CD8+ T-cell responses were induced. CONCLUSION AND RELEVANCE: In this phase 1 study, a single immunization with Ad26.COV2.S induced rapid binding and neutralization antibody responses as well as cellular immune responses. Two phase 3 clinical trials are currently underway to determine the efficacy of the Ad26.COV2.S vaccine. TRIAL REGISTRATION: ClinicalTrials.gov Identifier: NCT04436276
HIV-1 envelope glycoprotein is the primary target for HIV-1–specific antibodies. The native HIV-1 envelope spike on the virion surface is a trimer, but trimeric gp140 and monomeric gp120 currently ...are believed to induce comparable immune responses. Indeed, most studies on the immunogenicity of HIV-1 envelope oligomers have revealed only marginal improvement over monomers. We report here that suitably prepared envelope trimers have nearly all the antigenic properties expected for native viral spikes. These stable, rigorously homogenous trimers have antigenic properties markedly different from those of monomeric gp120s derived from the same sequences, and they induce potent neutralizing antibody responses for a cross-clade set of tier 1 and tier 2 viruses with titers substantially higher than those elicited by the corresponding gp120 monomers. These results, which demonstrate that there are relevant immunologic differences between monomers and high-quality envelope trimers, have important implications for HIV-1 vaccine development.
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