Non-neutralizing antibody functions for protection and control HIV in humans and SIV and SHIV in non-human primates

Antibodies to S2 domain of SARS-CoV-2 spike protein in Moderna mRNA vaccinated subjects sustain antibody-dependent NK cell-mediated cell cytotoxicity against Omicron BA.1

Vaccination with the primary two-dose series of SARS-CoV-2 mRNA protects against infection with the ancestral strain, and limits the presentation of severe disease after re-infection by multiple variants of concern (VOC), including Omicron, despite the lack of a strong neutralizing response to these variants. We compared antibody responses in serum samples collected from mRNA-1273 (Moderna) vaccinated subjects to identify mechanisms of immune escape and cross-protection. Using pseudovirus constructs containing domain-specific amino acid changes representative of Omicron BA.1, combined with domain competition and RBD-antibody depletion, we showed that RBD antibodies were primarily responsible for virus neutralization and variant escape. Antibodies to NTD played a less significant role in antibody neutralization but acted along with RBD to enhance neutralization. S2 of Omicron BA.1 had no impact on neutralization escape, suggesting it is a less critical domain for antibody neutralization; however, it was as capable as S1 at eliciting IgG3 responses and NK-cell mediated, antibody-dependent cell cytotoxicity (ADCC). Antibody neutralization and ADCC activities to RBD, NTD, and S1 were all prone to BA.1 escape. In contrast, ADCC activities to S2 resisted BA.1 escape. In conclusion, S2 antibodies showed potent ADCC function and resisted Omicron BA.1 escape, suggesting that S2 contributes to cross-protection against Omicron BA.1. In line with its conserved nature, S2 may hold promise as a vaccine target against future variants of SARS-CoV-2.

Antiviral antibody responses to systemic administration of an oncolytic RNA virus: the impact of standard concomitant anticancer chemotherapies

Background

Oncolytic reovirus therapy for cancer induces a typical antiviral response to this RNA virus, including neutralizing antibodies. Concomitant treatment with cytotoxic chemotherapies has been hypothesized to improve the therapeutic potential of the virus. Chemotherapy side effects can include immunosuppression, which may slow the rate of the antiviral antibody response, as well as potentially make the patient more vulnerable to viral infection.

Method

Reovirus neutralizing antibody data were aggregated from separate phase I clinical trials of reovirus administered as a single agent or in combination with gemcitabine, docetaxel, carboplatin and paclitaxel doublet or cyclophosphamide. In addition, the kinetics of individual antibody isotypes were profiled in sera collected in these trials.

Results

These data demonstrate preserved antiviral antibody responses, with only moderately reduced kinetics with some drugs, most notably gemcitabine. All patients ultimately produced an effective neutralizing antibody response.

Conclusion

Patients’ responses to infection by reovirus are largely unaffected by the concomitant drug treatments tested, providing confidence that RNA viral treatment or infection is compatible with standard of care treatments.

Effect of polymorphisms in porcine guanylate-binding proteins on host resistance to PRRSV infection in experimentally challenged pigs

Guanylate-binding proteins (GBP1 and GBP5) are known to be important for host resistance against porcine reproductive and respiratory syndrome virus (PRRSV) infection. In this study, the effects of polymorphisms in GBP1 (GBP1E2 and WUR) and GBP5 on host immune responses against PRRSV were investigated to elucidate the mechanisms governing increased resistance to this disease. Seventy-one pigs [pre-genotyped based on three SNP markers (GBP1E2, WUR, and GBP5)] were assigned to homozygous (n = 36) and heterozygous (n = 35) groups and challenged with the JA142 PRRSV strain. Another group of nineteen pigs was kept separately as a negative control group. Serum and peripheral blood mononuclear cells (PBMCs) were collected at 0, 3, 7, 14, 21 and 28 days post-challenge (dpc). Viremia and weight gain were measured in all pigs at each time point, and a flow cytometry analysis of PBMCs was performed to evaluate T cell activation. In addition, 15 pigs (5 pigs per homozygous, heterozygous and negative groups) were sacrificed at 3, 14 and 28 dpc, and the local T cell responses were evaluated in the lungs, bronchoalveolar lavage cells (BALc), lymph nodes and tonsils. The heterozygous pigs showed lower viral loads in the serum and lungs and higher weight gains than the homozygous pigs based on the area under the curve calculation. Consistently, compared with the homozygous pigs, the heterozygous pigs exhibited significantly higher levels of IFN-α in the serum, proliferation of various T cells (γδT, Th1, and Th17) in PBMCs and tissues, and cytotoxic T cells in the lungs and BALc. These results indicate that the higher resistance in the pigs heterozygous for the GBP1E2, WUR and GBP5 markers could be mediated by increased antiviral cytokine (IFN-α) production and T cell activation.

Update on Fc-Mediated Antibody Functions Against HIV-1 Beyond Neutralization

Antibodies (Abs) are the major component of the humoral immune response and a key player in vaccination. The precise Ab-mediated inhibitory mechanisms leading to in vivo protection against HIV have not been elucidated. In addition to the desired viral capture and neutralizing Ab functions, complex Ab-dependent mechanisms that involve engaging immune effector cells to clear infected host cells, immune complexes, and opsonized virus have been proposed as being relevant. These inhibitory mechanisms involve Fc-mediated effector functions leading to Ab-dependent cellular cytotoxicity, phagocytosis, cell-mediated virus inhibition, aggregation, and complement inhibition. Indeed, the decreased risk of infection observed in the RV144 HIV-1 vaccine trial was correlated with the production of non-neutralizing inhibitory Abs, highlighting the role of Ab inhibitory functions besides neutralization. Moreover, Ab isotypes and subclasses recognizing specific HIV envelope epitopes as well as pecular Fc-receptor polymorphisms have been associated with disease progression. These findings further support the need to define which Fc-mediated Ab inhibitory functions leading to protection are critical for HIV vaccine design. Herein, based on our previous review Su & Moog Front Immunol 2014, we update the different inhibitory properties of HIV-specific Abs that may potentially contribute to HIV protection.

A Recombinant Rabies Virus Expressing the Marburg Virus Glycoprotein Is Dependent upon Antibody-Mediated Cellular Cytotoxicity for Protection against Marburg Virus Disease in a Murine Model

Marburg virus (MARV) is a filovirus related to Ebola virus (EBOV) associated with human hemorrhagic disease. Outbreaks are sporadic and severe, with a reported case mortality rate of upward of 88%. There is currently no antiviral or vaccine available. Given the sporadic nature of outbreaks, vaccines provide the best approach for long-term control of MARV in regions of endemicity. We have developed an inactivated rabies virus-vectored MARV vaccine (FILORAB3) to protect against Marburg virus disease. Immunogenicity studies in our labs have shown that a Th1-biased seroconversion to both rabies virus and MARV glycoproteins (GPs) is beneficial for protection in a preclinical murine model. As such, we adjuvanted FILORAB3 with glucopyranosyl lipid adjuvant (GLA), a Toll-like receptor 4 agonist, in a squalene-in-water emulsion. Across two different BALB/c mouse challenge models, we achieved 92% protection against murine-adapted Marburg virus (ma-MARV). Although our vaccine elicited strong MARV GP antibodies, it did not strongly induce neutralizing antibodies. Through both in vitro and in vivo approaches, we elucidated a critical role for NK cell-dependent antibody-mediated cellular cytotoxicity (ADCC) in vaccine-induced protection. Overall, these findings demonstrate that FILORAB3 is a promising vaccine candidate for Marburg virus disease.IMPORTANCE Marburg virus (MARV) is a virus similar to Ebola virus and also causes a hemorrhagic disease which is highly lethal. In contrast to EBOV, only a few vaccines have been developed against MARV, and researchers do not understand what kind of immune responses are required to protect from MARV. Here we show that antibodies directed against MARV after application of our vaccine protect in an animal system but fail to neutralize the virus in a widely used virus neutralization assay against MARV. This newly discovered activity needs to be considered more when analyzing MARV vaccines or infections.

Deinococcus Mn2+-peptide complex: A novel approach to alphavirus vaccine development

Over the last ten years, Chikungunya virus (CHIKV), an Old World alphavirus has caused numerous outbreaks in Asian and European countries and the Americas, making it an emerging pathogen of great global health importance. Venezuelan equine encephalitis virus (VEEV), a New World alphavirus, on the other hand, has been developed as a bioweapon in the past due to its ease of preparation, aerosol dispersion and high lethality in aerosolized form. Currently, there are no FDA approved vaccines against these viruses. In this study, we used a novel approach to develop inactivated vaccines for VEEV and CHIKV by applying gamma-radiation together with a synthetic Mn-decapeptide-phosphate complex (MnDpPi), based on manganous-peptide-orthophosphate antioxidants accumulated in the extremely radiation-resistant bacterium Deinococcus radiodurans. Classical gamma-irradiated vaccine development approaches are limited by immunogenicity-loss due to oxidative damage to the surface proteins at the high doses of radiation required for complete virus-inactivation. However, addition of MnDpPi during irradiation process selectively protects proteins, but not the nucleic acids, from the radiation-induced oxidative damage, as required for safe and efficacious vaccine development. Previously, this approach was used to develop a bacterial vaccine. In the present study, we show that this approach can successfully be applied to protecting mice against viral infections. Irradiation of VEEV and CHIKV in the presence of MnDpPi resulted in substantial epitope preservation even at supra-lethal doses of gamma-rays (50,000Gy). Irradiated viruses were found to be completely inactivated and safe in vivo (neonatal mice). Upon immunization, VEEV inactivated in the presence of MnDpPi resulted in drastically improved protective efficacy. Thus, the MnDpPi-based gamma-inactivation approach described here can readily be applied to developing vaccines against any pathogen of interest in a fast and cost-effective manner.