Mosaic sarbecovirus vaccination elicits cross-reactive responses in pre-immunized animals

Immunization with mosaic-8b [60-mer nanoparticles presenting 8 SARS-like betacoronavirus (sarbecovirus) receptor-binding domains (RBDs)] elicits more broadly cross-reactive antibodies than homotypic SARS-CoV-2 RBD-only nanoparticles and protects against sarbecoviruses. To investigate original antigenic sin (OAS) effects on mosaic-8b efficacy, we evaluated effects of prior COVID-19 vaccinations in non-human primates and mice on sarbecovirus response breadths elicited by mosaic-8b, admix-8b (8 homotypics), and homotypic SARS-CoV-2, finding greatest cross-reactivity for mosaic-8b. As demonstrated by molecular fate-mapping in which antibodies derived from specific cohorts of B cells are differentially detected, B cells primed by WA1 spike mRNA-LNP dominated antibody responses after RBD-nanoparticle boosting. While mosaic-8b- and homotypic-nanoparticles boosted cross-reactive antibodies, de novo antibodies were predominantly induced with mosaic-8b boosting, and these were specific for variant RBDs with increased identity to RBDs on mosaic-8b. These results inform OAS mechanisms and support using mosaic-8b to protect COVID-19 vaccinated/infected humans against as-yet-unknown SARS-CoV-2 variants and animal sarbecoviruses with human spillover potential.

Kinetics of Myeloid-Derived Suppressor Cell Frequency and Function during Simian Immunodeficiency Virus Infection, Combination Antiretroviral Therapy, and Treatment Interruption

During chronic lentiviral infection, poor clinical outcomes correlate both with systemic inflammation and poor proliferative ability of HIV-specific T cells; however, the connection between the two is not clear. Myeloid-derived suppressor cells (MDSC), which expand during states of elevated circulating inflammatory cytokines, may link the systemic inflammation and poor T cell function characteristic of lentiviral infections. Although MDSC are partially characterized in HIV and SIV infection, questions remain regarding their persistence, activity, and clinical significance. We monitored MDSC frequency and function in SIV-infected rhesus macaques. Low MDSC frequency was observed prior to SIV infection. Post-SIV infection, MDSC were elevated in acute infection and persisted during 7 mo of combination antiretroviral drug therapy (cART). After cART interruption, we observed MDSC expansion of surprising magnitude, the majority being granulocytic MDSC. At all stages of infection, granulocytic MDSC suppressed CD4+ and CD8+ T cell proliferation in response to polyclonal or SIV-specific stimulation. In addition, MDSC frequency correlated significantly with circulating inflammatory cytokines. Acute and post-cART levels of viremia were similar, however, the levels of inflammatory cytokines and MDSC were more pronounced post-cART. Expanded MDSC during SIV infection, especially during the post-cART inflammatory cytokine surge, likely limit cellular responses to infection. As many HIV curative strategies require cART interruption to determine efficacy, our work suggests treatment interruption-induced MDSC may especially undermine the effectiveness of such strategies. MDSC depletion may enhance T cell responses to lentiviral infection and the effectiveness of curative approaches.

Simultaneous and sensitive detection of human immunodeficiency virus type 1 (HIV) drug resistant genotypes by multiplex oligonucleotide ligation assay

Oligonucleotide ligation assay (OLA) is a highly specific and relatively simple method to detect point mutations encoding HIV-1 drug-resistance, which can detect mutants comprising ≥2-5% of the viral population. Nevirapine (NVP), tenofovir (TDF) and lamivudine (3TC) are antiretroviral (ARV) drugs used worldwide for treatment of HIV infection and prevention of mother-to-child-transmission. Adapting the OLA to detect multiple mutations associated with HIV resistance to these ARV simultaneously would provide an efficient tool to monitor drug resistance in resource-limited settings. Known proportions of mutant and wild-type plasmids were used to optimize a multiplex OLA for detection of K103N, Y181C, K65R, and M184V in HIV subtypes B and C, and V106M and G190A in subtype C. Simultaneous detection of two mutations was impaired if probes annealed to overlapping regions of the viral template, but was sensitive to ≥2-5% when testing codons using non-overlapping probes. PCR products from HIV-subtype B- and C-infected individuals were tested by multiplex-OLA and compared to results of single-codon OLA. Multiplex-OLA detected mutations at codon pairs 103/181, 106/190 and 65/184 reliably when compared to singleplex-OLA in clinical specimens. The multiplex-OLA is sensitive and specific and reduces the cost of screening for NVP, TDF and/or 3TC resistance.