Induction of poxviral immunity by synthetic MVA-based dual-antigen COVID-19 vaccine COH04S1

The recent outbreak of monkeypox (MPXV) outside its endemic boundaries has attracted global attention and prompted world leaders to reserve millions of doses of the only approved third-generation smallpox/MPXV vaccine, Jynneos, which is based on the highly attenuated modified vaccinia Ankara (MVA) vector. We previously developed COH04S1, a multiantigen SARS-CoV-2 vaccine built on a synthetic MVA (sMVA) platform. COH04S1 was extensively tested for efficacy and immunogenicity in animal models, including non-human primates (NHP), and was found to be safe and to induce SARS-CoV-2-specific immunity in a Phase 1 clinical trial in healthy adults. Here we demonstrate that one or two vaccinations of NHP with either COH04S1 or sMVA elicit robust othopoxvirus-specific binding and neutralizing antibody responses. Furthermore, healthy adults vaccinated with COH04S1 at different dose levels develop robust othopoxvirus-specific humoral and cellular immune responses that are durable for over six months post-vaccination. Importantly, both COH04S1 and sMVA vaccinations induce elevated and sustained antibody responses to MPXV-proteins that are major targets of protective neutralizing antibodies. These results demonstrate that COH04S1 and sMVA are valuable vaccine candidates to stimulate robust orthopox/MPXV-specific humoral and cellular immunity.

The N-terminal and central domains of CoV-2 nsp1 play key functional roles in suppression of cellular gene expression and preservation of viral gene expression

Nonstructural protein 1 (nsp1) is the first viral protein synthesized during coronavirus (CoV) infection and is a key virulence factor that dampens the innate immune response. It restricts cellular gene expression through a combination of inhibiting translation by blocking the mRNA entry channel of the 40S ribosomal subunit and by promoting mRNA degradation. We performed a detailed structure-guided mutational analysis of CoV-2 nsp1 coupled with in vitro and cell-based functional assays, revealing insight into how it coordinates these activities against host but not viral mRNA. We found that residues in the N-terminal and central regions of nsp1 not involved in docking into the 40S mRNA entry channel nonetheless stabilize its association with the ribosome and mRNA, thereby enhancing its restriction of host gene expression. These residues are also critical for the ability of mRNA containing the CoV-2 leader sequence to escape translational repression. Notably, we identify CoV-2 nsp1 mutants that gain the ability to repress translation of viral leader-containing transcripts. These data support a model in which viral mRNA binding functionally alters the association of nsp1 with the ribosome, which has implications for drug targeting and understanding how engineered or emerging mutations in CoV-2 nsp1 could attenuate the virus.

Gender Disparity Impacts on Thymus Aging and LHRH Receptor Antagonist-Induced Thymic Reconstitution Following Chemotherapeutic Damage.

One of the main consequences of thymus aging is the decrease in naïve T cell output. This condition accelerates at the onset of puberty, and presents as a major clinical complication for cancer patients who require cytoablative therapy. Specifically, the extensive use of chemotherapeutics, such as cyclophosphamide, in such treatments damage thymic structure and eliminate the existing naïve T cell repertoire. The resulting immunodeficiency can lead to increased incidence of opportunistic infections, tumor growth relapse and/or autoimmune diseases, particularly in older patients. Thus, strategies aimed at rejuvenating the aged thymus following chemotherapeutic damage are required. Previous studies have revealed that sex hormone deprivation in male mice is capable of regenerating the thymic microenvironment following chemotherapy treatment, however, further investigation is crucial to identify gender-based differences, and the molecular mechanisms involved during thymus regeneration. Through phenotypic analyzes, we identified gender-specific alterations in thymocytes and thymic epithelial cell (TEC) subsets from the onset of puberty. By middle-age, females presented with a higher number of thymocytes in comparison to males, yet a decrease in their Aire+ medullary TEC/thymocyte ratio was observed. This reduction could be associated with an increased risk of autoimmune disease in middle-aged women. Given the concurrent increase in female Aire+ cTEC/thymocyte ratio, we proposed that there may be an impediment in Aire+ mTEChi differentiation, and Aire+ cTEChi as its upstream precursor. The regenerative effects of LHRH receptor antagonist, degarelix, on TEC subsets was also less pronounced in middle-aged females compared to males, possibly due to slower progression of thymic involution in the former, which presented with greater TEChi proportions. Furthermore, following cyclophosphamide treatment, degarelix enhanced thymocyte and mature TEC subset recovery, with faster recovery kinetics observed in females. These events were found to involve both reactivation and proliferation of thymic epithelial progenitor cells. Taken together, the findings from this study portray a relationship between gender disparity and thymus aging, and highlight the potential benefits of LHRH receptor antagonist treatment for thymic regeneration. Further research is required, however, to determine how gender may impact on the mechanisms underpinning these events.