Vaccinia virus-based vaccines confer protective immunity against SARS-CoV-2 virus in Syrian hamsters.

COVID-19 in humans is caused by Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) that belongs to the beta family of coronaviruses. SARS-CoV-2 causes severe respiratory illness in 10-15% of infected individuals and mortality in 2-3%. Vaccines are urgently needed to prevent infection and to contain viral spread. Although several mRNA- and adenovirus-based vaccines are highly effective, their dependence on the "cold chain" transportation makes global vaccination a difficult task. In this context, a stable lyophilized vaccine may present certain advantages. Accordingly, establishing additional vaccine platforms remains vital to tackle SARS-CoV-2 and any future variants that may arise. Vaccinia virus (VACV) has been used to eradicate smallpox disease, and several attenuated viral strains with enhanced safety for human applications have been developed. We have generated two candidate SARS-CoV-2 vaccines based on two vaccinia viral strains, MVA and v-NY, that express full-length SARS-CoV-2 spike protein. Whereas MVA is growth-restricted in mammalian cells, the v-NY strain is replication-competent. We demonstrate that both candidate recombinant vaccines induce high titers of neutralizing antibodies in C57BL/6 mice vaccinated according to prime-boost regimens. Furthermore, our vaccination regimens generated TH1-biased immune responses in mice. Most importantly, prime-boost vaccination of a Syrian hamster infection model with MVA-S and v-NY-S protected the hamsters against SARS-CoV-2 infection, supporting that these two vaccines are promising candidates for future development. Finally, our vaccination regimens generated neutralizing antibodies that partially cross-neutralized SARS-CoV-2 variants of concern.

Protogenin defines a transition stage during embryonic neurogenesis and prevents precocious neuronal differentiation.

Many Ig superfamily members are expressed in the developing nervous system, but the functions of these molecules during neurogenesis are not all clear. Here, we explore the expression and function of one of members of this superfamily, protogenin (PRTG), in the developing nervous system. Expression of PRTG protein is strong in the neural tube of mouse embryos between embryonic days 7.75 and 9.5 but disappears after embryonic day 10.5 when the neural progenitor marker nestin expresses prominently. Perturbation of PRTG activity in P19 embryonal carcinoma cells and in chick embryos, by either RNA interference or a dominant-negative PRTG mutant, increases neuronal differentiation. Using yeast two-hybrid screening and an in situ binding assay, we were able to identify ERdj3 (a stress-inducible endoplasmic reticulum DnaJ homolog) as a putative PRTG ligand. Addition of purified ERdj3 protein into the P19 differentiation assay reduced neurogenesis. This effect was blocked by addition of either a neutralizing antibody against PRTG or purified PRTG ectodomain protein, indicating that the effect of ERdj3 on neurogenesis is mediated through PRTG. Forced expression of ERdj3 in the chick neural tube also impairs neuronal differentiation. Together, these results suggest that expression of PRTG defines a stage between pluripotent epiblasts and committed neural progenitors, and its signaling plays a critical role in suppressing premature neuronal differentiation during early neural development.