Single immunization with recombinant ACAM2000 vaccinia viruses expressing the spike and the nucleocapsid proteins protect hamsters against SARS-CoV-2 caused clinical disease

Increasing cases of SARS-CoV-2 breakthrough infections from immunization with predominantly spike protein based COVID-19 vaccines highlight the need for alternative vaccines using different platforms and/or antigens. In this study, we expressed SARS-CoV-2 spike and nucleocapsid proteins in a novel vaccinia virus ACAM2000 platform (rACAM2000). Following a single intramuscular immunization, the rACAM2000 co-expressing the spike and nucleocapsid proteins induced significantly improved protection against SARS-CoV-2 challenge in comparison to rACAM2000 expressing the individual proteins in a hamster model, as shown by reduced weight loss and quicker recovery time. The protection was associated with reduced viral loads, increased neutralizing antibody titre and reduced neutrophil-to-lymphocyte ratio. Thus, our study demonstrates that the rACAM2000 expressing a combination of the spike and nucleocapsid antigens is a promising COVID-19 vaccine candidate and further studies will investigate if the rACAM2000 vaccine candidate can induce a long lasting immunity against infection of SARS-CoV-2 variants of concern.

Screen for new mutations on the 2nd chromosome involved in indirect flight muscle development in Drosophila melanogaster.

An extensive ethylmethanesulfonate mutagenesis of Drosophila melanogaster was undertaken to isolate the stronger alleles of 3 indirect flight-muscle mutations. We isolated 17 strong mutant lines, with nearly complete penetrance and expressivity, using direct screening under polarized light, from more than 1700 mutagenized chromosomes. On complementation, we found 11 of these 17 mutant lines to be alleles of 3 indirect flight-muscle mutations (Ifm(2)RU1, 3 noncomplementing lines; ifm(2)RU2, 6 alleles; ifm(2)RU3, 2 alleles) of the previously isolated 8 complementation groups (Ifm(2)RU1to ifm(2)RU8). In addition, we found 6 new complementation groups with strong defects in adult-muscle morphology; we named these ifm(2)RS1 to ifm(2)RS6. All mutant lines were mapped by meiotic recombination, and 5 of the 6 new complementation lines were mapped using chromosome deficiencies. ifm(2)RS1 maps to a region that harbors ifm(2)RU4 (a mutation that was isolated previously); however, theses are not alleles because each complements the other mutation, and the mutant-muscle phenotype is very different. We used direct screening under polarized light to find recessive mutations; although this method was labor intensive, it can be used to identify recessive genes involved in myogenesis, unlike screens for flightlessness or wing-position defects. This screen identifies regions on the second chromosome that harbor probable genes that are likely expressed in the mesoderm and are thought to be involved in myogenesis. This screen has generated valuable resources that will help us to understand the role of many molecular players involved in myogenesis.