Mead, H. | bioRxiv Science

bioRxiv2023

Recurrent SARS-CoV-2 mutations at Spike D796 evade antibodies from pre-Omicron convalescent and vaccinated subjects

SARS-CoV-2 lineages of the Omicron variant rapidly became dominant in early 2022 and frequently cause human infections despite vaccination or prior infection with other variants. In addition to antibody-evading mutations in the Receptor Binding Domain, Omicron features amino acid mutations elsewhere in the Spike protein, however their effects generally remain ill-defined. The Spike D796Y substitution is present in all Omicron sub-variants and occurs at the same site as a mutation (D796H) selected during viral evolution in a chronically-infected patient. Here we map antibody reactivity to a linear epitope in the Spike protein overlapping position 796. We show that antibodies binding this region arise in pre-Omicron SARS-CoV-2 convalescent and vaccinated subjects, but that both D796Y and D796H abrogate their binding. These results suggest that D796Y contributes to the fitness of Omicron in hosts with pre-existing immunity to other variants of SARS-CoV-2 by evading antibodies targeting this site.

immunology↗

bioRxiv2023

Using double cut in vitro assembled CRISPR/Cas9 to modify the genome of Coccidioides posadasii

Although the genus Coccidioides is divided into two closely related and putatively allopatric species, analysis shows that hybridization has occurred between species and at least one C. posadasii conserved fragment has introgressed into several C. immitis genomes in a population-specific manner. Transcript abundance in vitro and in vivo for ten ORFs in this introgressed region were measured for several isolates. We used signals of introgression and high mRNA transcript levels in the spherule as indicators of selection for genes related to critical biological processes involved in Coccidioides pathogenesis. The only transcript in the introgression region with significant expression was a gene that encodes for a betadefensin-like (DEFBL) peptide rich in serines and cysteines. Few virulence factors have been identified in Coccidioides, and we employed the CRISPR-Cas9 mediated gene deletion tool to delete this gene in Coccidioides.

molecular biology↗

bioRxiv2022

Low alcohol preferring mice have reduced task engagement during a waiting task for alcohol, which is enhanced by intermittent alcohol drinking

Alcohol use disorder (AUD) is related to excessive binge alcohol consumption, and there is considerable interest in associated factors that promote intake. AUD has many behavioral facets that enhance inflexibility toward alcohol consumption, including impulsivity, motivation, and attention. Thus, it is important to understand how these factors might promote responding for alcohol and can change after protracted alcohol intake. Previous studies have explored such behavioral factors using responding for sugar in the 5-Choice Serial Reaction Time Task (5-CSRTT), which allows careful separation of impulsivity, attention, and motivation. Importantly, our studies uniquely focus on using alcohol as the reward throughout training and testing sessions, which is critical for beginning to answer central questions relating to behavioral engagement for alcohol. Alcohol preference and consumption in C57BL/6 mice were determined from the first 9 sessions of 2-hour alcohol drinking which were interspersed among 5-CSRTT training. Interestingly, alcohol preference but not consumption level significantly predicted 5-CSRTT responding for alcohol. In contrast, responding for strawberry milk was not related to alcohol preference. Moreover, high-preference (HP) mice made more correct alcohol-directed responses than low-preference (LP) during the first half of each session and had more longer reward latencies in the second half, with no differences when performing for strawberry milk, suggesting that HP motivation for alcohol may reflect "front-loading." Mice were then exposed to an Intermittent Access to alcohol paradigm and retested in 5-CSRTT. While both HP and LP mice increased 5-CSRTT responding for alcohol, but not strawberry milk, LP performance rose to HP levels, with a greater change in correct and premature responding in LP versus HP. Overall, this study provides three significant findings: 1) alcohol was a suitable reward in the 5-CSRTT, allowing dissection of impulsivity, attention, and motivation in relation to alcohol drinking, 2) alcohol preference was a more sensitive indicator of mouse 5-CSRTT performance than consumption, and 3) chronic alcohol drinking promoted behavioral engagement with alcohol, especially for individuals with less initial engagement.

neuroscience↗