Biology subjects

Swain, J.

Publications and source records attributed to Swain, J..

4 recordsLinked to original sources

bioRxiv2022

Reorganization of F-actin nanostructures is required for the late phases of SARS-CoV-2 replication in pulmonary cells.

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is worldwide the main cause of the COVID-19 pandemic. After infection of human pulmonary cells, intracellular viral replication take place in different cellular compartments resulting in the destruction of the host cells and causing severe respiratory diseases. Although cellular trafficking of SARS-CoV-2 have been explored, little is known about the role of the cytoskeleton during viral replication in pulmonary cells. Here we show that SARS-CoV-2 infection induces dramatic changes of F-actin nanostructures overtime. Ring-like actin nanostructures are surrounding viral intracellular organelles, suggesting a functional interplay between F-actin and viral M clusters during particle assembly. Filopodia-like structures loaded with viruses to neighbour cells suggest these structures as mechanism for cell-to-cell virus transmission. Strikingly, gene expression profile analysis and PKN inhibitor treatments of infected pulmonary cells reveal a major role of alpha-actinins superfamily proteins in SARS-CoV-2 replication. Overall, our results highlight cell actors required for SARS-CoV2 replication that are promises for antiviral targets. TeaserImpairing regulation of actin filaments inhibits SARS-CoV-2 particle production in human pulmonary cells.

microbiology↗

bioRxiv2022

Escherichia coli response to subinhibitory concentration of Colistin: Insights from study of membrane dynamics and morphology.

Prevalence of wide spread bacterial infections bring forth a critical need in understanding the molecular mechanisms of the antibiotics as well as the bacterial response to those antibiotics. Improper usage of antibiotics, which can be in sub-lethal concentrations is one among the multiple reasons for acquiring antibiotic resistance which makes it vital to understand the bacterial response towards sub-lethal concentrations of antibiotics. In this work, we have used colistin, a well-known membrane active antibiotic used to treat severe bacterial infections and explored the impact of its sub-minimum inhibitory concentration (MIC) on the lipid membrane dynamics and morphological changes of E. coli. Upon investigation of live cell membrane properties such as lipid dynamics using fluorescence correlation spectroscopy, we observed that colistin disrupts the lipid membrane at sub-MIC by altering the lipid diffusivity. Interestingly, filamentation-like cell elongation was observed upon colistin treatment which led to further exploration of surface morphology with the help of atomic force spectroscopy. The changes in the surface roughness upon colistin treatment provides additional insight on the colistin-membrane interaction corroborating with the altered lipid diffusion. Although altered lipid dynamics could be attributed to an outcome of lipid rearrangement due to direct disruption by antibiotic molecules on the membrane or an indirect consequence of disruptions in lipid biosynthetic pathways, we were able to ascertain that altered bacterial membrane dynamics is due to direct disruptions. Our results provide a broad overview on the consequence of the cyclic polypeptide, colistin on membrane specific lipid dynamics and morphology of a live Gram-negative bacterial cell.

biophysics↗

bioRxiv2021

Allelic variation in Class I HLA determines pre-existing memory responses to SARS-CoV-2 that shape the CD8+ T cell repertoire upon viral exposure

Effective presentation of antigens by HLA class I molecules to CD8+ T cells is required for viral elimination and generation of long-term immunological memory. In this study, we applied a single-cell, multi-omic technology to generate the first unified ex vivo characterization of the CD8+ T cell response to SARS-CoV-2 across 4 major HLA class I alleles. We found that HLA genotype conditions key features of epitope specificity, TCR /{beta} sequence diversity, and the utilization of pre-existing SARS-CoV-2 reactive memory T cell pools. Single-cell transcriptomics revealed functionally diverse T cell phenotypes of SARS-CoV-2-reactive T cells, associated with both disease stage and epitope specificity. Our results show that HLA variations influence pre-existing immunity to SARS-CoV-2 and shape the immune repertoire upon subsequent viral exposure. One-Sentence SummaryWe perform a unified, multi-omic characterization of the CD8+ T cell response to SARS-CoV-2, revealing pre-existing immunity conditioned by HLA genotype.

immunology↗

bioRxiv2021

High resolution profiling of MHC-II peptide presentation capacity, by Mammalian Epitope Display, reveals SARS-CoV-2 targets for CD4 T cells and mechanisms of immune-escape

Understanding the mechanisms of immune evasion is critical for formulating an effective response to global threats like SARS-CoV2. We have fully decoded the immune synapses for multiple TCRs from acute patients, including cognate peptides and the presenting HLA alleles. Furthermore, using a newly developed mammalian epitope display platform (MEDi), we determined that several mutations present in multiple viral isolates currently expanding across the globe, resulted in reduced presentation by multiple HLA class II alleles, while some increased presentation, suggesting immune evasion based on shifting MHC-II peptide presentation landscapes. In support, we found that one of the mutations present in B1.1.7 viral strain could cause escape from CD4 T cell recognition in this way. Given the importance of understanding such mechanisms more broadly, we used MEDi to generate a comprehensive analysis of the presentability of all SARS-CoV-2 peptides in the context of multiple common HLA class II molecules. Unlike other strategies, our approach is sensitive and scalable, providing an unbiased and affordable high-resolution map of peptide presentation capacity for any MHC-II allele. Such information is essential to provide insight into T cell immunity across distinct HLA haplotypes across geographic and ethnic populations. This knowledge is critical for the development of effective T cell therapeutics not just against COVID-19, but any disease.

immunology↗