Effect of short-term use of FFP2 (N95) masks on the salivary metabolome of young healthy volunteers: a pilot study.

The use of face masks has become an integral part of public life in the post-pandemic era. However, the understanding of the effect of wearing masks on physiology remains incomplete and is required for informing public health policies. For the first time, we report the effects of wearing FFP2 masks on the metabolic composition of saliva, a proximal matrix to breath, along with cardiopulmonary parameters. Un-induced saliva was collected from young (31.2 ± 6.3 years) healthy volunteers (n = 10) before and after wearing FFP2 (N95) masks for 30 minutes and analyzed using GCMS. The results showed that such short-term mask use did not cause any significant change in heart rate, pulse rate or SpO2. Three independent data normalization approaches were used to analyze the changes in metabolomic signature. The individuality of the overall salivary metabotype was found to be unaffected by mask use. However, a trend of an increase in the salivary abundance of L-fucose, 5-aminovaleric acid, putrescine and phloretic acid was indicated irrespective of the method of data normalization. Quantitative analysis confirmed increases in concentrations of these metabolites in saliva of paired samples amid high inter-individual variability. The results showed that while there was no significant change in measured physiological parameters and individual salivary metabotypes, mask use was associated with correlated changes in these metabolites plausibly originating from altered microbial metabolic activity. These results might also explain the change in odour perception reported to be associated with mask use. Potential implications of these changes on mucosal health and immunity warrants further investigation to evolve more prudent mask use policies.

Characterizations of SARS-CoV-2 mutational profile, spike protein stability and viral transmission.

The recent pandemic of SARS-CoV-2 infection has affected more than 3.0 million people worldwide with more than 200 thousand reported deaths. The SARS-CoV-2 genome has the capability of gaining rapid mutations as the virus spreads. Whole-genome sequencing data offers a wide range of opportunities to study mutation dynamics. The advantage of an increasing amount of whole-genome sequence data of SARS-CoV-2 intrigued us to explore the mutation profile across the genome, to check the genome diversity, and to investigate the implications of those mutations in protein stability and viral transmission. We have identified frequently mutated residues by aligning ~660 SARS-CoV-2 genomes and validated in 10,000 datasets available in GISAID Nextstrain. We further evaluated the potential of these frequently mutated residues in protein structure stability of spike glycoprotein and their possible functional consequences in other proteins. Among the 11 genes, surface glycoprotein, nucleocapsid, ORF1ab, and ORF8 showed frequent mutations, while envelop, membrane, ORF6, ORF7a and ORF7b showed conservation in terms of amino acid substitutions. Combined analysis with the frequently mutated residues identified 20 viral variants, among which 12 specific combinations comprised more than 97% of the isolates considered for the analysis. Some of the mutations across different proteins showed co-occurrences, suggesting their structural and/or functional interaction among different SARS-COV-2 proteins, and their involvement in adaptability and viral transmission. Analysis of protein structure stability of surface glycoprotein mutants indicated the viability of specific variants and are more prone to be temporally and spatially distributed across the globe. A similar empirical analysis of other proteins indicated the existence of important functional implications of several variants. Identification of frequently mutated variants among COVID-19 patients might be useful for better clinical management, contact tracing, and containment of the disease.