Molecular characterization of Influenza A pandemic H1N1 viruses circulating in eastern India during 2017-19: Antigenic diversity in comparison to the vaccine strains.

In the endemic settings of India, high CFR (3.6-7.02%) was observed in the consecutive 2009, 2015 and 2017 A/H1N1pdm09 outbreaks, though in eastern India CFR varied between 0 and 5.5% during same period. Recurrent outbreaks of pandemic Influenza A/H1N1pdm09, fragmented nationwide incidence data, lack of national policy for Influenza vaccination in India underscores the necessity for generating regional level data. Thus, during 2017-19, 4106 referred samples from patients hospitalized with severe acute respiratory illness (SARI) in eastern India were tested for A/H1N1pdm09 infection. Among which 16.5% (n = 677/4106) were found A/H1N1pdm09 positive. Individuals <20 years and middle-aged persons (40-60 years) were most susceptible to A/H1N1pdm09 infection. The vaccine strain (A/human/California/07/2009) which was globally used before 2017, clustered in a different lineage away from the representative eastern Indian strains in the phylogenetic dendrogram. The vaccine strain (A/human/Michigan/45/2015) used in India during the study period and the WHO recommended strain (A/human/Brisbane/02/2018) for 2019-20 flu season for the northern hemisphere, clustered with the circulating isolates in the same lineage-6b. Dissimilarities in the amino acids encompassing the antigenic epitopes were seen to be highest with the vaccine strain- A/human/California/07/2009. The significant amino acid variations in the circulating strains with the current WHO recommended vaccine strain, implies the exigency of continuous pandemic A/H1N1pdm09 surveillance studies in this epidemiological setting. The absence of any Oseltamivir resistant mutation (H275Y) in the neuraminidase gene of the current isolates suggests continuing use of Tamiflu® as an antiviral therapy in suspected subjects in this region.

Implications derived from S-protein variants of SARS-CoV-2 from six continents.

The spike (S) protein is a critical determinant of the infectivity and antigenicity of SARS-CoV-2. Several mutations in the S protein of SARS-CoV-2 have already been detected, and their effect in immune system evasion and enhanced transmission as a cause of increased morbidity and mortality are being investigated. From pathogenic and epidemiological perspectives, S proteins are of prime interest to researchers. This study focused on the unique variants of S proteins from six continents: Asia, Africa, Europe, Oceania, South America, and North America. In comparison to the other five continents, Africa had the highest percentage of unique S proteins (29.1%). The phylogenetic relationship implies that unique S proteins from North America are significantly different from those of the other five continents. They are most likely to spread to the other geographic locations through international travel or naturally by emerging mutations. It is suggested that restriction of international travel should be considered, and massive vaccination as an utmost measure to combat the spread of the COVID-19 pandemic. It is also further suggested that the efficacy of existing vaccines and future vaccine development must be reviewed with careful scrutiny, and if needed, further re-engineered based on requirements dictated by new emerging S protein variants.

Crucial Mutations of Spike Protein on SARS-CoV-2 Evolved to Variant Strains Escaping Neutralization of Convalescent Plasmas and RBD-Specific Monoclonal Antibodies.

Small number of SARS-CoV-2 epidemic lineages did not efficiently exhibit a neutralization profile, while single amino acid mutation in the spike protein has not been confirmed in altering viral antigenicity resulting in immune escape. To identify crucial mutations in spike protein that escape humoral immune response, we evaluated the cross-neutralization of convalescent plasmas and RBD-specific monoclonal antibodies (mAbs) against various spike protein-based pseudoviruses. Three of 24 SARS-CoV-2 pseudoviruses containing different mutations in spike protein, including D614G, A475V, and E484Q, consistently showed an altered sensitivity to neutralization by convalescent plasmas. A475V and E484Q mutants are highly resistant to neutralization by mAb B38 and 2-4, suggesting that some crucial mutations in spike protein might evolve SARS-CoV-2 variants capable of escaping humoral immune response.