ABSTRACT
Recent surges in SARS-CoV-2 variants of concern (VOCs) call for the need to evaluate levels of vaccine-and infection-induced SARS-CoV-2 neutralizing antibodies (NAbs). CoronaVac (Sinovac Biotech, Beijing, China) is currently being used for mass vaccination in Thailand as well as other low-income countries. Three VOCs currently circulating within Thailand include the B.1.1.7 (Alpha), B.1.351 (Beta), and B.1.617.2 (Delta) strains. We assessed NAb potency against the prototypic strain containing the original spike sequence (WT) compared to that against the 3 VOCs using sera derived from a cohort of healthcare workers who received a full 2-dose regimen of CoronaVac. Sera from two other cohorts consisting of COVID-19 patients who had been hospitalized in 2020 and 2021 were evaluated for comparison. We found that, despite equally robust production of S1-RBD-binding IgG and 100% seropositivity, sera from both CoronaVac vaccinees and naturally infected individuals had significantly reduced neutralizing capacity against all 3 VOCs compared to WT. Strikingly, NAb titers against Alpha and Beta were comparable, but Delta appears to be significantly more refractory to NAbs in all groups. Our results may help inform on CoronaVac NAb-inducing capacity, which is a proxy for vaccine efficacy, in the context of the WT strain and 3 VOCs. Our results also have critical implications for public health decision-makers who may need to maintain efficient mitigation strategies amid a potentially high risk for infection with VOCs even in those who have been previously infected.
ABSTRACT
Herein, we performed a genome-wide association study on SARS-CoV-2 genomes to identify genetic variations that might be associated with the COVID-19 severity. 152 full-length genomes of SARS-CoV-2 that were generated from original clinical samples and whose patient status could be determined conclusively as either "asymptomatic" or "symptomatic" were retrieved from the GISAID database. We found that nucleotide variations at the genomic position 11,083, locating in the coding region of non-structural protein 6, were associated with the COVID-19 severity. While the 11083G variant (i.e. having G at the position 11,083) was more commonly found in symptomatic patients, the 11083T variant appeared to associate more often with asymptomatic infections. We also identified three microRNAs that differentially target the two variants, namely miR-485-3p, miR-539-3p, and miR-3149. This may in part contribute to the differential association of the two SARS-CoV-2 variants with the disease severity.