Differential Cell Line Susceptibility to the SARS-CoV-2 Omicron BA.1.1 Variant of Concern

The unique mutations of the SARS-CoV-2 Omicron variant are associated with increased transmissibility, immune escape, increased binding affinity to ACE-2, and increased viral load. Omicron exhibited a shift in tropism infecting the upper respiratory tract compared to other variants of concern which have tropism for the lower respiratory tract. The tropism of omicron variants in cell lines of different hosts and tissue origins still remains unclear. Considering this, we assessed the susceptibility of different cell lines to the SARS-CoV-2 omicron BA.1.1 variant and permissiveness among different cell lines for omicron replication. Susceptibility and permissiveness of a total of eleven cell lines, including six animal cell lines and five human cell lines for omicron BA.1.1 infection, were evaluated by infecting individual cell lines with omicron BA.1.1 isolate at a 0.1 multiplicity of infection. Virus replication was assessed by observation of cytopathic effects followed by viral load determination by real-time PCR assay and virus infectivity determination by TCID50 assay. The characteristic cytopathic effect, increased viral load, and productive omicron replication was detected in Vero CCL-81, Vero E6, Vero/hSLAM, MA-104, and Calu-3 cells. Although LLC MK-2 cells showed an increased TCID50 titer at the second infection, the viral load did not show much difference in both infections. Caco-2 cells did not show evident CPE, but they supported omicron replication at a low level. A549, RD, MRC-5, and BHK-21 cells supported omicron BA.1.1 replication without the CPE. This is the first study on the comparison of susceptibility of different cell lines to Omicron variant BA.1.1, which might be useful for future studies on emerging SARS-CoV-2 variants

Evaluation of immunogenicity post two doses of inactivated SARS-CoV-2 vaccine, Covaxin after six months

We have evaluated the immunogenicity of two dose of Covaxin given at a one-month interval to two adult populations, i.e. COVID-19 naïve-vaccinated individuals (n = 118) and COVID-19 recovered individuals (n = 128) with the vaccination. The immune response in the study population were assessed at three follow-ups, namely at one month post first dose, one and six months after the second dose. The persistence of S1RBD IgG and neutralizing antibodies for six months post vaccination was observed at different time intervals. The enhanced immune response was observed in both the participant groups. The study emphasizes the need for a booster dose post six months of vaccination

First detection of Varicella Zoster Virus clade 9 cases in India during mpox surveillance

AbstractBackground The multi-country mpox outbreak across the globe has led to the systematic surveillance of mpox cases in India. During the surveillance of mpox, we encountered cases of Varicella Zoster Virus (VZV) in suspected mpox cases amongst children & adults. This study focused on the genomic characterization of VZV in India.Methods A total of 331 mpox suspected cases were tested for VZV through real-time PCR, and the positive samples were subjected to next-generation sequencing to retrieve the whole genome of VZV using CLC genomics software. Phylogenetic analysis has been done in MEGA 11.0 software to identify circulating clades.Result Of the 331 suspected cases, 28 cases with vesicular rashes were found to be positive for VZV. The maximum genome could be retrieved from the clinical specimens of 16 cases with coverage greater than 98% when mapped with reference strain Dumas (NC 001348). The phylogenetic analyses of these sequences determined the circulation of clades 1, 5, and 9 in India. Further, the sequence analysis demonstrated non-synonymous single nucleotide polymorphism (SNPs) among specific ORF of VZV including ORF 14, ORF 22, ORF 36, ORF 37 and ORF 51. Although clade 1 and 5 has been reported earlier, the circulation of clade 9 of VZV has been determined for the first time in India.Conclusion Although the circulation of different clades of VZV was reported from India, the presence of clade 9 was detected for the first time during the mpox surveillance