The histopathological lesions observed were similar to the earlier reports in hamsters with an onset of inflammatory changes by 3 DPI, which progress to interstitial pneumonia and a complete recovery by 14 DPI [31]. viral genomic RNA copy figures/mL) in (b) throat swab, (c) nasal wash, and (d) faeces samples collected on 3, 5, 7, 10, 12, and 14 days post contamination (DPI). Viral sub genomic mRNA weight (log10 viral subgenomic RNA copy figures/mL) in (e) throat swab, (f) nasal wash, and (g) faeces in hamsters post computer QL47 virus challenge on 3, 5, 7, 10, 12, and 14 DPI. The QL47 mean along with standard deviation is usually depicted in the scatter plot. The statistical significance was assessed using the non-parametric MannCWhitney assessments and = 0.0286) in the samples of the B.1.617.3 variant on day 14 in comparison with B.1. The sgRNA could be detected in the lung and nasal turbinate samples until 7 DPI in all the groups. On QL47 14 DPI, all the hamsters of the Delta variant-infected group QL47 showed significantly high sgRNA copies in nasal turbinates (imply = 2.1 107/mL, = 0.0286) and lungs (mean = 2.1 106/mL, = 0.0286), respectively, whereas in the B.1 and B.1.617.3 group, only 1/4 hamsters showed the presence of sgRNA (Determine 2dCf). Open in a separate window Physique 2 Viral weight in respiratory tract samples of hamsters post contamination. Viral genomic RNA weight (log10 viral genomic RNA copies/mL) in (a) nasal turbinates, (b) trachea, and (c) lung samples collected on 3, 5, 7, and 14 DPI, represented as imply with standard deviation in a scatter plot. Viral sub genomic RNA weight (log10 viral subgenomic RNA copies/mL) in (d) nasal turbinates, (e) trachea, and (f) lung samples collected on 3, 5, 7, and 14 DPI, represented as mean with standard deviation in a scatter plot. The statistical significance was assessed using the non-parametric MannCWhitney assessments, and = 0.0286), on 14 DPI. In the case of Delta and B.1.617.3 variant infection, a significant reduction (= 0.0286) in GMT against the Beta variant i.e., about 2.5- and 2.9-fold reduction, was also seen on 14 DPI. The GMT in the case of Delta variant-infected hamster sera was 1.8-fold reduced against the B.1 and B.1.617.3 variants, whereas the titre of B.1.617.3 infected sera was found to be 1.1-fold reduced against the Delta variant and 1.3-fold reduced against the B.1 variant on 14 DPI. Open in a separate window Physique 3 Antibody response in hamsters post challenge with SARS-CoV-2 variants. (a) Anti-SARS-CoV-2 IgG response in hamsters CGB post computer virus contamination by ELISA. Neutralizing antibody response in hamsters infected with the (b) B.1, (c) B.1.617.2 (Delta), and (d) B.1.617.3 variants against B.1, Delta, B.1.617.3, and B.1.351 (Beta). The dotted collection indicates the limit of detection of the assay. The mean along with standard deviation is usually depicted in the scatter plot. The statistical significance was assessed using the non-parametric MannCWhitney assessments, and em p /em -values less than 0.05 were considered to be statistically significant. 3.4. Lung Pathology in Infected Hamsters Grossly, 2/16 of B.1, 6/16 of B.1.617.2, and 3/ 16 of B.1.617.3 infected hamsters showed congestion and hemorrhages. A slightly higher imply lung excess weight to body weight ratio was observed on day 5 and 7 in the B.1.617.2 infected hamsters (Determine 4a). The cumulative lung histopathological score also showed Delta variant-infected animals with a higher average score during the first week of contamination (Physique 4b). Three/twelve of the Delta and 1/12 of the B.1.617.3 infected hamsters sacrificed during the first week of infection showed diffuse areas of consolidation, hemorrhages, pneumocyte hyperplasia, septal thickening, and perivascular and peribronchial inflammatory cell infiltration of moderate severity, and one hamster in the B.1.617.2 group showed severe lesions (Determine 4cCf). Lung tissues showed minimal to moderate pathological changes in the case of all the B.1 variant-infected hamsters. The lesions observed were mostly focal on all days of sacrifice, except in 2/4 hamsters sacrificed.