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.

Omicron BA.2 lineage predominance in severe acute respiratory syndrome coronavirus 2 positive cases during the third wave in North India.

Background: Recent studies on severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) reveal that Omicron variant BA.1 and sub-lineages have revived the concern over resistance to antiviral drugs and vaccine-induced immunity. The present study aims to analyze the clinical profile and genome characterization of the SARS-CoV-2 variant in eastern Uttar Pradesh (UP), North India. Methods: Whole-genome sequencing (WGS) was conducted for 146 SARS-CoV-2 samples obtained from individuals who tested coronavirus disease 2019 (COVID-19) positive between the period of 1 January 2022 and 24 February 2022, from three districts of eastern UP. The details regarding clinical and hospitalized status were captured through telephonic interviews after obtaining verbal informed consent. A maximum-likelihood phylogenetic tree was created for evolutionary analysis using MEGA7. Results: The mean age of study participants was 33.9 ± 13.1 years, with 73.5% accounting for male patients. Of the 98 cases contacted by telephone, 30 (30.6%) had a travel history (domestic/international), 16 (16.3%) reported having been infected with COVID-19 in past, 79 (80.6%) had symptoms, and seven had at least one comorbidity. Most of the sequences belonged to the Omicron variant, with BA.1 (6.2%), BA.1.1 (2.7%), BA.1.1.1 (0.7%), BA.1.1.7 (5.5%), BA.1.17.2 (0.7%), BA.1.18 (0.7%), BA.2 (30.8%), BA.2.10 (50.7%), BA.2.12 (0.7%), and B.1.617.2 (1.3%) lineages. BA.1 and BA.1.1 strains possess signature spike mutations S:A67V, S:T95I, S:R346K, S:S371L, S:G446S, S:G496S, S:T547K, S:N856K, and S:L981F, and BA.2 contains S:V213G, S:T376A, and S:D405N. Notably, ins214EPE (S1- N-Terminal domain) mutation was found in a significant number of Omicron BA.1 and sub-lineages. The overall Omicron BA.2 lineage was observed in 79.5% of women and 83.2% of men. Conclusion: The current study showed a predominance of the Omicron BA.2 variant outcompeting the BA.1 over a period in eastern UP. Most of the cases had a breakthrough infection following the recommended two doses of vaccine with four in five cases being symptomatic. There is a need to further explore the immune evasion properties of the Omicron variant.

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.

Protective efficacy of COVAXIN® against Delta and Omicron variants in hamster model.

The immunity acquired after natural infection or vaccinations against SARS-CoV-2 tend to wane with time. Here, we compared the protective efficacy of COVAXIN® following two- and three-dose immunizations against the Delta variant and also studied the efficacy of COVAXIN® against Omicron variants in a Syrian hamster model. Despite the comparable neutralizing antibody response against the homologous vaccine strain in both the two-dose and three-dose immunized groups, considerable reduction in the lung disease severity was observed in the 3 dose immunized group after Delta variant challenge. In the challenge study using the Omicron variants, i.e., BA.1.1 and BA.2, lesser virus shedding, lung viral load and lung disease severity were observed in the immunized groups. The present study shows that administration of COVAXIN® booster dose will enhance the vaccine effectiveness against the Delta variant infection and give protection against the BA.1.1 and BA.2 variants.

Zika a Vector Borne Disease Detected in Newer States of India Amidst the COVID-19 Pandemic.

Background: During the second wave of the COVID-19 pandemic, outbreaks of Zika were reported from Kerala, Uttar Pradesh, and Maharashtra, India in 2021. The Dengue and Chikungunya negative samples were retrospectively screened to determine the presence of the Zika virus from different geographical regions of India. Methods: During May to October 2021, the clinical samples of 1475 patients, across 13 states and a union territory of India were screened and re-tested for Dengue, Chikungunya and Zika by CDC Trioplex Real time RT-PCR. The Zika rRTPCR positive samples were further screened with anti-Zika IgM and Plaque Reduction Neutralization Test. Next generation sequencing was used for further molecular characterization. Results: The positivity was observed for Zika (67), Dengue (121), and Chikungunya (10) amongst screened cases. The co-infections of Dengue/Chikungunya, Dengue/Zika, and Dengue/Chikungunya/Zika were also observed. All Zika cases were symptomatic with fever (84%) and rash (78%) as major presenting symptoms. Of them, four patients had respiratory distress, one presented with seizures, and one with suspected microcephaly at birth. The Asian Lineage of Zika and all four serotypes of Dengue were found in circulation. Conclusion: Our study indicates the spread of the Zika virus to several states of India and an urgent need to strengthen its surveillance.

Nipah Virus Outbreak in Kerala State, India Amidst of COVID-19 Pandemic.

We report here a Nipah virus (NiV) outbreak in Kozhikode district of Kerala state, India, which had caused fatal encephalitis in a 12-year-old boy and the outbreak response, which led to the successful containment of the disease and the related investigations. Quantitative real-time reverse transcription (RT)-PCR, ELISA-based antibody detection, and whole genome sequencing (WGS) were performed to confirm the NiV infection. Contacts of the index case were traced and isolated based on risk categorization. Bats from the areas near the epicenter of the outbreak were sampled for throat swabs, rectal swabs, and blood samples for NiV screening by real-time RT-PCR and anti-NiV bat immunoglobulin G (IgG) ELISA. A plaque reduction neutralization test was performed for the detection of neutralizing antibodies. Nipah viral RNA could be detected from blood, bronchial wash, endotracheal (ET) secretion, and cerebrospinal fluid (CSF) and anti-NiV immunoglobulin M (IgM) antibodies from the serum sample of the index case. Rapid establishment of an onsite NiV diagnostic facility and contact tracing helped in quick containment of the outbreak. NiV sequences retrieved from the clinical specimen of the index case formed a sub-cluster with the earlier reported Nipah I genotype sequences from India with more than 95% similarity. Anti-NiV IgG positivity could be detected in 21% of Pteropus medius (P. medius) and 37.73% of Rousettus leschenaultia (R. leschenaultia). Neutralizing antibodies against NiV could be detected in P. medius. Stringent surveillance and awareness campaigns need to be implemented in the area to reduce human-bat interactions and minimize spillover events, which can lead to sporadic outbreaks of NiV.

Possible Role of Accessory Proteins in the Viral Replication for the 20I/501Y.V1 (B.1.1.7) SARS CoV-2 Variant.

The emergence of new severe acute respiratory syndrome coronavirus-2 (SARS CoV-2) has been a global concern. The B.1.1.7 variant of SARS CoV-2 is reported to cause higher transmission. The study investigates the replication cycle and transcriptional pattern of the B.1.1.7 to hypothesis the possible role of different genes in viral replication. It was observed that the B.1.1.7 variant required a longer maturation time. The transcriptional response demonstrated higher expression of ORF6 and ORF8 compared to nucleocapsid transcript till the eclipse period which might influence higher viral replication. The number of infectious viruses titer is higher in the B.1.1.7, despite a lesser copy number than B.1, indicating higher transmissibility. The experimental evidence published linked ORF6 and ORF8 to play important role in replication and we also observed their higher expression. This leads us to hypothesis the possible role of ORF6 and ORF8 in B.1.1.7 higher replication which causes higher transmission.

Immunogenicity and protective efficacy of inactivated SARS-CoV-2 vaccine candidate, BBV152 in rhesus macaques.

The COVID-19 pandemic is a global health crisis that poses a great challenge to the public health system of affected countries. Safe and effective vaccines are needed to overcome this crisis. Here, we develop and assess the protective efficacy and immunogenicity of an inactivated SARS-CoV-2 vaccine in rhesus macaques. Twenty macaques were divided into four groups of five animals each. One group was administered a placebo, while three groups were immunized with three different vaccine candidates of BBV152 at 0 and 14 days. All the macaques were challenged with SARS-CoV-2 fourteen days after the second dose. The protective response was observed with increasing SARS-CoV-2 specific IgG and neutralizing antibody titers from 3rd-week post-immunization. Viral clearance was observed from bronchoalveolar lavage fluid, nasal swab, throat swab and lung tissues at 7 days post-infection in the vaccinated groups. No evidence of pneumonia was observed by histopathological examination in vaccinated groups, unlike the placebo group which exhibited interstitial pneumonia and localization of viral antigen in the alveolar epithelium and macrophages by immunohistochemistry. This vaccine candidate BBV152 has completed Phase I/II (NCT04471519) clinical trials in India and is presently in phase III, data of this study substantiates the immunogenicity and protective efficacy of the vaccine candidates.

Transcriptome & viral growth analysis of SARS-CoV-2-infected Vero CCL-81 cells.

BACKGROUND & OBJECTIVES: The genome of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), belonging to the family Coronaviridae, encodes for structural, non-structural, and accessory proteins, which are required for replication of the virus. These proteins are encoded by different genes present on the SARS-CoV-2 genome. The expression pattern of these genes in the host cells needs to be assessed. This study was undertaken to understand the transcription pattern of the SARS-CoV-2 genes in the Vero CCL-81 cells during the course of infection. METHODS: Vero CCL-81 cells were infected with the SARS-CoV-2 virus inoculum having a 0.1 multiplicity of infection. The supernatants and cell pellets were harvested after centrifugation at different time points, post-infection. The 50% tissue culture infective dose (TCID50)and cycle threshold (Ct) values of the E and the RdRp-2 genes were calculated. Next-generation sequencing of the harvested sample was carried out to observe the expression pattern of the virus by mapping to the SARS-CoV-2 Wuhan HU-1 reference sequence. The expressions were in terms of the reads per kilobase million (RPKM) values. RESULTS: In the inital six hours post-infection, the copy numbers of E and RdRp-2 genes were approximately constant, which raised 10 log-fold and continued to increase till the 12 h post-infection (hpi). The TCID50 was observed in the supernatant after 7 hpi, indicating the release of the viral progeny. ORF8 and ORF7a, along with the nucleocapsid transcript, were found to express at higher levels. INTERPRETATION & CONCLUSIONS: This study was a step towards understanding the growth kinetics of the SARS-CoV-2 replication cycle. The findings indicated that ORF8 and ORF7b gene transcripts were expressed in higher amounts indicating their essential role in viral replication. Future studies need to be conducted to explore their role in the SARS-CoV-2 replication.