Comparative pathogenicity of BA.2.12, BA.5.2 and XBB.1 with the Delta variant in Syrian hamsters.

Omicron variant is evolving into numerous sub variants with time and the information on the characteristics of these newly evolving variants are scant. Here we performed a pathogenicity evaluation of Omicron sub variants BA.2.12, BA.5.2 and XBB.1 against the Delta variant in 6-8-week-old Syrian hamster model. Body weight change, viral load in respiratory organs by real time RT-PCR/titration, cytokine mRNA quantification and histopathological evaluation of the lungs were performed. The intranasal infection of the BA.2.12, BA.5.2 and XBB.1 variants in hamster model resulted in body weight loss/reduced weight gain, inflammatory cytokine response and interstitial pneumonia with lesser severity compared to the Delta variant infection. Among the variants studied, BA.2.12 and XBB.1 showed lesser viral shedding through the upper respiratory tract, whereas the BA.5.2 showed comparable viral RNA shedding as that of the Delta variant. The study shows that the Omicron BA.2 sub variants may show difference in disease severity and transmissibility amongst each other whereas the overall disease severity of the Omicron sub variants studied were less compared to the Delta variant. The evolving Omicron sub variants and recombinants should be monitored for their properties.

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.

Serosurvey for Nipah virus in bat population of southern part of India.

Nipah virus (NiV) is one of the priority pathogens with pandemic potential. Though the spread is far slower than SARS-CoV-2, case fatality is the biggest concern. Fruit bats belonging to genus Pteropus are identified to be the main reservoir of the virus causing sporadic cases and outbreaks in Malaysia, Bangladesh and India. The sudden emergence of Nipah in Kerala, India during 2018-2019 has been astonishing with respect to its introduction in the unaffected areas. With this, active Nipah virus surveillance was conducted among bat populations in Southern part of India viz., Karnataka, Kerala, Tamil Nadu, Telangana, Puducherry and Odisha during January-November 2019. Throat swabs/rectal swabs (n = 573) collected from Pteropus medius and Rousettus leschenaultii bat species and sera of Pteropus medius bats (n = 255) were screened to detect the presence of Nipah viral RNA and anti-Nipah IgG antibodies respectively. Of 255 P. medius bats sera samples, 51 bats (20%) captured from Karnataka, Kerala, Tamil Nadu and Puducherry demonstrated presence of anti-Nipah IgG antibodies. However, the presence of virus couldn't be detected in any of the bat specimens. The recent emergence of Nipah virus in Kerala in September 2021 warrants further surveillance of Nipah virus among bat populations from the affected and remaining states of India.

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.

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.

Neutralizing antibody responses to SARS-CoV-2 in COVID-19 patients.

BACKGROUND & OBJECTIVES: The global pandemic caused by SARS-CoV-2 virus has challenged public health system worldwide due to the unavailability of approved preventive and therapeutic options. Identification of neutralizing antibodies (NAb) and understanding their role is important. However, the data on kinetics of NAb response among COVID-19 patients are unclear. To understand the NAb response in COVID-19 patients, we compared the findings of microneutralization test (MNT) and plaque reduction neutralization test (PRNT) for the SARS-CoV-2. Further, the kinetics of NAb response among COVID-19 patients was assessed. METHODS: A total of 343 blood samples (89 positive, 58 negative for SARS-CoV-2 and 17 cross-reactive and 179 serum from healthy individuals) were collected and tested by MNT and PRNT. SARS-CoV-2 virus was prepared by propagating the virus in Vero CCL-81 cells. The intra-class correlation was calculated to assess the correlation between MNT and PRNT. The neutralizing endpoint as the reduction in the number of plaque count by 90 per cent (PRNT90) was also calculated. RESULTS: The analysis of MNT and PRNT quantitative results indicated that the intra-class correlation was 0.520. Of the 89 confirmed COVID-19 patients, 64 (71.9%) showed NAb response. INTERPRETATION & CONCLUSIONS: The results of MNT and PRNT were specific with no cross-reactivity. In the early stages of infection, the NAb response was observed with variable antibody kinetics. The neutralization assays can be used for titration of NAb in recovered/vaccinated or infected COVID-19 patients.

Study of Kyasanur forest disease viremia, antibody kinetics, and virus infection in target organs of Macaca radiata.

The present manuscript deals with experimental infections of bonnet macaques (Macaca radiata) to study disease progression for better insights into the Kyasanur Forest Disease (KFD) pathogenesis and transmission. Experimentally, 10 monkeys were inoculated with KFD virus (KFDV) (high or low dose) and were regularly monitored and sampled for various body fluids and tissues at preset time points. We found that only 2 out of the 10 animals showed marked clinical signs becoming moribund, both in the low dose group, even though viremia, virus shedding in the secretions and excretions were evident in all inoculated monkeys. Anti-KFDV immunoglobulin (Ig)M antibody response was observed around a week after inoculation and anti-KFDV IgG antibody response after two weeks. Anaemia, leucopenia, thrombocytopenia, monocytosis, increase in average clotting time, and reduction in the serum protein levels were evident. The virus could be re-isolated from the skin during the viremic period. The persistence of viral RNA in the gastrointestinal tract and lymph nodes was seen up to 53 and 81 days respectively. Neuro-invasion was observed only in moribund macaques. Re-challenge with the virus after 21 days of initial inoculation in a monkey did not result in virus shedding or immune response boosting.