Needle-free injection system delivery of ZyCoV-D DNA vaccine demonstrated improved immunogenicity and protective efficacy in rhesus macaques against SARS-CoV-2

The apprehension of needles related to injection site pain, risk of transmitting bloodborne pathogens, and effective mass immunization have led to the development of a needle-free injection system (NFIS). Here, we evaluated the efficacy of the NFIS and needle injection system (NIS) for the delivery and immunogenicity of DNA vaccine candidate ZyCoV-D in rhesus macaques against SARS-CoV-2 infection. Briefly, 20 rhesus macaques were divided into 5 groups (4 animals each), that is, I (1 mg dose by NIS), II (2 mg dose by NIS), III (1 mg dose by NFIS), IV (2 mg dose by NFIS) and V (phosphate-buffer saline [PBS]). The macaques were immunized with the vaccine candidates/PBS intradermally on Days 0, 28, and 56. Subsequently, the animals were challenged with live SARS-CoV-2 after 15 weeks of the first immunization. Blood, nasal swab, throat swab, and bronchoalveolar lavage fluid specimens were collected on 0, 1, 3, 5, and 7 days post infection from each animal to determine immune response and viral clearance. Among all the five groups, 2 mg dose by NFIS elicited significant titers of IgG and neutralizing antibody after immunization with enhancement in their titers postvirus challenge. Besides this, it also induced increased lymphocyte proliferation and cytokine response. The minimal viral load post-SARS-CoV-2 challenge and significant immune response in the immunized animals demonstrated the efficiency of NFIS in delivering 2 mg ZyCoV-D vaccine candidate.

Detection and isolation of SARS-CoV-2 Eta variant from the international travelers and local residents of India

International travel has been the major source for the rapid spread of new SARS‐CoV‐2 variants across the globe. During SARS‐CoV‐2 genomic surveillance, a total of 212 SARS‐CoV‐2 positive clinical specimens were sequenced using next‐generation sequencing. A complete SARS‐CoV‐2 genome could be retrieved from 90 clinical specimens. Of them, 14 sequences belonged to the Eta variant from clinical specimens of international travelers (n = 12) and local residents (n = 2) of India, and 76 belonged to other SARS‐CoV‐2 variants. Of all the Eta‐positive specimens, the virus isolates were obtained from the clinical specimens of six international travelers. Many variants of interest have been found to cause substantial community transmission or cluster infections. The detection of this variant with lethal E484K mutation across the globe and India necessitates persistent genomic surveillance of the SARS‐CoV‐2 variants, which would aid in taking preventive action.

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 3^rd-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.

Isolation and characterization of the new SARS-CoV-2 variant in travellers from the United Kingdom to India: VUI-202012/01 of the B.1.1.7 lineage

We have isolated the new severe acute respiratory syndrome coronavirus-2 variant of concern 202 012/01 from the positive coronavirus disease 2019 cases that travelled from the UK to India in the month of December 2020. This emphasizes the need for the strengthened surveillance system to limit the local transmission of this new variant.

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 (C_t) 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.