USJ researchers have investigated the immune responses of the first dose (rAd26-S) of the Gam-COVID-Vac, which is also known as Sputnik light, in a Sri Lankan population, 4 weeks after receiving the first dose and compared the immune responses with the previously published data following AZD1222, which is another adenovirus vector vaccine. The Gam-COVID-19 first dose (rAd26-S) induced seroconversion rates in 88.7% of individuals 4 weeks following the vaccine, with significantly lower seroconversion rates in the elderly in a Sri Lankan population. ACE2 receptor blocking antibody responses were seen in 82.6% of individuals, with levels Page 9/15 significantly lower than after a single dose of AZD1222 and following natural infection. While the antibody responses to the RBD by HAT were similar to AZD1222, the ex vivo IFNγ ELISpot responses were significantly lower. The findings suggest that the two Gam-COVID-19 doses using heterologous adenoviruses may be of particular importance in certain populations
As the first dose of Gam-COVID-Vac (Sputnik light), is currently used as a single dose vaccine in some countries, researchers investigated the immunogenicity of this at 4 weeks (327 naïve individuals). 88.7% seroconverted, with significantly lower seroconversion rates in those over 60 years (p = 0.004) and significantly lower than previously seen with AZD1222 (p = 0.018). 82.6% developed ACE2 receptor blocking antibodies, although levels were significantly lower than following natural infection (p = 0.0009) and a single dose of AZD1222 (p < 0.0001). Similar titres of antibodies were observed to the receptor binding domain of WT, B.1.1.7 and B.1.617.2 compared to AZD1222, while the levels for B.1.351 were significantly higher (p = 0.006) for Gam-COVID-Vac. 30% developed ex vivo IFNγ ELISpot responses (significantly lower than AZD1222), and high frequency of CD107a expressing T cells along with memory B cell responses. Although single dose of Gam-COVID-Vac was highly immunogenic, administration of a second dose is likely to be beneficial.
The research was carried out by a team of world renowned scientists. The research team included scientists from the Allergy, Immunology and Cell Biology Unit, Department of Immunology Molecular and Molecular Medicine, including Prof. Neelika Malavige, Dr. Chandima Jeewandara, researchers from University of Oxford including Prof. Graham Ogg, Prof. Alain Townsend and researchers from Ministry of Health Sri Lanka. The World Health Organization, UK Medical Research Council, the Foreign and Commonwealth Office and the NIH, USA (grant number 5U01AI151788-02 ). T.K.T. funded by the Townsend-Jeantet Charitable Trust (charity number 1011770) and the EPA Cephalosporin Early Career Researcher Fund supported the research. A.T. are funded by the Chinese Academy of Medical Sciences (CAMS) Innovation Fund for Medical Science (CIFMS), China (grant no. 2018-I2M-2-002). The donations by WBP, EGB and ANB to the Townsend-Jeantet Prize Trust Charity No 1011770 have supported the production and distribution of the HAT test.
Read the full Research Article : https://www.researchsquare.com/article/rs-787293/v1