key: cord-1018060-jpencoti
authors: Kozlovskaya, L. I.; Gordeychuk, I.; Piniaeva, A.; Kovpak, A.; Shishova, A.; Lunin, A.; Shustova, E.; Apolokhov, V.; Fominykh, K.; Ivin, Y.; Kondrashova, A.; Volok, V.; Tcelykh, I.; Siniugina, A.; Ishmukhametov, A. A.
title: CoviVac vaccination induces production of neutralizing antibodies against Delta and Omicron variants of SARS-CoV-2
date: 2022-02-25
journal: nan
DOI: 10.1101/2022.02.10.22270781
sha: b8227a3abeab89611149fca416376a61e5e30826
doc_id: 1018060
cord_uid: jpencoti

Vaccines are proven to be an effective tool in prophylaxis of severe COVID-19, but emerging mutated SARS-CoV-2 variants constantly challenge vaccines protectivity. We have evaluated the ability of the sera from individuals vaccinated with two variants of inactivated vaccine CoviVac and COVID-19 convalescents (May-December 2020) to neutralize SARS-CoV-2 variants Delta and Omicron. Four groups of serum samples (Covi-Vac vaccinees; COVID-19 convalescents; mice immunized with CoviVac preparations based on prototype B.1.1 strain and Delta variant) were evaluated in virus neutralization test against SARS-CoV-2 heterologous B.1.1 virus, Delta and Omicron variants. CoviVac preparations based on B.1.1 and Delta induced neutralizing antibodies against SARS-CoV-2 B.1.1 and two variants of concern. We observed a decrease in neutralization capacity in the sera from CoviVac (based on B.1.1 strain) vaccinees: 57.1% samples had detectable neutralizing antibodies against Delta and 61.9% against Omicron variants. Sera samples of all (100%) mice immunized with a candidate vaccine based on the SARS-CoV-2 Delta variant strain had neutralizing antibodies against all tested strains.

The severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) was identified in Wuhan, China, at the end of 2019. 23 The virus belongs to the Betacoronavirus genus of Coronaviridae family [1]. Since 2019, SARS-CoV-2 has evolved substantially. 24 A number of SARS-CoV-2 variants of interest (VOI) and variants of concern (VOC) have emerged, such as B.1.1.7 (Alpha) lineage Multiple vaccines based on different platforms have been developed to prevent severe COVID-19, generally showing good 30 safety and varying degrees of efficacy [5] . The emergence of variants that may escape from the immune response has raised concerns 31

[6] regarding the decrease of effectiveness of available vaccines and the threat of increased number of re-infections.

Here, we have evaluated the ability of the sera from COVID-19 convalescents (Russia, May-December 2020) and individuals BALB/c mice were vaccinated with CoviVac preparation based on B.1.1 strain (GISAID EPI_ISL_428851) intramuscularly (0.5 52 ml) twice with 14 days interval, serum samples were collected 7 days after the last immunization for vaccine immunogenicity testing 53 as described previously [7] . The samples were then stored at -20°C and used in the present study.

The CoviVac candidate vaccine based on Delta variant was prepared using the Delta variant strain (GISAID EPI_ISL_8799478) by 55 the same technology as CoviVac [7] . BALB/c mice were vaccinated with the candidate vaccine (0.5 ml) intramuscularly twice with 56 14 days interval, serum samples were collected 7 days after the last immunization for vaccine immunogenicity testing. The samples 57 were then stored at -20°C and used in the present study. VOCs. However, the nAB titers against VOCs were significantly lower, which supports the previously published data. perpetuity. preprint (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in 

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