3.4 Influenza/SARS-CoV-2 Omicron Subunit Combined Vaccine Induced High Titers of Neutralizing Antibodies against SARS-CoV-2 Omicron BA.5 Pseudovirus and Effectively Reduced the Viral Load of Authentic SARS-CoV-2 Omicron BA.5.2 in the Cell Culture Supernatants
We next detected the neutralizing antibodies of immunized mouse sera collected on days 21 and 35 against pseudotyped SARS-CoV-2 Omicron BA.5 variant. As shown in Figure 5A, Omicron S and HA+Omicron S immunized mouse sera collected on day 21 elicited high titers of Omicron BA.5-specific neutralizing antibodies (2577 and 1977, respectively). The neutralizing antibody titers in the sera of mice immunized with Omicron S or HA+Omicron S collected on day 35 increased significantly (8924 and 6679, respectively) (Figure 5B). We further detected the antiviral effect of mouse sera collected on day 35 against SARS-CoV-2 Omicron BA.5.2 strain on VeroE6-TMPRSS2 cells. As shown in Figure 5C, both Omicron S and HA+Omicron S immunized mouse sera effectively reduced the viral load of SARS-CoV-2 Omicron BA.5.2 in cell culture supernatants on day 35, and such reduction was dose-dependent.