Immunogenicity Evaluating of the Multivalent COVID-19 Inactivated Vaccine against the SARS-CoV-2 Variants

Abstract

It has been reported that the novel coronavirus (COVID-19) has caused more than 286 million cases and 5.4 million deaths to date. Several strategies have been implemented globally, such as social distancing and the development of the vaccines. Several severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants have appeared, such as Alpha, Beta, Gamma, Delta, and Omicron. With the rapid spread of the novel coronavirus and the rapidly changing mutants, the development of a broad-spectrum multivalent vaccine is considered to be the most effective way to defend against the constantly mutating virus. Here, we evaluated the immunogenicity of the multivalent COVID-19 inactivated vaccine. Mice were immunized by multivalent COVID-19 inactivated vaccine, and the neutralizing antibodies in serum were analyzed. The results show that HB02 + Delta + Omicron trivalent vaccine could provide broad spectrum protection against HB02, Beta, Delta, and Omicron virus. Additionally, the different multivalent COVID-19 inactivated vaccines could enhance cellular immunity. Together, our findings suggest that the multivalent COVID-19 inactivated vaccine can provide broad spectrum protection against HB02 and other virus variants in humoral and cellular immunity, providing new ideas for the development of a broad-spectrum COVID-19 vaccine.

Keywords: Beta; Delta; HB02; Omicron; SARS-CoV-2; immunogenicity; multivalent inactivated vaccines.

Figure 1

The neutralizing antibody titers of the HB02, HB02 + Delta, and HB02 + Beta + Delta vaccines against different variants. (A) Schematic diagram of the immunization program—the BALB/c mice were injected with different vaccines on day 0 and day 21, and blood was collected on days 28/35/42 after immunization. (B) The neutralizing antibody titers (NAb Titer) at 28/35/42 days after the administration of the vaccine against different variants were tested by means of the microplate micro-cytopathogenic efficiency (CPE) method. (C) The NAb titers of the HB02, HB02 + Delta, and HB02 + Beta + Delta vaccines against the Beta variant on days 0/28/35/42 were obtained by means of the microtitration method (n = 7–10). (D) The Nab titers of the HB02, HB02 + Delta, and HB02 + Beta + Delta vaccines against the HB02 variant on days 0/28/35/42 were obtained by means of the microtitration method (n = 7–10). (E) The NAb titers of the HB02, HB02 + Delta, and HB02 + Beta + Delta vaccines against the Delta variant on days 0/28/35/42 were obtained by means of the microtitration method (n = 7–10). (F) The NAb titers of the HB02, HB02 + Delta, and HB02 + Beta + Delta vaccines against the Beta variant on day 42 were obtained by means of the microtitration method (n = 7–10). (G) The NAb titers of the HB02, HB02 + Delta, and HB02 + Beta + Delta vaccines against the HB02 variant on day 42 were obtained by means of the microtitration method (n = 7–10). (H) The NAb titers of the HB02, HB02 + Delta, and HB02 + Beta + Delta vaccines against the Delta variant on day 42 were obtained by means of the microtitration method (n = 7–10).

Figure 2

Comparison of the broad protection ability of the Omicron + Delta + Beta + HB02, Delta + Beta + HB02, and HB02 + Omicron vaccines. (A) The GMTs of Omicron + Delta + Beta + HB02, Delta + Beta + HB02, and HB02 + Omicron vaccines against the Beta variant on days 0/28/35/42 were obtained by means of the microtitration method (n = 10). (B) The GMTs of the Omicron + Delta + Beta + HB02, Delta + Beta + HB02, and HB02 + Omicron vaccines against the HB02 variant on days 0/28/35/42 were obtained by means of the microtitration method (n = 7–10). (C) The GMTs of the Omicron + Delta + Beta + HB02, Delta + Beta + HB02, and HB02 + Omicron vaccines against the Delta variant on days 0/28/35/42 were obtained by means of the microtitration method (n = 10). (D) The NAb titers of the Omicron + Delta + Beta + HB02, Delta + Beta + HB02, and HB02 + Omicron vaccines against the Beta variant on day 42 were obtained by means of the microtitration method (n = 10). (E) The NAb titers of the Omicron + Delta + Beta + HB02, Delta + Beta + HB02, and HB02 + Omicron vaccines against the HB02 variant on day 42 were obtained by means of the microtitration method (n = 10). (F) The NAb titers of the Omicron + Delta + Beta + HB02, Delta + Beta + HB02, and HB02 + Omicron vaccines against the Delta variant on day 42 were obtained by means of the microtitration method (n = 10). (G) The GMTs of the Omicron + Delta + Beta + HB02, Delta + Beta + HB02, and HB02 + Omicron vaccines against the Omicron variant on days 0/28/35/42 were obtained by means of the microtitration method (n = 10). (H) The NAb titers of the Omicron + Delta + Beta + HB02, Delta + Beta + HB02, and HB02 + Omicron vaccines against the Omicron variant on day 42 were obtained by means of the microtitration method (n = 7–10).

Figure 3

Cellular response of splenocytes in mice immunized with different vaccines. (A,C) The percentage of GCB cells was analyzed by means of flow cytometry in mice immunized with the HB02 + Delta, HB02 + Beta + Delta, and HB02 vaccines or the control group after 42 days (n = 5–6), with GCB cells gated in live CD45 + B220 +; (B,D) The percentage of IFN-γ-expressing T cells was analyzed by means of flow cytometry in mice immunized with HB02 + Delta, HB02 + Beta + Delta, and HB02 vaccines or the control group after 42 days (n = 5–6), with IFN-γ-expressing T cell gated in live CD45 + CD90 +. Error bars represent SEM. * p < 0.05; ** p < 0.01; *** p < 0.001 ((A–D), Mann–Whitney test). See also Figure S1.

Figure 4

Cytokine response of splenocytes in mice immunized with different vaccines. Mice were immunized with different vaccines, and splenocytes were collected on day 42 post immunization. (A,B) Virus-specific IFN-γ and IL-4 in spleens were measured by means of the ELISPOT assay (n = 5–6) after injection of the HB02 + Delta, HB02 + Beta + Delta, and HB02 vaccines or the control group. (C,D) Virus-specific IFN-γ and IL-4 in spleens were measured by means of the ELISPOT assay (n = 5–6) after injection of the HB02 + Omicron, HB02 + Omicron + Delta, and HB02 + Omicron + Delta + Beta vaccines or the control group. Error bars represent SEM. ** p < 0.01; *** p < 0.001 ((A–D), Mann–Whitney test).