Ascorbic Acid and α-Tocopherol in the Inactivated SARS-CoV-2 Vaccine Formulation: Induction of the Th1 Pattern in Aged Mice

Aging is physiologically associated with a decline in the function of the immune system and subsequent susceptibility to infections. Interferon-gamma (IFN-<i>γ</i>), a key element in the activation of cellular immunity, plays an important role in defense against virus infections. Decreased levels of IFN-<i>γ</i> in the elderly may explain their increased risk for viral infectious diseases such as COVID-19. There is accumulating evidence that ascorbic acid (vitamin C [VitC]) and <i>α</i>-tocopherol together help improve the function of the immune system in the elderly, control infections, and decrease the treatment duration. A SARS-CoV-2 strain was isolated from a patient and then cultured in the Vero cell line. The isolated and propagated virus was then inactivated using formalin and purified by the column chromatography. The inactivated SARS-CoV-2 was formulated in the Alum adjuvant combined with VitC or <i>α</i>-tocopherol and/or both of them. The vaccines were injected twice to young and aged C57BL/6 mice. Two weeks later, IFN-<i>γ</i>, IL-4, and IL-2 cytokines were assessed using ELISA Kits. Specific IgG and IgG1/IgG2a were assessed by an in-house ELISA. In addition, the expression of PD1 and <i>TERT</i> genes in the spleen tissue of the mice was measured using real-time PCR. IL-4 and IFN-<i>γ</i> cytokines showed a significant increase in both aged and young mice compared with the Alum-based vaccine. In addition, our results exhibited a significant decrease and increase in specific total IgG and the IgG2a/IgG1 ratio, respectively. Furthermore, the vaccine formulated in <i>α</i>-tocopherol + VitC led to decreased PD1 and increased <i>TERT</i> gene expression levels. In conclusion, our results demonstrated that <i>α</i>-tocopherol + VitC formulated in the inactivated SARS-CoV-2 vaccine led to a shift toward Th1, which may be due to their effect on the physiology of cells, especially aged ones and changing their phenotype toward young cells.