Comparing the immune response of mRNA-based, inactivated COVID-19 and seasonal influenza vaccines and their effects on submandibular glands and associated lymph nodes in albino rats: biochemical, histological and immunohistochemical analysis

Objectives

This research attempted to compare the immune response of Pfizer, Sinovac, and Influvac tetra vaccines in addition to comparing their effects on the submandibular glands (SMGs) and associated lymph nodes in albino rats.

Material and Methods

Forty rats were allocated into four groups: group Ι (control), group II (Pfizer), group III (Sinovac) and group IV (Influvac tetra). Serum immunoglobulins G and A (IgG and IgA) were measured. Then, animals were sacrificed. Histological and immunohistochemical examinations were performed on the dissected SMGs and associated lymph nodes.

Results

The Pfizer group had the highest mean IgG and IgA readings, followed by the Sinovac, Influenza and control groups, with a significant variation between every 2 groups. Histopathological examination of the SMGs of all groups showed nearly normal gland architecture resembling the control group. However, mild changes were observed in vaccinated groups. Lymph nodes’ histopathological examination revealed inactive primary lymphoid follicles in the control group. However, all vaccinated groups revealed active lymph nodes with secondary lymphoid follicles. Regarding the area percentage of CD3 immunoexpression, the greatest value was reported in Pfizer group, followed by Sinovac, Influenza and control groups, with a significant difference between Pfizer and both Sinovac and influenza groups. However, no substantial variation was observed between Sinovac and Influenza groups.

Conclusion

All vaccines administered were effective. The Pfizer vaccination had the most T cells and the highest serum concentrations of IgG and IgA. All vaccines generally had a satisfactory safety profile with no impact on salivary gland histology.