Non-clinical analysis of virus-like particles (VLP) containing SARS-CoV-2 vaccine antigens

This study aimed to evaluate the safety of a vaccine based on virus-like particles (VLPs) containing the SARS-CoV-2 spike protein and another vaccine with additional viral proteins from the membrane, nucleocapsid and envelope coinfection group (BVS:BVN:BVM:BVE), associated or not with the aluminum hydroxide adjuvant, in a repeated dose model in rats. The expression of viral proteins was confirmed, and VLP morphology was verified by transmission electron microscopy. Safety was assessed through parameters such as weight gain, animal behavior, hematological, biochemical and histopathological analyses. The results showed that the vaccine did not cause significant changes in weight gain or animal behavior. However, the addition of aluminum hydroxide led to an increase in lung weight and mild inflammatory infiltration, suggesting that the adjuvant may enhance the immune response but also induce pulmonary adverse effects. Furthermore, alterations in the reproductive system of rats were observed, including degeneration of the germinal epithelium in males and changes in the corpus luteum and granulosa in females, particularly in the groups treated with the adjuvant. These findings contribute to the understanding of the impact of aluminum hydroxide adjuvant on VLP-based vaccines, highlighting the importance of assessing the safety of new vaccine platforms.