Purpose: The objective of the present study was to evaluate the immune-enhancing potential of Salmonella typhimurium outer membrane protein (OMP) and alum as adjuvants towards inactivated Vero cells rabies vaccine (FRV/K2). Materials and Methods: Six groups of female Sprague Dawley albino rats (10/group) were used in the evaluation of immunogenicity and safety of vaccines and adjuvants. Total immunoglobulin G secreted interferon-gamma (IFN-γ), and the percentage of proliferated CD4+ and CD8+ T cells were measured. Biochemical analysis and histopathological examination were used to test safety profiles. Results: OMP adjuvanted rabies vaccine (FRV/K2+OMP) (OMP combined locally prepared vaccine) induced significantly higher neutralizing antibodies on day 21 post-vaccination relative to free (FRV/K2) vaccine and alum adsorbed vaccine (FRV/K2+alum) (alum adsorbed locally prepared vaccine). (FRV/K2+OMP) induced a significantly higher level of IFN-γ on day 14 post-vaccination. CD8+ T cells were significantly higher post-vaccination with reference (RV), free (FRV/K2), and (FRV/K2+OMP) than (FRV/K2+alum). On the contrary, CD4+ T cells were significantly elevated post-vaccination with (FRV/K2+alum) at p<0.05. Biochemical analysis and histopathological examination revealed that OMP could be used safely as an adjuvant for the development of more effective rabies vaccines. Conclusion Outer membrane proteins adjuvanted rabies vaccines would be beneficial to induce rapid neutralizing antibodies and essential cytokines.

Purpose: The present study aimed to compare the immune-enhancing potential of gold nanoparticles (AuNPs) to Alum against rabies vaccine and the related immunological, physiological, and histopathological effects. Materials and Methods: Alum and AuNPs sole and in combination with rabies vaccine were used at 0.35 mg/mL and 40 nM/mL, respectively. Rats used were categorized into six groups (20/each): control rats, rabies vaccine, aluminum phosphate gel, rabies vaccine adsorbed to Alum, AuNPs, and rabies vaccine adjuvant AuNPs. Results: Liver and kidney functions were in the normal range after AuNPs and Alum adjuvanted vaccine compared to control. Interleukin-6 and interferon-γ levels were significantly increased in groups immunized with Alum and AuNPs adjuvanted vaccine, the peak level was in the case of AuNP adjuvanted vaccine on the 14th day. Ninety days post-vaccination, total immunoglobulin G (IgG) against adjuvanted rabies vaccine showed a significantly elevated anti-rabies IgG with AuNPs and Alum adsorbed vaccine compared with unadjuvanted one. The total antioxidant capacity, malondialdehyde (MDA) levels, superoxide dismutase, and glutathione peroxidase activities were significantly increased post-adjuvanted AuNPs adjuvanted vaccine vaccination than in Alum adsorbed vaccine, while MDA was significantly decreased. The histopathological examination revealed detectable alterations post-AuNPs and Alum adjuvanted vaccine immunization compared with liver and kidney profiles post-administration of unadjuvanted and non-immunized groups, meanwhile, splenic tissue revealed hyperplasia of lymphoid follicles indicating increased immune reactivity. Conclusion The AuNPs are promising enhancers of the immune response as Alum, and the undesirable effects of AuNPs could be managed by using suitable sizes, shapes, and concentrations.

Purpose: One of the essential goals regarding the successful control of rabies infection is the development of a safe, effective, and inexpensive vaccine. the current study aimed to evaluate the inactivation potential of β-propiolactone (βPL), binary ethyleneimine (BEI), and hydrogen peroxide (H2O2). Materials and Methods: Estimating the inactivation kinetics of βPL, BEI, and H2O2 revealed that the tested inactivants could completely and irreversibly inactivate rabies virus within 2, 12, and 4 hours, respectively while maintaining its viral immunogenicity. The potency of βPL, BEI, and H2O2 inactivated vaccines was higher than the World Health Organization acceptance limit and were in the order of 3.75, 4.21, and 3.64 IU/mL, respectively. Monitoring the humoral and cellular immunity elicited post-immunization using Staphylococcus aureus derived hyaluronic acid (HA) and bacillus Calmette-Guérin purified protein derivative (PPD) adjuvanted rabies vaccine candidates were carried out using enzyme-linked immunosorbent assay. Results: Results: demonstrated that both adjuvants could progressively enhance the release of anti-rabies total immunoglobulin G as well as the pro-inflammatory mediators (interferon-gamma and interleukin-5) relative to time. However, a higher immune response was developed in the case of HA adjuvanted rabies vaccine compared to PPD adjuvanted one. The harmful consequences of the tested adjuvants were considered via investigating the histopathological changes in the tissues of the immunized rats using hematoxylin and eosin stain. Lower adverse effects were observed post-vaccination with HA and PPD adjuvanted vaccines compared to that detected following administration of the currently used alum as standard adjuvant. Conclusion Our findings suggested that HA and PPD could serve as a promising platform for the development of newly adjuvanted rabies vaccines with elevated immune enhancing potentials and lower risk of health hazards.