Evaluation of the effects of cisplatin and the cisplatin-alum mixture as adjuvants for increasing the efficacy of vaccination against Salmonella typhimurium in Balb/c mice

 Salmonella typhimurium (S. typhimurium) is one of the causative agents of intestinal and extraintestinal infections in humans. Symptoms of the mouse infection by this bacterium mimic typhoid fever in humans. Adjuvants are compounds that enhance the effectiveness of vaccines in combination with them. Alum as an adjuvant causes a shift towards Th2 immune and strengthens the humoral immunity responses. Cisplatin is a highly effective anti-tumor drug that stimulates immune responses by activating macrophages and other immune cells and is used in tumor immunotherapy. This study aimed to investigate the role of cisplatin and the cisplatin-alum mixture as adjuvants to increase the efficacy of vaccination against S. typhimurium in Balb/c mice.

 Male BALB/c mice were divided into five groups. Mice in the experimental groups received either the HKST vaccine alone or in combination with the adjuvants alum, cisplatin, or the cisplatin-alum. Mice in the negative control group received phosphate-buffered saline. All mice were immunized two times on days 0 and 14. Two weeks after the last immunization, immune responses to S. typhimurium were assessed by measuring the survival rate after challenge with a lethal dose of bacterium, bacterial load in the liver, interferon-gamma, and S. typhimurium-specific IgG1 and IgG2a production. 

 The numbers of colonies in the spleen and liver cultures in all dilutions were significantly lower in cisplatin-vaccine, and cisplatin-alum vaccine immunized mice. The average rate of specific IgG2a was higher in the same groups compared to other groups. The survival rate in alum-vaccine, cisplatin-vaccine, and cisplatin-alum-vaccine groups was significantly higher than in the control group. The average rate of Interferon-gamma in cisplatin-vaccine and cisplatin- alum vaccine groups, was significantly higher than other groups.

 This study is the first to determine the role of administrating cisplatin and alum-cisplatin mixture on increasing the efficiency of the HKST vaccine in a mouse model. This study confirmed the role of cisplatin and cisplatin-alum mixture in increasing the efficiency of the HKST vaccine by using different experiments.