Using an Aluminum Hydroxide-Chitosan Matrix Increased the Vaccine Potential and Immune Response of Mice against Multi-Drug-Resistant Acinetobacter baumannii.

Acinetobacter baumannii is a Gram-negative, immobile, aerobic nosocomial opportunistic coccobacillus that causes pneumonia, septicemia, and urinary tract infections in immunosuppressed patients. There are no commercially available alternative antimicrobials, and multi-drug resistance is an urgent concern that requires emergency measures and new therapeutic strategies. This study evaluated a multi-drug-resistant A. baumannii whole-cell vaccine, inactivated and adsorbed on an aluminum hydroxide-chitosan (mAhC) matrix, in an A. baumannii sepsis model in immunosuppressed mice by cyclophosphamide (CY). CY-treated mice were divided into immunized, non-immunized, and adjuvant-inoculated groups. Three vaccine doses were given at 0D, 14D, and 28D, followed by a lethal dose of 4.0 × 108 CFU/mL of A. baumannii. Immunized CY-treated mice underwent a significant humoral response, with the highest IgG levels and a higher survival rate (85%); this differed from the non-immunized CY-treated mice, none of whom survived (p < 0.001), and from the adjuvant group, with 45% survival (p < 0.05). Histological data revealed the evident expansion of white spleen pulp from immunized CY-treated mice, whereas, in non-immunized and adjuvanted CY-treated mice, there was more significant organ tissue damage. Our results confirmed the proof-of-concept of the immune response and vaccine protection in a sepsis model in CY-treated mice, contributing to the advancement of new alternatives for protection against A. baumannii infections.

Inactivated alpha toxin from Clostridium novyi type B in nano-emulsion protect partially protects Swiss mice from lethal alpha toxin challenge.

Nano-emulsions are promising carriers for antigen delivery. Here, we evaluated the efficacy of a water-oil nano-emulsion containing concentrated, inactivated Clostridium novyi (C. novyi) type B supernatant culture (nano-iCnB) in protecting Swiss mice against a lethal dose of alpha toxin concentrated extract. Proteins were confirmed in the nano-iCnB and their stabilities were determined according physical parameters such as Zeta Potential (ZP). Biochemical, hematological parameters and morphological appearance of liver, spleen and thigh muscle alterations were examined to determine the safety of the compound. Partial protection against lethal doses was achieved in immunized mice despite low IgG titers. These data suggest that our nano-emulsion is a simple and efficient method of promoting antigen delivery for toxin-related diseases.