The Evolution of Vaccines Development across Salmonella Serovars among Animal Hosts: A Systematic Review

Abstract

Salmonella is a significant zoonotic foodborne pathogen, and the global spread of multidrug-resistant (MDR) strains poses substantial challenges, necessitating alternatives to antibiotics. Among these alternatives, vaccines protect the community against infectious diseases effectively. This review aims to summarize the efficacy of developed Salmonella vaccines evaluated in various animal hosts and highlight key transitions for future vaccine studies. A total of 3221 studies retrieved from Web of Science, Google Scholar, and PubMed/Medline databases between 1970 and 2023 were evaluated. One hundred twenty-seven qualified studies discussed the vaccine efficacy against typhoidal and nontyphoidal serovars, including live-attenuated vaccines, killed inactivated vaccines, outer membrane vesicles, outer membrane complexes, conjugate vaccines, subunit vaccines, and the reverse vaccinology approach in different animal hosts. The most efficacious vaccine antigen candidate found was recombinant heat shock protein (rHsp60) with an incomplete Freund's adjuvant evaluated in a murine model. Overall, bacterial ghost vaccine candidates demonstrated the highest efficacy at 91.25% (95% CI = 83.69-96.67), followed by the reverse vaccinology approach at 83.46% (95% CI = 68.21-94.1) across animal hosts. More than 70% of vaccine studies showed significant production of immune responses, including humoral and cellular, against Salmonella infection. Collectively, the use of innovative methods rather than traditional approaches for the development of new effective vaccines is crucial and warrants in-depth studies.

Keywords: Salmonellosis; bacterial vaccines; conventional vaccine technologies; immunotherapy; infectious diseases; reverse vaccinology.

Figure 1

A simplified PRISMA diagram of methodology. A total of 3221 articles from different animal models were identified by our search strategy from different online databases (i.e., PubMed, ScienceDirect, and Google Scholar). * n is the no. of studies.

Figure 2

Summary of vaccine studies used in this review. (a) Proportion of vaccine studies according to animal models; (b) types of different Salmonella serovars used in different vaccine studies; (c) types of vaccine strategies used in this study.

Figure 3

Transition in the development of different vaccine candidates across various animal models from 1970 to 2023.

Figure 4

Efficacy of different vaccine candidates in various animal models. Here, the small square represents the reported efficacy after vaccination. All data were taken from the articles included in this systematic review. The 95% confidence intervals were not evenly distributed because the response levels for all vaccines were not the same. There is only one reverse vaccinology study in the chicken model, so we were not able to find the upper and lower limits of 95% CI; thus, it was not reported in the figure.