Advances in the development of a vaccine for the prevention of human leptospirosis: a review.

Leptospirosis is a zoonosis with global distribution caused by spirochetes of the genus Leptospira. In regions with poor sanitation, leptospirosis is considered a neglected disease, resulting in approximately one million cases and thousands of deaths annually. Transmission occurs mainly through contact with the urine of infected rodents, and clinical manifestations range from mild symptoms to the severe form known as Weil's disease. Although licensed vaccines are available, they are targeted at specific risk groups. Bacterins are composed of specific serovars, induce a short-term immune response, and may cause adverse reactions. Advances in molecular biology-including sequencing of the Leptospira genome-have spurred the development of new vaccination strategies, particularly protein subunit vaccines. These vaccines are based on proteins located in the outer membrane of pathogenic Leptospira species. These antigens are expressed in prokaryotic hosts, exhibit high immunogenicity, and, because they are directly exposed to the host's immune system, are considered promising targets for the development of safer and more effective vaccines. Among the main antigens studied, the most notable are LipL32, LipL41, OmpL1, OmpL37, Loa22, LigA, and LigB. However, the identification of antigens capable of inducing an effective immune response while containing conserved regions across different serovars remains a major challenge in developing a universal vaccine against leptospirosis. This review presents the principal outer membrane proteins of pathogenic Leptospira that are considered promising candidates for new vaccine formulations, as well as their role in inducing the immune response in the human host.