DNA Immunization with the Gene Encoding P4 Nuclease ofLeishmania amazonensisProtects Mice against Cutaneous Leishmaniasis

Abstract

Infection with the protozoan parasiteLeishmania amazonensiscan cause diverse clinical forms of leishmaniasis. Immunization with purified P4 nuclease protein has been shown to elicit a protective response in mice challenged withL. amazonensisandL. pifanoi.To explore the potential of a DNA-based vaccine, we tested theL. amazonensisgene encoding P4 nuclease as well as adjuvant constructs encoding murine interleukin-12 (IL-12) andL. amazonensisHSP70. Susceptible BALB/c mice were immunized with the DNA encoding P4 alone, P4/IL-12, or P4/HSP70 prior to challenge withL. amazonensispromastigotes. Mice given P4/IL-12 exhibited no lesion development and had a 3- to 4-log reduction in tissue parasite burdens compared to controls. This protection corresponded to significant increases in gamma interferon and tumor necrosis factor alpha production and a reduction in parasite-specific immunoglobulin G1, suggesting an enhancement in Th1 responses. Moreover, we immunized mice with theL. amazonensisvaccines to determine if this vaccine regimen could provide cross-protection against a genetically diverse species,L. major. While the P4/HSP70 vaccine led to self-healing lesions, the P4/IL-12 vaccine provided negligible protection againstL. majorinfection. This is the first report of successful use of a DNA vaccine to induce protection againstL. amazonensisinfection. Additionally, our results indicate that different vaccine combinations, including DNA encoding P4, HSP70, or IL-12, can provide significant protection against both Old World and New World cutaneous leishmaniasis.