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

Abstract

Infection with the protozoan parasite Leishmania amazonensis can cause diverse clinical forms of leishmaniasis. Immunization with purified P4 nuclease protein has been shown to elicit a protective response in mice challenged with L. amazonensis and L. pifanoi. To explore the potential of a DNA-based vaccine, we tested the L. amazonensis gene encoding P4 nuclease as well as adjuvant constructs encoding murine interleukin-12 (IL-12) and L. amazonensis HSP70. Susceptible BALB/c mice were immunized with the DNA encoding P4 alone, P4/IL-12, or P4/HSP70 prior to challenge with L. amazonensis promastigotes. 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 the L. amazonensis vaccines 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 against L. major infection. This is the first report of successful use of a DNA vaccine to induce protection against L. amazonensis infection. 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.Leishmaniasis is widespread in over 88 countries. It is estimated that 350 million people live in areas where it is endemic, with 12 million people infected, and that approximately 1.5 million new cases occur each year (65). Current control measures rely on chemotherapy, vector control, and control of reservoir host populations. The chemotherapeutic agents used presently are inadequate, expensive, and often toxic. Due to the existing problems associated with leishmaniasis and the high incidence of infection, the World Health Organization has made it a major goal to develop an effective and affordable vaccine against leishmaniasis.The different Leishmania species cause a broad spectrum of human diseases. L. amazonensis is known to be associated with cutaneous, diffuse cutaneous, and visceral leishmaniasis in South and Central America. The pathological mechanisms responsible for the variable outcomes of infection in humans are not fully understood; however, it is generally agreed that longlasting immunity against reinfection can be developed in cutaneous leishmaniasis patients. Several vaccination trials have demonstrated that killed L. amazonensis can induce protection from natural infection (3,18,42,46,63). However, the efficacy of heat-killed vaccines against Leishmania has been extremely low (36) or highly variable within the same study (47,55). Live parasites have been used as a vaccine strategy, and although they are highly effective in indu...

Intranasal Vaccination against Cutaneous Leishmaniasis with a Particulated Leishmanial Antigen or DNA Encoding LACK

“…Previous studies have demonstrated the efficacy of parenteral DNA vaccines against murine leishmaniasis (4,12,28,34,39), but this is the first study to report the efficacy of a mucosal DNA vaccine for this disease. Altogether, the work presented here demonstrates the feasibility of using the nasal mucosa for effective delivery of both crude antigens and DNA against cutaneous leishmaniasis.…”

DNA Immunization with Na + -K + ATPase ( Sseat-6 ) Induces Protective Immunity to Larval Strongyloides stercoralis in Mice

“…An alternative vaccination approach has been to immunize mice with DNA, where the protein product is produced in vivo from the plasmid DNA. This approach has been used successfully against both protozoan (7,16,29) and helminth (10,46,53,54) infections resulting in measurable immune responses, some of which mediate protective immunity.…”

Cross-Protective Efficacy of a ProphylacticLeishmania donovaniDNA Vaccine against Visceral and Cutaneous Murine Leishmaniasis

“…For example, a DNA vaccine encoding the highly conserved LACK antigen cannot induce cross-species protection (16,29), whereas L. donovani promastigote antigen dp72 can induce protection against both L. donovani and L. major in mice (43). A DNA vaccine encoding L. amazonensis P4 nuclease can also protect significantly against L. amazonensis and L. major, but different adjuvants (interleukin-12-or HSP70-encoding plasmids) are required to obtain such protection (8).…”