A Dual Drug Sensitive L. major Induces Protection without Lesion in C57BL/6 Mice

Abstract

Leishmaniasis is a major health problem in some endemic areas and yet, no vaccine is available against any form of the disease. Historically, leishmanization (LZ) which is an inoculation of individual with live Leishmania, is the most effective control measure at least against cutaneous leishmaniasis (CL). Due to various reasons, LZ is not used today. Several live attenuated Leishmania have been developed but their use is limited. Previously, we developed a transgenic strain of L. major that harbors two suicide genes tk and cd genes (lmtkcd+/+) for use as a challenge strain in vaccine studies. These genes render the parasite susceptible to Ganciclovir (GCV) and 5-flurocytosine (5-FC). The dual drug sensitive strain of L. major was developed using gene targeting technology using a modified Herpes Simplex Virus thymidine kinase gene (hsv-tk) sensitive to Ganciclovir antibiotic and Saccharomyces cerevisae cytosine deaminase gene (cd sensitive to 5-flurocytosine) that were stably introduced into L. major chromosome. BALB/c mice inoculated with lmtkcd+/+ developed lesions which upon treatment with GCV and 5-FC completely healed. In the current study, the transgenic lmtkcd+/+strain was assessed as a live vaccine model to determine the time necessary to develop a protective immune response. C57BL/6 mice were inoculated with the transgenic lmtkcd+/+strain, and treated at the time of inoculation (day0) or at day 8 after inoculation. Immunized animals were challenged with wild-type L. major, and complete protection was induced in mice that were treated at day 8. The results show that in contrast to leishmanization, in group of mice inoculated with a dual sensitive L. major development and persistence of lesion is not necessary to induce Th1 response and protection.

Vaccination with a Leishmania infantum HSP70-II null mutant confers long-term protective immunity against Leishmania major infection in two mice models

“…This is the case of the LmLpg2 - line that was able to control the pathology in BALB/c mice alleviating disease associated responses, but did not reach the same degree of protection in the resistant model when inoculated in the absence of a cellular inducing adjuvant [28, 29]. As occurred for some subunit [62] or live vaccines [31, 32], LiΔHSP70-II line inoculation was able to induce a robust protection in both murine models of CL. For the susceptible BALB/c mice, we first used the i.v.…”

Cutaneous Infection with Leishmania major Mediates Heterologous Protection against Visceral Infection with Leishmania infantum

“…Numerous genetically modified or avirulent Leishmania strains have been studied in an effort to replicate the protective effect of leishmanization while reducing or controlling for the virulence of the parasite (52, 63-68). How effective these modified strains are compared to leishmanization with wild type L. major has not been addressed, with a single exception (68).…”

“…Numerous genetically modified or avirulent Leishmania strains have been studied in an effort to replicate the protective effect of leishmanization while reducing or controlling for the virulence of the parasite (52, 63-68). How effective these modified strains are compared to leishmanization with wild type L. major has not been addressed, with a single exception (68). Past observations (34, 35, 69, 70) suggest that attenuation resulting in sterile clearance rather than persistence will compromise long-term protection, especially against the more stringent conditions of infected sand fly challenge.…”

Cutaneous Leishmaniasis: Update on Vaccine Development

“…Balb/C mice lesions were cured in 2 weeks in the presence of these drugs, and the transgenic line mediated complete protection when wild-type L major was injected 8 days after vaccination. 72 However, development of drug resistance is a plausible risk associated with the latter vaccination protocol.…”