Induction of immunogenicity by live attenuated Leishmania donovani centrin deleted parasites in dogs

Abstract

Zoonotic visceral leishmaniasis, caused by the intracellular protozoan parasite Leishmania infantum, is a neglected tropical disease that is often fatal when untreated. Dogs are considered the main reservoir of L. infantum in zoonotic VL as the presence of infected dogs may increase the risk for human infection. Canine visceral leishmaniasis (CVL) is a major veterinary and public health problem in Southern Europe, Middle East and South America. Control of animal reservoirs relies on elimination of seropositive dogs in endemic areas. However, treatment of infected dogs is not considered a favorable approach as this can lead to emergence of drug resistance since the same drugs are used to treat human infections. Therefore, vaccination against CVL remains the best alternative in control of the animal reservoirs. In this study, we present data on the immunogenicity profile of a live attenuated parasite LdCen(-/-) in a canine infection model and compared it to that of Leishmune(®), a commercially available recombinant vaccine. The immunogenicity of the LdCen(-/-) parasites was evaluated by antibody secretion, production of intracytoplasmic and secreted cytokines, activation and proliferation of T cells. Vaccination with LdCen(-/-) resulted in high immunogenicity as revealed by the higher IgGTotal, IgG1, and IgG2 production and higher lymphoproliferative response. Further, LdCen(-/-) vaccinated dogs showed higher frequencies of activated CD4+ and CD8+ T cells, IFN-γ production by CD8+ T cells, increased secretion of TNF-α and IL-12/IL-23p40 and decreased secretion of IL-4. These results contribute to the understanding of immunogenicity elicited by live attenuated L. donovani parasites and, consequently, to the development of effective vaccines against visceral leishmaniasis.

Genetically Modified Live Attenuated Leishmania donovani Parasites Induce Innate Immunity through Classical Activation of Macrophages That Direct the Th1 Response in Mice

“…6G). Thus, these results suggest that live attenuated parasite-infected BMDM are capable of inducing the proliferation of Th1 type CD4 ϩ T cells in vitro, and the findings are consistent with an enhanced adaptive immune response to live attenuated parasites in various animal models as has been demonstrated elsewhere (40)(41)(42)(43).…”

“…Further, in live attenuated parasite-infected mice, the antigen-presenting abilities of macrophages were skewed toward a more effective Th1 response. These studies confirmed that the protective adaptive immune response generated by live attenuated parasites against wild-type L. donovani challenge previously observed by us (40)(41)(42)(43) is directed by the innate response generated by host macrophages.…”

“…), induction of a host-protective Th1 adaptive immune response and long-term protection against L. donovani infection (40)(41)(42)(43). However, whether the immunological basis of protection in terms of the host innate response induced by these live attenuated parasites could account for the protection observed in various animal models (40)(41)(42)(43) remains unexplored.…”

“…The live attenuated vaccines allow the host immune system to interact with a broad repertoire of antigens considered crucial in the development of protective immunity and, notably, cause no pathology (39). Recently, we demonstrated that these genetically modified L. donovani parasites (Ldp27 Ϫ/Ϫ and LdCen Ϫ/Ϫ ) when used as vaccine candidates induced protection against virulent L. donovani infection in various animal models (mice, hamsters, and dogs), as indicated by control of parasitemia and the induction of a host protective T cell response (40)(41)(42)(43). Since macrophage activation plays an important role in the commitment of T cells to either a protective (Th1) or disease-causing (Th2) phenotype during Leishmania infection (44), it is essential to study the role of macrophages and their phenotypes (M1 and M2) in live attenuated parasite-induced immunity.…”

Not All Antigens Are Created Equally: Progress, Challenges, and Lessons Associated with Developing a Vaccine for Leishmaniasis

“…To target and appropriately skew the anti-Leishmania response, vaccines require both pathogen-specific antigens and immune-stimulating molecules to be rendered effective. Whole and genetically attenuated parasites, such as L. donovani centrin-deleted parasites (LdCen1 Ϫ/Ϫ ), have undergone trials in both dogs and humans (4)(5)(6)(7)(8). Dendritic cell (DC)-based vaccines represent a more refined strategy and have been used in preclinical models.…”