Nucleoside Hydrolase NH 36: A Vital Enzyme for the Leishmania Genus in the Development of T-Cell Epitope Cross-Protective Vaccines

Abstract

NH36 is a vital enzyme of the DNA metabolism and a specific target for anti- Leishmania chemotherapy. We developed second-generation vaccines composed of the FML complex or its main native antigen, the NH36 nucleoside hydrolase of Leishmania (L.) donovani and saponin, and a DNA vaccine containing the NH36 gene. All these vaccines were effective in prophylaxis and treatment of mice and dog visceral leishmaniasis (VL). The FML-saponin vaccine became the first licensed veterinary vaccine against leishmaniasis (Leishmune®) which reduced the incidence of human and canine VL in endemic areas. The NH36, DNA or recombinant protein vaccines induced a Th1 CD4 + IFN-γ + mediated protection in mice. Efficacy against VL was mediated by a CD4 + TNF-α T lymphocyte response against the NH36-F3 domain, while against tegumentary leishmaniasis (TL) a CD8 + T lymphocyte response to F1 was also required. These domains were 36–41 % more protective than NH36, and a recombinant F1F3 chimera was 21% stronger than the domains, promoting a 99.8% reduction of the parasite load. We also identified the most immunogenic NH36 domains and epitopes for PBMC of active human VL, cured or asymptomatic and DTH + patients. Currently, the NH36 subunit recombinant vaccine is turning into a multi-epitope T cell synthetic vaccine against VL and TL.

The Delay in the Licensing of Protozoal Vaccines: A Comparative History

“…The FML complex inhibited the penetration of promastigotes (90) and amastigotes (91) into macrophages in in vitro assays in a species-specific manner (92). In addition, FML was immunogenic for mice and rabbits, and most of the anti-FML monoclonal antibodies reacted with its 36-kDa main component (91), which was disclosed to be a Nucleoside hydrolase (NH36) phylogenetic marker of the genus Leishmania (93). FML also showed high sensitivity and specificity in the serological diagnosis of human (94) and dog VL (95) and can be used in ELISA assays for the control of transfusional VL (96).…”

“…The second human vaccine that was tested in clinical trials is LeishF3 ( Table 1), composed of the Nucleoside hydrolase NH36 of Leishmania (L.) donovani (93,(139)(140)(141)(142)(143)(144)(145), which is the main antigen of the Leishmune R vaccine (91,94,139), and the sterol 24-c-methyltransferase (SMT) from L. (L.) infantum. The vaccine is adjuvanted by glucopyranosyl lipid A-stable oil-inwater nanoemulsion (GLA-SE) (146,147).…”

New Approaches to the Prevention of Visceral Leishmaniasis: A Review of Recent Patents of Potential Candidates for a Chimeric Protein Vaccine

“…These enzymes are present in all species of Leishmania spp., justifying their use as phylogenetic markers. Additionally, they share high identification levels among many microorganisms but are absent in mammals [ 124 ]. These characteristics make NHs targets for an anti-VL vaccine by inducing high immunogenicity [ 124 ].…”

“…Additionally, they share high identification levels among many microorganisms but are absent in mammals [ 124 ]. These characteristics make NHs targets for an anti-VL vaccine by inducing high immunogenicity [ 124 ]. For instance, the NH36 of L. donovani is a non-specific nucleoside hydrolase that is the main antigen of Leishmune ® , a vaccine previously sold in Brazil from 2004 to 2014, which was discontinued due to noncompliance with the requirements of phase III studies for efficacy (Brazil, Technical Note 038/2014).…”

Structure, Oligomerization and Activity Modulation in N-Ribohydrolases

“…As is the case for other protozoan parasites, members of the Leishmania genus also encode for two NHs in their genome, and their expression has been demonstrated in several isolates of L. infantum and L. donovanii [ 74 , 95 , 96 ]. These isozymes can be inhibited by several immucillins, most efficiently by Immucillin-A, to impair Leishmania mastigotes’ replication in vitro and in vivo.…”