Vaccination with recombinant Leishmania donovani gamma-glutamylcysteine synthetase fusion protein protects against L. donovani infection

Visceral leishmaniasis presents a serious health threat in many parts of the world. There is, therefore, an urgent need for an approved vaccine for clinical use to protect against infection. In this study, the ability of recombinant Leishmania donovani gammaglutamyl cysteine synthetase protein (Ld gamma GCS) alone or incorporated into a non-ionic surfactant vesicle (NIV) delivery system to protect against L. donovani infection was evaluated in a BALB/c mouse model. Immunization with Ld gamma GCS alone or Ld gamma GCS-NIV induced specific IgG1 and IgG2a antibodies compared to controls, with Ld gamma GCS-NIV inducing significantly higher titers of both antibody classes (P < 0.05). Both formulations induced similar increases in splenocyte IFN-gamma production following ex vivo antigen stimulation with Ld gamma GCS compared with cells from control mice (P < 0.05). Similar levels of protection against infection were induced by Ld gamma GCS alone and Ld gamma GCS-NIV, based on their ability to suppress liver parasite burdens compared to control values (P < 0.01), indicating that using a carrier system did not enhance the protective responses induced by the recombinant protein. The results of this study indicate that Ld gamma GCS may be a useful component in a vaccine against L. donovani.