Comparative assessment of a DNA and protein Leishmania donovani gamma glutamyl cysteine synthetase vaccine to cross-protect against murine cutaneous leishmaniasis caused by L. major or L. mexicana infection

Leishmaniasis is a major health problem and it is estimated that 12 million people are currently infected. A vaccine which could cross-protect people against different Leishmania spp. would facilitate control of this disease as more than one species of Leishmania may be present. In this study the ability of a DNA vaccine, using the full gene sequence for L. donovani gamma glutamyl cysteine synthetase (gamma GCS) incorporated in the pVAX vector (pVAX gamma GCS), and a protein vaccine, using the corresponding recombinant L. donovani gamma GCS protein (Ld gamma GCS), to protect against L major or L. mexicana infection was evaluated. DNA vaccination gave transient protection against L major and no protection against L. mexicana despite significantly enhancing specific antibody titres in vaccinated infected mice compared to infected controls. Vaccination with the Ld gamma GCS protected against both species but only if the protein was incorporated into non-ionic surfactant vesicles for L. mexicana. The results of this study indicate that a L. donovani gamma GCS vaccine could be used to vaccinate against more than one Leishmania species but only if the recombinant protein is used.