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A neglected disease of the tropical countries, leishmaniases or kala-azar, is caused by a single-celled (protozoan) parasite, Leishmania, that enters the human body when infected sand flies inoculate the parasite into the skin during its blood meal. The disease clinically ranges from localized cutaneous lesions that heal quickly to mucosal and visceral leishmaniasis that is almost always fatal if untreated. Globally about 350 million people, mainly the poor, are at risk of contracting this life-threatening disease, and two million new cases occur annually.
The need of the hour is a safe, efficacious and affordable vaccine against predominant Leishmania strains that is producible with minimal batch-to-batch variations and is stable under tropical conditions without cold chain. Most experimental vaccines against this disease comprise specific peptides of the bug, produced by gene cloning methods. These peptides are those which elicit a strong immune reaction in the host.
DNA vaccines are crafted from the genetic material of the pathogen that encodes antigens against which the human body raises a strong protective response, but in no way enable the pathogen to reconstitute itself and cause disease. In a collaborative project, funded by European Commission, a team of Indian scientists from CSIR-Indian Institute of Chemical Biology, CSIR-IICB has on the preclinical development of a safe and effective prophylactic DNA vaccine for combating this dreaded disease.
Normally circular DNA structures called ‘plasmids’ are used for incorporating the pathogen genes for constituting a DNA vaccine. CSIR scientists have developed the vaccine, christened as LEISHDNAVAX, which uses the state-of-the-art gene expression system developed by MOLOGEN AG, called Minimalistic Immunogenically Defined Gene Expression (MIDGE) vector, as gene delivery system. Unlike other DNA vectors like plasmids and viruses, the MIDGE vector contains only the information required for its actual activity. As it is free from undesirable information, the size of this vector is much smaller than that of conventional vectors. This DNA vaccine is a formulation comprising five select parasite genes that encode antigens which are found to be present in lymphocytes called T-cells of affected people residing in endemic geographical locations spread across the globe.
The LEISHDNAVAX vaccine has been tested to be highly effective in mice model of experimental visceral leishmaniasis, as it induces a strong and protective T-cell response to the infecting bug. This wonder vaccine, after it completes the necessary clinical trials, is all set to become the most trusted weapon to wipe out the menace of this neglected disease from the face of our planet.
(The Write-up is a feature from Unit of Science Dissemination Unit,(USD), CSIR)