A discovery by international researchers regarding the immune response to visceral leishmaniasis (VL) holds tremendous promise for India's efforts to combat this deadly disease also known  as Kala Azar. As one of the countries most affected by VL, with a significant number of cases reported annually, India has been actively working towards controlling and eliminating the disease. VL is caused by protozoan parasites transmitted by the bite of an infected female phlebotomine sand fly. It is characterised by irregular bouts of fever, weight loss, enlargement of the spleen and liver, and anaemia. In over 95 per cent of cases, the disease is fatal if left untreated.

The discovery of a new CD4 T cell population and its role in combating the Leishmania parasite by the team of scientists by Institut national de la recherche scientifique (INRS) and McGill University offers opportunities for enhancing India's VL elimination strategies which had missed elimination deadline three times. This discovery, published in the journal Cell Reports, sheds light on a surprising immune mechanism linked to chronic VL, potentially paving the way for new therapeutic approaches.

CD4 T cells are pivotal in defending the body against infections, but maintaining their functionality becomes challenging in chronic infections like leishmaniasis. The newly discovered CD4 T cell population exhibits unique properties, including self-renewal and differentiation into effector or regulatory cells. This population appears to play a crucial role in preventing the exhaustion of naive CD4 T cells during chronic VL, thereby boosting the immune response against the parasite, said the study.