Scientists in Delhi claim to have developed a drug which can boost the immune system, to fight leprosy and multi-drug resistant tuberculosis. The drug is a naturally found protein, gamma-interferon, which also has anti-viral and anti-cancerous properties, a scientist at the International Centre for Genetic Engineering and Biotechnology, Navin Khanna, told reporters here. Mr Khanna and his colleagues have devleoped a new route to prepare the therapeutic protein artificially.