Establishment of asymptomatic Leishmania donovani infection in Indian langurs (Presbytis entellus) through intradermal route

Abstract

Indian langurs, which were previously reported to be highly susceptible, were in fected intradermally using variable numbers of promastigotes along with different doses, 1/2 pair,5 pairs and 10 pairs respectively of salivary gland lysate (SGL). Although, all the monkeys developed mild infection and remained subclinically infected throughout the observation period, which later resolved, none of them could develop the classical disease. No marked antigen specific antibody or lymphoproliferative response was noticed throughout the experimental period. However, a late IFN-γ response (by day 90 pi.) was demonstrated in monkeys infected with 2x10⁶ promastigotes + 10 pairs SGL. It seems that a single intradermal dose of promastigotes with or without SGLs had a "vaccine" like effect. Perhaps, multiple frequent inoculations, as happens in the natural situation, may be necessary for the development of full-blown disease.