In the present study baculovirus expressed non-structural-protein (NSP) 3A of FMD virus (FMDV) was used to develop an indirect ELISA for differentiation of FMDV infected and vaccinated animals (DIVA). Using this test, field sera (from Haryana, India) were tested where a significant reduction (P 32). In 1st HtCE (AIraq22 vaccine/AIran96 challege virus), the vaccine offered good protection (PD506) but the vice versa of vaccine and challenge virus in 2nd HtCE could not offer protection (PD50