Molecular and histopathological evaluation of the efficacy of Saponified and Freund's incomplete adjuvanted paratuberculosis killed vaccine in murine model

Johne's disease (JD) is caused by Mycobacterium avium subspecies paratuberculosis (MAP). Vaccination is regarded as the only cost effective method for controlling JD. Experimental trial for 11 months was carried out by dividing mice into four different groups. Group I-saponified MAP killed vaccine; Group II-Freund's incomplete adjuvant (FIA) MAP killed vaccine; Group III-saponin adjuvant control; Group IV-FIA control. Mice of all the groups were challenged with 10⁸ colony forming unit live MAP organisms on 40^th day after vaccination. A total of 188 samples (52 faecal, 76 sera and 60 tissue samples) were collected from different groups of mice at different interval for monitoring MAP load by Ziehl Neelsen's staining and nested PCR along with tissue histopathology. Both the vaccinated groups (Group I and II) showed encouraging results in comparison to adjuvant control groups. There was reduction in faecal shedding (p<0.01), tissue load of MAP and less granuloma formation in both the vaccinated groups, however mice vaccinated with saponified MAP antigen gave better result in comparison to FIA vaccinated mice. Results of this study suggested that, saponified MAP killed vaccine in particular might reduce the overall burden of JD and show promising result in future.