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A Group of Low Molecular Weight (<30 kDa) Antigens of Heat Killed Mycobacterium tuberculosis H37Rv Confer Better Protection against Experimental Tuberculosis in Guinea Pigs

Muralidhar K Katti, Chall V and Mahadevan B

Heat-killed Mycobacterium tuberculosis (Mtb) H37Rv derived antigens were purified by electro-elution and evaluated their efficacy in conferring protection against Tb in guinea pigs in order to identify those protein antigens as sub-unit vaccine.Atotal sonicate extract ofMtbH37Rv (MTSE) was prepared by growing bacteria on Lowenstein-Jensen (LJ) solid medium to its mid-log phase, harvested and subjected to ultra-sonication. Fractions ofMTSEwere resolved on 10%polyacrylamide gel electrophoresis into as high (HMW, >60kDa),middle (MMW, 31-59kDa) and lowmolecular weight (LMW, <30kDa) antigens and were purified by electro-elution. Protection efficacy of each purified fraction was assessed in a placebo controlled study by injecting them separately into a group of two animals. After two booster doses, animals were challenged on day 84 and autopsy of all animalswere performed on day 126. On autopsy, animals were scored for formation of ‘tuberclesÂÂ’ in lungs and its dissemination to organs such as spleen, liver, kidney and lymph nodes. Viable counts (determined as colony forming unit or CFU) of all organs (lung and spleen) from each animalwere performed on LJ solidmedium. Results of this study showthat CFU of animals those received LMWantigens, were significantly lowwith respect to control animals when compared to MMW and HMW. In conclusion, LMW of Mtb has greater potential in prevention of tubercle formation and thus could be viewed as possible vaccine candidates in designing alternative subunit vaccine.