The Inductive Effect of Purified Streptococcal M-protein on Immunity against Streptococcus pyogenes in Rabbit Model

Aims: The study aimed to know the effects of the purified M-protein on immune system to produce protection against Streptococcus pyogenes in rabbits.

Study Design: Case-control study.

Place and Duration of Study: In this study, collection samples and bacterial identification were carried out in two hospitals; Child Protection Hospital and Central Child Hospital in Baghdad city, and experimental work was done in Department of Medical Microbiology, College of Medicine-Babylon university, Iraq. The study was done during the period between January to July 2014.

Methodology: A total of 260 samples were collected from tonsillitis and pharyngitis cases. Three main parts involved in this study: the first part is bacterial diagnosis based on relied diagnostic procedures. The second part is detection of serogroup of GAS and antistreptolysin O (ASO) antibodies by using latex agglutination test, and the third part is experimental study conducted on the protective immune response against the group A streptococci using rabbit model. M-protein was purified by using Ion exchange chromatography. The rabbit models were immunized with purified M protein according to standard method. The immune response generated against the M protein was checked in an rabbit population.

Results: From a total of 260 samples of tonsillitis and pharyngitis cases among children, only 8 (3.07%) isolates were identified as Streptococcus pyogenes. High amount of M-protein was detected in two isolates by indirect bacterial test. The concentration of purified M-protein ranged from 20-24.68 µg/ml. The purified M protein has important role in an induction of the immune response in experimental model. It leads to increased phagocytosis, stimulation of T-cell, and high level of antibody in serum of an immunized rabbits.

Conclusion: The purified streptococcal M protein has strong antigenicity, and it has important role in an induction the strong protective immune response in experimental rabbit model. It may be used in future studies as vaccine against streptococcal infection among humans.