Protective effect of antigen excess immune complex in guinea pigs infected with Mycobacterium tuberculosis

: Immune complexes (ICs) play a crucial role which can either be beneficial or pathological to the host. Involvement of circulating immune complexes (CICs) has been shown in tuberculosis (TB) cases (adults and neonates form), but its immunomodulatory effect has not been studied in vivo. Hence, this study was carried out to understand and explore the prognostic therapeutic potential of CICs on the host immune system in guinea pigs animal TB model.

In this study, the guinea pigs (group I) were immunized with in vitro synthesized antigen excess IC (AgX-IC), group II with antibody excess IC (AbX-IC) and group III with phosphate-buffered saline. All these animals were sensitized with Mycobacterium tuberculosis H37Rv before immunization and subsequently infected with M. tuberculosis H37Rv strain post-immunization with IC.

Mortality was observed in animals belonging of groups II and III, while all animals in group I survived. A steady increase in the body weight of animals immunized with AgX-IC was observed when compared to the other groups. The infection load in the spleen and lungs was less in animals from group I when compared to the other groups. The CICs were found to be in higher concentration in serum of IC-immunized guinea pigs when compared to ICs non-immunized animals.

Based on our findings, it can be speculated that the ICs may have a protective immunomodulatory role pertaining to disease progression and development of pathology. As a new perspective, with further insight into the underlying mechanism of action and correlation with clinical data, ICs may also be used as a potential tool for assessing the immune status of the infected individuals, especially the close contacts of TB patients.