The double-sided effects of Mycobacterium bovis bacillus Calmette-Guérin vaccine on helminthic infections – current data and future prospects.

Bacillus Calmette-Guérin (BCG), a live attenuated strain derived from an isolate of Mycobacterium bovis, is one of the childhood vaccinations widely used against tuberculosis (TB). In addition to its effects on mycobacterial diseases, the information has shown the protection effect of BCG in helminthic diseases. In the current review, the role of BCG vaccine in non-specific protection helminthic infection is reviewed. In human alveolar echinococcosis (AE), treatment with BCG enhances host's innate immune response against the parasite via the number and activation of monocytes. In cysticercosis, despite the enhancement of Th1-biased immune responses by coadministration of rcC1 plus BCG-DNA, the level of induced protection did not increase compared to immunization with rcC1 antigen alone. Also, pretreatment of mice with live BCG vaccine induced a high level of protection against subsequent parasite infection with Taenia taeniaeformis. The reduction of the parasite burden in mice infected with Mesocestoides corti that received two doses of BCG post-infection demonstrated the therapeutic effect of BCG. The protective potential of the schistosomula/BCG vaccine against Schistosoma japonicum in sheep study showed a reduction in the number of adult worms and mean faecal egg counts post-challenge. In trichinellosis, BCG can induce hyperplasia of the reticuloendothelial system and activation of macrophages in mice. Therefore, these data revealed that BCG vaccination can exert non-specific protective effects for the prevention of diseases other than tuberculosis. Medicinal doses of BCG may be considered a new approach to the treatment of helminth infections.