Experimental actinomycetoma by Nocardia brasiliensis in different mice strains

Objective. Nocardia brasiliensis is the most common isolated bacteria from actinomycetoma patients. The purpose of this work was to induce experimental mycetoma in different mice strains and to study the relation between anti-M brasiliensis antibody concentration and evolution of mycetoma lesion. Material and methods. In this work we used N. brasiliensis ATCC 700 358 to infect 10 mice of different strains: C57BL/6, CBA/N, DBA/2, F1 (CBA/N X DBA/2) females and F1 (CBA/N X DBA/2) males. Animals were observed daily for mycetoma signs. blood samples were obtained at various times after infection. A Western blot was used to identify immunodominant antigens and an ELISA assay for anti-N. brasiliensis antibody concentration. IgG and IgM antibody isotypes were determined by ELISA. Results. C57BL/6 mice developed complete actinomycetoma lesion 30 days after infection and most of them recovered by day 200. CBA/N, DBA/2 and their female and male F1 hybrids presented a complete mycetoma 150 days after infection with no spontaneous healing of mycetoma lesion. Western blot analysis showed P61, P26 and P24 as immunodominant antigens and the anti-P24 antibody concentration increased in tested animals except CBA/N mice. IgG isotype response was similar to total antibody response but IgM isotype was always low mainly in CBA/N males. Conclusion. A strong anti-N. brasiliensis antibody response was obtained in almost all tested animals mainly due to IgG isotype. CBA/N antibody titer was lower particularly IgM isotype. No correlation was found between anti-N. brasiliensis antibody concentration and severity of mycetoma lesion.