Cytokine profiles of macrophages by Mycobacterium abscessus conditional morphotype variants and comparison of their extracellular-protein expressions

Mycobacterium abscessus has been identified as an emerging pulmonary pathogen in humans. Previously, it was documented that a spontaneously formed rough variant of M. abscessus causes persistent and invasive infection in mice, while a smooth isogenic variant does not. However, little is known for immune responses elicited by M. abscessus variants artificially induced by culture conditions and their culture filtrate antigens. Thus, morphological variants of M. abscessus type strain (ATCC19977T) were generated by an acidic and low oxygen culture conditions. Overall comparison between the variant and its original smooth strain showed that the rough variant was less virulent than original smooth strain in murine bone-marrow derived macrophage. To understand the basis for the difference, the protein expression pattern in the culture filtrates of each strain was analyzed by 1-dimensional electrophoresis. Generally, the protein expressions were more influenced by pH conditions than oxygen pressures. Interestingly, several proteins, mainly lower than 30 kDa molecular weight, were uniquely expressed in normal culture conditions. In contrast, several high molecular weight proteins (>55 kDa) were induced by acidic and low oxygen culture conditions. These findings not only provide new insights of association between morphoiogical change and the virulence, but may also be useful in the design of immunological diagnosis and vaccines for M. abscessus infection.