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Expression of Host Macrophage Cytokines on Infection with Various Mycobacterium avium Wild Type and ssGPL Mutant Strains

By Yang Dai and Danielle Dunton

Mycobacterium avium complex (MAC) can cause severe disease (localized tuberculosis or disseminated disease) in immunocompromised patients. The complex consists of various serovars and morphologic forms that vary in virulence. MAC’s unique cell wall structure is associated with its virulence and drug-resistant nature. Glycopeptidolipids (GPL) are located on the surface of MAC cell wall. Two forms of MAC GPLs are present: serovar-specific glycopeptidolipids (ssGPL) and the apolar non-specific GPLs (nsGPL). ssGPL has the same structure as nsGPL except for an oligosaccharide (ss) attached on nsGPL. The same nsGPL can be found in all MAC strains. Only ssGPL varies among strains, thus classifying MAC into twenty-eight different serovars. In this experiment, two MAC wild type (wt) serovars, serovar-1 (MAC 104), serovar-8 (920A6 SmO) and their ssGPL mutants, 209R.5 (serovar-1 --> serovar-2 ssGPL) and 213R.4 (ssGPL null mutant of serovar-8 920A6) were used to infect murine macrophage cell line (J774A.1) with multiplicity of infection (MOI) of 5:1. These mutants were compared to the wt to determine if ssGPL is involved in M. avium pathogenesis. After 1h infection, the supernatants were collected and used to determine cytokine expression (TNF-alpha and IL-12). If ssGPL is involved in pathogenesis, then absence of ssGPL will result in low cytokine expression. Also, it is hypothesized that different serovars induce different levels of cytokines. This research study will address the above hypotheses, and its goal is to elucidate the early events associated with M. avium infection as a means to identify potential alternative therapeutic targets that alter the pathogenesis of infection.

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