Mycoplasma pulmonis, the etiologic agent of murine respiratory mycoplasmosis, is prevalent in most, if not all rodent populations in the United States. Virulence determinants have not been identified in M. pulmonis and most other mycoplasmas, probably as a result of the lack of clearly defined nonvirulent mutants and a poor understanding of the cellular aspects of the disease process. Only recently has our understanding of mycoplasma-host interactions improved through the development of simple in vitro models. The premise of this proposal is that mycoplasmas cause disease through the acquisition of host supplied nutrients and membrane components. It will focus on M. pulmonis membrane-associated activities which have been previously identified: hemagglutination, hemolysis, and a membrane-associated nuclease activity. Hemagglutination may be a reflection of the multiphasic association of M. pulmonis with host cell surfaces, hemolysis may provide a mechanism for acquisition of host membrane components, and the external nuclease may degrade host DNA, providing precursors for parasite DNA synthesis. Specifically, the proteins involved in each activity will be identified by the use of activity-blocking monoclonal antibodies in immunoblots and radioimmune precipitation reactions. In addition, chemically induced mutants for each activity will be obtained and screened for loss of growth potential in defined or serum-free medium and for cytopathogenic potential in in vitro assays. This combined approach of hybridoma technology and genetics will correlate specific proteins with defined activities permitting assessment of the role of each activity in cytopathogenesis. Eventually this knowledge will be invaluable in targeting specific genes for further study and for designing vaccine stratagems for mycoplasma control in the general laboratory rodent population.
