Expression of virulence-associated antigens of Rhodococcus equi is regulated by temperature and pH.
We recently reported that there are two different virulence-associated antigens correlated with virulence levels in Rhodococcus equi isolates from AIDS patients: virulent R. equi that kills mice with 10(6) cells expresses 15- to 17-kDa antigens and intermediately virulent R. equi that kills mice with 10(7) cells expresses a 20-kDa antigen. Environmental parameters were evaluated for their effects on the expression of these virulence-associated antigens in virulent R. equi strains by immunoblotting using monoclonal antibodies in this study. Expression of these two virulence-associated antigens of R. equi was regulated by pH and temperature; the antigens were produced maximally when the isolates were grown at 38 C and pH 6.5, but were not produced when grown at 38 C and pH 8, nor at temperatures below 30 C. The 20-kDa antigen was found to be located on the cell surface, as were the 15- to 17-kDa antigens, and showed susceptibility to proteolysis by trypsin. These results indicate that expression of the virulence-associated antigens of R. equi is dependent on the environmental conditions.
Takai
S
S
Department of Animal Hygiene, School of Veterinary Medicine and Animal Sciences, Kitasato University, Aomori, Japan.
Fukunaga
N
N
Kamisawa
K
K
Imai
Y
Y
Sasaki
Y
Y
Tsubaki
S
S
D000907:Antibodies, Bacterial; D000911:Antibodies, Monoclonal; D000942:Antigens, Bacterial / Q000032:analysis*; D015964:Gene Expression Regulation, Bacterial; D006863:Hydrogen-Ion Concentration; D015151:Immunoblotting; D016929:Rhodococcus equi / Q000472:pathogenicity*; D013696:Temperature
D000907:Antibodies, Bacterial; D000911:Antibodies, Monoclonal; D000942:Antigens, Bacterial