RESUMO
Diversity of virulence-associated antigens of Rhodococcus equi was detected among thirteen strains isolated from AIDS patients on two continents. One out of four Brazilian isolates presented the virulence-associated antigen of 15- to 17-kDa, and the other three isolates had the 20-kDa virulence-associated antigen. In contrast, only three out of nine Italian isolates were positive for virulence-associated antigens - two for the 15- to 17-kDa antigen and one for the 20-kDa antigen. In four other Italian strains, one or more other low-molecular-weight antigens were identified. Because of R. equi variability and host immune dysfunction, no characteristic antibody profile was detected among patients, although the presence of specific antibodies in serum samples suggested prognostic value: good patient outcome and recovery from pneumonia were correlated with R. equi antibody detection, whereas the lack or disappearance of specific antibodies, mainly those to low-molecular-weight antigens, was correlated with disease progression and patient death. These results confirmed the nonobligatory presence of the well-known virulence-associated antigens for the pathogenicity of R. equi in humans, and also the diversity of R. equi strains isolated from AIDS patients, which may be related to the geographic origin of the isolates or may be a consequence of the route of R. equi transmission in different countries. Some mechanisms underlying the results obtained are discussed, suggesting immune complex formation during the progress of the disease.
Assuntos
Infecções Oportunistas Relacionadas com a AIDS/diagnóstico , Infecções Oportunistas Relacionadas com a AIDS/imunologia , Infecções por Actinomycetales/diagnóstico , Infecções por Actinomycetales/imunologia , Anticorpos Antibacterianos/sangue , Rhodococcus equi/imunologia , Infecções Oportunistas Relacionadas com a AIDS/microbiologia , Infecções por Actinomycetales/microbiologia , Infecções por Actinomycetales/veterinária , Animais , Antígenos de Bactérias/imunologia , Eletroforese em Gel de Poliacrilamida , Doenças dos Cavalos/imunologia , Doenças dos Cavalos/microbiologia , Cavalos , Humanos , Immunoblotting , Rhodococcus equi/classificação , Rhodococcus equi/genética , Rhodococcus equi/patogenicidade , VirulênciaRESUMO
Rhodococcus equi (formerly Corynebacterium equi) are known to be highly virulent, intermediate in virulence, or avirulent correlated with specific virulence-associated antigens identified immunochemically by different molecular weights. The association of virulence antigens with infection of AIDS patients by this organism has not been sufficiently evaluated in Brazil or Italy. The objective of the present study was to search for virulence-associated antigens of 15-to 17-kD and 20-kD in Rhodococcus equi strains isolated from patients with rhodococcal infection and AIDS. Four Brazilian and 9 Italian strains were studied. All isolates were analyzed by gel electrophoresis followed by immunoblotting using specific monoclonal antibodies to identify virulence-associated antigens. The results obtained on gel electrophoresis analyses showed complexing of R. equi components with proteins of molecular weights ranging from 10-to 150-kD. By immunoblotting, a wide diversity in R. equi virulence-associated antigens was detected: 1 of the 4 Brazilian isolates and 2 Italian isolates had the 15-to 17-kD virulence-associated antigen, 3 Brazilian isolates and 1 Italian isolate had the 20-kD virulence-associated antigen, and the other Italian isolates had no virulence-associated antigens. These results indicate that the pathogenicity of R. equi strains for humans does not depend only on the presence of these well established virulence-associated antigens.