Search for an antibody profile of Rhodococcus equi infection in AIDS patients despite the diversity of isolates and patient immune dysfunction

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-ass ociated antigen. In contrast, only three out of nine Italian isolates were positive for virulence-associated antigens - two for the 15- to 17-kDa anti gen and one for the 20-kDa antigen. In four other Italian strains, one or m ore other low-molecular-weight antigens were identified. Because of R. equi variability and host immune dysfunction, no characteristic antibody profil e was detected among patients, although the presence of specific antibodies in serum samples suggested prognostic value: good patient outcome and reco very from pneumonia were correlated with R. equi antibody detection, wherea s the lack or disappearence of specific antibodies, mainly those to low-mol ecular-weight: antigens, was correlated with disease progression and patien t death. These results confirmed the nonobligatory presence of the well-kno wn virulence-associated antigens for the pathogenicity of R, equi in humans , and also the diversity of R. equi strains isolated from AIDS patients, wh ich may be related to the geographic origin of the isolates or may be a con sequence 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. (C) Elsevier, Paris.