Mechanisms of attachment of Mycoplasma arthritidis to host cells in vitro

Abstract

Although other investigators have reported that Mycoplasma arthritidis failed to attach to several types of mammalian cells in vitro, we showed that it attached well to rat synovial fibroblasts, lung cells, and skin cells but not to kidney cells, suggesting that receptor sites are unequally expressed or distributed among different rat tissues. M. arthrifidis also attached poorly to canine kidney and to baby hamster kidney cells, although it did attach to human fetal lung and fetal amnion cells. Four M. arthritidis strains, two virulent and two avirulent, all attached equally well to rat lung cells. Attachment was inhibited by trypsinization, suggesting that the major adhesins are protein. Fab' fractions of rabbit antisera against four M. arthritidis strains partially inhibited adherence of both homologous and heterologous strains, although not to the same extent, indicating some degree of antigenic heterogeneity among their adhesins. A filter-cloned variant of M. arthritidis 158plOp9, designated LC1, attached poorly compared with the parent strain. Missing from this variant were two proteins migrating within the 81to 90-kDa range by polyacrylamide gel electrophoresis; in their place was a 24-kDa antigen that may be a truncated version of one of these proteins. A monoclonal antibody that partially inhibited attachment recognized all these peptides by Western immunoblotting. An additional attachment-inhibiting monoclonal antibody recognized a 71-kDa antigen present in both low-adherence and fully adherent populations. The low-adherence variant LC1 induced slightly but significantly less arthritis in Lewis rats than did a fully adherent clone. Attachment of microbial pathogens to host tissues is a critical event in most infectious diseases. For Mycoplasma species, even saprophytic existence is highly dependent on close association with host cells, as a result of the small genome and correspondingly limited synthetic capacity of these organisms (24, 26). Attachment mechanisms have been studied for a number of members of the class Mollicutes (26), and an association with virulence has been shown for at least two species, Mycoplasma pneumoniae and M. pulmonis (21, 32). M. arthritidis, a natural pathogen for rats (45), is not among the species that have been studied in detail, although other investigators have reported its failure to hemadsorb or to attach to mouse fibroblasts, mouse macrophages, and human and rabbit polymorphonuclear leukocytes in vitro (7, 22, 29). The ability to hemadsorb and to attach to fibroblasts was tested by overlaying M. arthritidis colonies on agar with cell suspensions (7, 22). However, in a study done several years ago, we observed by immunofluorescence that M.

Comparison of Mycoplasma arthritidis strains by enzyme-linked immunosorbent assay, immunoblotting, and DNA restriction analysis

“…1B and 2B), indicating that it was at least partly strain specific. Another marker for this set of strains was a prominent antigen, previously identified as a putative adhesin and designated MAA2 (52), which migrated just below the 66-kDa marker in strains H606 and 13988 and just at 66 kDa in the other five strains ( Fig. 1A; see arrows).…”

“…After 24 to 48 h of incubation, the 5-ml cultures were frozen in 1-ml aliquots at Ϫ70ЊC for use as stock cultures. For PG6 and H606, the filtration and cloning processes were performed once, while for 158p10p9 they were repeated a total of three times for each lineage (52).…”

“…Rabbit antisera were prepared against each strain as described previously (51)(52)(53)(54); the resulting antibody responses were directed largely against surface antigens. Monoclonal antibodies (MAbs) G9a and 7a (isotype immunoglobulin G2A [IgG2A]), directed against putative adhesins MAA1 and MAA2 from strain 158p10p9, respectively, were also described previously (52). A third MAb (isotype IgG1), directed against an antigen that migrates at 74 kDa in strain H606 but at a slightly higher molecular mass range in the other strains tested, was prepared similarly from mice immunized with strain 158p10p9.…”

“…These studies have uncovered cross-reactivities between M. arthritidis and Mycoplasma pulmonis (31) and between M. arthritidis and various rat tissues (41,45). In addition, antigens that serve as targets for metabolism-inhibiting antibodies (50) and two surface proteins involved in adherence to host tissues (52) were identified. Droesse et al (10)(11)(12) showed that several M. arthritidis surface proteins undergo rapid spontaneous size and phase variations both in vivo and in vitro, which could possibly complicate immune recognition.…”

Comparative genomic analysis of seven Mycoplasma hyosynoviae strains

“…The molecular basis for attachment to the synovial membrane remains largely unknown. However, previous studies involving the related organism M. arthritidis implicated a 90 kDa adhesin, MAA1, in attachment of bacterial cells to the surface of rat synovial fibroblasts (Washburn et al 1993(Washburn et al , 2000.…”