Major membrane proteins and lipoproteins as highly variable immunogenic surface components and strain-specific antigenic markers of Mycoplasma arthritidis

Abstract

Ha n nover, B isc hof s hole r Damm 15,30173 Hannover, Germany Microbiology, Surface antigenic variation was investigated in Mycop/asma arthritidis, an agent that produces chronic arthritis in rats which shares several features with many mycoplasma-induced diseases and thus defines a well-characterized model system. Hyperimmune rabbit antisera (anti-ISRI, anti-PG6, anti-H606 and anti-158~10) to whole M. arthritidis organisms were used as immunological probes in Western immunoblots of four M. arthritidis prototype strains (ISRI, PG6, H606 and D263) and five rat-passaged substrains (ISRlpl, ISRlp7, ISRlp8, 1 5 8 ~ 1 0 and D263pl). Several prominent antigens were identified that varied in expression. By Triton X-114 phase fractionation and treatment of whole cells with trypsin and carboxypeptidase Y, these strain-variant antigens were shown to be integral membrane proteins with C-termini and portions of the polypeptide chains oriented outside the membrane. Western blot immunoscreening of a large number of randomly selected clonal isolates and well-established clonal lineages from stock cultures of M. arthritidis ISRlp7, 158~10, PG6 and H606 revealed an expanded repertoire of variant membrane proteins whose expression was subject to independent, reversible phase variation. Colony immunoblots of these clonal populations with a hyperimmune rabbit antiserum to a gel-purif ied variant membrane protein (P36) showed that this phase switching occurred at a high frequency lo-* per generation). Detailed immunological and biochemical characterization of the phase-variant membrane proteins demonstrated that they are: (i) antigenically related or distinct; (ii) apparently specific to particular strain populations; (iii) proteins or lipoproteins; (iv) major immunogens of M. arthritidis, recognized by serum antibodies from convalescent rat; and (v) able to undergo variation in expression during in viwo passage. Thus, M. arthritidis possesses a complex system capable of creating large repertoires of cell surface phenotypes which may affect the multiple interactions of this organism with its host and dictate its potential as a successful infectious agent and pathogen. to

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

“…2A, lane 6) was missing an antigen migrating just below the 42-kDa marker. This antigen may correspond to one of several phase-variable antigens in the 37-to 43-kDa range recently described by Droesse et al (10) in the related strain, strain 158p10. In any case, loss of these antigens may explain the loss of adsorption ability.…”

“…Because some of the surface antigens of M. arthritidis have been shown in the present study ( Fig. 4) and by others (10,12) to undergo both phase and size variations, filter-cloned isogenic progeny of strains 158p10p9, PG6, and H606 were examined for the stability of expression of the antigens identified above as potential strain markers. To begin with, the 158p10p9-derived clones were tested for differences in their abilities to adsorb antibody from anti-158p10p9 antiserum.…”

“…In addition, it was important to determine the actual stability of any such markers in individual members of a strain, and hence the reliability of any identification or quality control scheme based on these properties. This final point illustrates a very real concern, considering that variation in surface proteins seems to be a common property of several Mycoplasma species (37,38,40), including M. arthritidis (10)(11)(12).…”

“…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. However, much of this work was done with single strains of M. arthritidis, and most studies with multiple strains were not specifically designed for comparative purposes.…”

pMGA Phenotypic Variation in Mycoplasma gallisepticum Occurs In Vivo and Is Mediated by Trinucleotide Repeat Length Variation

“…In vitro and, more importantly, in vivo, epitope switching has been observed for many M. gallisepticum surface molecules (3,7,11,24) and in mollicutes generally (5,21,22,25). This switching of surface epitopes may provide the organism with a means of avoiding the host immune response and/or of increasing tissue tropism.…”