Summary auto-generated
This study investigated adhesion mechanisms of Mycoplasma genitalium and M. pneumoniae to human epithelial cells (HEp-2) using immunofluorescence microscopy. Researchers produced monospecific antibodies against recombinant fragments of key surface adhesion proteins: MgPa from M. genitalium (which is homologous to P1 from M. pneumoniae), P1 itself, and P116. Three fragments of MgPa, two of P1, and nearly complete P116 were generated as recombinant proteins. Through adhesion detection assays, the researchers determined which protein regions were surface-exposed. Results showed that only the C-terminal regions of MgPa and P1 were accessible on the mycoplasma surface. Adhesion inhibition experiments revealed that blocking these C-terminal regions with monospecific antibodies effectively prevented bacterial attachment to host cells. Additionally, P116 was identified as an essential adhesion protein, as anti-P116 antibodies blocked M. pneumoniae attachment independently of P1. The study successfully demonstrated the molecular basis of cytadherence in these important human pathogens and established immunofluorescence microscopy as an effective method for studying mycoplasma adhesion proteins.
Key findings
- Only C-terminal regions of MgPa and P1 are surface-exposed and directly involved in cytadherence, whereas N-terminal and middle regions are not accessible
- P116 is a surface-exposed protein essential for M. pneumoniae adhesion, functioning independently of P1 as an attachment factor
- Antibodies against C-terminal domains of MgPa and P1 effectively inhibit binding to HEp-2 cells with dramatic concentration-dependent effects
- MgPa of M. genitalium and P1 of M. pneumoniae show functional homology despite only 51.7% amino acid identity
- Immunofluorescence microscopy with monospecific antibodies is an effective method for identifying surface-exposed adhesion domains and evaluating their role in cytadherence
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Abstract
Adhesion of Mycoplasma pneumoniae and the closely related M. genitalium to HEp-2 cells was investigated. The main surface proteins known to be involved in adhesion are P1 of M. pneumoniae and its homologue, MgPa, of M. genitalium. Both proteins are also immunodominant proteins. Protein P116 is another immunodominant protein of M. pneumoniae. These immunogenic proteins were investigated for their surface exposure and involvement in adhesion to host epithelial cells. Immunofluorescence microscopy (IFM) was used to detect M. pneumoniae and M. genitalium adhering to HEp-2 cells. Monospecific antibodies were produced against fragments of the surface proteins lacking tryptophan stop codons and were used for adhesion detection, surface exposure and adhesion inhibition IFM assays. Three monospecific antibodies were made against MgPa covering regions in the N-terminal, the middle and the C- terminal part; two monospecific antibodies were produced against P1 covering regions of the N- and the C-terminal part and one monospecific antibody was made against most of P116. Only the C-terminal parts of P1 and MgPa were surface exposed and blocking of these regions with the monospecific antibody resulted in inhibition of cytadsorption. Protein P116 was shown to be surface exposed and an essential protein involved in adhesion because the anti-P116 antibody prevented attachment of M. pneumoniae to the HEp-2 cells independently of P1. This study adds to the understanding of the molecular biology of M. genitalium and M. pneumoniae and presents a method to study the proteins involved in adhesion of these mycoplasmas.