Detection of human IgG antibodies against <i>Mycoplasma genitalium</i> using a recombinant MG075 antigen

<i>Mycoplasma genitalium</i> is the second most common sexually transmitted bacterial infection after chlamydia. The long-term consequences of the infection are still under investigation, but reliable tools for monitoring exposure by detection of antibodies have been lacking specificity due to the presence of cross-reacting antibodies to the closely related <i>Mycoplasma pneumoniae</i>. Here, we describe a novel diagnostic antigen with promising sensitivity (87%) and specificity (95%) based on testing of sera from patients with PCR-confirmed <i>M. genitalium</i> infection and children with and without <i>M. pneumoniae</i> infection, respectively. The MG075F1 antigen was expressed in <i>Escherichia coli</i>, and the recombinant antigen was used in a western line-blot. Due to the insolubility of the antigen, harsh denaturing conditions were needed, making an enzyme-linked immunosorbent assay (ELISA) format impossible. Future work should explore shorter fragments or protein engineering to allow for assay designs better suited for high-throughput screening.