HTRA1 and chlamydia trachomatis infectious disease: Also in vivo, IgG antibody responses to C. trachomatis TroA and HtrA are more common in patients with ascending and repeated chlamydial infections than in healthy controls [15], and women with TFI have more often serum IgG antibodies to TroA and HtrA than subfertile women with patent Fallopian tubes [16].