Introduction: Ureaplasma spp. are vaginal commensals. Ascension into the amniotic cavity leads to chorioamnionitis and preterm birth (PTB) in some, but not all, vaginally-colonised pregnant women; predicting risk of Ureaplasma-related PTB is problematic. This study aimed to correlate vaginal Ureaplasma colonisation in early pregnancy with maternal anti-Ureaplasma antibody and obstetric outcome for improved ability to identify of at risk women.
Methods: Maternal blood was collected at ~20 weeks’ gestation. Vaginal colonisation (positive/negative) with Ureaplasma spp. was determined from self-collected vaginal swabs by culture and qRT-PCR. Immunoblots assessed maternal IgG responses to proteins isolated from four serovars (SV) of U.parvum (UpSV1, UpSV3, UpSV6 and UpSV14).
Results: 31 Ureaplasma-positive and 27 Ureaplasma-negative women were recruited. 23 women were colonised with U.parvum, six with U.urealyticum and two with both biovars. IgG responses were biovar-specific; serum derived from U.urealyticum-positivewomen had a reduced ability to react with U.parvum-derived proteins. IgG responses were SV-independent; responses were not specific to the colonising SV nor different to each other. In U.parvum-positive women, seroreactivity was common against proteins of ~115kDa (95.2%), ~75kDa (81%), and ~17kDa (61.9%). No woman were truly seronegative but serum from Ureaplasma-negative women had a reduced capacity to recognise multiple U.parvum proteins and reduced recognition of the ~115kDa (44.4%, p<0.001), ~75kDa (33.3%, p<0.01), and ~17kDa (11.1%, p<0.001) proteins. One Ureaplasma-negative and four Ureaplasma-positive women (all UpSV6) delivered preterm. U.parvum-positive women delivering preterm showed 100% seroreactivity against the ~115kDa protein, reduced recognition of the ~75kDa protein (50%) and no recognition of the ~17kDa protein (0%).
Conclusion: Seroconversion in response to Ureaplasma spp. is common, but elevated antibody responses are observed in vaginally-colonised pregnant women. Further characterisation of key protein antigens may identify specific antibodies conferring protection from PTB. The ability to predict Ureaplasma-related PTB remains challenging, but key in order to apply appropriate preventative therapies.