Identification and opsonic activity of immunoglobulins recognizing Streptococcus zooepidemicus antigens in uterine fluids of mares.

A direct ELISA was used to measure immunoglobulin (Ig) isotypes G, Gt, A, and M recognizing Streptococcus zooepidemicus epitopes in uterine lavage fluids collected during the early post ovulatory period. A S. zooepidemicus isolate, used as the plate antigen in this assay, was inoculated into the uteri of 8 mares (3 resistant and 5 susceptible to endometritis) at oestrus prior to ovulation during Oestrous Cycles 1, 3 and 5. Resistant mares aged 2-5 years were nulliparous, with clinically normal reproductive tracts as determined by physical examination, bacteriological culture of the uterus, and endometrial biopsy. Susceptible, pluriparous mares, aged 16-24 years, had histories of endometritis and infertility and had chronic endometrial inflammatory changes detected by uterine biopsy. On Post ovulation Day 3 during Oestrous Cycle 1, on the day of ovulation during Oestrous Cycle 3 and on Post Ovulation Day 5 during Oestrous Cycle 5, uterine swab specimens were obtained for bacteriological culture and the uterus was irrigated with 50 ml sterile physiological saline solution containing tracer amounts of 125I-labelled human serum albumin (HSA). The titre of each Ig isotype was determined and the amount in uterine effluents was calculated from the dilution of the 125I-HSA. Total IgG concentration in uterine effluents was measured by radial immunodiffusion. Uterine fluids, either unheated or heated 30 min at 56 degrees C, were used to opsonize the S. zooepidemicus isolate in an assay of luminol-enhanced neutrophil chemiluminescence (CL). Mean peak CL generated was compared with CL generated by a control serum. Streptococcus zooepidemicus was isolated from 10 of 15 (67%) uterine specimens from susceptible mares.(ABSTRACT TRUNCATED AT 250 WORDS)