Antisperm response in rams experimentally infected with Brucella ovis

Abstract

Brucella ovis infection causes chronic epididymitis in rams and may result in the formation of spermatic granulomas and a major reduction in fertility. To study the relationship between bacterial genital infection and antisperm response, 14 adult rams were experimentally inoculated via conjunctival ( n = 7; G1) or preputial route ( n = 7; G2) with a B. ovis strain. Serological response to B. ovis was evaluated by means of complement fixation (CF) and gel diffusion (GD). Autoimmunity was estimated by determination of antisperm antibodies (ASab) and the leukocyte migration inhibition test (MIT) using three different antigens: autologous sperm, ovine testicle, and B. ovis antigen. Immune responses were analyzed in relation to clinical signs, histopathological features, and bacterial isolations from semen and genital organs. Seven non-infected rams served as controls. Specific antibody titers were detected by CF during the second week post-inoculation (PI) in 100% of the inoculated rams. The CF values reached a peak during the 8th and 6th week PI for groups G1 and G2, respectively. The percentage of seropositive animals decreased progressively in both groups until weeks 45 and 30 PI. Specific antisperm reaction was verified by detection of immobilizing ASab and by MIT. ASab were detected in the serum of 85.7% and 71.4% of rams in G1 and G2, respectively, from week 3 PI onwards. Genital alterations were clinically detected in 71.4% of the inoculated rams. Gross epididymal lesions consisted of multiple caseous masses and cysts with purulent content. In those rams that presented clinical lesions, numerous spermatic granulomas were observed. 80% of these granulomas were located in the epididymis tail. Epididymitis, seminal vesiculitis, and chronic ampullitis were histologically detected in 71.4% of the animals of G1 and G2. B. ovis was isolated from 57% of semen cultures and was recovered from genital tissues in 75% of rams in both G1 and G2. At week 50 PI, four rams from each inoculated group (G1 and G2) received antibiotic treatment with long-acting oxytetracycline. In those animals treated with antibiotics, all semen and tissue cultures became negative to B. ovis at the time of the necropsy. However, cellular immunity was positive for autologous, testicular, and bacterial antigen and all rams demonstrated to be positive for ASab until week 80 PI. These data showed that rams with genital lesions caused by B. ovis developed a long-standing antisperm immune reaction. This autoimmune process could be significant in the pathogenesis of reduced fertility observed in B. ovis infected rams.