Actinobacillus seminis causes epididymitis in ruminants and spontaneous abortion. A. seminis virulence factors remain unknown; however, it has been shown that testosterone increased bacterial growth, adhesins expression, and protease expression, as well as biofilm production, suggesting the presence of a bacterial receptor for this hormone. The present study reported the isolation of two potential testosterone receptors from A. seminis grown in the presence of testosterone. A 75 kDa and a 55 kDa proteins were isolated from bacterial lysate with triazine orange-Sepharose CL6B column or with immobilized testosterone on polystyrene plates, respectively. Mass spectrometry identified the 75 kDa as the periplasmic LsrB, and the 55 kDa as the outer membrane OmpF from A. seminis. Molecular docking showed OmpF and LsrB interaction with testosterone in 59% and 55%, respectively. Testosterone plus furanone C-30 inhibits the expression of those proteins diminished bacterial growth, adhesin and protease expression. Cloning A. seminis lsrB into E. coli M15 strain improves clone development in a dose-dependent manner and induces the expression of proteases and putative adhesins. These findings strongly suggest that host testosterone could play a significant role in A. seminis pathogenesis, through OmpF and LsrB as testosterone receptors.
Ramírez-Paz-y-Puente et al. (2026) studied this question.