Inactivated Flagellin-Containing Vaccine Efficacy against Ovine Enzootic Abortion

Area of Science:

• Veterinary immunology
• Infectious diseases
• Vaccinology

Background:

• * *Chlamydia abortus* causes significant abortion and fetal loss in livestock, including sheep, goats, and cattle.
• * Current vaccines offer partial protection, highlighting the need for novel, safer, and more effective vaccine strategies.
• * Developing new vaccines against *C. abortus* is a priority for animal health.

Purpose of the Study:

• * To evaluate the efficacy of a novel vaccine candidate against *Chlamydia abortus* in pregnant sheep.
• * To assess the vaccine's ability to prevent abortion, reduce pathogen shedding, and improve lamb survival.

Main Methods:

• * An inactivated antigen vaccine using outer membrane proteins of *C. abortus* strain *Chlamydia VNITIBP-21* with recombinant flagellin adjuvant was developed.
• * Forty-three pregnant ewes were divided into three groups: vaccinated, control infected, and control non-infected.
• * Ewes were vaccinated twice, then challenged with virulent *C. abortus* on day 75 of gestation.

Main Results:

• * The vaccine candidate significantly reduced *C. abortus* shedding in vaginal swabs compared to controls.
• * No abortions occurred in the vaccinated group.
• * Control-infected ewes experienced abortions and delivered weak or nonviable lambs.

Conclusions:

• * The evaluated vaccine candidate demonstrates significant promise in preventing ovine abortion and fetal loss.
• * This inactivated antigen vaccine with adjuvant is a potential tool for controlling *C. abortus* infections in sheep.
• * Further development could lead to a new effective vaccine against a major cause of livestock reproductive failure.