# Inactivated Flagellin-Containing Vaccine Efficacy against Ovine Enzootic Abortion

## TL;DR

A new vaccine candidate using inactivated Chlamydia and flagellin as an adjuvant shows promise in preventing ovine abortion and fetal loss in sheep.

## Contribution

The study introduces a novel inactivated vaccine candidate with recombinant flagellin as an adjuvant for combating Chlamydia abortus in sheep.

## Key findings

- The vaccine candidate significantly reduced Chlamydia abortus shedding in vaccinated sheep.
- No abortions occurred in the vaccinated group, unlike the control group.
- Vaccinated sheep gave birth to viable lambs, while the control group had weak and nonviable births.

## Abstract

Chlamydia abortus is the etiological agent of abortion and fetal loss in sheep, goats and bovine cattle in many countries. Even though commercially available vaccines can reduce the incidence in sheep, the development of new, safe, and effective vaccines remains high on the agenda. In this study, an evaluation was made of the efficacy of a vaccine candidate, an inactivated antigen based on the extract of outer membrane proteins of a C. abortus strain known as Chlamydia VNITIBP-21, in combination with recombinant flagellin as an adjuvant. Pregnant sheep (n = 43) were divided into three groups: an experimental vaccinated group, a control infected group and a control non-infected group. The sheep were vaccinated twice, with an interval of 3 weeks, then infected with the homologous virulent strain of Chlamydia abortus on pregnancy day 75. The vaccine candidate reduced C. abortus shedding in vaginal swabs considerably, in comparison with the control group. In addition, ewes in the experimental group experienced no abortions, while those in the control group experienced instances of abortion, as well as births of weak and nonviable lambs. The findings show that the vaccine candidate proved itself to be promising in combatting the agent of ovine abortion and fetal loss.