Immunogenicity of a Lipopolysaccharide Brucella melitensis Vaccine in Goats: An Exploratory Study

Brucella melitensis is considered one of the most widespread zoonotic pathogens worldwide. Vaccination remains the most cost-effective strategy for controlling B. melitensis infection in small ruminants.

In this study, we evaluated the immunologic responses and protection against experimental challenge in 18 goats vaccinated with either lipopolysaccharide (LPS) from B. melitensis strain 16M (LPS alone), LPS of B. melitensis strain 16M and MONTANIDE™ ISA 61 VG adjuvant (Seppic; 50 Bd national, 92250 La Garenne-Colombes, France) (LPS + ISA 61 VG), or saline as a control.

Goats (n = 6) vaccinated with LPS + ISA 61 VG had greater (p < 0.05) antibody responses than those that were nonvaccinated. Our data demonstrate that goats vaccinated with LPS + ISA 61 VG exhibited greater lymphocyte proliferative responses (p < 0.05) to the LPS antigen than those vaccinated with LPS alone at week 12 after vaccination. However, proliferative responses of peripheral blood mononuclear cell (PBMC) from goats vaccinated with LPS + ISA61VG did not differ (p > 0.05) from responses of PBMC from control goats. CD4+, CD8+, and γδ T cells from all vaccinated goats had negligible proliferation and failed to induce antigen-specific IFN-γ production. Control and vaccinated goats did not differ (p > 0.05) in their protection against abortion, uterine, fetal, mammary, or maternal infection.

Our data suggests that LPS + ISA 61 VG induces a robust humoral response but negligible cellular responses. Our data also suggest that LPS + ISA 61 VG or LPS alone would not be efficacious for use as a vaccine in goats, but the LPS + ISA 61 VG inoculum may be beneficial as a booster. Additional trials would be necessary to evaluate the vaccine's efficacy as a booster inoculation for small ruminants.