Immunogenicity of a lipopolysaccharide Brucella melitensis vaccine in goats: An exploratory study

Authors: NASEER, AHSKHIL - Colorado State University; Olsen, Steven; SALMAN, MO - Colorado State University; DANIELS, JOSHUA - Colorado State University; MCCLUSKEY, BRIAN - Animal And Plant Health Inspection Service (APHIS)

Submitted to: Vaccine
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/8/2026
Publication Date: N/A
Citation: N/A

Interpretive Summary: Brucella melitensis causes reproductive losses in small ruminants and is a significant zoonotic pathogen for humans. Addressing the disease in animals is the most cost effective approach for reducing human infections with vaccination being the most important intervention tool. In this study, we evaluated a subunit vaccine to prevent brucellosis in goats and found that it induced strong antibody responses but had limited ability to prevent abortions and infections. This work is important to regulatory officials in areas with brucellosis in domestic livestock and for veterinarians and researchers that have interest in brucellosis.

Technical Abstract: 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* (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 'd T cells from all vaccinated goats had negligible proliferation and failed to induce antigen-specific IFN-' production. Control and vaccinated goats did not differ (p > 0.05) in protection against abortion, uterine, fetal, mammary, or maternal infection. The difference in the findings is limited by the low power level due to the small sample size. 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 in adults. Additional trials would be necessary to evaluate the vaccine’s efficacy as a booster inoculation for small ruminants.