Abstract
In this study, we first evaluated the duration of a protective immune response against Brucella melitensis infection in non-pregnant sheep and goats immunized with an improved (by vaccine formulation and route of administration) commercial Brucella abortus vaccine based on influenza viral vectors expressing Brucella immunodominant Omp16, L7/L12, Omp19, or Cu-Zn superoxide dismutase (SOD) proteins (Flu-BA_Omp19-SOD). Sheep and goats in the vaccinated group were immunized thrice concurrently via the subcutaneous and conjunctival routes of administration at an interval of 21 days. Animals in the control group were administered with 20% Montanide Gel01 adjuvant in phosphate-buffered saline in the same way. We showed that the Flu-BA_Omp19-SOD vaccine in sheep and goats induces antigen-specific Th1-biased [immunoglobulin G2a (IgG2a) over IgG1] antibody response and T-cell and interferon γ responses lasting over a period of 1 month post–last vaccination (PLV). The levels of protection against B. melitensis 16M infection (vaccination efficacy) in vaccinated sheep for a period of 6 months were 0–20% and in goats 20–40% compared to control challenge group. But the severity of B. melitensis 16M infection in the Flu-BA_Omp19-SOD–vaccinated sheep and goats during the entire period of observation revealed the infection index (P = 0.001–P < 0.0001) and Brucella colonization in lymph nodes and organs (P = 0.04–P < 0.0001) were significantly lower than those in the control group. To conclude, the Flu-BA_Omp19-SOD vaccine using improved formulation and administration method in sheep and goats provides augmented antigen specific humoral and T-cell immune response lasting only for 1 month PLV and partial protection for 6 months against B. melitensis 16M infection.
Highlights
Brucellosis is a chronic infectious disease of animals and humans that induces huge economic losses globally
We developed a novel Brucella abortus vaccine based on influenza viral vector (IVV) expressing Brucellaimmunodominant outer membrane protein (Omp)16 or ribosomal L7/L12 protein (Flu-BA) [6]
In the serum of vaccinated sheep and goats, IgG antibody response to a mixture of Brucella L7/L12, Omp16, Omp19, and superoxide dismutase (SOD) proteins was at peak levels after 1 month post–last vaccination (PLV)
Summary
Brucellosis is a chronic infectious disease of animals and humans that induces huge economic losses globally. To control brucellosis in animals, vaccination is one of the most cost-effective measures, which in turn helps in protecting the health of humans in endemic areas [2]. This aids in eradication of the disease among livestock [3]. The Rev. vaccine has been found effective, it has several limitations such as it causes abortion in a fraction of vaccinated animals, the vaccine bacteria are virulent to humans, and differentiation of infected from vaccinated animals (DIVA) is a challenge [4, 5]. Development of a safe and effective vaccine to control B. melitensis infection in sheep and goats that has DIVA potential is warranted
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