Improved influenza viral vector based Brucella abortus vaccine induces robust B and T-cell responses and protection against Brucella melitensis infection in pregnant sheep and goats

PLoS One. 2017 Oct 12;12(10):e0186484. doi: 10.1371/journal.pone.0186484. eCollection 2017.

Abstract

We previously developed a potent candidate vaccine against bovine brucellosis caused by Brucella abortus using the influenza viral vector expressing Brucella Omp16 and L7/L12 proteins (Flu-BA). Our success in the Flu-BA vaccine trial in cattle and results of a pilot study in non-pregnant small ruminants prompted us in the current study to test its efficacy against B. melitensis infection in pregnant sheep and goats. In this study, we improved the Flu-BA vaccine formulation and immunization method to achieve maximum efficacy and safety. The Flu-BA vaccine formulation had two additional proteins Omp19 and SOD, and administered thrice with 20% Montanide Gel01 adjuvant, simultaneously by both subcutaneous and conjunctival routes at 21 days intervals in pregnant sheep and goats. At 42 days post-vaccination (DPV) we detected antigen-specific IgG antibodies predominantly of IgG2a isotype but also IgG1, and also detected a strong lymphocyte recall response with IFN-γ production. Importantly, our candidate vaccine prevented abortion in 66.7% and 77.8% of pregnant sheep and goats, respectively. Furthermore, complete protection (absence of live B. melitensis 16M) was observed in 55.6% and 66.7% of challenged sheep and goats, and 72.7% and 90.0% of their fetuses (lambs/yeanlings), respectively. The severity of B. melitensis 16M infection in vaccinated sheep and goats and their fetuses (index of infection and rates of Brucella colonization in tissues) was significantly lower than in control groups. None of the protection parameters after vaccination with Flu-BA vaccine were statistically inferior to protection seen with the commercial B. melitensis Rev.1 vaccine (protection against abortion and vaccination efficacy, alpha = 0.18-0.34, infection index, P = 0.37-0.77, Brucella colonization, P = 0.16 to P > 0.99). In conclusion, our improved Flu-BA vaccine formulation and delivery method were found safe and effective in protecting pregnant sheep and goats against adverse consequences of B. melitensis infection.

MeSH terms

  • Abortion, Spontaneous / prevention & control
  • Animals
  • Antibodies / immunology
  • Antigens, Bacterial / genetics
  • Antigens, Bacterial / immunology
  • Antigens, Bacterial / metabolism
  • B-Lymphocytes / cytology
  • B-Lymphocytes / immunology*
  • B-Lymphocytes / metabolism
  • Bacterial Outer Membrane Proteins / genetics
  • Bacterial Outer Membrane Proteins / immunology
  • Bacterial Outer Membrane Proteins / metabolism
  • Bacterial Proteins / genetics
  • Bacterial Proteins / immunology
  • Bacterial Proteins / metabolism
  • Brucella Vaccine / genetics
  • Brucella Vaccine / immunology*
  • Brucella Vaccine / metabolism
  • Brucella melitensis / genetics*
  • Brucella melitensis / pathogenicity
  • Brucellosis / immunology
  • Brucellosis / prevention & control*
  • Female
  • Goats
  • Hemagglutinins, Viral / immunology
  • Immunoglobulin G / immunology
  • Interferon-gamma / metabolism
  • Lipoproteins / genetics
  • Lipoproteins / immunology
  • Lipoproteins / metabolism
  • Orthomyxoviridae / genetics*
  • Pregnancy
  • Sheep
  • Superoxide Dismutase-1 / genetics
  • Superoxide Dismutase-1 / immunology
  • Superoxide Dismutase-1 / metabolism
  • T-Lymphocytes / cytology
  • T-Lymphocytes / immunology*
  • T-Lymphocytes / metabolism
  • Vaccination

Substances

  • Antibodies
  • Antigens, Bacterial
  • Bacterial Outer Membrane Proteins
  • Bacterial Proteins
  • Brucella Vaccine
  • Hemagglutinins, Viral
  • Immunoglobulin G
  • Lipoproteins
  • OMP19 protein, Brucella abortus
  • Interferon-gamma
  • Superoxide Dismutase-1

Grant support

This work was supported by a grant from the Science Committee of the Ministry of Education and Science of the Republic of Kazakhstan (grant no. 1296/GF4) (http://sc.edu.gov.kz/ru). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. NP and KT are employed by Vaxine Pty Ltd. Vaxine Pty Ltd provided support in the form of salaries for authors NP and KT, but did not have any additional role in the study design, data collection and analysis, decision to publish, or preparation of the manuscript. The specific roles of these authors are articulated in the "author contributions" section.