Evaluation of the immunogenicity and the protective efficacy in mice of a DNA vaccine encoding SP41 from Brucella melitensis

Ayman Al-Mariri,Abdul Qader Abbady

doi:10.3855/jidc.2296

Abstract

Brucella melitensis is a facultative intracellular Gram-negative bacterial pathogen that may enter the host via ingestion or inhalation, or through conjunctiva or skin abrasions. Some Brucella spp surface proteins (SPs) play an important role in bacterial adhesion and invasion and thus represent targets for the host immune system. Brucella spp surface protein with apparent molecular mass of 41 kDa interacts selectively with HeLa cells. To evaluate the role of SP41 (41 kDa) as a DNA vaccine against Brucella spp., pCISP41, a plasmid construct for protein expression in mammalian cells, was established. Exogenous SP41 was detected in pCISP41-transfected Vero cell line by immune blotting using specific polyclonal antibody. The protective role of pCISP41 against B. melitensis 16M in mice was evaluated by measuring B and T cell responses in comparison to those achieved with attenuated B. melitensis Rev. 1 vaccine. BALB/c mice injected with pCISP41 were able to develop SP41-specific serum immunoglobulin G (IgG) antibodies. In addition, splenocytes from DNA-SP41-vaccinated mice elicited a T-cell-proliferative response and also induced gamma interferon (IFN-γ) production, but not interleukin-5 (IL-5), suggesting the induction of a T-helper-1-dominated immune response. Vaccination with attenuated B. melitensis Rev.1 strain induced better protection levels than DNA vaccination with SP41 against B. melitensis 16M in mice. Such responses play an important role against intracellular infecting agents such as Brucella spp. Altogether, our data suggest that SP41 may represent a promising candidate for DNA vaccination against brucellosis, but more investigation to increase its protective efficacy should be done.

Highlights

Brucella melitensis is a facultative intracellular Gram-negative bacterial pathogen that may enter the host via ingestion or inhalation, or through conjunctiva or skin abrasions
To verify the ability of the constructed DNA vaccine to be correctly expressed in mammalian cells, we transformed Vero cells with pCISP41 and the expression of exogenous SP41 was shown by Western blot assay using a homemade SP41-specific polyclonal antibody (Figure 1)
To evaluate the induction of humoral immunity using pCISP41 as DNA vaccination in mice, the titers of anti-SP41 antibodies in mouse sera were measured by enzyme-linked immunosorbent assay (ELISA), using total B. melitensis lysate or recombinant SP41 protein (rSP41) as immobilized antigens

Summary

Introduction

Brucella melitensis is a facultative intracellular Gram-negative bacterial pathogen that may enter the host via ingestion or inhalation, or through conjunctiva or skin abrasions. Methodology: To evaluate the role of SP41 (41 kDa) as a DNA vaccine against Brucella spp., pCISP41, a plasmid construct for protein expression in mammalian cells, was established. The protective role of pCISP41 against B. melitensis 16M in mice was evaluated by measuring B and T cell responses in comparison to those achieved with attenuated B. melitensis Rev. 1 vaccine. Because of the economic losses to the sheep and goat industry caused by B. melitensis, as well as the zoonotic infections caused by these bacterial species, great efforts were made to eradicate ovine brucellosis worldwide [3]. To achieve this objective, a vaccine strain of B. The historical basis of DNA vaccines rests on the observation that direct in vitro and in vivo gene transfer of recombinant DNA by a variety of techniques resulted in the expression of protein [11]

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