Evaluation of the aroA mutant of Corynebacterium pseudotuberculosis in cellular and murine models

Abstract

Caseous lymphadenitis of small ruminants causes economic losses worldwide. To date, no effective vaccine has been developed against the causative agent of this disease, Corynebacterium pseudotuberculosis. The objective of the present work was to evaluate an aroA mutant gene strain of C. pseudotuberculosis in cellular and murine models, for attenuation and the ability to stimulate an immune response. The intracellular survival of the aroA mutant strain and the wild type strain (WT) of C. pseudotuberculosis was evaluated in J774A.1 murine macrophages using a multiplicity of infection (MOI) of 1:1 with the following infection times: 30 min, and 1, 2, 4, 8, 12, and 24 h. The largest difference in the intracellular survival of the mutant was observed 30 min post-infection. After subcutaneous skin vaccination, the subcutaneous lesion progression observed on the 14 th day was more severe in those animals that were vaccinated with the WT strain. An analysis of the residual virulence in the murine model did not reveal any bacteria in mice vaccinated with the aroA strain on day 28 post-vaccination. Mice vaccinated with the mutant showed 50 % protection against the intraperitoneal challenge, exceeding that of the control group (41.67 %). We conclude that the virulence of the aroA mutant was significantly attenuated in both cellular and murine models according to the residual virulence detected in mice. However, vaccination with the mutant failed to confer at least 80 % protection, which is desirable for an immunogen. Hence, this study contributes to the knowledge of the immune response against Corynebacterium pseudotuberculosis.