Evaluation of a Salmonella Vectored Vaccine Expressing Mycobacterium avium Subsp. paratuberculosis Antigens Against Challenge in a Goat Model

Abstract

Johnes disease (JD), caused by Mycobacterium avium subsp paratuberculosis (MAP), occurs worldwide as chronic granulomatous enteritis of domestic and wild ruminants. To develop a cost effective vaccine, in a previous study we constructed an attenuated Salmonella strain that expressed a fusion product made up of partial fragments of MAP antigens (Ag85A, Ag85B and SOD) that imparted protection against challenge in a mouse model. In the current study we evaluated the differential immune response and protective efficacy of the Sal-Ag vaccine against challenge in a goat model as compared to the live attenuated vaccine MAP316F. PBMCs from goats vaccinated with Sal-Ag and challenged with MAP generated significantly lower levels of IFN-γ, following in vitro stimulation with either Antigen-mix or PPD jhonin, than PBMC from MAP316F vaccinated animals. Flow cytometric analysis showed the increase in IFN-γ correlated with a significantly higher level of proliferation of CD4, CD8 and γδT cells and an increased expression of CD25 and CD45R0 in MAP316F vaccinated animals as compared to control animals. Evaluation of a range of cytokines involved in Th1, Th2, Treg, and Th17 immune responses by quantitative PCR showed low levels of expression of Th1 (IFN-γ, IL-2, IL-12) and proinflammatory cytokines (IL-6, IL-8, IL-18, TNF-α) in the Sal-Ag immunized group. Significant levels of Th2 and anti-inflammatory cytokines transcripts (IL-4, IL-10, IL-13, TGF-β) were expressed but their level was low and with a pattern similar to the control group. Over all, Sal-Ag vaccine imparted partial protection that limited colonization in tissues of some animals upon challenge with wild type MAP but not to the level achieved with MAP316F. In conclusion, the data indicates that Sal-Ag vaccine induced only a low level of protective immunity that failed to limit the colonization of MAP in infected animals. Hence the Sal-Ag vaccine needs further refinement to increase its efficacy.

Regulatory T Cell Activity and Signs of T Cell Unresponsiveness in Bovine Paratuberculosis

“…This demonstrates an attempt by PBMCs from all animals, regardless of Johne’s disease test status, to respond to MAP antigens. The Th17 response, while not unprecedented in Johne’s disease ( 30 , 31 ), may be indicative of an immune response gone astray. Critically, expression of FOXP3 mRNA was also significantly upregulated in the presence of MAP as compared to nil-stimulated samples, suggesting a role for MAP in inducing expression of FOXP3 mRNA in bovine PBMCs.…”

Invited review: The economic impact and control of paratuberculosis in cattle

“…Subunit vaccines can alleviate the problems of severe inflammation at the injection site but they have not proven very successful in preventing MAP infection (Stabel et al, 2012). However, recent advances in genomics have led to the development of live-attenuated vaccines that will completely stimulate both cell-mediated and humoral immune responses and consequently may improve protection against MAP infection (Faisal et al, 2013).…”

Generation of gene-modified goats targeting MSTN and FGF5 via zygote injection of CRISPR/Cas9 system

“…As one of the first domestic farm animals, the goat is one of the most important livestock species and provides a variety of products, including fiber, milk, meat, and hides. Furthermore, goats have also been used as a model in biomedical studies 3 4 5 . Although specific gene knockout strategies based on homologous recombination (HR) and somatic cell nuclear transfer (SCNT) have been established in goats 6 , precise gene modification of the goat genome is still challenging.…”