Although, MAP as a zoonotic pathogen has not yet been confirmed, there is some investigations about the role of MAP in public health concern. MAP can be isolated from pasteurized milk [
3], children’s milk powder [
4], soil and surface water [
5]. Also, MAP may shed through infected animal’s feces and survive in the environment for a long period. Then the exposure of human to a contaminated environment is a potential risk [
6]. There are studies about the association of MAP with Crohn’s disease [
7], sarcoidosis and Blau syndrome [
8], type 1 diabetes [
9], Hashimoto’s thyroiditis [
10], and multiple sclerosis (MS) [
11]. This could explain the significant risk of MAP to public health safety. Among the approaches to reduce Johne’s disease in most countries, testing and culling practices are the most common [
12], but vaccination is the best control strategy and more cost-effective [
13] than other approaches. Whole-cell based vaccines, live attenuated vaccines, and inactivated vaccines were have been used until now [
12] with inadequate protection.
M. avium subsp.
paratuberculosis binds to Microfold cells (M cells) and epithelial cells through a fibronectin bridge and mycobacterial adhesins, to cross the intestinal barrier and enter into the subepithelium. Then, MAP can be picked up by antigen presenting cells and carried to regional lymph nodes [
14]. IFN-γ induced by Th
1-mediated immune responses are play a crucial role in activating macrophages to kill intracellular MAP and protection against MAP infection [
15,
16]. Gamma interferon (IFN-γ) response and antibody response can be induced by MAP. IFN-γ responses (mediated by Th
1) detected early can lead to the controlling of MAP replication and restricted bacterial shedding; but antibody responses (mediated by Th
2) detected late in infection which inhibit Th
1 and are much less effective against MAP [
15,
17,
18]. The best characterized mycobacterial adhesin is Heparin-binding hemagglutinin (HBHA). HBHA is located on the surface of mycobacteria and is important in the binding of mycobacteria to the epithelial cells [
19] during bovine tuberculosis and Johne’s disease; it is also a major target for host humoral immune response. Some studies have demonstrated that methylated HBHA causes specific IFN-γ response in latent
M. tuberculosis infection [
20,
21]. Also, there is some reports about the induction by HBHA of both CD4
+ and CD8
+ T lymphocytes producing cytokines like IFN-γ in
M. tuberculosis infection [
22,
23]. The FN-binding glycoprotein family including fibronectin attachment proteins (FAPs) is important for attachment and internalization of MAP by epithelial cells and induce Th
1 polarization and IFN-γ production in vitro [
24].
Due to the global distribution of paratuberculosis and the creation of many economic problems, as well as suspicion of zoonotic nature of the MAP, using control strategies and research to identify appropriate antigens and introduce them as vaccine candidates are important. This study describes successful expression, purification, and evaluation of cellular immune response induction ability of a chimeric fusion protein which consists of HBHA and high antigenic region of FAP-P. Triggered antigen-specific IFN-γ response of isolated PBMCs from immunized goats (with our chimeric fusion protein and the crude protein fraction prepared from the culture supernatant of MAP-PPD) to rHBHA-FAP and PPD, was measured by ELISA.