Studies on pathology, cytokine gene expression and molecular typing of Mycobacterium avium subsp. paratuberculosis of naturally occurring Johne's disease in bullocks

Seroepidemiology of paratuberculosis in cattle population of organized and unorganized farms of India

Serum samples (531) collected randomly from cattle of organized (200) and unorganized (331) farms of Central and Northern parts of India were subjected to a commercial ELISA to know the seroprevalence of paratuberculosis. These serum samples were also tested by an in-house absorbed ELISA developed in the laboratory and the results were compared. The overall seroprevalence of paratuberculosis in cattle was 8.09% with significantly higher prevalence in cattle of organized farms (13.5%) than unorganized farms (4.83%). The seroprevalence was also significantly higher in calves (17.24%) than adults (7.57%); whereas there was no significant difference in prevalence rate among male (6.71%) and female (9.87%) cattle. Region wise the seroprevalence was slightly higher in organized farms of Northern India (16.43%) than that of Central India (11.81%). The sensitivity and specificity of in-house ELISA were 71.11% and 98.76%, respectively, with the accuracy of over 96%. On the basis of Kappa-test, the inhouse ELISA was in good agreement with commercial Pourquier ® ELISA and can be recommended for screening of paratuberculosis infection in cattle in India.

The role of IL-10 in Mycobacterium avium subsp. paratuberculosis infection

Mycobacterium avium subsp. paratuberculosis (MAP) is an intracellular pathogen and is the causative agent of Johne's disease of domestic and wild ruminants. Johne's disease is characterized by chronic granulomatous enteritis leading to substantial economic losses to the livestock sector across the world. MAP persistently survives in phagocytic cells, most commonly in macrophages by disrupting its early antibacterial activity. MAP triggers several signaling pathways after attachment to pathogen recognition receptors (PRRs) of phagocytic cells. MAP adopts a survival strategy to escape the host defence mechanisms via the activation of mitogen-activated protein kinase (MAPK) pathway. The signaling mechanism initiated through toll like receptor 2 (TLR2) activates MAPK-p38 results in up-regulation of interleukin-10 (IL-10), and subsequent repression of inflammatory cytokines. The anti-inflammatory response of IL-10 is mediated through membrane-bound IL-10 receptors, leading to trans-phosphorylation and activation of Janus Kinase (JAK) family receptor-associated tyrosine kinases (TyKs), that promotes the activation of latent transcription factors, signal transducer and activators of transcription 3 (STAT3). IL-10 is an important inhibitory cytokine playing its role in blocking phagosome maturation and apoptosis. In the current review, we describe the importance of IL-10 in early phases of the MAP infection and regulatory mechanisms of the IL-10 dependent pathways in paratuberculosis. We also highlight the strategies to target IL-10, MAPK and STAT3 in other infections caused by intracellular pathogens.