Effects of cyclosporin A on the immune responses and pathogenesis of a virulent strain of Mycoplasma gallisepticum in chickens

Abstract

Immune responses to the virulent S6 strain of Mycoplasma gallisepticum in immunocompetent and cyclosporin A (CsA)-treated specific pathogen free chickens were investigated, and pathogenesis of the M. gallisepticum strain was also examined. Ten-day-old specific pathogen free chickens were inoculated by eye-drop with M. gallisepticum, and a control uninfected group was inoculated with mycoplasma broth. Blood was collected weekly for 4 weeks from five birds in each group and whole blood lymphocyte transformation assayed against concanavalin A and lipopolysaccharide. Blood samples were also collected at intervals for serological assays. Live body weight, clinical signs and lesions were monitored, and recovery of M. gallisepticum was attempted from choanal cleft of live birds and also from various sites at necropsy. In parallel to the aforementioned groups, another set of two groups of chicks treated with CsA was infected with M. gallisepticum S6 or mycoplasma broth. These groups were subjected to the same experimental procedures. In the immunocompetent chickens, M. gallisepticum caused temporary T-cell suppression at 2 weeks post-infection. Comparison of the clinical signs and macroscopic lesions produced in immunocompetent and CsA-treated chickens indicated that T cells may not play an active role in disease development. The percentage of birds with mycoplasma isolation and the load of mycoplasmas suggested that T cells may have some role in resisting mycoplasma colonization or in the elimination of the infection.

Rapid evolution of disease resistance is accompanied by functional changes in gene expression in a wild bird

“…MG is well known for its complex immunomodulatory effects in poultry, which include the suppression of important immune processes a week or two after MG inoculation (22,23). Consistent with the evolution of reduced susceptibility to immunomodulation, Alabama finches showed greater up-regulation (or increased expression compared with infected Arizona finches) of immune-related genes, 2 wk postinfection.…”

“…In addition, MG can also have immunosuppressive effects (23), particularly on later stages of the immune response (24). For example, 1-2 wk postinfection, MG has been shown to be associated with a decline in the infiltration of T cells in the trachea (24) and a suppression of T-cell activity (22) in chicken (Gallus gallus domesticus). There is also evidence that infection with MG is associated with a reduced humoral antibody response to other pathogens (27,28).…”

“…MG is known for its ability to manipulate host immunity in poultry (22,23). At the onset of infection, MG triggers the upregulation of proinflammatory cytokines and chemokines (23,24) and induces an inflammatory response (25), which can cause damage to host epithelia (26).…”

Poultry mycoplasmas: sophisticated pathogens in simple guise

“…gallisepticum appeared to induce transient immunosuppression in turkeys concurrently infected with avian pneumovirus (Naylor et al, 1992) and there have been reports of immunosuppression in turkeys by M. meleagridis (Ortiz et al, 1981) and M. iowae (Bradbury, 1984) but the underlying mechanisms are not known. In more recent work (Ganapathy and Bradbury, 2003) a virulent strain of M. gallisepticum was shown to cause temporary T cell suppression in infected chickens. …”

An Assay in Microtitre Plates for Absolute Abundance of Chicken Interferon Alpha Transcripts

“…It has been known since the early 1970s that mycoplasmas are immunosuppressive in several species (Kaklamanis and Pavlatos 1972), chickens among them (Nonomura 1973;Ganapathy and Bradbury 2003). Mycotoxins are immunosuppressive but their effects can be prevented by quality control of feedstock to avoid feeding contaminated feed (Devegowda and Murthy 2005).…”