Asymptomatic Salmonella enterica serovar Enteritidis carrier state in poultry has serious consequences on food safety and public health due to the risks of food poisoning following consumption of contaminated products. An understanding the mechanisms of persistence of Salmonella in the digestive tract of chicken can be achieved by a better knowledge of the defects in the control of infection in susceptible versus resistant animals. The gene expression of innate immune response factors including anti-microbial molecules, inflammatory and anti-infectious cytokines was studied in the caecal lymphoid tissue associated with the carrier state. Expression levels of these genes were assessed by real-time PCR and were compared in two inbred lines of chickens differing in resistance to the carrier state following oral inoculation of S. enterica serovar Enteritidis at I week of age. No correlation was observed between resistance/susceptibility to caecal carrier state and level of interleukin (IL)-1beta, IL-8, IL-18, inducible NO synthase (iNOS) and natural resistance associated macrophage protein 1 (NRAMP1). A high baseline level of defensin gene expression was recorded in young animals from the susceptible line. In contrast, a significantly low expression of interferon-gamma (IFN-gamma) gene was observed in these susceptible infected animals in comparison to resistant ones and healthy counterparts. IFN-gamma expression level represents a valuable indication of immunodeficiency associated with persistence of Salmonella in the chicken digestive tract, and IFN-gamma thus represents a factor to consider in the development of prophylactic measures for the reduction of Salmonella carrier state.

The CD45 (leucocyte common) antigen is a haemopoietic cell specific tyrosine phosphatase essential for antigen receptor signalling in lymphocytes, and expression of different CD45 isoforms is associated with distinct functions. Here we describe a novel polymorphism in exon 4 (A54G) of the gene encoding CD45 (PTPRC) that results in an amino acid substitution of Thr-19 to Ala in exon 4. The 54G allele was identified in African Ugandan populations and was found with a suggestive but not statistically significant increase in frequency amongst HIV-seropositive Ugandans. This suggests that the 54G variant and CD45 splicing abnormalities might be associated with HIV infection

The comparative intradermal skin test, in which a delayed type hypersensitivity (DTH) response to purified protein derivative of tuberculin (PPD) from Mycobacterium bovis and M. avium is assessed and compared, may be used repeatedly on non-infected animals on farms where bovine tuberculosis (TB) has occurred. A skin test is known to affect subsequent skin tests in infected animals. The reported study was to determine whether repeated skin testing prior to infection with M. bovis might affect the development of the comparative skin test and IFN? response subsequent to exposure to virulent M. bovis. The comparative intradermal skin test was applied to one group of six calves five times at 8-week intervals. These and six control calves were subsequently inoculated intratracheally with a dose of M. bovis that produced mild disease. The development of the DTH reaction, IFN?, IL-10 and proliferative responses were compared in the two groups of animals. No differences in IFN?, IL-10 and proliferative responses were seen between the two groups of calves prior to challenge. After infection with M. bovis no differences in the development of the DTH and IFN? responses to PPD were noted as a consequence of the repeated skin testing prior to challenge. No differences between the groups were evident when ESAT-6 was used as antigen and IFN? was assayed, although two animals that responded to PPD did not respond with ESAT-6. However, there did appear to be subtle effects of repeated skin testing on the immune response post-challenge that did not affect the diagnostic tests. After challenge control animals showed greater proliferative responses than animals given repeated skin tests prior to challenge, indicating that the procedure did have consequences for immune responses following infection. In both groups a marked reduction in the intensity of the skin test and in the number of animals that would be recognized as reactors was evident when animals were tested 15 weeks post-infection compared to their responses 8 weeks earlier that could have consequences for diagnosis of TB. An antibody response was not evident as a result of repeat skin testing prior to infection but was seen in both groups of calves following skin testing performed 7 weeks after infection.