Physiological response of mammary glands to Escherichia coli infection:A conflict between glucose need for milk production and immune response.

The mammary immune and physiological responses to distinct mammary-pathogenic E. coli (MPEC) strains were studied. One gland in each of ten cows were challenged intra-mammary and milk composition (lactose, fat, total protein, casein), biochemical (glucose, glucose-6-phosphate (Glu6P), oxalate, malate, lactate, pyruvate and citrate, malate and lactate dehydrogenases, lactate dehydrogenase (LDH), nitrite, lactic peroxidase, catalase, albumin, lactoferrin, immunoglobulin) and clotting parameters were followed for 35 days post-challenge. Challenge lead to clinical acute mastitis, with peak bacterial counts in milk at 16-24 h post-challenge. Biochemical and clotting parameters in milk reported were partially in accord with lipopolysaccharide-induced mastitis, but increased Glu6P and LDH activity and prolonged lactate dehydrogenase and Glu6P/Glu alterations were found. Some alterations measured in milk resolved within days after challenge, while others endured for above one month, regardless of bacterial clearance, and some reflected physiological responses to mastitis such as the balance between aerobic and anaerobic metabolism (citrate to lactate ratios). The results suggest that E. coli mastitis can be divided into two stages: an acute, clinical phase, as an immediate response to bacterial infection in the mammary gland, and a chronic phase, independent of bacteria clearance, in response to tissue damage caused during the acute phase.

The host genotype influences infectious bursal disease virus pathogenesis in chickens by modulation of T cells responses and cytokine gene expression.

The immunopathogenesis of infectious bursal disease virus (IBDV) was investigated in different layer and broiler type chickens in comparison to highly susceptible specific-pathogen-free layers (SPF-Wh-LT) often used for experimental studies. Layer-type chickens (LT) of all genetic backgrounds showed significantly higher IBDV antigen loads in the bursa of Fabricius (BF) compared to broiler type birds (BT) (P<0.05). The variation between IBDV-infected and virus-free birds in the percentage of splenic and intrabursal B cells, T cells and macrophages differed between genetic backgrounds as well as the expression levels of cytokines. The most susceptible SPF-Wh-LT showed high levels of circulating type I IFN starting at 2 days post infection (dpi) up to 7 dpi coinciding with clinical IBD, while less susceptible birds showed a delayed response. Circulating cytokine levels were poorly associated neither with intrabursal nor with splenic mRNA expression of these cytokines. Detected cytokines varied in expression levels and timing between infected groups of different genetic background. These data suggest that variations in the activity of immune cell populations contribute to differences in infectious bursal disease between birds of various genetic backgrounds.

Contribution of the genetic background to the immune response of broilers vaccinated or challenged with LPAI H9N2.

BACKGROUND: The knowledge on the immune responses to LPAI is limited. The purpose of this study was to investigate the immune responses of two divergently selected lines of broilers, a line responding with high antibody response to antigens (HH), and a line responding with low antibody titers (LL) to antigen. METHODS: Day old chicks from each line were divided in two groups, one vaccinated with inactivated H9N2 vaccine and one non-vaccinated. At 21 days of age all the chicks were challenged with field isolate of H9N2, 1X106.5 ELD50 per chick by drops to the eye, nose and beak. Twenty four hours and 14 days post challenge (PC), the chickens were weighed blood spleen and lungs were taken and leukocytes were isolated. The leukocytes were stained with monoclonal antibodies for surface markers and analyzed by flow cytometry. We used Elispot assay to identify the number of antibody producing cells in each of the organs. mRNA was extracted using TRIsol reagent in order to assess the cytokine production level by qRT-PCR using the SYBR green methods. RESULTS: Our results showed that LL-vaccinated group gained more weight than any of the other group. Using IDEXX kit, no antibody titers could be identified in vaccinated chicks 21 days post vaccination while 14 days PC vaccinated HH chickens demonstrated the highest average antibody titers. LL vaccinated chickens demonstrated higher average antibody titer than non-vaccinated LL. Using the Elispot assay no difference were found between the groups either cells producing IgA, IgM or IgY beside of a high number of IgY producing cells in the lungs of vaccinated HH birds. CONCLUSIONS: Further data on leukocytes subpopulations using flow cytometry, cytokines production (IFNγ, IL-6, IL-18, IL-2 and IL-4) isotype specific antibody responses and number and functionality of NK cells are in process.