Salmonella enterica subsp. enterica serovar Gallinarum biovar Gallinarum (SG) belongs to serogroup D of Salmonella enterica subsp. enterica and causes fowl typhoid, a disease characterized by high morbidity and mortality in birds. The control of this disease in commercial poultry farms is accomplished through a combination of biosecurity measures including vaccination of birds. SG is a host-specific biovar that is able to infect chickens of all ages. Clinical symptoms are variable between the different commercial lines of chickens. Brown Layer-hens (semi-heavy line) are susceptible to SG infection and develop severe symptoms with high mortality rates at any age. Rather the white layer-hens (light lines) are resistant to infection and show low mortality after infection. This study will evaluate the immune response against SG in two different experiments. The first study will evaluate the innate immune response after infection of layer-hens (light and semi-heavy lines). At 4h, 2 and 6 days post-infection (dpi) birds of the two lines will be sacrificed to harvest the samples and assess the bacterial infection. Additionally, the cellular immune response will be evaluated by detecting ³´ T cells and macrophages by immunohistochemistry. RT-PCR in real time will be used to quantify the expression of receptors responsible for the detection of the bacteria and proinflammatory cytokines.The other experiment will evaluate the acquired immune response triggered by an attenuated strain of SG, with deletion of genes cobS and cbiA (SGcobScbiA), with proven potential as a live vaccine against SG infection (FAPESP Proc. N. 2007/53479-0). This study seeks to identify the important elements involved in protection against challenge by pathogenic strain of SG. For this, the response will be evaluated after immunization with fifteen and 1 day before the infection (dbi) and 1, 3 and ten days after infection (dpi) with SG. The technique of RT-PCR inreal time will be used to quantify the expression of immunomodulatory cytokines and flow cytometry will be used to quantify effector T lymphocytes (CD4+CD44+ and CD8+CD44+). Additionally, the cellular immune response will be evaluated by imunohistochemistry to detect macrophages (Experiment 1) and by flow citometry to quantify effector T lymphocytes (CD4+CD44+ and CD8+CD44+). The levels of the immunoglobulins IgM and IgG will be measured by ELISA. Overall, this study was designed to generate knowledge about the different immune responses in birds vaccinated or naturally resistant or susceptible to infection by SG.
News published in Agência FAPESP Newsletter about the scholarship: