Intra‐ and inter‐breed variation in immune response to acute and sub‐chronic <i>Salmonella</i> infection and commercial immune‐stimulant in two‐layer breeds

Abstract

Salmonella is one of the most hazardous diseases in poultry farms. Markedly, the application of active immunostimulants is illustrated as potential protective agents against infection in poultry farms. Thus, this work aimed to explore inter- and intra-breed variation in response to acute and subchronic Salmonella enteritidis infection in two-layer breeds (one commercial [Hy-line strain] and another native [Fayoumi breed]). Besides exploring the possible protective effect of a commercial immune modulator (STIMULAN) on the two breeds during the acute infection. The ELISA antibody titer in sub-chronic infections and the expression analysis of some selected genes (IL-1β, LITAF, TGF-β, HSP90 and HSP70) are used as the clinical signs for acute infections to assess the possible protective role of a commercial immunomodulator (STIMULAN). Five groups were used during the acute experiment: G1-control; G2a-susceptible; G2b-resistant birds, G3-which received STIMULAN and G4-which received the infection + STIMULAN. The groups with sub-chronic infections include G1 (control), G2 (high antibody titer) and G3 (low antibody titer). The gene expressions among the susceptible birds during acute infection of both breeds are nearly similar. They only differ in the expression of HSP90 in the Fayoumi breed. However, the resistant birds vary in their gene expression profile. The effect of STIMULAN as a feed additive in non-infected birds was an up-regulation of LITAF, TGF-β, HSP90 in Fayoumi. Moreover, a powerful stimulatory role was observed when both breeds were infected. Both breeds were asymptomatic during the sub-chronic infection. Although, the increased expression of inflammatory-related genes in the Hy-line was considered as an indication of infection persistence. Fayoumi is capable of immune clearance for this infection. Thus, the Fayoumi breed is more resistant to acute Salmonella infection. HSP90 plays a vital role in its resistance. We recommend the use of STIMULAN as an immunomodulator during Salmonella infection.