Toll like receptor-4 gene expression assay in mastitis caused by Stapylococcus aureus in crossbred cattle

Mastitis is inflammation of mammary gland characterized by infiltration of leukocytes in udder tissue in response to various bacterial invasions. Staphylococcus aureus is the etiological agent more commonly associated to the disease and is normally related to both subclinical and chronic infections leading to severe economic loss to dairy farms. TLR4 is involved in the initiation of the immune response to different pathogens, including Gram-negative and Gram-positive bacteria, fungi, and viruses. This study was carried out to assess the expression of TLR4 gene in spontaneous bovine sub-clinical and clinical mastitis caused by S. aureus. RNA isolated from milk somatic cells was converted as cDNA using oligo (dT) primers. mRNA expression of TLR4 was analysed by RT-qPCR system. The mRNA expression of TLR4 gene in sub-clinical mastitis was higher (2.22 fold) than clinical case (1.62 fold) when compared to normal bovine case. The expression of TLR4 gene at high level during sub-clinical stage of infection, may be subsided itself without precipitating into clinical mastitis. This study sheds light into the innate immune system represents the first line of defence in the host response to infection and is poised to immediately recognize and respond to the earliest stages of infection.