POLYMORPHISM IN GENOMIC REGIONS LINKED TO RESISTANCE AGAINST BRUCELLOSIS IN CATTLE AND BUFFALO
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Date
2023-04
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SRI VENKATESWARA VETERINARY UNIVERSITY TIRUPATI - 517 502. (A.P.) INDIA
Abstract
Brucella abortus causes bovine brucellosis, a prevalent reproductive disease
with high zoonotic potential where the host immune response plays a critical role in
disease prevention. Toll-Like Receptors (TLRs) are the type of receptors that serve as
the body's first line of defense against pathogens thus conferring resistance to various
diseases. They distinguish invading pathogens as well as endogenous substances from
damaged cells and are critical in bridging the gap between innate and adaptive
immunity. The current study sought to identify genetic polymorphisms in TLR1 and
TLR2 and their association with natural resistance to brucellosis. Mutations in the
coding regions of TLR1 (+1380 G/A) and TLR2 (T385G) were used to identify the
polymorphism in 362 samples of cattle and buffalo using PCR-RFLP. To know the
association of SNPs with the disease, a case-control study has been made with 222
samples of which 41 samples resulted as positive (case) and 181 as negative (control)
in both RBPT and ELISA. In TLR1/AciI locus, the “GG” genotype was predominant in
Murrah, Holstein Friesian crossbreds, and Jersey crossbreds while indigenous cattle
solely genotyped to “GG”. In the TLR2-EcoRV locus, “GG” genotype was prevalent
in Murrah and indigenous cattle breeds, whereas the “TT” genotype was prevalent in
crossbred cattle. Murrah buffaloes in TLR1 and TLR2, and Ongole cattle in TLR2 had
deviated from the Hardy-Weinberg equilibrium (P<0.01). The logistic regression
analysis for TLR1 could not be performed; however, for the TLR2 (T385G) locus, the
Odds Ratio (OR) of T/T against G/G - G/T was 0.17 (0.02-1.46; 95% CI), indicating
that the ‘T’ allele had a lower relative risk of brucellosis incidence than the ‘G’ allele.
The odds ratios of HF crossbreds and Ongole were 0.43 and 0.23, respectively,
indicating that they were brucellosis-resistant, but it was observed that Punganur cattle
had a significant risk of infection (OR=1.71). In the present investigation, selection
against TLR2(T385G) may reduce the risk of brucellosis in bovine herds however, due
to the small sample size of Jersey crossbred and Punganur the computed estimates
were not reliable.