In recent several studies, it has been reported that Brucella is having mainly five virulence factors that are necessary for intracellular survival and infection, including virB T4SS (Comerci et al., 2001; de Jong et al., 2013), cyclic b-glucan (Martirosyan et al., 2012), two- component sensory and regulatory system BvrS/BvrR (Martin-Martin et al., 2012), Brucella LPS (BrLPS) (Lapaque et al., 2005) and pathogen-associated molecular patterns
Naturally occurring cell-wall polysaccharides, beta-glucans, are examples of such conserved non-self-molecules collectively referred to as microbe- or pathogen-associated molecular patterns
(MAMPs or PAMPs).
They respond to 'pathogen-associated molecular patterns
(PAMP)' and 'danger-associated molecular patterns (DAMP).
TLRs 1,2,4,5,6 and 11 are located on the plasma membrane of cells of the innate immune system and epithelial cells and recognise a range of pathogen-associated molecular patterns
found on the cell-wall of bacteria, including lipopeptides (TLRs1 and 6), lipoteichoic acids and lipoproteins (TLR2), lipopolysaccharides (TLR4), and bacterial flagellin (TLR5), while TLR11 interacts with less well-defined ligands on uropathogenic bacteria; (3) the remaining TLRs are located cytoplasmically in endosomes where they interact with viral double-stranded (TLR3) and singlestranded RNA (TLRs7 and 8), and with bacterial and viral DNA via interactions with so-called unmethylated CpG sites (TLR9), which are rarely encountered on the human genome.
Scientists had generally accredited this observation to "pathogen-associated molecular patterns
" (PAMPs) on viruses and other microbes.