To explore the potential role of these genes in the susceptibility to pulmonary tuberculosis in a Mexican mestizo population, we evaluated the association of D543N and 3'-UTR polymorphisms in NRAMP1/SLC11 A1 and - 762 and A1513C polymorphisms in P2X(7) genes with the risk for tuberculosis.
Polymorphisms at the four loci had no statistically significant association between the SLC11A1 variants and susceptibility to TB in subjects of European descent, while they showed a statistically significant association in Asian subjects (except the INT4 variant), African subjects (except the 3'UTR variant) and the population as a whole (except the INT4 variant).
We then examine the putative role of iron-related host genes by focussing on two candidate genes, haptoglobin and NRAMP1, for which there are common polymorphic variants in humans with strong evidence of functionally distinct biochemical phenotypes that would be predicted to influence the course of HIV and TB infections.
The findings of the present study support the hypothesis that genetic variants of NRAMP1 may have an effect on bacilli growth and on outcomes of pulmonary tuberculosis, but not on susceptibility to M. tuberculosis infection.
These results indicate that variant alleles in the Nramp1 gene are associated with increased mycobacterial replication rather than susceptibility for tuberculosis and may thus confer increased risk of severe disease.
Human susceptibility to infectious and inflammatory diseases, including rheumatoid arthritis, inflammatory bowel disease, and tuberculosis, shows allelic association with a highly polymorphic regulatory, Z-DNA-forming microsatellite of (GT/AC)n dinucleotides within the proximal SLC11A1 promoter.
For example, tumour necrosis factor polymorphisms have been associated with susceptibility to malaria and other infections; chemokine receptor polymorphisms with susceptibility to HIV; natural resistance-associated macrophage protein 1 with tuberculosis; and mannose binding lectin polymorphisms with meningococcal disease.
Several important candidate genes like human leucocyte antigen/alleles and non-human leucocyte antigen genes, such as cytokines and their receptors, chemokines and their receptors, pattern recognition receptors (including toll-like receptors, mannose binding lectin and the dendritic cell-specific intercellular adhesion molecule-3 grabbing nonintegrin), solute carrier family 11A member 1 (formerly known as natural resistance-associated macrophage protein 1) and purinergic P2X7 receptor gene polymorphisms, have been associated with differential susceptibility to TB in various ethnic populations.
In the present study, we scanned the regulatory and coding region of Nuclear LIM Interactor-Interacting Factor gene (NLI-IF), which is physically close to the tuberculosis-associated gene NRAMP1.
Among the subjects, D543NNRAMP1 polymorphism, history of contact with TB patients, and not having a clear BCG scar on the upper arm tended to be significantly association with active TB.
To test this, we determined the frequency of an allele (SLC11A11729 + 55del4) associated with natural resistance to intracellular pathogens such as tuberculosis and leprosy.
These results indicate that variant alleles in the Nramp1 gene are associated with increased mycobacterial replication rather than susceptibility for tuberculosis and may thus confer increased risk of severe disease.
The (GT)n promoter alleles 2 and 3 (rs534448891), which alter SLC11A1 expression, were significantly associated with tuberculosis (OR=1.47 (1.30-1.66), OR=0.76 (0.65-0.89), respectively) and infectious disease (OR=1.25 (1.10-1.42), OR=0.83 (0.74-0.93), respectively).
These findings suggest that the 5'(GT)n polymorphism of NRAMP1 modifies TB susceptibility in this Caucasian population, and could possibly be related to the site of infection among HIV-negative individuals and HIV-coinfected TB.
The 469 + 14 G/C (INT4), 1465 - 85 G/A, and C274T polymorphisms of NRAMP1 and the A/C polymorphism of IL12 3'-UTR were analyzed in ethnic Russians with (N = 58) or without (N = 127) tuberculosis (TB) from Tomsk.
Similarly, no significant differences were observed between NRAMP1 polymorphisms and rheumatoid factor positivity and erosive disease in RA and localization of TB.