Association of polymorphism at COL3A and CTLA4 loci on chromosome 2q31-33 with the clinical phenotype and in-vitro CMI status in healthy and leprosy subjects: a preliminary study.
Two genetic loci, viz. COL3A and CTLA4, located within the chromosome 2q31-33 region in the vicinity of the proposed syntenic site of the mouse "Bcg" locus were genotyped by the polymerase chain reaction in leprosy patients and healthy individuals. All the subjects studied were assessed as in-vitro responders/non-responders to mycobacterial antigens. Simple sequence length polymorphism analysis revealed five (236 to 312 bp) and eight (84 to 120 bp) allelomorphs for COL3A and CTLA4, respectively. Our preliminary analysis showed a significant association between the 250-bp COL3A allelomorph in the homozygous condition and the multibacillary form of leprosy (P < 0.05: relative risk = 5.5). Another allelic (312 bp) variant of COL3A was significantly correlated with non-responsiveness to M. leprae antigens in vitro (P < 0.01). The 104-bp allelomorph of CTLA4 was not observed in any of the 25 cases of leprosy. This absence was statistically significant (P < 0.05) when compared with normal healthy controls and depicted a high relative risk (RR = 25.83). An additional observation of the predominance of a unique 84-bp CTLA4/CTLA4-like allelomorph was observed in the Indian subjects studied.