¹Cambridge Institute for Medical Research, Wellcome Trust/MRC Building, Addenbrooke's Hospital, Hills Road, Cambridge CB2 2XY, UK

²Department of Molecular Medicine, Karolinska Hospital, CMM L8:03, S171 76 Stockholm, Sweden

³School of Biology, University of Leeds, Leeds LS2 9JT, UK

⁴Human Genetics, Duthie Building (808), Southampton General Hospital, Tremona Road, Southampton SO16 6YD, UK

⁵MRC HGMP Resource Centre, Hinxton, Cambridge CB10 1SA, UK

⁶Research & Development Genetics Department, Zeneca Pharmaceuticals, Alderly Park, Macclesfield, Cheshire SK10 4TG, UK

⁷Instituto Evandro Chagas, Caixa Postal 3, 66.001 Belem, Brazil

⁸Departamento de Patologica, Universidade de Federal do Maranho, São Luis, Maranhão, Brazil

⁹Departamento de Parasitologia, Universidade de Piaui, Terasina, Piaui, Brazil

¹⁰London School of Hygiene and Tropical Medicine, Keppel Street, London WC1E 7HT, UK

Correspondence to: Professor J M Blackwell, CIMR, Wellcome Trust/MRC Building, Addenbrooke's Hospital, Hills Road, Cambridge CB2 2XY, UK. E-mail: jennie.blackwell@cimr.cam.ac.uk

This work was supported by grants from The Wellcome Trust, Heather Cordell (CIMR) provided valuable advice on power calculations for linkage. We would also like to thank the people of northeastern Brazil for their hospitality and for their contribution to this study.

Familial aggregation, high relative risk to siblings, and segregation analysis, suggest genetic control of visceral leishmaniasis in Brazil. Class II gene effects in mice, and high circulating tumour necrosis factor in humans, provide reasons to target HLA. Fifteen polymorphic markers across 1.03 Mb (DQB1 to TNFa) were genotyped (87 multicase families; 638 individuals). Model-based parametric analyses using single-point combined segregation and linkage in COMDS, or multi-point linkage in ALLEGRO, failed to detect linkage. Model-free nonparametric affected sibling pair (SPLINK) or NPL_all score (ALLEGRO) analyses also failed to detect linkage. Information content mapping confirmed sufficient marker information to detect linkage. Analysis of simulated data sets demonstrated that these families had 100% power to detect NPL_all scores of 5 to 6 (>LOD4; P < 0.00001) over the range (7% to 61%) of age-related penetrances for a disease susceptibility gene. The extended transmission disequilibrium test (TDT) showed no consistent allelic associations between disease and the 15 loci. TDT also failed to detect significant associations between extended haplotypes and disease, consistent with failure to detect significant linkage disequilibrium across the region. Linkage disequilibrium between adjacent groups of markers (HLADQ/DR; 82-1/82-3/-238bpTNFA; LTA/62/TNFa) was not accompanied by significant global haplotype TDT associations with disease. The data suggest that class II/III regions of HLA do not contain major disease gene(s) for visceral leishmaniasis in Brazil.

Genes and Immunity (2002) 3, 350-358. doi:10.1038/sj.gene.6363852

visceral leishmaniasis; HLA; multicase families; genetic susceptibility