Role of the HLA system in the association between multiple sclerosis and infectious mononucleosis.

OBJECTIVE

To determine whether multiple sclerosis (MS) and infectious mononucleosis (IM) share common HLA associations.

DESIGN

A prospective cohort study was conducted from October 1, 1999, through September 30, 2003.

SETTING

University of Edinburgh Richard Verney Health Centre, Edinburgh, Scotland.

PATIENTS: Participants included 179 individuals who underwent asymptomatic Epstein-Barr virus seroconversion and 175 patients who developed IM.

INTERVENTION: Genotyping for 5 classical HLA loci (HLA-A, HLA-B, HLA-C, HLA-DRB1, and HLA-DQB1).

MAIN OUTCOME MEASURE: Diagnosis of IM and allele frequency.

RESULTS

Allelic analysis showed that HLA-DRB1*01:01 was significantly associated with the development of IM (odds ratio, 3.2; P < .001). Patients with IM and HLA-DRB1*01:01 had a lower Epstein-Barr virus viral load compared with those without the allele (median, 783 vs 7366 copies/10(6) peripheral blood mononuclear cells; P = .03).

CONCLUSION

HLA-DRB1*01:01 is protective against developing MS; thus, a common genetic basis between IM and MS is not supported.