Complement C4 deficiency and HLA homozygosity in patients with frequent intraoral herpes simplex virus type 1 infections

Three consecutive patients with no apparent immunodeficiency who had freque nt intraoral herpes simplex type 1 recurrences, a rare complication of herp es simplex virus infection, were found to have a total deficiency of either the A or B isotype of the complement component C4 and to be homozygous for the studied HLA antigens. A combination of HLA homozygosity, which may lea d to impaired T cell recognition of viral peptides, and deficiency in the c lassical complement pathway, which can compromise virus neutralization, may predispose to severe and frequent herpes simplex virus infections.