Haemophilus influenzae type b disease in twins

Invasive Haemophilus influenzae infections in household contacts of patients with Haemophilus influenzae meningitis and epiglottitis

In a retrospective nation-wide Swedish study of Haemophilus influenzae meningitis and epiglottitis, a total of 500 cases of culture-verified meningitis and 841 cases of epiglottitis fulfilling strict clinical criteria were found during a three-year period. Eight families with two cases of these infections occurring with an interval of less than 60 days were identified. Four of the secondary cases occurred in siblings and four in mothers of the index case. Two of the secondary cases were twins to the index case. This shows that the risk of developing invasive H. influenzae infections is considerably increased in both siblings and parents of patients with invasive infection. Rifampicin prophylaxis, which is recommended in the United States for family contacts, would, however, prevent less than 1% of all invasive infections with H. influenzae.

Genetic factors in Haemophilus influenzae type b disease susceptibility and antibody acquisition

Because Alaskan Eskimos have the greatest known endemic risk of Haemophilus influenzae type b (Hib) disease and represent a comparatively homogeneous population, we selected this population to evaluate the presence or absence of an association of 35 genetic markers (alleles or allotypes) at 12 chromosomal loci with susceptibility to both invasive Hib disease risk and level of Hib anticapsular antibody. We studied nearly all Alaskan Eskimo children who had had invasive Hib disease between 1971 and 1982 in southwestern Alaska (n = 103) and an equivalent number of controls matched for age, race, and village of residence, and verified not to have had proved or suspected Hib disease. We found no significant associations with Hib disease for the single alleles of HLA-A, -B, -C, -DR, Gm, Km, Am, Kidd, MNSs, ABO, esterase D, or glutamate pyruvate transaminase loci. However, we observed a significant interaction of two loci, Gm(a;..;g,s,t) allotype and HLA-DR8 (P = 0.002), with increased Hib disease susceptibility, and an interaction of the same Gm allotype and HLA-DR5 with decreased disease susceptibility (P = 0.01). We also compared the level of anticapsular antibody to Hib with each genetic marker and two-locus interactions, but no genetic association with antibody level was found. We conclude that some genetic factors contribute to the susceptibility to invasive Hib disease in this population.