Hepatitis B infection in institutionalized Down's syndrome inmates: a longitudinal study with five hepatitis B virus markers.
A 3-year longitudinal survey in a residential institution for the mentally retarded was carried out to study the epidemiology of hepatitis B virus (HBV) and to elucidate the different responses which Down's syndrome (DS) and non-Down's (ND) subjects have to HBV infection. Sensitive tests for the HBV surface antigen and antibody (HBsAg and anti-HBs), core antibody (anti-HBc) and `e' antigen and antibody (HBeAg and anti-HBe) were used. The HBsAg and anti-HBs content of positive sera was quantitated accurately. 
 
All twenty-six chronic carriers of HBsAg possessed anti-HBc and 73% possessed HBeAg. The presence of HBeAg was correlated with abnormal liver function and high titres of HBsAg. The fifty-nine DS inmates possessing anti-HBs at the beginning of the study had significantly lower anti-HBs titres than the corresponding forty-nine ND subjects, but had a higher frequency of both anti-HBc and anti-HBe. Within both DS and ND groups the presence of anti-HBe was correlated with higher anti-HBs titres and within the ND group, high anti-HBs titres were also correlated with the presence of anti-HBc. Most inmates possessing HBV markers at the beginning of the study retained them for its duration. 
 
Of the initially seronegative inmates, proportionately more DS (88%) than ND (54%) acquired HBV markers during the study; of these converters, proportionately more DS than ND (33% vs 10%) infections had chronic HBsAg carriage as the outcome. Most of these chronic HBsAg cases also acquired persistent HBeAg. In those seronegatives converting to anti-HBs, anti-HBc and anti-HBe tended to be more frequent in DS than ND groups, and patients with anti-HBe possessed higher anti-HBs titres than those without anti-HBe. These findings were similar to those seen in those inmates positive for anti-HBs at the beginning of the study (the anti-HBs group). However, unlike the anti-HBs group, the peak anti-HBs titres achieved after primary HBV infection (seroconversion) tended to be higher in the DS than in the ND group. The latter results are interpreted as indicating that a deficient humoral response in DS inmates is unlikely to be responsible for the high rates of chronic HBsAg carriage so often seen in these subjects.