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The serologic reactivity and epidemiology associated with different hepatitis C virus (HCV) variants were investigated in a cohort of 113 anti-HCV-positive donors. In Scotland, HCV type 1 accounted for one-half of all infections; 40 percent of subjects were infected with HCV type 3, and the remainder were infected with type 2. Reactivity with the NS-4-encoded antigens in the first-generation anti-c100 assay was absent in 68 percent of donors infected with types 2 and 3, as compared with 10 percent for those infected with type 1. Even when combined with surrogate marker testing, first-generation tests would have failed to detect 12 percent of HCV-infected blood donors. The age distribution, incidence of past infection with hepatitis B virus, and reported risk factors were similar in donors infected with types 1 and 3 (mean ages were 31.9 and 29.9; 18 and 17.5% were positive for antibody to hepatitis B core antigen; and 47 and 48% had past intravenous drug abuse). However, the distributions of alanine aminotransferase levels were significantly different in those infected with type 3 (abnormally raised in 83%) and those infected with type 1 (55% abnormal alanine aminotransferase; p < 0.05) or type 2 (60%; p < 0.01) and those who were nonviremic (8%; p < 0.0001). These data suggest that HCV type 1 is the most common HCV infection in blood donors and that infection with HCV type 3 may be associated with more severe liver disease, because of more recent infection or because of a greater inherent pathogenicity of type 3 variants.

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SUMMARY In an attempt to correlate host and parasite-related events occurring during the course of a primary Giardia infection in the mouse we have measured epithelial cell kinetics, enzymes, and intraepithelial lymphocytes at different stages of the infection. New methods were developed for the accurate measurement of parasite numbers and distribution within the gut. In jejunum a modest decrease in villus length and intraepithelial lymphocytes at week 1 preceded a pronounced disaccharidase deficiency at week 2, the time of maximum trophozoite numbers, whereas crypt lengthening and increased cell production became maximal at week 3. As trophozoite numbers fell the intraepithelial lymphocyte count and disaccharidase values rose. With the exception of the intraepithelial lymphocyte count, which followed the same pattern as in jejunum but two weeks later, the changes seen in the ileum were the opposite of those in jejunum, suggesting rapid ileal adaptation. The results indicate that the disaccharidase deficiency associated with giardiasis is likely to represent a direct effect of the parasite on the brush border rather than enterocyte immaturity, whereas the intraepithelial lymphocyte response reflects host immunity to the parasite. Profound adaptive changes occur throughout the small intestine in response to a relatively localised insult.Infection with Giardia lamblia may be entirely asymptomatic, may produce a mild, self-limiting illness, or chronic diarrhoea with or without malabsorption. The reasons for this variation in severity are unknown at present, but among the possible causes to be considered are variations in parasite virulence, associated bacterial overgrowth in the small intestine, nutritional status, and other host factors such as the type of the immune response and its effect on the intestinal mucosa. Various abnormalities of small bowel pathology have been identified consistently in giardiasis, and these include disaccharidase deficiencies 12 increased intraepithelial lymphocyte counts3 4 and, in patients with malabsorption, crypt hyperplasia with short villi and increased lamina propria cellularity.5 6 The severity of the mucosal changes in a biopsy of proximal jejunum appears to correlate with the * On leave from the

SUMMARY Pneumatosis cystoides intestinalis (PCI) is an uncommon condition of unknown aetiology. Bacterial gas production may be an important aetiological factor, but experimental evidence in humans has been lacking. We have studied breath hydrogen excretion as an index of bacterial gas production in 12 patients with PCI and have shown that four out of five with demonstrable cysts produced unusually high levels of hydrogen while fasting. This abnormality has not been previously reported. One patient showed resolution of PCI after antibiotic treatment. These findings confirm the importance of bacterial gas production in the pathogenesis of PCI.There has been much speculation about the aetiology of pneumatosis cystoides intestinalis (PCI), an uncommon condition characterised by the presence of gas-filled cysts within the walls and mesentery of the intestine. The most widely accepted theories have proposed a mechanical origin for the cysts (Koss 1952;Keyting et al., 1961), but mechanical theories alone fail to account for the finding that hydrogen, a gas never produced by mammalian cells, may comprise up to 50 % of the gas content of the cysts (Forgacs et al., 1973).Measurement of breath hydrogen is now an established method of studying bacterial activity in the intestine (Hepner, 1974) and we have therefore studied breath hydrogen excretion in our patients with PCI.