ABSTRACT— Two key lysosomal enzymes, N‐acetyl‐β‐glucosaminidase and β‐glucuronidase of Kupffer cells and blood monocytes were studied in guinea pigs infected intramesenterically with E. histolytica. The animals were sacrificed on days 0, 2, 5 and 8 post‐infection. The enzyme levels in the cell lysate and supernatants of both Kupffer cells and blood monocytes were significantly higher (P < 0.01) in the infected animals compared with the controls. This increase was more marked on the 5th and 8th days post infection (P < 0.001). The alteration in enzyme levels was higher in Kupffer cells than in blood monocytes (P < 0.05). The enzyme levels increased exponentially with the severity of the hepatic lesions. A direct correlation was observed between the enzyme levels and the severity of the hepatic lesions (P < 0.01). Hence, the role of lysosomal enzymes, released by activated mononuclear phagocytic cells, in the pathogenesis of hepatic amoebiasis is postulated.

The role of beta-glucuronidase (BG), released by blood monocytes and Kupffer cells, in the pathogenesis of intestinal amoebiasis was studied. Guinea-pigs, infected intracaecally with Entamoeba histolytica, were killed 0, 3, 7, 14 and 21 d after infection. Enhanced levels of BG were observed in the cell lysates as well as supernatants of both blood monocytes and Kupffer cells in the infected animals, from the 3rd day after infection, as compared to those in controls. The rise in BG levels was more marked on 7 and 14 d after infection (P less than 0.001). The animal which survived for 21 d had lower levels of BG, though still significantly higher than those in controls (P less than 0.05). The animals with grade IV or V caecal scoring and on the verge of death had higher levels of beta-glucuronidase. A direct correlation was observed between the enzyme levels and severity of infection. It is postulated that acid hydrolases have a role in causing tissue damage during intestinal amoebiasis.

Excretory/secretory (E/S) and somatic antigens prepared from third stage infective larvae of Ancylostoma duodenale were evaluated for the diagnosis of human hookworm infection by enzyme-linked immunosorbent assay (ELISA). Taking the mean absorbance plus 2 standard deviations (SD) of normal serum as the cut-off value, the positivity rates in 30 hookworm cases were 97% and 93% respectively. False positivity with E/S antigen was 8-20% in 61 control subjects; with somatic antigen it was slightly lower. In contrast, when the mean absorbance value plus 2 SD of control groups with other parasitic infections was taken as cut-off point, the positivity was 93% with E/S antigen and 43% with somatic antigen, indicating the superiority of E/S antigen. Percentage positivity declined after treatment of hookworm cases. No relationship was found between ELISA reactivity and severity of infection.

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