Synergistic action of praziquantel and host specific immune response against Schistosoma mansoni at different phases of infection

The interaction between specific immune response to Schistosoma mansoni and praziquantel (PZQ) was studied in mice. In mice harboring concomitant immunity, 6-day-old parasites treated with PZQ were more effectively removed than 24 h treated parasites despite both had a significant worm burden reduction when compared with respective treated controls. These results show that PZQ can be effective at the skin and lung stages of parasite's development mainly acting with a established specific immune response, and particularly at the lung phase.

Antibody isotype responses to Schistosoma japonicum antigens in subjects from a schistosomiasis area with repeated praziquantel chemotherapy compared with a new endemic zone in Hunan Province, P.R. China

To demonstrate the dynamics of specific antibody isotypes against schistosome adult worm (AWA) and soluble egg (SEA) antigens, we evaluated (in 1999-2000) 112 subjects infected with Schistosoma japonicum from 2 regions of Hunan Province, China. Fifty-eight subjects were from Area A, a well-known endemic area with repeated chemotherapy. Area B (n = 54) is a new endemic focus in another part of the same province. Serum samples were collected prior to praziquantel (PZQ) chemotherapy, and at 2 and 12 months post-treatment. IgM, IgA, IgG, IgG2, IgG4 and IgE antibodies to AWA and SEA were measured by quantitative enzyme-linked immunosorbent assay (ELISA). Pre-treatment antibody isotype levels from Area A, except IgA against AWA and SEA, were significantly higher than those from Area B. In response to chemotherapy, most antibody isotype levels fell or remained stable. However, in Area A there was a significant increase in the IgA, IgE and IgG4 responses to AWA 2 months after PZQ--which fell to approach pre-treatment levels by 12 months. A similar response was seen in Area B with IgE and IgG4 to AWA. Levels of all AWA-specific IgE and IgG4 were significantly higher in subjects from Area A compared with Area B at all time-points. AWA-IgE levels demonstrated significant linear correlations with age and number of previous PZQ treatments in Area A only. All SEA-specific isotypes in both areas fell significantly in response to treatment--except IgE, which remained stable in both area. All SEA-specific isotype levels (except IgA) were significantly higher from Area A at baseline. This significant difference was maintained through 12-months follow-up for IgE, IgG2 and IgG4 only. This study suggests that multiple episodes of schistosome infection may be required to generate antibody isotype levels that have been associated with resistance to re-infection in other studies. Further, a surrogate marker of successful chemotherapy (AWA-IgG4) performed less effectively in patients with previous treatment courses.

The effect of praziquantel administration on the course of hepatitis B among cases with concomitant schistosome infection

The present work was designed to study the course of HB virus infection among bilharzial and non-bilharzial patients and to assess the therapeutic effect of praziquantel administration on subsequent course of HB among individuals with concomitant infections. This study included 26 bilharzial cases, 14 cases with HB and 40 cases with both infections (HB and schistosomiasis). Praziquantel was administered to all bilharzial positive cases. Sera were collected from all groups prior to anti-bilharzial chemotherapy, and then later at three and six months post treatment. The results show improvement of both liver function tests and cell mediated immunity as estimated by increased mean value of CD3, CD4, helper/suppressor ratio among individuals who received praziquantel in the two groups with schistosomiasis and concomitant infection. Furthermore the individuals who lost their HB surface antigenaemia were found to have a higher mean pan T cells, CD4 values, normal helper/suppressor ratio and absence of Clc in their sera than those who retained their carrier state. The follow up of HB carriers demonstrated a higher cure rate (clearance of HBsAg) among the group with concomitant infection as compared to the group with virus hepatitis only. HBV type two infection was common among the study population accounting for 25.9% of HBsAg positive cases. 42.9% of them cleared their antigenemia after treatment with praziquantel.