Effect of combined praziquantel and recombinant glutathione S-transferase on resistance to reinfection in murine Schistosomiasis mansoni.

This study was undertaken to evaluate the effect of recombinant Schistosoma mansoni-26 Glutathione S-transferase (rSm 26 GST) or soluble egg antigen (SEA) alone and in addition to praziquantel (PZQ) on the state of resistance to S. mansoni reinfection. The associated changes in the immune responses were evaluated. The experimental group of mice were injected intravenously before S. mansoni infection (80 cercariae/mouse) either with rSm26 GST (1 microgx4) or SEA (10 microgx4) in addition to PZQ (2x500 mg/kg) administered 6 weeks post-infection. Seven control groups were used, three of them were the infected (80 cercariae/mouse), the challenged (240 cercariae/mouse) and the infected challenged controls (80+240 cercariae/mouse). The rest of the four groups were the treated controls receiving: the GST-Lyzate, rSmGST, SEA and PZQ in the same doses and at the same timings. Challenge infection was conducted for all the groups 8 weeks post-infection. Animals were sacrificed 3 weeks post-challenge. After sacrifice animals were perfused and percentage resistance to reinfection was calculated. Immune responses were assessed by the measurement of hepatic granuloma diameter, intralesional T-cell phenotypes and serum immunoglobulin isotypes. The highest percentage of resistance to reinfection was observed in rGST-treated group while the lowest percentage of resistance was detected in PZQ-treated group. Whereas in mice receiving combined rGST or SEA and PZQ, percentage resistance to reinfection was significantly higher than that in PZQ treated mice. The remarkable reduction in granuloma diameter in rGST-treated group with or without PZQ was associated with decrease in the intralesional L(3)T(4)(+) and increase in Lyt(2)(+) T-cell phenotypes. However, no special relationship was observed between the percentage of resistance and the changes in granuloma diameter or intralesional T-cell phenotypes. The increase in percentage resistance to reinfection was found accompanied by increased anti SWAP IgE. Combined rGST and PZQ provided the complementary goals of improved state of resistance to reinfection 'which was compromized after cure with PZQ' and the maximal reduction in granuloma diameter.

Effect of Schistosoma mansoni infection on offsprings born from infected mothers.

Offsprings C57BL/6 mice (4 weeks old) coming from either moderately infected (40 S. mansoni cercariae) or heavily infected (100 S. mansoni cerariae) mothers, were exposed to 40 S. mansoni cercariae each. Seven weeks post infection (P.I.), Offsprings were sacrificed. In both groups there was significant reduction in the worm load, both hepatic and intestinal tissue egg count. The oogram profile was not altered. Humoral immune response as regards the level of anti S. mansoni SEA Ab was elevated in both groups in comparison to their parallel controls at 2 weeks post delivery and 7 weeks P.I. The level of antibodies was significantly higher in heavily infected Offsprings than that present in offsprings coming from moderately infected mothers. Delayed footpad swelling and hepatic granuloma size were significantly reduced in both groups comparing with their corresponding controls.

Mutual effect of Schistosoma mansoni infection and pregnancy in experimental C57 BL/6 black mice.

Sixty female C57BL/6 mice were infected with 40 Schistosoma mansoni cercariae each. Seven weeks later, they were mated with normal syngeneic males. Uninfected mice (30) were bred in parallel, and both groups were bred several more times with daily records of pregnancy, delivery and number of offsprings. The number of pregnancy was 146, with 50 survived infants (34.2%) in contrast to 121 pregnancy with 93 survived infants (76.8%) in controls. The outcome of pregnancy was 13% abortion, 10.9% maternal death and 41.7% infanticide. The weight of offspring at 2 and 4 weeks of age was significantly less than in controls (P < 0.01). Again, C57BL/6 (40) female mice were mated, then infected with 100 S. mansoni cercariae each. The results showed that, pregnancy had no effect on bilharzial infection as the total worm burden and distribution, hepatic and intestinal tissue egg count and the oogram profile, were not significantly differ from that in the control group (20). Besides, the immediate footpad swelling was significantly higher but the delayed footpad swelling and the level of antibodies against S. mansoni soluble egg antigen were insignificantly differ from that present in the parallel control (infected but not pregnant). As regards histopathological parameters, although there was insignificant difference in the size of hepatic granuloma, yet there was more collagenous fibrous tissue deposition distributed in-between inflammatory cells specially at the periphery of the granuloma.

Use of Kato and nucleopore techniques for qualitative diagnosis of schistosomiasis.

A comparison on qualitative basis, is attempted between merthiolate-iodine-formaldehyde concentration (MIFC) and Kato thick smear techniques for diagnosis of schistosome eggs in stools. As well, the centrifugation-sedimentation method was compared with the Nucleopore filtration technique for schistosome eggs in urine. Using MIFC and Kato techniques, 149 out of 185 subjects were found to have Schistosoma mansoni infection, 41 of them were diagnosed by Kato alone, while no case was solely MIFC positive. The sensitivity of MIFC compared to kato was 72.3% and both techniques were 100% specific. For diagnosis of S. haematobium infection, 78 out of 103 subjects were positive by centrifugation- sedimentation and/or Nucleopore techniques. 42 of them were diagnosed by Nucleopore alone and none was positive by centrifugation- sedimentation only. The sensitivity of the latter technique was 46.2% and both techniques were 100% specific. The study demonstrates that Kato thick smear and Nucleopore filtration are highly sensitive techniques that can be used for routine qualitative diagnosis of schistosomiasis. Under field conditions, they are qualitatively and quantitatively useful. The Kato technique besides its high sensitivity is very cheap. The only limitation for the Nucleopore technique is its relative high expenses.

Effect of specific chemotherapy on the immune response and resistance to reinfection in experimental Schistosomiasis mansoni.

Mice infected for 45 days with 120 Schistosoma mansoni cercariae and treated with praziquantel in a dose of 500 mg/kg for two consecutive days had a significant lower resistance to reinfection when challenged two weeks after treatment (45% compared to 88% in infected challenged untreated mice). In praziquantel-treated mice, the reduction in the per cent resistance was accompanied by a diminution in the size of hepatic granulomata and its in vivo correlate the delayed foot pad swelling. Moreover, the granuloma proportionate T-cell subset enumeration revealed a significant reduction in the number of T-helper cells. The humoral immune response as measured by the immediate foot pad swelling was not affected by praziquantel. Results reveal besides the diminution of the state in resistance to reinfection after praziquantel, possible involvement of egg-related pathology as a T-cell mediated reaction and as a mechanical obstacle in maintenance of this resistance.

Levamisole restored the compromised state of immunity after specific chemotherapy in experimental schistosomiasis mansoni.

Mice infected for 45 days with 120 Schistosoma mansoni cercariae and treated with levamisole (25 mg/kg subcutaneously) have more efficient acquired immunity when challenged with 240 Schistosoma mansoni cercariae the same day of treatment (97.7% # 87.7% in infected challenged controls). In praziquantel-treated mice (500 mg/kg for 2 days orally), the reduction in the percent resistance (45.5%) was accompanied by a significant diminution in the size of granuloma, delayed foot pad swelling and granuloma proportionate T-helper cells number. Levamisole when given two weeks post praziquantel treatment and with the challenge infection increased the percent resistance to 79.2%. The increase in percent resistance recorded in mice receiving both praziquantel and levamisole was accompanied by restoration of granuloma size, delayed foot pad swelling and granuloma proportionate T-helper cells number to infected challenged untreated control values. Results reveal-beside efficacy of levamisole as immunoregulant in schistosome immunity--a possible role for the granuloma as a T-cell mediated response in maintenance of immunity.

Serological cross-reaction between rodent malaria parasites as determined by the indirect immunofluorescent technique.

In view of the morphological similarity between the blood stages of Plasmodium berghei berghei and P. b. yoelii on the one hand and P. vinckei and P. chabaudi on the other, these rodent malaria parasites were investigated by the indirect fluorescent antibody technique in the hope of thus differentiating between them.Sera were obtained from rats hyperimmunized against these four parasites, from rabbits immunized against the soluble antigens of the blood stages of the parasites, and from a rabbit immunized against the sporozoites of P. b. yoelii. The titre of each serum was determined by its reaction with the homologous and the heterologous antigens in a modified immunofluorescent technique.The results showed a definite cross-reaction between the four parasites, indicating a common antigen; no serological difference between P. b. berghei and P. b. yoelii (these being considered the berghei group or Group 1); no serological difference between P. vinckei and P. chabaudi (vinckei group or Group 2); and a definite serological difference between Group 1 and Group 2 infections.The theoretical antigenic structure of rodent plasmodia is discussed in the light of these findings.