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M J Doenhoff

Publications and source records attributed to M J Doenhoff.

At least 55 records · Page 3Linked to original sources
PubMed1996

Sm480: a high molecular weight Schistosoma mansoni antigen associated with protective immunity.

Rabbit antisera were raised against an antigen present in Schistosoma mansoni adult worms and eggs, and were shown to yield a single immunoprecipitin arc in immunoelectrophoresis and immunodiffusion against S. mansoni egg and worm antigen extracts. The antisera conferred partial but significant protection (22-30%) against a S. mansoni challenge when transferred to mice five and six days after the mice had been infected percutaneously with 200 cercariae. The egg and the worm forms of the antigen were immunologically cross-reactive, but the egg antigen possessed peptidolytic activity that could be inhibited with serine protease inhibitors. In indirect immunofluorescence the rabbit antisera reacted with surfaces of cercariae, five-day old lung-stage schistosomula, miracidia and praziquantel-treated adult worms. Gel-filtration chromatography demonstrated a relative molecular size of approximately 480 kDa for both the egg and worm forms of the antigen, and lectin-affinity chromatography indicated both were glycosylated. The serine protease activity and large relative molecular size of egg Sm480 were confirmed by a combination of radiolabelling with tritiated di-isopropyl fluorophosphate, immunoelectrophoresis and polyacrylamide gel electrophoresis.

Animals↗
PubMed1996

Enhancement of Schistosoma mansoni infectivity by intradermal injections of larval extracts: a putative role for larval proteases.

Extracts of Schistosoma mansoni cercariae caused increased vascular permeability and edema if administered to CBA/Ca mice by intradermal injection. Percutaneous infection with cercariae over the skin site at which cercarial homogenate (CH) had been injected intradermally resulted in a significant increase in the infectivity of S. mansoni compared with that shown by worm recovery from control animals (P < .05). This effect was abrogated by inhibition of protease activity prior to injection. Injection of inflammatory mediators (bradykinin or zymosan-activated plasma) with or without prostaglandin E2 produced a similar amount of edema as did CH. Injection of these mediators did not, however, enhance infectivity of cercariae. Pancreatic elastase was found to induce edema and enhancement of infectivity comparable to those induced by CH. The protease(s) introduced into the site of infection may have facilitated larval migration directly by hydrolyzing host tissue or indirectly by inducing an inflammatory response (or both).

Animals↗
PubMed1995

Efficacy of treatment of murine Schistosoma mansoni infections with praziquantel and oxamniquine correlates with infection intensity: role of host antibody.

The reduction in worm burden obtained by treatment of Schistosoma mansoni with praziquantel and oxamniquine was greater in mice with heavy infections than in relatively lightly infected animals. The reduction in worm burden achieved by each drug correlated with the size of the pre-treatment worm burden (r2 = 0.82 and 0.81 for praziquantel and oxamniquine, respectively). Intensity of infection did not affect the degree of tegumental damage and drug-induced antigen exposure on worms recovered soon after treatment with praziquantel. However, praziquantel-treated worms from mice with heavy infections had significantly more murine antibody attached to the treated-worm surface than worms from praziquantel-treated lightly infected mice. Heavily infected mice had greater levels of circulating anti-worm antibodies than lighter infected mice. The correlation between infection intensity and cure rates achieved by praziquantel and oxamniquine may thus be a reflection of the higher titres of relevant antibody in heavily infected mice mediating death of drug-treated worms.

Animals↗
PubMed1995

Active immunization of mice with Schistosoma mansoni worm membrane antigens enhances efficacy of praziquantel.

The efficacy of praziquantel treatment was significantly enhanced (P < 0.01) in CBA/Ca mice that had been immunized prior to Schistosoma mansoni infection with a crude extract of worm membrane antigens. In Western immunoblots sera from the worm antigen-immunized animals had a polyspecific antibody response, with a 25-27 kDa antigen being reacted against with particular intensity. A molecule of similar size was also recognized by rabbit antisera raised against an antigen with esterase activity that has been previously identified as a sensitive target for drug-antibody synergy. The increase in efficacy of subcurative doses of praziquantel in immunized animals is attributed to drug-induced tegumental damage causing antigens to become exposed on the worm surface. Thus, specific antigens, including the 25-27 kDa antigen, become accessible to circulating schistosomicidal antibodies. The role of antibodies that can synergize with praziquantel to kill schistosome worms is discussed.

Animals↗
PubMed1995

Short report: diminished susceptibility to praziquantel in a Senegal isolate of Schistosoma mansoni.

There is a recent report of low efficacy of praziquantel (PZQ) treatment of human schistosomiasis in a new Schistosoma mansoni focus in northern Senegal. Biomphalaria pfeifferi snails with patent infections were collected from the area of the focus and transported to the United Kingdom. Groups of mice were infected with cercariae from this Senegalese isolate, or with laboratory-maintained Kenyan or Puerto Rican isolates. In two separate experiments, PZQ was less effective against the parasite from Senegal than against the two other geographic isolates. The reduced susceptibility of S. mansoni to PZQ in infected human populations has important implications for current schistosomiasis control programs.

Animals↗
PubMed1994

Schistosoma mansoni host-parasite relationship: interaction of contrapsin with adult worms.

Contrapsin, a serine protease inhibitor (serpin) present in mouse serum, was compared with that found in adult Schistosoma mansoni worm homogenates, which although immunologically identical to contrapsin in mouse serum, had a higher molecular weight in Western blotting. Immunolocalization studies demonstrated parasite-associated contrapsin on the surface and interstitial cells of adult male worms. After extraction of these parasites with Triton X-114, contrapsin was found in the aqueous phase of the detergent, suggesting it is unlikely to be an integral membrane protein. Treatment of adult worms with deoxycholate resulted in a change in the electrophoretic behaviour of worm-derived contrapsin. Parallel studies with trypsin suggested this was due to interaction of the serpin with a protease. Using porcine pancreatic trypsin as a model for a putative schistosome protease reacting with contrapsin, we have shown that trypsin, following complex formation with contrapsin, loses immunogenicity. Thus, when contrapsin-trypsin complexes were used as immunogen, the resulting antisera contained antibodies to contrapsin and contrapsin-trypsin complexes only, and none to native trypsin. Thus, epitopes characterizing native trypsin were presumably either masked following complex formation with contrapsin, or their processing and presentation to antigen presenting cells was suppressed, so that an antibody response was not mounted against them. These observations encourage speculation that S. mansoni may be elaborating an immune evasion strategy whereby immunologically sensitive proteases are first complexed with host serpins, which would render them immunogenically inert, and then cleared from the circulation by the host's reticulo-endothelial system. In this way the immune system would be unable to 'see' sensitive parasite proteases sufficiently to mount a response against the parasite.

Animals↗
PubMed1994

Praziquantel-induced exposure of Schistosoma mansoni alkaline phosphatase: drug-antibody synergy which acts preferentially against female worms.

The efficacy of praziquantel-treatment of murine Schistosoma mansoni-infections can be enhanced by concurrent administration of rabbit anti-sera with specificity for parasite antigens. Monospecific rabbit serum raised against S. mansoni worm alkaline phosphatase, that was reactive with the enzyme on the drug-treated female surface, was found to significantly and preferentially increase the mortality of female worms by PZQ. Immunoglobulins purified from the anti-alkaline phosphatase antiserum inhibited 54% of schistosome alkaline phosphatase enzymatic activity on the surface of praziquantel-treated worms. We propose that synergistic antibody-mediated death of drug-damaged worms is a consequence of the inhibition of drug-exposed alkaline phosphatase on the female worm surface by passively transferred antibody.

Alkaline Phosphatase↗
PubMed1994

Drug-resistant schistosomiasis: resistance to praziquantel and oxamniquine induced in Schistosoma mansoni in mice is drug specific.

Schistosoma mansoni infections in mice were treated with subcurative multiple doses of either praziquantel (PZQ) or oxamniquine (OX). With an early exception, the drug treatments commenced when the worms were adult, but before the infections had become fully patent, and the eggs subsequently produced by worms that had survived the drug treatments were used to infect snails. Six or seven drug-treated passages of S. mansoni in mice were completed for each of the drugs, with the amount of drug administered to the infected mice generally being increased with each passage. Eighty percent of the worms of the sixth passage selected for PZQ resistance survived three doses of 300 mg/kg of PZQ given between days 28 and 37 after infection, and 93% of those of the seventh passage survived the same drug dose. In contrast, only 13% of worms of the sixth PZQ-selected passage survived three doses of 200mg/kg of OX given during the same period after infection. Only 11% or fewer worms derived from S. mansoni infections that had not been subjected to any drug pressure survived the 3 x 300 mg/kg PZQ treatments. Worms selected for OX resistance over six passages were completely resistant to three doses of 200 mg/kg, but only 26% survived three doses of 300 mg/kg of PZQ. Therefore, the results indicate that S. mansoni subjected to drug pressure may develop resistance to schistosomicidal drugs over the course of relatively few passages, but that cross-resistance between PZQ and OX does not occur. This is the first demonstration of drug resistance to PZQ, the current drug of choice for human schistosomiasis.

Animals↗
PubMed1993

Mechanisms of the inflammatory response induced by extracts of Schistosoma mansoni larvae in guinea pig skin.

Penetration of skin by cercariae of Schistosoma mansoni is associated with a local inflammatory response characterised by leukocyte accumulation and tissue swelling. The significance of the inflammation and its relevance to infection of the host is unknown. In this study, we have investigated the mechanisms of the local inflammatory response induced by injecting extracts of Schistosoma mansoni cercariae into guinea pig skin. Intradermal injection of cercarial homogenate or cercarial transformation fluid induced a dose-dependent increase in local edema formation and accumulation of intravenously injected 111In-labeled eosinophils and neutrophils. The responses were rapid in onset and independent of new protein synthesis. The capacity of extracts to induce edema formation and leukocyte accumulation correlated significantly with their proteolytic activity. In addition, extract-induced inflammation was reduced by co-injection with Trasylol, soybean trypsin inhibitor, PMSF, or heparin. A combination of PMSF and heparin virtually abolished extract-induced inflammation. The known inhibitory effect of Trasylol on kallikrein prompted an investigation into the role of kinins in inducing local edema formation. The bradykinin antagonist HOE 140 substantially reduced extract-induced edema whereas bradykinin itself was weak at inducing leukocyte accumulation. The cyclooxygenase inhibitor ibuprofen, the platelet-activating factor antagonist WEB 2086, and the 5-lipoxygenase inhibitor PF5901 had no effect on edema formation. In contrast, extract-induced eosinophil accumulation was reduced by WEB 2086 and PF5901, suggesting that endogenous PAF and leukotriene B4 were involved in recruiting these cells to inflammatory sites. Thus, cercarial proteases induce a local inflammatory response in guinea pig skin that can be attributed, in part, to known mediators of inflammation. It remains to be established whether the response is protective for the host or whether it is beneficial for the parasite. Further understanding of the underlying mechanisms may provide a target for the pharmacologic control of infection in schistosomiasis.

Animals↗
PubMed1993

Promutagenic methylation damage in liver DNA of mice infected with Schistosoma mansoni.

Male and female BK-TO mice were infected with different numbers of Schistosoma mansoni cercariae under standard environmental conditions. Promutagenic methylation damage (O6-methyldeoxyguanosine; O6-MedG) was detected in liver DNA, but not in kidney, spleen or bladder DNA of infected animals. It was shown that levels of hepatic O6-MedG increased with increasing intensities of schistosomal infection. Possible mechanisms of action are discussed. These include the activating effects of schistosomes and their products on murine macrophages and subsequent endogenous formation of N-nitroso compounds by the activated macrophages.

Animals↗
PubMed1993

Schistosoma mansoni egg attachment to cultured human umbilical vein endothelial cells: an in vitro model of an early step of parasite egg excretion.

To model the attachment of Schistosoma mansoni eggs to the endothelium of the mesenteric vasculature, the interaction between S. mansoni eggs and cultured human umbilical vein endothelial cells (HUVEC) in vitro was investigated. S. mansoni eggs rapidly attached to monolayers of both HUVEC and bovine aortic endothelial cells but more slowly to monolayers of cultured fibroblasts and smooth muscle cells. While both native and glutaraldehyde-fixed eggs attached equally well to HUVEC, eggs attached only to live, metabolically active HUVEC. Attachment was enhanced by both serum and plasma factors. In addition, platelet release products increased egg attachment by 75%. Preincubation of S. mansoni eggs with soluble egg antigens promoted attachment; in contrast, preincubation of HUVEC with the antigens inhibited attachment. These results suggest that interaction of S. mansoni eggs with HUVEC is an active process that can be modulated by molecules secreted by the egg and by platelets during egg extravasation.

Animals↗
PubMed1993

Comparison of the hepatoprotective effects of immune cells and serum in Schistosoma mansoni-infected immunosuppressed mice.

Immunosuppressed mice with heavy Schistosoma mansoni infections suffer from a severe hepatotoxicity reaction soon after the onset of infection patency, and this may be directly consequent upon the failure of the hosts to mount adequate granulomatous responses to embolized parasite eggs. Immune serum or immune peripheral lymphocytes from normal S. mansoni-infected immunologically intact donor mice were transferred to homologously-infected syngeneic T-cell deprived recipients to test the respective capacities of the transferred humoral or cellular immune effector elements to prevent hepatocellular damage and to reconstitute granuloma formation. Transferred immune serum was very effective in preventing liver cell damage, but did not significantly reconstitute the capacity to form granulomas in the recipients. In contrast, mice receiving immune spleen and mesenteric lymph node cells had their capacity to form granulomas around liver-bound eggs reconstituted, but lymphoid cell transfer was less effective in protecting against hepatocyte damage than serum transfer. Protection of host tissues may therefore not be the main role of the T-cell mediated S. mansoni egg granuloma.

Animals↗
PubMed1993

Immune attrition of adult schistosomes.

Mouse infection models are described that demonstrate reduction in the rate of egg production in Schistosoma haematobium worms 6-10 weeks after the onset of oviposition and loss of Schistosoma bovis worms around 10 weeks after infection. Neither phenomenon has been shown in Schistosoma mansoni- or Schistosoma japonicum-infected mice. The immunological basis for these anti-adult responses was inferred by comparison with infections in T-cell deprived mice and by transference of the ability to reduce a S. bovis worm burden in immuno-compromised hosts with immune serum. Vaccination with irradiation-attenuated parasites of S. haematobium was also shown to have consequences for the adults of challenge infections of either S. haematobium or of S. bovis, but not of S. mansoni. Thus, prior vaccination resulted in an abrogation of the reduced egg production by S. haematobium and S. bovis worms and also of the adult worm elimination that occurred in non-vaccinated S. bovis-infected mice. These models are being used to define the targets and mechanisms involved in the attrition of adult worms of schistosomes with terminal spined eggs.

Animals↗
PubMed1992

Schistosoma mansoni: control of hepatotoxicity and egg excretion by immune serum in infected immunosuppressed mice is schistosome species-specific, but not S. mansoni strain-specific.

Immunosuppressed mice infected with Schistosoma mansoni suffer from an acute hepatotoxicity reaction, and they fail to excrete as many parasite eggs as comparably infected immunologically intact control animals. The hepatotoxicity was shown here to be preventable, and egg excretion rates were enhanced, by transfer of serum from donors with chronic S. mansoni infections, but not by serum from donors with heterologous infections of Schistosoma haematobium, Schistosoma bovis, or Schistosoma japonicum. The effects of the transferred sera are considered to be due to specific antibody, but the possibility of cytokine involvement is discussed. A high degree of serological cross-reactivity was found between sera from mice infected with the different schistosome species and unfractionated egg homogenate (SEA) in ELISA. Cross-reactivity of the heterologous sera was, however, reduced against CEF6, a partially purified fraction of S. mansoni eggs that contains the putative hepatotoxin and has serodiagnostic potential. S. mansoni isolates from Puerto Rico, Brazil, Egypt, and Kenya shared similar characteristics with respect to the immune dependence of egg excretion and hepatotoxicity in immunosuppressed mice. The S. mansoni geographic isolates were also indistinguishable serologically, in terms of both the capacity of respective infection sera to neutralize hepatotoxicity and in their capacity to promote egg excretion of the other isolates in vivo. Complete immunological cross-reactivity of the geographically distinct isolates was also observed in ELISA with both CEF6 and SEA. Utilization of CEF6 for serodiagnosis of schistosomiasis mansoni is therefore unlikely to be restricted by geographical considerations.

Animals↗
PubMed1992

A stage-specific calcium-binding protein expressed in eggs of Schistosoma mansoni.

A cDNA sequence encoding a Schistosoma mansoni egg antigen SmE16 was cloned in Escherichia coli. The 16-kDa polypeptide deduced from the nucleotide sequence is related to the calmodulin and troponin C gene families of calcium-binding proteins, and the most significant homology is displayed around the four calcium-binding sites. The antigen was expressed as a hybrid protein of the bacteriophage MS2 polymerase. The MS2-SmE16 fusion protein binds calcium, as demonstrated via ligand blotting with 45Calcium. The detection of antibodies to the purified recombinant egg antigen in sera of schistosomiasis patients opens up the possibility that it may be a useful candidate for the development of serodiagnostic assays. The function of the protein in the egg is presently unclear.

Amino Acid Sequence↗