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Biomedical subjects

G F Mitchell

Publications and source records attributed to G F Mitchell.

At least 163 records · Page 9Linked to original sources
PubMed1982

Proteolytic cleavage of immunoglobulin by enzymes released by Fasciola hepatica.

Immature Fasciola hepatica release a papain or cathepsin B-like proteolytic enzyme which cleaves immunoglobulins (Ig) of mouse, rat, rabbit and sheep in vitro. Mouse IgG and IgM molecules are both susceptible to cleavage as is hemoglobin. Whether single or multiple proteases are responsible for Ig cleavage is unknown. The proteolytic activity of secreted enzyme(s) is optimal at pH 3.5-4.5, but activity is also present at pH 7. Proteolysis is enhanced in the presence of 5 mM dithiothreitol or 100 mM cysteine. Based on studies with protease inhibitors, the F. hepatica enzyme activity has been identified as a thiol protease. It is destroyed by heating at 56 degrees C for 1 h, but retains activity after storage at -20 degrees C for 7 days. Whether inhibition of the proteolytic activity increases the susceptibility of F. hepatica immature worm to any extant immune effector mechanisms in hosts remains to be determined.

Animals↗
PubMed1982

Surface membrane proteins and glycoproteins of red blood cells from normal and anaemic mice.

1. The surface membrane proteins of red blood cells from normal, hyperbled or acetylphenylhydrazine-treated BALB/c mice and NZB mice of different ages were labelled by lactoperoxidase-catalyzed radioiodination. Sialoglyoproteins were labelled by periodate/NaB3H4 or galactose oxidase +/- neuraminidase/Na3H4 treatments. 2. Anaemia produced several changes in radioiodinated proteins. 3. Sialoglycoprotein radiolabelling was unchanged, even with over 90% reticulocytosis. 4. Decreased periodate/NaB3H4-dependent labelling of red blood cells from Plasmodium berghei-infected BALB/c mice (Howard et al., 1980; Howard & Day, 1981) cannot therefore be due to anaemia per se, but must be related more specifically with infection.

Aging↗
PubMed1982

Strongyloides ratti infections in congenitally hypothymic (nude) mice.

The course of infection with Strongyloides ratti was examined in congenitally hypothymic CBA/H, C57Bl/6 and BALB/c nude mice. The intensity of infection and the duration of faecal larval excretion were both increased in nude mice when compared with intact mice. Adult worms persisted in the small intestine of nude mice for at least 6 weeks. Greater worm burdens were found in such mice after subcutaneous injection as compared with percutaneous infection. Hypothymic mice did not acquire resistance to re-infection. It is concluded that both the spontaneous expulsion of worms in primary infection and resistance to challenge infection are T cell-dependent events. Autoinfection was not seen.

Animals↗
PubMed1982

Lung granulomatous hypersensitivity to eggs of Schistosoma japonicum in mice analysed by a radioisotopic assay and effects of hybridoma (idiotype) sensitization.

The radioisotopic assay for acute granulomatous hypersensitivity (AGH) to eggs of Schistosoma japonicum in mice sensitized with eggs in adjuvant has been examined in the high responder strain. C57BL/6. Responsiveness is expressed as the lung-kidney ratio of radioactivity in mice challenged intravenously with eggs and injected with 125I-iododeoxyuridine. Eggs vary in their AGH sensitizing and eliciting potency; eggs proven to be superior in the circumoval precipitation (COP) test for detection of human serum anti-S. japonicum antibodies are superior in the C57BL/6 AGH assay. CBA/H are non responders and BALB/c are low to intermediate responders and are thus different from C57BL/6 mice. Short-term infected CBA/H mice are low COP antibody responders relative to infected C57BL/6 and titres of IgM anti-egg antibodies are low in the CBA/H strain as determined in a solid-phase radioimmunoassay (RIA). Following egg sensitization, CBA/H mice are also lower responders than C57BL/6 mice in terms of antibodies with the specificity of a COP-positive IgM hybridoma-derived antibody, P.41, measured in a competitive RIA. No evidence has been obtained that alteration of the response to the target epitope of P.41 alters the responsiveness of C57BL/6 mice to S. japonicum eggs. Thus, large amounts of injected P.41 antibody do not alter lung AGH and induced anti-idiotype responses to the P.41 protein do not influence AGH in egg-sensitized C57BL/6 mice. However, immunization of C57BL/6 mice with another IgM anti-schistosome hybridoma antibody, 1.39, results in partial inhibition of lung AGH responsiveness. The nature of the effect of 1.39 immunization on AGH to eggs remains unknown, but further analysis of the phenomenon may lead to novel approaches to the control of granulomatous inflammatory disease in high responders.

Animals↗
PubMed1982

Giardiasis in mice: analysis of humoral and cellular immune responses to Giardia muris.

Humoral and cellular immune responses have been evaluated in two inbred strains of mice which differ markedly in their susceptibility to infection with Giardia muris. Serum IgG and IgA antibody levels and IgA levels in intestinal washes were determined by a solid-phase radioimmunoassay using G. muris antigen prepared by sonication of trophozoites, while cell-mediated immunity was assessed by a radiometric ear-assay for delayed-type hypersensitivity. Following infection of BALB/c mice (resistant) and C3H/He mice (susceptible), the IgG and IgA antibody levels in serum progressively increased over the period of study with C3H/He mice having significantly higher titres of IgA antibodies than BALB/c late in the infection. Systemic immunization with G. muris trophozoites resulted in high titres of IgG antibodies in the serum. IgA antibodies were detected in intestinal washes 2 weeks after infection with a subsequent fall in levels in BALB/c mice but a progressive increase levels in C3H/He mice. Prior immunization resulted in IgA antibodies being detected earlier in the intestinal washings after a challenge infection. Delayed-type hypersensitivity to G. muris antigens could not be detected during an infection but a positive response was elicited following antigen priming in mice pretreated with cyclophosphamide. The immune responses evaluated in this study were assessed using a whole G. muris trophozoite sonicate and variations in the quantitative aspects of the responses did not account for observed differences in the course of infection in the two strains of mice.

Animals↗
PubMed1982

Variable and common antigens of Babesia bovis parasites differing in strain and virulence.

Virulent and avirulent K strain (KV and KA) and virulent L strain (LV) Babesia bovis parasites were biosynthetically labeled with 35S-methionine. Labeled proteins, extracted in detergent from infected cultures, were analyzed by two-dimensional gel electrophoresis. Protein antigens common to these forms of babesia and those specific for strain and correlating with the degree of virulence were identified by immunoprecipitation with antisera. Dominant labeled protein antigens were found to differ both between the K and L strains of B. bovis and between virulent (KV) and avirulent (KA) forms of the K strain. Partial cleavage of biosynthetically labeled proteins by staphylococcal V-8 protease and peptide mapping revealed that no extensive amino acid homology existed between the candidate variant antigens. KA B. bovis parasites are currently in use as a live attenuated vaccine for bovine babesiosis in Australia. Antigens that are better expressed in KA relative to virulent strains may therefore be markers of avirulence and/or candidate "host-protective antigens" of B. bovis. At least one protein (Mr 43,000) was identified as being a dominant labeled antigen of KA that is poorly represented in the KV and LV B. bovis isolates.

Antigens↗
PubMed1981

Immunisation of mice against Taenia taeniaeformis using antigens prepared from T. pisiformis and T. hydatigena eggs or oncospheres.

Experiments were carried out to investigation the degree of immunity stimulated against Taenia taeniaeformis infection in mice by prior administration of eggs or ultrasonically disrupted oncospheres of T. pisiformis or T. hydatigena. Sonicated oncospheral antigens were given either orally or by subcutaneous injection in Freund's complete adjuvant, and eggs were given orally. Three inbred strains of mice with varying degrees of innate resistance to initial infection with T. taeniaeformis were used in the experiments. These were the moderately resistant BALB/c, moderately susceptible CBA/H, and highly susceptible C3H/He strains. It was found that BALB/c mice developed high levels of immunity when immunised with either T. pisiformis or T. hydatigena eggs, or with sonicated oncospheres administered orally or parenterally. CBA/H mice developed moderate immunity, and C3H/He mice generally did not develop a satisfactory level of resistance. the implication of these findings with respect to immunisation of outbred animals against natural infection with larval cestodes using antigen prepared from the oncospheres of heterologous parasite species is discussed.

Animals↗
PubMed1981

Murine hybridoma-derived antibodies in the processing of antigens for the immunodiagnosis of hydatid (Echinococcus granulosus) infection in sheep.

Mice experimentally infected with hydatid parasite Echinococcus granulosus (secondary echinococcosis), were used as spleen cell donors for hybridoma production. Two hybridomas were produced which secreted antibody with anti-E. granulosus cyst fluid (EgCF) activity. Radioimmunoassays comparing the binding of these hybridoma-derived antibodies to E. granulosus versus several other antigen preparations from sheep parasites showed that the antibodies had a high degree of specificity for the hydatid parasite. However, using a panel of clinically defined sheep sera in a competitive radio-immunoassay, the binding of the hybridoma-derived antibodies to EgCF was inhibited strongly by sera from sheep infected with the common parasites Fasciola hepatica and Taenia hydatigena. When the hybridoma-derived antibodies were conjugated to CNBr-activated Sepharose and the crude EgCF applied to the affinity column, the "run through' antigen preparation showed a significant increase in specificity for experimental E. granulosus infection. A useful means of applying the hybridoma technology in the development of new immunodiagnostic reagents may be to select those murine hybridomas which produce high-affinity, cross-reacting antibodies and to use these antibodies in the processing of homologous antigen by affinity chromatography.

Animals↗
PubMed1981

Studies on malaria in Papua New Guinea: comparison of the surface glycoproteins on red blood cells from infected and uninfected individuals.

The levels of erythrocyte membrane sialic acid from 17 patients with Plasmodium falciparum malaria and 1 with Plasmodium vivax malaria, in Papua New Guinea, have been compared with 9 uninfected controls. The amounts of radioactivity incorporated into the major erythrocyte glycoproteins by the periodate/NaB3H4 or galactose oxidase plus neuraminidase/NaB3H4 methods were unchanged by malaria infection. The electrophoretic mobilities of these proteins also were unaffected. Several new glycoprotein bands with molecular weights (mol. wt) of 160,000, 89,000, 46,000, 42,000 and 33,000 Daltons were labelled on the surface of erythrocytes from infected individuals; however, none of these bands appeared in all malarious samples. Sialic acid levels on the erythrocyte membrane were also measured by exhaustive neuraminidase treatment and quantitative assay of released sialic acid. The amount of sialic acid was raised in 1 infected individual, within the normal range for Europeans in 4 others, and below this range with 3 patients. Apparently, extensive removal or modification of sialic acid on the surface of uninfected erythrocytes does not occur in human malaria, in contrast to the results obtained in earlier studies with the lethal murine malarias.

Adolescent↗
PubMed1981

Murine hybridoma-derived antibodies producing circumoval precipitation (COP) reactions with eggs of Schistosoma japonicum.

Of 7 hybridomas which secrete immunoglobulins binding to crude extracts of Schistosoma japonicum adult worms and/or eggs in solid-phase radioimmunoassays (RIAs), 3 gave positive precipitation reactions in the circumoval precipitin test (COPT). The COPT is a simple and inexpensive immunodiagnostic test for schistosomiasis japonica which involves the incubation of a selected batch of S. japonicum eggs with sera from patients and examination for precipitates one or more days later. Using a competitive RIA with an egg antigen extract and a labelled COPT-positive hybridoma ascites fluid, PwF.41-1-3, the surprising observation was made that only one anti-egg antibody specificity appeared to be represented in the series of 3 antibodies (as ascites fluids). Using sera as inhibitors in the competitive RIA, inhibitory activity (presumably antibodies to the target antigenic determinant of PwF.41-1-3) was readily detected in sera from egg-immunized mice and was of relatively high titre in a strain of mouse (C57BL/6) which can be readily sensitized for large granuloma formation around entrapped eggs in the lungs. Negligible inhibitory activity was found in the sera from S. japonicum-infected patients, even with sera from patients with prominent hepatosplenomegaly. The availability of COPT-positive hybridoma antibodies should facilitate isolation of at least one S. japonicum egg antigen involved in COP reactions and perhaps induction of immunopathological immune responses at least in mice.

Animals↗
PubMed1981

Resistance to cutaneous leishmaniasis in genetically susceptible BALB/c mice.

When injected cutaneously with promastigotes of an isolate of Leishmania tropica, BALB/c mice develop progressive cutaneous disease whereas lesions in BALB/c.H-2k mice heal after several weeks. Lesions in BALB/c mice injected into deep subcutaneous tissues with promastigotes are less obvious early but much more prominent later than in mice after strict intradermal injection. BALB/c mice injected with Corynebacterium parvum together with a preparation of frozen and thawed infected macrophages are more resistant to cutaneous disease than mice injected with either adjuvant or crude antigen mixture alone. Results of these experiments, and those on other mouse strains reported previously, will aid in the choice of mouse and injection regime to be used in testing the efficacy of isolated L. tropica antigens as vaccines.

Animals↗