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Biomedical subjects

D A Denham

Publications and source records attributed to D A Denham.

At least 37 records · Page 2Linked to original sources
PubMed1989

Heat shock cognate 70 is a prominent immunogen in Brugian filariasis.

A cDNA expression library constructed from RNA derived from adult stage Brugia pahangi (mixed sexes) was screened with pooled sera from chronic, amicrofilaremic cases of human lymphatic filariasis from the Indonesian island of Tanjungpinang, where Brugia malayi is endemic. Polyclonal antisera raised to purified beta-galactosidase fusion proteins from two of the most highly reactive clones identified a protein of Mr 70,000 in all stages examined (microfilariae, L3 and adults) of both B. malayi and Brugia pahangi. Derivation of the amino acid sequence from these two overlapping cDNAs identified the encoded protein as a member of the heat shock protein 70 family, and showed the closest similarity to the constitutively expressed "heat shock cognate 70" (hsc70) protein. Hybridization of hsc70 cDNAs to RNA and DNA from B. pahangi under stringent conditions identified a major transcript of 2.4 kb and revealed the existence of a family of related genes. In vitro culture of larval stages of B. pahangi at elevated temperatures (43 degrees C) resulted in increased expression of hsc70, and a classic heat shock response in which five proteins (mr 18,500, 22,000, 62,000, 70,000, and 85,000) were exclusively synthesized in microfilariae. Analysis of cross-reactivities by Western blotting implied that antibody generated by infection with B. malayi was directed at filarial-specific determinants of Brugia hsc70. However, ELISA with recombinant fusion proteins for both Plasmodium falciparum and Schistosoma mansoni hsc70 indicated that some individuals with Brugian or Bancroftian filariasis did produce antibodies which cross-reacted with plasmodial and schistosomal homologs. Thus filarial-specific antibody responses were not generated in all individuals, indicating that this molecule would not be suitable for diagnostic purposes. ELISA with a purified beta-galactosidase fusion protein from B. pahangi showed antibody responses to hsc70 across the clinical spectrum of filariasis. Alignment of the derived amino acid sequences from B. pahangi, P. falciparum, S. mansoni and rat hsc70 homologs, and comparison of the immunologic reactivity of the products of the two cDNA clones by Western blotting and ELISA suggested that these determinants were located primarily at the C terminus of the protein.

Amino Acid Sequence↗
PubMed1989

Experimental Brugia pahangi and B. malayi infections of callitrichid primates.

The callitrichid primates, Callithrix jacchus jacchus (the marmoset) and Saguinus labiatus (the tamarin) were inoculated with infective larvae of Brugia malayi and B. pahangi. Microfilaraemia at low levels developed in 3 out of 4 C.j. jacchus infected with B. malayi and living or dead adult worms found in all 4. Only one of 4 C.j. jacchus became microfilaraemic (mf + ve) when given B. pahangi and adults were found in two. Of 4 S. labiatus given B. pahangi one became very lightly mf + ve and adults were found in 3. It is concluded that these animals are not suitable hosts for chemotherapeutic experiments.

Animals↗
PubMed1989

Microfilariae of Brugia pahangi in the blood of cats have variable levels of feline IgG on their sheaths.

Feline IgG was found on the sheath of microfilariae (mf) of Brugia pahangi isolated from the blood of cats. Gamma heavy chains, both light chains, and the Fc and F(ab')2 portions of IgG were present, suggesting that the molecule is intact. The amount of IgG on the sheath was variable and the younger the mf the less IgG was present on their sheaths. Possible functions of this adherent layer of host protein are considered.

Animals↗
PubMed1988

The effect of diethylcarbamazine on the in vitro serum-mediated adherence of feline granulocytes to microfilariae of Brugia pahangi.

The effect of the antifilarial drug diethylcarbamazine (DEC) on immunologically mediated destruction of the microfilariae (mf) of Brugia pahangi in vitro is addressed by studying the drug's influence on the granulocyte adherence to the surface of mf and the subsequent death of these parasites. DEC enhanced the adherence of cat blood-derived granulocytes to the surface of mf through the meditation of cuticle direct antibodies but not that mediated by complement alone; the parasites became immobilized and degenerated subsequent to cell adherence. The rate of cell adherence in the antibody-containing cultures was enhanced by DEC. As previously reported, this drug had no direct effect on the viability of the parasites. Preincubation of the cells in DEC had a greater effect on cell adherence than did preincubating the parasites in the drug, thus supporting the contention that this antifilarial compound may act on host components. Further investigation of this possibility may contribute significantly to a more complete understanding of why DEC can cause severe side reactions in filariae infected patients.

Animals↗
PubMed1988

The effect of sera from cats infected with Brugia pahangi and subsequently treated with levamisole on the infectivity of third-stage larvae of B. pahangi.

Cats were treated with levamisole and the infective (L3) stage of Brugia pahangi. Serum from infected cats was subsequently tested for its ability to infect jirds. Jirds autopsied at 33 days postmortem showed significant levels of parasitemia. This is contrary to reports of a previous study wherein serum from humans infected with B. malayi was found to induce cell adherence and death of the L3.

Animals↗
PubMed1987

The cat infected with Brugia pahangi as a model of human filariasis.

The responses of cats to Brugia pahangi, which parasitizes them in nature, mimic those of humans to Brugia malayi and Wuchereria bancrofti in many important respects. It is likely that many of the features of the relationship between host and parasite that can be studied in cats infected with B. pahangi also apply to humans, but for a variety of practical reasons cannot be demonstrated in humans. Both immunologically and parasitologically there is a profound difference between B. pahangi-infected cats that have microfilariae in their blood and those that either do not become microfilaraemic or clear their blood of microfilariae and become post-microfilaraemic. Microfilaraemic cats are susceptible to reinfection and fail to recognize the surface of the sheath of microfilariae. They also do not produce antibodies against several components recognized by post-microfilaraemic cats. Cats that have destroyed their microfilariae also destroy their adult worms and are very resistant to challenge with infective larvae. Apart from the unique ability to recognize the sheath of microfilariae in fluorescent antibody tests, sera from these cats react with microfilarial antigens at 61-81 kDa, antigens of infective larvae at 22 and 18.5 kDa and adult antigens at 34, 18, 16, 13 and 11.5 kDa. None of these antigens are recognized by microfilaraemic cats.

Animals↗
PubMed1987

Phosphorylcholine-bearing antigens in filarial nematode parasites: analysis of somatic extracts, in-vitro secretions and infection sera from Brugia malayi and B. pahangi.

A set of cross-reactive antigens is described which are present in somatic extracts and in-vitro secretions of the filarial nematodes Brugia pahangi and B. malayi. A monoclonal antibody reactive with a repeating epitope on these molecules readily detects circulating antigen in the serum of animals infected with lymphatic filariae, using either an immunoradiometric assay or enzyme-linked immunosorbent assay (ELISA). This epitope has the immunological reactivity and chemical characteristics of the phosphorylcholine (PC) hapten. The anti-PC monoclonal has been used to define the antigens bearing this epitope, and in chromatographic studies on material from extracts of Brugia adult worms, a heterogeneous profile of PC-positive molecules are found. In sera from Brugia-infected jirds, an antigen with a native molecular weight of approximately 500,000 is observed, which displays limited sensitivity to protease degradation. However, denatured samples on Western blots show a major parasite circulating antigen of Mr 90,000. The detection of this antigen in the presence of excess host antibody is also demonstrated, taking advantage of the stability of the target epitope to a range of treatments designed to dissociate and eliminate immune complexes.

Animals↗
PubMed1986

Expression of cross-reactive surface antigens by microfilariae and adult worms of Brugia pahangi during infections in cats.

Microfilariae of Brugia pahangi were labelled with 125-Iodine using the reagent IODOGEN. Electron microscope autoradiographs of sections of iodinated microfilariae showed that the label was strictly confined to their sheath. Adult worms were also iodinated by the same procedure. Sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) analysis of detergent extracts of radio-labelled parasites revealed components of molecular weights 113, 81-71, 46 and 33 kDa in microfilariae, and of molecular weights 29, 20 and 16 kDa in adult worms. All but the 33 kDa component of microfilariae were immunoprecipitable with sera of infected cats and therefore antigenic. Antibodies to the 81-71 kDa and the 46 kDa microfilarial antigens were detected by immunoprecipitation before patency. Similarly, the 29 kDa antigen of adult worms was immunoprecipitable before the fourth moult. Therefore, during infection in cats, these antigens cross-react with epitopes present on earlier developmental stages.

Animals↗
PubMed1986

Attempted vaccination of jirds (Meriones unguiculatus) against Brugia pahangi with radiation attenuated infective larvae.

Jirds were vaccinated by three to five subcutaneous (SC) injections of infective larvae of Brugia pahangi which had been irradiated at 25, 45 or 90 krads from a 60Co source. They were challenged either SC or intraperitoneally. Vaccination with four doses of 50 larvae irradiated with 25 krads produced 49.3% resistance to IP challenge worms and 39.8% against SC challenge worms. Five doses of larvae irradiated with 45 krads produced 62% resistance to SC challenge. Three doses of larvae irradiated with 90 krads produced 74.9% resistance to SC challenge and five doses produced 76.2% resistance. The reasons why irradiated larvae produce resistance whereas normal larvae do not are discussed.

Animals↗
PubMed1986

The ability of Aedes aegypti mosquitoes to survive and transmit infective larvae of Brugia pahangi over successive blood meals.

The mortality of Aedes aegypti mosquitoes increased; immediately following a blood meal containing microfilariae of Brugia pahangi, when infective larvae began to migrate out of the flight muscles and when infective larvae were lost from the mosquitoes during a blood meal. When infective mosquitoes took a second blood meal 86.2% of the infective larvae escaped from their bodies. However, only 50.3% escaped when mosquitoes fed through a thin layer of cotton. Infective larvae in the abdomen of the mosquitoes stood the least chance of escaping from the insects. When infective mosquitoes were offered a third blood meal four days later, the proportion of infective larvae in the head and labium had risen from 56.6% in the control group to 66.0% and 69.4% in the two test groups. At this third feed 54.7% and 75.7% of the infective larvae were lost from mosquitoes with a low and medium pre-feeding worm burden respectively. This suggests that the escape of infective larvae from mosquitoes with only a few worms is less efficient than from mosquitoes with a medium worm burden.

Aedes↗
PubMed1986

The antifilarial activity of a novel group of organic arsenicals upon Brugia pahangi.

Mel W is a second generation anionic organic arsenical which is filaricidal but has sporadic and unacceptable lethal side effects. Eight new cationic derivatives have now been synthesized in an attempt to avoid the side effects and have been examined for their effects upon adult Brugia pahangi in Meriones unguiculatus. They were all shown to be potent filaricides and the two best compounds, Mel Ga and Mel Cy, were at least 95% effective in killing adult B. pahangi at 5 X 3.13 mg/kg when injected subcutaneously.

Animals↗
PubMed1986

Brugia pahangi infections in cats: antibody responses which correlate with the change from the microfilaraemic to the amicrofilaraemic state.

The humoral responses of eight cats infected with Brugia pahangi to somatic antigens from all life-cycle stages were examined quantitatively by ELISA and qualitatively by immunoblotting for almost a year post infection. Six cats spontaneously became amicrofilaraemic: their production of IgG antibodies against somatic antigens of microfilariae, adults, and infective larvae was not statistically higher than that of the two cats which remained microfilaraemic. However, immunoblotting revealed that those cats which spontaneously became amicrofilaraemic selectively recognized certain microfilarial, adult and infective larval somatic antigens prior to disappearance of microfilariae from the peripheral circulation. The data suggest that selective recognition of antigens by some cats is responsible for the production of antibodies which may then promote microfilarial death.

Animals↗
PubMed1985

The effect of different types of skin surfaces on the transmission of Brugia pahangi infective larvae by the mosquito Aedes aegypti.

The transmission of Brugia pahangi from Aedes aegypti into Meriones unguiculatus was compared for four different skin surfaces (HAIRY, CLOTH, CLEAN, GREASY). Unshaven jirds reduced the feeding avidity of infective mosquitoes. The loss of larvae from infective mosquitoes was greatest when these insects fed on "exposed" skin surfaces. Significantly fewer infective larvae penetrated the host when infective mosquitoes fed on a jird through a thin layer of cloth.

Aedes↗
PubMed1985

Toxocara canis larvae in the brain of a British child.

The clinical and autopsy findings of a two and a half year-old infant with Toxocara sp. infection of the brain and granulomatous lesions in the liver are reported. The cause of death was non-accidental injury. The relationship between Toxocara infection and behavioural disorders is discussed.

Ascariasis↗
PubMed1985

Mononuclear and multinuclear macrophages in filarial infections.

Filarial infections commonly involve chronic tissue responses to these complex and resiliant organisms. These responses, which occur with a number of the parasitic stages of filariae, involve macrophages, and these cells appear to be important in immunologically induced destruction and removal of these important parasites of man and animals. Details of their presence and experimental induction as well as their distinction into a number of morphological types, including multinuclear (giant cell) forms, is described in this communication. The ability of these various forms to function in phagocytic and immunologically mediated adherence assays is also described.

Animals↗