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K G Powers

Publications and source records attributed to K G Powers.

At least 19 recordsLinked to original sources
PubMed1985

Quantitative and qualitative changes in the humoral response of dogs through the course of infection with Dirofilaria immitis.

The present study compared the humoral response of dogs which developed microfilaremic or occult forms of dirofilariasis following experimental infection with Dirofilaria immitis L3 larvae. Quantitative analysis by ELISA revealed that antibody levels to adult somatic (AS), excretory-secretory (ES), and microfilarial (MF) antigens were highest during the patent phase of infection in dogs with either form of dirofilariasis. Patent sera from dogs destined for occult infections contained anti-AS and anti-MF antibody concentrations of 1,572 and 1,004 micrograms/ml, respectively, while microfilaremic-bound dogs contained 1,044 and 906 micrograms/ml, respectively. Chronic sera (430 days post infection) from occult dogs contained anti-AS and anti-MF antibody levels of 982 and 600 micrograms/ml, respectively, which were higher than in microfilaremic dogs. The antibody response to ES antigen was generally 10-fold less in absolute antibody concentrations at all time points tested. Immunoperoxidase staining of antigens transferred to nitrocellulose revealed the presence of several antigenic proteins which were recognized by occult, and to a lesser extent or not at all, by microfilaremic dogs. Sera drawn from occult-bound dogs 280 days post-infection, a time corresponding to microfilarial clearance (transition phase), contained higher antibody activity to microfilarial proteins weighing 47.5, 42.0, 34.2, and 22.4 kilodaltons compared to the microfilaremic dogs. This difference in antigen recognition became more apparent during the chronic phase of infection.

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PubMed1985

Monoclonal antibodies to parasite antigens found in the serum of Dirofilaria immitis-infected dogs.

We recently reported that parasite antigens are detectable in the serum of Dirofilaria immitis-infected dogs by counterimmunoelectrophoresis (CIE). Hybridoma cell lines that produce monoclonal antibodies specific for these antigens were obtained by immunizing mice with a partially purified antigen preparation, fusing spleen cells with SP-2 myeloma cells, and screening cell culture supernatants for antibody by ELISA and CIE inhibition. Antibodies specific for two epitopes shared by the two major circulating parasite antigens were identified. Immunoperoxidase studies showed that the epitopes recognized by the monoclonals were widely distributed in D. immitis, but the female uterus and eggs were particularly strongly labeled. A monoclonal antibody-based ELISA was developed to measure parasite antigens in dog sera. Parasite antigens were detected in 45 of 46 sera from infected dogs but were absent in sera from uninfected dogs and sera from dogs infected with Dipetalonema reconditum. Serum antigen content was significantly correlated with the number of female worms recovered from infected dogs (r = 0.82, p less than 0.001). Antigenemia was first detected 6 mo after infection, and antigen levels remained fairly stable between 9 and 21 mo after infection. Parasite antigen detection with this monoclonal antibody-based ELISA appears to be superior to previously described diagnostic methods for canine dirofilariasis in terms of sensitivity, specificity, and relation to infection intensity.

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PubMed1984

Detection of circulating parasite antigens in canine dirofilariasis by counterimmunoelectrophoresis.

Circulating Dirofilaria immitis antigen was detected in sera from 24 of 24 infected dogs by counterimmunoelectrophoresis (CIE). Parasite antigen was not detected in sera from uninfected dogs or dogs with Dipetalonema reconditum infection. In experimentally infected dogs, the antigen was first detectable 6.5-8.5 months after infection. Preliminary evidence suggests that the antigen is present in male and female adult worms but not in microfilariae. Sera from dogs with microfilaremic and amicrofilaremic infections contained statistically equivalent amounts of D. immitis antigen. However, a significant correlation was observed between serum parasite antigen content and the number of adult worms present in individual dogs at necropsy. Previous studies from several laboratories have shown that microfilarial counts and serum antibody titers are not related to adult worm counts in canine dirofilariasis or other filarial infections. Thus, CIE detection of D. immitis antigenemia represents a significant improvement over previously available diagnostic techniques because it is more sensitive than microfilarial tests, more specific than antibody tests, and the only test that has been related to infection intensity.

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PubMed1984

Antigens of Dirofilaria immitis which are immunogenic in the canine host: detection by immuno-staining of protein blots with the antibodies of occult dogs.

We describe here the profiles of antigens of Dirofilaria immitis that are immunogenic in dogs. Purebred beagle dogs were inoculated with a standard number of the infective third-stage larvae of the heartworm. Microfilaremia and anti-heartworm antibody levels were monitored by the Knott's test and by ELISA, respectively. Antibody-binding polypeptides were detected by immunoperoxidase staining of protein blots of detergent extracts of adult parasites from SDS-PAGE gels. Densitometric scans of these blots revealed considerable variation in the profiles of dirofilarial antigens detected by the sera obtained at different stages of the infection. Sera obtained during the prepatent phase, i.e., 3 mo post-infection (titer 1:2000), detected antigens of Mr 75, 80, 100, 130, and 200 kilodaltons. In addition to these antigens, sera obtained at the onset of microfilaremia, 6 mo post-infection (titer 1:30,000), detected antigens of Mr 15, 16, 18, 34, and 38 kilodaltons. Protein blots stained with sera from dogs, which subsequently cleared the microfilaremia and in which the infection became occult, showed that most of the antibody reactivities were directed at antigens of Mr 15, 21, and 38 kilodaltons. The variations in the species of molecules detected in sera obtained during the course of an infection seem to reflect fluctuations in the levels of specific antibodies directed at the individual heartworm antigens. We discuss the apparent role that the metamorphic differentiation of the parasite may play in determining the levels of reactivities of these antibodies at specific stages of the infection.

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PubMed1982

World Association for the Advancement of Veterinary Parasitology (W.A.A.V.P.) guidelines for evaluating the efficacy of anthelmintics in ruminants (bovine and ovine).

During the 8th International Conference of the World Association for the Advancement of Veterinary Parasitology (W.A.A.V.P.) held in Sydney, Australia, in 1977, President S. Gaafr appointed a committee to prepare international guidelines for evaluating the efficacy of anthelmintic products. The goal was to develop uniform testing standards and registration requirements to expedite the testing and approval of effective products with a minimum of labor, money, and experimental animals without sacrificing scientific validity. Achievement of such a goal would mean that data from investigators in one country could be used in registering drugs in another country. These guidelines, which were approved by the membership at the general meeting of the 9th International Conference of the W.A.A.V.P. on July 16, 1982 in Budapest, Hungary, are only a beginning in the development of uniform international methods for testing the efficacy of anthelmintics. We now propose that they be used by the scientific community recognizing that, at this time, these guidelines have not been officially reviewed or accepted by any government regulatory authority. Investigators are encouraged to evaluate this document critically and to recommend modifications promptly to the Committee so that they may be incorporated in these guidelines before the 10th International Conference to be held in Perth, Australia in 1983.

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PubMed1982

Dirofilaria immitis. VI. Antimicrofilarial immunity in experimental filariasis.

Antimicrofilarial immunity was studied in Dirofilaria immitis-infected dogs in order to better understand amicrofilaremic filariasis in man. Sera from dogs with amicrofilaremic infections contained IgG antibodies specific for microfilarial surface antigens detectable by immunofluorescence and in vitro leukocyte adherence. In vivo immune mechanisms were studied by injecting 51Cr-labeled microfilariae (MF) into infected and uninfected dogs. Injected MF were concentrated in lung, liver, spleen, and kidneys of normal and microfilaremic dogs, but circulated throughout the 5-hour study period. In contrast, injected MF were rapidly cleared (15-30 min) from the blood of amicrofilaremic-infected dogs. Tissue radioactivity and histopathology indicated that injected MF were trapped and destroyed in the lungs of these dogs. Antibody-dependent clearance and destruction of MF is a potent anti-helminth effector mechanism in canine dirofilariasis. Similar events are likely to occur in amicrofilameric filariasis in humans.

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PubMed1982

Developmental stages of Dirofilaria immitis in the dog.

Thirty-six Beagles were inoculated with 3rd-stage infective Dirofilaria immitis larvae to determine when 3rd and 4th molts occurred, how long each stage of development persisted in muscle and skin, and the patterns of larval migration from the infection site to the heart. From 22% to 84% of these larvae were recovered when the dogs were euthanatized and necropsied (mean recovery 45%). Larvae were recovered only from the skin and muscle during the first 58 days. The 5th-stage immature adults were first recovered from the heart in dogs killed on postinoculation day (PID) 70. Migration to the heart was essentially completed in dogs killed on PID 120, although 1 immature adult was recovered from subcutaneous tissues of each dog killed on PID 140 and 142. Starting and completion days of molting periods were recorded along with body lengths of male and female worms from the 3rd, 4th, and 5th stages. Microfilariae were first recovered from the peripheral blood in dogs killed on PID 190. Optimal time for drug evaluation against a particular stage of larval development is as follows: 3rd-stage larvae, PID 0 to 2; 4th-stage larvae, PID 15 to 50; and 5th-stage or immature adults, PID 65 to 120.

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PubMed1981

Rhesus monkeys protected against Plasmodium knowlesi malaria produce antibodies against a 65,000-MrP. knowlesi glycoprotein at the surface of infected erythrocytes.

Sera from 27 rhesus monkeys immunized in various ways against the H strain of Plasmodium knowlesi were analyzed by quantitative crossed immunoelectrophoresis. The reaction of the sera was compared with a reference immune serum only reactive with P. knowlesi-specific 65,000-Mr glycoprotein-immune component 13 (gp65/ic13) in membranes of infected rhesus monkey erythrocytes. Triton X-100-solubilized, 125I-labeled membranes of schizont-infected erythrocytes were used as an antigen. Sera from 9 or 10 monkeys immunized by repeated infections with P. knowlesi reacted with gp65/ic13. In 6 of 10 sera, anti-gp65/ic13 was the only antibody reacting with host cell membrane proteins. In contrast, vaccination of 15 monkeys with predominantly sexual stages or trophozoites of P. knowlesi in Freund complete adjuvant resulted in protection against blood challenges in 7 monkeys, only 2 of which contained precipitating antibody against gp65/ic13. None of the sera from monkeys not protected by infections or vaccinations contained detectable levels of precipitating antibodies against gp65/ic13. Our data indicate that gp65/ic13 acts as a prominent immunogen in vivo during natural p. knowlesi infections of rhesus monkeys. There is a positive correlation suggested between anti-gp65/ic13 antibody and protection in the monkeys analyzed. This correlation does not apply to monkeys protected against P. knowlesi malaria by vaccination, pointing to other effective immune defense mechanisms.

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PubMed1981

Dirofilariasis. IV. Glomerulonephropathy induced by Dirofilaria immitis infection.

The kidneys of dogs chronically infected with Dirofilaria immitis were studied by light, electron, and immunofluorescent microscopy. The glomeruli of dogs with high microfilaremia showed a moderately increased mesangium and thickened glomerular basement membrane. There was a deposition of electron-dense particles which were continuously distributed in the lamina rara interna and lamina densa of the glomerular basement membrane. Immunofluorescent microscopy showed intense IgG deposits in a uniform linear pattern along the glomerular basement membrane. This linear deposition of IgG appeared to correspond to continuous distribution of electron-dense particles in the basement membrane. Microfilariae present in the glomerular capillary lumens were connected with the capillary endothelial cells by narrow cytoplasmic bands. The interaction of the worm's internal substances with the glomerular capillaries through these cytoplasmic bands may deposit worm antigen on the glomerular capillary wall before antigen-antibody interaction takes place. These findings suggest that the glomerulopathy seen in dogs infected with D. immitis is caused by the in situ formation of immune complexes in the glomerular basement membrane.

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PubMed1981

Dirofilaria immitis. 5. Immunopathology of filarial nephropathy in dogs.

Fourteen beagles infected with larvae (microfilariae) of Dirofilaria immitis, were randomly selected from another study in which the toxic effects of subfilaricidal doses of diethylcarbamazine were being evaluated. This group of 14 dogs, together with 4 uninfected control animals, were variably sacrificed between 14 and 25 months after larval inoculations, and the ensuing renal lesions were studied by light and ultrastructural microscopy and by immunofluorescence and antibody elution techniques. On the basis of these studies, two groups of animals were distinguished. The first group was characterized by a striking pattern of linear fluorescence and fine ultrastructural dense deposits along the glomerular basement membrane, poor antibody response, and an inability to clear microfilariae from the tissues and circulation. The second group, with a nonlinear pattern of fluorescence, was characterized by a strong immune response, efficient elimination of microfilariae, and immunofluorescence and ultrastructural evidence of predominantly mesangiopathic immune complex renal disease. In both groups, elution studies demonstrated tissue deposits of antiworm antibodies, suggesting a filaria-antibody immune-complex nephropathy. No evidence was found for the presence of anti-basement-membrane antibodies. On the basis of a previous experimental model, it is postulated that in the first group of animals with linear fluorescence, the observed lesions may represent a natural form of an immunopathogenic mechanism of glomerular damage in which filarial antigen becomes uniformly localized in the glomerulus and elicits an autologous antibody response. The possible role of the drug diethylcarbamazine in inducing this mechanism of immune injury is discussed.

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PubMed1976

The preparation of malaria haemagglutination antigen.

Methods of preparing malaria antigen were compared. In one experiment a Ficoll density gradient was used to obtain a purified suspension of Plasmodium knowlesi schizonts from which antigen was prepared. Evaluation of methods such as freeze-thawing and the use of the French press following saponin lysis of schizonts demonstrated that a single freeze-thaw was the best method for obtaining the most antigen. A second experiment was done comparing the antigen prepared from schizont infected erythrocytes separated on a Ficoll density gradient with antigen prepared without separation of schizont infected erythrocytes on a Ficoll gradient. Saponin treatment of erythrocytes without the use of a Ficoll gradient followed by either freeze-thawing or the French press appeared to be the method of choice in preparing malaria IHA antigen.

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PubMed1974

Suppression of schistosome granuloma formation by malaria in mice.

Plasmodium berghei yeolii infection in mice suppressed granuloma formation around Schistosoma mansoni eggs in the lungs. This suppressive effect was observed as early as 4 days after schistosome eggs were injected into malaria-infected mice and the maximum suppressive effect was seen by the 16th day. At this time granulomas in control mice than in mice infected with malaria. These data suggest that malaria has a direct influence on an immunologic reaction of the delayed hypersensitivity type. There was no significant difference in the level of antibodies, specific for schistosome eggs, in the sera of the malaria-infected mice as compared to mice injected with S. mansoni eggs alone.

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