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Biomedical subjects

A A Gam

Publications and source records attributed to A A Gam.

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

Leishmania mexicana mexicana: quantitative analysis of the intracellular cycle.

The complete intracellular cycle of the Leishmania mexicana mexicana G. S. strain was quantified in human macrophages and in the mouse IC-21 macrophage line utilizing a culture system that allows the direct observation of individual intracellular parasites. A wide range of pre-replicative lag periods exists, implying that promastigotes may be in any phase of their DNA synthetic cycle when phagocytosed by the macrophage. Amastigotes replicated 2-3 times, after which the host cell died and liberated amastigotes that were taken up by other macrophages and continued to replicate. The mean amastigote population-doubling time in human macrophages (17.5 h) was not statistically different from promastigotes growing in axenic culture (16.4 h), but was nearly 2-fold less than amastigotes growing in mouse-derived IC-21 macrophages (33.7 h). These observations are markedly different from cover-glass culture assays of Leishmania-macrophage interactions and provide an unambiguous description of the intracellular cycle of Leishmania mexicana mexicana.

Animals↗
PubMed1989

Diffuse cutaneous leishmaniasis in Mexico.

In Mexico, 6 cases of diffuse cutaneous leishmaniasis (DCL) were found in widely separated geographic regions. Information was also available on 2 other cases. In addition to the typical clinical features, half of the patients had evidence of nasopharyngeal mucosal involvement. All isolates from the DCL patients were identified as Leishmania mexicana mexicana by isoenzyme analysis and monoclonal antibody typing. In 1 region of Tabasco state where DCL was found, uncomplicated cutaneous leishmaniasis appeared to be highly endemic, and isolates from a few such patients were identified as L. mexicana mexicana. An incidental finding was the recovery of an isolate of L. braziliensis braziliensis from a patient with chiclero ulcer in Oaxaca state. The clinical and epidemiological significance of the reported cases are discussed.

Adolescent↗
PubMed1988

Antigens from the surface and excretions/secretions of the filariform larva of Strongyloides stercoralis.

The surface and excretory/secretory (ES) antigens of the infective, filariform larva (L3) of Strongyloides stercoralis were identified. These studies provide a basis for the purification of these proteins as diagnostic allergens for human strongyloidiasis. The Mr values of the surface and ES molecules were determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and autoradiography, fluorography, or silver staining following the recovery of these molecules after the radiolabelling of living parasites. At least 10 surface proteins were radioiodinated extrinsically using chloroglycoluril as the catalyst for iodination, and then extracted with detergents and/or beta-mercaptoethanol. Several surface molecules of the L3 were immunogenic in humans, as determined by immunoprecipitation with sera (IHS) from infected patients. About 30 proteins were present in the ES preparation. Many ES antigens were labelled biosynthetically during the culture of larvae in media supplemented with either [35S]methionine or [14C]glucose. Furthermore, several of the surface proteins of the L3 were found with the ES antigens recoverable by culturing larvae in vitro. About 10 of the ES proteins were immunogenic as determined by immunoaffinity chromatography using IHS; and two of these antigens with Mr 50,000 and 90,000 incorporated [35S]methionine during culture of larvae. Moreover, some ES proteins were allergenic when tested in an in vitro assay of histamine release from basophils from infected humans or monkeys. The isotype of the homocytophilic antibodies involved in this immediate hypersensitivity assay, which is the basis of a diagnostic skin test for human strongyloidiasis, appears to be IgE.

Animals↗
PubMed1988

The immune response to nematode parasites: modulation of mast cell numbers and function during Strongyloides stercoralis infections in nonhuman primates.

Mucosal mast cell numbers are modulated in the intestines of rodents during parasitic infections. These mast cells can degranulate in response to worm antigens, and this event has been suggested to play a protective role for the host. To examine whether mast cells in higher animals play a role in protecting from disseminated parasitic disease, mast cell numbers and responsiveness to parasite antigens were evaluated in 5 Erythrocebus patas infected with the human intestinal nematode Strongyloides stercoralis. Initial infection and subsequent challenge infections were associated with increase in jejunal histamine and mast cell numbers, and these mast cells could release histamine in response to parasite antigens. Jejunal mast cell numbers returned to normal during a chronic phase of infection. The cells lost their ability to respond to antigenic stimulation following limited steroid treatment. Subsequent activation of chronic infections to fatal disseminated disease by more prolonged steroid treatment was associated with a marked decrease in jejunal mast cell numbers and histamine. In one animal which succumbed to severe disease without steroid treatment, jejunal mast cells were refractory to worm antigens.

Animals↗
PubMed1987

American trypanosomiasis (Chagas' disease) in Central American immigrants.

A survey was conducted to determine the prevalence of infection with Trypanosoma cruzi, the protozoan etiologic agent of American trypanosomiasis (Chagas' disease), among Nicaraguan and Salvadoran immigrants living in the Washington, D.C., area. The serum samples of study subjects were tested for reactivity with T. cruzi antigens in an enzyme-linked immunosorbent assay, and also tested for antibody specific for the 72 and 90 kilodalton (kDa) surface glycoproteins of the parasite in an immunoprecipitation and electrophoresis procedure. Xenodiagnosis using reduviid bugs to detect parasites, and clinical evaluations for cardiac and gastrointestinal disease were performed in patients in whom results of both serologic tests were positive. Of 205 subjects studied, 4.9 percent were infected with T. cruzi, and parasites were isolated from 50 percent of those in whom xenodiagnosis was attempted. No significant cardiac or gastrointestinal abnormalities were detected in the six infected patients who were evaluated clinically. These findings suggest that a sizable proportion of persons in this immigrant group are infected with this organism. Thus, routine serologic testing for antibody to T. cruzi may be warranted in immigrants from these countries, especially in view of the potentially serious consequences of infection with this parasite, and also because of the risk of transmission of T. cruzi by blood transfusion.

Chagas Disease↗
PubMed1987

Parasite-specific humoral responses in different clinical forms of strongyloidiasis.

Total IgE, specific IgE and IgG antibodies directed against Strongyloides stercoralis antigens were measured in the serum of 8 asymptomatic individuals with parasitologically proven strongyloidiasis, 10 patients with symptomatic strongyloidiasis and 8 with a severe form of the disease. No correlation was found between any of the immunological quantities evaluated and the clinical form of strongyloidiasis. We suggest that other responses may be involved in determining clinical manifestations of this parasitosis.

Antibodies, Helminth↗
PubMed1987

Comparative sensitivity and specificity of ELISA and IHA for serodiagnosis of strongyloidiasis with larval antigens.

Sera from 68 patients with parasitologically proven strongyloidiasis were tested by the ELISA and IHA tests using larval antigens prepared from Strongyloides stercoralis and Strongyloides ratti. The ELISA using the S. stercoralis antigen detected the greatest number of sero-reactors (83.8%), whereas the IHA using the S. ratti antigen detected the fewest (55.9%). In addition, the S. stercoralis antigen had higher geometric mean titers than the S. ratti antigen in both the ELISA and the IHA tests. Sera from 37 presumed normal individuals also were tested by IHA and ELISA and nonspecific reactions were seen only with the IHA test. When sera from patients with parasitic infections other than strongyloidiasis were tested, the only consistent cross-reactions were with those sera from patients who had occult filariasis and acute schistosomiasis.

Antibodies↗
PubMed1984

Experimental disseminated strongyloidiasis in Erythrocebus patas. II. Immunology.

Parasite-specific humoral and cellular immune responses were evaluated in seven Erythrocebus patas monkeys experimentally infected with a Southeast Asian strain of Strongyloides stercoralis. Most animals developed high titers of anti-larval surface IgG antibody (as evaluated by the indirect immunofluorescence test), and all animals tested developed specific IgE antibody (as shown by the in vitro histamine release test). Modest lymphoproliferative responses to S. stercoralis antigens were demonstrated in most animals during the early phase of the infection (days 20-40), but disappeared later. Steroid treatment (prednisone, 12.5 mg/kg on alternate days) was given to three animals, but did not appear to significantly affect the immune parameters tested. The degree of the immune responses to S. stercoralis larval antigens did not correlate well with the course of the infection, and several animals died of disseminated disease in spite of demonstrable humoral and cellular responses to these antigens. We suggest therefore that other factors, such as local intestinal immune and nonimmune mechanisms may be of importance in protection against disseminated strongyloidiasis.

Animals↗
PubMed1983

Immunologic responses to experimental strongyloidiasis in rats.

Humoral and cellular immune responses were evaluated in Lewis rats infected with high (3000) inocula of Strongyloides ratti larvae (L3). The responses of peripheral and mesenteric node lymphocytes to crude larval antigen (by lymphocyte proliferation assay) sharply rose between days 12 and 16 of the primary infection and days 8 and 12 of the challenge, and decreased promptly to almost preinfection levels. Spleen lymphocytes failed to show any response to the primary infection, but did exhibit a modest response after challenge. The responses of peripheral lymphocytes to the mitogen phytohemagglutinin fell considerably on infection day 8 and then rose sharply to very high levels. Reinfection caused a small decrease in responsiveness, followed by another increase after 10 days. Inoculation of 3000 heat-killed larvae stimulated a response in peripheral lymphocytes similar to that elicited by the inoculation of live larvae. Spleen lymphocytes appeared to be stimulated more by the killed larvae inoculation, whereas only a limited response was found in mesenteric node lymphocytes in animals inoculated with dead larvae. IgG antibody titers against S. ratti antigen were measured by the enzyme-linked immunoabsorbent assay (ELISA). A significant elevation was noted between days 12 and 20 with a return to pre-infection levels between days 80 and 150. Challenge with 3,000 L3 induced a rapid and significant elevation. These data indicate that in rats experimentally inoculated with large numbers of S. ratti larvae a direct relationship exists between the development of cellular and humoral immune responses to larval antigens, the expulsion of the intestinal worms, and the acquisition of resistance to subsequent challenge.

Animals↗
PubMed1983

Specific allergic sensitization to Strongyloides antigens in human strongyloidiasis.

Reaginic antibodies to antigens from the human parasite Strongyloides stercoralis were studied by histamine release from basophils in 15 patients with chronic uncomplicated strongyloidiasis and in 12 controls (six North Americans with no evidence of parasitic diseases, two patients with Schistosoma mansoni, two with hookworm, one with Ascaris lumbricoides, and one with Onchocerca volvulus). All of the patients had antibodies to the somatic larval antigens, and 14 of 15 patients also had antibodies to the excretory/secretory products of S. stercoralis larvae. None of the controls had a positive response to any of the antigens tested. These findings indicate that patients with chronic strongyloidiasis have parasite-specific IgE antibodies and that S. stercoralis larval allergens may have a potential role in the immunodiagnosis of strongyloidiasis.

Antigens↗
PubMed1982

Antibody levels to Trypanosoma cruzi in infected patients with and without evidence of chronic Chagas' disease.

Antibody levels to Trypanosoma cruzi were compared in asymptomatic individuals infected with the parasite as well as those with different forms of chronic Chagas' disease of varying severity. The following three serologic tests were used: complement fixation, direct agglutination with previous treatment of the serum with 2-mercaptoethanol, and the enzyme-linked immunosorbent assay. The clinical groups tested included individuals with (a) a positive serology but no symptoms and without evidence of chronic disease (indeterminate form); (b) mega disease (groups I, II, III, and IV); (c) cardiomyopathy (mild, moderate, and severe); and (d) those with both mega disease and cardiomyopathy (combined form). The mean enzyme-linked immunosorbent assay and complement fixation antibody levels among the various clinical groups showed no statistical differences. With the direct agglutination test patients with mega disease and those with severe cardiomyopathy had slightly higher mean titers than patients in the indeterminate group and those with mild or moderate cardiomyopathy. While there may be possible reasons for these differences, the biological relevance of the findings was concluded to be of dubious significance.

Adult↗
PubMed1981

Comparison of larval antigens in an enzyme-linked immunosorbent assay for strongyloidiasis in humans.

An enzyme-linked immunosorbent assay for specific antibodies in patients with strongyloidiasis was developed using antigens extracted from the third-stage larvae of Strongyloides stercoralis and Strongyloides ratti. Sera from two groups of patients with strongyloidiasis proven by parasitologic methods, including one group of 29 coded positive sera, and from presumed normal subjects as controls were tested. Sera with optical density values greater than two standard deviations above the mean optical density value for the sera from control subjects were considered to be positive. Using this criterion 82%-84% of 51 positive patients had antibodies to S. stercoralis or S. ratti antigens. Immunosuppression and other factors that might influence antibody responses were associated with some patients who were negative for antibodies to Strongyloides. Antigen from an intestinal nematode of rats, Nippostrongylus brasiliensis, was also evaluated and found to be unsuitable for serodiagnosis of strongyloidiasis because of frequent false-positive as well as false-negative results.

Adult↗
PubMed1977

A complement-fixing antigen from Trypanosoma cruzi grown in cell cultures.

A complement-fixing (CF) antigen was prepared from amastigotes and trypomastigotes of Trypanosoma cruzi (Ernestina strain) grown in beef embryo cell cultures. Multiple lots of the antigen, which consisted of a supernate of washed and disrupted organisms, required material from 10(6) to 10(7) total organism per ml for optimum CF activity. Antibody at dilutions up to 1:256 was demonstrable in various sera from infected animals or patients. Contaminating beef cells from infected cultures were shown to be partly responsible for crossreactions of the antigen by CF with sera from cases of cutaneous leishmaniasis in whom concomitant infection with T. cruzi could be excluded. There were no cross-reactions with syphilitic sera and the frequency of positive reactions with normal sera was very low. Some characterisitics of the antigen included stability to storage at -20 degrees C and -70 degrees C for months, inactivation at 60 degrees C and by lyophilization, and an estimated molecular size of between 50,000 and 100,000 on the basis of membrane filtration.

Animals↗
PubMed1977

Comparison of cell culture with epimastigote antigens of Trypanosoma cruzi.

Various epimastigote antigens of Trypanosoma cruzi were compared with an amastigote-trypomastigote antigen from infected cell cultures by complement fixation (CF) and gel diffusion (Ouchterlony). CF results with human Chagasic sera showed that the amastigote-trypomastigote antigen was usually more sensitive than epimastigote antigens tested. In addition, cross-reactions with normal and other sera were no greater and perhaps less frequent than with crude epimastigote antigens. Specificity of the amastigote-trypomastigote antigen, however, was less than with a protein extract of epimastigotes. Gel diffusion results with human Chagasic and hyper-immunized rabbit sera indicated differences between epimastigote and amastigote-trypomastigote antigens whereas differences by CF with the same sera were equivocal.

Animals↗
PubMed1974

Relationship of serum complement levels to events of the malarial paroxysm.

Malarial paroxysms due to Plasmodium vivax were studied for alterations in whole serum complement (C') and certain C' components. The objective was to relate C' values with events of the parasite cycle during schizogony and with the febrile pattern. Substantial decreases in C' were found in 9 of 18 paroxysms studied during relapse. In contrast, only one of 22 paroxysms occuring during the primary attack was associated with a striking depression in C', and this case exhibited certain characteristics of a relapse paroxysm. The mean change in C' levels during paroxysms in relapse (-23%) was significantly different from paroxysms of the primary attack (-2%). Depletion of C' was associated directly with degree of parasitemia and presence of complement-fixing (CF) antibody. Lowest levels of C' were found within a few hours after completion of schizont repture and peak fever. C4 levels reflected changes in whole serum C' and appeared to be a more sensitive indicator of C' alterations during malaria. While the alterations in C4 as well as C1 and C2 indicated that the classical C' pathway was involved, some preliminary results showed little or no depletion of late components, C3 and C6. Overall results are compatible with C' activation and depletion during or soon after schizont repture if parasite density is sufficiently high and if CF antibody is present.

Adult↗