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C L Chappell

Publications and source records attributed to C L Chappell.

At least 37 records · Page 2Linked to original sources
PubMed1998

Susceptibility and serologic response of healthy adults to reinfection with Cryptosporidium parvum.

Healthy adults are susceptible to infection with small numbers of Cryptosporidium parvum oocysts, resulting in self-limited infection. We investigated if infection of humans with C. parvum is protective 1 year after primary exposure. At 1 year after a primary challenge with 30 to 10(6) oocysts, 19 healthy immunocompetent adults were rechallenged with 500 oocysts and monitored for the development of infection and/or illness. Oocyst excretion was quantitated by direct immunofluorescence with a C. parvum-specific monoclonal antibody, and anti-C. parvum antibodies in serum were detected by an enzyme-linked immunosorbent assay. Fewer subjects shed oocysts after the second exposure (3 of 19; 16%) than after the first exposure (12 of 19; 63%) (P < 0.005). Although the rates of diarrhea were comparable after each of the two exposures, the clinical severity as determined by the mean number of unformed stools passed was lower after reexposure (11.25 versus 8.62; P < 0.05). The number of anti-Cryptosporidium immunoglobulin G and A seroconversions increased after secondary exposure. However, the C. parvum serum antibody response did not correlate with the presence or absence of infection.

Adult↗
PubMed1997

Characterization of a cysteine proteinase from Taenia crassiceps cysts.

Human neurocysticercosis, due to infestation of the central nervous system with Taenia cysts, is a common cause of neurologic disease in endemic areas and is being increasingly recognized in the United States. Previous studies have suggested that Taenia cysts bind host IgG via Fc-like receptors and that bound IgG is degraded by the parasite, perhaps as a source of nutrients or a means of immune evasion. We now demonstrate that IgG degradation is thiol dependent and is inhibited by the cysteine proteinase inhibitor, E-64. The cysteine proteinase activity from Taenia crassiceps cysts was purified 682-fold by acid extraction, gel filtration chromatography, and anion-exchange FPLC. The cysteine proteinase appeared as a 43 kDa band on silver-stained gels. Its isoelectric point was 5.27. The purified enzyme was inhibited by cysteine proteinase inhibitors and also by chloromethyl ketone inhibitors, but not significantly by other inhibitors of serine, aspartic, or metallo-proteinases. Substrate studies showed pronounced cleavage of Z-Phe-Arg-7-amino-4-trifluoromethylcoumarin (Z-Phe-Arg-AFC), but not of substrates with neutral or positively charged amino acids in the P2 position. Km for Z-Phe-Arg-AFC was 1.0 x 10(-7) M, Kcat 58 s-1, and Kcat/Km 5.8 x 10(8) mol-1s-1. Amino acid sequencing of the amino terminus revealed a single cysteine residue with surrounding residues suggestive suggestive of a cysteine proteinase active site. The sequence, however, did not contain the conserved active site associated with enzymes of known cysteine proteinase families. This cysteine proteinase may play an important role in the interaction of Taenia cysts and host immunoglobulin and is a potential target for antiparasitic chemotherapy.

Amino Acid Sequence↗
PubMed1997

Cryptosporidiosis in Houston, Texas. A report of 95 cases.

Cryptosporidiosis is an important cause of diarrhea. We identified 95 patients with cryptosporidiosis over a 6-year period in our county hospital system, including 9 children and 86 adults infected with the human immunodeficiency virus (HIV). Risk factors included male-to-male sexual practices and Hispanic race. Diarrhea, weight loss, and gastrointestinal complaints were the most common symptoms at presentation. Among the HIV-infected adults, 20 (23%) developed biliary tract disease. Biliary involvement was associated with low CD4 counts. Treatment with paromomycin and antimotility agents was effective in reducing diarrheal symptoms in 54 of 70 (77%) patients with the acquired immunodeficiency syndrome (AIDS), although there was a high rate of relapse. Paromomycin did not prevent the development of biliary disease. Biliary disease responded to cholecystectomy or sphincterotomy with stent placement. Though often a cause of morbidity, cryptosporidiosis was only rarely the cause of death, even among patients with HIV. Cryptosporidiosis continues to be an important medical problem even in developed-countries. Current methods of prevention and treatment are suboptimal.

AIDS-Related Opportunistic Infections↗
PubMed1997

Flow cytometric detection of Cryptosporidium oocysts in human stool samples.

Cryptosporidium parvum is an important pathogen that causes diarrhea in virtually all human populations. Improved diagnostic methods are needed to understand the risk factors, modes of transmission, and impact of cryptosporidiosis. In the present study, we fluorescently labeled and counted C. parvum oocysts by flow cytometry (FC) and developed a simple and efficient method of processing human stool samples for FC analysis. Formed stool (suspended in phosphate-buffered saline) from an asymptomatic, healthy individual was seeded with known concentrations of oocysts, and oocysts were labeled with a cell wall-specific monoclonal antibody and detected by FC. The method described herein resulted in a mean oocyst recovery rate of 45% +/- 16% (median, 42%), which consistently yielded a fourfold increase in sensitivity compared to direct fluorescent-antibody assay of seeded stool samples. However, in many instances, FC detected as few as 10(3) oocysts per ml. Thus, FC provides a reproducible and sensitive method for C. parvum oocyst detection.

Animals↗
PubMed1996

Cryptosporidium parvum: intensity of infection and oocyst excretion patterns in healthy volunteers.

Data about human Cryptosporidium parvum infection have originated from travelers, community and day care center outbreaks, and persons infected with the human immunodeficiency virus. In addition, experimental infection in 29 antibody-negative, healthy, adult volunteers generated information on the dose-infection response of C. parvum (Iowa strain). In that report, low inocula were sufficient to cause infection in 18 and illness in 7 persons. To further define the duration and intensity of infection in this population, oocyst shedding patterns were investigated in the 18 subjects infected with C. parvum. Oocyst quantitation revealed that volunteers with diarrheal illness (n = 7) excreted more oocysts over the course of the infection than did volunteers without diarrhea (n = 11; P < .05). Symptomatic subjects were more likely to shed oocysts on consecutive days. Further, a statistical nonsignificant inverse trend (r2 = .330, P = .136) was seen between challenge dose and total excreted oocysts. This paradox may relate to receptor saturation or a toxic effect on cells, parasites, or both afforded by a high inoculum.

Animals↗
PubMed1996

Cryptosporidium parvum metalloaminopeptidase inhibitors prevent in vitro excystation.

Cryptosporidium parvum arginine aminopeptidase (RAP) was studied during in vitro excystation. Specific RAP inhibitors were identified by using C. parvum extracts. Amastatin, a series of alpha-aminoboronic acids, and the chelating agents EDTA and 1,10-phenanthrolene, but not endoproteinase inhibitors, blocked enzymatic activity. RAP inhibitors found to be effective in soluble enzymatic assays were then studied for their effect on in vitro excystation. 1,10-Phenanthrolene, amastatin, and H-boronorleucine (pinacol) inhibited excystation by 84, 57, and 61%, respectively, compared with solvent-treated control oocysts. Sporozoites remained viable within the oocyst as determined by propidium iodide and fluorescein diacetate dye uptake, suggesting that alpha-aminoboronic acids were not directly lethal to the parasite.

Aminopeptidases↗
PubMed1995

The infectivity of Cryptosporidium parvum in healthy volunteers.

BACKGROUND: Small numbers of Cryptosporidium parvum oocysts can contaminate even treated drinking water, and ingestion of oocysts can cause diarrheal disease in normal as well as immunocompromised hosts. Since the number of organisms necessary to cause infection in humans is unknown, we performed a study to determine the infective dose of the parasite in healthy adults. METHODS: After providing informed consent, 29 healthy volunteers without evidence of previous C. parvum infection, as determined by the absence of anti-cryptosporidium-specific antibodies, were given a single dose of 30 to 1 million C. parvum oocysts obtained from a calf. They were then monitored for oocyst excretion and clinical illness for eight weeks. Household contacts were monitored for secondary spread. RESULTS: Of the 16 subjects who received an intended dose of 300 or more oocysts, 14 (88 percent) became infected. After a dose of 30 oocysts, one of five subjects (20 percent) became infected, whereas at a dose of 1000 or more oocysts, seven of seven became infected. The median infective dose, calculated by linear regression, was 132 oocysts. Of the 18 subjects who excreted oocysts after the challenge dose, 11 had enteric symptoms and 7 (39 percent) had clinical cryptosporidiosis, consisting of diarrhea plus at least one other enteric symptom. All recovered, and there were no secondary cases of diarrhea among household contacts. CONCLUSIONS: In healthy adults with no serologic evidence of past infection with C. parvum, a low dose of C. parvum oocysts is sufficient to cause infection.

Adult↗
PubMed1995

Intestinal function and injury in acquired immunodeficiency syndrome-related cryptosporidiosis.

BACKGROUND/AIMS: The pathogenesis of the diarrhea in acquired immunodeficiency syndrome (AIDS)-related cryptosporidiosis is not known. The hypothesis of this study was that the intestinal dysfunction and injury are related to the number of organisms infecting the intestinal mucosa. The aim of this study was to study the influence of intensity of infection on intestinal function and injury in AIDS-related cryptosporidiosis. METHODS: In 16 patients with AIDS with intestinal Cryptosporidium infection, the intensity of infection was quantified by counting the total number of fecal oocysts excreted in 24 hours and by determining the percent of duodenal epithelium covered by organisms. Intestinal function was assessed by vitamin B12 absorption and serum D-xylose test. Intestinal injury was assessed by morphology of duodenal mucosa, differential urinary excretion of lactulose and mannitol, and fecal alpha 1-antitrypsin clearance. Measurements were repeated after treatment with paromomycin. RESULTS: Vitamin B12 and D-xylose absorption negatively correlated with intensity of infection. Villus atrophy occurred only in patients with oocyst excretion of > 10(8) oocyst/24 hours. Lactulose/mannitol urinary excretion ratio showed a positive correlation with intensity of infection. Intestinal function and injury improved in patients whose oocyst counts were reduced by treatment with paromomycin. CONCLUSIONS: Cryptosporidium infection in patients with AIDS causes malabsorption and intestinal injury in proportion to the number of organisms infecting the intestine.

AIDS-Related Opportunistic Infections↗
PubMed1994

Paromomycin for cryptosporidiosis in AIDS: a prospective, double-blind trial.

To test the effects of paromomycin, 10 patients with AIDS and cryptosporidiosis were randomized to paromomycin or placebo in a double-blind trial. After 14 days, patients were switched to the other treatment for 14 additional days. Measures included the number and character of each stool and weekly 24-h stool specimens for weight and oocyst excretion. During the paromomycin treatment phase, oocyst excretion decreased from 314 x 10(6) to 109 x 10(6)24 h (P < .02). Oocyst excretion increased for the 4 patients initially on placebo compared to a median decrease of 128 x 10(6)/24 h for the 6 initially treated with drug (P < .02). Stool frequency also decreased more in those treated with drug (3.6 fewer vs. 1.25 fewer/24 h, P < .05). Trends favored drug over placebo for stool weight, stool character, and Karnofsky score. Paromomycin treatment resulted in improvement in both clinical and parasitologic parameters in cryptosporidiosis in AIDS.

AIDS-Related Opportunistic Infections↗
PubMed1994

Arginine aminopeptidase, an integral membrane protein of the Cryptosporidium parvum sporozoite.

Cryptosporidium parvum oocysts were studied for the expression of aminopeptidase by using amino acids bound to the synthetic fluorescent substrate 7-amino-4-trifluoromethyl coumarin. After 1 h of incubation, intact oocysts showed no activity; however, homogenization and solubilization with Triton X-114 followed by phase separation yielded a 22-fold increase in aminopeptidase activity in the detergent fraction. With arginyl-6-amino-2-styrylquinoline as a substrate, aminopeptidase activity was observed in permeabilized oocysts and freshly excysted sporozoites but not on intact oocysts or empty oocyst membranes after excystation. These results suggest that C. parvum expresses an arginine aminopeptidase that is an integral protein of the sporozoite membrane.

Aminopeptidases↗
PubMed1993

Duodenal morphology and intensity of infection in AIDS-related intestinal cryptosporidiosis.

BACKGROUND: The pathogenesis of intestinal cryptosporidiosis is not known. Previous studies have shown that the intensity of infection varies between patients. The hypothesis of this study is that intestinal injury is related to the intensity of infection. METHODS: The histological abnormalities associated with Cryptosporidium infection were evaluated in duodenal biopsy specimens from 18 patients with acquired immunodeficiency syndrome-associated cryptosporidiosis. The intensity of Cryptosporidium infection was assessed histologically in all patients as the percentage of mucosa covered by organisms and by quantitation of oocyst excretion in the stools of 14 patients. RESULTS: Duodenal biopsy specimens from 13 patients (72%) showed normal villous architecture. In these patients, the inflammatory component of the lamina propria was either normal or moderately increased. This increase consisted mostly of lymphocytes and plasma cells. Five of 18 patients (28%) had flattening of the mucosa associated with a prominent neutrophilic infiltrate. The intensity of infection in patients with villous flattening as measured from biopsy specimens and stool was significantly higher than in those without flattening (92% vs. 12% mucosa occupied with organisms; 738 x 10(3) vs. 199 x 10(3) oocyst/mL stool) (P < 0.004 in both cases). CONCLUSIONS: Most patients with intestinal Cryptosporidium infection had normal duodenal villous architecture. Severe duodenal morphological abnormalities, including flattening of the villi, were associated with high-intensity infections.

AIDS-Related Opportunistic Infections↗
PubMed1993

Intensity of infection in AIDS-associated cryptosporidiosis.

A fluorescent monoclonal anti-Cryptosporidium antibody was used to count the oocysts in stools of 12 AIDS patients with chronic cryptosporidiosis. Oocyst excretion was present throughout the day in all 12 patients. Stool-to-stool variation in oocyst concentration was within one order of magnitude. Small variations were also found in daily mean oocyst concentration and total daily oocyst excretion in 3 patients who had multiple 24-h stool collections. However, there was a large patient-to-patient variation in mean oocyst concentration (from < 5.0 x 10(3) to 9.2 x 10(5) oocysts/mL) and 24-h total oocyst excretion (from < 6.0 x 10(6) to 1.2 x 10(9) oocysts/day). There was a significant correlation between oocyst excretion and numbers of Cryptosporidium organisms seen on small bowel biopsy. Oocyst excretion was reduced in 4 patients treated with paromomycin, but diarrhea improved only in the 2 patients with high initial oocyst excretion.

AIDS-Related Opportunistic Infections↗
PubMed1993

Purification and partial characterization of cysteine proteinase from Spirometra mansoni plerocercoids.

Spirometra mansoni plerocercoids were dissected from the tissues of naturally infected snakes (Natrix trigrialateralia). Fresh plerocercoids were incubated in medium, and excretory-secretory products (E-S) were collected. In addition, soluble proteins from lyophilized plerocercoids (10 mg/ml) were extracted in 0.1 M sodium acetate. Proteinase activity was assayed with a synthetic fluorescent substrate, carbobenzoxy-phenylalanyl-arginyl-7-amino-4-trifluoromethylcoumarin. Proteinase was isolated from plerocercoid extract or E-S by diethylaminoethyl trisacryl M ion-exchange chromatography and thiolpropyl-Sepharose affinity chromatography. These separations resulted in a 12.2- (extract) and 15.6-fold (E-S) purification of proteinase. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of the purified materials revealed a 28-kDa band, consistent with the apparent native molecular weight (gel filtration chromatography) of approximately 35 kDa. Proteinases purified from whole extracts and E-S were compared for various biochemical characteristics; inhibitor profiles indicated that activities from both sources are cysteine proteinases, they exhibited identical pH curves with optima at pH 5.5 and a 50% activity range at pH 4.7-8.0, they cleaved collagen chains to 3 identical products, and they showed only minor activity toward hemoglobin. Further, the proteinase purified from plerocercoids was utilized in immunoblots with sera from sparganosis patients. Antibody (IgG) from the infected patients, but not uninfected controls, recognized the cysteine proteinase, suggesting that this antigen may be useful in the serodiagnosis of Spirometra mansoni infection.

Animals↗
PubMed1993

Proteinase activity in miracidia, transformation excretory-secretory products, and primary sporocysts of Schistosoma mansoni.

Proteinase activity was detected in the culture medium of transforming miracidia and in detergent extracts of Schistosoma mansoni miracidia and primary sporocysts using a fluorescent substrate, carbobenzoxy-phenylalanyl-arginyl-7-amino-4- trifluoromethylcoumarin. Medium collected after the first 24 hr of miracidial cultivation (transformation medium; TM) contained most (80%) of the activity released during 5 days of in vitro culture. Based on proteinase activity contained in Triton X-100 extracts of whole larvae, miriacidia and primary sporocysts exhibited a similar amount of total activity per organism, whereas specific activity was about 2-fold greater in miracidia. Approximately 10% of total miracidial activity was released during the first 24 hr of transformation. This early release of proteinase is consistent with possible involvement of these enzymes in miracidial snail penetration. Proteinase activities from larval extracts and culture media were identical when characterized for thiol-dependence, inhibitor profile, and pH optimum and indicate that the proteinase(s) belongs to the cysteine class of acidic endopeptidases. Further studies with TM revealed a substrate preference for a hydrophobic amino acid in the P2 position. High performance liquid chromatography gel filtration showed 2 peaks of activity at 19,000 and 36,000 Da, whereas specific inhibitor labeling yielded heterogeneous banding in the molecular weight range of 33,000-44,000 Da. Lastly, sporocyst extracts incubated with snail plasma (cell-free hemolymph) revealed degradation of high molecular weight hemolymph proteins, including hemoglobin. The finding of significant cysteine proteinase activity in miracidia and primary sporocysts and the continued low level of secretion by sporocysts suggest a functional role of these proteinases in the establishment and/or maintenance of infections within the snail host.

Animals↗
PubMed1992

Giardia antigen detection in patients with chronic gastrointestinal disturbances.

BACKGROUND: Giardia lamblia, a protozoan parasite, is transmitted by cysts in contaminated water or food or by person-to-person contact. The standard in diagnosis has been the microscopic demonstration of fecal cysts, which yields many false negatives due to high variability in cyst excretion. A new method that detects infection even when few parasites are present is now available. This immunodiagnostic test is rapid, sensitive, and specific, and typically requires only a single stool specimen. In this study patients with gastrointestinal (GI) complaints were screened for Giardia antigens, and the test results were compared to conventional microscopy. Costs incurred by patients with chronic GI problems were documented. METHODS: Twelve patients with GI complaints were tested for Giardia by microscopy and 13 patients by the immunodiagnostic test. Patient charts were evaluated for pertinent history and the diagnostic tests ordered before giardiasis was considered. RESULTS: For all patients, microscopy was uniformly negative, but 6 of 13 patients were antigen positive. Patients with chronic complaints, later found to test positive for Giardia, typically underwent five diagnostic tests at a cost of $338. CONCLUSIONS: Giardiasis, an increasing problem in family practice, should be considered early in patients with GI disturbances. New, sensitive immunodiagnostic tests that usually require a single specimen are more useful than microscopy. Prompt diagnosis of giardiasis not only relieves patients of unpleasant symptoms, but can avoid unnecessary and costly evaluations.

Adult↗
PubMed1990

Antibody response to Schistosoma mansoni adult worm cysteine proteinases in infected individuals.

Antigens of the Schistosoma mansoni digestive tract are recognized early in the infective process. Two immunogenic components of the excretory/secretory products are proteolytic enzymes that degrade host hemoglobin in the lumen of the parasite gut. These enzymes, CP1 and CP2, belong to the class of cysteine proteinases. In this study, a preparation containing both proteinases has been used to detect proteinase antibodies in the sera of individuals living in Burundi. Of 133 individuals tested, 92% were excreting schistosome eggs. All patients with documented infections had positive anti-proteinase IgG titers (mean = 1:614), while 82% had positive IgM titers (mean = 1:267). Six weeks following praziquantel treatment, patients were assessed for egg excretion and antibody titer. Anti-proteinase IgG titers were significantly lower (mean = 1:259) than pre-treatment titers. Patients who were infected with S. japonicum or S. haematobium typically showed a cross-reactive IgG response. Patients from non-endemic regions yielded negative titers, and those with non-trematode parasites were negative (79%) or weakly positive. S. mansoni cysteine proteinases may be used for the detection of schistosome infections.

Adolescent↗