Prospective audit of cross-sectional imaging and radiation exposure in general surgical patients

INTRODUCTION

Most patients admitted with an acute surgical problem undergo some imaging during their in-patient stay. As computed tomography (CT) scanning becomes more readily available, it is becoming the mainstay of assessment. Recent studies have commented on the potential adverse effects of early cross-sectional imaging. This audit aimed to determine the use of early cross-sectional imaging and associated radiation dose in an acute surgical cohort.

PATIENTS AND METHODS

Data from 500 acute surgical patients were prospectively collected over a 3-month period. CT scans were undertaken, the effect on subsequent diagnostic and management decisions and the potential associated risks were evaluated.

RESULTS

Almost 40% of subjects underwent CT scanning. Of these, 20% did not alter management and could be deemed unnecessary. The radiation exposure equated to an age- and gender-specific risk of fatal cancer induction between 1 in 1675 and 1 in 7130.

CONCLUSIONS

Early-cross sectional imaging provides a valuable diagnostic adjunct. Decisions to expose patients to potentially hazardous radiation need to acknowledge the anticipated benefits versus risks.

Characterization of a cytosolic aminopeptidase from Encephalitozoon intestinalis

Aminopeptidase activity was detected in Encephalitozoon intestinalis using a fluorometric assay. The aminopeptidase was capable of hydrolysing different amino acids bound to 7-amino-4-trifluoromethyl coumarin, with maximal activity against the amino acid, leucine. Aminopeptidase activity was localized in E. intestinalis spores and in intracellular stages. Enzymatic activity was inhibited by the traditional aminopeptidase inhibitors, bestatin and its analogue, nitrobestatin. Inhibition with the chelating agents, EDTA and 1,10-phenanthroline, suggested that the enzyme activity belongs to the metalloaminopeptidase class. Subcellular fractionation demonstrated that maximal enzyme activity was localized in the cytosolic fraction. Direct fluorogenic substrate analysis by native polyacrylamide gel electrophoresis estimated a molecular weight of 70.8 kDa. Direct fluorogenic analysis by polyacrylamide ampholyte gel electrophoresis indicated an isoelectric point of 4.8. The enzyme was both heat (> 37 degrees C) and cold (< 0 degrees C) labile with an optimal activity at pH 7.2. This is the first report characterizing a cytosolic aminopeptidase in microsporidia.

Risk assessment for Cryptosporidium: a hierarchical Bayesian analysis of human dose response data

Three dose-response studies were conducted with healthy volunteers using different Cryptosporidium parvum isolates (IOWA, TAMU, and UCP). The study data were previously analyzed for median infectious dose (ID50) using a simple cumulative percent endpoint method (Reed and Muench, 1938). ID50s were derived using two definitions of infection: one as subjects having oocysts detected in stool by direct fluorescence assay, and the other by a clinical finding of diarrhea with or without detected oocysts (Chappell et al., 1998; Okhuysen et al., 1999). In the present study, the data were analyzed using the broader definition of infection (i.e., presence of oocysts in stool and/or diarrheal illness characteristic of cryptosporidiosis). Maximum likelihood dose-response parameter estimates for UCP, IOWA, and TAMU were 2980, 190, and 17.5, respectively. Based on these estimates, the ID50s of the three respective isolates were 2066, 132, and 12.1. The three oocyst isolates were considered representative of a larger population of human-infecting strains and analyzed as combined data using a hierarchical Bayesian model. Hyperparameters defined the distribution of dose-response parameters for the population of strains. Output from Markov Chain Monte Carlo analysis described posterior distributions for the hyperparameters and for the parameters of the IOWA, TAMU, and UCP strains. Point estimates of dose-response parameters produced by this analysis were similar to the maximum likelihood estimates. Finally, the utility of these results for probabilistic risk assessment was evaluated. The risk of infection from single oocyst doses was derived for a mixture of the three isolates (where IOWA, TAMU, or UCP are equally likely), and for an oocyst selected at random from the larger population of strains. These estimated risks of infection were 0.018 and 0.028, respectively.

Impact of breast-feeding on Giardia lamblia infections in Bilbeis, Egypt

A total of 152 infants were followed from birth to 1 year of age in a rural community of Egypt to document Giardia lamblia infection and to determine the effect of breast-feeding on enteric infections by this protozoan. Asymptomatic Giardia infections persisted as long as 4 months, with a mean duration of excretion of 7.18 weeks. The incidence of asymptomatic infection was 4.5 episodes per child-year. Exclusively breast-fed infants had lower risk for asymptomatic (odds ratio [OR] = 0.66, 95% confidence interval [CI] = 0.45-0.96, P < 0.05) and symptomatic infections (relative risk [RR] = 0.50, 95% CI = 0.27-0.90, P < 0.05). Furthermore, breast-fed infants had fewer clinical manifestations, including mucus in stool (23.8% versus 76.2%, P = 0.08), loss of appetite (17.6% versus 82.3%, P < 0.05), and abdominal tenderness (17% versus 82.9%, P < 0.05) compared with infants who were not exclusively breast-fed. Breast-feeding should be considered as an effective means to prevent Giardia infections and should be encouraged in regions where G. lambia is highly endemic.

The role of hepatitis C in hepatocellular carcinoma: a case control study among Egyptian patients

BACKGROUND

Egypt has one of the highest prevalence rates of hepatitis C virus (HCV) infection in the world; however, the risk and attribution related to HCV in Egyptian patients with hepatocellular carcinoma (HCC) remains unknown.

GOALS

The current study was undertaken to estimate the risk of HCC in relation to HCV in Egypt.

STUDY

Thirty-three patients with HCC and 35 healthy controls who had a similar socioeconomic status were prospectively enrolled at the University of Cairo National Cancer Institute.

RESULTS

Anti-HCV antibodies were present in 75.8% of the patients and in 42.9% of the controls (p = 0.01); hepatitis B surface antigen (HBsAg) was present in 15.2% of the patients and in 2.9% of the controls (p = 0.03). In addition, the sex-and age-adjusted odds ratio (OR) for anti-HCV antibodies was 5.1 (95% CI = 1.5-17.4) and for HBsAg was 13.2 (95% CI = 1.2-148.2). Concurrent Schistosoma mansoni and anti-HCV was associated with an OR of 10.3 (95% CI = 1.3-79.8), which was higher than that for anti-HCV (6.5; 95% CI = 1.6-26.6) and S. mansoni infection (0.2; 95% CI = 0.1-6.2) alone. Finally, we estimated the attributable fraction of HCC to HCV to be 64% in this study population and 48% in the general Egyptian population.

CONCLUSIONS

Both HCV and hepatitis B virus infection increase the risk of HCC in Egyptian patients, whereas isolated Schistosoma infection does not. Because of the very high prevalence rate of HCV in the general Egyptian population, it accounts for most HCC cases in Egypt.

Expression of IL-15 and IL-4 in IFN-gamma-independent control of experimental human Cryptosporidium parvum infection

We have previously demonstrated interferon gamma (IFN-gamma) in intestinal mucosa after experimental human Cryptosporidium parvum infection, but expression was limited to sensitized volunteers. To characterize IFN-gamma-independent mechanisms in control of infection, jejunal biopsies from immunocompetent volunteers experimentally challenged with C. parvum were examined by in situ hybridization for interleukin (IL-)15 and IL-4 mRNA with confirmation by immunohistochemistry. Cytokine expression was correlated with prechallenge anti- C. parvum IgG, symptoms, oocyst shedding, and prior IFN-gamma expression data. IL-15 expression was noted only in those without prior sensitization, who did not express IFN-gamma. By contrast, expression of IL-4 was associated with prior sensitization. IL-15 was only detected in those with symptoms (6/14 symptomatic vs 0/3 asymptomatic, P<0.05). Among 14 volunteers who did not express IFN-gamma, oocyst shedding was lower in those expressing IL-15. Overall, 14/15 volunteers who did not shed oocysts expressed either IFN-gamma or IL-15. There was no correlation between expression of IL-4 and symptoms or oocyst shedding. In conclusion, IL-15 expression was associated with control of oocyst shedding in those not expressing IFN-gamma. These data suggest that IL-15 is involved in IFN-gamma independent mechanisms of control of human cryptosporidiosis, perhaps via activation of the innate immune response.

Standardized method of measuring acanthamoeba antibodies in sera from healthy human subjects

Acanthamoeba species can cause serious, debilitating, and sometimes life-threatening infections. Three groups have been identified using morphological and immunological comparisons. Previous serological studies have utilized a variety of antigen preparations and assay methods and reported disparate (3 to 100%) results. This study was designed to (i) optimize an enzyme-linked immunosorbent assay for detecting serum antibodies to each of the Acanthamoeba serogroups and (ii) test 55 healthy individuals for specific immunoglobulin G reactivity. The highest signal-to-background ratio was found when 3,000 fixed, intact trophozoites per well were used with a 1:10 serum dilution. Sera yielding optical densities of <0.25 against all three Acanthamoeba serogroups were used to define the cutoff for positive results. The highest background reactivity with these sera was seen with Acanthamoeba polyphaga (serogroup 2), followed by Acanthamoeba culbertsoni (serogroup 3) and Acanthamoeba astronyxis (serogroup 1). Of 55 subjects tested, the highest number of positive results was seen with A. polyphaga (81.8%), followed by A. astronyxis (52.8%) and A. culbertsoni (40%). Seven serum samples (12.7%) were negative for all three Acanthamoeba serogroups, 16 (29.1%) were positive for one serogroup only, 16 were positive for two serogroups, and 16 reacted to all three serogroups. Further analysis showed no significant associations between serogroup reactivity and age or gender. However, some ethnic differences were noted, especially with A. polyphaga antigens. In that case, serum samples from Hispanic subjects were 14.5 times less likely to be positive (P = 0.0025) and had lower mean absorbance values (P = 0.047) than those from Caucasian subjects. Overall, these data suggest that Acanthamoeba colonization or infection is more common than previously thought. Mild or asymptomatic infections may contribute to the observed serum reactivities.

Expression of tumor necrosis factor alpha and interleukin 1 beta in jejuna of volunteers after experimental challenge with Cryptosporidium parvum correlates with exposure but not with symptoms

Jejunal biopsies from volunteers challenged with Cryptosporidium parvum were examined for tumor necrosis factor alpha (TNF-alpha) and interleukin (IL)-1 beta mRNA. Postchallenge biopsies from 15 of 28 (54%) volunteers expressed TNF-alpha; 14% expressed IL-1 beta. Cytokine expression did not correlate with enteric symptoms, suggesting that TNF-alpha and IL-1 beta are not key mediators of diarrhea in human cryptosporidiosis.

Fecal antibodies to Cryptosporidium parvum in healthy volunteers

This study examined the intestinal antibody response in 26 healthy volunteers challenged with Cryptosporidium parvum oocysts. Fecal extracts were assayed for total secretory immunoglobulin A (IgA) and C. parvum-specific IgA reactivity. Specific IgA reactivity was standardized to IgA concentration and expressed as a reactivity index (RI). Anti-C. parvum fecal IgA (fIgA) increased significantly in 17 of 26 (65.4%) following oocyst ingestion. Of those with detectable responses, 59, 76.5, and 94.1% were positive by days 7, 14, and 30, respectively. Volunteers receiving high challenge doses (>1,000 and 300 to 500 oocysts) had higher RIs (RI = 5.57 [P = 0. 027] and RI = 1.68 [P = 0.039], respectively) than those ingesting low doses (30 to 100 oocysts; RI = 0.146). Subjects shedding oocysts and experiencing a diarrheal illness had the highest fIgA reactivity. When evaluated separately, oocyst excretion was associated with an increased fIgA response compared to nonshedders (RI = 1.679 versus 0. 024, respectively; P = 0.003). However, in subjects experiencing diarrhea with or without oocyst shedding, a trend toward a higher RI (P = 0.065) was seen. Extracts positive for fecal IgA were further examined for IgA subclass. The majority of stools contained both IgA1 and IgA2, and the relative proportions did not change following challenge. Also, no C. parvum-specific IgM or IgG was detected in fecal extracts. Thus, fecal IgA to C. parvum antigens was highly associated with infection in subjects who had no evidence of previous exposure and may provide a useful tool in detecting recent infections.

Transforming growth factor beta1 is expressed in the jejunum after experimental Cryptosporidium parvum infection in humans

Biopsies from volunteers challenged with Cryptosporidium parvum were examined for transforming growth factor beta1 (TGF-beta1). None of the prechallenge biopsies exhibited TGF-beta. Seven of 12 volunteers with oocyst shedding expressed TGF-beta versus 2 of 13 volunteers without detected oocysts. The association of TGF-beta expression with oocyst excretion and the timing of symptoms suggests that TGF-beta mediates intestinal healing.

Interferon-gamma expression in jejunal biopsies in experimental human cryptosporidiosis correlates with prior sensitization and control of oocyst excretion

To investigate the role of interferon (IFN)-gamma in human cryptosporidiosis, jejunal biopsies from experimentally infected volunteers and chronically infected AIDS patients were examined for IFN-gamma expression by in situ hybridization. IFN-gamma expression was compared with oocyst excretion, baseline serum anti-Cryptosporidium antibody, and symptoms. IFN-gamma mRNA was detected in biopsies from 13 of 26 volunteers after experimental infection but not in biopsies taken before C. parvum exposure or in biopsies from patients with AIDS-associated cryptosporidiosis. After challenge, 9 of 10 volunteers with baseline C. parvum antibody produced IFN-gamma, compared with 4 of 16 volunteers without baseline antibody (P<.01). Furthermore, IFN-gamma mRNA was detected in 9 of 13 volunteers who did not excrete oocysts, compared with 4 of 13 with organisms (P<.05). Thus, expression of IFN-gamma in the jejunum was associated with prior sensitization and absence of oocyst shedding. IFN-gamma production may explain the resistance to infection noted in sensitized persons but may not be involved in control of human primary infection.

Virulence of three distinct Cryptosporidium parvum isolates for healthy adults

The infectivity of three Cryptosporidium parvum isolates (Iowa [calf], UCP [calf], and TAMU [horse]) of the C genotype was investigated in healthy adults. After exposure, volunteers recorded the number and form of stools passed and symptoms experienced. Oocyst excretion was assessed by immunofluorescence. The ID50 differed among isolates: Iowa, 87 (SE, 19; 95% confidence interval [CI], 48.67-126); UCP, 1042 (SE, 1000; 95% CI, 0-3004); and TAMU, 9 oocysts (SE, 2.34; 95% CI, 4.46-13.65); TAMU versus Iowa, P=.002 or UCP, P=.019. Isolates also differed significantly (P=.045) in attack rate between TAMU (86%) and Iowa (52%) or UCP (59%). A trend toward a longer duration of diarrhea was seen for the TAMU (94.5 h) versus UCP (81.6 h) and Iowa (64.2 h) isolates. C. parvum isolates of the C genotype differ in their infectivity for humans.

Infectivity of Cryptosporidium parvum in healthy adults with pre-existing anti-C. parvum serum immunoglobulin G

A 50% infectious dose (ID50) of 132 Cryptosporidium parvum oocysts was previously determined in serologically negative individuals (ELISA). In this study, 17 healthy adults with pre-existing anti-C. parvum serum IgG were challenged with 500-50,000 oocysts. Infection and diarrhea were associated with the higher challenge doses. The ID50 was 1,880 oocysts, > 20-fold higher than in seronegative volunteers. Fecal oocysts were detected in only seven (53.8%) of 13 individuals with clinical cryptosporidiosis, indicating that the host response may effectively decrease the number of oocysts produced. Subjects with the highest absorbances prior to challenge had little to no increase in IgG following challenge, whereas volunteers with lower reactivities showed significant postchallenge increases. This suggests that an upper limit of serum IgG was present in some subjects, while others were further stimulated by an additional exposure. These data indicate that prior exposure to C. parvum provides protection from infection and illness at low oocyst doses.

Sequence polymorphism in the beta-tubulin gene reveals heterogeneous and variable population structures in Cryptosporidium parvum

Restriction fragment length polymorphism (RFLP) analysis of isolates of Cryptosporidium parvum has revealed two subgroups, termed H and C. The limited resolution of the RFLP method precludes an in-depth study of the genetic structure of C. parvum populations. Published C. parvum restriction polymorphisms lie within protein-coding regions known to be more homogeneous than noncoding sequences. To better assess the degrees of heterogeneity between and within C. parvum isolates, sequence polymorphism in the beta-tubulin intron, the only C. parvum intron described to date, was investigated. In contrast to the two genotypes distinguished by multilocus RFLP, several alleles were detected by sequence and RFLP analysis of the beta-tubulin intron and adjacent exon 2. Isolates carrying different beta-tubulin alleles were found. Significantly, one of the beta-tubulin alleles present in two geographically unrelated isolates combined features of C- and H-type isolates, suggesting that it might have arisen from a recombination event. A comparison of multiple samples of a calf-propagated laboratory isolate showed that the ratio of different beta-tubulin alleles fluctuated during serial passage.

The antibody response to 27-, 17-, and 15-kDa Cryptosporidium antigens following experimental infection in humans

Previous studies have suggested that persons infected with Cryptosporidium parvum develop antibody responses to 27-, 17-, and 15-kDa C. parvum antigens. Studies of volunteers infected with Cryptosporidium species provided an opportunity to evaluate the relationship between antibody reactivity to these antigens and infection outcome. As monitored by immunoblot, increases in specific antibody reactivity were more prevalent among volunteers who developed signs and symptoms of cryptosporidiosis (n = 11) than among asymptomatic infected (n = 7; P = .05) or oocyst-negative volunteers (n = 11; P = .02). Volunteers with preexisting IgG antibody to the 27-kDa antigen excreted fewer oocysts than volunteers without this antibody (P = .003). IgG reactivity to the 17-kDa antigens and IgM reactivity to the 27-kDa antigens were higher at day 0 for asymptomatic infected persons than for those who developed symptoms (P = .03 and P = .04, respectively). These results suggest that characteristic antibody responses develop following C. parvum infection and that persons with preexisting antibodies may be less likely to develop illness.

Combination drug therapy for cryptosporidiosis in AIDS

Aside from effective antiretroviral therapy, there is no consistently effective antiparasitic therapy for cryptosporidiosis in AIDS. The purpose of this study was to assess safety, efficacy, and durability of combination therapy with paromomycin and azithromycin for chronic cryptosporidiosis. Patients with AIDS, chronic cryptosporidiosis, and < 100 CD4 cells/microL were treated with open-label paromomycin (1.0 g twice a day) plus azithromycin (600 mg once a day) for 4 weeks, followed by paromomycin alone for 8 weeks. In 11 patients, median stool frequency decreased from 6.5/day (baseline) to 4.9/day (week 4) and 3.0/day (week 12). Median reductions in 24-h oocyst excretion were 84%, 95%, and >99% at 2, 4, and 12 weeks, respectively. None of the responses were attributable to antiretrovirals. Of 5 survivors at 12-30 months of follow-up, 3 remain asymptomatic off medications, and 2 have chronic, mild diarrhea. Treatment of cryptosporidiosis with azithromycin and paromomycin was associated with significant reduction in oocyst excretion and some clinical improvement.

Prophylactic effect of bovine anti-Cryptosporidium hyperimmune colostrum immunoglobulin in healthy volunteers challenged with Cryptosporidium parvum

Bovine hyperimmune anti-Cryptosporidium colostrum immunoglobulin (BACI) decreases the intensity of Cryptosporidium parvum infection in vitro. We investigated the prophylactic effect of BACI in healthy adults challenged with C. parvum. After we established an oocyst dose that resulted in 100% infection in four volunteers (baseline group), 16 volunteers were randomized to receive (1) BACI prior to C. parvum challenge (BACI group) and a nonfat milk placebo 30 minutes later, (2) BACI prior to and 30 minutes after challenge (reinforced BACI group), or (3) nonfat milk placebo prior to and 30 minutes after challenge. Subjects received BACI (10 g) or nonfat milk placebo three times a day for a total of 5 days and were followed for clinical symptoms and oocyst excretion for 30 days. A trend toward less diarrhea (P = .08) was observed for subjects receiving BACI in comparison with occurrences in placebo recipients. Subjects receiving BACI or nonfat milk placebo had a 100-fold reduction in oocyst excretion as compared with excretion in the baseline group.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

Coenuriasis in a spectacled langur (Presbytis obscura): praziquantel treatment and the antibody response to cyst antigens

A diagnosis of coenuriasis was made in a spectacled langur raised in captivity. Multiple cysts removed from the subcutaneous tissues and later from the abdominal cavity were identified as coenuri, typical of the genus Taenia. Post-surgical treatment of the remaining cysts with praziquantel was assessed with whole body computerized tomography (CT). CT at 6 weeks post-treatment revealed a reduction in size and increased calcification of abdominal cysts as compared to pretreatment CT. Cyst fluid antigens in ELISA assays showed a high titer (1:5, 120) IgG response in the langur serum, while no IgM response could be detected. No decrease in IgG titer was seen 6 weeks after treatment. Immunoblot analyses identified several parasite-specific antigens with apparent molecular weights of greater than 92.5 (3 bands), 88, 41, 37, and 34 kDa.

Cloned Schistosoma mansoni proteinase (hemoglobinase) as a putative serodiagnostic reagent

Expressed cDNA encoding a proteolytic enzyme from Schistosoma mansoni has been cloned recently. Circulating antibodies reacting with the recombinant protein have been detected in the blood of mice and humans infected with S. mansoni, S. japonicum, or S. haematobium. S. mansoni and S. haematobium infection can be distinguished by antibody titer.

Schistosoma mansoni: expression and role of cysteine proteinases in developing schistosomula

The adult stage of Schistosoma mansoni utilizes host hemoglobin as a nutrient source. A proteolytic enzyme (SMw32) that has "hemoglobinase" activity is secreted into the parasite gut where it appears to be rapidly activated by glutathione released from host red blood cells. In the present study the expression of this proteinase, in developing schistosomula, has been correlated with digestive tract development and a dramatic rise in enzyme activity as early as Days 8-10 of culture. No evidence of the SMw32 proteinase was found in eggs, cercariae, or in newly transformed larvae. Further, the proteinase expressed at Days 8-10 is indistinguishable from the adult worm enzyme. In the larvae, indirect immunofluorescence with an anti-SMw32 monoclonal antibody showed that the proteinase is found throughout the developing cecum. The importance of cysteine proteinases to parasite development was also studied using a specific enzyme inhibitor, Ep-459. In cultures containing Ep-459 most (75%) of the schistosomula failed to survive the 18-day study period. Moreover, those that did survive showed a decrease in their growth (body length). These data suggest that the SMw32 proteinase is a developmentally regulated enzyme and that cysteine proteinase activity is essential in providing nutrients for the growth and survival of this parasite in its mammalian host. Thus, this proteinase may be an important target for chemotherapeutic intervention.

The hypersensitivity response to the adult worm proteinase, SMw32, in Schistosoma mansoni infected mice

A cysteine proteinase (SMw32) from the digestive tract of an adult Schistosoma mansoni worm has previously been purified and characterized. During the course of infection with this parasite, a strong immune response to the enzyme occurs. We now have confirmed the presence of anti-proteinase IgE and IgG in S. mansoni infected mice and have investigated the in vivo cellular response to proteinase in infected and uninfected mice. Immediate and delayed type hypersensitivities were detected in uninfected mice sensitized by multiple injections of proteinase. In S. mansoni infected mice, immediate hypersensitivity reactions were seen at 6 and 8 weeks following infection, coincident with the increase in anti-proteinase IgE antibody. Histological sections of the injection site confirmed the presence of degranulating mast cells. In contrast, delayed type hypersensitivity could not be detected at any time during the course of the infection. In the murine model of acute infection, immediate hypersensitivity to the SMw32 proteinase was predictive of infection.

Antibody response to a purified parasite proteinase (SMw32) in Schistosoma mansoni infected mice

Indirect immunofluorescence of Schistosoma mansoni adult worm sections has revealed that the early immunoglobulin response is directed toward the parasite digestive tract. One of the components of the worm gut is a cysteine proteinase which degrades host hemoglobin ingested by the parasite. In this report the purified proteinase (SMw32) was used in ELISA and immunoblot analyses to study the specific antibody response during the course of an acute infection. We have found high titer IgG antibody in S. mansoni infected, but not uninfected, mice. The anti-proteinase response involves IgM, IgG1, IgG2a, and IgE isotypes. Total IgM and IgG levels increased by week 3 post-infection and remained elevated throughout the study (7 weeks). Increased titers (IgM, IgG) of specific anti-proteinase were also apparent by week 3 post-infection, long before fecal eggs were detectable. Mean anti-proteinase IgG stabilized at high titer by week 5 post-infection, while IgM titers decreased to near background levels. Anti-proteinase IgE was first detectable at week 4 and reached peak titers by weeks 6 and 7. The strong antibody response to the purified SMw32 proteinase is consistent with the early reactivity of S. mansoni infected mice and humans to a 31 kDa component of the worm gut described by others.

Schistosoma mansoni: anti-SMw32 proteinase response in vaccinated and challenged baboons

Antibodies to a cysteinyl proteinase of the trematode Schistosoma mansoni have been detected in serum from infected mice and humans. We have evaluated antiproteinase responses in infected baboons and in baboons vaccinated with irradiated, cryopreserved schistosomules prior to challenge. Prechallenge sera and normal, uninfected control sera were nonreactive by ELISA and immunoblots. Serum antibodies were first detectable by ELISA at two months post-challenge in both challenged (C) and vaccinated-challenged (V-C) baboons (serum dilution 1:200). By four months post-challenge, ELISA absorbance values for subgroup C baboons were significantly higher than for V-C counterparts. The immunoblot technique provided a more sensitive means of detecting antibody early in the infection. One month post-challenge, 7 of 12 C and V-C sera (diluted 1:100) contained measurable anti-proteinase antibody. By month two, 12 of 12 were immunoblot-positive. Baboons vaccinated but not challenged (subgroup V) remained negative. The presence of the anti-proteinase antibody appears to be a sensitive and early marker for infection by S. mansoni.

Purification of cysteine proteinases from adult Schistosoma mansoni

Proteolytic activity against hemoglobin and low molecular weight synthetic substrates has been previously found in homogenates and excretion/secretion products of adult Schistosoma mansoni worms. This activity is stimulated in the presence of thiol compounds and is maximally active at acidic pH. To characterize further this proteolytic activity, lyophilized adult worms were extracted, and proteinases were isolated and purified. From extracts prepared in 0.2 M citrate buffer, pH 4.9, two proteinase species were purified to homogeneity by centrifugation, gel filtration, dialysis, and chromatofocusing chromatography. The proteinases, designated SMw32 and SMw28, have apparent molecular weights (SDS-PAGE) of 31,700 +/- 1400 and 27,800 +/- 1700, respectively. Both are thiol-dependent, acidic endopeptidases that cleave hemoglobin and a synthetic substrate, CBZ-arg-arg-AFC. A statistical comparison of amino acid compositions reveals that the proteinases are highly related.

Glutathione activation of a cysteine proteinase from Schistosoma mansoni

A cysteine proteinase isolated from Schistosoma mansoni adults requires reduction by thiols for activation. The proteinase is located in the parasite digestive tract where it degrades hemoglobin released from host red blood cells. Reduced glutathione (GSH) has been shown to be effective in activation. Total glutathione concentration and the GSH/oxidized glutathione (GSSG) ratio were measured in whole blood lysate (3.2 mM, 284), serum (24 microM, 9.8) and material collected from the parasite digestive tract (4.2 mM, 137). The ratio of GSH/GSSG at which the enzyme displays half-maximal activity (Kox) is 1.0. Proteinase activation as a function of glutathione concentration and time was determined. The first-order reaction yielded a half-time of activation of 13 min at 5 mM. The second-order rate constant was 12.7 M-1 X min-1. The function of the proteinase and its possible regulation by glutathione activation are discussed.

Schistosoma mansoni: proteinase activity of "hemoglobinase" from the digestive tract of adult worms

A method of collecting samples from the Schistosoma mansoni digestive tract was used to study proteinase activity. Activity against hemoglobin and a low molecular weight synthetic substrate, carbobenzoxy-arginyl-arginyl-7-amino-4-trifluoromethylcoumarin, was demonstrated in the soluble fraction of material regurgitated by S. mansoni adults and was dependent on the addition of a thiol compound, cysteine, to the assays. Using sodium dodecyl sulfate-polyacrylamide gel electrophoresis and gel filtration chromatography (AcA54), two proteins with estimated mol wt of 32,500 and 28,500 were found in the regurgitant and were associated with proteinase activity against both hemoglobin and the synthetic substrate. Homogenates of intact worms showed greater specific activity (synthetic substrate) in the females. Further, in bisected worms proteinase activity paralleled protein content, suggesting that, once secreted into the lumen, proteinase activity was distributed throughout the worm digestive tract.

Properties of the acid thiol proteinase from Schistosoma mansoni adults

Seven beta-naphthylamine-linked peptides were tested as substrates for a previously described thiol proteinase of adult Schistosoma mansoni. The enzyme was not active on carbobenoxy-arginyl-arginyl-4-methoxy-2-naphthylamide and carbobenzoxy-alanyl-arginyl-arginyl-4-methoxy-2-naphthylamide. Enzyme activity was maximal at acidic pH (4.9-5.5) with similar optima for both macromolecular and peptide substrates. Activity of partially purified enzyme preparations against carbobenzoxy-arginyl-arginyl-4-methoxy-2-naphthylamide was stimulated more than 10-fold by thiols. The properties of this proteinase differ from those of proteolytic enzymes from the cercariae ad eggs of S. mansoni.

Pili of Neisseria meningitidis: effect of media on maintenance of piliation, characteristics of Pili, and colonial morphology

In contrast to information in the literature which indicates that meningococci rapidly lose pili upon cultivation in vitro, we found that piliation of meningococci could be maintained in vitro for 15 or more passages. Pili were present on all eight isolates tested, whether from asymptomatic carriers or from subjects with meningococcal disease. Complete loss of piliation occurred in the same two strains on two of the three media tested. On one medium (Thayer-Martin medium with supplement B), there was partial or complete loss of pili by all strains. The optimal medium for maintaining pili was chocolate agar with 1% IsoVitaleX; 95% or more of the microorganisms of six of the eight strains tested were piliated after 15 passages in vitro, and more than 60% of the microorganisms of the other two strains were piliated. Meningococci passed on this medium generally maintained their initial density of piliation (3 to 34 pili per diplococcus). The ability to predictably cultivate piliated meningococci in vitro and to select piliated and nonpiliated clones of the same strain should allow investigation of the biochemical and immunological properties of meningococcal pili as well as their possible role in the pathogenicity of Neisseria meningitidis.