The Journal of protozoology最新文献

Human antibody response to Cryptosporidium parvum has been previously shown as involving immunoglobulin (Ig)M and IgG isotypes. The interest in anti-cryptosporidial IgA antibody response has been recently stimulated by studies on the therapeutic effects of secretory IgA antibodies to Cryptosporidium in animal models and in patients. In the present study, isotypes of serum anti-Cryptosporidium antibodies have been characterized in donors of the following categories: (a) healthy adults, (b) healthy children, (c) immunocompetent children with transient cryptosporidial diarrhea, (d) HIV-infected patients without clinical and parasitological evidence of Cryptosporidium infection and (e) AIDS patients with cryptosporidial diarrhea. Antibodies were detected using C. parvum oocysts purified by density gradient centrifugation from bovine faeces. The IgA antibodies were revealed using alpha-chain specific antibodies. Indirect immunofluorescence analysis with oocysts was used as control. Although high levels of serum antibodies of the IgA class were detected in some donors in the group of healthy adults, elevated values were consistently found in HIV-infected patients. Higher values were found in HIV patients with clinical cryptosporidiosis. The presence of a secretory component in serum IgA antibodies in these patients has been documented. Data indicate that IgA serum antibodies are produced as well as IgM and IgG antibodies upon contact with the parasite, and suggest that elevated IgA serum antibodies to Cryptosporidium are not associated with protection in HIV patients.

Sporozoites and merozoites of Cryptosporidium parvum were analyzed for the presence of a 15 kDa surface antigen using a monoclonal antibody probe. Both were found to possess the antigen by immunofluorescence, and further analysis by sodium dodecyl sulfate-polyacrylamide gel electrophoresis confirmed these observations. When separated by two-dimensional electrophoresis the isoelectric point was found to be similar, with major spots at 4.25 and minor spots at 4.15.

A compromised immune system is the primary predisposing condition for Pneumocystis infection. Factors that contribute to this underlying state of immunosuppression are poorly understood. The presence of common rodent viruses and the role of anti-Pneumocystis antibodies on the progression of natural infection in the corticosteroid-treated rat model of Pneumocystis pneumonia were evaluated. The development and intensity of infection were not affected by the presence or absence of antibodies to these viruses or to major Pneumocystis antigens. A significant increase in survival of Pneumocystis-infected viral antibody-positive rats was observed when these rats were housed under barrier conditions.

Enterocytozoon bieneusi was first described by electron microscopy in 1985 in intestinal biopsies from an AIDS patient. It has subsequently been observed in many AIDS patients with chronic diarrhea from the U.S.A., Africa, and Europe. Morphologically, this parasite meets the criteria for being a microsporidian but has unique features justifying the creation of a a new genus and family. It has organelles not seen in microsporida before, i.e. elongated nuclei, electron-lucent inclusions, electron-dense discs, and development of multiple polar tubules in a single cell prior to the final cytokinetic process producing many sporoblasts. However, it produces typical microsporidian spores. Recently, a second type of microsporidian has been observed in similar biopsies from an AIDS patient which resembles an Encephalitozoon except that it secretes a fine network of material in which the developing organisms become embedded. During sporogony, each cell appears to be in a separate chamber. These two parasites are morphologically and pathologically compared.

Use of monoclonal antibodies against the major glycoprotein of Pneumocystis carinii (P115) implicated the sugar moiety as being strongly antigenic. Furthermore, monoclonal antibodies directed against the peptide portion of P115 were generated by using synthetic oligopeptides after amino acid sequencing was done on P115 proteolytic fragments.

Spontaneous Pneumocystis carinii infections occur in piglets. In this report we describe the symptoms, pathology and predisposing conditions of P. carinii pneumonia in the pig. We also discuss the advantages and disadvantages of the pig as an experimental system to study P. carinii pneumonia.

To facilitate studies of the biology of Cryptosporidium parvum, we have developed an in vitro culture system using Madin-Darby canine kidney (MDCK) cells as the host cell. Oocysts or free sporozoites were incubated 37 degrees C with monolayers of MDCK cells in supplemented RPMI 1640 medium and the cells were examined at various time intervals after initiation of the culture. High rates of infection (up to 90% of MDCK cells) were achievable. Sequential development of trophozoites, meronts, microgametocytes, and macrogametocytes was observed over a 72-h period of culture. Between 72 and 96 h we observed formation of oocyst walls, but fully sporulated oocysts were not observed. This culture system provides access to both the asexual and sexual intracellular stages of C. parvum.

The cations Ca2+ and K+ and the anions Cl-, HCO3-, and PO4- were studied for their contribution to metacyclic trypomastigote formation of Trypanosoma cruzi in starvation media consisting of phosphate-buffered saline (PBS) + 10 mM proline + 10 mM sodium acetate as well as one of the following salts: 0.035% NaHCO3 (PBSNPA), 0.035% K2CO3 (PBSKPA) or 0.035% K2HPO4 (PBSPPA). Isolates CL and DM28c were activated to transform with 5% CO2 and the percent metacyclogenesis determined after incubation for 96 h in PBS starvation media. Maximal metacyclogenesis was found with CaCl2 and KCl. In the presence of K+, the percent transformation was highest with the phosphate salt, followed by the carbonate and the chloride salts. Cells incubated in PBSNPA and the cationic ionophores A23187 (5 x 10(-6) M), lasalocid (5 x 10(-6) M), and valinomycin (10(-8) M) do not survive; addition of 2 mM CaCl2 or 17 mM KCl to DM28c cells, reversed the lethal action of the ionophores permitting differentiation into metacyclic forms. The addition of CaCl2 to CL cells incubated in ionophores abrogated the lethal effect of the ionophores but transformation was significantly different than in control preparations. Adding KCl to ionophore incubated cells resulted in normal levels of transformation except in the case of valinomycin. DM28c and CL cells incubated in PBSKPA show significantly greater metacyclogenesis in the presence of 5 mM EGTA. These results indicate that exogenous concentrations of several cations and anions significantly influence T. cruzi metacyclogenesis and that the degree of response by the parasite to free ion levels may be strain dependent.

Alveolar macrophages are thought to participate in clearing Pneumocystis carinii (Pc) from the lungs. We have recently demonstrated that Pc cysts and trophozoites induce an oxidative burst in a cell line of rat alveolar macrophages (NR8383). In order to investigate the mechanism of this response, we examined the effect that disruption of the Pc cyst wall with zymolyase had on the cyst's ability to elicit H2O2 from NR8383 macrophages and correlated these results with the electron microscopic appearance of the cyst wall.

Pneumocystis carinii cells labeled with fluorescein isothiocyanate were co-cultured with tissue culture cells. Measurements of attachment was determined by the tissue culture cell fluorescence after washing out the P. carinii organisms. The effects of the extracellular matrix proteins, laminin and fibronectin, on the binding of P. carinii onto the monolayer of cultured cells were investigated for better understanding of organism-cell interactions. The internalization of P. carinii by MRC5 cells was observed.