The Journal of protozoology最新文献

Placental transmission of Pneumocystis carinii in mice was examined in 39 animals obtained by caesarean section from 17 pregnant SCID females experimentally infected with P. carinii. When examined with toluidine blue O, DAPI and immunofluorescent antibody stains, P. carinii was detected in the lungs of infected mothers but not in the lungs of caesarean section-derived neonates even after the neonates were treated with dexamethasone for 8 weeks. However, 13 neonates born to five infected females developed P. carinii pneumonia. These results indicate that P. carinii cannot be transmitted transplacentally in mice.

Resistance to Pneumocystis carinii infection appears to be mediated by T lymphocytes but the mechanism and subsets of T cells involved are poorly understood. We used the BALB/c mouse model to study the delayed-type hypersensitivity (DTH) response to rat P. carinii. Mice were sensitized to P. carinii for seven days and then challenged with P. carinii antigens in the right rear footpads and normal rat lung antigens in the left rear footpads. A typical DTH response was observed in the right footpads as evidenced by significant swelling and substantial mononuclear cell infiltration at 24-h post-challenge. The DTH response could be transferred to naive syngeneic mice by adoptively transferring spleen cells from P. carinii-sensitized mice. In addition, by using anti-thy-1, anti-mouse Ig, anti-L3T4 and anti-Lyt-2.2 monoclonal antibodies in in vitro cytolysis experiments, we were able to demonstrate that the DTH response was dependent upon T lymphocytes. The response appeared to require cooperation between both L3T4+ and Lyt 2+ subsets of T lymphocytes.

Three acidic proteins (42 kD, 43 kD and 50 kD) were present in unusually high concentrations in cortical preparations of the Tetrahymena pattern mutant broadened cortical domains (bcd). Antisera to the 42-kD and 50-kD proteins bound to discharging mucocysts and food vacuole contents in both wild-type and mutant cells. Subsequent analysis revealed that bcd mutant cell pellicles possess five times more "docked" mucocysts than their wild-type counterparts.

Cryptosporidium-specific circulating antigens were detected in sera of experimentally infected calves and AIDS patients by an enzyme-linked immunosorbent assay. Antigenemia was detectable from 2 to a minimum of 22 days post-infection (d.p.i.) in calves whose feces were parasitologically positive from 2-10 d.p.i. Antigenemia was detected in AIDS patients showing no a sero-conversion to immunoglobulin (Ig) M or to IgG. The detection of circulating antigens in humans allows early diagnosis of cryptosporidiosis, even in immunosuppressed patients.

Pathologic and clinicopathologic changes were examined in broiler chickens inoculated with Cryptosporidium baileyi (Cb) alone or in combination with infectious bronchitis virus (IBV), infectious bursal disease virus (IBDV) or Escherichia coli (Ec). Concurrent infections with Cb and either IBV or Ec resulted in a greater respiratory inflammatory response than either agent given alone. Concurrent Cb, IBV or Ec infections resulted in a decreased density of respiratory cryptosporidial stages. No interactions between Cb and IBDV were observed. Clinicopathologic results in broiler chicks exhibiting signs of respiratory cryptosporidiosis indicated that pO2 decreased, pCO2 increased, HCO3 increased and CO2 increased. Changes in blood gases and serum electrolyte values correlated with signs of acute respiratory disease. Blood gases and serum electrolyte values were unchanged in birds with bursal and cloacal infections only. Results of these studies clarified pathogenetic events associated with avian respiratory cryptosporidiosis, and demonstrated that cryptosporidiosis may enhance the severity of respiratory disease caused by other avian pathogens.

Pentamidine and related derivatives inhibit an ATP-dependent topoisomerase activity from Pneumocystis carinii extracts. Since it would be extremely difficult to purify ample quantities of the organisms to allow characterization of the enzyme and carry out drug binding experiments, we have begun the cloning of the topoisomerase genes with a goal towards expression of each gene in a heterologous system. Following construction of genomic libraries in the vectors lambda DASH and lambda ZAP, oligonucleotides corresponding to conserved regions of both topoisomerases I and II were used in the polymerase chain reaction (PCR) of P. carinii DNA to generate probes. Candidate clones for both genes have been identified. Partial DNA sequence of the topoisomerase II gene has been determined.

An analogue of pentamidine, 1,3-di(4-imidazolino-2-methoxyphenoxy)propane (DMP) lactate, was tested against rat Pneumocystis carinii pneumonia (PCP). The drug was found to be highly active in the treatment of rat PCP at a dose of 1.75 mg/kg (parent molecule) when administered by intravenous (i.v.) injection (daily for 2 wk). The compound was also active against PCP when given orally, however, significantly higher doses of DMP were necessary when compared to the i.v. dosing regimen. Prophylactic doses (i.v.) of the drug also proved highly effective in preventing PCP.

The attachment site of Cryptosporidium muris to host cells was investigated using the freeze-fracture method. Cryptosporidium muris was enveloped by a double membrane of host plasma membrane origin, which formed the parasitophorous vacuole. The outer membrane of the double membrane was continuous with the host plasma membrane at the dense band, while the inner membrane was connected with the anterior part of the parasite plasma membrane at the annular ring. The density of intramembranous particles (IMP) was dramatically altered at the above two junctures. The outer parasitophorous membrane showed low IMP-density as compared to the host plasma membrane, although both membranes were continuous. The inner parasitophorous membrane had few IMP, whereas the parasite plasma membrane showed numerous IMP. When the attachment sites of parasites and host cells were fractured, circular-shaped fractured faces were observed on both sites of the parasite and host cell. These exposed faces corresponded to the dense bands and were very similar in size in each parasite.

Ultrastructural studies of the attachment zone between Pneumocystis carinii (Pc) and type I alveolar epithelial cells showed a new aspect of the host-parasite relationship, i.e. an activation of the plasmalemmal vesicular system in the alveolar cells associated with Pc trophozoites in close apposition. This phenomenon may be involved in the nutrition of the trophozoite.

The polymerase chain reaction technique was used to detect Pneumocystis carinii by amplifying the P. carinii 5S ribosomal DNA. The efficacy and specificity of this diagnostic method is reported. Analysis of patients' sputa indicate that the method can be used on these samples for the diagnosis of P. carinii pneumonia.