Immunochemical studies of Toxocara canis proteases.

Proteases of nematodes play a crucial role in larval molting and, in addition to their active role in egg hatching, proteases are also considered a crucial factor in tissue invasion and connective tissue remodeling. In Toxocara canis, proteases play important roles throughout the complex life cycle. They can degrade components of a model of extracellular matrix, basement membranes and different physiological substrates. In the present study, measurements of the proteolytic activity of the perivitelline fluid (PF) surrounding Toxocara canis embryos at different stages of development, the hatching fluid (HF) surrounding the infective larvae, as well as the excretory secretory (ES) products of the larvae in the culture media were performed. Measurements were made using casein as substrate following the Sigma non-specific protease activity assay. The results showed that enzyme activity increased as the embryo matured. The infective larvae were found to continuously produce proteases in the surrounding HF and ES products after in vitro cultivation indicating that Toxocara canis proteases might be important for the worm in the egg and the host. Optimal enzymatic activity was found at pH 8. Incubation of the antiserum from infected mice with the HF and ES products decreased their proteolytic activities, suggesting that there may be a link between the proteases present in these fluids and the immune response.

Immunochemical studies of Toxocara canis proteases

@#Proteases of nematodes play a crucial role in larval molting and, in addition to their active role in egg hatching, proteases are also considered a crucial factor in tissue invasion and connective tissue remodeling. In Toxocara canis, proteases play important roles throughout the complex life cycle. They can degrade components of a model of extracellular matrix, basement membranes and different physiological substrates. In the present study, measurements of the proteolytic activity of the perivitelline fluid (PF) surrounding Toxocara canis embryos at different stages of development, the hatching fluid (HF) surrounding the infective larvae, as well as the excretory secretory (ES) products of the larvae in the culture media were performed. Measurements were made using casein as substrate following the Sigma non-specific protease activity assay. The results showed that enzyme activity increased as the embryo matured. The infective larvae were found to continuously produce proteases in the surrounding HF and ES products after in vitro cultivation indicating that Toxocara canis proteases might be important for the worm in the egg and the host. Optimal enzymatic activity was found at pH 8. Incubation of the antiserum from infected mice with the HF and ES products decreased their proteolytic activities, suggesting that there may be a link between the proteases present in these fluids and the immune response.

Experimental amoebic liver abcess produced by oral administration of Entamoeba histolytica cysts.

To determine the possibility of amoebic invasion and liver-abscess formation Swiss albino mice were infected orally with E. histolytica cysts isolated from human stools. Parasitological and histopathological changes in mice colon and liver tissues were sequentially followed. Three weeks postinfection (p.i) 5% of immunocompetent and all cortisonized immunosuppressed mice passed the parasite in their stools. Only 70% of the latter group of mice sacrificed at that time developed invasive intestinal amoebiasis. At the end of the experiment (12 weeks p.i.) 100% of the remaining immunosuppressed animals developed the same intestinal pathology. Amoebic liver abscess was detected in 62.5% of them. Oral inoculation of E. histolytica cysts constitutes an easy highly reproducible procedure for inducing liver abscess in immunosuppressed mice.

Serum IgG antibody response to Pneumocystis carinii among immunosuppressed, malnourished and healthy rats.

Pneumocystis carinii is an important opportunistic pulmonary pathogen that causing pneumonia in premature infants, children with immunodeficiency diseases and patients of all ages receiving immunosuppressive agents. In this work, humoral immune responses to this organism were studied, using IFAT during the period of infection and recovery of immunosuppressed and malnourished rats compared to healthy group. Where sever pneumonitis similar to that seen in humans can be induced in this experimental model. Serum IgG antibody titers to the organism were absent in rats administered corticosteroids but rose after steroid tapering with disappearance of the organism from their lungs due to reactivation of the immune system. While in malnourished infected rats, clearance of the organism had occurred after regaining the protein diet with progressive increase in IgG level denoting their immunocompetent state. IgG antibody appeared in the serum of control healthy rats with the progress of age at low non diagnostic level indicating the presence of dormant parasites in their lungs.

Opportunistic intestinal protozoa in chronic diarrhoeic immunosuppressed patients.

Chronic diarrhoea accompanied by weight loss is a common and often debilitating problem in immunocompromized patients, receiving chemotherapeutic agents. In these patients, the intestinal opportunistic parasites probably played a major role in causing this clinical manifestation. The present work, aims to search for these parasites. Special stains for each parasite were used to differentiate it easily from the fecal elements, obviating the need for diagnostic invasive techniques especially used in microsporidial infection. The detected parasites were, Giardia lamblia (17.7%) best seen by iron haematoxylin stain. Coccidian oocysts (Cryptosporidia; 13.3% Isospora belli; 2.2%) were clearly seen by using Ziehl-Neelsen and Chromotrope-based stains. The Gram positive spores of Enterocytozoon bieneusi were (4.4%) and best seen by using chromotrope-based stain, where as Giemsa failed in their diagnosis.

Pneumocystis carinii: recognition of the infection in albino rats using different stains.

Pneumocystis carinii is a commensal protozoan which may cause pneumonia in hosts with compromised immune status and may end fatally. Since effective management of pneumocystic pneumonia depends on rapid and accurate recognition of the disease, so, the present study aims to throw lights on the best staining method for cytodiagnosis of this organism with the sequential pathological changes in the infected lungs. An immunosuppression state was induced in albino rats for 6-8 weeks then rats were sacrificed weekly & lungs were examined for infection using different stains. In stained smears, intracystic bodies have been identified using Giemsa, Papanicolaou & Toluidine blue stains. On the other hand, cysts were inspected in paraffin sections using Gomori methenamine silver nitrate (GMS) & weight gram stains. Histopathologically, in sections stained with H & E, features of Pneumocystis carinii pneumonia were obvious, foamy exudation, inflammatory infiltration formed mainly of histiocytes, plasma cells, lymphocytes, thickening of alveolar septa and lastly formation of hyaline membrane in some alveoli.

Effect of Capillaria hepatica infection on Schistosoma mansoni challenge in mice.

The combined infection between Capillaria hepatica and Schistosoma mansoni was studied. The results of this work revealed that C. hepatica infection induced significant reduction of S. mansoni worm load in the two groups infected with C. hepatica and challenged with S. mansoni either during worm maturation period of C. hepatica, or at the time of presence of C. hepatica eggs in the liver Reduction in total and tissue egg count was also reported, but eggs excreted in the stool showed no difference in count from that of S. mansoni-infected controls. Oogram pattern of the experimental groups revealed a higher percentage of dead eggs and absence of mature and some developing stages. Scanning electron microscopy demonstrated severe destruction of adult worm of both groups. All these data showed the vigorous destructive effect of C. hepatica infection on the challenged S. mansoni.

The chemiluminescent response of macrophages in mice infected with Schistosoma mansoni.

Peritoneal phagocytic cells when stimulated by Schistosoma mansoni infection in this study, exhibited a sudden increase in oxygen consumption known as a respiratory burst. This resulted in the production of toxic oxygen metabolites (H2O2 and others). The level of this toxic oxygen metabolites (chemiluminescence/cells) in normal mice and in mice infected with S. mansoni was measured in vitro. One week, one and two months after infection, a highly significant increase in the levels of chemiluminescence/cell was observed when compared to that of the normal control group. These oxygen metabolites have long been known to have microbicidal activity, and may take part in the ecytotoxic role in cell-mediated immune response against all stages of schistosoma life cycle in this study.