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M S Ibrahim

Publications and source records attributed to M S Ibrahim.

At least 37 records · Page 2Linked to original sources
PubMed1992

Anti-Onchocerca volvulus immunoglobulin subclass response in children from Sierra Leone.

The humoral immune responses of a paediatric population of 224 children, 2-15 years of age, residing in an onchocerciasis endemic area of Sierra Leone, were studied to gain information that may be useful in the serodiagnosis of prepatent and low-level infections with Onchocerca volvulus. The antigen-specific levels of IgG and IgG4 were determined and evaluated in the context of the parasitological status of the child. Over 87% of the microfilaria-negative children had significant levels of antigen-specific antibodies against O. volvulus, suggesting that a large percentage of this paediatric population were harbouring prepatent or low-level infections. Over 60% of the children in the group that had detectable numbers of microfilariae in skin snips had elevated levels of O. volvulus-specific IgG4. In contrast, only 23% of the microfilaria-negative children had detectable IgG4 responses. The results presented here indicate that measures of O. volvulus-specific IgG4 may be a useful indicator of the parasitological status of children during the very early stages of onchocerciasis.

Adolescent↗
PubMed1990

Surface-associated antigens of second, third and fourth stage larvae of Dirofilaria immitis.

The surface-associated molecules of the second (L2), third (L3) and fourth (L4) larval stages of Dirofilaria immitis were characterized employing radiolabeling techniques and SDS-PAGE analysis. Major labeled components of 35 kDa and 6 kDa were present in extracts from IODO-GEN-labeled L2 and L3 parasites. The results of lactoperoxidase-catalyzed reactions also demonstrated that L2 and L3 stages of D. immitis have a similar repertoire of surface-associated antigens. However, in contrast to the results obtained with IODO-GEN, lactoperoxidase reactions labeled components with apparent molecular weights of 66, 48, 25, 16.5 and 12 kDa. The similarities in the molecular weights of the L2 and L3 surface-associated components and the results of immunoprecipitation experiments which demonstrated that antibodies produced against the 35 kDa molecule from D. immitis L3s also recognize the 35 kDa component from L2 parasites suggest that synthesis of the molecules found at the surface of mature infective larvae begins as early as day 6 of development in the mosquito, D. immitis L4s emerged from the molting process with a repertoire of surface-associated antigens distinct from those found on L2s and L3s. IODO-GEN labeling of D. immitis L4s showed major surface-associated molecules with apparent molecular weights of 57, 40, 25, 12 and 10 kDa when analyzed under non-reducing conditions. In addition to molecules of 57, 40, 25, 12 and 10 kDa, extracts of D. immitis L4s labeled with lactoperoxidase contained additional major bands at 45, 43 and 8 kDa. Metabolic labeling experiments demonstrated a shift in the amount and complexity of the excretory/secretory products released by D. immitis during L3 to L4 development.

Animals↗
PubMed1989

Antigen shedding from the surface of the infective stage larvae of Dirofilaria immitis.

A qualitative and quantitative analysis was made of the release of surface-associated molecules from developing Dirofilaria immitis infective-stage larvae (L3). D. immitis L3s were labelled with 125I using an Iodogen catalysed reaction and either maintained in culture or placed in chambers that were implanted into Lewis rats. The larvae released 10-20% of the labelled material each day during the first 4 days of in vitro and in vivo development. The loss of surface-labelled peptides from developing larvae corresponded with an increase in the amount of trichloroacetic acid-precipitable radioactivity found in the culture medium. SDS-PAGE analysis of the labelled material showed that the same 35 and 6 kDa components found in larval extracts were shed into culture medium by the developing parasites. Metabolic labelling studies and experiments in which larvae were labelled after different times in culture indicated that, once released, the surface-associated molecules were not replaced, and that this net loss of surface peptides resulted in a reduction in the antigenic potential of the cuticular surface. Antibodies from both immunized rabbits and naturally infected dogs immunoprecipitated the 35 kDa component. In contrast, the 6 kDa molecule was not recognized by the antibodies in any of the sera tested. Shedding of surface peptides and reducing surface antigenicity may represent mechanisms by which D. immitis infective-stage larvae evade immune attack.

Animals↗
PubMed1989

Dirofilaria immitis: studies on anti-microfilarial immunity in Lewis rats.

The effect of vaccination on rates of microfilarial clearance using Dirofilaria immitis in male Lewis rats was examined. Animals were immunized with whole, dead microfilariae or a PBS extract of microfilariae in Freund's adjuvant. The immunized animals, as well as untreated and adjuvant controls, were challenged intravenously with 4 x 10(5) viable microfilariae (mf). The duration of microfilaremia was 15.5 days in rats vaccinated with whole mf, 17.7 days in those vaccinated with a PBS extract, 36.3 days for those vaccinated with adjuvant alone, and greater than 70 days for the untreated group. Analysis of the anti-microfilarial IgG response by ELISA and Western blots demonstrated that immunization induced significant amounts of antibody against high molecular weight peptides, particularly a peptide located at 105 kDa. Antibody levels in both groups of immunized animals continued to rise following challenge, reaching peak levels of 78-80 micrograms/ml on the day of microfilarial clearance. Decreasing microfilaremia following challenge was associated with an enhanced recognition of low molecular weight peptides.

Animals↗
PubMed1988

Dirofilaria immitis: biochemical and immunological characterization of the surface antigens from adult parasites.

The molecules associated with the surface of adult Dirofilaria immitis were identified and characterized employing IODO-GEN-mediated surface labeling methods. D. immitis female and male parasites were found to have a limited number of surface-associated proteins (17.5, 16, and 14.5 kDa) and glycoproteins (49 and 20 kDa) which were readily extracted from parasite homogenates in the absence of detergent. The major surface labeled proteins and glycoproteins were antigenic in rabbits, but appeared to elicit only a weak humoral response in dogs with patent dirofilariasis. In addition, a 10- to 6-kDa surface-associated glycolipid was identified which may form a coat on the outside of the parasite and play a role in immune evasion. In immunoprecipitation experiments, the glycolipid was not recognized by the antibodies from rabbits exposed to the glycolipid or by antibodies in the sera of patently infected animals. The glycolipid and the 14.5-kDa surface protein were selectively released by the adult parasite during in vitro culture.

Animals↗
PubMed1988

Antibiotics and immunity: effects of antibiotics on mitogen responsiveness of lymphocytes and interleukin-2 production.

The immunomodulating properties of antimicrobial drugs may have important implications in prescriptive practice. This is particularly so for patients whose immune system has been compromised. In this study, tetracycline, cephalothin, rifampicin, polymyxin B and nitrofurantoin reduced mitogen responsiveness of both B and T lymphocytes of mouse spleen cells and human peripheral blood lymphocytes in vitro in a dose-dependent fashion. Ampicillin, chloramphenicol, gentamicin, streptomycin and erythromycin had no effect. In the in vivo study none of the antibiotics affected mouse spleen cell transformation in response to mitogen. The addition of interleukin-2 (IL-2) did not prevent the effect of the antibiotics tested on human lymphocytes in vitro. Cephalothin, chloramphenicol and gentamicin decreased IL-2 production by mouse spleen cells in vitro.

Animals↗
PubMed1987

The effect of Brugia pahangi infection on survival of susceptible and refractory species of the Aedes scutellaris complex.

Life table statistics were used to examine the survival functions of filarial susceptible and refractory species of the Aedes scutellaris (Walker) group of mosquitoes, following infection with high and moderate doses of Brugia pahangi (Buckley & Edeson). Survivorship curves and hazard function curves were generated, and the median survival times and the proportions of mosquitoes surviving beyond the extrinsic incubation period of the parasite were determined. In the susceptible populations of Aedes polynesiensis Marks, Ae. pseudoscutellaris (Theobald) and Ae.tabu Ramalingam & Belkin a dose-response relationship was detected between parasite load and mortality. This relationship was characterized by a significant reduction in the proportions of infected female mosquitoes surviving at days 1 and 9 postinfection, reduction in the median survival times and an increase in the hazard rates as the infectious dose increased. The survival of the refractory species, Ae.alcasidi Huang and Ae.katherinensis Woodhill was not significantly affected by the infection. A positive correlation between microfilaraemia in the vertebrate host and parasite load in the susceptible mosquito populations was also observed. Regression analysis of the number of parasites recovered from susceptible mosquitoes at the time of death showed that mosquitoes at highest risk of dying harboured from 11.6 to 19.4 infective larvae when fed on a gerbil with sixty-five microfilariae per 20 microliters blood; this resulted in 34.4-40.2% mortality by day 9 postinfection. A mean number of 32.6-46.9 infective larvae was observed when these populations were exposed to a gerbil with a microfilaraemia of 150 mf/20 microliters and resulted in 72.8% to 80% mortality in these populations. Viable infective larvae were recovered from infected mosquitoes up to 50 days postinfection.

Aedes↗
PubMed1987

Antibiotics and immunity: effects of antibiotics on natural killer, antibody dependent cell-mediated cytotoxicity and antibody production.

We studied the effects of antibiotics on natural killer (NK), antibody dependent cell-mediated cytotoxicity (ADCC) and immunoglobulin production. When human peripheral blood lymphocytes were incubated overnight with the antibiotic before the assay, nitrofurantoin significantly reduced NK but not ADCC activity. Nitrofurantoin also suppressed both spontaneous and interferon-enhanced NK activities in a dose-dependent fashion. Though it did not affect spontaneous ADCC activity, nitrofurantoin suppressed interferon enhancement of ADCC. Chloramphenicol significantly decreased the number of plaque forming cells in mice. In addition to chloramphenicol, tetracycline, rifampicin, cephalothin, polymyxin B and nitrofurantoin reduced mitogen-induced polycloned immunoglobulin synthesis. Results of this study may have clinical relevance, especially in treating immunocompromised patients.

Animals↗
PubMed1977

Mastitis concomitant with traumatic reticulo-peritonitis in buffaloes.

Out of 500 dairy buffaloes examined for traumatic reticulitis in two farms, 51 buffaloes (10.2 %) were diagnosed as having the syndrome in its subacute and chronic forms. Of this 51 diseased animals, 39 had idiopathic mastitis (76.5 %). This high percentage of mastitis cases associated with traumatic reticulitis is considered as being four times the incidence of primary mastitis (20 %) in cattle. It is most likely that secondary mastitis is due to the contiguous spread of bacteria from the infected focus favoured by the devitalising effect of the foreign body syndrome.

Animals↗