المقالات العلمية – كلية الطب
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Item Antigenic diversity of Plasmodium falciparum and antibody-mediated parasite neutralization(Blackwell Scientific Publications, 1972) A Bolad, K BerzinsAbstract The malaria parasite Plasmodium falciparum, causing the most severe form of the disease in humans, is characterized by a broad antigenic diversity between different strains and isolates of the parasite. The antigenic diversity reflects on the one hand polymorphisms in allelic gene products and, on the other hand, antigenic variation as a result of expression of alternative genes in multigene families. Using selected polymorphic regions in two merozoite surface antigens, a method for genotyping P. falciparum parasites has been ...Item Pf332 Repeat Sequences Inhibit Plasmodium Falciparum Growth In Vitro On Their Own And In Cooperation With Human Monocytes(1999-09-01) A Bolad, K BerzinsRepeat sequences from the Plasmodium falciparum blood stage antigen Pf332 frequently comprise the pentapeptide VTEEI, an epitope recognized by certain parasite neutralizing antibodies. This motif was assembled in octavalent multiple antigen peptides as trimers (VTEEI)3 (MAP1). We optimized in vitro conditions for studying the inhibition of P. falciparum growth with rabbit antibodies raised against MAP1. When total IgG was used, the parasite growth inhibitory effect was unexpectedly low and agglutination of the erythrocytes in the culture was observed in the microscope, indicating that the low inhibition obtained was due to presence of haemagglutinins. Haemagglutinins bind both infected and non infected red blood cells. When parasitised erythrocytes rupture, released merozoites infect non infected red blood cells. When haemagglutinins were removed by absorbtion the inhibitory capacity of IgG was considerably increased. Affinity purified Pf332 specific antibodies induced higher inhibition at lower levels than did the rabbit total IgG. We also found that MAP1-specific antibodies increased the capacity of monocytes to inhibit growth of parasites. Surface exposure of Pf332 makes it accessible to opsonic??ic antibodies involved in phagocytosis of parasite infected erythrocytes and can mediate cellular killing of parasite. Thus, Pf332 specific antibodies proved able to inhibit parasite growth on their own as well as in cooperation with normal human monocytes.Item Antibody-mediated in vitro growth inhibition of field isolates of Plasmodium falciparum from asymptomatic children in Burkina Faso(The American Society of Tropical Medicine and Hygiene, 2003-06-01) Ahmed BoladAntibody-mediated inhibition of Plasmodium falciparum parasites in vitro reflects the potential parasite-neutralizing activity of the antibodies in vivo. In this study, immunoglobulins and P. falciparum isolates were collected from children with asymptomatic malaria in Burkina Faso. We demonstrate a significantly lower in vitro growth inhibitory activity against the P. falciparum field isolates by autologous host immunoglobulin compared with that of immunoglobulin from other individuals. To gain further insight to possible ...Item The Impact of the Use of Impregnated Curtains on Antibody Responses Againstplasmodium falciparumand on Complexity of Infecting Parasite Populations(A Bolad, 2003-08-01) A Bolad;Read 'The Impact of the Use of Impregnated Curtains on Antibody Responses AgainstPlasmodium falciparumand on Complexity of Infecting Parasite Populations' on Ovid Insights.Item Item Antibody responses in Plasmodium falciparum malaria and their relation to protection against the disease(Wenner-Grens institut för experimentell biologi, 2004) Ahmed Kamal BoladProtective immunity against Plasmodium falciparum may be obtained after repeated exposure to infection. Several studies indicate that immunity against the blood stages of the P. Falciparum infection is mainly antibody mediated. Protective antibodies may act either on their own, mediate antibody-dependent phagocytosis and/or cell-mediated neutralization of parasites. This thesis describes several aspects of humoral immune responses to P. falciparum infection in individuals of different age groups, different genetic background and with different degrees of malaria exposure. Several target antigens for antibody-mediated inhibition of parasite growth or invasion have been identified. One such antigen is Pf332, which appears on the surface of parasitized erythrocytes at late trophozoite and schizont stage. This surface exposure makes the antigen a possible target for opsonizing antibodies. We optimized an in vitro assay for studying cellmediated parasite neutralization in the presence of Pf332-reactive antibodies. Our data demonstrate that, Pf332 specific antibodies are able to inhibit parasite growth on their own and in cooperation with human monocytes. The P. falciparum parasites have evolved several mechanisms to evade the host neutralizing immune responses. In this thesis, we show that freshly isolated P. falciparum parasites from children living in a malaria endemic area of Burkina Faso were less sensitive for growth inhibition in vitro by autologous immunoglobulins (Ig) compared with heterologous ones. Analyses of two consecutive isolates taken 14 days apart, with regard to genotypes and sensitivity to growth inhibition in vitro, did not give any clear-cut indications on possible mechanisms leading to a reduced inhibitory activity in autologous parasite/antibody combinations. The frequent presence of persisting parasite clones in asymptomatic children indicates that the parasite possesses as yet undefined mechanisms to evade neutralizing immune responses. Transmission reducing measures such insecticide treated nets (ITNs) have been shown to be effective in reducing morbidity and mortality from malaria. However, concerns have been raised that ITNs usage could affect the acquisition of malaria immunity. We studied the effect of the use of insecticide treated curtains (ITC) on anti-malarial immune responses of children living in villages with ITC since birth. The use of ITC did neither affect the levels of parasite neutralizing immune responses nor the multiplicity of infection. These results indicate that the use of ITC does not interfere with the acquisition of anti-malarial immunity in children living in a malaria hyperendemic area. There is substantial evidence that the African Fulani tribe is markedly less susceptible to malaria infection compared to other sympatrically living ethnic tribes. We investigated the isotypic humoral responses against P. falciparum asexual blood stages in different ethnic groups living in sympatry in two countries exhibiting different malaria transmission intensities, Burkina Faso and Mali. We observed higher levels of the total malaria-specific-IgG and its cytophilic subclasses in individuals of the Fulani tribe as compared to non-Fulani individuals. Fulani individuals also showed higher levels of antibodies to measles antigen, indicating that the intertribal differences are not specific for malaria and might reflect a generally activated immune system in the Fulani.Item Antiplasmodial activity of seven plants used in African folk medicine(Medknow Publications on behalf of Indian Pharmacological Society, 2004) Ahmed Bolad, G Bidla; VPK Titanji, B Joko; G El-Ghazali, K BerzinsResults are expressed as mean+ SD. The differences between experimental groups were compared by one-way ANOVA (control Vs treatment) followed by Student-Neuman-Keuls test and were considered statistically significant at P< 0.05. The number of acetic acid induced writhings were significantly reduced by treatment with AO-1 in both the doses. The effect was found to be more than that of the standard, diclofenac (20 mg/kg) at a dose of 100 mg/kg (Table 1). AO-1 pretreatment significantly reduced the paw edema in rats. The effect ...Item Antibodies to the Plasmodium falciparum antigen Pf332 inhibit parasite growth in vitro on their own and in cooperation with monocytes(Wenner-Grens institut för experimentell biologi, 2004) AK Bolad, L Xu; K BerzinsProtective immunity against Plasmodium falciparum may be obtained after repeated exposure to infection. Several studies indicate that immunity against the blood stages of the P. Falciparum infection is mainly antibody mediated. Protective antibodies may act either on their own, mediate antibody-dependent phagocytosis and/or cell-mediated neutralization of parasites. This thesis describes several aspects of humoral immune responses to P. falciparum infection in individuals of different age groups, different genetic background and with different degrees of malaria exposure. Several target antigens for antibody-mediated inhibition of parasite growth or invasion have been identified. One such antigen is Pf332, which appears on the surface of parasitized erythrocytes at late trophozoite and schizont stage. This surface exposure makes the antigen a possible target for opsonizing antibodies. We optimized an in vitro assay for studying cellmediated parasite neutralization in the presence of Pf332-reactive antibodies. Our data demonstrate that, Pf332 specific antibodies are able to inhibit parasite growth on their own and in cooperation with human monocytes. The P. falciparum parasites have evolved several mechanisms to evade the host neutralizing immune responses. In this thesis, we show that freshly isolated P. falciparum parasites from children living in a malaria endemic area of Burkina Faso were less sensitive for growth inhibition in vitro by autologous immunoglobulins (Ig) compared with heterologous ones. Analyses of two consecutive isolates taken 14 days apart, with regard to genotypes and sensitivity to growth inhibition in vitro, did not give any clear-cut indications on possible mechanisms leading to a reduced inhibitory activity in autologous parasite/antibody combinations. The frequent presence of persisting parasite clones in asymptomatic children indicates that the parasite possesses as yet undefined mechanisms to evade neutralizing immune responses. Transmission reducing measures such insecticide treated nets (ITNs) have been shown to be effective in reducing morbidity and mortality from malaria. However, concerns have been raised that ITNs usage could affect the acquisition of malaria immunity. We studied the effect of the use of insecticide treated curtains (ITC) on anti-malarial immune responses of children living in villages with ITC since birth. The use of ITC did neither affect the levels of parasite neutralizing immune responses nor the multiplicity of infection. These results indicate that the use of ITC does not interfere with the acquisition of anti-malarial immunity in children living in a malaria hyperendemic area. There is substantial evidence that the African Fulani tribe is markedly less susceptible to malaria infection compared to other sympatrically living ethnic tribes. We investigated the isotypic humoral responses against P. falciparum asexual blood stages in different ethnic groups living in sympatry in two countries exhibiting different malaria transmission intensities, Burkina Faso and Mali. We observed higher levels of the total malaria-specific-IgG and its cytophilic subclasses in individuals of the Fulani tribe as compared to non-Fulani individuals. Fulani individuals also showed higher levels of antibodies to measles antigen, indicating that the intertribal differences are not specific for malaria and might reflect a generally activated immune system in the Fulani.Item The use of impregnated curtains does not affect antibody responses against Plasmodium falciparum and complexity of infecting parasite populations in children from Burkina Faso(Elsevier, 2004-05-31) A Bolad, I Nebie; F Esposito, Klavs BerzinsIn Burkina Faso, where malaria is hyper-endemic and transmission intensity is very high, the majority of malaria-related morbidity and mortality occurs in children less than 5 years of age. A control measure such as the use of insecticide-treated curtains (ITC) significantly reduces transmission of malaria infection. Concerns remain whether reduced transmission intensity may lead to a delay in the development of immunity in younger children and even to a partial loss of already acquired immunity. In this study, the levels of P. falciparum- ...Item Distinct interethnic differences in IgG class/subclass and IgM antibody responses to malaria antigens but not in IgG responses to non-malarial antigens in sympatric tribes living in West Africa(Scandinavian Journal of Immunology, 2005) Ahmed BoladThe well-established relative resistance to malaria observed in the Fulani as compared with other sympatric tribes in West Africa has been attributed to their higher levels of serum immunoglobulin (Ig) G antibodies to malarial antigens. In this study, we confirm and extend the previous findings by analyses of the levels of IgM, IgG and IgG subclasses of anti-malarial antibodies in asymptomatic individuals of different sympatric tribes in Burkina Faso (Fulani/Mossi) and Mali (Fulani/Dogon). The Fulani showed significantly higher median concentrations of anti-malarial IgG and IgM antibodies than the sympatric tribes at both locations. Although the overall subclass pattern of antibodies did not differ between the tribes, with IgG1 and IgG3 as dominant, the Fulani showed consistently significantly higher levels of these subclasses as compared with those of the non-Fulani individuals. No significant differences were seen in the levels of total IgG between the tribes, but the Fulani showed significantly higher levels of total IgM than their neighbours in both countries. While the antibody levels to some nonmalarial antigens showed the same pattern of differences seen for antibody levels to malaria antigens, no significant such differences were seen with antibodies to other nonmalarial antigens. In conclusion, our results show that the Fulani in two different countries show higher levels of anti-malarial antibodies than sympatric tribes, and this appears not to be a reflection of a general hyper-reactivity in the Fulani.Item The use of impregnated curtains does not affect antibody responses against Plasmodium falciparum and complexity of infecting parasite populations in children from Burkina Faso [MIM-AB-123513](ELSEVIER SCIENCE BV, 2005-01-01) A Bolad, I Nebie; F Esposito, K BerzinsItem Interethnic differences in antibody responses to malarial antigens but not to non-malarial antigen in sympatric tribes living in West Africa [MIM-EI-119816](ELSEVIER SCIENCE BV, 2005-01-01) A BoladItem Distinct interethnic differences in immunoglobulin G class/subclass and immunoglobulin M antibody responses to malaria antigens but not in immunoglobulin G responses to nonmalarial antigens in sympatric tribes living in West Africa(Blackwell Science Ltd, 2005-04) A BoladAbstract The well-established relative resistance to malaria observed in the Fulani as compared with other sympatric tribes in West Africa has been attributed to their higher levels of serum immunoglobulin (Ig) G antibodies to malarial antigens. In this study, we confirm and extend the previous findings by analyses of the levels of IgM, IgG and IgG subclasses of anti- malarial antibodies in asymptomatic individuals of different sympatric tribes in Burkina Faso (Fulani/Mossi) and Mali (Fulani/Dogon). The Fulani showed significantly higher median ...Item Analysis of T-cell responses in malaria-exposed and non-exposed donors using Plasmodium falciparum asexual blood stages enriched by a simple centrifugation method(Elsevier, 2006-01-31) Ahmed Bolad, Salah E Farouk; Jinfeng Shen, Klavs Berzins; Marita Troye-BlombergSeveral studies have reported on similar in vitro cellular responses to different malaria-antigen preparations in both malaria-primed and un-primed donors. Whether intact live parasites can exert a distinct type of response in either of the two groups is not well known. In this study, we developed a simple three-step centrifugation method for simultaneous enrichment of early and late blood stages from Plasmodium falciparum cultures. Such enriched P. falciparum fractions and other antigen preparations were used to stimulate lymphocytes from malaria-exposed and non-exposed individuals to examine the proliferative activity and expansion of CD3+, γδ+, CD4+, and CD8+ T cells. While lymphocytes from malaria non-exposed donors proliferated relatively higher than those from malaria-exposed donors in response to most antigens tested, the enriched fractions of live parasites exerted higher proliferative responses on cells from the latter donors. This suggests the existence of memory cells in the malaria-exposed donors, but not in the non-exposed ones. Flow cytometric analysis revealed a higher percentage expansion of CD4+ T cells in the responding cells of the exposed donors than the non-exposed ones. Taken together, this study reports on a simple method that simultaneously enriches for intact live early and late blood stages of P. falciparum parasites. Moreover, the study revealed higher expansion CD4+ T cells in the exposed individuals than the non-exposed in response to live malaria parasites and not to other parasite–antigen preparations.Item Glutamate-rich protein (GLURP) induces antibodies that inhibit in vitro growth of Plasmodium falciparum in a phase 1 malaria vaccine trial(Elsevier, 2007) Ahmed BoladThe glutamate-rich protein (GLURP) of P. falciparum is the target of cytophilic antibodies which are significantly associated with protection against clinical malaria. A phase 1 clinical trial was conducted in healthy adult volunteers with the long synthetic peptide (LSP) GLURP85–213 combined with either Aluminum Hydroxide (Alum, 18 volunteers) or Montanide ISA 720 (ISA, 18 volunteers) as adjuvants. Immunizations with 10, 30 or 100μg GLURP85–213 were administered subcutaneously at days 0, 30, and 120. Adverse ...Item Comparison of Rheumatoid Factor and anti-Cyclic-Citrullinated protein antibodies for the Diagnosis of rheumatic arthritis in Khartoum, Sudan(Al Neelain Medical Research Centre, 2008) Ahmed Bolad, Shaaban Khudair; Mohammed Abbas, Mowahib Al EdressyBackground: The objective of the current study was to determine the sensitivity and specificity of anti-Cyclic-Citrullinated protein antibodies (anti-CCP antibodies) as compared to that of Rheumatoid Factor (RF) in diagnosing patients with rheumatoid arthritis (RA) Methodology Fifty six samples were collected from Sudanese patients (46 females, 9 males) with rheumatic diseases who visited the rheumatology clinic ElRibat Hospital, Khartoum, Sudan. Titers of RF and anti-CCP antibodies of each patient were recorded. Sensitivity and specificity of the test were evaluated using ELISA as the gold standard method. Results The sensitivity of (RF) test (41/56) was 73.2% whereas the sensitivity of Anti CCP test (34/56) was 60.7%. The specificity of RF test (44/56) was 78.6%, whereas the specificity of Anti CCP test (54/56) was 96.4%. Conclusions The combination of anti-CCP and RF tests provides nearly 100% and thus could be helpful in the differential diagnosis of RA and other rheumatic diseases Comparison of Rheumatoid Factor and anti-Cyclic-Citrullinated protein antibodies for the Diagnosis of rheumatic arthritis in Khartoum, Sudan. Available from: https://www.researchgate.net/publication/271014292_Comparison_of_Rheumatoid_Factor_and_anti-Cyclic-Citrullinated_protein_antibodies_for_the_Diagnosis_of_rheumatic_arthritis_in_Khartoum_Sudan [accessed Oct 08 2017].Item Culturing of erythrocytic asexual stages of Plasmodium falciparum and P. vivax(Methods in malaria research, 2008) Fingani Mphande, Sandra Nilsson; Ahmed BoladComment: For growing parasites from patient blood, use 10 g of Albumax for 1 liter of complete MCM. The vast majority of cultures will survive at least 2 weeks. It is also important to avoid serum in the culture for preparation of crude parasite antigen (see SEROLOGY, section III: B). Not all strains can be adopted to Albumax II medium.Item Detection of Helicobacter pylori Reactive IgA and IgG Antibodies Using Enzyme Linked Immunsorbent Assay (ELISA)(Sudanese Association of Dermatologists, 2010) Ahmed Bolad, Samah Seif Eldein; Mohamed LutfiBackground: Helicobacter pylori (H. pylori) infection is usually acquiredduring the early years of life and persists for several years. Recent investigations pointed to a potential role of H. pylori infection of the upper gastrointestinal tract as a possible causative agent in chronic urticaria (CU).Objectives: This study is aiming at evaluating the relationship between H. pylori and chronic urticaria in Sudanese patients.Methods and patients: Fifty patients with idiopathic CU, twenty five ofother skin disorder and ten healthy controls were enrolled estimated for serum H.pylori Immunoglobulin G (IgG) and A (IgA) antibodies levels using Enzyme Linked Immunsorbent Assay (ELISA). All the results were analyzed using the Microsoft Office Excel (Microsoft Office Excel for windows; 2003) and SPSS (SPSS for windows 17).Results and discussion: The IgG and IgA levels of control group weresignificantly lower compared with both patients with chronic urticaria (P = 0.001 for IgG) (P = 0.001 for IgA) and patients with other skin disorders (P = 0.011 for IgG) (P = 0.006 for IgA). Receiver Operating Characteristic curve (ROC curve) analysis revealed that the area under ROC curves of IgA is higher compared to IgG (0.80 0Vs 0.890). In conclusion the current study revealed that patients with H. pylori infection have an increased tendency to develop urticaria. H. pylori reactive IgA antibodies correlate best with the infection.Item Sequestrated Plasmodium falciparum parasites in human infections: different genotype distribution in placental as compared to that in the peripheral circulation(Al Neelain Medical Research Centre, 2011) Ahmed Bolad, Alamin Abdulkareem Alamin,; Imad Mohammed Fadl-ElmulaABSTRACT Introduction: In regions highly endemic for malaria, the prevalence of placental malaria ranges from 30% to 60% and has been associated with increased risk of adverse infant outcomes, particularly in primigravidae. Objectives: The study was conducted on mothers after delivery to detect sequestered Plasmodium falciparum (P. falciparum) parasite by using PCR based genotyping technique. Materials and methods: The study was conducted during the period of January 2009 to September 2011. 5ml of venous and placental blood were obtained from 75 mothers after delivery, attended to Omdurman Maternity Hospital. Genomic DNA was extracted from peripheral and placental blood samples using modified phenol chloroform technique. The msp-1 allele (MAD20,) and msp-2 allele A1, A2, B1 and B2, plasmodium falciparum primers were used for PCR. The PCR product was analyzed on 1.5% Agarose gel and visualized by gel documentation system after ethidium bromide staining. Results: The results revealed that the overall malaria detection rate in peripheral blood and placental blood using ICT was 10.7%. With the PCR (msp-1 alleles) the detection rate of malaria in peripheral blood was found to be 9.3%, while in placental blood the same technique showed a detection rate of 10.7%. For PCR (msp-2 alleles), the detection rate of malaria in peripheral blood was 12%, while in placental blood the same technique showed detection rate of 21.3% malaria. Conclusion: In the vast majority of cases, some sequestered genotypes remain hidden, undetected in the peripheral circulation, indicating that analysis of peripheral parasites generates a partial picture of a P. falciparum infection. The cord blood must be collected from the umbilical cord to detected placental P. falciparum infection particularly in primigravidaeItem Reliability of Polymerase Chain Reaction (PCR) for Detection of Hepatitis B virus (HBV) in Healthy Blood Donors as Compared to That of Enzyme-Linked Immuno-Sorbent Assay (ELISA)(Sudan Journal of Medical Science, 2011) Ahmed Bolad, Myada Hashim; Mohammed LutfiCareful screening of the donated blood is mandatory and tests that are currently used for the detection HBV are mainly serological using enzyme lined immune-sorbent assay (ELISA). These tests may have some design for example, missing of some infected individuals that fall at or in the window period. More sensitive tests for example polymerase chain reaction (PCR) that may have the capacity to detect viruses RNA or DNA are a necessity now to minimize the danger of transmitting such a serious disease through blood transfusion, a life saving maneuver. This study has been conducted for detection of hepatitis B virus in healthy donate blood using two methods Enzyme Linked Immune Sorbent Assay (ELISA) as serological test and Polymerase Chain Reaction (PCR) as molecular method. In this study, samples were collected randomly from 100 apparently healthy middle-age blood donors at some stage during donation session of central blood bank in Khartoum teaching hospital. Individuals with positive screening were asked for repeat sample and confirmatory test were carried out. Hepatitis B surface antigen (HBsAg) screening test were performed using ELISA and PCR tests. All the results were analyzed using Statistical Packages of Social Sciences version13 (SPSS). HBs Ag was detected in 15% of samples by using ELISA while, 85% of samples were found to be negative. However, when using PCR for detection of Hepatitis B virus deoxyribonucleic acid (HBV DNA), 23% of samples were found to be positive. Accordingly, it seems that ELISA is an excellent test to rule out HBV infection in non-infected people but it may be unreliable to confirm the disease in actually infected patients.
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