Browsing by Author "Ahmed, Firoz"

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Antigen-specific immunoglobulin A antibodies secreted from circulating B cells are an effective marker for recent local immune responses in patients with cholera: comparison to antibody-secreting cell responses and other immunological markers
(2003) Qadri, Firdausi; Ryan, Edward T.; Faruque, A.S.G.; Ahmed, Firoz; Khan, Ashraful Islam; Islam, M. Munirul; Akramuzzaman, Syed M.; Sack, David A.; Calderwood, Stephen B.
Assessing Content-Based Instruction (CBI) in the Context of Teaching English at the Tertiary Level of Bangladesh
(Daffodil International University, 2023-07) Ahmed, Firoz; Akter, Rahima
This study aims to assess the English language outcome of Content-Based Instruction (CBI) among EFL learners of English at the tertiary level of Bangladesh and the problems involved in this process, where a group of students and teachers (existing) of English department were the focus of the study. To conduct this study, a mixed-method approach was applied where research instruments such as questionnaire and classroom observation were used. In total, 279 (students=260, teachers=19) respon dents participated in the survey questionnaires and classroom observations. The findings of this study suggested that though teachers and students prefer the CBI approach, some drawbacks were found in this learning process. Keywords: Content-Based Instruction, Tertiary Level Learners of Bangladesh, EFL context
Characterization of the Immune Response to Vibrio cholerae 01 antigens and its impact on Vaccine development strategies
(© University of Dhaka, 2025-05-04) Ahmed, Firoz
Characterization of the immune response to vibrio cholerae O1 antigens and its impact on vaccine development strategies
(University of Dhaka, 2014-07-13) Ahmed, Firoz
Cholera persists as one of the major causes of mortality and morbidity globally. Prevention using different approaches are needed, one of which is vaccination. Improving immunogenicity of oral cholera vaccines and production of effective single dose schedules suitable for all age groups and populations is the prerequisite. Historically injectable cholera vaccines have been replaced in the last three decades by oral mucosal vaccines but neither fulfills all the requisites. The aim was to evaluate potential vaccine immunogens which have not been tested earlier for generating protective immunity. The concept of a one dose vaccine using bacterial antigen(s) through a “needle free approach” of immunization via the transcutaneous route (TCI) for enteric vaccines was explored in this work. The lipopolysaccharide (LPS) of Vibrio cholerae O1 is the most consistently described protection associated immunogen and has been identified as the most important of the antigens described so far. Epidemiological studies of natural infection in cholera suggest that Inaba serotype is more protective against subsequent attacks of cholera than the Ogawa serotype. Crystallographic studies have revealed antigenic determinants of LPS Ogawa and binding pattern of monoclonal antibodies (mAbs) using synthetic fragment of Ogawa in the O-specific polysaccharide (O-PS) region. Previous studies with other mAbs have indicated involvement of both the core and the O-specific polysaccharide as common antigenic determinants. This dissertation describes the first crystal structure of a mAb F-22-30 that recognizes a common epitope present in both the Ogawa and Inaba serotypes of V. cholerae O1. Modeling calculations and preliminary NMR results suggest that binding pocket at the center of antibody recombination site could bind side-chain of a perosaminyl residue from the O-PS with higher accessibility compared with core-PS implying a lateral recognition in contrast to antibodies specific for the Ogawa serotype. Mechanism of the immune response elicited by transcutaneous route of immunization (TCI) with potential V. cholerae antigens was evaluated as alternative modes of vaccination compared with oral (ORI) and subcutaneous route (SCI) with the same antigens i.e. recombinant cholera toxin B subunit (CTB), cholera toxin (CT), recombinant toxin co-regulated pilus A (TcpA), LPS Ogawa and Inaba and in-house prepared membrane extract in Balb/c mice to determine the immunoglobulin isotype patterns and its properties linked with protection. Both humoral and cellular immune responses induced by the immunization were studied using ELISA and flow cytometric procedures to assess and phenotypic changes in the mucosal and systemic compartments were analyzed. Among the three routes of immunization, SCI showed robust elevation pattern with superiority of IgG compared toIgM and IgA respectively. TcpA in the TCI route did not up-regulate IgA, while CT and CTB were seen to respond with all three antibody isotypes. CTB immunized mice showed reduced serum antibody titer in the zinc supplemented but CT and TcpA individually as well as co-administered together had no effect. When CT in the TCI and SCI route generated all four IgG subclasses, TcpA and LPS-specific antibody response was only IgG1 subclass where membrane extract has overcome the inherent limitation of LPS. However, sera obtained from both CT and TcpA immunized were negative for vibriocidal antibody responses. Membrane extract displayed more than 10 times elevated IgM and IgG titers with vibriocidal response than LPS with comparable positive effect of zinc supplementation. Moreover, ALS antibody titers were comparable with ELISA and vibriocidal assays and expressed the recently formed status of the humoral response. Expression of increased CD19+ve B cells in blood and lamina propria as well as CD4+ cells in the lamina propria were detected following TCI. Significant elevations of the co-stimulatory marker CD40 in the CD19+ve B cell population as well as CD28 and CD154 in the CD4 population were observed in spleen and lamina propria. The expression of homing markers, cutaneous lymphocyte antigen (CLA) was increased in blood and lamina propria (CD19, CD4), whereas an increase of the gut homing marker (β7) was not seen in blood or the mucosal surface in the different cell types. The results of TCI immunization were compared with those obtained after subcutaneous (SCI) where similar or discordant results were seen but interestingly the magnitude of responses by TCI was equal to that seen by SCI. The isotype switch and antibody maturation patterns elicited by the TCI route of immunization incorporating zinc as another confounder with the potential immunogens, applying a novel in-house immunogenetic method, were studied. Finally, bioinformatics approaches were applied to compare position specific similarities and dissimilarities of LPS specific 'membrane extract' immunized antibody sequences with experimentally characterized mAb F-22-30 for better understanding the binding affinity of the carbohydrate antigen. Considering the percentages of antigen-specific cellular representation at different compartments, CTB specific cells was the highest compared to TcpA and LPS specific pool. With the novel in situ positive selection immunogenetic technique, first murine B-cell VH and VL chain repertoire specific for protein and polysaccharide antigens were reported. VH and VL amino acid sequence comparison demonstrated variable expression in co-administration than individual immunogens. Amino acids expressed through immunization of polysaccharide immunogens were more stable than protein immunogens specific sequences. Moreover, CDRH3 length of antibody sequences to protein immunogens varied between 8 and 19 amino acids with CTB specific shorter sequences containing more charged and hydrophobic residues. Further bioinformatics approaches with Inaba specific sequences obtained through TCI confirmed ligand binding with similar nature amino acids to be identical groove type binding pattern. Findings presented here suggest that the newer, needle-free TCI route is suitable for inducing humoral and cellular immune responses in the systemic and mucosal compartments and should be considered as an option in vaccine development strategies.
Classification of EEG-Based Auditory Evoked Potentials Using Entropy-Based Features and Machine Learning Techniques
(IEEE, 2023-11-06) Islam, Thamina; Ahmed, Firoz; Ahmed, Nayem; Naziullah, Shekh; Islam, Md Nahidul; Rashid, Mamunur
Hearing loss is a prevalent impairment that disrupts interactions with others and individuals' learning abilities. Immediate and accurate diagnosis of hearing loss using Electroencephalogram (EEG) signals, particularly Auditory Evoked Potentials (AEP), is considered the most effective approach to address this issue. The AEP signals, generated in the cerebral cortex in response to auditory stimuli, serve as the most reliable method for diagnosing deafness. This study introduces a novel approach for detecting hearing ability through the classification of EEG-AEP signals. The current experiment makes use of a publicly available dataset that contains AEP responses from 16 people who responded to auditory stimuli on either the left or right side. Sample Entropy is employed to extract the feature, capturing the complex temporal dynamics of the EEG signals. Four popular machine learning-based classifiers, namely Support Vector Machines (SVM), K-Nearest Neighbors (KNN), Random Forest (RF), and Logistic Regression (LR), are utilized for classification purposes. The results indicate that SVM achieves the highest classification accuracy of 99.37% with subject-4 and the average accuracy of 90.74% is achieved with all subjects. This finding shows the effectiveness of Sample Entropy as a feature extraction technique for characterizing AEPs and highlights the potential of SVM as a robust classifier for the accurate identification of auditory stimuli localization. The accuracy achieved in this study indicates a promising direction for the development of reliable and non-invasive methods for hearing-related diagnoses.
Clinical evaluation of dengue and identification of risk factors for severe disease: protocol for a multicentre study in 8 countries
(© 2016 BMC Infectious Diseases, 2/18/2016) Jaenisch, Thomas; Hoai Tam, Dong Thi; Thanh Kieu, Nguyen Tan; Ngoc, Tran Van; Tran Nam, Nguyen; Kinh, Nguyen Van; Yacoub, Sophie; Chanpheaktra, Ngoun; Kumar, Varun; Chai See, Lucy Lum; Sathar, Jameela; Sandoval, Ernesto Pleités; Marón Alfaro, Gabriela Maria; Laksono, Ida Safitri; Mahendradhata, Yodi; Sarker, Malabika; Ahmed, Firoz; Caprara, Andrea; Benevides, Bruno Souza; Marques, Ernesto T. A.; Magalhaes, Tereza; Brasil, Patricia; Netto, Marco; Tami, Adriana; Bethencourt, Sarah E.; Guzman, Maria; Simmons, Cameron; Quyen, Nguyen Thanh Ha; Merson, Laura; Dung, Nguyen Thi Phuong; Beck, Dorothea; Wirths, Marius; Wolbers, Marcel; Lam, Phung Khanh; Rosenberger, Kerstin; Wills, Bridget
Background The burden of dengue continues to increase globally, with an estimated 100 million clinically apparent infections occurring each year. Although most dengue infections are asymptomatic, patients can present with a wide spectrum of clinical symptoms ranging from mild febrile illness through to severe manifestations of bleeding, organ impairment, and hypovolaemic shock due to a systemic vascular leak syndrome. Clinical diagnosis of dengue and identification of which patients are likely to develop severe disease remain challenging. This study aims to improve diagnosis and clinical management through approaches designed a) to differentiate between dengue and other common febrile illness within 72 h of fever onset, and b) among patients with dengue to identify markers that are predictive of the likelihood of evolving to a more severe disease course. Method/Design This is a prospective multi-centre observational study aiming to enrol 7–8000 participants aged ≥ 5 years presenting with a febrile illness consistent with dengue to outpatient health facilities in 8 countries across Asia and Latin America. Patients presenting within 72 h of fever onset who do not exhibit signs of severe disease are eligible for the study. A broad range of clinical and laboratory parameters are assessed daily for up to 6 days during the acute illness, and also at a follow up visit 1 week later. Discussion Data from this large cohort of patients, enrolled early with undifferentiated fever, will be used to develop a practical diagnostic algorithm and a robust clinical case definition for dengue. Additionally, among patients with confirmed dengue we aim to identify simple clinical and laboratory parameters associated with progression to a more severe disease course. We will also investigate early virological and serological correlates of severe disease, and examine genetic associations in this large heterogeneous cohort. In addition the results will be used to assess the new World Health Organization classification scheme for dengue in practice, and to update the guidelines for “Integrated Management of Childhood Illness” used in dengue-endemic countries.
Clinical evaluation of dengue and identification of risk factors for severe disease: protocol for a multicentre study in 8 countries
(© 2016 BMC Infectious Diseases, 2/18/2016) Jaenisch, Thomas; Hoai Tam, Dong Thi; Thanh Kieu, Nguyen Tan; Ngoc, Tran Van; Tran Nam, Nguyen; Kinh, Nguyen Van; Yacoub, Sophie; Chanpheaktra, Ngoun; Kumar, Varun; Chai See, Lucy Lum; Sathar, Jameela; Sandoval, Ernesto Pleités; Marón Alfaro, Gabriela Maria; Laksono, Ida Safitri; Mahendradhata, Yodi; Sarker, Malabika; Ahmed, Firoz; Caprara, Andrea; Benevides, Bruno Souza; Marques, Ernesto T. A.; Magalhaes, Tereza; Brasil, Patricia; Netto, Marco; Tami, Adriana; Bethencourt, Sarah E.; Guzman, Maria; Simmons, Cameron; Quyen, Nguyen Thanh Ha; Merson, Laura; Dung, Nguyen Thi Phuong; Beck, Dorothea; Wirths, Marius; Wolbers, Marcel; Lam, Phung Khanh; Rosenberger, Kerstin; Wills, Bridget
Background The burden of dengue continues to increase globally, with an estimated 100 million clinically apparent infections occurring each year. Although most dengue infections are asymptomatic, patients can present with a wide spectrum of clinical symptoms ranging from mild febrile illness through to severe manifestations of bleeding, organ impairment, and hypovolaemic shock due to a systemic vascular leak syndrome. Clinical diagnosis of dengue and identification of which patients are likely to develop severe disease remain challenging. This study aims to improve diagnosis and clinical management through approaches designed a) to differentiate between dengue and other common febrile illness within 72 h of fever onset, and b) among patients with dengue to identify markers that are predictive of the likelihood of evolving to a more severe disease course. Method/Design This is a prospective multi-centre observational study aiming to enrol 7–8000 participants aged ≥ 5 years presenting with a febrile illness consistent with dengue to outpatient health facilities in 8 countries across Asia and Latin America. Patients presenting within 72 h of fever onset who do not exhibit signs of severe disease are eligible for the study. A broad range of clinical and laboratory parameters are assessed daily for up to 6 days during the acute illness, and also at a follow up visit 1 week later. Discussion Data from this large cohort of patients, enrolled early with undifferentiated fever, will be used to develop a practical diagnostic algorithm and a robust clinical case definition for dengue. Additionally, among patients with confirmed dengue we aim to identify simple clinical and laboratory parameters associated with progression to a more severe disease course. We will also investigate early virological and serological correlates of severe disease, and examine genetic associations in this large heterogeneous cohort. In addition the results will be used to assess the new World Health Organization classification scheme for dengue in practice, and to update the guidelines for “Integrated Management of Childhood Illness” used in dengue-endemic countries.
Increased levels of inflammatory mediators in children and adults infected with Vibrio cholerae O1 and O139
(2002) Qadri, Firdausi; Raqib, Rubhana; Ahmed, Firoz; Rahman, Taufiqur; Wenneras, Christine; Das, Swadesh Kumar; Alam, Nur Haque; Mathan, Minnie M.; Svennerholm, Ann-Mari
Lipopolysaccharide- and cholera toxin-specific subclass distribution of B-cell responses in cholera
(1999-11) Qadri, Firdausi; Ahmed, Firoz; Karim, M. Manjurul; Wenneras, Christine; Begum, Yasmin Ara; Abdus, Salam Mohammad; Albert, M. John; McGhee, Jerry R.
Safety and immunogenicity of an oral, inactivated enterotoxigenic Escherichia coli plus cholera toxin B subunit vaccine in Bangladeshi adults and children
(2000) Qadri, Firdausi; Wennerâs, Christine; Ahmed, Firoz; Asaduzzaman, Muhammad; Saha, Debashish; Albert, M.J.; Sack, R.B.; Svennerholm, Ann-Mari
Safety and immunogenicity of an oral, inactivated enterotoxigenic Escherichia coli plus cholera toxin B subunit vaccine in Bangladeshi children 18-36 months of age
(2003) Qadri, Firdausi; Ahmed, Tanvir; Ahmed, Firoz; Sack, R. Bradley; Sack, David A.; Svennerholm, Ann-Mari
Study on Water pollution of Vairab River from Nowapara, Jessore to Labon Chara, Khulna
(Khulna University of Engineering & Technology (KUET), Khulna, Bangladesh, 2014-05) Ahmed, Firoz; Aziz, Prof. Dr. Md. Abdul
only Vairab river is the vital source of water in Nowapara, Jessore to Khulna and is being polluted increasingly by effluents discharged from industries, municipal sewage, household wastes, linical wastes and oils. The purpose of this study is to investigate the impact of this wastewater on the river and thus to provide an updated report on the state of water quality of river Vairab. The water sample were collected from different areas in the river Vairab and analyzed for physico-chernical parameters and fresh water elements in the month of July, 2013 to November, 2013. The values of Temperature, turbidity, pH, chloride, hardness, DO, BUD, COD, Fe, As, Pb. Cd and Measured. During study period the temperature. turbidity,pH, hardness, chloride, DO, BUD and COD were found to be 28 Cr in the river °C to 31.5°C. 37 to 947 NTU, 7.2 to 8.01, 92 to 140 ppm, 9 to 34 ppm, 122 to 5.51 mg/L, 0.22 to 5.79 and 3.80 to 10.80 mg/L respectively. The concentration of Fe, Pb, As, Cd and Cr were found to be 0.10 to 2.60 ppm, 0.004 to 0.025 ppm, 0.001 to 0.004 ppm, 0.00015 to 0.0094 ppm and 0.001 to 0.006 ppm respectively. From the results of investigation, it was observed that the values of pH, Cl, hardness, As, Pb, Cd and Cr were within standard limit but the values of temperature, turbidity, DO, BUD, COD and Fe were not within acceptable limit as recommended by WHO and BDS guidelines. The results obtained from this investigation will help the people of the research area to be conscious for using the water in the Vairab river.
Supplementation with zinc, but not vitamin A, improves seroconversion to vibriocidal antibody in children given an oral cholera vaccine
(2003) Albert, M.John; Qadri, Firdausi; Wahed, Mohammad A.; Ahmed, Tanvir; Rahman, A.S.M. Hamidur; Ahmed, Firoz; Bhuiyan, Nurul A.; Zaman, K. Zaman; Baqui, Abdullah H.; Clemens, John D.; Black, Robert E.