M A Hossain

Bio: M A Hossain is an academic researcher from Chittagong Medical College Hospital. The author has contributed to research in topics: Malaria & Scrub typhus. The author has an hindex of 5, co-authored 6 publications receiving 1611 citations.

Spread of Artemisinin Resistance in Plasmodium falciparum Malaria

Abstract: BACKGROUND: Artemisinin resistance in Plasmodium falciparum has emerged in Southeast Asia and now poses a threat to the control and elimination of malaria. Mapping the geographic extent of resistance is essential for planning containment and elimination strategies. METHODS: Between May 2011 and April 2013, we enrolled 1241 adults and children with acute, uncomplicated falciparum malaria in an open-label trial at 15 sites in 10 countries (7 in Asia and 3 in Africa). Patients received artesunate, administered orally at a daily dose of either 2 mg per kilogram of body weight per day or 4 mg per kilogram, for 3 days, followed by a standard 3-day course of artemisinin-based combination therapy. Parasite counts in peripheral-blood samples were measured every 6 hours, and the parasite clearance half-lives were determined. RESULTS: The median parasite clearance half-lives ranged from 1.9 hours in the Democratic Republic of Congo to 7.0 hours at the Thailand-Cambodia border. Slowly clearing infections (parasite clearance half-life >5 hours), strongly associated with single point mutations in the "propeller" region of the P. falciparum kelch protein gene on chromosome 13 (kelch13), were detected throughout mainland Southeast Asia from southern Vietnam to central Myanmar. The incidence of pretreatment and post-treatment gametocytemia was higher among patients with slow parasite clearance, suggesting greater potential for transmission. In western Cambodia, where artemisinin-based combination therapies are failing, the 6-day course of antimalarial therapy was associated with a cure rate of 97.7% (95% confidence interval, 90.9 to 99.4) at 42 days. CONCLUSIONS: Artemisinin resistance to P. falciparum, which is now prevalent across mainland Southeast Asia, is associated with mutations in kelch13. Prolonged courses of artemisinin-based combination therapies are currently efficacious in areas where standard 3-day treatments are failing. (Funded by the U.K. Department of International Development and others; ClinicalTrials.gov number, NCT01350856.).

Drug-resistant malaria in Bangladesh: an in vitro assessment.

Abstract: Forty-four Plasmodium falciparum isolates from Bangladesh and 22 from western Thailand were success- fully tested for their drug susceptibility. High degrees of resistance were observed against chloroquine with geometric mean IC50s of 114.25 and 120.5 nM, respectively, for Bangladesh and western Thailand. Most isolates from both sites were sensitive to quinine, and all were sensitive to artesunate. Many isolates were considered in vitro resistant to mefloquine, but the geometric mean IC50 for the Thai isolates (98.79 nM) was 1.6 times (P 0.002) higher than that of isolates from Bangladesh (60.3 nM). The high prevalence of in vitro mefloquine resistance in Bangladesh suggests that close surveillance is necessary to delay widespread multidrug resistant problems in the area.

Rickettsial Illnesses as Important Causes of Febrile Illness in Chittagong, Bangladesh.

Abstract: We conducted a yearlong prospective study of febrile patients admitted to a tertiary referral hospital in Chittagong, Bangladesh, to assess the proportion of patients with rickettsial illnesses and identify the causative pathogens, strain genotypes, and associated seasonality patterns. We diagnosed scrub typhus in 16.8% (70/416) and murine typhus in 5.8% (24/416) of patients; 2 patients had infections attributable to undifferentiated Rickettsia spp. and 2 had DNA sequence-confirmed R. felis infection. Orientia tsutsugamushi genotypes included Karp, Gilliam, Kato, and TA763-like strains, with a prominence of Karp-like strains. Scrub typhus admissions peaked in a biphasic pattern before and after the rainy season, whereas murine typhus more frequently occurred before the rainy season. Death occurred in 4% (18/416) of cases; case-fatality rates were 4% each for scrub typhus (3/70) and murine typhus (1/28). Overall, 23.1% (96/416) of patients had evidence of treatable rickettsial illnesses, providing important evidence toward optimizing empirical treatment strategies.

Diagnostic Accuracy of the InBios Scrub Typhus Detect™ ELISA for the Detection of IgM Antibodies in Chittagong, Bangladesh

Abstract: Here we estimated the accuracy of the InBios Scrub Typhus Detect™ immunoglobulin M (IgM) ELISA to determine the optimal optical density (OD) cut-off values for the diagnosis of scrub typhus Patients with undifferentiated febrile illness from Chittagong, Bangladesh, provided samples for reference testing using (i) qPCR using the Orientia spp 47-kDa htra gene, (ii) IFA ≥1:3200 on admission, (iii) immunofluorescence assay (IFA) ≥1:3200 on admission or 4-fold rise to ≥3200, and (iv) combination of PCR and IFA positivity For sero-epidemiological purposes (ELISA vs IFA ≥1:3200 on admission or 4-fold rise to ≥3200), the OD cut-off for admission samples was ≥125, resulting in a sensitivity (Sn) of 915 (95% confidence interval (95% CI: 968–825) and a specificity (Sp) of 924 (95% CI: 950–890), while for convalescent samples the OD cut-off was ≥150 with Sn of 660 (95% CI: 785–517) and Sp of 960 (95% CI: 983–923) Comparisons against comparator reference tests (ELISA vs all tests including PCR) indicated the most appropriate cut-off OD to be within the range of 075–125 For admission samples, the best Sn/Sp compromise was at 125 OD (Sn 915%, Sp 924%) and for convalescent samples at 075 OD (Sn 698%, Sp 895%) A relatively high (stringent) diagnostic cut-off value provides increased diagnostic accuracy with high sensitivity and specificity in the majority of cases, while lowering the cut-off runs the risk of false positivity This study underlines the need for regional assessment of new diagnostic tests according to the level of endemicity of the disease given the high levels of residual or cross-reacting antibodies in the general population

Genotypic and phenotypic characterization of G6PD deficiency in Bengali adults with severe and uncomplicated malaria

Abstract: Control of malaria increasingly involves administration of 8-aminoquinolines, with accompanying risk of haemolysis in individuals with glucose-6-phosphate dehydrogenase (G6PD) deficiency. Few data on the prevalence and genotypic basis of G6PD deficiency are available from Bangladesh, where malaria remains a major problem in the South (Chittagong Division). The aim of this study was to determine the prevalence of G6PD deficiency, and associated G6PD genotypes, in adults with falciparum malaria in southern Bangladesh. G6PD status was assessed via a combination of fluorescent spot testing (FST) and genotyping in 141 Bengali patients admitted with falciparum malaria to two centres in Chittagong Division from 2012 to 2014. In addition, an analysis of genomic data from 1000 Genomes Project was carried out among five healthy Indian subcontinent populations. One male patient with uncomplicated malaria was found to have G6PD deficiency on FST and a genotype associated with deficiency (hemizygous Orissa variant). In addition, there were two female patients heterozygous for deficiency variants (Orissa and Kerala-Kalyan). These three patients had a relatively long duration of symptoms prior to admission compared to G6PD normal cases, possibly suggesting an interaction with parasite multiplication rate. In addition, one of 27 healthy local controls was deficient on FST and hemizygous for the Mahidol variant of G6PD deficiency. Examination of 1000 Genomes Project sequencing data across the Indian subcontinent showed that 19/723 chromosomes (2.63%) carried a variant associated with deficiency. In the Bengali from Bangladesh 1000 Genomes population, three of 130 chromosomes (2.31%) carried deficient alleles; this included single chromosomes carrying the Kerala-Kalyan and Orissa variants. In line with other recent work, G6PD deficiency is uncommon in Bengalis in Bangladesh. Further studies of particular ethnic groups are needed to evaluate the potential risk of wide deployment of primaquine in malaria control efforts in Bangladesh.

Fluorine and Fluorinated Motifs in the Design and Application of Bioisosteres for Drug Design.

Abstract: The electronic properties and relatively small size of fluorine endow it with considerable versatility as a bioisostere and it has found application as a substitute for lone pairs of electrons, the hydrogen atom, and the methyl group while also acting as a functional mimetic of the carbonyl, carbinol, and nitrile moieties. In this context, fluorine substitution can influence the potency, conformation, metabolism, membrane permeability, and P-gp recognition of a molecule and temper inhibition of the hERG channel by basic amines. However, as a consequence of the unique properties of fluorine, it features prominently in the design of higher order structural metaphors that are more esoteric in their conception and which reflect a more sophisticated molecular construction that broadens biological mimesis. In this Perspective, applications of fluorine in the construction of bioisosteric elements designed to enhance the in vitro and in vivo properties of a molecule are summarized.

Glucose-6-phosphate dehydrogenase deficiency.

Abstract: Glucose-6-phosphate dehydrogenase deficiency is a genetic disorder that occurs almost exclusively in males. This condition mainly affects red blood cells, which carry oxygen from the lungs to tissues throughout the body. In affected individuals, a defect in an enzyme called glucose-6-phosphate dehydrogenase causes red blood cells to break down prematurely. This destruction of red blood cells is called hemolysis.

Uncovering the essential genes of the human malaria parasite Plasmodium falciparum by saturation mutagenesis

Abstract: INTRODUCTION Malaria remains a devastating global parasitic disease, with the majority of malaria deaths caused by the highly virulent Plasmodium falciparum . The extreme AT-bias of the P. falciparum genome has hampered genetic studies through targeted approaches such as homologous recombination or CRISPR-Cas9, and only a few hundred P. falciparum mutants have been experimentally generated in the past decades. In this study, we have used high-throughput piggyBac transposon insertional mutagenesis and quantitative insertion site sequencing (QIseq) to reach saturation-level mutagenesis of this parasite. RATIONALE Our study exploits the AT-richness of the P. falciparum genome, which provides numerous piggyBac transposon insertion targets within both gene coding and noncoding flanking sequences, to generate more than 38,000 P. falciparum mutants. At this level of mutagenesis, we could distinguish essential genes as nonmutable and dispensable genes as mutable. Subsequently, we identified 2680 genes essential for in vitro asexual blood-stage growth. RESULTS We calculated mutagenesis index scores (MISs) and mutagenesis fitness scores (MFSs) in order to functionally define the relative fitness cost of disruption for 5399 genes. A competitive growth phenotype screen confirmed that MIS and MFS were predictive of the fitness cost for in vitro asexual growth. Genes predicted to be essential included genes implicated in drug resistance—such as the “ K13 ” Kelch propeller, mdr , and dhfr-ts —as well as targets considered to be high value for drugs development, such as pkg and cdpk5 . The screen revealed essential genes that are specific to human Plasmodium parasites but absent from rodent-infective species, such as lipid metabolic genes that may be crucial to transmission commitment in human infections. MIS and MFS profiling provides a clear ranking of the relative essentiality of gene ontology (GO) functions in P. falciparum . GO pathways associated with translation, RNA metabolism, and cell cycle control are more essential, whereas genes associated with protein phosphorylation, virulence factors, and transcription are more likely to be dispensable. Last, we confirm that the proteasome-degradation pathway is a high-value druggable target on the basis of its high ratio of essential to dispensable genes, and by functionally confirming its link to the mode of action of artemisinin, the current front-line antimalarial. CONCLUSION Saturation-scale mutagenesis allows prioritization of intervention targets in the genome of the most important cause of malaria. The identification of more than 2680 essential genes, including ~1000 Plasmodium -conserved essential genes, will be valuable for antimalarial therapeutic research.

K13-propeller mutations confer artemisinin resistance in Plasmodium falciparum clinical isolates

Abstract: The emergence of artemisinin resistance in Southeast Asia imperils efforts to reduce the global malaria burden. We genetically modified the Plasmodium falciparum K13 locus using zinc-finger nucleases and measured ring-stage survival rates after drug exposure in vitro; these rates correlate with parasite clearance half-lives in artemisinin-treated patients. With isolates from Cambodia, where resistance first emerged, survival rates decreased from 13 to 49% to 0.3 to 2.4% after the removal of K13 mutations. Conversely, survival rates in wild-type parasites increased from ≤0.6% to 2 to 29% after the insertion of K13 mutations. These mutations conferred elevated resistance to recent Cambodian isolates compared with that of reference lines, suggesting a contemporary contribution of additional genetic factors. Our data provide a conclusive rationale for worldwide K13-propeller sequencing to identify and eliminate artemisinin-resistant parasites.

Artemisinin—A Gift from Traditional Chinese Medicine to the World (Nobel Lecture)

Abstract: Malaria has long been a devastating and life-threatening global epidemic disease in human history. Artemisinin, the active substance against malaria, was first isolated and tested in the 1970s in China. The important role played by traditional Chinese medicine in the discovery of artemisinin is described by Y. Tu in her Nobel Lecture.