Rapid epidemiologic assessment of glucose-6-phosphate dehydrogenase deficiency in malaria-endemic areas in Southeast Asia using a novel diagnostic kit

Plasmodium knowlesi (Pk) Malaria: A Review & Proposal of Therapeutically Rational Exchange (T-REX) of Pk-Resistant Red Blood Cells

Plasmodium knowlesi (Pk) causes zoonotic malaria and is known as the "fifth human malaria parasite". Pk malaria is an emerging threat because infections are increasing and can be fatal. While most infections are in Southeast Asia (SEA), especially Malaysia, travelers frequently visit this region and can present with Pk malaria around the world. So, clinicians need to know (1) patients who present with fever after recent travel to SEA might be infected with Pk and (2) Pk is often misdiagnosed as P. malariae (which typically causes less severe malaria). Here we review the history, pathophysiology, clinical features, diagnosis, and treatment of Pk malaria. Severe disease is most common in adults. Signs and symptoms can include fever, abdominal pain, jaundice, acute kidney injury, acute respiratory distress syndrome, hyponatremia, hyperparasitemia, and thrombocytopenia. Dengue is one of the diseases to be considered in the differential. Regarding pathophysiologic mechanisms, when Pk parasites invade mature red blood cells (RBCs, i.e., normocytes) and reticulocytes, changes in the red blood cell (RBC) surface can result in life-threatening cytoadherence, sequestration, and reduced RBC deformability. Since molecular mechanisms involving the erythrocytic stage are responsible for onset of severe disease and lethal outcomes, it is biologically plausible that manual exchange transfusion (ET) or automated RBC exchange (RBCX) could be highly beneficial by replacing "sticky" parasitized RBCs with uninfected, deformable, healthy donor RBCs. Here we suggest use of special Pk-resistant donor RBCs to optimize adjunctive manual ET/RBCX for malaria. "Therapeutically-rational exchange transfusion" (T-REX) is proposed in which Pk-resistant RBCs are transfused (instead of disease-promoting RBCs). Because expression of the Duffy antigen on the surface of human RBCs is essential for parasite invasion, T-REX of Duffy-negative RBCs-also known as Fy(a-b-) RBCs-could replace the majority of the patient's circulating normocytes with Pk invasion-resistant RBCs (in a single procedure lasting about 2 h). When sequestered or non-sequestered iRBCs rupture-in a 24 h Pk asexual life cycle-the released merozoites cannot invade Fy(a-b-) RBCs. When Fy(a-b-) RBC units are scarce (e.g., in Malaysia), clinicians can consider the risks and benefits of transfusing plausibly Pk-resistant RBCs, such as glucose-6-phosphate dehydrogenase deficient (G6PDd) RBCs and Southeast Asian ovalocytes (SAO). Patients typically require a very short recovery time (<1 h) after the procedure. Fy(a-b-) RBCs should have a normal lifespan, while SAO and G6PDd RBCs may have mildly reduced half-lives. Because SAO and G6PDd RBCs come from screened blood donors who are healthy and not anemic, these RBCs have a low-risk for hemolysis and do not need to be removed after the patient recovers from malaria. T-REX could be especially useful if (1) antimalarial medications are not readily available, (2) patients are likely to progress to severe disease, or (3) drug-resistant strains emerge. In conclusion, T-REX is a proposed optimization of manual ET/RBCX that has not yet been utilized but can be considered by physicians to treat Pk malaria patients.

Prevalence of G6PD deficiency and diagnostic accuracy of a G6PD point-of-care test among a population at risk of malaria in Myanmar

BACKGROUND

Over the past decade, the incidence of malaria has steadily declined in Myanmar, with Plasmodium vivax becoming predominant. The resilience of P. vivax to malaria control is attributed to the parasite's ability to form hypnozoites in the host's liver, which can cause relapse. Primaquine is used to eliminate hypnozoites but can cause haemolysis in glucose-6-phosphate dehydrogenase (G6PD)-deficient individuals. It is thus necessary to estimate the frequency and variant types of G6PD deficiency in areas where primaquine will be widely used for P. vivax elimination.

METHODS

In this study, a descriptive cross-sectional survey was conducted to determine the prevalence of G6PD deficiency in a population residing in Nay Pyi Taw, Myanmar, using a standard spectrophotometric assay, a rapid diagnostic test (RDT), Biosensor, and by genotyping G6PD variants.

RESULTS

G6PD enzyme activity was determined from 772 leukocyte-depleted samples, with an adjusted male median G6PD activity value of 6.3 U/g haemoglobin. Using a cut-off value of 30% enzyme activity, the overall prevalence of G6PD deficiency was 10.8%. Genotyping of G6PD variants was performed for 536 samples, of which 131 contained mutations. The Mahidol variant comprised the majority, and males with the Mahidol variant showed lower G6PD enzyme activity. The G6PD Andalus variant, which has not been reported in Myanmar before, was also identified in this study.

CONCLUSION

This study provides a G6PD enzyme activity reference value for the Myanmar population and further information on the prevalence and variants of G6PD deficiency among the Myanmar population; it also evaluates the feasibility of G6PD deficiency tests.

G6PD deficiency among malaria-infected national groups at the western part of Myanmar with implications for primaquine use in malaria elimination

BACKGROUND

Glucose 6-phosphate dehydrogenase deficiency (G6PDd) plays a central role in readiness assessment for malaria elimination in Myanmar by 2030 that includes primaquine (PQ) use. The risk of hemolysis in G6PDd individuals hampers the widespread use of primaquine safely in malaria-infected patients. In the pre-elimination era, it is important to screen initially for asymptomatic malaria in combination with G6PD deficiency by applying more sensitive diagnostic tools. Therefore, this study examined the proportion of G6PDd and the distribution of G6PD genotypes among malaria-infected national groups in Myanmar before initiation of malaria elimination strategies.

METHODS

A cross-sectional study in one township each with high malaria burden from two states in the western part of Myanmar, was conducted during 2016-2018, and 320 participants (164 Rakhine and 156 Chin National groups) were recruited. We used RDT and ultrasensitive polymerase chain reaction (us PCR) method to confirm malaria infection, and a G6PD RDT(CareStart) to detect G6PDd and PCR/restriction fragment length polymorphism (RFLP) method to confirm the variant of G6PDd for genotyping. G6PD enzyme activity was measured by G6PD Biosensor (CareStart).

RESULTS

Malaria positivity rates detected by RDT were lower than those detected by us PCR in the combined samples [13% (42/320) vs. 21% (67/320)] as well as in the Rakhine samples [17% (28/164) vs. 25% (41/164)] and in Chin samples [9% (14/156) vs. 17% (26/156)]. G6PD deficiency rates were approximately 10% in both the combined samples and specific national groups. For G6PD enzyme activity in the combined samples, G6PDd (defined as < 30% of adjusted male median) was 10% (31/320) and severe G6PDd (< 10% of AMM) was 3% (9/320). Among malaria-infected patients with positive by both RDT and usPCR, G6PDd was less than 20% in each national group. G6PD genotyping showed that the G6PD Mahidol (G487A) was the major variant.

CONCLUSIONS

The varying degree of G6PDd detected among malaria-infected national groups by advanced diagnostic tools, strongly support the recommend G6PD testing by the National Malaria Control Program and the subsequent safe treatment of P. vivax by primaquine for radical cure. Establishing a field monitoring system to achieve timely malaria elimination is mandatory to observe the safety of patients after PQ treatment.

The integrity and stability of specimens under different storage conditions for glucose-6-phosphate dehydrogenase deficiency screening using WST-8

Accurate measurement of glucose-6-phosphate dehydrogenase (G6PD) activity is critical for malaria treatment as misclassification of G6PD deficiency could cause serious harm to patients. G6PD activity should be assessed in blood samples on the day of collection. Otherwise, specimens should be stored under suitable conditions to prevent loss of G6PD activity. Here, we assessed stability and integrity of G6PD testing in samples from normal controls, heterozygous females, and G6PD deficient individuals using water-soluble tetrazolium salts (WST-8) assay. Specimens were stored as ethylenediaminetetraacetic acid (EDTA) whole blood and dried blood spots (DBS) at various temperatures (37 °C, room temperature, 4 °C and -20 °C) and under different humidity conditions (with and without desiccant). G6PD normal samples were stable for up to 1 year when stored at -20 °C under controlled conditions, with 85% and 91% G6PD activity in EDTA whole blood and DBS in the presence of desiccant, respectively. Specimens from heterozygous females showed greater G6PD activity when stored as DBS, with 85% enzyme activity after 1 year of storage at -20 °C under controlled conditions in the presence of desiccant. G6PD deficient samples rapidly lost enzyme activity in all storage conditions tested. However, the reduction in G6PD enzyme activity in G6PD deficient samples did not interfere with G6PD classification. Samples stored under suitable conditions for G6PD testing will allow accurate measurement of enzyme activity, prevent misclassification of G6PD deficiency and enable safe and effective use of antimalarial drugs such as primaquine and tafenoquine.

Glucose-6-phosphate dehydrogenase mutations in malaria endemic area of Thailand by multiplexed high-resolution melting curve analysis

Background

Glucose-6-phosphate dehydrogenase (G6PD) deficiency, the most common enzymopathy in humans, is prevalent in tropical and subtropical areas where malaria is endemic. Anti-malarial drugs, such as primaquine and tafenoquine, can cause haemolysis in G6PD-deficient individuals. Hence, G6PD testing is recommended before radical treatment against vivax malaria. Phenotypic assays have been widely used for screening G6PD deficiency, but in heterozygous females, the random lyonization causes difficulty in interpreting the results. Over 200 G6PD variants have been identified, which form genotypes associated with differences in the degree of G6PD deficiency and vulnerability to haemolysis. This study aimed to assess the frequency of G6PD mutations using a newly developed molecular genotyping test.

Methods

A multiplexed high-resolution melting (HRM) assay was developed to detect eight G6PD mutations, in which four mutations can be tested simultaneously. Validation of the method was performed using 70 G6PD-deficient samples. The test was then applied to screen 725 blood samples from people living along the Thai–Myanmar border. The enzyme activity of these samples was also determined using water-soluble tetrazolium salts (WST-8) assay. Then, the correlation between genotype and enzyme activity was analysed.

Results

The sensitivity of the multiplexed HRM assay for detecting G6PD mutations was 100 % [95 % confidence interval (CI): 94.87–100 %] with specificity of 100 % (95 % CI: 87.66–100 %). The overall prevalence of G6PD deficiency in the studied population as revealed by phenotypic WST-8 assay was 20.55 % (149/725). In contrast, by the multiplexed HRM assay, 27.17 % (197/725) of subjects were shown to have G6PD mutations. The mutations detected in this study included four single variants, G6PD Mahidol (187/197), G6PD Canton (4/197), G6PD Viangchan (3/197) and G6PD Chinese-5 (1/197), and two double mutations, G6PD Mahidol + Canton (1/197) and G6PD Chinese-4 + Viangchan (1/197). A broad range of G6PD enzyme activities were observed in individuals carrying G6PD Mahidol, especially in females.

Conclusions

The multiplexed HRM-based assay is sensitive and reliable for detecting G6PD mutations. This genotyping assay can facilitate the detection of heterozygotes, which could be useful as a supplementary approach for high-throughput screening of G6PD deficiency in malaria endemic areas before the administration of primaquine and tafenoquine.

Associations between red blood cell variants and malaria among children and adults from three areas of Uganda: a prospective cohort study

Background

Multiple red blood cell (RBC) variants appear to offer protection against the most severe forms of Plasmodium falciparum malaria. Associations between these variants and uncomplicated malaria are less clear.

Methods

Data from a longitudinal cohort study conducted in 3 sub-counties in Uganda was used to quantify associations between three red blood cell variants Hb [AA, AS, S (rs334)], alpha thalassaemia 3.7 kb deletion, and glucose-6-phosphate dehydrogenase deficiency A—(G6PD 202A genotype) and malaria incidence, parasite prevalence, parasite density (a measure of anti-parasite immunity) and body temperature adjusted for parasite density (a measure of anti-disease immunity). All analyses were adjusted for age, average household entomological inoculation rate, and study site. Results for all variants were compared to those for wild type genotypes.

Results

In children, HbAS was associated, compared to wild type, with a lower incidence of malaria (IRR = 0.78, 95% CI 0.66–0.92, p = 0.003), lower parasite density upon infection (PR = 0.66, 95% CI 0.51–0.85, p = 0.001), and lower body temperature for any given parasite density (− 0.13 ℃, 95% CI − 0.21, − 0.05, p = 0.002). In children, HbSS was associated with a lower incidence of malaria (IRR = 0.17, 95% CI 0.04–0.71, p = 0.02) and lower parasite density upon infection (PR = 0.31, 95% CI 0.18–0.54, p < 0.001). α−/αα thalassaemia, was associated with higher parasite prevalence in both children and adults (RR = 1.23, 95% CI 1.06–1.43, p = 0.008 and RR = 1.52, 95% CI 1.04–2.23, p = 0.03, respectively). G6PD deficiency was associated with lower body temperature for any given parasite density only among male hemizygote children (− 0.19 ℃, 95% CI − 0.31, − 0.06, p = 0.003).

Conclusion

RBC variants were associated with non-severe malaria outcomes. Elucidation of the mechanisms by which they confer protection will improve understanding of genetic protection against malaria.

Evaluation of quantitative biosensor for glucose-6-phosphate dehydrogenase activity detection

Neonatal jaundice is a common and severe disease in premature infants with Glucose-6-Phosphate Dehydrogenase (G-6-PD) deficiency. The World Health Organization (WHO) has recommended screening for G-6-PD deficiency in newborns for early recognition as well as to prevent unwanted outcomes in a timely manner. The present study aimed to assess a point-of-care, careSTARTTM G6PD biosensor as a quantitative method for the diagnosis of G-6-PD deficiency. Factors influencing the evaluation of G-6-PD enzyme activity were examined in 40 adults, including ethylenediaminetetraacetic acid (EDTA) anticoagulant, hematocrit concentration, storage temperature and time. Analytic performance of the careSTARTTM G6PD biosensor was evaluated in 216 newborns and compared with fluorescent spot test (FST) and standard quantitative G-6-PD enzyme activity (SGT) assay. The results of factors affecting the G-6-PD enzyme activity showed that the activity determined from finger-prick was not statistically different from venous blood (p = 0.152). The G-6-PD value was highly dependent on the hematocrit and rose with increasing hematocrit concentration. Its activity was stable at 4°C for 3 days. Reliability analysis between the careSTARTTM G6PD biosensor and SGT assay showed a strong correlation with a Pearson's correlation coefficient of 0.82 and perfect agreement by intraclass correlation coefficient (ICC) of 0.90. Analysis of the area under the Receiver Operating Curve (AUC) illustrated that the careSTARTTM G6PD biosensor had 100% sensitivity, 96% specificity, 73% positive predictive value (PPV), 100% negative predictive value (NPV) and 97% accuracy at 30% of residual activity. While the diagnostic ability for identifying G-6-PD deficiency had 78% sensitivity, 89% specificity, 56% positive predictive value (PPV), 96% negative predictive value (NPV) and 88% accuracy when stratified by gender. The careSTARTTM G6PD biosensor is an attractive option as a point-of-care quantitative method for G-6-PD activity detection. Quantification of G-6-PD enzyme activity in newborns is the most effective approach for the management of G-6-PD deficiency to prevent severe jaundice and acute hemolysis.

MTT FORMAZAN REPLACED WST-8 AS A BETTER SIMPLE SCREENING METHOD FOR DETECTION OF GLUCOSE-6-PHOSPHATE DEHYDROGENASE DEFICIENCY

We have previously developed the WST-8 method as a simple and rapid screening test for detection of glucose-6-phosphate dehydrogenase (G6PD) deficiency accomplished by the naked eye. However, it was little difficult to distinguish between faint orange colors developed by heterozygous females and pink colors of normal hemolyzed blood, since both have similar tones. To solve this problem, we established a new and simple screening method that utilizes another formazan substrate, MTT (3-(4,5-dimethyl-2- thiazolyl)-2,5-diphenyl-2H tetrazolium bromide) in combination with a hydrogen carrier, 1-methoxy phenazine methosulfate. MTT formazan exhibits a purple color, thus allowing for the ability to easily distinguish the pink colors of hemolyzed blood. However, MTT has been reported to react with hemoglobin non-specifically and to interfere with the interpretation of the color reaction. In our examinations by mixing MTT with hemolyzed blood, we found that the non-specific reaction was very slow, and that the addition of a small amount of blood (5~10 μl) into a reaction mixture (800 μl) did not interfere with the reaction of G6PD activity. In this new MTT method, a strong purple color was generated in normal blood samples at 20~30 min after incubation, which could be distinguished by the naked eye from G6PD-deficient blood samples with less than 50% residual activity. In addition, quantitative measurement using a spectrophotometer was also possible despite the fact that MTT formazan is water-insoluble.

Association of glucose-6-phosphate dehydrogenase deficiency and malaria: a systematic review and meta-analysis

Glucose-6-Phosphate Dehydrogenase (G6PD) deficiency overlaps with malaria endemicity although it predisposes carriers to hemolysis. This fact supports the protection hypothesis against malaria. The aim of this systematic review is to assess the presence and the extent of protective association between G6PD deficiency and malaria. Thirteen databases were searched for papers reporting any G6PD alteration in malaria patients. Twenty-eight of the included 30 studies were eligible for the meta-analysis. Results showed absence of negative association between G6PD deficiency and uncomplicated falciparum malaria (odds ratio (OR), 0.77; 95% confidence interval (CI), 0.59-1.02; p = 0.07). However, this negative association happened in Africa (OR, 0.59; 95% CI, 0.40-0.86; p = 0.007) but not in Asia (OR, 1.24; 95% CI, 0.96-1.61; p = 0.10), and in the heterozygotes (OR, 0.70; 95% CI, 0.57-0.87; p = 0.001) but not the homo/hemizygous (OR, 0.70; 95% CI, 0.46-1.07; p = 0.10). There was no association between G6PD deficiency and total severe malaria (OR, 0.82; 95% CI, 0.61-1.11; p = 0.20). Similarly, there was no association with other malaria species. G6PD deficiency can potentially protect against uncomplicated malaria in African countries, but not severe malaria. Interestingly, this protection was mainly in heterozygous, being x-linked thus related to gender.

G6PD testing in support of treatment and elimination of malaria: recommendations for evaluation of G6PD tests

Malaria elimination will be possible only with serious attempts to address asymptomatic infection and chronic infection by both Plasmodium falciparum and Plasmodium vivax. Currently available drugs that can completely clear a human of P. vivax (known as "radical cure"), and that can reduce transmission of malaria parasites, are those in the 8-aminoquinoline drug family, such as primaquine. Unfortunately, people with glucose-6-phosphate dehydrogenase (G6PD) deficiency risk having severe adverse reactions if exposed to these drugs at certain doses. G6PD deficiency is the most common human enzyme defect, affecting approximately 400 million people worldwide.Scaling up radical cure regimens will require testing for G6PD deficiency, at two levels: 1) the individual level to ensure safe case management, and 2) the population level to understand the risk in the local population to guide Plasmodium vivax treatment policy. Several technical and operational knowledge gaps must be addressed to expand access to G6PD deficiency testing and to ensure that a patient's G6PD status is known before deciding to administer an 8-aminoquinoline-based drug.In this report from a stakeholder meeting held in Thailand on October 4 and 5, 2012, G6PD testing in support of radical cure is discussed in detail. The focus is on challenges to the development and evaluation of G6PD diagnostic tests, and on challenges related to the operational aspects of implementing G6PD testing in support of radical cure. The report also describes recommendations for evaluation of diagnostic tests for G6PD deficiency in support of radical cure.

Review of key knowledge gaps in glucose-6-phosphate dehydrogenase deficiency detection with regard to the safe clinical deployment of 8-aminoquinoline treatment regimens: a workshop report

The diagnosis and management of glucose-6-phosphate dehydrogenase (G6PD) deficiency is a crucial aspect in the current phases of malaria control and elimination, which will require the wider use of 8-aminoquinolines for both reducing Plasmodium falciparum transmission and achieving the radical cure of Plasmodium vivax. 8-aminoquinolines, such as primaquine, can induce severe haemolysis in G6PD-deficient individuals, potentially creating significant morbidity and undermining confidence in 8-aminoquinoline prescription. On the other hand, erring on the side of safety and excluding large numbers of people with unconfirmed G6PD deficiency from treatment with 8-aminoquinolines will diminish the impact of these drugs. Estimating the remaining G6PD enzyme activity is the most direct, accessible, and reliable assessment of the phenotype and remains the gold standard for the diagnosis of patients who could be harmed by the administration of primaquine. Genotyping seems an unambiguous technique, but its use is limited by cost and the large range of recognized G6PD genotypes. A number of enzyme activity assays diagnose G6PD deficiency, but they require a cold chain, specialized equipment, and laboratory skills. These assays are impractical for care delivery where most patients with malaria live. Improvements to the diagnosis of G6PD deficiency are required for the broader and safer use of 8-aminoquinolines to kill hypnozoites, while lower doses of primaquine may be safely used to kill gametocytes without testing. The discussions and conclusions of a workshop conducted in Incheon, Korea in May 2012 to review key knowledge gaps in G6PD deficiency are reported here.

Clinical spectrum and severity of hemolytic anemia in glucose 6-phosphate dehydrogenase-deficient children receiving dapsone

Drug-induced acute hemolytic anemia led to the discovery of G6PD deficiency. However, most clinical data are from isolated case reports. In 2 clinical trials of antimalarial preparations containing dapsone (4,4'-diaminodiphenylsulfone; 2.5 mg/kg once daily for 3 days), 95 G6PD-deficient hemizygous boys, 24 G6PD-deficient homozygous girls, and 200 girls heterozygous for G6PD deficiency received this agent. In the first 2 groups, there was a maximum decrease in hemoglobin averaging -2.64 g/dL (range -6.70 to +0.30 g/dL), which was significantly greater than for the comparator group receiving artemether-lumefantrine (adjusted difference -1.46 g/dL; 95% confidence interval -1.76, -1.15). Hemoglobin concentrations were decreased by ≥ 40% versus pretreatment in 24/119 (20.2%) of the G6PD-deficient children; 13/119 (10.9%) required blood transfusion. In the heterozygous girls, the mean maximum decrease in hemoglobin was -1.83 g/dL (range +0.90 to -5.20 g/dL); 1 in 200 (0.5%) required blood transfusion. All children eventually recovered. All the G6PD-deficient children had the G6PD A- variant, ie, mutations V68M and N126D. Drug-induced acute hemolytic anemia in G6PD A- subjects can be life-threatening, depending on the nature and dosage of the drug trigger. Therefore, contrary to current perception, in clinical terms the A- type of G6PD deficiency cannot be regarded as mild. This study is registered at http://www.clinicaltrials.gov as NCT00344006 and NCT00371735.

A novel cytofluorometric assay for the detection and quantification of glucose-6-phosphate dehydrogenase deficiency

Glucose-6-phosphate dehydrogenase (G6PD) deficiency is an X-linked enzymopathy that affects hundreds of millions of people worldwide, conferring increased risk of neonatal jaundice and oxidant-induced hemolytic anemia. Screening and diagnosis of G6PD deficiency is currently performed using genetic or biochemical assays, the former being cost ineffective in populations with significant allelic heterogeneity, and the latter being limited in ability to detect female heterozygotes. Cytochemical assays can obviate these shortcomings, but at the expense of added technical complexity and labor. We describe here a simple, novel cytofluorometric method that extends the classic methemoglobin reduction test, assessing G6PD deficiency at the level of an individual erythrocyte. In preliminary testing in Malian children, there was strong concordance between our method and established genetic and biochemical techniques. The assay is robust and economical, and could serve as a screening method as well as a research tool, especially for high-throughput applications such as flow cytometry.

Predicting the Kinetic Properties Associated with Redox Imbalance after Oxidative Crisis in G6PD-Deficient Erythrocytes: A Simulation Study

It is well known that G6PD-deficient individuals are highly susceptible to oxidative stress. However, the differences in the degree of metabolic alterations among patients during an oxidative crisis have not been extensively studied. In this study, we applied mathematical modeling to assess the metabolic changes in erythrocytes of various G6PD-deficient patients during hydrogen peroxide- (H(2)O(2)-) induced perturbation and predict the kinetic properties that elicit redox imbalance after exposure to an oxidative agent. Simulation results showed a discrepancy in the ability to restore regular metabolite levels and redox homeostasis among patients. Two trends were observed in the response of redox status (GSH/GSSG) to oxidative stress, a mild decrease associated with slow recovery and a drastic decline associated with rapid recovery. The former was concluded to apply to patients with severe clinical symptoms. Low V(max) and high K(mG6P) of G6PD were shown to be kinetic properties that enhance consequent redox imbalance.

Malaria distribution, prevalence, drug resistance and control in Indonesia

Approximately 230 million people live in Indonesia. The country is also home to over 20 anopheline vectors of malaria which transmit all four of the species of Plasmodium that routinely infect humans. A complex mosaic of risk of infection across this 5000-km-long archipelago of thousands of islands and distinctive habitats seriously challenges efforts to control malaria. Social, economic and political dimensions contribute to these complexities. This chapter examines malaria and its control in Indonesia, from the earliest efforts by malariologists of the colonial Netherlands East Indies, through the Global Malaria Eradication Campaign of the 1950s, the tumult following the coup d'état of 1965, the global resurgence of malaria through the 1980s and 1990s and finally through to the decentralization of government authority following the fall of the authoritarian Soeharto regime in 1998. We detail important methods of control and their impact in the context of the political systems that supported them. We examine prospects for malaria control in contemporary decentralized and democratized Indonesia with multidrug-resistant malaria and greatly diminished capacities for integrated malaria control management programs.

Population screening for glucose-6-phosphate dehydrogenase deficiencies in Isabel Province, Solomon Islands, using a modified enzyme assay on filter paper dried bloodspots

Background

Glucose-6-phosphate dehydrogenase deficiency poses a significant impediment to primaquine use for the elimination of liver stage infection with Plasmodium vivax and for gametocyte clearance, because of the risk of life-threatening haemolytic anaemia that can occur in G6PD deficient patients. Although a range of methods for screening G6PD deficiency have been described, almost all require skilled personnel, expensive laboratory equipment, freshly collected blood, and are time consuming; factors that render them unsuitable for mass-screening purposes.

Methods

A published WST8/1-methoxy PMS method was adapted to assay G6PD activity in a 96-well format using dried blood spots, and used it to undertake population screening within a malaria survey undertaken in Isabel Province, Solomon Islands. The assay results were compared to a biochemical test and a recently marketed rapid diagnostic test.

Results

Comparative testing with biochemical and rapid diagnostic test indicated that results obtained by filter paper assay were accurate providing that blood spots were assayed within 5 days when stored at ambient temperature and 10 days when stored at 4 degrees. Screening of 8541 people from 41 villages in Isabel Province, Solomon Islands revealed the prevalence of G6PD deficiency as defined by enzyme activity < 30% of normal control was 20.3% and a prevalence of severe deficiency that would predispose to primaquine-induced hemolysis (WHO Class I-II) of 6.9%.

Conclusions

The assay enabled simple and quick semi-quantitative population screening in a malaria-endemic region. The study indicated a high prevalence of G6PD deficiency in Isabel Province and highlights the critical need to consider G6PD deficiency in the context of P. vivax malaria elimination strategies in Solomon Islands, particularly in light of the potential role of primaquine mass drug administration.

Deficiencia de glucosa 6-fostato deshidrogenasa en hombres sanos y en pacientes maláricos; Turbo (Antioquia, Colombia)

INTRODUCCIÓN: En América Latina la deficiencia de glucosa 6-fosfato deshidrogenasa (d-G6PD) ha sido poco estudiada y en Colombia solo conocemos tres publicaciones antiguas. Urge conocer más la prevalencia de d-G6PD, sobre todo ahora que el tratamiento de la malaria vivax plantea aumentar la dosis diaria o total de primaquina. OBJETIVO: Medir la prevalencia de d-G6PD en poblaciones masculina sana y de enfermos con malaria por Plasmodium vivax, en Turbo (Urabá, departamento de Antioquia, Colombia). METODOLOGÍA: Encuestas de prevalencia, para evaluar la G6PD en dos poblaciones de Turbo (Antioquia): hombres sanos; hombres y mujeres con malaria vivax. Se trabajó con muestras diseñadas con criterios estadístico-epidemiológicos. La actividad enzimática se midió con el método normalizado de Beutler para valorar la G6PD en hemolizados. RESULTADOS: Entre los hombres sanos (n = 508), el intervalo de confianza 95% para el promedio (IC95%) estuvo entre 4,15 y 4,51 UI/g hemoglobina y 14,8% presentaron valores por debajo del "límite normal" de < 2,29 UI/g hemoglobina (prevalencia de d-G6PD). Entre los hombres con malaria (n = 206) el IC95% fue 3,81 a 4,16 UI/g hemoglobina y entre las mujeres palúdicas fue 3,86 a 4,20 UI/g hemoglobina. Los promedios masculinos (sanos vs. maláricos) fueron estadísticamente diferentes (p = 0,028). Únicamente 9,5% (13/137) de los enfermos con paludismo, todos de sexo masculino, presentaron d-G6PD. CONCLUSIONES: la d-G6PD es relativamente alta (14,8%) en la población masculina sana de Turbo y en los enfermos maláricos por P. vivax (9,5%, todos hombres).

Glucose-6-phosphate dehydrogenase deficiency

Glucose-6-phosphate dehydrogenase (G6PD) deficiency is the most common human enzyme defect, being present in more than 400 million people worldwide. The global distribution of this disorder is remarkably similar to that of malaria, lending support to the so-called malaria protection hypothesis. G6PD deficiency is an X-linked, hereditary genetic defect due to mutations in the G6PD gene, which cause functional variants with many biochemical and clinical phenotypes. About 140 mutations have been described: most are single base changes, leading to aminoacid substitutions. The most frequent clinical manifestations of G6PD deficiency are neonatal jaundice, and acute haemolytic anaemia, which is usually triggered by an exogenous agent. Some G6PD variants cause chronic haemolysis, leading to congenital non-spherocytic haemolytic anaemia. The most effective management of G6PD deficiency is to prevent haemolysis by avoiding oxidative stress. Screening programmes for the disorder are undertaken, depending on the prevalence of G6PD deficiency in a particular community.

Primary Immunodeficiencies

Primary immunodeficiencies (PIDs), once considered to be very rare, are now increasingly recognized because of growing knowledge in the immunological field and the availability of more sophisticated diagnostic techniques and therapeutic modalities [161]. However in a database of >120,000 inpatients of a general hospital for conditions suggestive of ID 59 patients were tested, and an undiagnosed PID was found in 17 (29%) of the subjects tested [107]. The publication of the first case of agammaglobulinemia by Bruton in 1952 [60] demonstrated that the PID diagnosis is first done in the laboratory. However, PIDs require specialized immunological centers for diagnosis and management [33]. A large body of epidemiological evidence supports the hypothesis of the existence of a close etiopathogenetic relation between PID and atopy [73]. In particular, an elevated frequency of asthma, food allergy (FA), atopic dermatitis and enteric pathologies can be found in various PIDs. In addition we will discuss another subject that is certainly of interest: the pseudo-immunodepressed child with recurrent respiratory infections (RRIs), an event that often requires medical intervention and that very often leads to the suspicion that it involves antibody deficiencies [149].

Prospects for the treatment of drug-resistant malaria parasites

Widespread parasitic resistance has led to an urgent need for the development and implementation of new drugs for the treatment of Plasmodium falciparum malaria. Artemisinin and its derivatives are becoming increasingly important, used preferably in combination with a second antimalarial agent to increase the efficacy and slow the development of resistance. However, cost, production and pharmacological issues associated with artemisinin derivatives and potential partner drugs are hindering the implementation of combination therapies. This article reviews the molecular basis of the action of, and resistance to, different antimalarials and examines the prospects for the next generation of drugs to combat this potentially lethal human pathogen.

Improved quantitative method for G6PD deficiency detection

Glucose-6-phosphate dehydrogenase (G6PD) deficiency is a common hereditary enzyme defect that affects over 400 million people worldwide. Deficiency in G6PD can cause hemolytic anemia, which can be fatal if it is not treated properly. Mass qualitative G6PD-deficiency screening methods have been available for some time; however, in this study we developed the first high-throughput quantitative method for measuring G6PD activity. A patient's blood can be analyzed directly from the original collection tubes on a Hitachi P modular serum work area (SWA), which dramatically reduces the analysis time and the cost of the assay. The results presented here may enable the development of other improved, automated assays of whole-blood samples.

Further investigations of glucose-6-phosphate dehydrogenase variants in Flores Island, eastern Indonesia

We conducted field surveys for malaria and glucose-6-phosphate dehydrogenase (G6PD) deficiency in the eastern part of Flores Island, East Nusa Tenggara Province, Indonesia. A total of 1,108 volunteers (642 males and 466 females) belonging to three ethnic groups (Sikka, Ende and Bajo) were examined, and 55 G6PD-deficient individuals (38 males and 17 females) were detected. Among them, 50 samples were analyzed molecularly, in addition to three deficient cases in a Bajo family. In the Sikka population, G6PD Kaiping (1388G>A), one of the two common variants in the Chinese population, was unexpectedly found as the most dominant variant (11/22, 50.0%), followed by G6PD Chatham (1003G>A, 36.4%), G6PD Coimbra (592C>T, 9.1%) and G6PD Vanua Lava (383T>C, 4.5%). Frequency of G6PD Kaiping in the Sikka might be the highest among non-Chinese populations reported so far. In the Ende population, G6PD Vanua Lava (9/14, 64.3%) was the highest, followed by G6PD Kaiping (14.3%), G6PD Chinese-5 (1024C>T, 14.3%) and G6PD Chatham (7.1%). In the Bajo population, a total of 18 deficient cases were analyzed, and a novel mutation (844G>T) in exon 8 with a predicted amino acid change of 282 Asp>Tyr was found in a 7-year-old boy at a Bajo village near Maumere. This new Class II (mild type) variant was also confirmed in his mother and sister, and designated as G6PD Bajo Maumere. The missense mutation at the same nucleotide 844 has been known as G6PD Seattle/Lodi/Modena/Ferrara II, but this mutation is caused by a G>C substitution (282 Asp>His). In the Bajo population, G6PD Viangchan (871G>A, IVS 11 nt93 T>C, 1311C>T), the most common variant in continental Southeast Asian populations, was found to be the dominant (11/18, 61.1%), followed by G6PD Vanua Lava and the new variant (each 16.7%), and G6PD Coimbra (5.6%). These results strongly suggest that the Bajo peoples may have different ancestors from those for Sikka and Ende, and may be much closer to continental Southeast Asian populations. It is interesting that G6PD Canton (1376G>T), another common variant in Chinese, was not seen in the Flores population.

[Is Plasmodium vivax still a paradigm for uncomplicated malaria?]

P. vivax is supposed to be involved in benign tertian fever, responsible for a non-complicated disease that could be easily treated by standard antimalarial drug regimen. This could be considered as a long-standing paradigm of a non-virulent malaria parasite. When a patient exhibits severe malaria with the vivax parasite, the issue is often to find falciparum. However, with the implementation of molecular diagnosis, it has becoming more evident that vivax parasites could be involved in severe disease with probably a different pathogenesis. Mixed infections are frequent in various parts of Southeast Asian endemic areas and it was speculated that drugs used to treat falciparum could be involved in the development of vivax drug resistance. How should primaquine be used today for the treatment and prophylaxis of vivax malaria? Considering the re-emergence of vivax malaria in several areas, improving the treatment for this disease is certainly an important issue to avoid late episodes and transmission potential.

Process map proposal for the validation of genomic biomarkers

How can we encourage the application of novel genomic biomarkers in drug development? A major step in this direction would be a consensus on how to interpret results from measurements of these biomarkers in regulatory submissions. A transparent process for genomic biomarker validation would be of value both for the pharmaceutical industry as well as for regulatory agencies associated with it. A discussion on process map proposals for genomic biomarker validation can help with drafting of guidance documents for this process.

Rapid screening for glucose-6-phosphate dehydrogenase deficiency and haemoglobin polymorphisms in Africa by a simple high-throughput SSOP-ELISA method

BACKGROUND

Mutations in the haemoglobin beta-globin (HbB) and glucose-6-phosphate dehydrogenase (G6PD) genes cause widespread human genetic disorders such as sickle cell diseases and G6PD deficiency. In sub-Saharan Africa, a few predominant polymorphic variants of each gene account for a majority of these deficiencies. Examining at a larger scale the clinical importance of these independent genetic disorders, their possible association with malaria pathogenesis and innate resistance, and their relevance for antimalarial drug treatment, would be easier if an accurate screening method with limited costs was available.

METHODS

A simple and rapid technique was developed to detect the most prominent single nucleotide polymorphisms (SNPs) in the HbB and G6PD genes. The method is able to detect the different haemoglobin polymorphisms A, S, C and E, as well as G6PD polymorphisms B, A and A- based on PCR-amplification followed by a hybridization step using sequence-specific oligonucleotide probes (SSOPs) specific for the SNP variants and quantified by ELISA.

RESULTS

The SSOP-ELISA method was found to be specific, and compared well to the commonly used PCR-RFLP technique. Identical results were obtained in 98% (haemoglobin) and 95% (G6PD) of the tested 90 field samples from a high-transmission area in Tanzania, which were used to validate the new technique.

CONCLUSION

The simplicity and accuracy of the new methodology makes it suitable for application in settings where resources are limited. It would serve as a valuable tool for research purposes by monitoring genotype frequencies in relation to disease epidemiology.

Glucose-6-phosphate dehydrogenase (G6PD) mutations in Cambodia: G6PD Viangchan (871G>A) is the most common variant in the Cambodian population

We conducted a survey of malaria diagnoses and glucose-6-phosphate dehydrogenase (G6PD) testing in remote areas of Cambodia. Blood specimens from 670 people were collected by the finger-prick method. Of these people, 24.9% were found to have malaria, and 7.0% of people were G6PD deficient. In the Khmer, the largest ethnical population in Cambodia, the G6PD deficiency rate of males was 12.6% (25/199) whereas the rates in the minorities of the Tum Pun and the Cha Ray were 1.1% (1/93) and 3.2% (2/63), respectively. Of the G6PD-deficient subjects, 97.9% (46/47) were G6PD Viangchan (871G>A), and only one case (2.1%) was G6PD Union (1360C>T). Since G6PD Mahidol (487G>A) is common in Myanmar according to our previous study, the current finding suggests that the Cambodian population is derived from homogeneous ancestries and is different from the Myanmar population. All G6PD Viangchan cases were linked to two other mutations of 1311C>T and IVS-11 nt93T>C in the G6PD gene.

Glucose-6-phosphate dehydrogenase (G6PD) mutations in Myanmar: G6PD Mahidol (487G>A) is the most common variant in the Myanmar population

We conducted a survey of malaria diagnoses and treatments in remote areas of Myanmar. Blood specimens from more than 1,000 people were collected by the finger-prick method, and 121 (11%) of these people were found to be glucose-6-phosphate dehydrogenase (G6PD) deficient. Of these 121, 50 consented to analysis of the G6PD genome. We read the G6PD sequences of these subjects and found 45 cases of G6PD Mahidol (487G>A), two of G6PD Coimbra (592C>T), two of G6PD Union (1360C>T), and one of G6PD Canton (1376G>T). Taken together with data from our previous report, 91.3% (73/80) of G6PD variants were G6PD Mahidol. This finding suggests that the Myanmar population is derived from homogeneous ancestries and are different from Thai, Malaysian, and Indonesian populations.