Biomedical subjects

Ulrich Bienzle

Publications and source records attributed to Ulrich Bienzle.

At least 19 recordsLinked to original sources

PubMed2006

Detection and clinical manifestation of placental malaria in southern Ghana.

BACKGROUND: Plasmodium falciparum can be detected by microscopy, histidine-rich-protein-2 (HRP2) capture test or PCR but the respective clinical relevance of the thereby diagnosed infections in pregnant women is not well established. METHODS: In a cross-sectional, year-round study among 839 delivering women in Agogo, Ghana, P. falciparum was screened for in both, peripheral and placental blood samples, and associations with maternal anaemia, low birth weight (LBW) and preterm delivery (PD) were analysed. RESULTS: In peripheral blood, P. falciparum was observed in 19%, 34%, and 53% by microscopy, HRP2 test, and PCR, respectively. For placental samples, these figures were 35%, 41%, and 59%. Irrespective of diagnostic tool, P. falciparum infection increased the risk of anaemia. Positive peripheral blood results of microscopy and PCR were not associated with LBW or PD. In contrast, the HRP2 test performed well in identifying women at increased risk of poor pregnancy outcome, particularly in case of a negative peripheral blood film. Adjusting for age, parity, and antenatal visits, placental HRP2 was the only marker of infection associated with LBW (adjusted odds ratio (aOR), 1.5 (95%CI, 1.0-2.2)) and, at borderline statistical significance, PD (aOR, 1.4 (1.0-2.1)) in addition to anaemia (aOR, 2.3 (1.7-3.2)). Likewise, HRP2 in peripheral blood of seemingly aparasitaemic women was associated with PD (aOR, 1.7 (1.0-2.7)) and anaemia (aOR, 2.1 (1.4-3.2)). CONCLUSION: Peripheral blood film microscopy not only underestimates placental malaria. In this highly endemic setting, it also fails to identify malaria as a cause of foetal impairment. Sub-microscopic infections detected by a HRP2 test in seemingly aparasitaemic women increase the risks of anaemia and PD. These findings indicate that the burden of malaria in pregnancy may be even larger than thought and accentuate the need for effective anti-malarial interventions in pregnancy.

Animals↗

PubMed2006

Markers of sulfadoxine-pyrimethamine-resistant Plasmodium falciparum in placenta and circulation of pregnant women.

Placental sequestration of Plasmodium falciparum in pregnancy may impair the usefulness of molecular markers of sulfadoxine-pyrimethamine resistance. In 300 infected, delivering women, the concordance of PCR-restriction fragment length polymorphism-derived parasite resistance alleles in matched samples from placenta and circulation was 83 to 98%. Sulfadoxine-pyrimethamine resistance typing in peripheral blood is reasonably representative of P. falciparum infecting pregnant women.

Adolescent↗

PubMed2006

High prevalence of drug-resistance mutations in Plasmodium falciparum and Plasmodium vivax in southern Ethiopia.

BACKGROUND: In Ethiopia, malaria is caused by both Plasmodium falciparum and Plasmodium vivax. Drug resistance of P. falciparum to sulfadoxine-pyrimethamine (SP) and chloroquine (CQ) is frequent and intense in some areas. METHODS: In 100 patients with uncomplicated malaria from Dilla, southern Ethiopia, P. falciparum dhfr and dhps mutations as well as P. vivax dhfr polymorphisms associated with resistance to SP and P. falciparum pfcrt and pfmdr1 mutations conferring CQ resistance were assessed. RESULTS: P. falciparum and P. vivax were observed in 69% and 31% of the patients, respectively. Pfdhfr triple mutations and pfdhfr/pfdhps quintuple mutations occurred in 87% and 86% of P. falciparum isolates, respectively. Pfcrt T76 was seen in all and pfmdr1 Y86 in 81% of P. falciparum. The P. vivax dhfr core mutations N117 and R58 were present in 94% and 74%, respectively. CONCLUSION: These data point to an extraordinarily high frequency of drug-resistance mutations in both P. falciparum and P. vivax in southern Ethiopia, and strongly support that both SP and CQ are inadequate drugs for this region.

Adolescent↗

PubMed2006

Common polymorphisms of toll-like receptors 4 and 9 are associated with the clinical manifestation of malaria during pregnancy.

Toll-like receptors (TLRs) are involved in recognition of and response to Plasmodium falciparum. In 304 primiparous Ghanaian women, we examined whether common TLR4 and TLR9 polymorphisms influence susceptibility to and manifestation of malaria during pregnancy. The TLR variants did not affect P. falciparum prevalence or parasite density. However, in P. falciparum-infected women, both the TLR4 Asp299Gly and the TLR9 T-1486C polymorphisms increased the risk of low birth weight in term infants 6-fold, and, additionally, TLR4 Asp299Gly increased the risk of maternal anemia 5-fold; preterm delivery was not associated with these TLR variants. These findings suggest that TLR4 and TLR9 play a role in the manifestation of malaria during pregnancy.

Adolescent↗

PubMed2006

Malaria, anemia, and malnutrition in african children--defining intervention priorities.

BACKGROUND: Malaria, anemia, and malnutrition contribute substantially to childhood morbidity in sub-Saharan Africa, but their respective roles and interactions in conferring disease are complex. We aimed to investigate these interactions. METHODS: In 2002, we assessed plasmodial infection, anemia, and nutritional indices in 2 representative surveys comprising >4000 children in northern Ghana. RESULTS: Infection with Plasmodium species was observed in 82% and 75% of children in the rainy and dry season, respectively. The fraction of fever attributable to malaria was 77% in the rainy season and 48% in the dry season and peaked in children of rural residence. Anemia (hemoglobin level, <11 g/dL) was seen in 64% of children and was, in multivariate analysis, associated with young age, season, residence, parasitemia, P. malariae coinfection, and malnutrition (odds ratio [OR], 1.68 [95% confidence interval [CI], 1.38-2.04]). In addition, malnutrition was independently associated with fever (axillary temperature, > or = 37.5 degrees C; OR, 1.59 [95% CI, 1.13-2.23]) and clinical malaria (OR, 1.67 [95% CI, 1.10-2.50]). CONCLUSIONS: Malnutrition is a fundamental factor contributing to malaria-associated morbidity and anemia, even if the latter exhibits multifactorial patterns. Our data demonstrate that malaria-control programs alone may not have the desired impact on childhood morbidity on a large scale without concomitant nutrition programs.

Age Factors↗

PubMed2006

Field-based evidence for linkage of mutations associated with chloroquine (pfcrt/pfmdr1) and sulfadoxine-pyrimethamine (pfdhfr/pfdhps) resistance and for the fitness cost of multiple mutations in P. falciparum.

Mutations in the Plasmodium falciparum pfcrt gene on chromosome 7 and possibly mutations in pfmdr1 on chromosome 5 have a role in conferring resistance against chloroquine (CQ), as do mutations of pfdhfr on chromosome 4 and pfdhps on chromosome 8 in terms of resistance against sulfadoxine/pyrimethamine (SP). The additive role of multiple mutations in the development of resistance to each drug suggests a non-random occurrence. In this study, parasite isolates were obtained from 50 patients with uncomplicated P. falciparum malaria from rural Eastern Sudan, an endemic setting with minimal overlap of infection. The parasite isolates were genotyped for detection of 12 alleles in CQ and SP resistance genes. Our main findings were: (1) the frequency of mutant alleles, pfcrt K76T, pfmdr1 N86Y, pfdhfr N51I, pfdhfr S108N, pfdhps K540E and pfdhps A581G were; 0.90, 0.86, 0.84, 0.84, 0.80 and 0.20, respectively. (2) No mutations were detected for the pfdhfr loci A16V, C59R and I164L, and for pfdhps loci S436A, A437G and A613S. (3) There was a statistically significant association between the mutations in: (i) the CQ resistance (CQR) genes, pfcrt T76 and pfmdr1 Y86 (P< or =0.001), (ii) the SP resistance (SPR) genes, pfdhfr I51, pfdhfr N108 and pfdhps E540 (P< or =0.001-0.04) and (iii) the CQ "i" and SP "ii" resistance genes (P=0.001) 4. The fitness cost of multiple mutations was revealed by a significantly reduced parasite density of isolates bearing the mutant alleles (P=0.048). However, the significantly higher gametocyte carriage rate among isolates with resistance mutations (P=0.001) is possibly an evolutionary mechanism for survival of mutant parasites.

Animals↗

PubMed2006

Immunization with an adjuvant hepatitis B vaccine in liver transplant recipients: antibody decline and booster vaccination with conventional vaccine.

Patients after orthotopic liver transplantation (OLT) due to hepatitis B virus (HBV)-related disease are at risk of endogenous hepatitis B reinfection and may receive life long prophylaxis with hepatitis B hyperimmunoglobulin (HBIG). In a previous study 16 of 20 OLT patients were immunized successfully with an adjuvant hepatitis B vaccine. To maintain protective antibody levels under immunosuppressive therapy, 11 of these patients were revaccinated with a double dosed conventional hepatitis B vaccine. Median interval between last vaccination and booster was 24 months (range 22-31 months). Antibody titres against hepatitis B surface antigen (anti-HBs) were monitored at the day of booster vaccination (day 0), at day 7 and day 28. At day 0, all vaccinees but one had anti-HBs titres greater than 500 IU/L (median 1,925 IU/L, range 196-7,612 IU/L). Maximum antibody titres after previous vaccination declined by a median of 82% (range 47-96%). After booster vaccination the anti-HBs titre increased significantly by a median factor of 2.42 (P<0.05). In conclusion, the majority of liver transplant recipients who previously had responded to adjuvant hepatitis B vaccine exhibited sufficient immunocompetence to produce a substantial antibody response after booster immunization with a conventional vaccine.

Adjuvants, Immunologic↗

PubMed2005

Toll-like receptor (TLR) polymorphisms in African children: Common TLR-4 variants predispose to severe malaria.

Genetic host factors play a substantial role in susceptibility to and severity of malaria, which continues to cause at least one million deaths per year. Recently, members of the toll-like receptor (TLR) family have been shown to be involved in recognition of the etiologic organism Plasmodium falciparum: The glycosylphosphatidylinositol anchor induces signaling in host cells via TLR-2 and -4, whereas hemozoin-induced immune activation involves TLR-9. Binding of microbial ligands to the respective TLRs triggers the release of proinflammatory cytokines via the TLR/IL-1 receptor (TIR) domain and may contribute to the host response in malaria, including cytokine induction and fever. In a case-control study among 870 Ghanaian children, we examined the influence of TLR-2, -4, and -9 polymorphisms in susceptibility to severe malaria. TLR-2 variants common in Caucasians and Asians were completely absent. However, we found a rare previously undescribed mutation (Leu658Pro), which impairs signaling via TLR-2. We failed to detect any polymorphisms within the TLR-9 Toll/IL-1 receptor domain. Two frequent TLR-9 promoter polymorphisms did not show a clear association with malaria severity. In contrast, the TLR-4-Asp299Gly variant occurred at a high rate of 17.6% in healthy controls and was even more frequent in severe malaria patients (24.1%, P < 0.05). Likewise, TLR-4-Thr399Ile was seen in 2.4% of healthy children and in 6.2% of patients (P = 0.02). TLR-4-Asp299Gly and TLR-4-Thr399Ile conferred 1.5- and 2.6-fold increased risks of severe malaria, respectively. These findings suggest TLR4-mediated responses to malaria in vivo and TLR-4 polymorphisms to be associated with disease manifestation.

Base Sequence↗

PubMed2005

Concurrence of Plasmodium falciparum dhfr and crt mutations in northern Ghana.

BACKGROUND: Both chloroquine (CQ) and sulfadoxine-pyrimethamine (SP) are failing drugs in much of sub-Saharan Africa. Previous findings suggest an association between resistance to CQ and to SP in vivo, in vitro, and on the molecular level. METHODS: In 126 Ghanaian children with uncomplicated malaria, associations between mutations conferring resistance in the Plasmodium falciparum dihydrofolate reductase (dhfr; SP) and chloroquine resistance transporter (crt; CQ) genes, concentrations of residual antimalarial drugs, and gametocyte carriage were examined. RESULTS: Mutant dhfr alleles and the CQ-resistance allele crt T76 were strongly associated with each other. Isolates exhibiting the dhfr triple mutation seven times more likely also contained crt T76 parasites as compared to isolates without the dhfr triple variant (P = 0.0001). Moreover, both, isolates with the dhfr triple mutation (adjusted OR, 3.2 (95%CI, 1.0-10.4)) and with crt T76 (adjusted OR, 14.5 (1.4-150.8)) were associated with an increased likelihood of pre-treatment gametocytaemia. However, crt T76 did not correlate with gametocytaemia following SP treatment and no selection of crt T76 in SP treatment failure isolates was observed. CONCLUSION: These results confirm an association between CQ and SP resistance markers in isolates from northern Ghana. This could indicate accelerated development of resistance to SP if CQ resistance is already present, or vice versa. Considering the enhanced transmission potential as reflected by the increased proportion of isolates containing gametocytes when resistant parasites are present, co-resistance can be expected to spread in this area. However, the underlying mechanism leading to this constellation remains obscure.

Animals↗

PubMed2005

In vitro antiplasmodial activity of prenylated chalcone derivatives of hops (Humulus lupulus) and their interaction with haemin.

OBJECTIVES: There is an urgent need to discover new antimalarials, due to the spread of chloroquine resistance and the limited number of available drugs. Chalcones are one of the classes of natural products that are known to possess antiplasmodial properties. Therefore, the in vitro antiplasmodial activity of the main hop chalcone xanthohumol and seven derivatives was evaluated. In addition, the influence of the compounds on glutathione (GSH)-dependent haemin degradation was analysed to determine its contribution to the antimalarial effect of chalcones. METHODS: In vitro antiplasmodial activity was evaluated against the chloroquine-sensitive strain poW and the multiresistant clone Dd2 using a [(3)H]hypoxanthine-incorporation assay. Inhibition of GSH-dependent haemin degradation was analysed by a multiwell plate assay at 11 microM. RESULTS: Of the eight compounds tested, four possessed activity with IC(50) values<25 microM against at least one of the two strains of Plasmodium falciparum. The main hop chalcone, xanthohumol, was most active with IC(50) values of 8.2+/-0.3 (poW) and 24.0 +/- 0.8 microM (Dd2). Three of these compounds were additionally active in the haemin-degradation assay. CONCLUSIONS: The results demonstrate for the first time the ability of chalcone derivatives to interfere with the haemin-degradation process of P. falciparum. This effect might contribute to their antiplasmodial activity. Nevertheless, as one compound showed inhibition of P. falciparum without being able to interact with GSH-dependent haemin degradation, other modes of action must add to the observed antiparasitic activity of hop chalcones.

Animals↗

PubMed2005

Diagnosis of red cell G6PD deficiency in rural Burkina Faso: comparison of a rapid fluorescent enzyme test on filter paper with polymerase chain reaction based genotyping.

Glucose-6-phosphate dehydrogenase (G6PD) deficient individuals are at increased risk of developing haemolysis following treatment with various antimalarial drugs. Reliable field tests for G6PD deficiency are thus needed in chemotherapy studies and their validity has to be assessed. In two phase II clinical trials on methylene blue (MB) antimalarial therapy in rural Burkina Faso, paediatric and adult participants were tested for G6PD deficiency. The results of a haemoglobin-adjusted nicotinamide adenine dinucleotide phosphate (NADPH) fluorescence test on paper (NFP test) were compared with polymerase chain reaction (PCR)-based G6PD genotyping also using blood samples on filter papers. This is the first study comparing sensitivity and specificity of the two methods. There was good agreement between the NFP test results and the PCR findings. The estimate of the sensitivity of the NFP test was 98.2% (95.8-99.6%) and the specificity was 97.1% (94.2-99.2%). In conclusion, the NFP assay is a reliable and inexpensive method for large-scale G6PD deficiency screening in rural West Africa.

Adolescent↗

PubMed2005

A randomized, placebo-controlled, double-blind trial on sulfadoxine-pyrimethamine alone or combined with artesunate or amodiaquine in uncomplicated malaria.

The therapeutic efficacy of sulfadoxine-pyrimethamine (SP) alone, SP plus amodiaquine (AQ), and SP plus artesunate (AS) was assessed in a randomized, placebo-controlled, and double-blind trial among 438 children with uncomplicated Plasmodium falciparum malaria in northern Ghana. Clinical and parasitological responses were monitored for 28 days following treatment; 86%, 98% and 97% of SP-, SP + AQ-, and SP + AS-treated patients achieved adequate clinical and parasitological response (ACPR) within 2 weeks, respectively. Parasite clearance was better with SP + AS than with SP or SP + AQ treatment but re-infections were more common. Polymerase chain reaction (PCR)-corrected rates of ACPR at day 28 were 72.2% for SP, 94.1% for SP + AQ (P < 0.0001), and 94.5% for SP + AS (P < 0.0001). Gametocyte prevalence and density 1 week after treatment were highest in children treated with SP, and lowest in patients receiving SP + AS. No severe adverse events attributable to study medication were observed. In northern Ghana, more than one of four children suffered SP treatment failure within 4 weeks. Both SP + AQ and SP + AS are efficacious alternative therapeutic options in this region. Although SP + AS and SP + AQ treatments have virtually identical cure rates, rapid parasite clearance and pronounced gametocidal effects are the advantages of the former, whereas cost and a lower rate of late re-infections are those of the latter.

Amodiaquine↗

PubMed2005

Age-dependent effect of plasma nitric oxide on parasite density in Ghanaian children with severe malaria.

Nitric oxide (NO) has toxic properties against Plasmodium falciparum. While high blood levels have been associated with protection against severe malarial disease, they may also contribute to the pathophysiology of cerebral malaria and severe anaemia. Promoter variants in the inducible nitric oxide synthase (iNOS) gene have been shown to influence NO concentrations and disease manifestation. However, findings are conflicting. We examined associations of plasma NO metabolites (NOx) with symptoms of severe malaria, particularly malarial anaemia and cerebral malaria, and with iNOS promoter variants. In 210 Ghanaian children with severe malaria, we measured plasma nitrite, nitrate, and S-nitrosothiol, and genotyped the iNOS promoter variants -954G-->C, -1173C-->T, and the -2.5 kb (CCTTT)(n) microsatellite. NOx levels decreased with age. In young children (<24 months), high NOx was associated with reduced parasite density. This was not seen in patients of 24-48 months of age and reversed in older children. Subgroup analysis revealed that in children with severe anaemia but without cerebral involvement (prostration, impaired consciousness, convulsions), high NOx levels correlated with low parasitaemia (P = 0.02). In these children, elevated NOx levels were also associated with the iNOS-954C-->T/(CCTTT)(8) haplotype (P = 0.03). No association between NOx or iNOS genotypes and cerebral malaria was observed. Our findings suggest that in young children with severe malaria NOx reduces parasitaemia. This effect wanes at higher ages and may reflect a predominance of unspecific immune responses to infection in early childhood. This finding may have importance for the understanding of associations between iNOS variants and severe malaria in regions of differing disease manifestation.

Age Factors↗

PubMed2005

Limited influence of haptoglobin genotypes on severe malaria in Ghanaian children.

Haptoglobin (Hp) polymorphisms in sub-Saharan Africa have been associated with an increased risk of severe malaria. However, available data are inconclusive. We examined the role of Hp polymorphisms in susceptibility to Plasmodium falciparum infection and to severe malaria in northern Ghana. Three groups each of 290 age and sex-matched children with severe malaria, children with asymptomatic P. falciparum infection and aparasitaemic healthy controls were studied. Hp typing was based on PCR. In all children, Hp1-1, Hp2-1, and Hp2-2 occurred in 32.4%, 54.1%, and 13.5%, respectively. The prevalence of the Hp genotypes did not differ significantly between groups. However, Hp2 alleles were least common in healthy children (0.379), more frequent in parasitaemic controls (0.402), and most common in severe malaria patients (0.434; = 3.7; P = 0.06). In matched pair analysis, no Hp genotype increased the risk of severe malaria. However, using Hp1-1 as a reference, children with Hp2-2 exhibited a slightly increased risk of severe malaria (odds ratio, 1.6; P = 0.04). These results indicate that Hp polymorhisms may have a rather limited influence on the development of severe malaria.

Child↗

PubMed2005

Plasmodium falciparum dhfr but not dhps mutations associated with sulphadoxine-pyrimethamine treatment failure and gametocyte carriage in northern Ghana.

Both use of sulphadoxine-pyrimethamine (SP) and SP-resistance of Plasmodium falciparum are increasing in sub-Saharan Africa. Mutations in the P. falciparum dihydrofolate reductase (dhfr) and dihydropteroate synthase (dhps) genes can predict treatment failure of SP, however, the degree of this relationship varies regionally. In northern Ghana, pre-treatment dhfr/dhps genotypes were examined in 126 children and associations with PCR-corrected SP treatment outcome and gametocyte carriage were analysed. SP treatment failure within 4 weeks of follow-up occurred in 28%. Among all pre-treatment isolates, the dhfr triple mutation (Ile-51 + Arg-59 + Asn-108) was detected in 47%. Compared with dhfr wildtype parasites, the presence of the dhfr triple mutation increased the risk of treatment failure tenfold. Likewise, parasite clearance was delayed in the presence of dhfr variants. Dhfr mutants and dhps Gly-437 were selected in treatment failure isolates. Gametocytaemia 1 week following treatment was strongly associated with dhfr mutations. Remarkably, this was also true for the prevalence of gametocytes at recruitment. Dhps alleles did neither influence treatment outcome nor gametocyte carriage. In northern Ghana, the prevalence of the dhfr triple mutation can be used as a tool to screen for and to monitor SP resistance. The lack of association between dhps alleles and SP treatment outcome suggests a minor role of these molecular markers in this region at present.

Animals↗

PubMed2005

Short communication: high prevalence of the cytochrome P450 2C8*2 mutation in Northern Ghana.

Recently, Ghana has changed the first-line treatment of uncomplicated malaria from chloroquine to amodiaquine (AQ) plus artesunate. AQ may cause adverse events such as agranulocytosis and hepatoxicity. The pro-drug AQ is transformed by cytochrome P450 CYP2C8 to the active metabolite N-desethylaminodiaquine. Several polymorphic variants of CYP2C8 are known, some with reduced activity. In 200 randomly selected children from Northern Ghana, we determined the allele frequencies of the CYP2C8 variants CYP2C8*1 (wild type), CYP2C8*2, CYP2C8*3, and CYP2C8*4. We did not detect CYP2C8*3 and CYP2C8*4, but CYP2C8*2 showed an allele frequency of 0.1675. AQ metabolism in patients with CYP2C8*2 may be impaired, and with an increase of AQ based treatment the risk of severe adverse events may mount.

Amodiaquine↗

PubMed2004

Hemoglobin C and resistance to severe malaria in Ghanaian children.

Hemoglobin (Hb) C has been reported to protect against severe malaria. It is unclear whether relative resistance affects infection, disease, or both. Its extent may vary between regions and with disease pattern. We conducted a case-control study of children with severe malaria, asymptomatic parasitemic children, and healthy children in Ghana. HbAC did not prevent infection but reduced the odds of developing severe malaria and severe anemia. Protection was stronger with HbAS. The frequencies of HbCC and HbSC decreased, from healthy children to asymptomatic parasitemic children to children with severe malaria. These data support the notion that natural selection of HbC occurs because of the relative resistance it confers against severe malaria but argue against the notion that HbC offers resistance to infection.

Animals↗

PubMed2004

Alpha(+)-thalassemia protects African children from severe malaria.

The high frequency of alpha(+)-thalassemia in malaria-endemic regions may reflect natural selection due to protection from potentially fatal severe malaria. In Africa, bearing 90% of global malaria morbidity and mortality, this has not yet been observed. We tested this hypothesis in an unmatched case-control study among 301 Ghanaian children with severe malaria and 2107 controls (62% parasitemic). In control children, alpha(+)-thalassemia affected neither prevalence nor density of Plasmodium falciparum. However, heterozygous alpha(+)-thalassemia was observed in 32.6% of controls but in only 26.2% of cases (odds ratio [OR], 0.74; 95% confidence interval [CI], 0.56-0.98). Protection against severe malaria was found to be pronounced comparing severe malaria patients with parasitemic controls (adjusted OR in children < 5 years of age, 0.52; 95% CI, 0.34-0.78) and to wane with age. No protective effect was discernible for homozygous children. Our findings provide evidence for natural selection of alpha(+)-thalassemia in Africa due to protection from severe malaria.

Case-Control Studies↗