Chairat Turbpaiboon

A variant in the CD209 promoter is associated with severity of dengue disease

Dengue fever and dengue hemorrhagic fever are mosquito-borne viral diseases. Dendritic cell–specific ICAM-3 grabbing nonintegrin (DC-SIGN1, encoded by CD209), an attachment receptor of dengue virus, is essential for productive infection of dendritic cells. Here, we report strong association between a promoter variant of CD209, DCSIGN1-336, and risk of dengue fever compared with dengue hemorrhagic fever or population controls. The G allele of the variant DCSIGN1-336 was associated with strong protection against dengue fever in three independent cohorts from Thailand, with a carrier frequency of 4.7% in individuals with dengue fever compared with 22.4% in individuals with dengue hemorrhagic fever (odds ratio for risk of dengue hemorrhagic fever versus dengue fever: 5.84, P = 1.4 × 10−7) and 19.5% in controls (odds ratio for protection: 4.90, P = 2 × 10−6). This variant affects an Sp1-like binding site and transcriptional activity in vitro. These results indicate that CD209 has a crucial role in dengue pathogenesis, which discriminates between severe dengue fever and dengue hemorrhagic fever. This may have consequences for therapeutic and preventive strategies.

Genetic determination and linkage mapping of Plasmodium falciparum malaria related traits in Senegal.

Plasmodium falciparum malaria episodes may vary considerably in their severity and clinical manifestations. There is good evidence that host genetic factors contribute to this variability. To date, most genetic studies aiming at the identification of these genes have used a case/control study design for severe malaria, exploring specific candidate genes. Here, we performed a family-based genetic study of falciparum malaria related phenotypes in two independent longitudinal survey cohorts, as a first step towards the identification of genes and mechanisms involved in the outcome of infection. We studied two Senegalese villages, Dielmo and Ndiop that differ in ethnicity, malaria transmission and endemicity. We performed genome-scan linkage analysis of several malaria-related phenotypes both during clinical attacks and asymptomatic infection. We show evidence for a strong genetic contribution to both the number of clinical falciparum malaria attacks and the asymptomatic parasite density. The asymptomatic parasite density showed linkage to chromosome 5q31 (LOD = 2.26, empirical p = 0.0014, Dielmo), confirming previous findings in other studies. Suggestive linkage values were also obtained at three additional chromosome regions: the number of clinical malaria attacks on chromosome 5p15 (LOD = 2.57, empirical p = 0.001, Dielmo) and 13q13 (LOD = 2.37, empirical p = 0.0014 Dielmo), and the maximum parasite density during asymptomatic infection on chromosome 12q21 (LOD = 3.1, empirical p<10−4, Ndiop). While regions of linkage show little overlap with genes known to be involved in severe malaria, the four regions appear to overlap with regions linked to asthma or atopy related traits, suggesting that common immune related pathways may be involved.

Impaired interaction of α-haemoglobin-stabilising protein with α-globin termination mutant in a yeast two-hybrid system

α‐Thalassaemia caused by α‐globin gene termination codon mutations (αT‐globin) has been explained by their inherent mRNA instability and by oxidative damage arising from the presence of membrane‐bound αT‐globin chains. To better understand the latter phenomenon, a yeast two‐hybrid system was used to assay the interaction between αT‐globin and its molecular chaperone, α‐haemoglobin‐stabilising protein (AHSP) and impaired binding of αT‐globin with AHSP compared with αwild‐type‐globin was observed.

Heritability of P. falciparum and P. vivax malaria in a Karen population in Thailand.

The majority of studies concerning malaria host genetics have focused on individual genes that confer protection against rather than susceptibility to malaria. Establishing the relative impact of genetic versus non-genetic factors on malaria infection and disease is essential to focus effort on key determinant factors. This relative contribution has rarely been evaluated for Plasmodium falciparum and almost never for Plasmodium vivax. We conducted a longitudinal cohort study in a Karen population of 3,484 individuals in a region of mesoendemic malaria, Thailand from 1998 to 2005. The number of P. falciparum and P. vivax clinical cases and the parasite density per person were determined. Statistical analyses were performed to account for the influence of environmental factors and the genetic heritability of the phenotypes was calculated using the pedigree-based variance components model. The genetic contribution to the number of clinical episodes resulting from P. falciparum and P. vivax were 10% and 19% respectively. There was also moderate genetic contribution to the maximum and overall parasite trophozoite density phenotypes for both P. falciparum (16%&16%) and P. vivax (15%&13%). These values, for P. falciparum, were similar to those previously observed in a region of much higher transmission intensity in Senegal, West Africa. Although environmental factors play an important role in acquiring an infection, genetics plays a determinant role in the outcome of an infection with either malaria parasite species prior to the development of immunity.

Alpha-hemoglobin stabilizing protein: molecular function and clinical correlation.

The discovery of alpha-hemoglobin stabilizing protein (AHSP), a chaperone for free alpha-hemoglobin (alpha-Hb), has provided a satisfactory solution to the perplexing problem of balanced globin levels for Hb production in erythroid cells in the face of a two-fold excess of alpha-globin to beta-globin gene dosage. Unmatched alpha-Hb is unstable and precipitates onto membranes, where the released heme exerts oxidative damages resulting in ineffective erythropoiesis and hemolytic anemia, the underlying causes of pathology in the hereditary anemia of beta-thalassemia. The interaction of alpha-Hb with AHSP involves surfaces normally employed in binding to beta-Hb. However, a conformational change to the AHSP-bound alpha-Hb results in an oxidized heme, but in a pocket that is now less exposed to the outside environment, thereby protecting against both peroxide-induced heme loss and iron-induced redox reaction. Studies in both mice and humans indicate that reduction in AHSP can result in hematological pathology. Conversely, alpha-Hb variants that are compromised in their ability to bind with AHSP produce beta-thalassemia-like symptoms. Disease conditions like some forms of thalassemia that are directly associated with AHSP structural and/or functional defects can now be included within the category of chaperonopathies.

Hemoglobin Pakse: Presence on Red Blood Cell Membrane and Detection by Polymerase Chain Reaction-Single-Strand Conformational Polymorphism

Nondeletional gene mutations giving rise to α-thalassemia can be found at polymorphic frequency in Southeast Asia. Although the most common is hemoglobin Constant Spring (Hb CS), caused by a termination codon mutation (UAA →CAA, Gln) in the α2-globin gene and resulting in reduced synthesis of the elongated α-globin variant, Hb Pakse (UAA→UAU,Tyr) also has been observed at a significant prevalence.Western blot analysis of ghost membrane proteins separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis from an individual with α-thal 1/Hb Pakse revealed the existence of a higher molecular weight globin of 18 kd consistent with an αPakse-globin chain.The presence of αPakse-globin on membranes of Hb Pakse-containing red blood cells affords an explanation for the severity of anemia observed in such patients. However, because the 2 Hb variants cannot be distinguished by current biochemical techniques, we developed a convenient single-tube polymerase chain reaction-single-strand conformational polymorphism (PCR-SSCP) protocol for the simultaneous diagnosis of Hb CS and Hb Pakse by amplifying a short fragment covering the termination codon of the α2-globin gene.This PCR-SSCP method required no internal control coamplification or use of restriction enzymes and has the potential of identifying all the other possible termination codon mutations in a single reaction with only 1 pair of primers.

Vascular Nature and Existence of Anastomoses of Extrinsic Postauricular Fascia: Application for Staged Auricular Reconstruction

Abstract A staged auricular reconstruction in microtia patients was developed by using superficial mastoid fascia (as part of extrinsic postauricular fascia) to cover the cartilagenous framework due to its highly vascularized nature. Three branches of external carotid artery (superficial temporal artery, posterior auricular artery and occipital artery) were found to supply this fascia, this study was therefore aimed to investigate the dimension of blood supply from each vessel and also to demonstrate the existence of anastomoses among these arteries. Thirty-eight pinnas and postauricular fascias from Thai fresh adult cadavers were included to document the anastomoses by showing both perfused dye connection (10 dissections) and visible anastomotic branches (8 dissections) among them. Distribution of each vessel trunk and its branches were demonstrated using superimposed illustration in the other 20 dissections with dye injection into each artery to designate 3 zones of anastomotic area between each arterial pair. Maximal size of viable postauricular fascial flap for staged reconstruction according to this vascular study was thus estimated to be at least 5 cm above and 3 cm below the Frankfurt horizontal plane and about 6 cm posterior to external acoustic meatus owing to the course of posterior auricular artery and its anastomoses. In addition, greater size of flap with dual blood supply from both superficial temporal and posterior auricular arteries can be raised by harvesting beyond 5 cm above external acoustic meatus.

Anatomy of medial plantar superficial branch artery perforators: Facilitation of medial plantar superficial branch artery perforator (MPAP) flap harvesting and design for finger pulp reconstruction

Medial plantar artery perforator (MPAP) flap was proposed as proper option for finger pulp reconstruction. To provide the previously unavailable vessel information required for this small flap design, this study aimed to gather all necessary anatomy of MPA, MPAP, and their territories of blood supply to apply in clinical MPAP flap reconstruction minimizing perforator injury.