Inhibitory effect of beta zero-thalassaemia/haemoglobin E erythrocytes on Plasmodium falciparum growth in vitro

The growth of Plasmodium falciparum in erythrocytes from individuals with beta zero-thalassaemia or haemoglobin (Hb) E, or both, was assessed in vitro. A significant inhibitory effect on the growth of the parasite was found only with erythrocytes from individuals doubly heterozygous for beta zeros-thalassaemia and HbE. The inhibitory effect was particularly marked with erythrocytes from splenectomized beta zeros-thalassaemia/HbE patients. The protective effect was related to HbF, Hb levels and shape abnormalities of the variant erythrocytes.     

Association of Hb Q-Thailand with homozygous Hb E and heterozygous Hb Constant Spring in pregnancy

Hemoglobin (Hb) Q-Thailand [alpha74(EF3): Asp-->His] is an abnormal Hb found mainly in China and South-east Asian countries. Association of the alpha(Q-Thailand) allele with alpha-thalassemia has important implications in diagnosis. We report the hitherto undescribed conditions of this variant in two unrelated pregnant Thai women. Routine Hb analyses using high-performance liquid chromatography identified abnormal Hb migrating after Hb A(2) in addition to a homozygous Hb E in the proband 1 and to a heterozygous Hb Constant Spring (Hb CS) in the proband 2. Further alpha-globin gene analysis identified that the variant was caused by the GAC to CAC mutation at codon 74 of the alpha1-globin gene corresponding to the Hb Q-Thailand, detected in cis to the 4.2 kb deletional alpha-thalassemia 2 in both cases. Interaction of the alpha(Q-Thailand) with the beta(E) globin chains in the proband 1 leads to a Hb variant, namely the Hb QE. Family study of the proband 1 showed that her non-pregnant sister had the same genotype but her father was a double heterozygote for Hb E and Hb Q-Thailand in whom both Hb Q-Thailand and Hb QE were detected. Genotype-phenotype relationships observed in these families with complex hemoglobinopathies are presented and compared with those of simple homozygote for Hb E, heterozygote for Hb CS and heterozygote for Hb Q-Thailand found in other unrelated subjects. A simple DNA assay based on allele-specific polymerase chain reaction for simultaneous detection of the Hb Q-Thailand mutation and the 4.2 kb deletional alpha-thalassemia 2 determinant was developed and validated.     

Molecular characterization of thalassemia intermedia associated with HPFH-6/beta-thalassemia and HPFH-6/Hb E in Thai patients

We report the molecular and hematological characterizations of thalassemia caused by interactions of the hereditary persistence of fetal hemoglobin (HPFH)-6 with beta-thalassemia in 2 Thai patients and the HPFH-6 with Hb E in another Thai patient. Marked hypochromic microcytosis, characteristics of thalassemia intermedia, were obvious in the former 2 cases but the latter had much milder clinical phenotype with normal Hb and a slightly reduced mean corpuscular volume (MCV) value. Hb analysis revealed no Hb A but Hb A(2)F patterns in the compound HPFH-6/beta-thalassemia patients and the EF pattern in the HPFH-6/Hb E patient. The (G)gamma-globin chain predominated in all cases. Globin gene analyses demonstrated that all patients carried the 101-kb HPFH-6 deletion in trans to the beta-thalassemia genes with the IVS1#5 G-C mutation and the G insertion between codons 8/9 and the beta(E)-gene, respectively. Hematologic data of the patients were compared to those of the HPFH-6 heterozygotes found in their family members and different genotype-phenotype interactions of this HPFH determinant in these Thai patients are illustrated.     

Ultrastructure and cell cycle distribution of erythropoietic cells in heterozygotes and homozygotes for haemoglobin E

S ummary. Marrow aspirates from heterozygotes and homozygotes for haemoglobin E (HbE) have been studied by electron microscopy and by the technique of combined Feulgen microspectrophotometry and ³H-thymidine autoradiography. The erythropoietic cells of heterozygotes did not contain any precipitated globin chains and the proliferating erythroblasts of such individuals showed no abnormality in their distribution in the different stages of interphase. By contrast, 0–1.5% of late erythroblast profiles and 3.1–12.8% of marrow reticulocyte profiles of homozygotes contained intracellular inclusions resembling precipitated α-chains. Although precipitated globin chains were not seen in the early polychromatic erythroblasts of homozygotes, the number of these cells in the G2 phase relative to that in the S phase was increased. These data indicate that there is (1) probably little or no imbalance of globin chain synthesis in heterozygotes, (2) a substantial degree of imbalance in homozygotes, and (3) a disturbance of erythroblast proliferation in homozygotes which cannot be attributed to the deleterious effects of detectable intracellular α-chain precipitates. The electron microscope and cell cycle distribution data in the homozygotes for HbE were similar to those in two heterozygotes for β thalassaemia.     

Red cell and plasma calcium, copper and zinc in beta-thalassemia/hemoglobin E

Beta-thalassemia/Hb E is a genetic disease prevalent in Thailand. This study has used atomic absorption spectroscopy to evaluate red cell and plasma calcium, copper and zinc in patients with beta-thalassemia/Hb E, both splenectomized and non-splenectomized. The levels of these trace elements in both red cells and plasma were different between the non-thalassemic controls and the disease patients. The most prominent result was that calcium concentration in red cells increased significantly in thalassemia subjects, particularly in splenectomized cases. These results might reflect the abnormal trace element metabolism and defects in the calcium transport system of the red cell membrane in thalassemia.     

Hb Paksé [(alpha2) codon 142 (TAA-->TAT or Term-->Tyr)J in Thai patients with EAbart's disease and Hb H Disease

Hb Paksé is caused by an alpha2-globin gene termination codon mutation, TAA-->TAT or Term-->Tyr, initially described in a Laotian family. We now report for the first time that the same mutation has been found in 14 Thai patients, seven with EABart's disease, four with Hb H disease, and three with alpha-thalassemia trait who were initially diagnosed as having Hb Constant Spring (Hb CS; alpha2-globin gene termination codon mutation TAA-->CAA or Term-->Gln). Co-inheritance of this mutation with alpha-thalassemia-1 (SEA type) leads to Hb H disease (hereafter designated as Hb H-Paksé disease) and to a complex thalassemia syndrome, namely EABart's-Paksé disease. Hematological data of these patients were compared with those of classical Hb H-CS and the EABart's patients. To facilitate epidemiological and diagnostic screening of Hb Paksé, a simple assay procedure based on allele specific polymerase chain reaction (PCR) amplifications was developed and validated. Using this allele specific PCR as a screening method, five additional individuals with Hb Paksé were found among 71 Thai subjects previously thought to have Hb CS.