Prevention of severe thalassemia in northeast Thailand: 16 years of experience at a single university center

OBJECTIVE

To demonstrate the performance of thalassemia prevention in northeast Thailand during 1993-2008.

METHODS

Retrospective data from 1422 at-risk couples who attended from January 1993 to December 2008 were studied. All couples were suspected at-risk couples based on initial screening using standard protocols. Three thalassemia carrier types including alpha(0)-thalassemia, beta-thalassemia and hemoglobin E were identified using standard methods. Data on prenatal diagnosis were collected.

RESULTS

Of the 1422 positive-screened couples, 1254 (88.2%) were diagnosed as true-positive couples. After DNA analysis, 968 of 1254 (77.2%) resulted at risk for three types of severe conditions being hemoglobin E-beta-thalassemia disease (640/968, 66.1%), homozygous alpha(0)-thalassemia (304/968, 31.4%) and homozygous beta-thalassemia (11/968, 1.1%). The remaining 1.3% of the couples were at risk for more than one disease. After genetic counseling, prenatal diagnosis was performed on 756 couples (78.1%). The proportions of affected fetuses, thalassemia carriers and unaffected fetuses were 26.9, 50.0 and 23.0%, respectively.

CONCLUSION

Implementation of a prevention and control program accompanying with a referral system for prenatal diagnosis is technically feasible in northeast Thailand and a large number of severe thalassemia diseases have been prevented during the past 16 years of operation.

Hemoglobin Q-Thailand related disorders: origin, molecular, hematological and diagnostic aspects

We describe the molecular and hematological profiles of thalassemia syndromes caused by interactions of hemoglobin (Hb) Q-Thailand [α74(EF3) Asp-His] and various hemoglobinopathies found in 52 unrelated adult Thai subjects. Ten genotypes including several previously undescribed conditions were observed, which were classified into 4 groups. Group I included 26 Hb Q-Thailand heterozygotes and a homozygotous subject. Group II included subjects with Hb Q-Thailand and other α-thalassemia alleles in trans including 1 compound Hb Q-Thailand/α(+)-thalassemia (-α(3.7)), 2 Hb Q-Thailand/Hb Constant Spring disease and 6 Hb H/Q-Thailand disease. The average levels of Hb Q-Thailand were found to be 29.8%, 82.3%, 34.7%, 49.2-49.3% and 79.4%, respectively. Both Hbs Bart's and H were observed in addition to Hb Q-Thailand in all 6 cases with Hb Q-H disease but not in a homozygous Hb Q-Thailand. Group III included 7 double heterozygotes for Hb Q-Thailand/Hb E, 3 Hb Q-Thailand/Hb E/α(+)-thalassemia (-α(3.7)), 3 heterozygous Hb Q-Thailand/homozygous Hb E and 1 triple heterozygote for Hb Q-Thailand/Hb Constant Spring/Hb E. In this group, Hbs E (α(A)(2)β(E)(2)), Q-Thailand (α(QT)(2)β(A)(2)) and QE (α(QT)(2)β(E)(2)) were observed on both HPLC and capillary electrophoresis. The Hb QE, rather than Hb Q-Thailand, was detected in all 3 cases with heterozygous Hb Q-Thailand and homozygous Hb E. The remaining two cases in group 4 were double heterozygotes for Hb Q-Thailand and β(0)-thalassemia in which Hb Q-Thailand, elevated Hb A(2) (α(A)(2)δ(2)), and Hb QA(2) (α(QT)(2)δ(2)) were detected. DNA analysis identified the Hb Q-Thailand mutation (α74: GAC-CAC) and the linked (-α(4.2)) in all cases. Analysis of α-globin gene haplotype provided the first evidence of a single origin of this Hb variant in Thai population.

Improvement of alpha(0)-thalassemia screening using combined osmotic fragility, dichlorophenolindophenol and Hb H inclusion tests

BACKGROUND

Screening for alpha(0)-thalassemia is usually done using osmotic fragility (OF) test or reduced erythrocyte indexes, both with high sensitivity, but accurate diagnosis requires PCR analysis. However, a low specificity of screening leads to unnecessary PCR workload during a massive population survey. We have established a more effective screening strategy using a combination of three simple tests.

METHODS

The study was done on 206 subjects with hypochromic microcytosis. Methods include osmotic fragility (OF) test, a dichlorophenolindophenol (DCIP) test for Hb E, a modified Hb H inclusion test, Hb and PCR analyses.

RESULTS

Initial screening with combined OF and DCIP tests identified 9 subjects with negative OF and DCIP tests (-/-), 58 with positive OF test but negative DCIP test (+/-), 13 with negative OF but positive DCIP tests (-/+) and 126 subjects with positive in both tests (+/+). Hb H inclusion was observed in 52 of 206 subjects including 1 in OF/DCIP (-/-), 31 in OF/DCIP (+/-) and 20 in OF/DCIP (+/+) groups. Among these 52 subjects, PCR analysis identified alpha(0)-thalassemia in 28 of 31 (+/-) and 16 of 20 (+/+) groups. Five of 106 subjects with negative Hb H inclusion in the (+/+) group were found to be heterozygous (3 of 5) and homozygous (2 of 5) Hb E co-inherited with alpha(0)-thalassemia.

CONCLUSIONS

Hb H inclusion is not an appropriate screening test for alpha(0)-thalassemia in a region where Hb E is common. However performance of the test in the OF/DCIP (+/-) group would enhance the specificity of screening and result in elimination of almost 50% of cases that would have required further PCR confirmation.

Application of maternal plasma DNA analysis for noninvasive prenatal diagnosis of Hb E-beta-thalassemia

To establish simple noninvasive prenatal diagnosis of common beta-thalassemia in Southeast Asia, we have evaluated the possibility of identifying the 3 most common beta-thalassemia genes [beta(E), beta(17A-T), and beta(41/42(-CTCC))] by analysis of fetal DNA in maternal plasma using combined conventional polymerase chain reaction (PCR) and real-time quantitative PCR. Maternal plasma was obtained from peripheral blood of Thai pregnant women collected during the first and second trimesters of gestation. DNA was prepared from 200 microL plasma using a QIAmp Blood Mini Kit. Identifications of the beta(E), beta(41/42(-CTTT)), and beta(17A-T) in plasma DNA were carried out using semi-nested (for beta(E)) and nested (for beta(41/42) and beta(17)) real-time allele-specific PCR methodologies, and the results were compared with those obtained on fetal tissue analysis with routine invasive procedure. Twenty-six fetal beta(E) genes were correctly identified by maternal plasma DNA analysis of 39 pregnant women investigated. The fetal beta(41/42) and beta(17) mutations were detectable in 6 of 12 and 4 of 9 maternal plasma specimens, respectively, which were in concordance with the results obtained by routine invasive procedure. The noninvasive prenatal diagnostic methods developed should potentially prove useful for detection of paternally inherited mutation and for providing the exclusion of pregnancies at risk for this common genetic disorder in the region.

Role of NF-kappa B in regulation of apoptosis of erythroid progenitor cells

Erythropoietin (EPO) and interferon-gamma (IFN-gamma) added to human erythroid progenitor cells purified from peripheral blood (erythroid colony-forming cells; ECFC) significantly reduces apoptosis as assessed by flow cytometry (FCM) using annexin V. To clarify the role of NF-kappaB in the regulation of the apoptosis of erythroid progenitor cells, cyclosporin A (CsA), which blocks dissociation of the NF-kappaB complex, was added to serum-free cultures of ECFC. CsA induced the apoptosis of ECFCs in the presence of EPO or IFN-gamma, but at different magnitudes. In the presence of a relatively low concentration of CsA (10 microm), apoptosis was induced only in cultures with EPO. The direct involvement of NF-kappaB was then assessed by Western blotting and confocal microscopy. In the presence of EPO, NF-kappaB was abundant both in the cytoplasm and in the nucleus, and nuclear expression was diminished after adding CsA. In contrast, NF-kappaB was undetectable in the nucleus in the presence of IFN-gamma. The effect of CsA on mitochondrial function was investigated by determining the DeltaPsim and reactive oxygen species production. CsA disturbed the transmembrane potential in the presence of either EPO or IFN-gamma, although the viability of the cells was maintained in the presence of IFN-gamma plus CsA. These results indicate that IFN-gamma reduced the apoptosis of erythroid progenitor cells through a unique signaling pathway that is independent of NF-kappaB translocation, and which is not mediated by modulating mitochondrial function, whereas EPO reduced apoptosis through NF-kappaB translocation to the nucleus.

Frequency Distribution and Haplotypic Heterogeneity of beta(E)-Globin Gene among Eight Minority Groups of Northeast Thailand

The frequencies of hemoglobin E and beta(E)-globin gene haplotypes were determined in eight minority groups living in the northeastern part of Thailand. A total of 478 samples of eight minority groups, namely Soui, Thai Khmer, So, Yor, Phuthai, Thai Puan, Thai Loei and Thai Dam, were examined. High prevalences of hemoglobin E (>50%) were observed in Soui, Thai Khmer, So, Yor and Phuthai inhabiting the region near Cambodia and Laos. Thai Puan, Thai Loei, Thai Dam and native Thai living in the same geographical area had prevalences of 42.6, 35.9, 21.4 and 27.9%, respectively. A prevalence of 9.5% was found among the Thai with Chinese background living in the same area. Beta-globin gene haplotypes analysis demonstrated that most of the beta(E)-globin genes in these Thai populations were associated with two haplotypes: (- + - + + + -) and (+ - - - - + -) on chromosomes with framework 2 variety. Some beta(E)-globin genes in Soui and Thai Khmer groups were associated with the framework 3 chromosome. Genetic distances based on the beta( )-globin gene haplotypes between minority groups revealed that Soui and Thai Khmer were closely related to each other. This finding has a valuable implication for study of the origin and spread of hemoglobin E in the region.

Molecular taxonomy of a new potyvirus isolated from chilli pepper in Thailand

A virus isolated from chilli pepper plants in Kamphaengsaen, Nakorn Pathom, showing vein banding mottle symptoms was classified using sequence analysis and phylogeny of the coat protein gene and 3' noncoding region (3'NCR). This virus was found to be a typical potyvirus on the basis of particle morphology, biological properties and cytopathology. The 3'terminus region of the genome of 1,309 nucleotides, representing the viral coat protein gene and 3' NCR was cloned and sequenced. Nucleotide sequence analysis indicated that the 3' region of the viral genome had a poly A tail of at least 12 nucleotides, a noncoding region of 272 nucleotides, a coat protein gene of 864 nucleotides and 161 nucleotides representing the 3' terminus of the polymerase gene. The amino acid sequence of the coat protein was compared with those of 23 distinct potyviruses, and 63.1% shown to be the highest homology. However the 3' NCR had, at most, 29.7% random homology, thus indicating that this virus is a distinct species in the genus Potyvirus in the family Potyviridae. The result is well supported by previous studies on the biology and biochemical properties of this virus.

Reduced deformability of thalassemic erythrocytes and erythrocytes with abnormal hemoglobins and relation with susceptibility to Plasmodium falciparum invasion

A number of genetically variant erythrocytes showed decreased deformability of both intact cells and membranes prepared therefrom as measured by laser diffractometry. Erythrocytes associated with minor or no clinical symptoms (eg, alpha-thalassemia traits, hemoglobin [Hb] E trait, Hb Constant Spring trait), which showed only a minimal decrease in deformability, were, in general, invaded efficiently by the malarial parasite Plasmodium falciparum. Other variant erythrocytes (beta-thalassemia/Hb E, homozygous Hb E, homozygous Hb Constant Spring, Hb H, Hb H/Hb Constant Spring) with low deformability showed different degrees of reduction in invasion susceptibility, most of which were less than proportional with deformability decrease. It is concluded that parasite invasion is only weakly related to gross cell deformability, which in turn depends on various factors other than membrane deformability.