Eudora Y. D. Chow

Mannose-Binding Lectin in Severe Acute Respiratory Syndrome Coronavirus Infection

Abstract Little is known about the innate immune response to severe acute respiratory syndrome (SARS) coronavirus (CoV) infection. Mannose-binding lectin (MBL), a key molecule in innate immunity, functions as an ante-antibody before the specific antibody response. Here, we describe a case-control study that included 569 patients with SARS and 1188 control subjects and used in vitro assays to investigate the role that MBL plays in SARS-CoV infection. The distribution of MBL gene polymorphisms was significantly different between patients with SARS and control subjects, with a higher frequency of haplotypes associated with low or deficient serum levels of MBL in patients with SARS than in control subjects. Serum levels of MBL were also significantly lower in patients with SARS than in control subjects. There was, however, no association between MBL genotypes, which are associated with low or deficient serum levels of MBL, and mortality related to SARS. MBL could bind SARS-CoV in a dose- and calcium-dependent and mannan-inhibitable fashion in vitro, suggesting that binding is through the carbohydrate recognition domains of MBL. Furthermore, deposition of complement C4 on SARS-CoV was enhanced by MBL. Inhibition of the infectivity of SARS-CoV by MBL in fetal rhesus kidney cells (FRhK-4) was also observed. These results suggest that MBL contributes to the first-line host defense against SARS-CoV and that MBL deficiency is a susceptibility factor for acquisition of SARS

The interferon gamma gene polymorphism +874 A/T is associated with severe acute respiratory syndrome

BackgroundCytokines play important roles in antiviral action. We examined whether polymorphisms of IFN-γ,TNF-α and IL-10 affect the susceptibility to and outcome of severe acute respiratory syndrome (SARS).MethodsA case-control study was carried out in 476 Chinese SARS patients and 449 healthy controls. We tested the polymorphisms of IFN-γ,TNF-α and IL-10 for their associations with SARS.ResultsIFN-γ +874A allele was associated with susceptibility to SARS in a dose-dependent manner (P < 0.001). Individuals with IFN-γ +874 AA and AT genotype had a 5.19-fold (95% Confidence Interval [CI], 2.78-9.68) and 2.57-fold (95% CI, 1.35-4.88) increased risk of developing SARS respectively. The polymorphisms of IL-10 and TNF-α were not associated with SARS susceptibility.ConclusionIFN-γ +874A allele was shown to be a risk factor in SARS susceptibility.

The association of RANTES polymorphism with severe acute respiratory syndrome in Hong Kong and Beijing Chinese

BackgroundChemokines play important roles in inflammation and antiviral action. We examined whether polymorphisms of RANTES, IP-10 and Mig affect the susceptibility to and outcome of severe acute respiratory syndrome (SARS).MethodsWe tested the polymorphisms of RANTES, IP-10 and Mig for their associations with SARS in 495 Hong Kong Chinese SARS patients and 578 controls. Then we tried to confirm the results in 356 Beijing Chinese SARS patients and 367 controls.ResultsRANTES -28 G allele was associated with SARS susceptibility in Hong Kong Chinese (P < 0.0001, OR = 2.80, 95%CI:2.11–3.71). Individuals with RANTES -28 CG and GG genotypes had a 3.28-fold (95%CI:2.32–4.64) and 3.06-fold (95%CI:1.47–6.39) increased risk of developing SARS respectively (P < 0.0001). This -28 G allele conferred risk of death in a gene-dosage dependent manner (P = 0.014) with CG and GG individuals having a 2.12-fold (95% CI: 1.11–4.06) and 4.01-fold (95% CI: 1.30–12.4) increased risk. For the replication of RANTES data in Beijing Chinese, the -28 G allele was not associated with susceptibility to SARS. However, -28 CG (OR = 4.27, 95%CI:1.64–11.1) and GG (OR = 3.34, 95%CI:0.37–30.7) were associated with admission to intensive care units or death due to SARS (P = 0.011).ConclusionRANTES -28 G allele plays a role in the pathogenesis of SARS.

Association of ICAM3 Genetic Variant with Severe Acute Respiratory Syndrome

Abstract Genetic polymorphisms have been demonstrated to be associated with vulnerability to human infection. ICAM3, an intercellular adhesion molecule important for T cell activation, and FCER2 (CD23), an immune response gene, both located on chromosome 19p13.3 were investigated for host genetic susceptibility and association with clinical outcome. A case-control study based on 817 patients with confirmed severe acute respiratory syndrome (SARS), 307 health care worker control subjects, 290 outpatient control subjects, and 309 household control subjects unaffected by SARS from Hong Kong was conducted to test for genetic association. No significant association to susceptibility to SARS-CoV infection was found for the FCER2 and the ICAM3 single nucleotide polymorphisms. However, patients with SARS homozygous for ICAM3 Gly143 showed significant association with higher lactate dehydrogenase levels (P=.0067; odds ratio [OR], 4.31 [95% confidence interval [CI], 1.37–13.56]) and lower total white blood cell counts (P=.022; OR, 0.30 [95% CI, 0.10–0.89]) on admission. These findings support the role of ICAM3 in the immunopathogenesis of SARS.

Robertsonian translocation as an acquired karyotypic abnormality in leukaemia

Robertsonian translocations, although relatively common as a constitutional genetic aberration, are rarely encountered in leukaemia. We report a case of acute myeloid leukaemia which showed an acquired Robertsonian translocation in the form of der(14;21) by cytogenetic analysis of leukaemic cells. This was confirmed by the PHA‐stimulated culture of peripheral blood lymphocytes. A review of the literature identifies only eight reported cases of acquired Robertsonian translocations in leukaemia. In the majority of cases the Robertsonian translocation occurs as a secondary change in a complex abnormal clone, whereas in two out of nine patients reported, including ours, it is found as a sole karyotypic abnormality.

Molecular Diagnosis of a Case of Hb Phnom Penh [α117(GH5)Phe-I1e-α118(H1)Thr (α1)]

We report the first case of Hb Phnom Penh where a molecular study was done on the patients sample. The result confirmed the predicted DNA sequence change involved in the mutation, which was delineated by another group in 1998 using amino acid analysis.

Genetic association between germline JAK2 polymorphisms and myeloproliferative neoplasms in Hong Kong Chinese population: a case-control study.

BackgroundMyeloproliferative neoplasms (MPNs) are a group of haematological malignancies that can be characterised by a somatic mutation (JAK2V617F). This mutation causes the bone marrow to produce excessive blood cells and is found in polycythaemia vera (~95%), essential thrombocythaemia and primary myelofibrosis (both ~50%). It is considered as a major genetic factor contributing to the development of these MPNs. No genetic association study of MPN in the Hong Kong population has so far been reported. Here, we investigated the relationship between germline JAK2 polymorphisms and MPNs in Hong Kong Chinese to find causal variants that contribute to MPN development. We analysed 19 tag single nucleotide polymorphisms (SNPs) within the JAK2 locus in 172 MPN patients and 470 healthy controls. Three of these 19 SNPs defined the reported JAK2 46/1 haplotype: rs10974944, rs12343867 and rs12340895. Allele and haplotype frequencies were compared between patients and controls by logistic regression adjusted for sex and age. Permutation test was used to correct for multiple comparisons. With significant findings from the 19 SNPs, we then examined 76 additional SNPs across the 148.7-kb region of JAK2 via imputation with the SNP data from the 1000 Genomes Project.ResultsIn single-marker analysis, 15 SNPs showed association with JAK2V617F-positive MPNs (n = 128), and 8 of these were novel MPN-associated SNPs not previously reported. Exhaustive variable-sized sliding-window haplotype analysis identified 184 haplotypes showing significant differences (P < 0.05) in frequencies between patients and controls even after multiple-testing correction. However, single-marker alleles exhibited the strongest association with V617F-positive MPNs. In local Hong Kong Chinese, rs12342421 showed the strongest association signal: asymptotic P = 3.76 × 10−15, empirical P = 2.00 × 10−5 for 50,000 permutations, OR = 3.55 for the minor allele C, and 95% CI, 2.59-4.87. Conditional logistic regression also signified an independent effect of rs12342421 in significant haplotype windows, and this independent effect remained unchanged even with the imputation of additional 76 SNPs. No significant association was found between V617F-negative MPNs and JAK2 SNPs.ConclusionWith a large sample size, we reported the association between JAK2V617F-positive MPNs and 15 tag JAK2 SNPs and the association of rs12342421 being independent of the JAK2 46/1 haplotype in Hong Kong Chinese population.

Acute promyelocytic leukaemia with cryptic PML-RARA fusion.

A 68-year-old female presented with gum bleeding and multiple bruises. Peripheral blood counts showed pancytopenia: haemoglobin 71 g/l, platelet count 1Æ3 · 10/l and leucocytes 1Æ3 · 10/l with 15% neutrophils, 54% lymphocytes and 31% abnormal promyelocytes. The abnormal promyelocytes were heavily granulated and some had bilobed nuclei. Many faggot cells were found. The bone marrow was hypercellular and was packed with abnormal promyelocytes (top left). Cytochemical study showed that the abnormal promyelocytes were strongly positive for myeloperoxidase and chloroacetate esterase. Coagulation screening tests showed: prothrombin time 14Æ8 s (normal 10–12Æ2 s), activated partial thromboplastin time 27Æ1 s (normal 26Æ5–36Æ5 s) and D-dimer >400 ng/ml FEU (normal <200 ng/ml FEU). A provisional diagnosis of acute promyelocytic leukaemia was made. However, cytogenetic study performed by overnight fluorodeoxyuridine-synchronized culture of marrow cells showed 46,XX[20]. Reverse transcription polymerase chain reaction on RNA extracted from the marrow cells detected the PML-RARA fusion transcript, and DNA sequence analysis showed that the breakpoint in the PML gene was at the bcr1 in exon 6. Fluorescence in situ hybridization (FISH) with dual colour dual fusion probes (SpectrumOrange labelled PML and SpectrumGreen-labelled RARA) showed 46,XX.ish ins(17;15)(q21Æ1;q22)(RARA+,PML+). Nuclear FISH showed two orange PML, one green RARA and one yellow PMLRARA fusion signals (top right). Metaphase FISH shows a single PML-RARA fusion signal in chromosome 17, indicating insertion of the PML gene on 15q into the RARA gene on 17q (bottom). The diagnosis of acute promyelocytic leukaemia with cryptic PML-RARA was confirmed. The patient was treated with all-trans-retinoic acid. The t(15;17)(q22;q12) is detectable in only about 90% of APL with molecular evidence of PML-RARA fusion. In most instances, absence of the t(15;17) is a reflection of failed cytogenetic study, but about 2–3% of cases are due to cryptic PMLRARA fusion as a result of insertion of the PML gene into the RARA gene or vice versa, which is only demonstrable by FISH.

Haemoglobin Bonn in a Chinese family as a cause of spurious hypoxaemia measured by pulse oximetry

Haemoglobin (Hb) Bonn is a newly described benign Hb variant that causes falsely depressed oxygen saturation as measured by pulse oximetry. It was found to be associated with mild haemolysis. Since its first report in a German family, no further cases have been documented in the literature. We report the first Chinese family with this Hb variant and confirm its unusual clinical presentation. No evidence of haemolysis was seen. The absence of consistent abnormalities in routine Hb tests such as high-performance liquid chromatography and gel electrophoresis means that spurious hypoxaemia is the only clue to its presence, and genotypic analysis is the preferred method for definitive diagnosis. Its positive identification is important for counselling and will help to avoid unnecessary investigation and treatment for this benign condition.

A unique case of familial leukaemia: maternal puerperal leukaemia followed by infantile leukaemia with monosomy 7.

A 26-year-old mother (G1P1) presented with generalized lymphadenopathy 2 months after spontaneous vaginal delivery of a normal 3Æ5 kg daughter. A peripheral blood examination (haemoglobin 133 g/l, white cell count 4Æ2 · 10 /l, platelet count 183 · 10 /l) showed occasional blasts, and a marrow biopsy showed sheets of blasts (Fig 1A) that were negative for myeloperoxidase and non-specific esterase, but showed weak granular periodic acid-Schiff positivity. Flow cytometric immunophenotyping of the blasts showed expression of CD4, CD7, CD56 and HLA-DR, but negativity for Tdt, MPO, CD13, CD34 and other B and T cell markers (CD19, CD20, CD22 and CD2, CD3, CD5, CD8). Cytogenetics (Fig 1B) showed 44, XX, t(1;6)(q21;q23),)9,)13[5]/44,idem,t(9;17)(p22;p13)[3]/46XX[10]. She was treated as undifferentiated acute leukaemia with a lymphoid leukaemia protocol (Au et al, 1998) followed by allogeneic haemopoietic stem cell transplantation (HSCT) from an unrelated donor (two younger brothers were not a human leucocyte antigen (HLA) match) in first remission (conditioning: cyclophosphamide, total body irradiation). At 18 months of age, her infant daughter presented with recurrent fever and anaemia (haemoglobin 56 g/l, white cell count 5Æ5 · 10 /l, platelet count 393 · x10 /l). The peripheral film was unremarkable, but a marrow biopsy showed 14% granulated blasts and dysplastic megakaryocytes (Fig 1C), compatible with refractory anaemia with excess blasts, stage 2 (RAEB-2). Cytogenetic study showed 45, XX, )7[2]/46, XX[2]. Using a directly labelled chromosome 7 centromeric probe (D7Z1; Vysis, Downers Grove, IL, USA), monosomy 7 was shown in 58% of marrow nucleated cells (Fig 1D). Chromosome fragility screening using diepoxybutane-induced chromosome breakage was negative, but sequencing for RUNX1 mutation was not performed. The peripheral count was static for 6 weeks and the child underwent direct HSCT from another unrelated donor (conditioning: bulsuphan, cyclophasmide, melphalan, antithymocyte globulin). Both patients remained well at 2 and 1-year follow-up respectively. They denied any herbal or toxin exposure, nor any family history of leukaemia or malignancies; and neither patient had any dysmorphic features.