Comparison of neutralization profiles for anti-HCV reactive donor samples with or without detectable HCV RNA.

BACKGROUND AND OBJECTIVES: At Japanese Red Cross (JRC) Blood Centers, all donated blood is screened for hepatitis C virus (HCV) by serological and nucleic acid amplification testing. Donor plasma that tested reactive for anti-HCV by serological test is disqualified even if the donor tests negative for HCV RNA. These test results reflect both true-positive results because of past HCV infection and false-positive results because the cross-reactivity of plasma IgG, which current testing methods are unable to distinguish. To characterize these antibody test results, we examined the neutralizing activity of these plasma samples. MATERIAL AND METHODS: Donor plasma samples that tested reactive for anti-HCV by serological test but negative for HCV RNA (n = 43) were analysed for determining their neutralizing activities measured by the inhibition of the cellular entry of pseudoparticles harbouring HCV envelope glycoproteins (HCVpp). RESULTS: Strong and broad neutralizing activities against HCVpp entry similar to the samples that tested reactive for anti-HCV serological test and positive for HCV RNA (considered to be derived from individuals with chronic HCV infection) were observed in three of 43 plasma samples from donors who tested anti-HCV reactive but HCV RNA negative. CONCLUSION: By examining the neutralizing activities of plasma samples, we identified individuals with a past HCV infection from those in whom we were unable to confirm HCV infection according to the current testing algorithms of JRC, which do not perform anti-HCV confirmatory tests.

A novel mutation of the GATA site in the erythroid cell-specific regulatory element of the ABO gene in a blood donor with the Am B phenotype.

The Am and Bm phenotypes are characterized by weak expression of the A or B antigens, respectively, by red blood cells with a normal expression by the saliva of secretors. Deletion of the regulatory element in the first intron of the ABO gene and disruption of the GATA motif in the element were found to be responsible. In this study, we identified a novel mutation within the GATA motif (G>C substitution at position c.28 + 5830) in the regulatory element of the A allele that might diminish transcription activity causing the generation of the Am B phenotype.

A new transfectant panel cell line-based MoAb-independent antigen capture assay system for detection of CD36 antibody.

BACKGROUND AND OBJECTIVES: CD36 antibody (Ab) causes several disorders: neonatal alloimmune thrombocytopenia, platelet transfusion refractoriness and non-haemolytic transfusion reactions. However, there is no gold-standard test for CD36 Ab. MATERIALS AND METHODS: We developed a transfectant panel cell line-based MoAb-independent antigen capture assay system for detection of CD36 Ab and compared it with the monoclonal antibody-specific immobilization of platelet antigens (MAIPA) system in terms of sensitivity and specificity. RESULTS: Our new system was characterized by (1) gene-transfected cell lines, but not panel platelets; (2) not being hampered by HLA Abs; and (3) no need to use CD36 MoAbs to ensure the antigen specificity of this detection system. In addition, it showed a much better receiver operating characteristic curve than the MAIPA system. CONCLUSIONS: The present results indicate that our new system permits highly sensitive and specific detection of CD36 Ab.

Significant background rates of HBV and HCV infections in patients and risks of blood transfusion from donors with low anti-HBc titres or high anti-HBc titres with high anti-HBs titres in Japan: a prospective, individual NAT study of transfusion-transmitted HBV, HCV and HIV infections.

BACKGROUND: The Japanese Red Cross (JRC) conducted a prospective study to evaluate the frequency of transfusion-transmitted HBV, HCV and HIV infections to assess the risk of transfusion of blood components routinely supplied to hospitals. STUDY DESIGN AND METHODS: Post-transfusion specimens from patients at eight medical institutes were examined for evidence of infection with HBV (2139 cases), HCV (2091) and HIV (2040) using individual nucleic acid amplification testing (NAT). If these specimens were reactive, pre-transfusion specimens were also examined for the virus concerned by individual NAT. In the event that the pre-transfusion specimen was non-reactive, then all repository specimens from implicated donors were tested for the viruses by individual donation NAT. In addition, a further study was carried out to evaluate the risk of transfusion of components from donors with low anti-HBc titres or high anti-HBc with high anti-HBs titres. RESULTS: Transfusion-transmitted HCV and HIV infections were not observed. One case of post-transfusion HBV infection was identified (rate, 0·0004675; 95% CI for the risk of transmission, 1 in 451-41,841). The background rates of HBV, HCV and HIV infections in patients prior to transfusion were 3·4% (72/2139), 7·2% (150/2091) and 0% (0/2040), respectively. Sixty-four anti-HBc- and/or anti-HBs-reactive blood components were transfused to 52 patients non-reactive for anti-HBc or anti-HBs before and after transfusion (rate, 0; 95% CI for the risk of transmission, <1 in 22). CONCLUSION: This study demonstrated that the current criteria employed by JRC have a low risk, but the background rates of HBV and HCV infections in Japanese patients are significant.

Genetic polymorphisms of tumour necrosis factor receptor superfamily 1A and 1B affect responses to infliximab in Japanese patients with Crohn's disease.

BACKGROUND: Tumour necrosis factor alpha is the key inflammatory cytokine involved in the pathogenesis of Crohn's disease. Infliximab, a chimaeric monoclonal antibody of tumour necrosis factor-alpha is successfully used for the treatment of Crohn's disease, although the response to infliximab therapy differs among patients. The genetic background of the individual may partially explain the differences of the responsiveness. AIM: To investigate whether the polymorphisms in these genes are associated with the response to infliximab treatment as tumour necrosis factor-alpha exerts its biological activity through TNF receptor superfamily 1A and 1B. METHODS: Eighty Crohn's disease patients were enrolled in the study and classified into responder and nonresponder according to the efficacy of infliximab treatment. Single nucleotide polymorphisms of TNF receptor superfamily 1A (rs767455 and rs4149570) and TNF receptor superfamily 1B (rs1061622, rs1061624 and rs3397) were determined. RESULTS: The minor allele carrier of rs767455 showed a significant association with a lack of efficacy compared to the major genotype (OR = 0.26; 95% CI: 0.08-0.91). A TNF receptor superfamily 1B haplotype inferred by rs1061624 and rs3397 also showed significant differences in the distribution between responder and nonresponder (P = 0.01). CONCLUSION: These results suggest that tumour necrosis factor receptor genotypes may be involved in the different responses to infliximab in Japanese patients with Crohn's disease.

Secondary erythrocytosis associated with distal renal tubular acidosis.

AIMS: Diagnosis and classification of renal tubular acidosis (RTA) have traditionally been made on the basis of functional studies. Despite recent expanding knowledge about the molecular abnormalities involved in renal bicarbonate (HCO3-) and H+ transport, the pathophysiology of secondary erythrocytosis in association with distal RTA remains obscure. CASE HISTORY: A 2-month-old boy with severe hyperchloremic metabolic acidosis with positive urine anion gap was diagnosed with distal RTA. Replacement therapy with sodium bicarbonate and potassium citrate succeeded in improving his metabolic acidosis and growth. His renal function remained normal. He had persistent erythrocytosis. CONCLUSION: Secondary erythrocytosis is a rarely reported association of distal RTA. It may increase the risk of thromboembolism.

Discordant phenotypic expression of Alport syndrome in monozygotic twins.

BACKGROUND: Alport syndrome is a genetically heterogeneous disorder, but most patients showed the X-linked form resulting from mutations in the COL4A5 gene. A few cases of mosaicism in Alport syndrome have been reported. METHODS: We describe the case of an 8-year-old boy with mosaicism in Alport syndrome. Punch skin biopsies were obtained from the patient's mother and monozygotic twin brother. Five biopsy specimens from non-Alport patients were used as controls. Immunohistochemical analysis was performed using rat monoclonal antibodies towards individual collagen IV(NC) domains. RESULTS: Kidney tissue of the patient showed: mosaic expression of alpha3(IV), alpha4(IV) and alpha5(IV) in the glomerular basement membrane (GBM), distal tubular basement membrane (TBM) and Bowman's capsule; mosaic alpha6(IV) expression in the Bowman's capsule and distal TBM; and well-preserved expression of alpha1(IV) and alpha2(IV). The patient's skin exhibited mosaic alpha5(IV) expression. His mother and monozygotic twin brother disclosed a normal linear staining of alpha5(IV) in their epidermal basement membranes. This unusual mosaicism of alpha3(IV), alpha4(IV), alpha5(IV) and alpha6(IV) is consistent with a pattern of female heterozygotes of Alport syndrome. CONCLUSION: This discordant phenotypic expression of Alport syndrome in monozygotic twins with unaffected parents suggests possible somatic mosaicism in the COL4A5 gene.

Clinical and mutational characteristics of X-linked agammaglobulinemia and its carrier identified by flow cytometric assessment combined with genetic analysis.

BACKGROUND: X-linked agammaglobulinemia (XLA), caused by mutations in Bruton's tyrosine kinase (BTK ), is the most common form of inherited antibody deficiency. We previously reported that a flow cytometric evaluation of BTK expression in monocytes could easily detect XLA as well as its carrier. OBJECTIVE: Our purpose was to perform further flow cytometric analysis in additional XLA families in Japan. METHODS: In all, 106 hypogammaglobulinemic males (from 91 families) of various ages with a lack of mature B cells (<1%) were investigated. RESULTS: Flow cytometric assessment revealed the deficient BTK expression status in 78 families (93 patients), and mutations in BTK were identified in 76 of 78 families with presumed XLA. Of the patients with normal BTK expression, 2 showed missense mutations in which the normal amount of altered BTK transcript would cause the XLA phenotype. As many as 30% of these patients with XLA were clinically or genetically recognized beyond 5 years of age. Higher concentrations (>300 mg/dL) of serum IgG were evident in the cases diagnosed among adults, seemingly preventing severe infections. Fifty-seven of 70 mothers of patients with BTK deficiency were diagnosed as obligate carriers on the basis of a bimodal BTK expression pattern. Nine of the remaining 13 mothers showing nonmosaic BTK expression had no mutations in 2 alleles; surprisingly, the other 4 mothers had the mutated alleles. CONCLUSIONS: A diagnostic approach based on flow cytometric assessment for XLA should be initially considered in genetic investigation of antibody deficiencies, regardless of the patient's age.