No abstract

Development of antibodies (Ab) that either block the function of coagulation factor VIII (FVIII) (inhibitors) or clear it from circulation, seriously complicate the treatment of haemophilia A patients with FVIII products. Autoantibodies which develop in subjects without congenital FVIII defects, cause acquired haemophilia, a rare but life-threatening coagulopathy. Identification of the FVIII epitopes to which inhibitor Abs bind will help understanding the mechanisms of inhibitor activity, and perhaps development of new therapies. Here, we examined the FVIII peptide sequence regions recognised by anti-FVIII Ab in the plasma of six congenital and one acquired haemophilia patients with high inhibitor titers (24.4-2000 BU/ml). We used indirect ELISA and overlapping synthetic peptides, 20 residues long, spanning the sequence of the A and C FVIII domains. None of the plasma samples reacted with A1, A3 or C1 domain peptides. Six plasmas reacted with A2 and/or C2 peptides. Peptides spanning residues A2-521-690 and C2-2251-2332 were recognised most frequently and strongly. They include residues that contribute to the binding sites for activated factor IX and phosphatidyl serine/von Willebrand factor. These results suggest that anti-FVIII Abs share a pattern of antigen specificity in our panel of patients, and that exposed regions of the FVIII molecule that form functionally important binding sites elicit an intense Ab response.

No abstract

Coagulation factor VII (FVII) is a key enzyme of the extrinsic coagulation cascade that is predominantly produced by hepatocytes. The F7 gene mutations cause FVII deficiency with considerable molecular and phenotypic heterogeneity. We characterized the molecular alterations of the F7 gene and their corresponding mRNA transcripts in Iranian patients from eight unrelated families. The mutations were detected by polymerase chain reaction (PCR)-sequencing of all F7 gene exons, their flanking intronic sequences, as well as their corresponding cDNA fragments. Homozygous P303T, C91S and R304Q mutations were detected in patient 2, patient 5, and patient 6, respectively. Patient 7 was a compound heterozygote for S282R and H348R and patient 8 was a compound heterozygote for R304Q and IVS7+7A>G mutations. Furthermore, our investigation revealed three heterozygous individuals, patient 1 and patient 3 with the A244V mutation who were symptomatic and patient 4 with V(–39)I mutation who was also asymptomatic. The F7 mRNA expression analysis revealed that, except the transcript of V(–39)I, other mutation-harboring transcripts were expressed at detectable levels. In conclusion, this report reinforces the genetic and phenotypic heterogeneity of FVII deficiency. The findings of the mRNA study implied that decreased FVII protein activity subsequent to missense mutations does not completely reflect the degradation of mutation-harboring mRNA.