Characterization of cleaved plasma protein S with a monoclonal antibody-based assay.
A monoclonal antibody (mAb 5A5G2) recognized cleaved plasma protein S (PS) but not uncleaved PS. Interestingly, mAb 5A5G2 did not recognize thrombin-cleaved recombinant PS. Microsequencing of cleaved plasma PS showed a Q-S-T-N amino-terminal sequence, inferring cleavage after the Arg 60 residue. The mAb epitope was located within the sequence encompassing residues 61 to 73, i.e. the carboxy-terminal part of the thrombin-sensitive region (TSR). We used this mAb to develop an ELISA assay to quantify in vivo cleaved PS. In plasma from 10 normal subjects, about 10% of PS was cleaved (7.1% to 15.4%), with a more than 2-fold increase in the corresponding sera. We found increased levels of cleaved PS in 8 patients with disseminated intravascular coagulation (DIC) and decreased levels in 22 patients on long-term oral anticoagulant therapy, whereas cleaved PS levels were similar in 8 hemophiliacs and the 10 normal subjects. Cleaved PS levels did not correlate with prothrombin fragment 1+2 levels released after cleavage by FXa in any of the groups, suggesting that circulating FXa is not the main factor involved in the production of cleaved PS in vivo.
Morboeuf
O
O
Unité INSERM 428, Faculte de Pharmacie, France.
Borgel
D
D
Gaussem
P
P
Vincenot
A
A
Pittet
J L
JL
Aiach
M
M
Gandrille
S
S
D000911:Antibodies, Monoclonal / Q000276:immunology; D000918:Antibody Specificity; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D006801:Humans; D008297:Male; D017293:Protein S / Q000032:analysis* / Q000276:immunology / Q000378:metabolism*; D011994:Recombinant Proteins / Q000276:immunology
D000911:Antibodies, Monoclonal; D017293:Protein S; D011994:Recombinant Proteins