Ex vivo inhibition of thrombus formation by an anti-glycoprotein VI Fab fragment in non-human primates without modification of glycoprotein VI expression.

OBJECTIVES: Glycoprotein (GP)VI is an attractive target for the development of new antithrombotic drugs. Its deficiency protects animals in several models of thrombosis, arterial stenosis and ischemia--reperfusion while inducing no major bleeding tendency. The Fab fragment of one anti-GPVI monoclonal antibody (9O12.2) inhibits all GPVI functions in vitro. The aim of this study was to determine the ex vivo effects of 9O12.2 Fab on hemostasis, coagulation and thrombosis in non-human primates. METHODS AND RESULTS: Blood samples were collected from cynomolgus monkeys before and after (30, 90 and 150 min, 1 and 7 days) a bolus injection of 9O12.2 Fab (4 mg kg(-1)) or vehicle. Platelet counts and coagulation tests (prothrombin time, activated partial thromboplastin time) were not modified following Fab injection. The PFA-100 closure time increased during the first hours and returned to initial values on day + 1. Platelet-bound Fab was detected from 30 min to 24 h after Fab injection without GPVI depletion at any time. Collagen-induced platelet aggregation was selectively and fully inhibited at 30 min. Thrombus formation on collagen in flowing whole blood (1500 s(-1)) was delayed and decreased, and collagen-induced or tissue factor-induced thrombin generation in platelet-rich plasma was profoundly inhibited. CONCLUSION: The anti-GPVI 9O12.2 Fab inhibits thrombus formation ex vivo in non-human primates with a composite effect on platelet activation and thrombin generation in the absence of GPVI depletion.

Alopecia areata in a rhesus monkey (Macaca mulatta).

BACKGROUND: A 14-year-old female rhesus monkey (Macaca mulatta) of Chinese origin has been suffering from alopecia universalis since childhood. METHODS: Recently, the health status of the animal was recorded comprehensively by detailed clinical examination including hematology and serology supplemented by histological and immunohistochemical investigations of skin biopsies and molecular biological techniques to clarify the causes of the persistent hair loss. RESULTS AND CONCLUSIONS: The hairless gene (hr) nonsense mutation was ruled out by polymerase chain reaction and by sequencing of the corresponding gene. Histological examinations revealed a prominent chronic lymphocytic perifolliculitis and folliculitis affecting anagen stage hair follicles as well as miniaturized hair follicles. Immunohistochemistry using the antibodies CD3, CD20 and CD4 confirmed the diagnosis of a T-cell-mediated autoimmune disease resembling alopecia areata universalis in humans.