title: The evaluation of platelet function in HIV infected, asymptomatic treatment-naïve individuals using flow cytometry.
abstract: BACKGROUND
  Human immunodeficiency virus (HIV) induces inflammation and platelet activation. People living with HIV are at increased risk of thrombotic events. Activated platelets link inflammation with thrombosis. However platelet function in HIV remains unclear. P-selectin (CD62P), a marker of platelet activation, and platelet glycoprotein GPIV (CD36) a marker of platelet aggregation, can be measured using flow cytometry. We raise a hypothesis that HIV alters the signalling pathways involved in normal platelet function. We evaluated platelet function in HIV using a whole blood platelet flow cytometry based assay.
  
  
  METHODS
  Fifty-eight antiretroviral therapy naïve HIV infected and 38 HIV negative individuals were recruited in a clinic in Cape Town. Platelet surface CD36 and CD62P were measured using flow cytometry. These were then correlated with CD4 count, viral load and %CD38 on CD8+ T-cells. Platelet function was evaluated using adenosine diphosphate, arachidonic acid and collagen at varying concentrations.
  
  
  RESULTS
  The HIV group showed increased levels of %CD62P (median 5.51[3.03- 10.11] vs. Control group 2.14[0.19 - 3.59], p<0.0001. This correlated with Viral load (r=0.336, P=0.008). The HIV group also showed increased levels of platelet %CD36 21.93[11.03-44.92] vs. Control 16.15[2.24-25.37], p=0.0087) which correlated with viral load (r=0.398, p=0.024). The HIV group showed a hyper response to AA and collagen at various concentrations. Notably, the HIV group only showed a hyper response to ADP at a maximal concentration of 20 μM (median CD62P MFI, 1.91[1.64-4.95] vs. Control 1.75[1.45-2.44] p=0.0279.
  
  
  CONCLUSIONS
  The measurement of platelet function using flow cytometry is a rapid technique for the evaluation of platelet signalling pathways that may be modified in HIV infected individuals.
authors.affiliation: Divisions of Haematology, Department of Pathology, Stellenbosch University and NHLS, Tygerberg, South Africa.
authors.forename: Bongani B
authors.initials: BB
authors.lastname: Nkambule
authors.affiliation: Department of Biomedical sciences, Faculty of Health and wellness sciences, Cape Peninsula University of Technology, Bellville, South Africa.
authors.forename: Glenda Mary
authors.initials: GM
authors.lastname: Davison
authors.affiliation: Divisions of Haematology, Department of Pathology, Stellenbosch University and NHLS, Tygerberg, South Africa. Electronic address: hipp@sun.ac.za.
authors.forename: Hayley
authors.initials: H
authors.lastname: Ipp
mesh_terms: D000328:Adult; D001792:Blood Platelets / Q000821:virology; D018955:CD36 Antigens / Q000097:blood; D015331:Cohort Studies; D003094:Collagen / Q000737:chemistry; D003430:Cross-Sectional Studies; D018450:Disease Progression; D005260:Female; D005434:Flow Cytometry / Q000379:methods*; D015658:HIV Infections / Q000097:blood* / Q000276:immunology; D006801:Humans; D008297:Male; D019007:P-Selectin / Q000097:blood; D015539:Platelet Activation; D010974:Platelet Aggregation; D010979:Platelet Function Tests / Q000379:methods*; D012367:RNA, Viral / Q000032:analysis; D015398:Signal Transduction
chemical_list: D018955:CD36 Antigens; D019007:P-Selectin; D012367:RNA, Viral; C546937:SELP protein, human; D003094:Collagen