BackgroundWe investigated the possible role of antiphospholipid (APA) and anti-human 2 -glycoprotein I (b 2 -GPI) antibodies (Ab) in thrombosis and atherosclerosis in human immunodeficiency (HIV)-positive patients, in whom they seem to be more frequent. MethodsWe measured APA and anti-b 2 -GPI Ab in 58 HIV-positive patients together with markers of disease progression, circulating b 2 -GPI, plasma lipids, biological markers of endothelial activation and integrity (plasma thrombomodulin, von Willebrand factor, vascular cell adhesion molecule 1) and with antimalonic dialdehyde antibodies (anti-MDA Ab). ResultsWe found a 41% frequency of IgG APA in the HIV-positive patients. APA IgMs were rarely positive (7%), and anti-b 2 -GPI IgGs were positive in 3·4% patients. There was no correlation between APA or anti-b 2 -GPI Ab and the presence of opportunistic infections. Although plasma thrombomodulin, von Willebrand factor and vascular cell adhesion molecule 1 were significantly increased in the HIV-positive patients, APA was correlated only with vascular cell adhesion molecule 1, suggesting that APAs are correlated with endothelial activation but not with vascular endothelial lesions. A correlation between APA and anti-MDA IgG was demonstrated using multivariate analysis (r ¼ 0·542, P < 0·0001), suggesting a relationship between the targets of these antibodies. Finally, IgG APAs are frequent in HIV infection but are not correlated with biological markers of endothelial injury. ConclusionOur results do not support a role for APA or anti-b 2 -GPI in HIV-associated silent vascular endothelial damage. However, the role of these autoantibodies in clinically relevant thrombotic events should be investigated in HIV-positive patients.