Characterization of HIV-1-specific antibodies and HIV-1-crossreactive antibodies to platelets in HIV-1-infected haemophiliac patients

Sera from HIV-1-infected haemophiliacs were examined for human immunodefici ency virus (HIV) specific antibodies and for platelet crossreactive antibod ies. Using HIV sepharose 4B affinity columns for serum absorption, antibodi es against various HIV antigens, including HIV lysate, HIV-p24 and HIV-gp12 0, were eluted either by low or by high pH buffer. The eluates were examine d by ELISA for HIV specificity and by flow cytometry for platelet cross-rea ctivity. Two types of HIV antibodies could be eluted, i.e, acid-sensitive a nd alkaline-sensitive antibodies. HIV antibodies were obtained in 26/29 aci d eluates and in 25/29 of the alkaline eluates from HIV-lysate columns; 96% (25/26) of the acid-eluted antibodies were HIV-specific but 48% (12/25) of the alkaline-eluted antibodies also showed cross-reactivity to platelets. Of the 20 alkaline-eluted HIV-p24 antibodies, 40% (8/20) reacted specifical ly with HIV-p24 and 60% (12/20) were platelet crossreactive. In contrast, o f the alkaline-eluted HIV-gp120 antibodies (n=17), 88% (15/17) were HIV gp1 20-specific and only 12% (2/17) were platelet crossreactive. Western blot a nalysis of platelets demonstrated that the anti-p24 antibodies recognized t hree bands with approximate molecular weights of 72 000 to 95 000. 69% of t he serum antiplatelet antibodies showed platelet glycoprotein IIbIIIa speci ficity. Anti-HIV antibodies could be eluted from platelets. Hence, platelet crossreactive antibodies in HIV infection are primarily alkaline-sensitive and are associated predominantly with HIV p24 antibody; these antibodies m ay play a role in the immune thrombocytopenia of HIV-infected haemophiliacs .