Antibody masking renders HIV-1 resistant to cationic membrane filtration through alteration of its electrostatic characteristics

Previously, it was demonstrated that any human immunodeficiency virus type 1 (HIV-I) strain proliferating in peripheral blood mononuclear cells (PBMCs ) in vitro, and resuspended in seronegative plasma, could be captured effic iently (mean > 95%) by a porous polypropylene (PP) membrane modified cation ically. We investigated if this cationic membrane could capture HIV-I obtai ned from seropositive plasma, and confirmed whether this membrane was effec tive fur the preparation of safe plasma products against HIV-I transmission . Thirty-six seropositive plasma samples derived from HIV-I positive cohort s in New York and Lusaka (Republic of Zambia), including 18 cases of acquir ed immunodeficiency syndrome (AIDS) I-elated complex, AIDS and five termina l cases of AIDS, were filtered through the cationic membrane to determine t he reduction of RNA concentration, the gag p24 concentration, and infectiou s titer. Only a small reduction in RNA concentration (mean < 20%) and almos t no decrease in gag concentration (mean < 2%) were obtained. despite the f act that the infectivity was eliminated entirely by the filtration. Due to the possibility that anti-HIV-l antibodies in patients' plasma combine with HIV-1, laboratory-adapted HIV-1(HTLV-IIIB) was mixed with seropositive pla sma to test the effect of antibodies on HIV-1 adsorption, and also to inves tigate the interfacial electrokinetic potential (zeta -potential) of both i ntact and plasma-treated HIV-I. The zeta -potential of HIV-1(HTLV-IIIB) in the presence of seropositive plasma was neutral as opposed to negative when stored in seronegative plasma or culture medium. Also the rate of HIV-I ca pture by the membrane, as determined by the reduction in RNA concentration, sank from 95% to 20%, the same capture percentage observed when filtering plasma of patients. These findings suggested that in patients' plasma, the antibody-masked HIV-I comprise most of the viral population, and was not tr apped on the cationic membrane because of its electrostatic character. Conv ersely, the cationic membrane was thought to adsorb antibody-free HIV-1 exc lusively. It was suggested that each viral swarm had its own zeta -potentia l, and this difference in electrostatic character determined the extent of the viral adsorption by the cationic membrane. (C) 2001 Elsevier Science B. V. All rights reserved.