Recovery of antigenically reactive HIV-2 cores

Negative staining studies of human immunodeficiency virus (HIV) have been hampered by the fragile nature of the particles. Although detergent treatment is capable of releasing cores from HIV-2 particles, these are unstable and do not retain morphological integrity. Addition of glutaraldehyde will stabilise these structures but, if used at too high a concentration, will destroy their antigenicity. This study shows that if both detergent and glutaraldehyde are used in correct proportions, antigenically reactive cores can be recovered from HIV-2 cell cultures. More specifically we show that a mixture of 0.1% Nonidet P40 and 0.1% glutaraldehyde produces preparations of HIV-2 cores that are suitable for immune electron microscopy. These cores reacted positively, that is, formed immune complexes, with both human HIV-2 antisera and a mouse monoclonal antibody that, although directed against p24 (HIV-1), reacts also with p25 (HIV-2).