A previous study aimed at concentrating antigen in plasma from
adult patients (Schüpbach, 2003). In these assays, most of the antigenwas
still found in the soluble phase, therefore, itwas considered
that itwould not be part of virus particles. Severalmechanisms can
account for the predominance of soluble p24 antigen over p24 associated
with virus particles once the immune response has started
(Schüpbach, 2003).