Objective: Antigen-driven B-cell proliferation and maturation occur in
germinal centres present in lymphoid tissues. This process is highly
dependent on functional interactions between B and T lymphocytes. In v
itro activation of CD40 present on B cells mimics B cell-T cell intera
ctions and allows the proliferation of normal Epstein-Barr virus (EBV)
-negative B lymphocytes. In HIV-1-seropositive individuals, B cells be
come exposed to free viral particles and to infected T lymphocytes whi
le migrating through germinal centres. The effect of HIV-1 viral expos
ure on CD40-activated B lymphocytes was therefore examined. Methods: F
reshly isolated B lymphocytes were cultured in vitro through activatio
n of CD40. B-cell proliferation, HIV-1 infectivity and viral productio
n were monitored following B-lymphocyte exposure to HIV-1. In addition
, HIV-mediated fusion between infected B cells and uninfected CD4+ T l
ymphocytes was assessed in a coculture assay. Results: EBV-negative, C
D40-activated human B lymphocytes were directly infected by HIV-1. The
infection significantly reduced their proliferation rate. Viral produ
ction was detected in B-cell culture supernatant. Numerous fusion even
ts indicated that HIV-1 infection of B lymphocytes could spread to T l
ymphocytes following HIV-1-mediated fusion of these two cell types. Co
nclusion: In view of the importance of B cell-T cell interactions in t
he maintenance of a functional immune system, disruption of B-lymphocy
te development could have direct implications on the course of AIDS pr
ogression.