Clusters of mature HIV-1 particles resembling biofilms were also detected at the surface of infected MOLT cells (human acute lymphoblastic leukemia, T-cells) (30), at the surface of primary CD4(+) T-cells upon in vitro HIV-1 infection (69, 70), and at the surface of CD4(+) T-cells from HIV-1-infected patients (69). Here, CD4 is linked to HIV-1 infection.