We first examined whether HIV-1 was able to bind to B cells and be transmitted to T lymphocytes through DC-SIGN using a low concentration of HIV-1 (multiplicity of infection [MOI] = 10−4, corresponding to 10 pg of p24 per 106 cells), similar to that used in studies of DC-SIGN–related transmission of HIV-1 from DC to T cells [1,27]. Here, CD209 is linked to infection.