Soluble factors from T cells inhibiting X4 strains of HIV are a mixture of β chemokines and RNases.

T-cell-derived soluble factors that inhibit both X4 and R5 HIV are recognized as important in controlling HIV. Whereas three β chemokines, regulated-on-activation normal T-cell expressed and secreted (RANTES), macrophage inflammatory protein (MIP)-1α, and MIP-1β, account for the suppression of R5 HIV by blockade of HIV entry, the major components responsible for the inhibition of X4 HIV strains have not been identified previously. We identify these factors primarily as a mixture of three β chemokines [macrophage-derived chemokine (MDC), thymus and activation-regulated chemokine (TARC), and I-309] and two RNases (angiogenin and RNase 4) of lesser potency and show that in a clade B population, some correlate with clinical status and are produced by both CD4(+) and CD8(+) T cells (chemokines, angiogenin) or only by CD8(+) T cells (RNase 4). The antiviral mechanisms of these HIV X4-suppressive factors differ from those of the previously described HIV R5-suppressive β chemokines.