NEF PROTEIN OF HIV-1 HAS B-CELL STIMULATORY ACTIVITY

Objective: To examine the B-cell stimulatory properties of the regulat ory Nef protein of HIV-1. Methods: The effect of the HIV-1 regulatory proteins Nef, Tat and Vif, were analyzed for their ability to induce d ifferentiation of normal B lymphocytes into immunoglobulin secreting c ells (ISC). Results: A recombinant Nei protein, but neither Tat or Vif , was able to induce ISC in peripheral blood lymphocyte (PBL) cultures of HIV-1-seronegative donors. Another recombinant Nef protein, d-Nef, with a truncated amino terminal (deletion of 34 amino acids) failed t o induce B-cell differentiation. Pretreatment of the Nef protein with a polyclonal anti-Nef-antibody abrogated its B-cell stimulatory activi ty. The Nef-induced B-cell differentiation was dependent on cell-to-ce ll contact. Cell surface molecules leukocyte function-associated molec ule (LFA)-1, intracellular adhesion molecule (ICAM)-1, human lymphocyt e antigen-DR and B7 were involved in the T-B-cell interaction because monoclonal antibodies to these molecules abrogated the Nef-induced B-c ell differentiation response. The Nef protein was able to induce inter leukin (IL)-6 messenger (m)RNA and IL-6 protein secretion in PBL, with monocytes as the primary source. Conclusions: These findings indicate that regulatory (Nef) proteins of HIV-1 contribute to the intense B-c ell activation that occurs in association with HIV-1 infection. T-B-ce ll contact-dependent interaction and induction of IL-6 by these protei ns appear to play major roles in this process.