Maximal HIV-1 Replication in Alveolar Macrophages during Tuberculosis Requires both Lymphocyte Contact and Cytokines Yoshihiko Hoshino,1 Koh Nakata,3 Satomi Hoshino,1 Yoshihiro Honda,4 Doris B. Tse,2 Tatsuo Shioda,5 William and Michael Weiden1 N. Rom,1 1Division of Pulmonary and Critical Care Medicine, and 2Division of Infectious Disease and Immunology, Department of Medicine, New York University School of Medicine, New York, NY 10016 3Department of Respiratory Diseases, Research Institute, International Medical Center of Japan,Tokyo 162-8655, Japan 4Department of Medicine, Sendai Kosei Hospital, Sendai 980-0873, Japan 5Department of Viral Infections, Research Institute for Microbial Diseases, Osaka University, Osaka 565-0871, Japan Abstract HIV-1 replication is markedly upregulated in alveolar macrophages (AM) during pulmonary tuberculosis (TB). This is associated with loss of an inhibitory CCAAT enhancer binding pro- tein (C/EBP ) transcription factor and activation of nuclear factor (NF)- B. Since the cellu- lar immune response in pulmonary TB requires lymphocyte–macrophage interaction, a model system was developed in which lymphocytes were added to AM. Contact between lympho- cytes and AM reduced inhibitory C/EBP , activated NF- B, and enhanced HIV-1 replica- tion. If contact between lymphocytes and macrophages was prevented, inhibitory C/EBP ex- pression was maintained and the HIV-1 long terminal repeat (LTR) was not maximally stimulated although NF- B was activated. Antibodies that cross-linked macrophage expressed B-7, and vascular cell adhesion molecule and CD40 were used to mimic lymphocyte contact. All three cross-linking antibodies were required to abolish inhibitory C/EBP expression. However, the HIV-1 LTR was not maximally stimulated and NF- B was not activated. Max- imal HIV-1–LTR stimulation required both lymphocyte-derived soluble factors, and cross- linking of macrophage expressed costimulatory molecules. High level HIV-1–LTR stimulation was also achieved when IL-1 , IL-6, and TNF- were added to macrophages with cross- linked costimulatory molecules. Contact between activated lymphocytes and macrophages is necessary to down-regulate inhibitory C/EBP , thereby derepressing the HIV-1 LTR. Lymphocyte-derived cytokines activate NF- B, further enhancing the HIV-1 LTR. Key words: infection • cellular immunity • costimulatory molecules • transcription factors • derepression Introduction Worldwide, 1.86 billion persons are infected with Myco- bacterium tuberculosis and 8% of all tuberculosis (TB)* cases occur in persons coinfected with HIV. There is a synergistic Address correspondence to Michael Weiden, Division of Pulmonary and Critical Care Medicine, Department of Medicine, New York University School of Medicine, 550 First Avenue, New York, NY 10016. Phone: 212-263-7889; Fax: 212-263-8501; E-mail: weidem01@gcrc.med.nyu *Abbreviations used in this paper: AM, alveolar macrophages; BAL, bron- choalveolar lavage; CAT, chloramphenicol acetyltransferase; C/EBP , interaction between HIV-1 and M. tuberculosis. HIV-1 in- fection predisposes to activation of latent TB and accelerates the clinical course of the disease. Conversely, recent studies also demonstrate that TB accelerates the course of AIDS. In CCAAT enhancer binding protein ; EMSA, electrophoretic mobility shift assay; LTR, long terminal repeat; NF, nuclear factor; NRE, negative regulatory element; TB, tuberculosis; VCAM, vascular cell adhesion mol- ecule; VLA, very late antigen. 495 J. Exp. Med.  The Rockefeller University Press • 0022-1007/2002/02/495/11 $5.00 Volume 195, Number 4, February 18, 2002 495–505 http://www.jem.org/cgi/content/full/195/4/495