AIDS RESEARCH AND HUMAN RETROVIRUSES Volume 12, Number 17, 1996 Mary Ann Liebert, Inc. Alteration of CD44 Expression in HIV Type 1-Infected T Cell Lines VALÉRIE GIORDANENGO, MARTINE LIMOUSE, ALAIN DOGLIO, JOSETTE LESIMPLE, and JEAN-CLAUDE LEFEBVRE ABSTRACT CD44 is known to interfere in HIV replication and to participate in many physiological processes such as lym- phocyte binding to high endothelial venules of lymphoid tissue, lymph nodes, and mucosal endothelium. The T cell lines MOLT-4 and CEM, and CEM subclones were infected with the HIV-1 LAI strain and monitored for the expression of CD44 during the course of chronic virus production until the infected cells were at the stage of latent infection. The levels of CD44 protein expression were quantified using cell surface immuno- staining and biotinylation. The maturation of CD44 molecules was evaluated by metabolic sulforadiolabeling and CD44 mRNA was visualized by Northern blot analysis. We show a downmodulation of CD44 expression in infected T cell lines and subclones. This phenomenon was most evident at the stage of latent infection. Then, CD44 molecules were undetectable at both the protein and mRNA levels in latently infected CEM cells and CEM subclones. In addition, the 97-kDa standard CD44 isoform showed a shift upward, while detectable dur- ing the stage of chronic virus production. In latently infected MOLT-4 cells, the CD44 protein levels were dramatically decreased; CD44 mRNA was detected, but the sizes differed from the mRNA in uninfected cells. Since CD44 is known to regulate in part lymphocyte homing and HIV replication, the alterations that were observed in the expression of this molecule could interfere with the particular homing of HIV-infected cells and/or viral latency. INTRODUCTION Among the alterations to cellular immune functions caused by HIV infection, the dramatic depletion of CD4+ cells is the most striking. In fact, during the clinical course of HIV infection, the depletion of CD4+ cells is preceded by a de- cline in helper functions, and principally by a loss in the re- sponse of memory cells to recall antigen.1-3 Yet, HIV is mainly trapped in lymphoid tissues and only a small percentage of CD4+ peripheral blood cells express HIV in vivo.4'6 Moreover it has been shown that HIV-1-infected lymphocytes suffer dra- matic alterations in the expression of several surface glycopro- teins, such as (1) downregulation of CD4,7"10 CD28,11 and CD2612; (2) expression of new cellular carbohydrate antigens13; and (3) modified glycosylation of CD4514 and CD43.15 A loss of CD44 expression in HIV-infected monocytic cell lines has also been demonstrated.16 CD44, a broadly distributed cell membrane glycoprotein, is expressed as several variants generated by alternative splicing.17 Laboratoire de Virologie, Faculté de Médecine, 06107 Nice Cedex 2, France. 1615 Two major isoforms were originally described: CD44H in hematopoietic cells (thymus medulla, B cells, memory T lym- phocytes, monocytes, and granulocytes), and CD44E in epithe- lial and carcinoma cells.18 CD44E differs from CD44H essen- tially by an additional extracellular domain of 135 amino acids.18 CD44 is the major cell receptor for hyaluronate and also binds fibronectin and collagen,19-20 and therefore is involved in many physiological processes, such as cell adhesion to extracellular ma- trix and cell-cell interactions,21 lymphocyte recirculation, and lymph node homing22; lymphocyte adhesion to high endothelial cells of capillary venules23; and lymphopoiesis, metastasis, cell migration, and comitogenic factor for T cell activation.24-28 Elevated expression of CD44 has been suggested to delineate T cell subsets.29-30 In addition to the standard 85- to 95-kDa CD44H forms, several larger isoforms have been described and are gen- erated by alternative splicing of at least 12 exons.13 Interestingly, it has been shown that specific splice variants in CD44, espe- cially including the V6 exon, are implicated in normal immune responses as well as metastasis.32-35