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CD43 is a cell surface sialoglycoprotein expressed by most cells of hematopoietic origin, including all T lymphocytes. Elimination of CD43 expression by gene targeting in the CEM T cell line results in its increased homotypic adhesion and binding to HIV-1 gp120. Here we report that the CD43-negative CEM cells show increased susceptibility to HIV-1 infection and increased viral replication compared with the parental CD43+ CEM cell line. Increased HIV-1 replication also was observed in CEM cells with diminished CD43 expression secondary to functional inactivation of a single CD43 allele. The CD43- CEM cells were more susceptible to HIV-1-induced cytopathicity than their CD43+ counterparts. HIV-1 replication also was increased in the CD43- CEM cells after transfection with the infectious HIV molecular clone pNL4-3. These data suggest that factors that diminish CD43 expression on T lymphocytes may enhance their susceptibility to HIV-1 infection.

Sera from human immunodeficiency virus type 1 (HIV-1)-infected and -noninfected individuals were screened for antibodies that could bind to native T cell differentiation antigens. Antibodies that could immunoprecipitate CD43 (sialophorin, leukosialin) from a T cell lymphoma line were detected in sera from 27% of patients, and antibodies that could bind specifically to transfected cells expressing CD43 were detected in 47% of patients. The anti-CD43 antibodies were related to HIV-1 infection in that no patients with other chronic viral infections or systemic lupus erythematosus contained such antibodies in their sera. The anti-CD43 autoantibodies bound to a partially sialylated form of CD43 expressed by normal human thymocytes, but not by normal, circulating T lymphocytes. However, the determinant(s) recognized by the anti-CD43 autoantibodies was present on a large proportion of circulating T lymphocytes, but masked from antibody recognition by sialic acid residues. These results demonstrate that HIV-1 infection is specifically associated with the production of autoantibodies that bind to a native T cell surface antigen.

T lymphocytes bound to autologous immunoglobulin (surface Ig + T cells) and serum antibodies that bind to allogeneic lymphocytes have been detected in HIV-1-infected individuals, but their significance in the immunopathogenesis of HIV-1 infection is uncertain. We tested peripheral blood from HIV-1-infected individuals to determine if surface Ig+ T cells are specific for HIV-1 infection and are associated with CD4+ lymphocyte depletion. The majority of HIV-1-infected individuals contained substantial numbers of circulating surface Ig+ T cells. The presence of such cells was restricted to seropositive individuals and not related to risk factors associated with the acquisition of HIV-1 infection. Autologous immunoglobulin was detected on both CD4+ and CD8+ cells in all patients tested. Most individuals with surface Ig+ T lymphocytes also had serum anti-T-lymphocyte antibodies. The presence of surface Ig+ T lymphocytes correlated significantly with lower absolute CD4+ lymphocyte counts only in asymptomatic, HIV-1-infected individuals.