Morphological differentiation of human SH-SY5Y neuroblastoma cells inhibits human immunodeficiency virus type 1 infection

We have studied human immunodeficiency virus type 1 (HIV-1) infection in human SH-SY5Y neuroblastoma cells at various stages of morphological differentiation. Two days’ treatment of the cells with retinoic acid (RA) or dibutyryl cAMP (db-cAMP) resulted in the appearance of elongated neurites and enhanced production of 160K to 200K neurofilament proteins as shown by indirect immunofluorescence. DNA synthesis was reduced only in RA-treated cells as detected by 5-bromo- 2-deoxyuridine incorporation. The cells were infected with two T-lymphotropic virus strains (IIIB and NDK) and two fresh isolates (39001 and 46001) from bron- choalveolar lavage samples of AIDS patients. The latter two isolates were unable to form syncytia in infected CD4-positive T-lymphoblastoid C8166 cells which was in contrast to our T-lymphotropic virus strains. Interphase in situ hybridization showed that 14 to 16 % of SH- SY5Y cells become positive for HIV-1 DNA. Regardless of the virus strain, morphological differentiation of the cells with RA or db-cAMP inhibited infection by 50 % at a single cell in situ resolution. Nested PCR confirmed the presence of proviral DNA in the infected cells. These results show that human neuroblastoma cells, tumour cells of neuroectodermal origin, can be infected by different HIV-1 isolates and that the infection is inhibited by neurotypic cell differentiation.