Acute and persistent infection of human neural cell lines by human coronavirus OC43

Human coronaviruses (HuCV) are recognized respiratory pathogens. Data accum ulated by different laboratories suggest their neurotropic potential. For e xample, primary cultures of human astrocytes and microglia were shown to be susceptible to an infection by the OC43 strain of HuCV (A. Bonavia, N. Arb our, V. W. Yong, and P. J. Talbot, J. Virol. 71:800-806, 1997). We speculat e that the neurotropism of HuCV will lead to persistence within the central nervous system, as was observed for murine coronaviruses. As a first step in the verification of our hypothesis, we have characterized the susceptibi lity of various human neural cell lines to infection by HuCV-OC43. Viral an tigen, infectious virus progeny, and viral RNA were monitored during both a cute and persistent infections. The astrocytoma cell lines U-87 MG, U-373 M G, and GL-15, as well as neuroblastoma SK-N-SH, neuroglioma H4, oligodendro cytic MO3.13, and the CHME-5 immortalized fetal microglial cell lines, mere all susceptible to an acute infection by HuCV-OC43. Viral antigen and RNA and release of infectious virions were observed during persistent HuCV-OC43 infections (similar to 130 days of culture) of U-87 MG, U-373 MG, MO3.13, and H4 cell lines. Nucleotide sequences of RNA encoding the putatively hype rvariable viral S1 gene fragment obtained after 130 days of culture were co mpared to that of initial virus input. Point mutations leading to amino aci d changes were observed in all persistently infected cell lines. Moreover, an in-frame deletion was also observed in persistently infected H4 cells. S ome point mutations were observed in some molecular clones but not all, sug gesting evolution of the viral population and the emergence of viral quasis pecies during persistent infection of H4, U-87 MG, and MO3.13 cell lines. T hese results are consistent with the potential persistence of HuCV-OC43 in cells of the human nervous system, accompanied by the production of infecti ous virions and molecular variation of viral genomic RNA.