We previously reported that the neurovirulent influenza A virus strain, AIWSN/33 has strong affinity for the substantia nigra (SN) in mouse brain. In this study, we used a neuron-glia co-culture system in order to observe the cellular responses to viral infection. Co-cultured cells were infected with the A/WSN/33 strain and were examined immunohistochemically. Viral antigens were strictly confined to the neuronal cell bodies and their neurites. More than 90% of tyrosine hydroxylase (TH)-positive neurons in the SN were also positive to anti-WSN antibody. There was no increase in class I major histocompatibility complex (MHC) expression in virus antigen positive cells. Thus, we can conclude that the virus preferentially infects neurons, mainly TH-positive neurons in the SN. An antigen presenting response mediated by class I MHC was not observed in infected neurons.