Increased production of cytokines in the brain is a common event observed during infection with neurotropic viruses such as herpesviruses, JC virus, retroviruses (HIV and HTLV-1), poliovirus, rabies virus and arboviruses (JE, St. Louis encephalitis) [
12‐
14,
16,
40]. Inflammation in the brain is usually characterized by infiltration of immune cells, which along with glial cells are key contributors of these cytokines [
13,
41,
42]. We and others have recently demonstrated
in vitro increased production of cytokines and matrix metalloproteinases (MMPs) by WNV-infected astrocytes and microglia [
11,
22,
31]. Since neurons are the prime target of WNV infection, we examined the ability of WNV-infected human neuroblatostoma cell line, SK-N-SH, in producing key cytokines. In this report for the first time we demonstrate that neurons also respond to WNV infection by up-regulating cytokines production. The sharp increase of key pro-inflammatory cytokines such as IL-1β, -6, -8 and TNF-α at day 2 after infection as determined by qRT-PCR and ELISA is significant and coincides with peak virus replication in SK-N-SH cells suggesting that active virus replication in these cells is a main determinant of cytokines up-regulation (Figure
2). Neurons secrete several cytokines under various brain insults [
43]. In the normal intact CNS, neurons are the only cell type known to produce low levels of TNF-α [
44,
45]. IL-6 mRNA has been described within hippocampal and cerebellar neurons of the adult mammalian brain [
46,
47]. Treatment of neurons with S100B induces the expression of IL-1β and -6 [
41,
48]. Neurons highly express cytokines such as IL-6, -1β, and TNF-α in neurodegenerative diseases, including AD, spinal cord injury, stroke, and sciatic nerve injury [
27‐
29,
49]. In diseases like AD and JE, increased cytokine production by dying neurons is the main determinant of cytotoxicity [
41,
50,
51]. It is important to note that in HIV, another neurotropic virus, which does not infect neurons, the main source of cytokine production are glial cells [
14,
16,
52]. However unlike HIV, WNV infection of neurons is robust, therefore based on our data, it seems likely that they may be one of the main sources of cytokines in WNV-associated neuroinflammation. Though, our data does not rule out the possibility of cytokine production by glial cells and infiltrating immune cells in WNV-infected brain. Neurons have not been implicated as a source of IL-18 in various brain insults, therefore, no change in the expression of IL-18 (data not shown) is not surprising. Moreover, literature suggests glial cells as the main source of IL-18 upon various stimuli [
53], including infection with JEV [
16] and WNV (Verma et. al., unpublished data).