Neuroinflammatory responses can be mimicked in the CNS of rats treated with a bacterial component, that is, lipopolysaccharide (LPS) or the pro-inflammatory cytokine interleukin-1 (IL-1). Peripheral or central adminis- tration of LPS or IL-1b induces a clear activation of microglial and astroglial cells, and the production of, for example, interleukin-6 (IL-6), tumor necrosis factor a (TNFa) and nitric oxide. Production within the CNS of anti-inflammatory cyto- kines, including interleukin-1 receptor antagonist (IL-1ra) and interleukin-10 (IL-10) is supposed to limit the local pro-inflammatory responses and thereby their detrimental effects. IL-10 has a broader spectrum of anti-inflammatory activities because it suppresses the production of a whole number of pro-inflammatory cytokines (for example, interferon-g, IL-1a, IL-1b, IL-2, IL-6, IL-8 and TNF-a) and nitric oxide in different cell types, including glial cells, and B- and T-lymphocytes.
Transduction of NR8383 cells with LV-rIL-10 or LV-GFP resulted both in IL-10 production. The LV-GFP-induced production of rIL-10 was also observed in transduced C6 and 293T cells. The levels of rIL-10 released by the LV-rIL-10-transduced NR8383 cells were up to 600% higher (in the range from 4 to 10 days) compared with the LV-GFP-transduced cells
In LV-GFP- transduced NR8383 cells no effect on LPS-induced TNFa production was observed, indicating that the LV-GFP-induced rIL-10 production in NR8383 cells is not biologically relevant. The amount of TNFa produced and released by LPS stimulated, LV-rIL-10-transduced NR8383 cells was dramatically lower at all time-points measured.
LV-derived rIL-10 and rIL-1ra produced within the CNS did not affect TNFa, IL-6 or iNOS mRNA levels in the tissues studied that lie outside the blood–brain barrier, that is, the pituitary gland and spleen, indicating the centrally localized action of LV-derived proteins. LV expression of rIL-10 or rIL-1ra within the CNS is very effective in attenuating TNFa, IL-6 and iNOS, but not IL-4 and TGFb production, within the brain, and leaving peripheral production of the pro-inflammatory mediators intact. Recently, LV vectors expressing IL-10 or IL-1ra have been used to locally treat endotoxin-induced uveitis and it was shown not to affect the systemic immune response.
Animals transduced with LV-rIL-10 or LV-rIL-1ra produced 30–40% less TNFa and 50–75% less IL-6 protein in cortex and hippocampus compared with LV-GFP-transduced animals.
The mean clinical score during the relapse of cr-EAE (days 18-26) animals transduced with LV-GFP was 2.5 compared with 0.75 for animals transduced with LV-rIL-10 and 0.85 for animals transduced with LV-rIL-1ra.
