Interleukin-1 Mediates a Rapid Inflammatory Response After Injection of Adenoviral Vectors into the Brain

Abstract

Adenovirus-mediated gene transfer into the brain is associated with significant inflammation and activation of anti-vector and anti-transgene immune responses that curtail the gene delivery of adenoviruses and therapeutic efficacy. Elucidating the molecular mediators of inflammatory and immune responses to adenoviruses injected into the brain should allow us to inhibit their inflammatory actions, thereby reducing vector clearance and enhance adenoviral-mediated gene transfer into the CNS. Cytokines are primary mediators of the immune response and are released during inflammation. Here we report for the first time that injection of replication-deficient adenovirus vectors into the cerebral ventricles of rats causes a rapid increase in body temperature. This fever response precedes any vector-encoded transgene expression and occurs with vectors encoding no transgene, as well as with vectors encoding a therapeutic transgene i.e., HSV1-thymidine kinase. No fever is detected after infection of the striatum, an important brain target in studies on neurodegeneration. After infection of the brain ventricles, CSF levels of immunoreactive tumor necrosis factor (TNF)-alpha and interleukin (IL)-1beta increase significantly (up to 300-fold). In the hypothalamus, the locus of thermoregulation in the brain, only IL-1beta and IL-6 are significantly elevated. A neutralizing TNF-alpha antibody has no effect on adenovirus-induced fever. However, pretreatment with either the IL-1 receptor antagonist or the cyclooxygenase inhibitor flurbiprofen completely abolishes adenovirus-induced fever, suggesting that IL-1 and prostaglandins are direct mediators of this response. These results are the first to demonstrate that IL-1, but not TNF-alpha, is the main mediator of a very early inflammatory response to adenovirus in the brain.

Inflammation and adaptive immune responses to adenoviral vectors injected into the brain: peculiarities, mechanisms, and consequences

“…Moreover, the fever response upon injection of adenoviral vectors into the lateral ventricle is blocked by antagonists of IL-1, demonstrating that the fever response is induced by IL-1, rather than TNFa. 20 Similar increases in IL-6 and TNFa are detected upon systemic injections of adenoviral vectors. 22,23 Also, the fever response elicited was independent of the transgene encoded by the adenoviral vectors, but did depend on the integrity of the viral capsid.…”

“…[17][18][19] Cytokine 20 and cellular 21 inflammatory reactions are elicited upon injection of first-generation adenoviral vectors. This is reflected in a release of the cytokines IL-1, IL-6, TNFa, and the stimulation of a fever response, 20 when adenovirus is injected into the third ventricle. Cytokine levels increase very rapidly, with a peak observed at 1.5 h after virus injection, and a time course similar to the fever response, returning to normal within 24 h. Injection of adenovirus into the striatum elicits an increase of IL-1 and IL-6, but not TNFa or fever.…”

“…22,23 Also, the fever response elicited was independent of the transgene encoded by the adenoviral vectors, but did depend on the integrity of the viral capsid. 20 The very rapid increase in cytokine secretion and fever makes viral protein expression an unlikely explanation for these responses. Similar very rapid increases in the levels of mRNA for IL-8, and stimulation of signal transduction pathways, [24][25][26][27][28] suggest that the earliest phase (1-2 h) of inflammatory response to adenoviral vectors, both in nervous tissue as well as in other tissues, is independent of viral vector expression.…”

Intra-CSF administered recombinant adenovirus causes an immune response-mediated toxicity

“…Recently, Cartmell et al 10 showed that IL-1 is an important mediator of the innate early immune response to adenovirus in the brain. In rats, IL-1 synthesis (and not TNF-␣), was associated with the rise in body temperature observed within a few hours following intraventricular recombinant adenovirus administration.…”

“…In vivo studies showed a role of TNF-␣, IL-1 and IL-6 in initiating an aspecific early immune response. 9,10 In vitro studies also suggest a critical role of adenovirus-induced IL-8 production in eliciting an innate immune response against the vector. 11,12 In two nonhuman primates, cytokine production (IL-8 and IL-1, IL-2, IL-6, TNF-␣ and IFN-␥) in the CSF was determined 24, 48 and 72 h after intrathecal adenolacZ injection.…”