Recombinant Human Adenovirus with Rat MIP‐2 Gene Insertion Causes Prolonged PMN Recruitment to the Murine Brain

Abstract

Single injections of recombinant cytokines/chemokines into tissue have provided insights into their possible roles during the inflammatory response. Adenoviral technology may allow us to mimic the in vivo situation more closely, with protein generated in a continuous but transient fashion. Replication-deficient human type 5 adenovirus containing a rat macrophage inflammatory protein-2 (MIP-2) gene insertion and cytomegalovirus promoter was injected into the mouse brain to investigate the inflammatory response to continuous overproduction of MIP-2. Adenovirus with a LacZ gene insertion expressing beta-galactosidase was used as a control. At doses of 10(4) to 10(7) plaque-forming units, a minimal inflammatory response was detected to the LacZ virus, with leukocyte recruitment that was restricted to the injection site. A dose of 10(7) plaque-forming units of both the LacZ and the MIP-2 vector produced extensive transgene product expression that persisted for at least 7 days. Astrocytes, recognized by their morphology, were the predominant cell type expressing MIP-2 and beta-galactosidase. A dose of 10(7) plaque-forming units of MIP-2 vector caused dramatic polymorphonuclear leukocyte (PMN) recruitment to the brain parenchyma after 2 days. PMN recruitment was still observed after 4 and 7 days, but had become more localized to the injection site and was associated with numerous foam-like macrophages. At both 2 and 7 days the blood-brain barrier was breached in the region of leukocyte recruitment. Despite the extent of leukocyte recruitment there were no overt signs of neuronal degeneration or demyelination. Our findings demonstrate that continuous production of MIP-2 in the CNS results in persistent PMN recruitment to the brain parenchyma with no evidence of tachyphylaxis. The lack of PMN recruitment to the brain parenchyma following CNS injury may be a result of deficient production of PMN chemoattractants.

Macrophage inflammatory protein-2 gene therapy attenuates adenovirus- and acetaminophen-mediated hepatic injury

“…These findings differ from previous observations pertaining to AdMIP-2 infection in lung 22 and brain, 23 where neutrophil recruitment was markedly increased in both tissues for up to 7 days after virus injection. Discrepancies between the present and previous studies may simply relate to differences in the amount or the route of AdMIP-2 administration.…”

“…AdMIP-2 has previously been shown to cause increased MIP-2 expression in many tissues after its introduction into rodents. 22,23 Overall, the results from the present study demonstrate that increasing MIP-2 levels through adenovirus-mediated gene therapy has a protective and regenerative effect in the liver during acute liver injury due to adenovirus infection and acetaminophen challenge.…”

“…The survival of AdMIP-2-pretreated mice challenged with acetaminophen was also reflected in a CXCR2-dependent reduction in histological injury, serum levels of AST and ALT and liver levels of KC. In contrast to previous studies using AdMIP-2 to overexpress MIP-2 in the lung 22 and brain, 23 AdMIP-2 delivery to the liver via an i.v. injection did not markedly augment neutrophil accumulation in hepatic tissue as determined by histology and MPO activity.…”

“…22 This construct, designated as AdMIP-2, has been used previously to promote MIP-2 protein overexpression in the lung 22 and the brain. 23 To control for the effects mediated by the adenovirus infection alone, a similar replication-defective human type 5 vector which lacked the MIP-2 gene insert (Ad70-3) was also employed in each experiment. Fresh suspensions of acetaminophen (Sigma Chemical, St Louis, MO, USA) were made daily by dissolving the drug in phosphate-buffered saline (PBS) warmed to 41°C.…”

Variation in the immune response to adenoviral vectors in the brain: influence of mouse strain, environmental conditions and priming

“…17 In contrast, in pathological conditions the presence of dendritic cells in the brain and the breakdown of BBB have been reported. 18,19 In other organs, dendritic cells play a key role in initiating immune responses to cell-associated antigens. 20 Since there are marked immunological differences between the brain and other organs, it is difficult to extrapolate the immune consequences of adenoviral vector delivery to other tissue to that of brain.…”