Adenovirus Vector-Induced Innate Inflammatory Mediators, MAPK Signaling, As Well As Adaptive Immune Responses Are Dependent upon Both TLR2 and TLR9 In Vivo

Abstract

Adenovirus (Ad) vectors are promising candidates for both gene transfer and vaccine applications. In this study, we investigated the role of TLR2 in innate and adaptive immune responses to Ad and/or the transgene it expresses following systemic injection. We found that Ad directly activates ERK1/2 in vivo, but that initiation of ERK1/2 activation is primarily a MyD88/TLR2-independent, but Kupffer cell-dependent, event. The complexity of Ad-induced innate immune responses was confirmed when we also found that both TLR2 and MyD88 functions are required for the sustained activation of ERK1/2. Although we found that the initial activation of NF-κB by Ads is dependent upon MyD88, but independent of TLR2 in (non-Kupffer cells) the liver, TLR2 significantly influenced the Ad-induced late phase NF-κB activation. These very rapid responses were positively correlated with subsequent innate immune responses to the Ad vector, as our results confirmed that the induction of several cytokines and chemokines, and the expression of innate immune response genes following Ad injection were TLR2 dependent in vivo. The requirement of TLR2 in Ad-induced innate responses also correlated with significantly altered adaptive immune responses. For example, our results demonstrate that the generation of Ad-neutralizing Abs, and anti-transgene-specific Abs elicited subsequent to Ad vector treatments, are both dependent upon TLR2 functionality. Finally, we found that several Ad-induced innate immune responses are dependent on both TLR2 and TLR9. Therefore, this study confirms that several (but not all) Ad-induced innate and adaptive immune responses are TLR dependent.

Intratumor RNA interference of cell cycle genes slows down tumor progression

“…As control Ad-EGFP was ineffective, the antitumor effect was not mediated by the induction of innate immunity upon vector injection. 35 These data further showed that RNAi of cell cycle-related genes (such as PLK-1) represents a viable option in the treatment of cancer. However, as our experiments have been performed in immunodeficient mice, we have not assessed the potential impact of the immune response against Ad vectors.…”

Complex interactions with several arms of the complement system dictate innate and humoral immunity to adenoviral vectors

“…7,20,22 It has also been shown that rAd injection results in evidence of Kupffer cell toxicity within 10 min of intravenous injection, followed by complete Kupffer cell depletion by 24 h after Ad injection. 27 For this reason, we evaluated rAd-induced Kupffer cell toxicity via F4/80 staining and fluorescence microscopy in Ad-injected C3-KO, FB-KO and C1q-KO mice at 24 h.p.i.…”

“…Interestingly, we have recently revealed a similar result in Ad-injected Complement factors in innate and humoral immunity to Ad DM Appledorn et al TLR2-KO mice, and showed that IkBa degradation was completely dependent on MyD88 functionality. 7 The possibility of a direct or indirect interaction between complement and TLR-mediated signaling pathways is intriguing and relatively understudied. 33,34 Interestingly, we did not detect a role for C3 in rAd-induced ERK1/2 activation.…”

“…Although we, and others, have recently implicated intracellular signaling systems as mediating several important aspects of this response (that is, Ad interactions with the Toll-like receptor (TLR) system), it is also clear that instantaneous interactions of rAds with the extracellular pathogensensing complement system may also be significantly modulating these intracellular responses. [7][8][9][10][11][12] The complement system is an ancient defense system that innately recognizes pathogen-associated molecular patterns on a variety of organisms including bacteria, viruses and protozoan parasites. Opsonization of invaders by complement proteins facilitates downstream phagocytosis by platelets, macrophages and/or other cells that have complement receptors, initiates proinflammatory responses that enhance adaptive immune responses and facilitates destruction of some pathogens directly.…”

The impact of antigen expression in antigen-presenting cells on humoral immune responses against the transgene product

“…Insufficient co-stimulation may induce tolerance. 6 Adenoviral vectors engage pattern recognition receptors such as Toll-like receptor (TLR)2 and TLR9 [7][8][9] known to initiate pro-inflammatory responses and to induce expression of co-stimulatory molecules.…”