Cellular distribution of the receptors differs with the type I receptor generally expressed Y-27632 concentration by hematopoietic cells and type II by non-hematopoietic cells due to differing expression of the γc and IL-13Rα1 subunits, while macrophages express both type I and II receptors. Engagement of IL-4/IL-13 to the receptors triggers cell signalling via JAK/STAT6 dependent mechanisms [25]. A second receptor, IL-13Rα2, binds IL-13 with high affinity and is thought to be a decoy receptor sequestering IL-13 [24], although some studies suggest an uncharacterised signalling activity [26]. Previously, Ahlers et al. [27] demonstrated that soluble IL-13Rα2-Fc decoy

receptor together with GM-CSF and CD40L as molecular adjuvants can enhance magnitude HIV Env-specific CD8+ CTL peptide vaccine response. However, IL-13Rα2-Fc protein used alone without other co-stimulators failed MEK inhibitor to enhance CTL magnitude or activity. Consistent with this finding we have also found that, a single administration of soluble IL-13Rα2-Fc protein together with FPV-HIV made no difference

in HIV-specific CD8+ T cell numbers or T cell avidity [23]. In contrast, HIV vaccines co-expressing IL-13Rα2 decoy receptor was able to sequester free IL-13 and greatly enhance magnitude, functional avidity and poly-functionality of the HIV Gag-specific CD8+ T cell response [23]. A number of IL-4 derivatives that either mutate or delete the essential tyrosine residue found in the C-terminal region of both human and mouse cytokines have been developed which bind to cellular IL-4Rα with high

affinity without stimulating cell signalling and block activation 5-Fluoracil by both endogenous IL-4 and IL-13 [28], [29], [30] and [31]. To avoid introducing novel viral expressed “IL-4 antigens” due to amino acid substitutions we have constructed recombinant FPV and VV co-expressing a soluble mouse IL-4 protein containing a short C-terminal deletion encompassing the essential Y119, IL-4C118, while retaining high affinity binding to both IL-4R types I and II and blocking IL-4/IL-13 cell signalling (see Suppl. Diagram 1). In this study we have evaluated the efficacy of this novel IL-4R antagonist HIV vaccine, specifically the ability to not only induce high avidity CD8+ T cells but also B cell immunity. In this study the HIV-specific T cell responses were evaluated against the BALB/c Gag197–205 AMQMLKETI immune-dominant CD8 T cell epitope [32]. As we have previously shown that CD8+ T cells specific for the immuno-dominant epitope represent approximately 80% of the total Gag response in an FPV-HIV/VV-HIV immunisation setting [33]. The B cell responses were measured against the total HIV P55 Gag protein. The mouse IL-4C118 cDNA was isolated using the reverse transcriptase polymerase chain reaction (RT-PCR) method and the Qiagen RT-PCR kit to amplify the cDNA from mouse spleen total RNA.