Adenovirus vector-mediated gene transfer to regional lymph nodes

Regional lymph nodes (RLNs) possess important immune functions and represen t a major pathway of metastasis for solid tumors. Given these facts, the ab ility to transfer exogenous genes to the RLNs with the goal of manipulating the local immunological milieu would be desirable. On the basis of the hyp othesis that a significant proportion of adenovirus (Ad) gene transfer vect ors traffic through the lymphatics, E1(-)E3(-) Ad vectors were injected int o the hind footpad of C3H/He mice and the RLNs assessed for vector traffick ing and transgene expression. A low dose (10(9) particles) of an Ad vector encoding the firefly luciferase gene (AdCMV.Luc) resulted in luciferase exp ression only in the injection site and RLNs, with no detectable systemic (l iver, spleen, lung) expression. At a higher dose (10(11) particles), some e xpression could be detected systemically in addition to the RLNs, but at le vels in liver 14-fold less than in the RLNs. Transgene expression in the RL Ns was transient, peaking at 1 day, decreasing markedly by 7 days. At high doses (10(11) particles), interruption of draining lymphatics decreased the amount of systemic dissemination 22-fold, suggesting that a large proporti on of the vector trafficks through the lymphatics before reaching the syste mic circulation. Administration of a vector encoding the jellyfish green fl uorescent protein gene (AdCMV.GFP, 10(11) particles) showed that transgene expression in the RLNs was primarily in the cortical area. After footpad in jection of a fluorescent-labeled Ad vector (Cy3-AdCMV.Null), fluorescent vi rions were visualized in the draining lymph. Regional lymph collected from animals injected in the footpad with AdCMV.Luc (10(11) particles) contained functional vector. Augmentation of local immune function in the RLNs was a chieved by footpad administration of an Ad vector encoding murine IL-12, re sulting in high mIL-12 and IFN-gamma levels in the regional, but not distan t, nodes. These data demonstrate that expression of exogenous genes in RLNs is easily accomplished with Ad vectors, Ad vector dissemination occurs pri marily via the lymphatics after footpad administration in mice, and basic i mmune functions in the RLNs can be manipulated by Ad-mediated gene transfer in vivo.