Cancer-induced expansion and activation of CD11b⁺ Gr-1⁺ cells predispose mice to adenoviral-triggered anaphylactoid-type reactions

Intravascular delivery (1.5 × 10⁹ particles and higher) of recombinant adenovirus (rAd) induces myeloid cell mediated, self-limiting hemodynamic responses in normal mice. However, we observed anaphylactoid-type reactions and exacerbated hemodynamic events following rAd injection in mice bearing malignant 4T1 mammary carcinoma. Because 4T1 tumors induce significant CD11b⁺Gr-1⁺ myeloid cell expansion and activation, we set to determine whether this causes rAd-induced exaggerated responses. When treated with a single intravenous dose (1 × 10¹⁰ particles) of rAd, mice implanted with 4T1 carcinoma succumbed due to the anaphylactoid-type reactions. In contrast, normal mice and mice implanted with a related mammary carcinoma (66cl4) that does not induce CD11b⁺ Gr-1⁺ cell expansion, showed minimal responses. Depletion of phagocytic CD11b⁺Gr-1⁺ cells prior to rAd delivery protected 4T1 tumor-bearing animals, whereas passive transfer of CD11b⁺Gr-1⁺ cells from 4T1 tumor-bearing animals was sufficient to convey susceptibility to anaphylactoid-type reactions in normal animals. We further show that there is upregulation of nitric oxide and leukotriene signaling pathways in the 4T1 tumor-induced CD11b⁺Gr-1⁺ myeloid cells and that pretreating mice with inhibitors of nitric oxide synthetase and leukotrienes can attenuate the anaphylactoid-type reactions. These data show that malignant tumor growth can alter CD11b⁺Gr-1⁺ myeloid cells, rendering hosts susceptible to anaphylactoid-type reactions upon intravascular treatment with rAd.