Abstract
Virus‐like particles (VLPs) have increasingly attracted attention as DNA‐free and safe antigen carriers in tumor immunotherapy, requiring only minute amounts of antigens. Previously, we have immunized with murine polyomavirus (MPyV) VLPs carrying human Her2/neu and prevented the outgrowth of a human Her2/neu expressing tumor in a transplantable tumor model as well as outgrowth of spontaneous rat Her2/neu carcinomas in BALB‐neuT mice. Here, we examine if prophylactic and therapeutic protection could be obtained with murine pneumotropic virus (MPtV) VLPs, and study the cross‐reactivity between human and rat Her2/neu. VLPs from MPyV and MPtV carrying human or rat Her2/neu were tested in two transplantable tumor models against a human Her2/neu positive (D2F2/E2) and a rat Her2/neu positive tumor cell line (TUBO). Rat Her2/neu‐VLPs were also tested in BALB‐neuT mice. Her2/neu‐MPtVLPs were as efficient as prophylactic vaccines against D2F2/E2 and TUBO as those from MPyV. Homologous Her2/neu was better than heterologous, i.e. human Her2/neu‐VLPs were better than rat Her2/neu‐VLPs against D2F2/E2 and vice versa. Moreover, therapeutic immunization with human Her2/neu‐VLPs together with CpG given up to 6 days after challenge protected against D2F2/E2. In BALB‐neuT mice, rat Her2/neu‐VLPs were less efficient than human Her2/neu‐VLPs used in our previous study, implying that protection seen in that study was partly due to the use of human rather than rat Her2/neu. In conclusion, Her2/neu‐MPtVLPs are effective both as prophylactic and therapeutic tumor vaccines. Homologous Her2/neu‐VLPs are superior to heterologous in transplantable tumor models, while the opposite is true in BALB‐neuT mice. © 2008 Wiley‐Liss, Inc.