The infectivity of progeny adenovirus in the presence of neutralizing antibody.

Human adenoviruses (Ads), common pathogens that cause upper respiratory and gastrointestinal infections, are blocked by neutralizing antibodies (nAbs). However, Ads are not fully eliminated even in hosts with nAbs. In this study, we assessed the infectivity of progeny Ad serotype 5 (Ad5) in the presence of nAb. The infectivity of Ad5 was evaluated according to the expression of the Ad genome and reporter gene. Infection by wild-type Ad5 and Ad5 vector continued to increase until 3 days after infection even in the presence of nAb. We established an assay for determining the infection levels of progeny Ad5 using a sorting system with magnetic beads and observed little difference in progeny Ad5 counts in the presence and absence of nAb 1 day after infection. Moreover, progeny Ad5 in the presence of nAb more effectively infected coxsackievirus and adenovirus receptor (CAR)-positive cells than CAR-negative cells. We investigated the function of fiber proteins, which are the binding partners of CAR, during secondary infection, observing that fibre proteins spread from infected cells to adjacent cells in a CAR-dependent manner. In conclusion, this study revealed that progeny Ad5 could infect cells even in the presence of nAb, differing from the common features of the Ad5 infection cycle. Our findings may be useful for developing new therapeutic agents against Ad infection.

Development of Dendritic Cell-Based Immunotherapy Targeting Tumor Blood Vessels in a Mouse Model of Lung Metastasis.

Tumor blood vessels supply cancer tissues with oxygen and nutrients, and it was therefore believed that inhibition of angiogenesis would induce tumor regression. In fact, the situation is complicated by the presence of normal blood vessels in cancer tissues such as carcinomas and sarcomas as well as abnormal vessels. Here, we describe the development of a dendritic cell (DC)-based immunotherapy which targets tumor endothelial cells (TECs) rather than normal endothelial cells (ECs) or cancer cells themselves. After density gradient centrifugation, the TEC-rich fraction from lungs invaded by B16 melanoma cells was separated from the endothelial cell (EC)-rich fraction on the basis of positivity for angiotensin-converting enzyme (ACE) activity. Prophylactic vaccination with DCs pulsed with lysates of TECs isolated from lungs with metastases significantly suppressed lung metastasis in this B16/BL6 mouse melanoma model. This suggests that DC-based vaccine therapy targeting TECs in cancers tissue could show promise as an effective therapy for distant metastasis.

Cancer Vaccine Therapy Using Tumor Endothelial Cells as Antigens Suppresses Solid Tumor Growth and Metastasis.

Tumor angiogenesis plays an important role in tumor growth and metastasis, with tumor cells requiring nutrients and oxygen via blood flow for their proliferation. In comparison, angiogenesis also occurs under normal physiological conditions, such as wound healing and in the formation of the corpus luteum. Herein, we report on the development of a novel dendritic cell (DC) vaccine therapy using tumor endothelial cells (TECs) derived from tumor vessels as tumor antigens. After density gradient centrifugation and the detection of angiotensin-converting enzyme activities, a TEC-rich fraction was separated from solid tumor tissues. Prophylactic or therapeutic immunization using DCs pulsed with TECs as vaccine antigens significantly suppressed solid tumor growth in a Colon-26 colorectal adenocarcinoma tumor-bearing mouse model, compared with the use of tumor cells as DC vaccine antigens. Tumor tissues showed reduced angiogenesis. However, vaccination using DCs pulsed with TECs did not inhibit physiological angiogenesis as evidenced by a wound healing assay. Additionally, in a B16/BL6 mouse melanoma lung metastasis model, DC vaccination using TECs derived not only from the same tumor tissue but from a different type of tumor also suppressed metastasis. These results thus show that cancer vaccine therapy targeting TECs is an effective therapy against angiogenesis in several types of cancer, but does not affect normal blood vessel growth.