Canine
transmissible venereal tumor (CTVT) is a naturally occurring
tumor that can be transmitted between dogs via live
tumor cell inoculation. It is also a spontaneous self-regression
tumor and its behavior is closely related to host immune responses. Since CTVT had been widely used for
tumor models in canine
cancers, whether this self-regression may overtake the immunity elicited from an exogenous
tumor vaccine remains unclear and certainly worthwhile to be investigated. In this study, we used DCs/
tumor hybrids as a
tumor vaccine to evaluate the CTVT model. We prepared mature allogeneic dendritic cells from bone marrow and then assessed their phenotype (CD80, CD83, CD86, CD1a, CD11c, CD40 and MHC II),
antigen uptake and presenting abilities. Fused dendritic cell/CTVT hybrids were then used as a
vaccine, administered three times at two-week intervals via
subcutaneous injection near the bilateral auxiliary and inguinal lymph nodes. In comparison with unvaccinated dogs (spontaneous regressed group), within a period of 2.5 months, the vaccinations substantially inhibited
tumor progression (p<0.05) and accelerated the rate of regression by a mechanism involving amplification of the host
tumor-specific adaptive immune responses and NK cytotoxicity (p<0.001). Pathologic examination revealed early massive lymphocyte infiltration resulting in final
tumor necrosis. In addition, there are not any detectable effects on routine physical, body temperature or blood chemistry examinations. In conclusion, our data furnishes a reference value showing that CTVT is a model of potential use for the study of immunity elicited by
vaccines against
tumors, and also enable early-phase evaluation of the dendritic cell/
tumor vaccine in terms of raising host immunity.