1 ABSTRACT The success of cancer vaccines depends on factors associated with the vaccine, which define the main parameters of effective immune responses such as its size and quality, as well as on factors related with the host, represented by the immunosuppressive mechanisms that allow the tumor to escape recognition by the immune system or negatively influence the function of effector T-cells. Attenuated, non-replicating viruses are at present preferred as VACV for safety reasons. A problem may arise concerning their lack of immunogenicity. Through the deletions of non-essential genes, vaccination vectors are therefore developed based on attenuated rVACV capable of replication, which induce a strong immune response. Genes of various immunological adjuvants (e.g., genes for cytokines and costimulatory molecules) are inserted into the vectors for the purpose of eliminating the influence of the immunosuppressive mechanisms of tumors. The first part of the work describes our study of the influence of vCCI on biological properties of rVACV derived from the Prague strain. Testing of vCCI deletion and insertion mutants expressing tumor associated protein HPV16 E7 has shown that secreted vCCI attenuated the virus in vivo, which correlated with reduced levels of the corresponding CC chemokines in the blood compared...