Sánchez-Sampedro L, Gómez CE, Mejías-Pérez E, Pérez-Jiménez E, Oliveros JC, Esteban M.
Replication competent poxvirus vectors with an attenuation phenotype and with high immunogenic capacity of the foreign expressed antigen are being pursuit as novel vaccine vectors against different pathogens. In this investigation we have examined the replication and immunogenic characteristics of two vaccinia virus (VACV) mutants M65 and M101.
These mutants were generated after 65 and 101 serial passages of persistently infected Friend erythroleukemia cells (FEL). In cultured cells of different origins the mutants are replication competent and have growth kinetics similar or slightly reduced in comparison with the parental Western Reserve (WR) virus strain. In normal and immune suppressed infected mice the mutants showed different attenuation levels, and pathogenicity in comparison with WR and MVA strains. Wide genome analysis after deep sequencing revealed selected genomic deletions and mutations in a number of viral open-reading frames (ORFs). Mice immunized in DNA prime/Mutant boost regime with viral vectors expressing the LACK antigen of Leismania infantum resulted in protection or delay in the onset of cutaneus leishmaniasis. Protection was similar to that triggered by MVA-LACK. In immunized mice, both polyfunctional CD4+ and CD8+ T cells with an effector memory phenotype were activated by the two mutants, but DNA-LACK/M65-LACK protocol preferentially induced CD4+ while DNA-LACK/M101-LACK preferentially induced CD8+ T cell responses.
Altogether our findings showed the adaptive changes of the WR genome during long-term virus-host cell interaction and how replication competency of M65 and M101 mutants confers distinct biological properties and immunogenicity in mice, as compared to the MVA strain. These mutants could have applicability for understanding VACV biology and as potential vaccine vectors against pathogens and tumors.