Background: A combination of strategies aimed both at destroying tumor cells and at inducing an immune response against them by the activation of the innate and adaptive immunity, in particular oncolytic virotherapy, is considered promising for cancer biotherapy. Oncolytic viruses of the Paramyxoviridae family, particularly Newcastle disease virus (NDV), are powerful oncolytic and immunostimulating agents non-pathogenic in humans.
Methods: The study included 19 white outbred male rats receiving NDV vaccine (a single dose of 5000 vaccine doses (1 bottle) paratumorally, twice a week, a total of 4 injections): group 1 – injections were started 1 day after subcutaneous Guerin carcinoma transplantation, group 2 – a week before tumor transplantation. All procedures followed the guidelines of the European Convention for the protection of vertebrate animals used for experimental and other scientific purposes. Subpopulations of lymphocytes were determined in the peripheral blood collected from the femoral vein of animals. Relative numbers of CD3+, CD4+, CD8+, CD25+ and CD45RA+ cells were determined by flow cytometry using monoclonal antibodies BD Pharmingen Rat T/B/NK Cell Cocktail, BD Pharmingen Rat Activated T Lymphocyte, BD Pharmingen Rat T Lymphocyte Cocktail.
Results: Early after its injections, NDV caused a significant increase in the levels of T lymphocytes with the early activation marker, with a decrease in CD3+CD8+ cells. The stimulation of CD3+CD4+ and CD3+CD25+ lymphocytes was registered in animals with the subsequent tumor transplantation, compared to controls.
Conclusions: The results suggested that stimulation of the T-cell component of the immune system of rats by prior NDV injections induced antitumor effect in some animals.