This study was carried out to evaluate the antitumor effect of live attenuated measles virus Schwarz (MV) vaccine strain on tumor cell lines in vitro. Live attenuated measles virus Schwarz vaccine strain was obtained from Aventis Pasteur, France. It was propagated on Vero, human Rhabdomyosarcoma (RD) and human Glioblastoma-Multiform (GBM) cell lines which were supplied by Iraqi Center for Cancer and Medical Genetic Researches (ICCMGR). Results revealed that cell fusion was occurred after 24 h of infection. The infected confluent monolayer appeared to be covered with syncytia with granulation and vaculation of cells after 72 to 120 h of infection. Moreover, the formation of large round empty plaque spaces was observed in infected cells. Results showed that after 72 h of exposure, alterations in morphology of Vero, RD and GBM cells were observed. Cells were rounded, shrinkage, clustered cells and large empty space with cell debris as a result of cell lysis and death. Haemadsorption effect of MV was studied and result recorded that all cell lines infected with virus have the ability for haemadsorption to human red blood cells after 72 h of infection. Detection of MV H protein by monoclonal antibodies in infected cells of all cell lines by immunocytochemistry assay gave positive results in cytoplasm of infected cells. Assessment of the MV antitumor effect on RD and GBM cell lines was carried out by using different dilutions of virus starting from 1:2 to 1:64 for 2 h at 37 0C. Cell viability was measured after 72 and 120 h of infection by MTT assay. Results showed a significant cytotoxic effect for measles virus (P ≤0.05) on growth of RD and GBM cell lines at the dilution 1:2 and the 1:4 dilutions after 72 and 120 h of infection. When the dilution increases, there was a significant decline in the inhibitory effect with a significant cytotoxic effect as compared with the control. Also concentrated inoculums of measles virus showed a significant cytotoxic effect when compared with the control. Induction of apoptosis by MV virus was assessed by measuring mitochondrial membrane potentials in RD and GMB after 48, 72 and 120h of infection by Mitocapture kit. Healthy cells gave a bright red fluorescent light. Apoptotic cells gave green fluorescent light. Apoptotic cells were counted and the mean percentage of dead cells was significantly higher (87.42, 93.69 and 97.36 Vs. 20.83) % after 48, 72 and 120 h of infection for RD when compared with control. A significant difference was recorded in the percentage of dead cells in GBM after 48, 72 and 120 h in comparison with control (89.62, 95.43 and 97.97 Vs. 20.83). Also results were analyzed by imageJ program and results exhibited that MV induce apoptosis in RD and GBM cell lines.
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