Development of Indirect Immunofluorescence Technique for the Identification of MRC5 Working Seed Cell

Diploid and continuous cell lines are used to propagate viral vaccines. At Human Viral Vaccine Department of Razi Vaccine and Serum Research Institute, MRC5 diploid cell is used for the development of live attenuated measles, mumps, rubella, and three types of poliovirus vaccines.  Additionally, three continuous cell lines (i.e., RK13, HeLa, and Vero) are applied in quality control tests. Accordingly, cell cross-contamination can occur at cell culture labs, hence controlling the identity and specificity of cells is essential. Indirect immunofluorescence is a sensitive, specific, and simple test for cell identification. The present study was designed to develop the in-house indirect immunofluorescence test (IIF) as follows: homemade polyclonal anti-MRC5 serum was prepared in rabbits, and cross-reactive antibodies to RK13, HeLa, and Vero cells were eliminated. The diploid and continuous cell lines were fixed on Teflon slide using cold methanol and acetone. The reproducibility of the in-house IIF test was evaluated using the agreement Kappa test.  The purity of the three batches of MRC5 working seed cell at Human Viral Vaccine Department of Razi institute was verified using IIF and no contamination with continuous cell lines was detected.