genetic modification method viral transduction method This refers to the infection of cells with either a pathogenic or a modified virus, which introduces viral genome into the cells. Pathogenic viruses include the influenza virus, measles virus, Japanese encephalitis virus, etc. For recombinant expression of proteins in cells or tissues, several types of viruses are utilized, including lentivirus, retrovirus, adenovirus, etc, with each having their own advantages and disadvantages.