srjalsSRJALSSRJALS2788-9386https://doi.org/10.47310/srjals.2025.v05i02.009Determination of the Factors that Define the Tropism of Astroviruses in Established Cell LinesMarwahAli OudahSuhad AbdulhusseinSalmanShahad AhmedBakheetAlfurat Alawsat Technical University, Polytechnic College Alqadisyah, IraqAstroviruses that infect humans are an important cause of gastroenteritis in children. They are classified into 8 classic serotypes named 1 to 8 and some new genotypes that genetically resemble animal viruses more than human viruses. The genome of astroviruses consists of a single strand of RNA of positive polarity; they are non-enveloped viruses, and the viral particle is formed by the viral genome surrounded by a 35 nm icosahedral protein capsid. Different serotypes infect different cell lines with additional efficiency. Susceptibility or resistance to infection may be determined at various levels of the replication cycle, such as attachment to the cell, viral particle internalisation, viral RNA release (uncoating), RNA translation, and genome replication, the assembly and exit of the viral particles to the outside of the cell. In accordance with previous evidence, this work aimed to determine which step or steps of the astrovirus replication cycle determine tropism in different cell lines. It was found that in a population of cells from the Caco-2 cell line infected with astrovirus serotype 8, 95% of the cells in the monolayer can be infected. By cloning subpopulations, we discovered MA104 cell clones with up to ten times lower susceptibility than the parental cell line. Each cell infected with serotypes 1 and 8 produced 143 and 328 infectious viral particles, respectively, in the Caco-2 cell line, while the MA104 cell line produced 34 and 24. The findings of this study suggest that astrovirus tropism is restricted for the MA104 and MDCKII cell lines during entry and in some phases after the release of the viral RNA to the cytosol.