PRPS1 and infection: Through forward genetic screening, we found that the pals-22 gene represses a set of immunity-related genes called the Intracellular Pathogen Response (IPR) genes, which are activated upon infection by natural intracellular pathogens of the C. elegans intestine–the Orsay virus and the fungus Nematocida parisii from the microsporidia phylum [11–15].