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 (6-10).