TEP1 and infection: Interestingly, a subsequent RNA-sequencing study involving exposure of D. melanogaster adults with either symbiotic (carrying P. luminescens bacteria) or axenic (lacking P. luminescens) nematodes of H. bacteriophora showed that either type of infection results in consistent downregulation of Tep1 at early and late times after the introduction of the pathogens to the flies, while Tep1 and Tep2 together with Tep4 are highly upregulated by the parasites as well as by injection of P. luminescens bacteria alone throughout the infection [41].