Microplitis demolitor bracovirus blocks plasmatocyte response to PSP

The noctuid moth Chrysodeixis includens defends itself against large invaders such as parasitoid wasps by encapsulating them with hemocytes. An important step in capsule formation is the processing of a 20 kD precursor protein to produce the cytokine Plasmatocyte Spreading Peptide (PSP).  PSP then activates capsule-forming hemocytes called plasmatocytes.  Prior studies establish that the braconid wasp Microplitis demolitor disables capsule formation by infecting C. includens with M. demolitor bracovirus (MdBV).  Here we report that MdBV does not alter PSP processing but it does interfere with signaling and adhesion responses in plasmatocytes that are stimulated by PSP.