RT Journal Article SR Electronic(1) A1 Strand, M. R.YR 1994 T1 Microplitis Demolitor Polydnavirus Infects and Expresses in Specific Morphotypes of Pseudoplusia Includens Haemocytes JF Journal of General Virology, VO 75 IS 11 SP 3007 OP 3020 DO https://doi.org/10.1099/0022-1317-75-11-3007 PB Microbiology Society, SN 1465-2099, AB Microplitis demolitor is a polydnavirus-carrying wasp that parasitizes the larval stage of Pseudoplusia includens. M. demolitor eggs are never encapsulated by host hae- mocytes when coinfected with its associated polydnavirus (MdPDV) whereas eggs are encapsulated within 36 h when injected into hosts without virus. In this study, infection of specific classes of P. includens haemocytes by MdPDY was examined. Electron microscopic studies indicated that MdPDV entered all haemocyte morphotypes. Northern blot analysis revealed that similar size classes of viral mRNAs were produced in granular cells, plasmatocytes and spherule cells. Expression of a 1ยท6 kb MdPDV mRNA in haemocytes from parasitized hosts was detectable by in situ hybridization at 2 h post-parasitism (p.p.) and continued through until day 6 p.p. By 12 h p.p., viral expression was detected in greater than 80% of the haemocytes in circulation but thereafter the percentage of haemocytes exhibiting a hybridization signal declined. Similar patterns were observed in haemocytes from larvae injected with calyx fluid or MdPDV plus venom. Granular cells and plasmatocytes from unparasitized larvae were purified on Percoll cushions and maintained in vitro. Both morphotypes were successfully infected with MdPDV and exhibited changes in morphology and adhesiveness very similar to cells from parasitized hosts. Cell-free plasma from parasitized larvae had a variable effect on haemocyte adhesion. Haemocytes cultured in plasma from 1 or 4 day p.p. larvae rapidly spread whereas cells cultured in 7 day p.p. plasma did not. Reciprocally, adhesion of haemocytes from parasitized larvae could not be rescued by cell-free plasma from unparasitized larvae. Together, these data suggest that disruption of the host encapsulation response is mediated primarily by direct infection of granular cells and plasmatocytes by MdPDV., UL https://www.microbiologyresearch.org/content/journal/jgv/10.1099/0022-1317-75-11-3007