The CrV1 gene of Cotesia rubecula polydnavirus (PDV) suppresses the cellular immune system of Pieris rapae larvae. Although the gene was originally described in C. rubecula, CrV1 gene homologs exist in polydnaviruses of several Cotesia species. A CrV1 homolog gene has been identified in C. congregata PDV. The C. congregata PDV not only suppresses the immune response but it may also be involved in causing hemocyte apoptosis in parasitized Manduca sexta larvae. Although CrV1 is expressed in a transient manner (4-8 hpp) in P. rapae, the CrV1 homolog is continuously expressed (from parasitization to emergence of the parasitoid wasp) in M. sexta hosts of Cotesia congregata. This paper reports the cloning,sequencing and expression of the CrV1 gene homolog in C. congregata. The final goal is to develop a hybrid baculovirus containing the immune-suppressive gene of the PDV that can be tested against several important insect pests.This research was jointly funded by CONACYT-UC MEXUS at UC-Riverside and IPN in Reynosa, Mexico