Arch Virol (2003) 148: 1507–1521
Virulence of Infectious hematopoietic necrosis virus and Infectious
pancreatic necrosis virus coinfection in rainbow trout
(Oncorhynchus mykiss) and nucleotide sequence analysis
of the IHNV glycoprotein gene
, S. Rodr´ıguez Saint-Jean
, and S. I. P´erez-Prieto
Department of Microbiology, Oregon State University, Corvallis, Oregon, U.S.A.
Departamento de Microbiolog´ıa Molecular, Centro de Investigaciones
Biol´ogicas (CSIC), Madrid, Spain
Received November 6, 2002; accepted March 3, 2003
Published online June 2, 2003
Summary. The outcomes of a coinfection of rainbow trout (Oncorhynchus mykiss)
with Infectious hematopoietic necrosis virus (IHNV) strain S46 and Infectious
pancreatic necrosis virus (IPNV) strain S46 was determined after waterborne
infection. Trout infected with the IHNV/IPNV.S46 sample, (a mixed sample
containing equal infectious titers of the viruses) showed 50% less mortality than
ﬁsh infected with either of the reference viruses alone. Forty-ﬁve days after the
coinfection, IPNV antigens were detected by ﬂow cytometry in 49 to 63% of
the leukocytes from the surviving trout; whereas, only 9–15.6% of the leukocytes
expressed IHNV viral antigens. IPNV was easily detected by reverse transcription-
polymerase chain reaction (RT-PCR), whereas, for IHNV, a second step of am-
pliﬁcation of a 753 bp fragment corresponding to the internal sequences of the
IHNV G gene was necessary to optimize viral detection. The sequence of the
IHNV gene involved in virulence, the glycoprotein (G) gene, was determined
for the IHNV.S46 and compared with other sequences available in the GenBank.
Changes found were not located in the antigenic domains of the glycoprotein and
were considered not signiﬁcant.
Infectious hematopoietic necrosis virus (IHNV) and Infectious pancreatic necrosis
virus (IPNV) are important pathogens in global freshwater aquaculture. To control
the infections caused by these viral agents, pathogen-free certiﬁcation is required
in many countries before eggs or ﬁsh are removed or introduced in a new facility.