Arch Virol (2000) 145: 1149–1161
Mutations in the genome of porcine reproductive and respiratory
syndrome virus responsible for the attenuation phenotype
, G. F. Kutish
, W. Laegreid
, T. L. Lewis
, D. L. Rock
, J. A. Galeota
, A. R. Doster
, and F. A. Osorio
Department of Veterinary and Biomedical Sciences, University of Nebraska-Lincoln,
Lincoln, Nebraska, U.S.A.
Plum Island Animal Disease Center, USDA/ARS, Greenport, New York, U.S.A.
U.S. Meat Animal Research Center, USDA/ARS, Clay Center, Nebraska, U.S.A.
Accepted December 16, 1999
Summary. Although live-attenuated vaccines have been used for some time to
control clinical symptoms of the porcine reproductive and respiratory syndrome
(PRRS), the molecular bases for the attenuated phenotype remain unclear. We
had previously determined the genomic sequence of the pathogenic PRRSV
16244B. Limited comparisons of the structural protein coding sequence of an
attenuated vaccine strain have shown 98% homology to the pathogenic 16244B.
Here we have conﬁrmed the attenuated phenotype and determined the genomic
sequence of that attenuated PRRSV vaccine and compared it to its parental VR-
2332 and the 16244B strains. The attenuated vaccine sequence was colinear
with that of the strain 16244B sequence containing no gaps and 212 substitu-
tions over 15,374 determined nucleotide sequence. We identiﬁed nine amino acid
changes distributed in Nsp1␤, Nsp2, Nsp10, ORF2, ORF3, ORF5 and ORF6.
These changes may provide the molecular bases for the observed attenuated
Porcine reproductive and respiratory syndrome (PRRS), is a devastating viral
disease characterized by reproductive failure in sows, pre-weaning mortality and
respiratory illness in piglets [1, 24]. The causative agent, PRRSV , belongs
to the Arteriviridae family together with lactate dehydrogenase-elevating virus
The GenBank accession number for the PRRSV modiﬁed live vaccine (complete
genome) reported in this paper is AF159149.