✓ IROGENETICS 
NYVAC (vP866) INFORMATION 
A. ORIGIN OF THE NYVAC (vP866) VECTOR 
1. Parental organism: A plaque-cloned isolate of the Copenhagen vaccinia 
vaccine strain (VC-2) was used as the parent virus in the derivation of 
NYVAC (vP866). The complete DNA sequence of the VC-2 isolate is known 
and described in Appendix A. 
2. Description of the NYVAC vector: The highly attenuated vaccinia virus 
strain, NYVAC (vP866) was derived from a plaque-cloned isolate of the 
Copenhagen vaccine strain by the precise deletion of 18 open reading frames 
(ORFs) from the viral genome. Among the ORFs deleted from NYVAC 
(vP866) are two genes involved in nucleotide metabolism, the thymidine kinase 
(ORF J2R) and the large subunit of the ribonucleotide reductase (ORF I4L); 
the gene encoding the viral hemagglutinin (ORF A56R); the remnant (ORF 
A26L) of a highly expressed gene responsible for the formation of A-type 
inclusion bodies; the disrupted gene (ORFs B13R/B14R) normally encoding a 
serine protease inhibitor; and a block of twelve ORFs bounded by two known 
viral host range regulatory functions (ORFs C7L through K1L). Within this 
block a secretory protein (ORF NIL) implicated in viral virulence and a 
functional complement 4b binding protein (ORF C3L) are encoded. The ORFs 
were deleted in a manner which prevents the synthesis of undesirable novel 
gene products (Appendix B). The net result of these deletions is a highly 
attenuated vaccinia virus which nonetheless retains the capacity to evoke strong 
immune responses to foreign immunogens (Appendix C). 
B. BIOLOGICAL PROPERTIES 
1. Host/range specificity: Both the C7L and K1L host range genes are deleted 
from NYVAC (vP866), making it deficient for replication on human cell lines 
(Appendices B and D), as well as cells derived from a number of other species 
(Appendix E). In a study comparing the replicative ability of three vaccinia 
strains in mouse ovaries, the WR (L-variant) and VC-2 (Copenhagen) strains 
disseminated to and accumulated in various organs, while the NYVAC (vP866) 
strain cleared rapidly and did not disseminate (Appendix F). 
2. Virulence: In an IC challenge of newborn mice, NYVAC (vP866) had an 
LD 50 value of 1.58 x 10 6 pfu; in 3-week-old mice the LD 50 was 1.58 x 10 8 pfu. 
IP inoculation of high doses of NYVAC (5 x 10 8 pfu) into nude mice caused 
no deaths, no lesions, and no apparent disease over a 100-day observation 
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Recombinant DNA Research, Volume 18 
