Exchanging the yellow fever virus envelope proteins with Modoc virus prM and E proteins results in a chimeric virus that is neuroinvasive in SCID mice.
A chimeric flavivirus infectious cDNA was constructed by exchanging the premembrane (prM) and envelope (E) genes of the yellow fever virus vaccine strain 17D (YF17D) with the corresponding genes of Modoc virus (MOD). This latter virus belongs to the cluster of the "not-known vector" flaviviruses and is, unlike YF17D, neuroinvasive in SCID mice. Replication of in vitro-transcribed RNA from this chimeric flavivirus was shown by [(3)H]uridine labeling and RNA analysis. Expression of the MOD prM and E proteins was monitored by radioimmunoprecipitation and revealed that the MOD proteins were correctly and efficiently produced from the chimeric precursor protein. The MOD E protein was shown to be N-linked glycosylated, whereas prM, as predicted from the genome sequence, did not contain N-linked carbohydrates. In Vero cells, the chimeric virus replicated with a similar efficiency as the parental viruses, although it formed smaller plaques than YF17D and MOD. In SCID mice that had been infected intraperitoneally with the chimeric virus, the viral load increased steadily until death. The MOD/YF virus, like MOD from which it had acquired the prM and E structural proteins, but unlike YF, proved neuroinvasive in SCID mice. Animals developed neurological symptoms about 15 days after inoculation and died shortly thereafter. The distribution of MOD/YF RNA in the brain of infected mice was similar to that observed in MOD-infected mice. The observations provide compelling evidence that the determinants of neuroinvasiveness of flaviviruses are entirely located in the envelope proteins prM and E.
Charlier
Nathalie
N
Rega Institute for Medical Research, Minderbroedersstraat 10, B-3000 Leuven, Belgium. johan.neyts@rega.kuleuven.ac.be
Molenkamp
Richard
R
Leyssen
Pieter
P
Paeshuyse
Jan
J
Drosten
Christian
C
Panning
Marcus
M
De Clercq
Erik
E
Bredenbeek
Peter J
PJ
Neyts
Johan
J
D000595:Amino Acid Sequence; D000818:Animals; D002522:Chlorocebus aethiops; D006224:Cricetinae; D018792:Encephalitis, Viral / Q000401:mortality* / Q000821:virology; D005416:Flavivirus / Q000235:genetics* / Q000378:metabolism; D051379:Mice; D016513:Mice, SCID; D008969:Molecular Sequence Data; D011995:Recombination, Genetic; D014709:Vero Cells; D014759:Viral Envelope Proteins / Q000235:genetics* / Q000378:metabolism; D015005:Yellow fever virus / Q000235:genetics / Q000378:metabolism / Q000472:pathogenicity*
D014759:Viral Envelope Proteins; C074932:prM protein, Flavivirus; C078400:yellow fever virus envelope protein E