Tropic determinant for canine parvovirus and feline panleukopenia virus functions through the capsid protein VP2.

Abstract

Canine parvovirus (CPV) can productively infect canine and feline cell lines whereas feline panleukopenia virus (FPV) is restricted to the latter. The major determinants of tropism are two amino acids in the sequence shared by the capsid proteins, VP1 and VP2. We have shown that a rodent parvovirus-derived transducing genome, containing the luciferase reporter, can be packaged by VP1 and VP2 from separate helper sources. Canine A72 cells and feline CFK cells were transduced with recombinant virions generated using VP1 and VP2 combinations from CPV and FPV. Both VP1 and VP2 were necessary for production of transducing virions. Efficient transduction of A72 cells required VP2 of CPV. Therefore, the capsid determinants of tropism for CPV and FPV are in VP2, although a source of VP1 is also necessary to produce infectious particles. The results extend similar observations on the tropic determinants of different strains of minute virus of mice.The feline group of autonomous parvoviruses includes feline panleukopenia virus (FPV) and canine parvovirus (CPV), which have greater than 98 % sequence identity but a distinct host range (Truyen et al., 1992). In cell culture, CPV productively infects both canine and feline cell lines whereas FPV is restricted to feline cells. Studies with CPV-FPV recombinant genomes have shown that the canine host range is determined by the sequence between map units 59 and 73, within the overlapping coding sequence for VP1 and VP2 (Parrish & Carmichael, 1986). Site-directed mutagenesis has implicated amino acids 93 and 323 (numbered from the N terminus of VP2) as the major determinants of host range .We previously described the production of transducing recombinant virions derived from the rodent parvovirus LuIII, Author for correspondence : Ian Maxwell.Fax j1 303 315 8272. e-mail Ian.Maxwell!uchsc.edu with substitution of reporter genes for the viral coding sequences (Maxwell et al., 1993 a). The recombinant genome could be packaged by capsid proteins either from LuIII or from related parvoviruses, including CPV or FPV (Maxwell et al., 1993 b ;Spitzer et al., 1996). In particular, packaging of the recombinant with capsid proteins supplied by a CPV helper, but not by a FPV helper, conferred the ability to transduce canine A72 cells efficiently (Spitzer et al., 1996). By packaging a heterologous genome the results confirmed that the tropic determinants for CPV and FPV were specified by the capsid and direct involvement of the encoding DNA was excluded.The capsids of CPV and FPV are composed of 60 capsomers, which consist of VP1 (" 15 % of the mass of the capsid) and VP2 (Tsao et al., 1991 ; Agbandje et al., 1993). These proteins are translated from alternately spliced transcripts from the P38 promoter. However, since the amino acid residues that determine tropism are present in both VP1 and VP2, this function might be mediated by either protein.Knowledge of which protein is involved would help to clarify their roles in establishing infection. Here, we have investigated this question using th...

Distinct genotypes of a nonenveloped DNA virus associated with posttransfusion non-A to G hepatitis (TT virus) in plasma and peripheral blood mononuclear cells

“…This finding invites a possibility of different organ tropisms for particular TTV variants, as has been shown with parvoviruses [Maxwell et al, 1995;Spitzer et al, 1997;Ueno et al, 1997], as well as HCV [Shimizu et al, 1997;Navas et al, 1998] and human immunodeficiency virus (HIV) [Epstein et al, 1991]. In all these studies, however, a tropism for different tissues was ascribed to only one or a few amino acid changes in the env (capsid for unenveloped viruses) or pol protein, or both.…”

Expansion of tropism of a feline parvovirus to target a human tumor cell line by display of an αv integrin binding peptide on the capsid

“…21,22 We used an expression plasmid encoding VP1 and VP2 of FPV to generate modified capsids with peptide insertions at the extremity of loop 2 on the virion surface. 5 To facilitate characterization of the resulting viruses, the modified capsid proteins were used to package a recombinant parvovirus genome expressing a luciferase reporter gene, [21][22][23] as shown in Figure 1. In this way, virion production could be assayed using PCR to detect the packaged recombinant genome and successful infection (transduction) of target cells could be determined by luciferase expression.…”

“…23,28 However, in our recombinant system these proteins can be supplied from separate expression plasmids, 23,29 enabling these proteins to be independently modified by peptide insertion. We generated recombinant virions with C4-RGD separately inserted into VP1 or VP2 at the same SpeI site in their shared coding sequence, with the other protein retaining the wild-type sequence.…”

“…28,39 Plasmids pF.VP1 and pF.VP2, expressing either VP1 or VP2 alone, have also been described. 23 For most experiments, virions were produced containing the GLuP38LUC2 LuIIIluciferase genome (see Figure 1), by cotransfection of capsid protein expression plasmids with pGLuP38LUC2 21 which expresses LuIII non-structural (NS) proteins. For some experiments, virions were produced containing the alternative GLuP4LUC1 genome 22,40 by supplying NS helper functions from the additionally cotransfected plasmid, pRSVhel.…”

“…Virus production was as described 21,22 using electroporation to cotransfect the 324K cell line (or, in some experiments, COS cells) with a plasmid containing a LuIIIluciferase recombinant genome and one or more plasmids encoding wild-type or modified FPV capsid proteins. Virus with the peptide insert in either VP1 or VP2 (Figure 7) was obtained by cotransfection with combinations of pF-VP1 or pF-VP2 23 with their derivative plasmids containing the C4-RGD insert. Virus stocks, consisting of combined culture medium and freezethawed extracts of the electroporated producer cells were stored at 4°C.…”