Enhanced polymerase activity confers replication competence of Borna disease virus in mice

Abstract

We previously showed that mouse adaptation of cDNA-derived Borna disease virus (BDV) strain He/80 FR was associated exclusively with mutations in the viral polymerase complex. Interestingly, independent mouse adaptation of non-recombinant He/80 was correlated with different alterations in the polymerase and mutations in the viral glycoprotein. We used reverse genetics to demonstrate that changes in the polymerase which improve enzymatic activity represent the decisive host range mutations. The glycoprotein mutations did not confer replication competence in mice, although they slightly improved viral performance if combined with polymerase mutations. Our findings suggest that the viral polymerase restricts the host range of BDV.Borna disease virus (BDV) is a non-segmented negativestrand RNA virus (Briese et al., 1994) which belongs to the order Mononegavirales (de la Torre, 1994;Schneemann et al., 1995). BDV naturally infects the central nervous system (CNS) of a wide range of mammalian species and is the causative agent of Borna disease (Rott & Becht, 1995), an immune-mediated neurological disorder mainly affecting horses and sheep (Ludwig et al., 1988). Successful experimental infection of a variety of warm-blooded animals has been reported (Rott & Becht, 1995; Staeheli et al., 2000). Nevertheless, most tissue culture-adapted laboratory strains of BDV do not readily infect the CNS of mice, but can be adapted to mice by serial passage. Recently, we successfully adapted molecularly cloned BDV to the mouse and showed that adaptive mutations in the L polymerase (L 1116 R and N 1398 D) as well as in the polymerase cofactor P (R 66 K) contributed to replication competence of BDV in mice (Ackermann et al., 2007). In a previous study, Nishino et al. (2002) identified four different amino acid changes in a derivative of BDV strain He/80, designated CRNP5, that unlike its parent propagates efficiently in the brain of mice. Other amino acid changes originally reported to be present in CRNP5 (Nishino et al., 2002) could not be confirmed if the sequence was compared with those of BDV strain He/80 FR (data not shown). The remaining amino acid changes in CRNP5 affected the viral glycoprotein G (F 458 S and Y 480 H) and the polymerase L (K 1417 R and G 1686 R).To determine the relative contributions of these four mutations, we used reverse genetics technology established by our group (Martin et al., 2006;Schneider et al., 2005).We generated full-length cDNAs carrying either the amino acid substitutions F 458 S and Y 480 H in G, the substitutions K 1417 R and G 1686 R in L or all four substitutions in combination and recovered the corresponding viruses. The resulting recombinant viruses were designated BDV-G SH , BDV-L RR and BDV-G SH /L RR , respectively (Fig. 1). To further analyse the individual contributions of the mutations at amino acid positions 1417 and 1686 in L, we created fulllength cDNAs carrying these mutations individually. The corresponding viruses were recovered and were designated BDV-L 1417 R and BDV-L 1686 ...

Avian Bornavirus Research—A Comprehensive Review

“…Subclinical deficiencies, such as impaired learning and memory functions, have been described for neonatally infected rats even in the absence of clinical signs and inflammatory lesions [ 194 , 195 ]. Host adaptation by multiple passages in experimentally infected hosts has been shown to increase infectivity and pathogenicity of the virus for rats and mice of all age groups [ 172 , 196 , 197 , 198 , 199 ].…”

Epidemiology and host spectrum of Borna disease virus infections

“…In addition to these most abundant proteins, the BDV genome encodes protein p10 (X), matrix protein p16 (M), glycoprotein p57 (G, gp94 when glycosylated) and RNA polymerase (L) (Walker et al, 2000;reviewed by Lipkin & Briese, 2007;Tomonaga et al, 2002). Polymerase activity is important in the adaptation of BDV to new hosts (Ackermann et al, 2007) and the X protein regulates viral polymerase activity and inhibits apoptosis, being essential for host survival (Poenisch et al, 2009). BDV uniquely limits its genome amplification by trimming the genome, which may favour non-cytolytic virus persistence and evasion of the antiviral host response (Habjan et al, 2008;Schneider et al, 2005).…”

Tick-Borne Nyamanini Virus Replicates in the Nucleus and Exhibits Unusual Genome and Matrix Protein Properties

“…Stocks of influenza virus A/PR/8/34 (FLUAV) were generated in MDCKII cells kept in DMEM supplemented with 0.1% bovine serum albumin and 1 g/ml trypsin. Stocks of influenza virus strain WSN were generated in MDCKII cells, and stocks of measles virus (MeV, Edmonston strain), BDV (strain BDV-L RD [1]), vesicular stomatitis virus (VSV), and NYMV (tick isolate 39) were generated in Vero cells.…”