In Vivo Interactions of Ecotropic and Polytropic Murine Leukemia Viruses in Mixed Retrovirus Infections

Profound Amplification of Pathogenic Murine Polytropic Retrovirus Release from Coinfected Cells

“…1A). This observation is consistent with our in vivo results indicating highly elevated polytropic MuLV replication in coinoculated mice (22,33). Similar results were observed when M. dunni cells chronically infected with Fr98 were superinfected with F-MuLV.…”

“…In previous studies, we observed that inoculation of mice with mixtures of the ecotropic virus F-MuLV and the polytropic isolate Fr98 or Fr54 resulted in a profound elevation of the polytropic virus load (22,33). To determine if this occurred in vitro, we compared infectious polytropic viruses released from cell lines infected with only the polytropic virus to polytropic viruses released from cells infected with both the polytropic virus and F-MuLV.…”

“…In this regard, we have described in vivo interactions between ecotropic and recombinant polytropic MuLVs that may facilitate a stepwise process of leukemogenesis in mice infected with Moloney murine leukemia virus (M-MuLV) (29). More recently, we examined the interactions of ecotropic and polytropic MuLVs that were inoculated as virus mixtures into mice (22). Coinoculation of the ecotropic virus Friend murine leukemia virus (F-MuLV) with one polytropic virus (Fr54) greatly extended the survival times of mice compared to those of mice inoculated with F-MuLV alone, while coinoculation of F-MuLV with another polytropic virus (Fr98) induced a rapidly fatal neurological disease that was not observed in infections with either virus by itself (22).…”

“…More recently, we examined the interactions of ecotropic and polytropic MuLVs that were inoculated as virus mixtures into mice (22). Coinoculation of the ecotropic virus Friend murine leukemia virus (F-MuLV) with one polytropic virus (Fr54) greatly extended the survival times of mice compared to those of mice inoculated with F-MuLV alone, while coinoculation of F-MuLV with another polytropic virus (Fr98) induced a rapidly fatal neurological disease that was not observed in infections with either virus by itself (22). In both instances, we observed nearly complete pseudotyping of the polytropic virus RNA genome within ecotropic virions.…”

Absence of infection in pigs inoculated with high-titre recombinant PERV-A/C

“…However, the number of infectious particles (6.4 × 10 6 ) was much higher than what has been used for infection of cats with feline leukaemia virus (FeLV) and mice with murine leukaemia virus (MuLV). Between 1 × 10 4 TCID50 [29] and 1 × 10 6 ffu [30] FeLV was sufficient to infect cats oronasally, and 2 × 10 4 ffu was used for successful infection of mice with MuLV [31]. The absence of antibodies may be explained either by the absence of replication or by the fact that pigs are immunologically tolerant to PERVs, as they are endogenous.…”