UNLABELLED PA-X is a newly discovered protein that decreases the virulence of the 1918 H1N1 virus in a mouse model. However, the role of PA-X in the pathogenesis of highly pathogenic avian influenza viruses (HPAIV) of the H5N1 subtype in avian species is totally unknown. By generating two PA-X-deficient viruses and evaluating their virulence in different animal models, we show here that PA-X di...

In guinea pigs, methotrexate and x-radiation have been employed to block the development of delayed hypersensitivity and of antibody to vaccinia virus during experimental infection. Animals whose specific responses were blocked by x-radiation and methotrexate recovered from vaccinia virus infection as rapidly as non-treated control animals suggesting that these responses were not essential in r...

Exposure of Venezuelan equine encephalomyelitis (VEE) virus (at -70 C) to 6 x 106 r y-radiation (6WCo) resulted in loss of lethality for young adult mice and guinea pigs, and loss of capacity to produce plaques or cyLopathic effects in tissue culture. The suckling mouse was more sensitive for detecting live virus in radiated suspensions than was the adult mouse or guinea pig. Live virus was dem...

Exposure of Venezuelan equine encephalomyelitis (VEE) virus (at -70 C) to 6 x 10 r gamma-radiation (Co) resulted in loss of lethality for young adult mice and guinea pigs, and loss of capacity to produce plaques or cytopathic effects in tissue culture. The suckling mouse was more sensitive for detecting live virus in radiated suspensions than was the adult mouse or guinea pig. Live virus was de...

The following viruses were used in the form of pre­ parations purified from infected allantoic fluids by two cycles of alternate low (3,000 x g, 20 mins.) and high speed centrifugations (conditions are given in parenthe­ ses) : Inhibitor resistant variant of A 2 (Singapore) 57 influenza virus (48,000 x g, 40 mins.), previously puri­ fied by adsorption onto and elution from rooster red blood cel...

Infection of JLS-V9 cells in culture with Rauscher murine leukemia virus induced the appearance on the cell surface of two classes of viral proteins: Rauscher murine leukemia virus gp70, and glycoproteins related to the viral core (gag) proteins with apparent molecular weights in sodium dodecyl sulfate polyacrylamide gels of 80 x 10(3) and 95 x 10(3). The latter proteins were identified by lact...

The capacity of monoclonal antibodies to protect mice passively against yellow fever (YF) virus infection was investigated. Both neutralizing (54K-specific) and non-neutralizing (54K- and 48K-specific) antibodies protected mice against challenge with the RMP substrain of YF virus. Average survival times of mice inoculated intracerebrally with a standard lethal dose of YF virus differed accordin...

Three consecutive plaque purifications of four chimeric yellow fever virus-dengue virus (ChimeriVax-DEN) vaccine candidates against dengue virus types 1 to 4 were performed. The genome of each candidate was sequenced by the consensus approach after plaque purification and additional passages in cell culture. Our data suggest that the nucleotide sequence error rate for SP6 RNA polymerase used in...