Janeczko, and M. or spleen. WT mouse macrophages express WASP but not N-WASP; after VV contamination, WASP levels increase threefold. KO macrophages lack N-WASP expression and, when VV infected, are incapable SR-13668 of inducing actin tails and generating extracellular computer virus. These functions were rescued in KO macrophages after ectopic WASP expression. Overall, our findings demonstrate that WASP has a role in orthopoxvirus SR-13668 infections. Use of WASP HOX11L-PEN proteins for computer virus spread SR-13668 via the actin tail provides a selective advantage for VV, and probably variola virus, dissemination to distant tissues. Although smallpox has been eradicated, little is known of the mechanisms responsible for the high mortality rate due to this disease (9, 21). Since vaccination has been discontinued (9), recent functions of bioterrorism and the possible use of variola computer virus as a biological weapon raise major issues about the security of the human population. Second-generation vaccines are needed, as although the current vaccine has proved effective, adverse effects have been reported (21). Drugs must also be developed that can be used safely to resist a potential bioterrorist attack with variola computer virus. Further understanding of viral distributing mechanisms in the human host is thus needed. Using DNA microarrays of the Western Reserve (WR) and altered Ankara strains (14, 15), we recognized a set of human genes that are induced selectively during the course of vaccinia computer virus (VV) contamination. One of these genes encodes the Wiskott-Aldrich syndrome protein (WASP), a member of the structurally related protein family termed the WASP family. These proteins are implicated in numerous actin-regulated processes, including cell motility, epithelial cell adhesion, and pathogen F-actin tail formation (20, 34-36, 38). You will find five known WASP family members, termed WASP, N-WASP, and three isoforms of WAVE (WASP family verprolin-homologous protein, also called Scar) (6). VV is the only computer virus known to use actin-based motility to facilitate distributing between cells (7). Actin assembly on VV is usually mediated by the viral protein A36R (11, 12, 27, 28). VV replicates in the infected host cell cytoplasm in a complex process that leads to production of SR-13668 two unique infectious forms (21), the intracellular mature virion (IMV) and the extracellular enveloped virion (EEV). The EEV is the form involved in computer virus dissemination through the host, contributing to distant computer virus spread, whereas the IMV is probably more efficient in local cell-to-cell transmission by cell fusion (3, 4, 30). As contamination of human cells with VV induces WASP (14, 15), and N-WASP is essential to the VV exit pathway in infected HeLa cells via actin tail formation (11, 12), we analyzed the role of WASP in in vivo contamination. In WASP knockout (KO) mice, we found that VV requires WASP for computer virus distributing, with a correlation between loss of actin tail formation and a decrease in virulence. This in vivo study revealed a role for a cellular protein with a function in actin-regulated processes in VV contamination. MATERIALS AND METHODS Cells, viruses, and contamination conditions. VV wild-type (WT) WR was cultured in spinner HeLa cells, purified by banding on sucrose gradients as previously explained (24), and titrated in BSC-40 African green monkey kidney cells. BSC-40 cells were managed in Dulbecco’s altered Eagle medium. Viral inoculation of mice and sample collection. The origin of WASP?/? mice has been explained previously (40). WASP?/? and control WT C57/BL-6 mice (8 to 12 weeks aged) were immunized intraperitoneally (i.p.) with VV (108 PFU) in 200 l of sterile phosphate-buffered saline (PBS) or intranasally (i.n.) with VV (106 PFU) in 20 l of PBS. Animals were sacrificed at numerous times postinoculation, and the spleen, liver, ovaries, and lungs were removed, washed with sterile PBS, and stored at ?70C. Serum was obtained by retro-orbital bleeding before the inoculation and 3 to 10 days after the i.n. inoculation and was allowed to clot for 30 min at 37C; after samples were left at 4C overnight, they ere spun in a microcentrifuge and serum samples were removed and stored at ?20C. Quantitative real-time RT-PCR. RNA (1 g) was reverse transcribed with the Superscript first-strand synthesis system for reverse transcription (RT)-PCR.