Cover photograph (Copyright © 2001, American Society for Microbiology. All rights reserved.): A BT7-H cell expressing the poliovirus protein 2BC was processed for indirect immunofluorescence with antibodies against poliovirus protein 2B (red) and endoplasmic reticulum (ER)-resident protein p63 (green). A three-dimensional reconstruction (surface rendering) was prepared after deconvolution of consecutive optical sections obtained by confocal microscopy. The viral protein 2BC triggers vesicle budding from the ER. The vesicles exclude the ER membrane protein p63, with colocalization of p63 and 2B being restricted to collar-like transition sites (yellow). The vesicles were found to carry components of the COPII complex, and thus are homologous to the transport vesicles of the anterograde membrane traffic. During poliovirus infection, vesicles destined to carry the viral RNA replication complex are formed similarly. Original image area was 2 by 2 µm. (See related article on page 9808.)