Incomplete but Infectious Vaccinia Virions Are Produced in the Absence of Oncolysis in Feline SCCF1 Cells

Vaccinia virus is a large, enveloped virus of the poxvirus family. It has broad tropism and typically virus replication culminates in accumulation and lytic release of intracellular mature virus (IMV), the most abundant form of infectious virus, as well as release by budding of extracellular enveloped virus (EEV). Vaccinia viruses have been modified to replicate selectively in cancer cells and clinically tested as oncolytic agents. During preclinical screening of relevant cancer targets for a recombinant Western Reserve strain deleted for both copies of the thymidine kinase and vaccinia growth factor genes, we noticed that confluent monolayers of SCCF1 cat squamous carcinoma cells were not destroyed even after prolonged infection. Interestingly, although SCCF1 cells were not killed, they continuously secreted virus into the cell culture supernatant. To investigate this finding further, we performed detailed studies by electron microscopy. Both intracellular and secreted virions showed morphological abnormalities on ultrastructural inspection, suggesting compromised maturation and morphogenesis of vaccinia virus in SCCF1 cells. Our data suggest that SCCF1 cells produce a morphologically abnormal virus which is nevertheless infective, providing new information on the virus-host cell interactions and intracellular biology of vaccinia virus.     

Ubiquitous calpains promote caspase-12 and JNK activation during endoplasmic reticulum stress-induced apoptosis

Ubiquitously expressed mu- and m-calpain proteases are implicated in development and apoptosis. They consist of 80-kDa catalytic subunits encoded by the capn1 and capn2 genes, respectively, and a common 28-kDa regulatory subunit encoded by the capn4 gene. The regulatory subunit is required to maintain the stability and activity of mu- and m-calpains. Accordingly, genetic disruption of capn4 in the mouse eliminated both ubiquitous calpain activities. In embryonic fibroblasts derived from these mice, calpain deficiency correlated with resistance to endoplasmic reticulum (ER) stress-induced apoptosis, and this was directly related to a calpain requirement for activation of both caspase-12 and the ASK1-JNK cascade. This study provides compelling genetic evidence for calpain's role in caspase-12 activation at the ER, and reveals a novel role for the ubiquitous calpains in ER-stress induced apoptosis and JNK activation.     

The Siva protein is a novel intracellular ligand of the CD4 receptor that promotes HIV-1 envelope-induced apoptosis in T-lymphoid cells

In addition to its positive signaling function in the antigen presentation process, CD4 acts as the primary receptor for HIV-1. Contact between CD4 and the viral envelope leads to virus entry, but can also trigger apoptosis of uninfected CD4⁺ T-cells through a mechanism that is poorly understood. We show that Siva-1, a death domain-containing proapoptotic protein, associates with the cytoplasmic domain of CD4. This interaction is mediated by the cysteine-rich region found in the C-terminal part of the Siva-1 protein. Expression of Siva-1 specifically increases the susceptibility of both T-cell lines and unstimulated human primary CD4⁺ T-lymphocytes to CD4-mediated apoptosis triggered by the HIV-1 envelope, and results in activation of a caspase-dependent mitochondrial pathway. The same susceptibility is observed in T-cells expressing a truncated form of CD4 that is able to recruit Siva-1 but fails to associate with p56^Lck, indicating that Siva-1 participates in a pathway independent of the p56^Lck kinase activity. Altogether, these results suggest that Siva-1 might participate in the CD4-initiated signaling apoptotic pathway induced by the HIV-1 envelope in T-lymphoid cells. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Cryo-electron microscopy of vitreous sections

Since the beginning of the 1980s, cryo-electron microscopy of a thin film of vitrified aqueous suspension has made it possible to observe biological particles in their native state, in the absence of the usual artefacts of dehydration and staining. Combined with 3-d reconstruction, it has become an important tool for structural molecular biology. Larger objects such as cells and tissues cannot generally be squeezed in a thin enough film. Cryo-electron microscopy of vitreous sections (CEMOVIS) provides then a solution. It requires vitrification of a sizable piece of biological material and cutting it into ultrathin sections, which are observed in the vitrified state. Each of these operations raises serious difficulties that have now been overcome. In general, the native state seen with CEMOVIS is very different from what has been seen before and it is seen in more detail. CEMOVIS will give its full potential when combined with computerized electron tomography for 3-d reconstruction.     

Interleukin-13 interferes with CFTR and AQP5 expression and localization during human airway epithelial cell differentiation

Interleukin-13 (IL-13) is a central regulator of Th2-dominated respiratory disorders such as asthma. Lesions of the airway epithelial barrier frequently observed in chronic respiratory inflammatory diseases are repaired through proliferation, migration and differentiation of epithelial cells. Our work is focused on the effects of IL-13 in human cellular models of airway epithelial cell regeneration. We have previously shown that IL-13 altered epithelial cell polarity during mucociliary differentiation of human nasal epithelial cells. In particular, the cytokine inhibited ezrin expression and interfered with its apical localization during epithelial cell differentiation in vitro. Here we show that CFTR expression is enhanced in the presence of the cytokine, that two additional CFTR protein isoforms are expressed in IL-13-treated cells and that part of the protein is retained within the endoplasmic reticulum. We further show that aquaporin 5 expression, a water channel localized within the apical membrane of epithelial cells, is completely abolished in the presence of the cytokine. These results show that IL-13 interferes with ion and water channel expression and localization during epithelial regeneration and may thereby influence mucus composition and hydration.     

Microorganisms immobilized by membrane inclusion: kinetic measurements in a fixed bed bioreactor and oxygen consumption calculations

Cells living in the pores of macroporous carriers can be immobilized by coating the carriers with a porous membrane. To evaluate the performance of cells immobilized with such a technique, a fixed bed bioreactor was used to study the oxidation of D-sorbitol to L-sorbose by Acetobacter suboxydans. Comparisons were made of immobilized cells to cells living in the pores of a non-coated carrier and to cells living in the absence of a carrier (“submerged cells”). Productivity was similar in all three cultures (4.6–6.3?g sorbose?l^?1?h^?1). Biomass concentration at the outlet was highest for submerged cells (1.3?·?10⁹?cells?ml^?1) but was equal for coated and non-coated carriers (0.4?·?10⁹?cells?ml^?1). Examination of the coated carriers under the electron microscope revealed that only a thin layer near the surface was actually colonized by bacteria. Interestingly, when normalized on the basis of volume, sorbitol oxidation in the colonized layer appeared to be about 100-fold faster than in the bulk medium. A model was derived for oxygen relations inside the coated carriers. This model implicates that the inner parts of the carrier are not colonized by bacteria due to oxygen limitation. The findings indicate that coated carriers have potential to catalyze biotransformations at very high rates, and identify oxygen supply and confinement of cells to the carriers as issues that need further attention. The mathematical model for oxygen concentration profiles inside the coated carriers will be useful for designing improved carriers.