Cellular and viral mechanisms of HIV-1 transmission mediated by dendritic cells.

Dendritic cells (DCs) play a key role in the initial infection and cell-to-cell transmission events that occur upon HIV-1 infection. DCs interact closely with CD4(+) T cells, the main target of HIV-1 replication. HIV-1 challenged DCs and target CD4(+) T cells form a virological synapse that allows highly efficient transmission of HIV-1 to the target CD4(+) T cells, in the absence of productive HIV-1 replication in the DCs. Immature and subsets of mature DCs show distinct patterns of HIV-1 replication and cell-to-cell transmission, depending upon the maturation stimulus that is used. The cellular and viral mechanisms that promote formation of the virological synapse have been the subject of intense study and the most recent progress is discussed here. Characterizing the cellular and viral factors that affect DC-mediated cell-to-cell transmission of HIV-1 to CD4(+) T cells is vitally important to understanding, and potentially blocking, the initial dissemination of HIV-1 in vivo.

Evidence for the formation of a heptameric ion channel complex by the hepatitis C virus p7 protein in vitro.

The p7 protein of hepatitis C virus functions as an ion channel both in vitro and in cell-based assays and is inhibited by amantadine, long alkyl chain imino-sugar derivatives, and amiloride compounds. Future drug design will be greatly aided by information on the stoichiometry and high resolution structure of p7 ion channel complexes. Here, we have refined a bacterial expression system for p7 based on a glutathione S-transferase fusion methodology that circumvents the inherent problems of hydrophobic protein purification and the limitations of chemical synthesis. Rotational averaging and harmonic analysis of transmission electron micrographs of glutathione S-transferase-FLAG-p7 fusion proteins in liposomes revealed a heptameric stoichiometry. The oligomerization of p7 protein was then confirmed by SDS-PAGE and mass spectrometry analysis of pure, concentrated FLAG-p7. The same protein was also confirmed to function as an ion channel in suspended lipid bilayers and was inhibited by amantadine. These data validate this system as a means of generating high resolution structural information on the p7 ion channel complex.