No abstract

Replication-competent lentivirus (RCL) may be generated during the production phase or subsequently after introduction of a lentiviral vector into target cells, potentially by homologous or nonhomologous recombination. Because most gene transfer of HIV-based vectors involves the use of high-titer vesicular stomatitis virus (VSV) G-pseudotyped particles, one particular concern would be the generation of an RCL of altered host range, i.e., one that has incorporated the VSV G envelope in cis configuration. We report here on the artificial generation and properties of such a virus, including its detection after biological amplification. Viral spread, beginning with a very low inoculum, takes several weeks in culture and is characterized by "autoinfection," resulting in multiple proviral copies per cell, higher levels of viral gene expression, and eventual cell death. After this initial amplification step, the RCL is easily detectable by standard p24 assay or by "marker-rescue" assay. For the latter, a 293T-based cell line that has an integrated replication-defective provirus encoding alkaline phosphatase (AP) was used and mobilization of AP-containing virus was detected by transduction of naïve cells. Replication-defective virus was not amplified nor detected, demonstrating assay specificity. These results suggest that these artificial RCLs of broad host range have slightly different biological properties compared to wild-type HIV but still spread and are readily detectable.

No abstract

The interaction between viral HA (hemagglutinin) and oligosaccharide of the host plays an important role in the infection and transmission of avian and human flu viruses. Until now, this interaction has been classified by sialyl(α2-3) or sialyl(α2-6) linkage specificity of oligosaccharide moieties for avian or human virus, respectively. In the case of H5N1 and newly mutated flu viruses, classification based on the linkage type does not correlate with human infection and human-to-human transmission of these viruses. It is newly suggested that flu infection and transmission to humans require high affinity binding to the extended conformation with long length sialyl(α2-6)galactose containing oligosaccharides. On the other hand, the avian flu virus requires folded conformation with sialyl(α2-3) or short length sialyl(α2-6) containing trisaccharides. This suggests a potential future direction for the development of new species-specific antiviral drugs to prevent and treat pandemic flu.

The infection of pandemic influenza viruses such as swine flu (H1N1) and avian flu viruses to the host cells is related to the following two factors: First, the surface protein such as HA (hemagglutinin) and NA (neuraminidase) of the influenza virus. Second, the specific structure of the oligosaccharide [sialic acid(α2-6) galactose(β1-4)glucose or sialic acid(α2-3)galactose(β1-4)glucose] on the host cell. After recognizing the specific structure of the oligosaccharide on the surface of host cells by the surface protein of the influenza virus, the influenza virus can secrete sialidase and cleave the sialic acid attached on the final position of the specific structure of the oligosaccharide on the surface of host cells. Tamiflu (oseltamivir), known as a remedy of swine flu, has a saccharide analog structure, especially the sialic acid analog. Tamiflu can inhibit the invasion of influenza viruses (swine flu and avian flu viruses) into the host cells by competition with sialic acid on the terminal position of the specific oligosaccharide on the surface of the host cell. Because of the emergence of Tamiflu resistance, the development of new potent anti-influenza inhibitors is needed. The inhibitors with positive-charge groups have potential as antiviral therapeutics, and the strain specificity must also be resolved.