Comparative Study of Fusogenic Activity of H1 and H5 Subtypes Influenza Virus Hemagglutinins.

Influenza virus hemagglutinins are surface proteins responsible for fusion of the viral and cellular membranes. Their capacity to mediate membrane fusion (fusogenic activity) is studied by various methods, including the syncytium formation and pseudovirus transduction methods. We constructed plasmids coding for genes of three H1 and one H5 hemagglutinins and compared their fusogenic activities. Hemagglutinin capacity to induce syncytium formation did not always correlate with the transduction activity of the respective pseudoviruses. Hemagglutinin H5 exhibited high fusogenic activity in studies by both methods, however, two of the studied H1 hemagglutinins induced the formation of syncytia, but did not mediate pseudovirus transduction. This could be due to different capsid sizes of influenza virus and vesicular stomatitis virus, which determines their different permeability through the fusion pore.

N-Heterocyclic borneol derivatives as inhibitors of Marburg virus glycoprotein-mediated VSIV pseudotype entry.

There is currently no approved antiviral therapy for treatment of Marburg virus disease (MVD). Although filovirus infection outbreaks are quite rare, the high mortality rates in such outbreaks make the development of anti-filoviral drugs an important goal of medical chemistry and virology. Here, we performed screening of a large library of natural derivatives for their virus entry inhibition activity using pseudotype systems. The bornyl ester derivatives containing saturated N-heterocycles exhibited the highest antiviral activity. It is supposed that compounds with specific inhibitory activity toward MarV-GP-dependent virus entry will inhibit the rVSIV-ΔG-MarV-GP pseudotype much more efficiently than the control rVSIV-ΔG-G pseudotype. At the same time, the compounds similarly inhibiting both pseudotypes will likely affect rVSIV capsid replication or the cellular mechanisms common to the entry of both viruses. Borneol itself is not active against both pseudotypes and is nontoxic, whereas its derivatives have varying toxicity and antiviral activity. Among low-toxic borneol derivatives, six compounds turned out to be relatively specific inhibitors of MarV-GP-mediated infection (SC > 10). Of them, compound 6 containing a methylpiperidine moiety exhibited the highest virus-specific activity. Notably, the virus-specific activity of this compound is twice as high as that of the reference.

A vesicular stomatitis pseudovirus expressing the surface glycoproteins of influenza A virus.

Pseudotyped viruses bearing the glycoprotein(s) of a donor virus over the nucleocapsid core of a surrogate virus are widely used as safe substitutes for infectious virus in virology studies. Retroviral particles pseudotyped with influenza A virus glycoproteins have been used recently for the study of influenza hemagglutinin and neuraminidase-dependent processes. Here, we report the development of vesicular-stomatitis-virus-based pseudotypes bearing the glycoproteins of influenza A virus. We show that pseudotypes bearing the hemagglutinin and neuraminidase of H5N1 influenza A virus mimic the wild-type virus in neutralization assays and sensitivity to entry inhibitors. We demonstrate the requirement of NA for the infectivity of pseudotypes and show that viruses obtained with different NA proteins are significantly different in their transduction activities. Inhibition studies with oseltamivir carboxylate show that neuraminidase activity is required for pseudovirus production, but not for the infection of target cells with H5N1-VSV pseudovirus. The HA-NA-VSV pseudoviruses have high transduction titers and better stability than the previously reported retroviral pseudotypes and can replace live influenza virus in the development of neutralization assays, screening of potential antivirals, and the study of different HA/NA reassortants.