Influenza Pseudotyped lentivirus: A flexible useful tool for influenza research

Abstract

Background: Influenza envelop, hemagglutinin (HA), can be incorporated on the surface of replication-deficient lentiviral particles by a process call pseudotyping (reviewed recently in [1]). These chimerical viral particles can be used to investigate HA-related biological processes such as the receptor binding or the identification of HA-specific antibodies in neutralizationbased serological assays. In this presentation, we will show, in the case of H5 from highly pathogenic avian influenza H5N1, how such particles (H5pp) can be produced and used for serodiagnostics of H5N1 safely in Biosafety Level 2 conditions. Results: After biochemical and functional characterizations of these H5-pseudoparticles (H5pp) [2], H5pp serological assay has been thoroughly optimized and validated [3]. During the evaluation of the assay with paired-sera from seasonal and H5N1 pandemic flu vaccines, we could show, thanks to the increased sensitivity of H5pp assay compared with the conventional microneutralization, that the induction of heterosubtypic neutralizing antibodies in some healthy volunteers unexposed to H5N1 mediated by cross-reaction to the H5 HA [4]. The assay we also used to investigate the kinetics of anti-H5 neutralizing antibodies in naturally H5N1- infected patients with severe clinical illness or asymptomatic infection. We showed that people with asymptomatic H5N1 infection have lower H5N1 antibody titers compared to those with severe illness and that in many asymptomatically infected patients the antibody titer decreased to levels below the threshold of positivity within one year [5]. In another study, H5pp assay was used in field investigation of H5N1 transmission in rural Cambodia and showed for example that bathing or swimming in the community ponds was associated to higher risk of H5N1 infection to human [6]. Finally, as H5pp can mimic the presentation of HA at surface of influenza virus, H5pp were used to explore at atomic level the receptor-virus interactions without the potential confounding sialidase activity from the neuraminidase (proof-of-concept can be found in [7]). Conclusion: Through divers examples, we have illustrated the flexibility of influenza pseudotyped lentiviral particles technology that makes it a kind of “Swiss army knife” for flu virologists.