Role of the Human Parainfluenza Virus Type 3 Fusion Machinery in Viral Growth in the Natural Host

Abstract

Human parainfluenza virus type 3 (HPIV3) is a single‐stranded, negative‐sense RNA enveloped virus that causes severe respiratory diseases in children; including croup, bronchiolitis and pneumonia. HPIV3 infects its target cells by the coordinated action of the receptor binding protein hemagglutinin‐neuraminidase (HN) and the fusion (F) envelope glycoprotein, which together comprise the molecular fusion machinery. Previous studies from our lab show that viruses bearing HN‐F machinery that confer excellent growth in monolayer cultures cannot thrive in vivo. In turn, viruses that efficiently replicate in vivo‐ for example clinical isolates (CIs) ‐ bear HN‐F machinery that cannot cope with in vitro cell culture. Our aim is to characterize the fusion machinery properties of lung adapted HPIV3 virions. We hypothesized that circulating HPIV3 viruses (CIs) bear HN‐F fusion machineries well suited to the natural environment. In order to characterize the different functions of the CIs HNs and F HPIV3, viral RNA was extracted from CIs and the genomic sequences were analyzed by deep sequencing techniques. The cDNA encoding the CIs viral glycoproteins were inserted in expression vectors and assayed for expression levels by a biotinlyation assay. Additionally, neuraminidase activity was tested for all CIs HNs. Results were expressed as relative percentage of lab adapted ‐HPIV3 HN. Preliminary results suggest that HPIV3 CIs have a higher neuraminidase activity in comparison to lab adapted ‐HPIV3 HN and low fusogenicity. Overall, our results suggest that the fusion machinery of CIs is more stable and less readily activated than viruses adapted to growth in culture.Support or Funding InformationGrant: 5R01AI031917‐23Grant: NIH NIGMS R25GM096955