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A persistent variant of influenza C virus fails to interact with actin filaments during viral assembly
A Hechtfischer1, H Meier-Ewert, M Marschall
1Abteilung für Virologie, Institut für Medizinische Mikrobiologie, Immunologie und Hygiene, Technische Universität München, Germany.
Abstract:
C/AA-pi virus, a variant of influenza C/Ann Arbor/1/50 virus, establishes persistent infections in MDCK cells, characterized by low levels of progeny production. During viral assembly, nucleoprotein (NP) was found homogeneously distributed over cytoplasmic and nuclear compartments and matrix (M) protein was likewise localized in a barely structured fashion. In contrast, infections with nonpersistent influenza A, B and C viruses produced cytoplasmic granular structures, which typically consisted of colocalized NP and M proteins. Studies on the in vitro interaction between NP and M proteins revealed identical binding capacities comparing influenza C wild-type virus with the persistent variant. Cytochalasin D treatment of infected cells demonstrated that NP protein of the wild-type virus, but not of the persistent variant, was distinctly associated with cellular actin filaments. Moreover, the assembly characteristics of wild-type virus were modulated in the presence of recombinant persistent-type NP protein towards a behaviour similar to persistent infection. Cell type specificity was particularly illustrated in C/AA-pi virus-infected Vero cells, which did not support viral persistence, but produced granular wild-type-like complexes. Thus, interaction between NP, M and actin proteins (i) is a basic part of the viral assembly process, (ii) is dominantly modulated by NP protein and (iii) is specifically altered in the case of persistent infection.
Insights
Persistent influenza C virus variants alter viral assembly by changing nucleoprotein (NP) interactions with actin. This impacts progeny production and viral structure, unlike wild-type influenza viruses.
Area of Science:
- Virology
- Cell Biology
- Molecular Biology
Background:
- Influenza C virus infections can be persistent, characterized by reduced progeny production.
- Viral assembly involves interactions between viral proteins like nucleoprotein (NP) and matrix (M) protein.
- Cellular actin filaments play a role in the assembly of some viruses.
Purpose of the Study:
- To investigate the molecular mechanisms underlying persistent influenza C virus infections.
- To compare the assembly characteristics of persistent influenza C variants with wild-type strains.
- To elucidate the role of nucleoprotein (NP), matrix (M) protein, and actin in viral persistence.
Main Methods:
- Infection of Madin-Darby canine kidney (MDCK) and Vero cells with influenza C/AA-pi virus and wild-type strains.
- Immunofluorescence microscopy to visualize the distribution of NP and M proteins.
- In vitro binding assays to assess NP-M protein interactions.
- Cytochalasin D treatment to study the association of NP with actin filaments.
Main Results:
- Persistent C/AA-pi virus showed homogeneous NP and M protein distribution, unlike the granular structures in wild-type infections.
- NP and M proteins from wild-type and persistent viruses exhibited similar in vitro binding.
- Wild-type NP associated with actin filaments, while persistent NP did not; this interaction was modulated by NP type.
- Vero cells supported wild-type-like complex formation but not viral persistence.
Conclusions:
- The interaction between NP, M protein, and actin is crucial for viral assembly.
- Nucleoprotein (NP) plays a dominant role in modulating these interactions.
- Altered NP-actin interaction is a key feature distinguishing persistent influenza C virus infection from wild-type strains.