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Mengovirus and encephalomyocarditis virus poly(C) tract lengths can affect virus growth in murine cell culture
L R Martin1, Z C Neal, M S McBride
1Institute for Molecular Virology and Department of Biochemistry, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA.
Abstract:
Many virulent aphthoviruses and cardioviruses have long homopolymeric poly(C) tracts in the 5' untranslated regions of their RNA genomes. A panel of genetically engineered mengo-type cardioviruses has been described which contain a variety of different poly(C) tract lengths. Studies of these viruses have shown the poly(C) tract to be dispensable for growth in HeLa cells, although the relative murine virulence of the viruses correlates directly and positively with tract length. Compared with wild-type mengovirus strain M, mutants with shortened poly(C) tracts grow poorly in mice and protectively immunize rather than kill recipient animals. In the present study, several murine cell populations were tested to determine whether, unlike HeLa cells, they allowed a differential amplification of viruses with long or short poly(C) tracts. Replication and cytopathic studies with four hematopoietically derived cell lines (CH2B, RAW 264.7, A20.J, and P815) and two murine fibroblast cell lines [L929 and L(Y)] demonstrated that several of these cell types indeed allowed differential virus replication as a function of viral poly(C) tract length. Among the most discerning of these cells, RAW 264.7 macrophages supported vigorous lytic growth of a long-tract virus, vMwt (C(44)UC(10)), but supported only substantially diminished and virtually nonlytic growth of vMC(24) (C(13)UC(10)) and vMC(0) short-tract viruses. The viral growth differences evident in all cell lines were apparent early and continuously during every cycle of virus amplification. The data suggest that poly(C) tract-dependent attenuation of mengovirus may be due in part to a viral replication defect manifest in similar hematopoietic-type cells shortly after murine infection. The characterized cultures should provide excellent tools for molecular study of poly(C) tract-mediated virulence.
Insights
Mengovirus virulence in mice depends on poly(C) tract length. Certain mouse cell types, like macrophages, differentially replicate viruses based on poly(C) tract length, suggesting a replication defect contributes to reduced virulence.
Area of Science:
- Virology
- Molecular Biology
- Immunology
Background:
- Aphthoviruses and cardioviruses possess long poly(C) tracts in their 5' untranslated regions.
- Poly(C) tract length influences mengovirus murine virulence, with longer tracts correlating with increased virulence.
- Previous studies showed poly(C) tracts are dispensable for HeLa cell growth but critical for mouse virulence.
Purpose of the Study:
- To investigate if specific murine cell populations differentially amplify viruses based on poly(C) tract length.
- To identify cell types that exhibit differential replication of mengovirus variants with varying poly(C) tract lengths.
- To explore the role of cellular replication defects in poly(C) tract-mediated viral attenuation.
Main Methods:
- Genetically engineered mengo-type cardioviruses with diverse poly(C) tract lengths were utilized.
- Replication and cytopathic effects were assessed in multiple murine cell lines, including hematopoietic and fibroblast types.
- RAW 264.7 macrophages were specifically analyzed for differential growth of long-tract versus short-tract viruses.
Main Results:
- Several murine cell lines, notably RAW 264.7 macrophages, demonstrated differential virus replication correlating with poly(C) tract length.
- Long-tract mengovirus (vMwt) exhibited vigorous lytic growth in RAW 264.7 cells, while short-tract mutants (vMC(24), vMC(0)) showed significantly diminished, nonlytic growth.
- Differential replication was observed early and consistently throughout all cycles of virus amplification.
Conclusions:
- Murine hematopoietic-type cells can exhibit replication defects dependent on viral poly(C) tract length.
- These cellular replication differences may contribute to the attenuation of mengovirus strains with shorter poly(C) tracts in vivo.
- The characterized cell cultures serve as valuable tools for studying poly(C) tract-mediated virulence mechanisms.