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Immunofluorescent sites in vero cells infected with the flavivirus Kunjin
Abstract:
The sites of replication and of accumulation of viral macromolecules were examined using fluorescent antibodies to viral products and to cell organelles. Synthesis of envelope protein and its accumulation in a narrow rim around the nucleus were detected at 4 hours post infection; concurrently, a progressive change was observed in the rough endoplasmic reticulum from a fine to a coarse network emanating from around the nucleus. This change in the network was visible by light microscopy. The immunofluorescent sites of viral RNA synthesis, located by use of anti-double stranded RNA, extended from the perinuclear region in another fine network which included many small foci or vesicles; these sites were also visible by light microscopy late in infection. None of these changes were associated with any visible redistribution of actin, intermediate filaments or microtubules, and no nuclear involvement was detected. However, when microtubules were disrupted by vinblastine treatment of cells, the distribution of the immunofluorescent sites of viral RNA synthesis was modified and the virus yield was reduced by at least 10-fold. These results confirmed our biochemical studies showing separation of viral sites of RNA synthesis and translation, and the accumulation of envelope protein in nuclear-associated membranes. The relevance of these observations is discussed in relation to the reports of specific membrane structures induced in flavivirus-infected cells.
Insights
Viral RNA synthesis and envelope protein accumulation occur in distinct cellular compartments. Microtubule disruption significantly reduces virus yield, highlighting their importance in viral replication.
Area of Science:
- Cell Biology
- Virology
- Molecular Biology
Background:
- Viral replication involves complex interactions between viral components and host cell machinery.
- Understanding the precise localization of viral RNA synthesis and protein accumulation is crucial for deciphering viral life cycles.
- Flaviviruses are known to induce specific membrane structures during infection, but their functional significance remains under investigation.
Purpose of the Study:
- To investigate the cellular sites of viral macromolecule replication and accumulation during infection.
- To elucidate the role of host cell organelles and cytoskeletal elements in viral RNA synthesis and protein transport.
- To determine the impact of microtubule disruption on viral RNA synthesis localization and virus production.
Main Methods:
- Immunofluorescence microscopy using antibodies against viral products and cellular organelles.
- Light microscopy to observe changes in the rough endoplasmic reticulum.
- Treatment with vinblastine to disrupt microtubules and assess its effects on viral RNA synthesis and virus yield.
Main Results:
- Envelope protein synthesis and accumulation were observed in a rim around the nucleus starting at 4 hours post-infection.
- A progressive change in the rough endoplasmic reticulum network was detected, visible by light microscopy.
- Immunofluorescent sites of viral RNA synthesis formed a fine network extending from the perinuclear region.
- No redistribution of actin, intermediate filaments, or microtubules was observed; no nuclear involvement was detected.
- Disruption of microtubules by vinblastine altered viral RNA synthesis distribution and reduced virus yield by over 10-fold.
Conclusions:
- Viral RNA synthesis and envelope protein accumulation occur in distinct cellular locations, likely associated with specific membrane structures.
- Host cell microtubules play a critical role in the proper localization of viral RNA synthesis and efficient virus production.
- These findings provide insights into the mechanisms of flavivirus replication and the formation of virus-induced membrane compartments.