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Giardiavirus enters Giardia lamblia WB trophozoite via endocytosis
1Molecular Parsitology Laboratory, Academia Sinica, Taipei, Taiwan, Republic of China.
Abstract:
As part of our continuing effort in the study of Giardiavirus life cycle, the early events of Giardia lamblia virus (GLV) infection in the trophozoites of G. lamblia WB strain were examined. Electron microscopy showed that GLV particles were initially localized on plasma membrane. As time progresses, GLV was translocated to the peripheral vacuole and then spread to the cytoplasm. Inhibitors of endocytosis such as sodium azide, chloroquine, or ammonium chloride disrupted viral infection when the drug was added simultaneously with the infecting GLV. The inhibitory effect was reduced when sodium azide or chloroquine was added at various intervals after infection. When cells infected for 1 hr were examined by immunofluorescence staining, sodium azide greatly reduced GLV staining signal in general while chloroquine restricted the staining signal to a few bright spots. Significantly more GLV was found in the peripheral vacuoles of chloroquine-treated cells than untreated controls by semiquantitative electron microscopy. In contrast, only a reduced amount of GLV was found in the peripheral vacuoles of sodium azide-treated cells. These results suggest that sodium azide reduces the internalization of infecting GLV, while chloroquine confines the virus in the peripheral vacuoles and, consequently, leads to nonproductive infection. We conclude from these observations that the entry of GLV into the susceptible WB cells in the event of infection is most likely mediated by endocytosis.
Insights
Giardiavirus (GLV) enters Giardia lamblia cells via endocytosis. Inhibitors like sodium azide and chloroquine disrupt this process, affecting viral infection.
Area of Science:
- Microbiology
- Virology
- Cell Biology
Background:
- The Giardia lamblia virus (GLV) is a virus that infects Giardia lamblia, a protozoan parasite.
- Understanding the early events of GLV infection is crucial for elucidating its life cycle and potential impact.
Purpose of the Study:
- To investigate the initial stages of Giardia lamblia virus (GLV) infection in G. lamblia trophozoites.
- To determine the mechanism of GLV entry into susceptible host cells.
Main Methods:
- Electron microscopy to visualize GLV particle localization and translocation.
- Use of endocytosis inhibitors (sodium azide, chloroquine, ammonium chloride) to assess their effect on infection.
- Immunofluorescence staining to detect GLV presence in infected cells.
- Semi-quantitative electron microscopy for precise GLV quantification in vacuoles.
Main Results:
- GLV particles initially bind to the plasma membrane, then move to peripheral vacuoles and cytoplasm.
- Endocytosis inhibitors disrupted infection when added simultaneously with GLV.
- Sodium azide reduced overall GLV internalization, while chloroquine trapped GLV in peripheral vacuoles.
- Chloroquine treatment led to nonproductive infections, suggesting impaired viral progression.
Conclusions:
- The entry of GLV into G. lamblia WB cells is likely mediated by endocytosis.
- Sodium azide inhibits GLV internalization, whereas chloroquine blocks viral progression from peripheral vacuoles.
- These findings provide insights into the early steps of GLV infection and host-pathogen interactions.