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Japanese encephalitis virus in mosquito salivary glands
Abstract:
Culex tritaeniorhynchus and C. pipiens mosquitoes were infected with Japanese encephalitis virus either by intrathoracic injection or by membrane feeding. The virus maturation sites and the process of virus particle concentration in salivary gland cells were studied by electron microscopy. Occurrence of mature virions was primarily associated with intracytoplasmic viral matrices which were extraordinarily large and had a perinuclear location in C. pipiens mosquitoes. The other sign of virus replication was the proliferation of small spherical vesicles throughout the cytoplasm. It appeared that mature virions were entrapped in intracellular vacuoles and later released into the apical cavity of salivary gland cells through the fusion of these vacuoles with the apical plasma membrane. This process seemed to be associated with primary resynthesis of saliva in mosquitoes following blood feeding activity. Another type of shedding involved virus particles either singly or in mass being released directly through the apical plasma membrane. All of these events occurred only in cells of the lateral lobes of the salivary glands, which fact was confirmed by immunofluorescent staining of infected glands. The median lobe of mosquito salivary glands may have a minor or no role in the transmission of Japanese encephalitis virus.
Insights
Japanese encephalitis virus replicates in salivary gland cells of Culex mosquitoes, concentrating in viral matrices and releasing through vacuoles or direct membrane shedding. Lateral salivary gland lobes are key sites for virus concentration and potential transmission.
Area of Science:
- Virology
- Entomology
- Cell Biology
Background:
- Japanese encephalitis virus (JEV) is a significant public health concern transmitted by mosquitoes.
- Understanding the replication and dissemination mechanisms of JEV within mosquito vectors is crucial for disease control.
Purpose of the Study:
- To investigate the sites of JEV maturation and virion concentration within salivary gland cells of Culex mosquitoes.
- To elucidate the cellular processes involved in JEV release from salivary gland cells.
Main Methods:
- Infection of Culex tritaeniorhynchus and Culex pipiens mosquitoes with JEV via intrathoracic injection or membrane feeding.
- Ultrastructural analysis using electron microscopy to observe virus-cell interactions.
- Immunofluorescent staining to confirm the location of viral replication within salivary glands.
Main Results:
- Mature JEV virions were found associated with large, perinuclear intracytoplasmic viral matrices in C. pipiens.
- Virus replication was also indicated by the proliferation of cytoplasmic vesicles.
- Virions were released via intracellular vacuoles fusing with the apical plasma membrane or through direct shedding from the apical membrane.
- Viral replication and concentration were localized to the lateral lobes of the salivary glands.
Conclusions:
- The lateral lobes of mosquito salivary glands are the primary sites for JEV replication and concentration.
- JEV utilizes distinct cellular mechanisms for release from salivary gland cells.
- The median salivary gland lobe appears to play a minimal role in JEV transmission.