Human Astrovirus MLB Replication In Vitro: Persistence in Extraintestinal Cell Lines

Area of Science:

• Virology
• Cell Biology

Background:

• MLB astroviruses, identified 10 years ago, cause gastroenteritis and have been unexpectedly linked to severe meningitis, encephalitis, and respiratory syndromes.
• Establishing a cell culture system is crucial for understanding MLB astrovirus replication and pathogenesis.

Purpose of the Study:

• To develop a cell culture system supporting the replication of MLB astroviruses.
• To investigate the permissiveness of various human cell lines to MLB astrovirus infection.

Main Methods:

• Two clinical MLB astrovirus strains (gastroenteritis and neurologic) were used to infect multiple human cell lines.
• Quantitative reverse transcription-PCR (RT-qPCR), immunofluorescence assays, and electron microscopy were employed to detect and characterize viral replication.
• Interferon (IFN) expression was analyzed in infected cells.

Main Results:

• Huh-7 and A549 cell lines were found to be permissive to both MLB astrovirus genotypes.
• Serial passages led to persistent infections in Huh-7.5, Huh-7AI, and A549 cells, with high viral loads detected.
• Electron microscopy confirmed the presence of MLB astrovirus particles and capsid arrays, particularly in Huh-7.5 cells.

Conclusions:

• The developed cell culture system is the first to support MLB astrovirus propagation, facilitating further virologic studies.
• MLB astroviruses demonstrated an unknown capacity to establish persistent infections in cell culture, with IFN expression playing a role in this mechanism.
• This breakthrough enables deeper understanding of MLB astrovirus replication, pathogenesis, and potential for persistent infections in humans.