Early Entry Events in Echovirus 30 Infection

Area of Science:

• Virology
• Cell Biology
• Molecular Biology

Background:

• Echovirus 30 (E30) is a significant cause of viral meningitis in children and adults, responsible for global outbreaks.
• Despite its prevalence, the precise mechanisms of E30 cell entry and replication remain largely uncharacterized.
• Understanding E30's infectious pathway is crucial for developing targeted therapeutic strategies.

Purpose of the Study:

• To elucidate the early entry and replication events of Echovirus 30 (E30) in human RD cells.
• To identify the specific cellular receptors and pathways utilized by E30 during infection.
• To compare E30's entry mechanism with other known enteroviruses.

Main Methods:

• Generation of Echovirus 30 strain Bastianni (E30B) from an infectious cDNA clone.
• Infection assays in human RD cells using E30B, assessing the roles of Fc echovirus receptor (FcRn), CAR, and DAF.
• Pharmacological inhibition of cellular pathways (Rac1, cholesterol, macropinocytosis, clathrin-mediated endocytosis) and analysis of viral replication intermediates and capsid production.
• Colocalization studies with early endosomes and assessment of Rab5 expression effects on infection.

Main Results:

• E30B infection requires FcRn but not CAR; interaction with DAF was observed but not essential for entry.
• Viral RNA replication initiated between 2-3 hours post-infection, and capsid production began 4-5 hours post-infection.
• Infection was inhibited by drugs targeting Rac1 and cholesterol, suggesting a macropinocytic entry pathway, distinct from clathrin-mediated endocytosis.
• E30B colocalized with early endosomes, and Rab5 expression enhanced infection, indicating partial overlap with classical early endosomes.

Conclusions:

• Echovirus 30 utilizes a unique entry pathway involving FcRn and macropinocytosis, leading to uncoating within early endosomes.
• E30 does not rely on acidification for entry and bypasses the clathrin-mediated endocytosis pathway.
• The findings contribute to defining a conserved 'enterovirus entry pathway' within the Enterovirus B species.