Three-dimensional structure of herpes simplex virus from cryo-electron tomography

Area of Science:

• Virology
• Structural Biology
• Molecular Biology

Background:

• Herpes simplex virus (HSV) is a complex DNA virus with a nucleocapsid, tegument, and envelope.
• The tegument and envelope are crucial for viral infectivity and exhibit pleomorphic characteristics.
• Understanding the precise structure of these components is vital for deciphering viral mechanisms.

Purpose of the Study:

• To visualize and characterize the three-dimensional structure of the herpes simplex virus tegument and envelope.
• To investigate the spatial relationship between the capsid, tegument, and envelope.
• To analyze the distribution and characteristics of glycoprotein spikes on the viral envelope.

Main Methods:

• Cryo-electron tomography was employed to image isolated herpes simplex virus virions.
• Detailed analysis of tomograms was performed to resolve the tegument substructure and envelope morphology.
• Quantification of glycoprotein spikes and assessment of their distribution patterns were conducted.

Main Results:

• The tegument forms an asymmetric cap around the nucleocapsid, with varying distances to the envelope.
• Tegument substructure appears particulate, with evidence of actin-like filaments.
• The viral envelope displays 600-750 glycoprotein spikes with heterogeneous lengths, spacing, and emergence angles.
• Glycoprotein spike distribution is nonrandom, suggesting potential functional clustering.

Conclusions:

• The asymmetric tegument structure is a key feature of herpes simplex virus virions.
• The particulate nature of the tegument and the clustered distribution of envelope spikes hint at specific functional roles.
• These findings provide a detailed structural basis for understanding herpes simplex virus infectivity and assembly.