Herpes simplex virus 1 (HSV-1)- An Overview


Herpes simplex virus 1 (HSV-1) is a member of the Alphaherpesvirinae subfamily of the Herpesviridae family, a group of viruses that cause infections in humans and animals. HSV-1 is mainly responsible for oral and ocular infections, such as cold sores and keratitis, but can also cause genital herpes and encephalitis in some cases.

HSV-1 has a complex structure composed of four main components:

  • A linear double-stranded DNA genome that encodes more than 100 genes and is about 152 kilobase pairs long. The genome is divided into two unique regions, long (UL) and short (US), that are flanked by inverted repeats. The genome also has terminal repeats at both ends.
  • An icosahedral protein capsid that surrounds the genome and consists of 162 capsomeres, each made of six or five copies of a major capsid protein. The capsid also contains minor proteins that are involved in DNA packaging, maturation, and interaction with the tegument. The capsid has a diameter of about 100 nanometers.
  • A tegument layer that fills the space between the capsid and the envelope. The tegument contains various viral proteins that have functions in viral replication, transcription, immune evasion, and virion assembly. Some of these proteins are VP16, which activates viral gene expression; VHS, which shuts off host protein synthesis; and UL41, which degrades host mRNA.
  • An envelope that is derived from the host cell membrane and contains viral glycoproteins that mediate attachment and entry into host cells. HSV-1 encodes at least 11 glycoproteins, such as gB, gC, gD, and gH/gL, that have roles in binding to specific receptors, fusion with the cell membrane, structural stability, and immune escape. The envelope also has spikes of about 8 nanometers long that project from its surface.