Herpes Simplex Virus

Herpes Simplex Virus


MORPHOLOGY:

Herpes viruses have a unique four-layered structure: 

  • Core containing large double-stranded DNA genome 
  • Enclosed by an icosapentahedral capsid ,composed of capsomers. 
  • The capsid is surrounded by an amorphous protein coat ,tegument. 
  • It is encased in a glycoprotein-bearing lipid bilayer envelope.

PATHOGENESIS

  • Source of infection 
  • Saliva
  • Skin lesion
  • Respiratory secretion.

The initial infection

  • inapparent
  • occurs through a break in the skin or mucous membranes, such as in the eye, throat, or genitals.
  • The virus replicates initially in epithelial cells
  • Produce characteristic vesicle on an erythematous base. 
  • It then ascends sensory nerves to the dorsal root ganglia,
  • initial period of replication
  • establishes latency. 
  • During reactivated infection
  • Virus spreads distally from the ganglion
  • Initiate new cutaneous and/or mucosal lesions.
  • In clearance of virus from lesion, CD8 + T cell responses important.
HSV includes
  • HSV-1
  • HSV-2
  • HSV 1 and 2 have only about 50 percent genomic homology. 
  • However, they share most other characteristics.
  • Distinguished by 
  • restriction endonuclease analysis
  • nucleic acid hybridization (DNA sequencing)

HSV 1 

  • Cause lesion in and around mouth
  • Transmission
  • Direct contact or droplet spread
  •  Replicate
  • poorly in chick embryofibroblast cell
  • Relatively sensitive to
  • antiviral agents
  • Less neurovirulent
  • Infectivity is less temperature sensitive
  • Site of latency
  • trigeminal ganglia
  • On chick embryo CAM,
  • form smaller pock
HSV 2
  • Cause lesion around
  • genital area
  • Transmission
  • sexually
  • Replicate well
  • Resistant
  • More neurovirulent
  • More temperature sensitive
  • Sacral ganglia
  • Form larger pock 

CLINICAL MANIFESTATION:

  • Mucocutaneous manifestations
  • Face most common site
  • gingivostomatitis
  • herpes genitalis
  • herpetic keratitis
  • dermal whitlows.
  • Herpes Gladiatorum

Encephalitis

  • Herpes Simplex Virus is the commonest cause of sporadic encephalitis

Neonatal herpes simplex virus infection and herpes simplex virus encephalitis shows:

  •  fever
  • followed by headache
  • confusion
  •  focal seizures 
  • Alterations in behaviour
  • Olfactory hallucinationand right hemiparesis.
  • Mollaret meningitis is also caused by herpes simplex-2

Meningitis

  •  Mollaret’s  Meningitis

Eye Infection

  • Type 1 herpes simplex virus is usually
  • Follicular conjunctivitis 
  • Decreased corneal sensations
  • dendritic and geographical ulcer
  • Accompanied by stromal keratitis in more severe infection. 

Genital lesions 

  • Type 2 
  • Bilateral lesion
  •  women: Cervix and Urethre 
  • Males: Penis
  • Latent infection often persists at the initial site despite high antibody titers. 
  • Recurrent disease triggered by 
  • temperature change
  • emotional distress
  • hormonal factors. 

DIAGNOSIS:

MRI 

  • shows bilateral frontotemporal hyperintense lesion in herpes encephalitis

CT

  • Temporoparietal areas of low absorption, mass effect and control enhancement

EEG

  • Periodic temporal lobe spikes on a background of slow or low amplitude activity on EEG
  • Herpes simplex virus produces small white shiny non-necrotic pocks on chick embryo chorioallontoic membrane.

TREATMENT:

  • Acyclovir is effective for Herpes simplex (thymidine kinase enzyme)
  • Valaciclovir and famciclovir are all licensed therapeutics.
  • Ganciclovir is used to treat cytomegalovirus retinitis.
  •  B virus appears to respond to either of these drugs. 
  • Acyclovir treats herpes simplex encephalitis 
Exam Question

MORPHOLOGY:

  • Core containing large double-stranded DNA genome 

PATHOGENESIS

  • The initial infection
  • inapparent
  • occurs through a break in the skin or mucous membranes, such as in the eye, throat, or genitals.
HSV includes
  • HSV-1
  • HSV-2
  • HSV 1 and 2 have only about 50 percent genomic homology. 
  • However, they share most other characteristics. 
  • HSV 1 On chick embryo CAM,form smaller pock
  • HSV 2 Form larger pock 

CLINICAL MANIFESTATION:

  • Mucocutaneous manifestations
  • Face most common site
  • gingivostomatitis
  • herpes genitalis
  • herpetic keratitis
  • dermal whitlows.
  • Herpes Gladiatorum

Encephalitis

  • Herpes Simplex Virus is the commonest cause of sporadic encephalitis

Neonatal herpes simplex virus infection and herpes simplex virus encephalitis shows:

  •  fever
  • followed by headache
  • confusion
  •  focal seizures 
  • Alterations in behaviour
  • Olfactory hallucinationand right hemiparesis.
  • Mollaret meningitis is also caused by herpes simplex-2

Meningitis

  •  Mollaret’s  Meningitis

Eye Infection

  • Type 1 herpes simplex virus is usually
  • Follicular conjunctivitis 
  • Decreased corneal sensations
  • dendritic and geographical ulcer
  • Accompanied by stromal keratitis in more severe infection. 

Genital lesions 

  • Type 2 
  • Bilateral lesion
  •  women: Cervix and Urethre 
  • Males: Penis
  • Latent infection often persists at the initial site despite high antibody titers. 
  • Recurrent disease triggered by 
  • temperature change
  • emotional distress
  • hormonal factors.
 DIAGNOSIS:

MRI 

  • shows bilateral frontotemporal hyperintense lesion in herpes encephalitist

EEGmembrane.

  • Periodic temporal lobe spikes on a background of slow or low amplitude activity on EEG
  • Herpes simplex virus produces small white shiny non-necrotic pocks on chick embryo chorioallontoic 

TREATMENT:

  • Acyclovir is effective for Herpes simplex (thymidine kinase enzyme)
  • Valaciclovir and famciclovir are all licensed therapeutics.
  • Acyclovir treats herpes simplex encephalitis 
Don’t Forget to Solve all the previous Year Question asked on Herpes Simplex Virus

This site uses Akismet to reduce spam. Learn how your comment data is processed.

%d bloggers like this:
Malcare WordPress Security