Herpes Simplex Virus

MORPHOLOGY:
  • Herpes viruses have a unique four-layered structure: a core containing the large, double-stranded DNA genome is enclosed by an icosapentahedral capsid which is composed of capsomers. 
  • The capsid is surrounded by an amorphous protein coat called the tegument. 
  • It is encased in a glycoprotein-bearing lipid bilayer envelope.
CLINICAL MANIFESTATION:
  • Herpes simplex viruses 1 and 2 have only about 50 percent genomic homology.
  • However, they share most other characteristics. 
  • Mucocutaneous manifestations of herpes simplex virus infection include gingivostomatitis, herpes genitalis, herpetic keratitis, and dermal whitlows.
  • A dendritic corneal ulcer is the hallmark sign of HSV infection, accompanied by stromal keratitis in more severe infection. 
  • These ulcers may begin as nondescript punctate keratopathies but quickly coalesce to form the familiar branching patterns
  • 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
  • The initial infection by herpes simplex virus is often inapparent and occurs through a break in the skin or mucous membranes, such as in the eye, throat, or genitals.
  • Latent infection often persists at the initial site despite high antibody titers. 
  • Recurrent disease can be triggered by temperature change, emotional distress, and hormonal factors.
  • Type 1 herpes simplex virus is usually, but not exclusively, associated with ocular(Follicular conjunctivitis with Decreased corneal sensations, dendritic and geographical 
  • lcers ) and oral lesions 
  • Type 2 infection is more common. In addition to mucocutaneous infections,like erythema multiformis the CNS and occasionally visceral organs can be involved.
  • Type 2 is usually, but not exclusively, associated with genital and anal lesions.
PATHOGENESIS
  • The virus replicates initially in epithelial cells, producing a characteristic vesicle on an erythematous base. 
  • It then ascends sensory nerves to the dorsal root ganglia, where, after an initial period of replication, it establishes latency. 
  • During reactivated infection, the virus spreads distally from the ganglion to initiate new cutaneous and/or mucosal lesions.
DIAGNOSIS:
MRI 
  • shows bilateral frontotemporal hyperintense lesion in herpes encephalitis
CT
  • Tcmporoparietal 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:
  • Infections with herpes simplex virus 1 and 2 and varicella-zoster virus are currently the most amenable to therapy; 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
  • Recurrent disease can be triggered by temperature change, emotional distress, and hormonal factors.
  • Acyclovir treats herpes simplex encephalitis
  • Herpes simplex contains thymidine kinase enzyme that makes it susceptible to acyclovir
  • Herpes simplex virus encephalitis shows fever, followed by headache, confusion, focal seizures and right hemiparesis,Alterations in behaviour, Olfactory hallucination
  • MRI shows bilateral frontotemporal hyperintense lesion in herpes encephalitis
  • Herpes Simplex Virus is the commonest cause of sporadic encephalitis
  • Herpes simplex 1 latent virus infection which is responsible for the pathogenesis of the achalasia 
  • Alterations in behaviour, Olfactory hallucinations,Hemiparesis are the clinical features of Herpes Simplex Encephalitis
  • In Herpes Simplex Virus infection dendritic ulcer is seen
  • Herpes simplex virus produces small white shiny non-necrotic pocks on chick embryo chorioallontoic membrane.
  • Herpes simplex virus is a Double stranded DNA
  • Erythema multiformis is caused by Herpes simplex virus
  • Herpes simplex virus causes genital ulcers
  • Most common site of infection of herpes simplex is face
  • Follicular conjunctivitis with Decreased corneal sensations, dendritic and geographical ulcers is seen in ocular herpes simplex infection
  • Mollaret meningitis is also caused by herpes simplex-2

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