Herpes Simplex Virus: Introduction, Properties, Pathogenecity, Lab Diagno

Herpes Simplex Virus: Introduction, Properties, Pathogenecity, Lab Diagnosis , Treatment and Prevention

Herpes Simplex Virus (HSV) Introduction

Human infections with Herpes simplex virus (HSV) were first documented in ancient Greece. Greek scholars, in particular, Hippocrates used the word “herpes’,’ meaning creeping or crawling, to describe spreading lesions. The classification that is now in use came into being at the end of the eighteenth century, and even though it did. Previously, the vesicular nature of the lesions associated with herpes infections was well characterized, and it was not until 1893 that Vidal specifically recognized the person-to-person transmission of HSV infections.

Family: Herpesviridae (DNA A Virus)

(Greek:herpein – to creep)

Properties of Herpes Simple Virus

Double-stranded DNA
Roughly spherical with icosahedral capsid symmetry with 162 capsomers.
Size: 120 -150 nm in diameter
Contains loose lipid envelop ( lipid from the host)
Between the envelope and capsid is an amorphous structure.
When the envelope breaks and collapses away from the capsid, the virion has a typical ”fried egg” appearance with the capsid as the yolk and the envelope as white.
Heat labile, sensitive to ether and bile salt.
Isolation by insulating into

embryonated egg
tissues culture

The family, Herpesviridae contains 5 genera and they are-

Herpes simplex Virus (HSV)
Herpes Virus simiae ( Monkey Virus)
Varicella-zoster
Human Cytomegalovirus ( Beta Herpes)
Epstein – Barr Virus ( Gamma Herpes Virus)

HSV are of two types -HSV -1 AND HSV -2 whose genome shares 50-70 % homology.

HSV-1 (usually associated with non-genital infection i.e., above the belt)

Transmitted through direct contact or droplet infection from cases or carriers.
Usually cause infection of the oral cavity, eyes, and occasionally respiratory tract.

Infections include

Gingivostomatitis ( ulceration of gums and lining of the mucus membrane of the month)
Kerato conjunctivitis ( Denderic ulcer in cornea and Conjunctive)
Occasionally encephalitis
Herpes infection in burned and eczematous ( inflammatory process in the epidermis) may cause blisters.
Occasionally respiratory tract infection

HSV -2 ( usually associated with genital infection i.e., below the belt)

Transmitted usually through sexual contact.
Neonatal infection through mother’s birth canal and/or transplacental passage ( could be both HSV -1 and 2)

Infection include

Genital infection: causes painful ulceration in genital and urogenital organs.

Such as :

Penis and urethra in males.

Cervix, vulva, vagina perineum in female

Infants born of mothers with genital Herpes become seriously ill with jaundice, splenomegaly, and hepatomegaly leading to develop congenital malformation.
Thought to be associated with cervical and valvular carcinoma

The cycle of Herpes Virus infection Skin to Axon to Skin ( Centrifugal cycle)

Penetration of virus into the skin

Local replication: The virus enters into cutaneous neurons centripetal migration in the axon through uncoated nucleocapsids and synthesis of the infection virus particle passes to the skin.

Laboratory Diagnosis of Herpes Simple Virus

Collection of specimen/s:

Herpetic sore
Skin scraping
Pustule fluid

Note: Immediate transfer to the lab or collection in Viral transport medium in immediate at -70°C is important.

Direct Microscope examination

Direct demonstration of antigen

Immunofluorescence test
Electron microscopy
Staining of scraped materials with Toluidine blue

Note the following

Multinuclear giant cell
Intranuclear bodies
Giant cell shows homogeneously stained chromatin ( ground glass appearance)
DNA/DNA hybridization
Polymerase Chain Reaction (PCR)

Culture on the chorioallantoic membrane of the embryonated egg where tiny white uniform pocks will be seen.

Tissue culture

Human embryonic kidney cell lines
Rabbit kidney cell lines
Human embryonic tissue cell line

Serological test in patients serum

Complement fixation test
Neutralization test

Treatment of Herpesvirus Diseases

Acyclovir, a synthetic acyclic purine nucleoside analog, has become the standard therapy for HSV infections. It’s the most common prescripted and clinically effective antiviral drug available to date. Valacyclovir (converted to acyclovir) and famciclovir (converted to penciclovir) have recently been licensed and have greater oral bioavailability than acyclovir and penciclovir.

Prevention

Increased awareness of the increasing incidence and association of genital herpes and neonatal herpes. Between infection with HSV and increased risk of HIV infection, every effort should be made to prevent infections with HSV-2. Until the vaccine has been shown to be effective, educational efforts must be made. The use of condoms should be encouraged. Individuals are known to have been infected. In particular, education should be provided on the risks of transmission of infection to seronegative female sexual partners. It’s pregnant. In addition, the incidence of neonatal HSV infection can be reduced by performing a cesarean section if there are lesions. At delivery, they are present in the mother. Vaccination remains the ideal method for the prevention of viral infection, but the use of vaccination to prevent infections with HSV introduces a unique problem due to recurrence in the presence of humoral and cell-mediated immunity. Adolescents and adults at greatest risk.

Key Notes on Herpesvirus

Herpes simplex is a virus infection caused by the herpes simplex virus.
To distinguish between HSV -1 and HSV -2, DNA/DNA hybridization is done.
HSV-2 is also called genital herpes simplex virus because of causing genital infection while HSV-1 called oral HSV due to causing oral infection.
An estimated 536 million people worldwide (16 percent of the population) have been infected with HSV-2 since 2003 with higher rates among women and women in the developing world.

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