HSV: Herpes Simplex Virus
Micr. 401 – Virology Case Study #15
By: Kevin Chau
Jere Wilson
Yessenia Velazco
Case Study #15:
•A 2-year-old child with a fever for 2 days was not eating and
was crying often. On examination, the physician noted that the
mucous membranes of the mouth were covered with numerous
shallow, pale ulcerations. A few red papules and blisters were
also observed around the border of the lips. The symptoms
worsened over the next five days and then slowly resolved, with
complete healing after two weeks
•Diagnosis: Typical HSV-1 or Congenital HSV-2
HSV Background:
•Greek “herpein” – “to creep”
•Enveloped w/glycoproteins, icosahedral capsid
•ds, linear w/nicks DNA genome
•Tegument proteins – between envelope & capsid
HSV Lytic Cycle:
1)Attachment:
gB/gC: viral ligands binding host heparan sulfate low affinity receptor
gD: viral ligand binding to primary receptor directing envelope fusion at the plasma membrane
2)Penetration:
pH Independent Fusion – facilitates envelope fusion at the plasma membrane
Releases nucleocapsid into cytoplasm
Does not form a vesicle or pH-dependent endosome
Releases tegument proteins: αTIF & VHS
3)Uncoating:
•Retrograde Transport – nucleocapsid transport from cell periphery to the cell nucleus along microtubules scaffolds (axonal transport)
4)Viral Synthesis:
Immediate Early Transcription activated by αTIF
VHS (virion host shutoff) – overall mRNA degradation & inhibits host translation machinery
Circularization & amplification of genome
5)Assembly:
Rolling concatemer synthesis & assembly
6)Viral Release:
Virus buds from nuclear membrane through intermediate glycoproteins
Obtains tegument proteins in cytoplasm
Buds into a glycosylated vesicle from Golgi apparatus
Enveloped virion is released by exocytosis
HSV Latency:
•Viral reservoir in sensory
neurons: trigeminal & sacral
ganglia
•Common cold
•Fever/Allergy
•LAT gene expression increases in •Severe sunburn
response to viral stress on host cell •Physical fatigue
•Represses VHS via Histones, but •Emotional disturbance
allows minimal gene transcription
•Trauma
for reactivation
•Gastrointestinal disturbances
•Reactivation in differentiated
neural cells must require
•Menstruation
independent viral replication
•Pregnancy
machinery
HSV Immune Response:
•Antibodies are present 4-8 days
after primary infection
•Infections stimulate MHC II
pathway immune response
resulting in active B cells and
memory B cells
•Cytolytic response via MHC I
is gradually downregulated by
viral glycoprotein ICP47 binding
to TAP
•TAP facilitates antigen
processing in MHC I response
HSV Transmission:
•Direct contact of lips or genitals when sores present
•Possible transmission when sores not present (viral shedding)
•Virions present in semen, saliva, & vaginal fluids
•Autoinoculation
•Pregnancy
HSV-1 Background:
•Also referred to as: “cold sores” - not “canker sores”
•Primarily associated with oral, pharyngeal, facial, ocular, and
encephalitis infections
•Mainly transmitted by oral secretions in close non-sexual
contact (ex. touching, kissing, sharing food or utensils)
•Lesions localize anteriorally: lips, gingiva, anterior tongue, and
hard palate
HSV-2 Background:
•Primarily associated genital infections
•Mainly transmitted sexually by genital secretions
•Lesions found on: vulva, vagina, cervix, urethra, perineum,
penis, and rectum
Despite typical, clinical manifestations, both HSV-1 &
HSV-2 can cause oral-facial and genital infections.
HSV Clinical Symptoms:
•Swollen lymph glands
•Headache
•Fever
•Sore mouth/genitals
•Itching sensation
•Lower back & leg pains
– associated with genital
herpes
•Visualization: Yellowishpus, epidermal lesion
w/erythematous border
•Incubation time is 2 to 20
days after contact; symptoms
last 10-21 days
•May be less severe for certain
individuals (especially HSV-1)
•First attack causes visible
sores; asymptomatic after
primary infection (latency)
•Reactivation produces active
lesions (secondary infections)
•Examine medical/sexual
history
HSV-2 & Pregnancy:
•Vaginal tract infection associated w/ spontaneous abortion,
premature birth, and 90% congenital neonatal herpes.
•5% Transplacental infection & 5% post-partum
•Untreated neonatal herpes: 60% neonatal mortality or severe
developmental defects
HSV Diagnosis:
1) Viral isolation:
•Reserved for patients with active lesions
•Involves collecting viral fluid from vesicles by swabbing &
incubation in growth media for cell culture
•Virus can be identified by monoclonal antibodies detecting
early antigens of HSV
•Tissue culture for HSV is positive within 48 hours of
inoculation.
•Visual examination of cell culture for viral cytopathic effect
Ex. ballooning of cells and rapid cell death of entire monolayer
HSV Diagnosis:
2)Tzanck Smear:
•Provides rapid and reliable
diagnosis of an infection caused by
Herpesviridae
•Purpose of this technique is to
observe viral-induced degenerative
changes in the cells:
multinucleated giant keratinocytes
and ballooning degeneration.
•Limitation: Cannot distinguish
between type-specific herpes
infection
HSV Diagnosis:
3) Direct fluorescent antibody (DFA):
•Used to detect viral antigens.
•DFA is very specific, sensitive, fast & inexpensive method for
labeling HSV antigens with monoclonal antibody, identifying
type-specific HSV
•Immunofluorescent staining of tissue culture cells can quickly
differentiate types 1 or 2 HSV.
HSV Diagnosis:
4) Viral DNA detection w/PCR:
•Rapid detection of HSV DNA in clinical specimens with
polymerase chain reaction (PCR) techniques.
•In HSV encephalitis, PCR using cerebrospinal fluid (CSF)
provides a rapid, noninvasive diagnostic technique that is as
sensitive as brain biopsy.
•PCR can detect viral infection during asymptomatic stages
(latency)
HSV Diagnosis:
5)Serological Assays:
Enzyme-linked immunosorbent assay (ELISA):
•Fast and inexpensive assay
•ELISA recognizes the antigenic subtype differences between
glycoprotein G1 and G2
•False-positive results may occur due to the potential for crossreactivity between the two glycoprotein
Immunoblot (Western):
•Necessary for confirming positive results as it detects
antibodies across all viral proteins to determine if the infection
is caused by HSV1 or HSV2.
HSV Treatment:
There is no cure that can eradicate the virus, but
there are treatments that can modify the course of the
disease.
1) Fusion Inhibitors (Docosanol):
•An over-the-counter product approved for topical treatment
•Prevents the fusion of the viral envelope with the cell
membrane, preventing the entry of the virus into the host cell
2) Helicase-primase Inhibitors (Non-nucleoside):
•New non-nucleoside antivirals that target the helicaseprimase, which is one of the most important complex involved
in HSV DNA replication
HSV Treatment:
3) Nucleoside Antivirals:
• Acyclovir, Valacyclovir, Penciclovir: are viral agents that
target the DNA polymerase & viral replication
•Acyclovir and valacyclovir perform selective inhibition of DNA
polymerase resulting in termination of further elongation of
viral DNA
•Penciclovir, on the other hand, halts viral DNA replication by
competitive inhibition of DNA polymerase rather than chain
termination
HSV Treatment:
4) Vaccine (Herpevac):
•Herpevac is a vaccine used for HSV-2
•Studies showed 70% effectiveness for women but not for men\
5) Unproven Remedies:
• High Lysine Diet (Amino Acid)
•Topical Undecylenic acid (Castor oil derivative)
•Topical Butylated hydroxytoluene - (food preservative)
Reference:
•Bloom, D.C. Experimental investigation of herpes simplex virus latency. Clin Microbiol Rev. 1997 July; 10(3):419-443
•Brown, J.C. Uncoating the herpes simplex virus genome. J. Mol. Biol. 2007 370 (4): 633-42.
•Geraghty, R.J. Herpes simplex virus type 1 mediates fusion through a hemifusion intermediate by sequential activity of glycoproteins D, H, L, and B.
Proc. Natl. Acad. Sci. U.S.A. 2007. 104 (8): 2903-8.
•Hsia, S.C. Repressor element-1 silencing transcription factor/neuronal restrictive silencer factor (REST/NRSF) can regulate HSV-1 immediate-early
transcription via histone modification. Virol. J. 2007. 4: 56.
•Kimberlin D, Powell D, Gruber W, et al. 1996. Administration of oral acyclovir suppressive therapy after neonatal herpes simplex virus disease limited to
the skin, eyes and mouth: results of a phase I/II trial. Pediatric Infectious Diseases Journal 15:247-54.
•Kramer, Martha F. Accumulation of Viral Transcripts and DNA during Establishment of Latency by Herpes Simplex Virus. J Virol. 1998. 72:2
•Mahnaz F, Schwartz R. 2007. Human herpes simplex virus infections: Epidemiology, pathogenesis, symptomatology, diagnosis, and management.
Journal of American Academy of Dermatology 57:737-763.
•McIntosh E. 2005. Paediatric infections: prevention of transmission and disease- implications for adults. Vaccine 23:2087–2089.
•Wechsler, S.L. Fine mapping of the latency-related gene of herpes simplex virus type 1: alternative splicing produces distinct latency-related RNAs
containing open reading frames. J. Virol. 62:11
•Whitley, R.J. Herpesviruses. in: Baron's Medical Microbiology. 2008. 4th ed.
•Antiviral Drugs For Herpes Treatment
http://ezinearticles.com/?Antiviral-Drugs-For-Herpes-Treatment&id=265576
•Herpes & Cold Sores
http://www.herpes-coldsores.com
•The Tests You Take to Diagnose Genital Herpes
http://www.webmd.com/genital-herpes/guide/genital-herpes-diagnosis?src=rss_womenshealth
•Herpes Diagnosis
http://www.herpesdiagnosis.com/blood.html
•Herpes Viruses
http://pathmicro.med.sc.edu/virol/herpes.htm
•Immune Response
http://www.brown.edu/Courses/Bio_160/Projects2000/Herpes/HSV/Immune_response.html
•Dr. Edward K. Wagner’s Herpes Virus Research
http://www.dbc.uci.edu/~faculty/wagner/hsv7f.html
•Use a Prophylatic
•Get Tested
The End