Herpes Simplex Virus and Epstein-Barr Virus

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Herpes Simplex Virus and Epstein-Barr Virus

• By
• Sheryl Fleisch
• and
• Eric Warren

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Herpes Simplex Virus (HSV)and Epstein-Barr Virus
(EBV)

• Members of the Herpes Virus Family which are some
  of the most common human viruses

HSV
EBV
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Herpes Simplex Virus
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How was the HSV Discovered

• HSV is an ancient disease with descriptions of
  orolabial herpes appearing in records from the
  fifth century BCE.
• In the 1736 Astruc (physician to King of France)
  identified Herpes as a cause of genital
  infection.
• Over the next 50 years many different strains of
  herpes were discovered.
• In 1893 intimate human-to-human transmission was
  identified.
• In the 1940s neonatal HSV infection was
  described and finally identified in 1968.

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Types of HSV

• The Type 1 virus causes cold sores. Most people
  get Type 1 infections during infancy or
  childhood.

• The Type 2 virus causes genital sores. Most
  people get Type 2 infections following sexual
  contact with an infected person.

Both types can be differentiated by biologic,
biochemical and antigenic properties
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HSV Viral Structure

• Composed of a dsDNA (152kbp) nucleoprotein core
• Core is surrounded by an icosahedral protein
  capsid
• 100nm Capsid is enclosed in an outer envelope
  consisting of at least 8 glycoproteins.
• Envelope spikes 8 nm long
• The virus requires a moist environment for
  survival.

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From Dr. Edward K. Wagner at http//darwin.bio.uc
i.edu/faculty/wagner/movieindex.html
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Complications

• Meningitis-- infection of the sheaths and
  membranes (meninges) covering the brain and the
  spinal cord.
• Encephalitis-- acute inflammation of the brain,
  commonly caused by a viral infection by insect
  bites or food and drink
• Eczema herpetiform-- widespread herpes across the
  skin)
• Keratoconjunctivitis-- Infection of the eye
• Prolonged, severe infection in immunosuppressed
  individuals
• Pneumonia
• Infection of the trachea
• Keratitis-- Corneal infection, irritations, and
  inflammations

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HSV Hosts
Humans,
simians,
cattle,
cats
and chickens.
Of these, only herpes virus simiae is harmful to
us.
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From Dr. Edward K. Wagner at http//darwin.bio.uc
i.edu/faculty/wagner/movieindex.html
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Modes of Replication

• It appears that HSV replicates in sensory neurons
  after primary and/or secondary infection.

• The protein vhs (virion host shut off) causes
  rapid destabilization of host RNAs and is
  expressed by the virus.

• Virus produces 5 proteins that promote next set
  of proteins to be made

• Viral replication now ensues by circular dsDNA
  replication into capsid (Performed by 7 viral
  proteins)

• The linear HSV is then packaged in the capsid.

http//www.brown.edu/Courses/Bio_160/Projects2000/
Herpes/HSV/Mode_of_infection.html
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Modes of Replication

• Several viral structural proteins are then made.

• Encapsulation of the HSV capsids occur and they
  accumulate between the inner and outer nuclear
  membranes.

• The virions enter branched tubular structures and
  appear in transport vesicles.

• Transport vesicles fuse with the plasma membrane,
  releasing thousands of virions to the
  extracellular space causing secondary infection.

http//www.brown.edu/Courses/Bio_160/Projects2000/
Herpes/HSV/Mode_of_infection.html
13
From Dr. Edward K. Wagner at http//darwin.bio.uc
i.edu/faculty/wagner/movieindex.html
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Modes of Transmission
Even though most skin on our bodies is too thick
for the virus to penetrate, it can penetrate
areas with mucous membranes such as the genitals,
the mouth, the esophagus, the trachea, and even
onto broken areas of skin anywhere.
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Virus Latency
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Virus Latency

• 40 million people in the U.S. have latent HSV and
  may experience reactivation.

• HSV is transmitted through the body on nerves or
  synapses to and from mucosal tissues

• Vaccines and antiviral medicines cant attack
  latent virus

• Once infected, a person is infected for life.

• Latency in mucosal surfaces is effective way to
  transmit because of common mucosal contact

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From Dr. Edward K. Wagner at http//darwin.bio.uc
i.edu/faculty/wagner/movieindex.html
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Immunology
The constant battle between our body and invaders
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Immunology
The constant battle between our body and invaders

• T cells can prevent HSV-1 reactivation from
  latency in sensory neurons with the help of gamma
  interferon

• We can produce two different antibodies, one
  against each type of HSV.

• When both HSV 1 antibodies and HSV 2 antibodies
  are present, they can crosslink with one another
  and neither Antibody will be effective.

• The HSV protein ICP47 blocks MHC Class 1 which
  tells T cells whether there is a foreign invader.
  Since it can not longer do this, ICP47 allows
  enough time for HSV to regenerate and become
  active.

• HSV proteins inhibit cellular DNA synthesis and
  the virus uses its own primase and other
  replication machinery to replicate its DNA.

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Symptoms

• Mouth sores
• Genital lesions (male) -- may be preceded by
  burning or tingling sensation
• Genital lesions (female) -- may be preceded by
  burning or tingling sensation
• Blisters and/or ulcers -- most frequent on the
  mouth, lips and gums or genitalia
• Fever blisters
• Fever -- may be present especially during the
  first episode
• Enlargement of lymph nodes in the neck or groin

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Diagnosis of HSV

• The appearance of HSV is often so typical that no
  testing is needed to confirm an infection, only a
  physical.
• The genital herpes sores may not be visible to
  the naked eye so a doctor may have to do a swab
  from the infected skin (culture) and send it to
  the lab for analysis.
• A viral PCR can be run on a swab of infected
  tissue.
• A blood test, can show if a person has been
  infected with HSV but cannot distinguish between
  type I and II.
• There are also newer blood tests that can tell
  whether a person has been infected with HSV 1
  and/or 2 by the patients immune response to the
  herpes infection.

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Treatment of HSV

• There is no vaccine that prevents this disease
  from occurring.
• Oral anti-viral medications such as acyclovir
  (Zovirax), famciclovir (Famvir), or valacyclovir
  (Valtrex) have been developed to effectively
  treat herpes infections.
• Acyclovir
• Famvir
• Valacyclovir

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Treatment of HSV

• The combined effects of acyclovir and human
  interferon-alpha as drug therapy are being
  investigated now.
• Hsv 1 protective surface glycoprotein gD
  expressed in CHOs and protected mice
• To keep from spreading the infection
• Keep the infected area clean and dry to prevent
  other infections from developing.
• Try and avoid touching the sores.
• Wash your hands after contact with the sores.
• Avoid sexual contact from the time you first feel
  any symptoms until the sores are completely
  healed.

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New Anti-viral Vaccines

• Several studies have evaluated the utility of HSV
  vaccines to prevent genital HSV-2 infections.
  These vaccines have included glycoprotein
  antigens combined with various adjuvants. These
  trials have been fairly disappointing, however,
  and have not demonstrated efficacy outside of a
  limited subset of patients.
• Topical microbicides, preparations containing
  microbe-killing compounds, are also in various
  stages of development and testing. These include
  gels, creams, and lotions.

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Summary

• About 50 percent to 80 percent of the adult
  population in the United States has oral herpes.

• HSV II affects anywhere between 5 and 20
  million people, or up to 20 percent of all
  sexually active adults in the United States.

• Between 200,000 and 500,000 people are infected
  with genital herpes each year

• Over 80 of all genital herpes is transmitted
  when there isn't anything on the skin and no
  symptoms.

• The average number of outbreaks per year is
  four to five, and the first outbreak may be the
  most extreme outbreak a person will have.

• Between 1 in 1,000 and 1 in 5,000 infants are
  born with HSV. About 80 of these infections are
  acquired during the birth process itself.

• Without treatment, the infant mortality rate
  is 80. With antiviral medication, the mortality
  rate is still 15-20, with 40-55 of the
  survivors having permanent nerve damage

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Epstein-Barr Virus
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Discovery of EBV and Important Dates

• 1958- Burkitt's lymphoma described in the malaria
  belt of east Africa
• 1964- Epstein and Barr discover EBV through
  electron microscopy of cells cultured from
  Burkitt's lymphoma tissue
• 1968- EBV demonstrated as the etiological agent
  of infectious mononucleosis

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EBV Viral Structure

• A core containing a linear, dsDNA molecule of
  about 175 kbp.
• An icosahedral capsid, approximately 100-110 nm
  in diameter, containing 162 capsomeres with a
  hole running down the long axis.
• An amorphous, sometimes asymmetric material that
  surrounds the capsid, designated as the tegument
• An envelope containing viral glycoprotein spikes
  on its surface.

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Primary Infection Diseases

• Infectious Mononucleosis (glandular fever) -
  fever, lymphadenopathy, and pharyngitis

• Chronic active EBV infection - severe illness of
  more than six months, histologic evidence of
  organ disease, and demonstration of EBV antigens
  or EBV DNA in tissue (mimics chronic fatigue
  syndrome)

• X-Linked Lymphoproliferative Disease - inherited
  disease of males, absence of functional SAP gene
  impairs the normal interaction of T and B cells
  resulting in unregulated growth of EBV-infected B
  cells.

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Diseases resulting from EBV in reduced immunity
patients

• PTLD (Post-transplant lymphoproliferative
  disease) -a tumor often found in organ transplant
  patients
• Oral Hairy Leukoplakia
• Nonmalignant hyperplastic lesion of epithelial
  cells

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Cancers Associated with EBV

• Nasopharyngeal Carcinoma
• Southern China, Northern Africa, and Alaskan
  Eskimos
• Elevated titers of IgA antibody to EBV structural
  proteins
• Burkitt's Lymphoma
• Found in equitorial Africa and associated with
  malaria which doesnt allow T-cells to control
  proliferation of EBV-infected B cells
• Tumors present in jaw
• Hodgkin's Disease
• EBV DNA detected in tumors
• Lymphoproliferative Disease
• Impaired T-cell immunity and cannot control
  proliferation of EBV-infected B cells

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Site of Infection

• Infection of Epithelial Cells by EBV in vitro
• Active replication, production of virus, lysis of
  cell
• Infection of B cells by EBV in vitro
• Latent infection, with immortalization
  (proliferate indefinitely) of the virus-infected
  B cells
• Linear EBV genome becomes circular, forming an
  episome, and the genome usually remains latent in
  these B cells
• Viral replication is spontaneously activated in
  only a small percentage of latently infected B
  cells.
• Signal transduction pathways can reactivate EBV
  from the latent state

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Replication

• EBV replicates in the epithelial cells of the
  mouth, tongue, salivary glands, and oral cavity
  (few symptoms may be present, but a person can
  still be infectious)
• EBV infects B cells in the lymph nodes of the
  oral cavity
• Once inside B cells, EBV expresses proteins
• Nucleus EBNA (Epstein-Barr Virus Nuclear
  Antigens)
• Plasma Membrane LMP (Latent Membrane Proteins)
• Expression of these proteins stimulates B cell
  replication in lymph nodes producing clones
• Since many B cells are infected, polyclonal
  B-cell growth occurs which allows the disease to
  begin a long time after initial exposure to EBV

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Infection and Replication
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Modes of Transmission

• Intimate Contact
• kissing, sharing food, coughing

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Immune System to the Rescue! (or not)

• Yay Immune System
• Epithelial cells and polyclonal B cells express
  the viral-encoded LMP glycoprotein in their
  plasma membranes
• Killer T cells recognize the LMP glycoprotein and
  kill the EBV-infected cells
• While T cells are mounting an attack on B cells,
  the immune response of a person is abnormal
  producing atypical T cells and antibodies that
  can confirm diagnosis of infectious mononucleosis

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Immune System to the Rescue! (or not)

• Boo Immune System
• The ability of EBV to persist, despite potent
  immune effector responses against it, indicates
  that the virus has evolved strategies to elude
  the immune system.

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Symptoms

• The classic triad of mononucleosis is
• Inflammation of the pharynx (or tonsils) --
  usually the severest symptom
• Fever (higher in the evening)
• Lymphadenopathy (usually in the neck, groin or
  under the arms)

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Symptoms

• Other symptoms include
• Fatigue and malaise
• Rash (associated with the use of ampicillin)
• Headache
• Muscle aches
• Abdominal pain
• Occasional jaundice
• Enlargement of the spleen and liver

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Diagnosis of EBV

• Clinical diagnosis- Classic triad of symptoms
  lasting 1-4 weeks
• Serologic test- Shows elevate white blood cell
  count, an increased number of lymphocytes,
  greater than 10 atypical lymphocytes, and a
  positive reaction to a mono spot test
• Someone who appears to have infectious mono, a
  positive Paul-Bunnell heterophile antibody test
  can be done
• Serologic testing is the method of choice for
  primary infection
• EBV specific lab tests can be performed, testing
  patient for EBV antibodies.

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Complications and Symptom Alleviation

• A ruptured spleen (rare) Splenectomy
• Hemolytic anemia (steroid usage)
• Airway obstruction due to enlarged tonsils
  (steroid usage)
• Decreased platelet production, hypersplenism, or
  severe anemia (transfusions)

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Treatment of EBV

• Infectious Mononucleosis
• No specific therapy just nonaspirins and rest
• Oral Hairy Leukoplakia
• Acyclovir inhibits EBV replication
• EBV Lymphoproliferative Disease
• reduction in the dose of immunosuppressive
  medication
• Surgical removal or irradiation of localized
  lymphoproliferative lesions

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Prevention and Vaccines

• EBV lymphoproliferative disease
• infusion of B-celldepleted marrow to offset the
  proliferation of donor B cells
• Removal of donor B cells along with T cells
• Vaccination studies underway but no vaccine found
  so far

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Summary

• As many as 95 of adults between 35 and 40 years
  old have been infected.
• Many children become infected with EBV but do not
  usually show symptoms.
• When EBV occurs during adulthood it causes
  infectious mononucleosis 35-50 of the time.
• Causes lifelong, persistent infections - majority
  are benign

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References

• Levine, Arnold. Viruses. Scientific American
  Library. NY, 1992.
• http//www.emedicine.com/ped/topic705.htm
• http//www.science.org.au/nova/026/026key.htm
• http//www.uq.edu.au/vdu/EBV.htm
• http//www.cdc.gov/ncidod/diseases/ebv.htm
• Roizman, Bernard. Infectious Diseases in an Age
  of Change. National Academy Press. Washington
  D.C., 1995.
• http//www.niaid.nih.gov/factsheets/stdherp.htm
• http//www.aad.org/pamphlets/herpes.html
• http//www.ashastd.org/hrc/educate.html