Reason for choosing Epstein Barr virus as topic for research

–          Kissing Disease

–          Not many know that kissing can be a mode of transmission for a particular virus

Why is EBV known as Kissing Disease?

-Its mode of transmission is through secretion (saliva)

History of EBV

  • incidence of tumour that affected African children was presented as a report by a surgeon
  • climate may have affected the incidence
  • 3 researchers knew about this and started to look for possible virus that cause this tumour
  • This tumour caused a disease better known as Burkitt’s lymphoma
  • tests were carried out and with the use of electron microscope(physical method of studying virus), they were able to identity Epstein-Barr virus which was then an unknown member of the Herpes family.

http://www.sciencedaily.com/releases/2005/07/050725065240.htm

We can classify EBV according to 3 viral classification schemes

  • Balitmore
  • ICTV
  • Lwoff

According to Baltimore’s classification of virus, EBV is under

  • CLASS I [ double stranded(ds) DNA]

3 subfamilies for Herpesviridae

alpha

HSV(Herpes Simplex Virus which cause cold sores)

VZV(Varicella Zoster Virus which induces chicken pox)

beta

Cytomegalovirus(megalo=enlargement, cyto=cell). The cell enlarges making the function disrupted.

gamma

Which family is Epstein Bar Virus found?

Family: Herpesviridae(do not confuse it with Hepadnaviridae!)

Subfamily: Gammaherpes

According to Lwoff’s classification, Herpesviridae is  enveloped, has DNA as nucleic acid, and has a icosahedral capsid.

Between the capsid and envelope is the tegument. It consists of viral enzymes, some of which are needed to take control of the cell’s chemical processes and are responsible for virion production, some of which defend against the host cell’s immediate responses.

Pathogenesis of EBV

–          Virus initially infects oropharyngeal epithelial cells (where it replicates efficiently)

–          The virus then infects B cells (human B lymphocytes), as they pass through the oropharynx and this leads to latent viral infection in B cells.

General viral replication cycle involves

  • attachment
  • penetration(entry)
  • uncoating
  • replication & gene expression
  • maturation
  • release

ATTACHMENT & PENETRATION

a virus particle lands on a cell and attaches with cell surface proteins

Direct pentration(aka FUSION)  is only applicable for ENVELOPED virus. Its viral envelope then fuses with the plasma membrane of the cell and the viral capsid(viral genome and tegument proteins) enter the cytoplasm.

*what are tegument proteins?

Teguments are generally in enveloped viruses (Herpes) which have nucleocapsids and aid in viral DNA replication

REPLICATION & GENE EXPRESSION

Remember that the “method” in which virus replicates depends on the nature of its genetic material(based on the 7 classes of Balitmore’s classification. For EBV, it’s Class I ds DNA)

Replication occurs in the nucleus(except for Poxviridae). Look at the diagram and note that the big circle is the nucleus, where replication and 2 phases of gene expression take place.

Principles of molecular biology.

MATURATION

The protein capsid is assembled.

RELEASE

For enveloped EBV, the release of virion is through budding. Enveloped virus acquire their lipid membrane as the virus buds out of cell through the cell membrane or into an intracellular vesicle prior to subsequent release.

Signs & Symptoms of EBV

  • Fever
  • Pharyngitis(inflammation of the pharynx)
  • Enlarged lymph nodes
  • Jaundice(yellow skin or yellowing of membranes)
  • Skin rash
  • Eye swelling

According to stages of diseases, if typical signs & symptoms like lymphadenopathy, pharyngitis and fever occur simultaneously and last for 1-4 weeks, you can be diagnosed to have an EBV infection.

How do we confirm if a person has contracted Epstein Barr virus?

Blood tests

  • increased WBC
  • increased lymphocytes

Increased WBC is present as the body’s immune system is activated to fight against the infection.

Laboratory tests

  • It is usually diagnosed by the presence of antibody reaction to the virus.
  • differentiates whether person is susceptibile to EBV infection, has primary infection, past infection, reactivated infection or chronic infection.

A person who has EBV in him/her may be symptomatic(have symptoms) or asymptomatic (no symptoms).

A asymptomatic person is known as a carrier.

In the presence of antibodies(Ab) to EBNA, antibodies are increased and this can mean  reactivation.

When an early antigen test is carried out, the presence of Ab to EBNA does not confirm that a patient’s medical condition is caused by EBV.

Asymptomatic “healthy” people can have Ab to the EBV antigen for years after their first  EBV.  Many times reactivation occurs subclinically(before the symptoms develop).

Chronic active EBV infection is rarely  found in patients who have been ill(showing symptoms) for more than 4 months. If illness last for more than 6 months, other possible causes should be investigated.

Incidence of EBV

According to local statistics from MOH Weekly Epidemiological Bulletin of Infectious Diseases, there were no reported cases of EBV.

However, in US, statistics are different.

Among the 95% infected, there can be young adults or adolescents who can develop infectious mononucleosis(glandular fever).

Can they completely recover with no recurrence of symptoms?

NO. Latent infection means the virus remains “resting”(dormant)  in the once infected person for life and it can never be cleared.

Latency of EBV can occur …

Treatment of EBV infection

Rest and fluids intake are recommended for cases of mononucleosis(most EBV infection are mononucleosis).

Do you think antibiotics can treat EBV?

NO. Antibiotics can only treat bacterial infections.

One complication of EBV infection is sore throat that can attract the Streptoccocal infection(bacterial) to set in.Hence, antibiotics like Penicillin can be prescribed.