Enveloped DNA Viruses

As my group member had mentioned about envelope viruses. So let me tell you more about it.
There are two groups of enveloped DNA Viruses. Below are some interesting information about it.

Herpesviridae
Epstein-Barr virus, frequently referred to as EBV, is a member of the herpesvirus family with Linear ds DNA and three origin of replication.One of the most common human viruses. The virus occurs worldwide, and most people become infected with EBV sometime during their lives. In the United States, as many as 95% of adults between 35 and 40 years of age have been infected. Infants become susceptible to EBV as soon as maternal antibody protection (present at birth) disappears. Many children become infected with EBV, and these infections usually cause no symptoms or are indistinguishable from the other mild, brief illnesses of childhood.

The Epstein-Barr virus appears capable of infecting only two major cell types: the outer (epithelial) cells of the salivary gland, and white blood cells known as B lymphocytes (B-cells). Infection with the Epstein-Barr virus develops first in the salivary gland. Large amounts of the virus are released in the saliva, enabling it to spread from one person to another.
Infection of B-cells with the virus causes them to proliferate. This proliferation is controlled by the immune system; if the correct immune response does not develop, individuals are at risk of developing a form of cancer. It is thought to be responsible for a number of diseases in addition to glandular fever (otherwise known as infectious mononucleosis) and Burkitt’s lymphoma.

A late event in a very few carriers of this virus is the emergence of Burkitt's lymphoma and nasopharyngeal carcinoma, two rare cancers
Most individuals exposed to people with infectious mononucleosis have previously been infected with EBV and are not at risk for infectious mononucleosis. In addition, transmission of EBV requires intimate contact with the saliva (found in the mouth) of an infected person. Transmission of this virus through the air or blood does not normally occur. The incubation period, or the time from infection to appearance of symptoms, ranges from 4 to 6 weeks. Persons with infectious mononucleosis may be able to spread the infection to others for a period of weeks. However, no special precautions or isolation procedures are recommended, since the virus is also found frequently in the saliva of healthy people. In fact, many healthy people can carry and spread the virus intermittently for life. These people are usually the primary reservoir for person-to-person transmission. For this reason, transmission of the virus is almost impossible to prevent.

Symptoms of infectious mononucleosis:
Fever, sore throat, and swollen lymph glands. Sometimes, a swollen spleen or liver involvement may develop. Heart problems or involvement of the central nervous system occurs only rarely, and infectious mononucleosis is almost never fatal. There are no known associations between active EBV infection and problems during pregnancy, such as miscarriages or birth defects. Although the symptoms of infectious mononucleosis usually resolve in 1 or 2 months, EBV remains dormant or latent in a few cells in the throat and blood for the rest of the person's life. Periodically, the virus can reactivate and is commonly found in the saliva of infected persons. This reactivation usually occurs without symptoms of illness. EBV also establishes a lifelong dormant infection in some cells of the body's immune system.

Susceptibility
If antibodies to the viral capsid antigen are not detected, the patient is susceptible to EBV infection.

Primary Infection
Primary EBV infection is indicated if IgM antibody to the viral capsid antigen is present and antibody to EBV nuclear antigen, or EBNA, is absent. A rising or high IgG antibody to the viral capsid antigen and negative antibody to EBNA after at least 4 weeks of illness is also strongly suggestive of primary infection. In addition, 80% of patients with active EBV infection produce antibody to early antigen.

Past Infection
If antibodies to both the viral capsid antigen and EBNA are present, then past infection (from 4 to 6 months to years earlier) is indicated. Since 95% of adults have been infected with EBV, most adults will show antibodies to EBV from infection years earlier. High or elevated antibody levels may be present for years and are not diagnostic of recent infection.

Reactivation
In the presence of antibodies to EBNA, an elevation of antibodies to early antigen suggests reactivation. However, when EBV antibody to the early antigen test is present, this result does not automatically indicate that a patient's current medical condition is caused by EBV. A number of healthy people with no symptoms have antibodies to the EBV early antigen for years after their initial EBV infection. Many times reactivation occurs subclinically.

Chronic EBV Infection
Reliable laboratory evidence for continued active EBV infection is very seldom found in patients who have been ill for more than 4 months. When the illness lasts more than 6 months, it should be investigated to see if other causes of chronic illness or CFS are present.

Hepadnaviridae - Hepatitis

• Partial dsDNA
• Endogeneous DNA - dependent DNA polymerase
• Use of overlapping reading frame
• RNA intermediate

The word "hepatitis" means inflammation of the liver. Toxins, certain drugs, some diseases, heavy alcohol use, bacterial and viral infections can all cause hepatitis. Hepatitis is also the name of a family of viral infections that affect the liver; the most common types in the United States are hepatitis A, hepatitis B, and hepatitis C.

Hepatitis A

Is an acute liver disease caused by the hepatitis A virus (HAV), lasting from a few weeks to several months. It does not lead to chronic infection.
Transmission: Ingestion of fecal matter, even in microscopic amounts, from close person-to-person contact or ingestion of contaminated food or drinks.
Vaccination: Hepatitis A vaccination is recommended for all children starting at age 1 year, travelers to certain countries, and others at risk.

Hepatitis B

Is a liver disease caused by the hepatitis B virus (HBV). It ranges in severity from a mild illness, lasting a few weeks (acute), to a serious long-term (chronic) illness that can lead to liver disease or liver cancer.
Transmission: Contact with infectious blood, semen, and other body fluids from having sex with an infected person, sharing contaminated needles to inject drugs, or from an infected mother to her newborn.
Vaccination: Hepatitis B vaccination is recommended for all infants, older children and adolescents who were not vaccinated previously, and adults at risk for HBV infection.

Acute liver infection

• Immediate symptoms
• Loss of appetiet, nausea, vomiting, fever, abdominal pain and jaundice
• About 5% to 10% of acutely infected adults become chronically infected.

Chronic liver infection

• No visual symptoms
• No abnormalities on laboratory testing
• Some will go on to develop cirrhosis and Hepatocellular carcinoma (primary liver cancer)

Hepatitis C

Is a liver disease caused by the hepatitis C virus (HCV). HCV infection sometimes results in an acute illness, but most often becomes a chronic condition that can lead to cirrhosis of the liver and liver cancer.
Transmission: Contact with the blood of an infected person, primarily through sharing contaminated needles to inject drugs.
Vaccination: There is no vaccine for hepatitis C.

Hepatitis D

Is a serious liver disease caused by the hepatitis D virus (HDV) and relies on HBV to replicate. It is uncommon in the United States.
Transmission: Contact with infectious blood, similar to how HBV is spread.
Vaccination: There is no vaccine for hepatitis D.

Hepatitis E

Is a serious liver disease caused by the hepatitis E virus (HEV) that usually results in an acute infection. It does not lead to a chronic infection. While rare in the United States, hepatitis E is common in many parts of the world.
Transmission: Ingestion of fecal matter, even in microscopic amounts; outbreaks are usually associated with contaminated water supply in countries with poor sanitation.
Vaccination: There is currently no FDA-approved vaccine for hepatitis E.