Hepatitis A and Hepatitis E virus

Definitions & Key takeaways

Hepatitis viruses A and E are RNA viruses that can cause acute hepatitis, and they are both RNA viruses transmitted via the feco-oral route. However, hepatitis E is not as common as hepatitis A, and usually affects developing countries. Symptoms of both types of hepatitis include fever, nausea, vomiting, diarrhea, and abdominal pain.

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Hepatitis A and E are two viruses that cause acute hepatitis.The name comes from the word hepat - meaning liver, and suffix -itis to label inflammatory disease, meaning that hepatitis is an inflammation of the liver.
They tend to cause hepatitis epidemics, especially in children and young adults. Now, even though they cause the same disease, Hepatitis A and E viruses come from different families.
Hepatitis A is a picornavirus, while hepatitis E is a hepevirus. They are naked viruses, made of a single strand RNA surrounded by a capsid, which is a spherical protein shell.
And they’re “naked” because the capsid isn’t covered by a lipid membrane. These viruses are transmitted by the fecal-oral route, in other words, you catch it by ingesting stool particles of someone who is sick - yuck!
This usually happens if infected stool ends up in the food, water and shellfish, or on surfaces. So usually, outbreaks can often be traced to the same source of food or water, and they also tend to be common in day-care centers.
Ok, now, when you eat, food travels through your pharynx, esophagus, stomach, duodenum and intestines. In the intestines all of the nutrients are absorbed and go through hepatic portal venous system, which is a system of veins that carry blood from the spleen, pancreas and intestines to the liver.
And just like nutrients, the hepatitis A or E reach the liver through the hepatic portal venous system.Now, the liver is made of functional units called hepatic lobules.
The main cells are called hepatocytes, and their main job is to use a huuuge array of enzymes to detoxify harmful substances from our blood - like drugs or alcohol; synthesize a variety of important proteins, like coagulation factors; and convert cholesterol into bile salts which along with water and bilirubin make up the bile.
Bile flows into the bile ducts and eventually reaches the gallbladder, which is a small pear-shaped hollow organ located beneath the liver.
This is where bile is stored and becomes more concentrated. Another type of liver cells are the Kupffer cells, which are modified macrophages scattered through the lobules, that destroy old red and white blood cells, bacteria, and other foreign substances.In the liver the hepatitis A virus binds to receptors on hepatocytes and Kupffer cells and enters by endocytosis, which is when a particle, in this case virus is enveloped by cell membrane and brought inside the cell.
Inside the cell, viral RNA is released from its protein coat. Then, it binds to the host ribosomes, which translate it into a single polyprotein which is cut into smaller proteins that will be used to create the capsid and RNA polymerase, to make more copies of the viral RNA.
Then, viral proteins and RNA bind to make new viral particles that exit the cell by exocytosis, which is like reverse endocytosis; they can also exit when the infected cell is destroyed by the immune system.
The presence of hepatitis A virus outside the cell has twofold effects. First, after they exit the cell, viral particles are secreted into bile.
With the bile, they travel to the small intestine and leave the body through stool. Second, the immune system reacts by bringing CD4+ and CD8+ T-cells and natural killer cells to the liver.
These cells have different roles. CD4+ T cell secrete interferon gamma to limit viral replication.
CD8+ T-cells, also known as cytotoxic T-cells, along with natural killer cells eliminate infected hepatocytes and Kupffer cells, mostly by inducing programmed cell death, called apoptosis.
This results in liver damage. On a liver biopsy, liver damage translates as ballooning hepatocytes, which are about to enter apoptosis, and councilman bodies, which are shrivelled, dying hepatocytes, and there’s also monocyte infiltration.
Ok, now, finally, the immune system secretes antibodies against the virus. Specifically, B cells create IgM antibodies first and IgG antibodies later.
These antibodies provide lifelong protection against reinfection, and are used to diagnose the disease. And just a quick note - while the hepatitis E virus life cycle is still unknown, it’s thought to be similar to that of hepatitis A.Ok, now, symptoms of hepatitis usually appear 15-50 days after infection with the hepatitis A virus, and after around 40 days for hepatitis E.
Nonspecific symptoms include fever, fatigue, loss of appetite, nausea, vomiting, abdominal pain. Specific symptoms are related to liver damage.
When hepatocytes are destroyed, bilirubin with bile salts are released into the bloodstream, and impregnate the tissues causing jaundice, which is a yellowish pigmentation of the skin, mucosa and whites of the eyes; while the bile salts in the skin cause itching.
The bilirubin from the blood is filtered by the kidneys and ends up in the urine instead of the stool, making it dark, while the stool becomes pale.
The disease usually lasts 2 to 4 weeks and most of the infected individuals completely recover. Fulminant hepatitis with liver failure, brain damage, coagulation impairment and kidney failure is very rare.
Hepatitis E can rarely cause chronic disease in immunocompromised individuals, especially those with organ transplants, as they are taking lifelong immunosuppressive treatment to prevent transplant rejection, which can also interfere with virus clearance.
In pregnant individuals, hepatitis E infections come with a high mortality rate, about 20% for the pregnant individual, and it can also cause intrauterine death, preterm delivery and stillbirth.
Diagnosis requires lab studies. Liver enzymes alanine transferase, or ALT, and aspartate transferase, or AST, are much higher than normal.
Diagnosis is confirmed in the presence of IgM type anti-HAV or anti-HEV antibodies..IgM antibodies appear around 2-3 weeks after the virus has entered the body and remain elevated for about 6 weeks.
IgG antibodies appear about two weeks after IgM.. Anti HAV IgG antibody finding means that the acute stage of the disease has passed, and also that the individual is now immune to hepatitis A.
It is also found after vaccination. Finally, anti HEV IgG antibodies persist for a long time as well, but it’s uncertain if they provide lifelong immunity against hepatitis E.
There is no specific treatment for acute hepatitis A and E. Supportive treatment, like replacing lost fluids and electrolytes, as well as dietary measures are usually taken.
Chronic hepatitis E can be treated by reducing immunosuppressive medication doses or with ribavirin and pegylated interferon.
Prevention is done by avoiding potentially contaminated food or water and with regular hand washing. There’s also an inactivated vaccine against hepatitis A, which is given in two doses, and protects against hepatitis A for up to 20 years.
Alternatively, if unvaccinated individuals have been exposed to hepatitis A, immune serum globulin can be given to prevent illness.
##Summary All right, as a quick recap hepatitis A and E are RNA viruses, transmitted by feco-oral route through contaminated water, food or dirty hands, that usually cause acute hepatitis.
They infect hepatocytes and Kupfer cells, and the immune system destroys infected cells, causing liver damage. Symptoms include fever, fatigue, loss of appetite, nausea, vomiting, abdominal pain, dark urine and pale stools and jaundice.
Hepatitis E is especially dangerous to pregnant individuals. Treatment is usually supportive and dietary.
Both can be prevented by avoiding potentially contaminated food, water and through regular hand washing. Hepatitis A can be prevented through vaccination or immune serum globulin.
fatigue loss of appetite nausea vomiting abdominal pain dark urine and pale stools and jaundice Hepatitis C is especially dangerous to pregnant individuals Treatment is usually supportive and dietary both can be prevented by avoiding potentially contaminated food water and through regular handwashing Hepatitis A can be prevented