Hepatitis C virus

Transcript

Content Reviewers:

Viviana Popa, MD

Hepatitis C virus is a part of the flaviviridae family, and it can be broken down in hepat- which refers to the liver, and -itis, which means inflammation.

So this virus affects the liver, causing hepatitis.

Hepatitis C virus is enveloped, meaning that it is surrounded by a membrane.

It also has a lipoprotein envelope that’s very similar in structure to two lipoproteins that normally transport cholesterol through the blood: low density lipoprotein, or LDL and very-low-density lipoprotein, or VLDL.

Underneath the membrane, there’s an icosahedral capsid, which is a spherical protein shell made up of 20 equilateral triangular faces.

The capsid holds a single strand positive-sense RNA, meaning that it has positive polarity, which is why it can be used directly by the host ribosomes to synthesize viral proteins.

Now, hepatitis C virus can be transmitted through contaminated blood or through sexual contact.

Once inside the body, hepatitis C virus circulates the blood and reaches the liver, where it infects the main liver cells called hepatocytes; and B lymphocytes, which are a type of immune cells that create antibodies.

First, the virus binds to the cells using its envelope, which is very similar to LDL and VLDL, so it can attach to specific LDL receptors.

Then, the virus enters the cell by endocytosis, which is when it’s wrapped by the cell membrane and brought inside the cell in a bubble called an endosome.

Next, the viral membrane fuses with the endosome and releases the capsid which dissolves in the cytoplasm, leaving only viral RNA.

Then, viral RNA binds to the host ribosomes and is used to create structural and non-structural proteins.

Structural proteins will be used to make the viral particle, while the non-structural proteins make the replication complex that contains an enzyme called RNA dependent RNA polymerase.

This enzyme uses the positive-sense viral RNA to create a negative-sense template.

And the replication complex can use the newly made negative-sense template to create more copies of the positive-sense viral RNA, which can be packaged into viral particles, along with structural proteins, in the host cell endoplasmic reticulum.

However, RNA polymerase makes a lot of mistakes, so each viral particle is a bit different.

This contributes to viral variability, and it’s what makes it so hard to create a vaccine against hepatitis C.

Finally, the viral particles exit the cell through exocytosis, which is like reverse endocytosis.

About two thirds of affected people can develop complications like: cryoglobulinemia, when the blood contains temperature sensitive antibodies called cryoglobulins; autoimmune hemolytic anemia; glomerulonephritis, or inflammation of the kidneys’ glomeruli, leukocytoclastic vasculitis, which is an inflammation of the blood vessels; diabetes; hypothyroidism; and skin conditions like porphyria cutanea tarda and lichen planus.

It’s not clear why these complications arise; however, since hepatitis C virus infects B-lymphocytes, one explanation may be that it affects the production and function of antibodies.

Since hepatitis C is transmitted through blood or sexual contact, individuals at higher risk for infection include people who use intravenous drugs, individuals who have had tattoos and/or piercings done, recipients of transfusion and organ transplants; and individuals who have unprotected sex and multiple sexual partners.

The virus can’t be transferred from an infected pregnant individual to the baby during pregnancy, but there is a 1 in 20 chance to pass it to the baby during childbirth for both vaginal delivery and c-section.

Hepatitis C virus causes three types of disease: most commonly, chronic hepatitis; but it can also cause acute hepatitis; and rarely fulminant hepatitis that quickly progresses to liver failure.