Question

Which form of hepatitisvirus can only infect an individual who is already infected with another hepatitisvirus? a. HDV b. HAV c. \(\mathrm{HBV}\) d. HEV

Short answer

The Hepatitis D virus (HDV) can only infect an individual who is already infected with the Hepatitis B virus (HBV).

Step-by-step solution

Understanding the question

The question asks to identify the form of hepatitis virus which cannot infect an individual unless they are already infected with another hepatitis virus. Hepatitis viruses vary in their mode of transmission and their ability to cause infection.

Identifying the dependent hepatitis virus

Hepatitis D virus (HDV) is known to be a 'satellite' virus, meaning it can only propagate in the presence of Hepatitis B virus (HBV). Therefore, HDV requires an individual to be infected with HBV to cause infection.

Selecting the correct answer

Given the information that HDV requires HBV for infection, we can conclude that the correct form of hepatitis virus is Hepatitis D virus (HDV). Therefore, the correct answer is option a. HDV.

Key concepts

HDV Infection

Hepatitis D virus (HDV) is a unique viral agent that induces viral hepatitis only in individuals already infected with the Hepatitis B virus (HBV). HDV infection can occur simultaneously with an acute HBV infection or can superinfect those with existing chronic HBV. This specialized form of hepatitis can significantly worsen the severity and outcome of liver disease compared to HBV alone. HDV utilizes the envelope proteins of HBV to assemble and produce viable virions, which can then infect liver cells. It’s essential to diagnose HDV promptly for it can lead to more severe health complications, including cirrhosis and hepatocellular carcinoma.

Understanding HDV's lifecycle and interactions with HBV is crucial in managing such coinfections. In the steps provided in the textbook, recognizing the dependency of HDV on HBV allows a student to zero in on the correct answer with confidence, reflecting the importance of knowing these interactions in an educational context.

HBV Dependency

Hepatitis B virus (HBV) dependency plays a critical role when examining HDV infection. HBV, a DNA virus, provides the necessary building blocks for HDV, an RNA virus, to propagate. Unlike HDV, HBV can independently infect and replicate within liver cells. However, the presence of HBV in a cell is a prerequisite for HDV assembly because HDV lacks the required proteins for forming an outer shell (envelope) on its own.

This unique relationship means that preventative measures and treatments for HBV can also affect the control and spread of HDV, underlining the need for comprehensive vaccination programs targeting HBV to help prevent HDV superinfection. By highlighting the HBV dependency in educational resources, students gain valuable insight into virus relationships and the importance of vaccinations in infectious disease control.

Satellite Virus

Describing HDV as a 'satellite virus' refers to its reliance on a helper virus, in this case, HBV, for its replication and lifecycle. Satellite viruses contain their own nucleic acid but cannot form infectious particles without the assistance of the helper virus's structural proteins. HDV adopts the HBV's surface antigens to form its envelope, enabling it to infect liver cells.

This interdependent relationship showcases an intriguing aspect of virology where one virus can hijack another virus's components for survival. The concept of satellite viruses like HDV is not only pivotal for students learning about viral infections but also for scientists developing antiviral therapies. Treatments targeting HBV help prevent HDV replication, thereby controlling coinfections. Understanding the satellite nature of HDV is essential for comprehending the broader implications of interconnected viral diseases.