Which hepatitis virus is an enveloped, negative-sense, single-stranded RNA virus that replicates in the cytoplasm and requires HBsAg for its replication?

Question

Accepted Answer

D. Hepatitis D virus. ## Hepatitis D Virus (HDV) — Structural and Replication Features

### Virion Structure
**Key Point:** Hepatitis D virus is a defective RNA virus that requires hepatitis B surface antigen (HBsAg) for virion assembly and transmission.

### Genomic and Replication Characteristics
- **Genome:** Negative-sense, single-stranded circular RNA (~1.7 kb) — the smallest human RNA virus
- **Envelope:** Lipid bilayer envelope derived from host hepatocyte membrane
- **Replication site:** Cytoplasm (unlike HBV, which replicates in nucleus)
- **Dependency:** Obligate requirement for HBsAg for:
  - Virion assembly
  - Budding from hepatocyte
  - Transmission to other cells

### Comparison with Other Hepatitis Viruses

| Feature | HAV | HBV | HCV | HDV | HEV |
| --- | --- | --- | --- | --- | --- |
| **Genome** | (+) ssRNA | dsDNA | (+) ssRNA | (−) ssRNA | (+) ssRNA |
| **Envelope** | No | Yes | Yes | Yes | No |
| **Replication Site** | Cytoplasm | Nucleus | Cytoplasm | Cytoplasm | Cytoplasm |
| **Requires HBsAg** | No | — | No | **Yes** | No |
| **Defective Virus** | No | No | No | **Yes** | No |

**High-Yield:** HDV is the **only defective human virus** — it cannot complete its life cycle without HBsAg from HBV. This is why HDV infection occurs only as coinfection (with acute HBV) or superinfection (in chronic HBV carriers).

### Clinical Significance
- HDV coinfection with acute HBV → more severe acute hepatitis
- HDV superinfection in chronic HBV → rapid progression to cirrhosis
- Prevention: HBV vaccination prevents HDV (since HDV cannot occur without HBV)

[cite:Robbins 10e Ch 18]

Answer

A. Hepatitis E virus

Answer

B. Hepatitis B virus

Answer

C. Hepatitis A virus

Which hepatitis virus is an enveloped, negative-sense, single-stranded RNA virus that replicates in the cytoplasm and requires HBsAg for its replication?

Explanation

Hepatitis D Virus (HDV) — Structural and Replication Features

Virion Structure

Genomic and Replication Characteristics

Comparison with Other Hepatitis Viruses

Clinical Significance

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Feature	HAV	HBV	HCV	HDV	HEV
Genome	(+) ssRNA	dsDNA	(+) ssRNA	(−) ssRNA	(+) ssRNA
Envelope	No	Yes	Yes	Yes	No
Replication Site	Cytoplasm	Nucleus	Cytoplasm	Cytoplasm	Cytoplasm
Requires HBsAg	No	—	No	Yes	No
Defective Virus	No	No	No	Yes	No