Difference Between Lentivirus and Retrovirus

Main Difference – Lentivirus vs Retrovirus

Lentivirus and retrovirus are two types of viruses that infect living cells for the completion of their life cycle. Lentivirus is a subtype of retroviruses. The main difference between lentivirus and retrovirus is that lentivirus can infect both actively-dividing and non-dividing cells whereas retroviruses can only infect mitotically-active cell types. Thus, lentivirus can infect a wide range of cell stages than retroviruses. Both lentivirus and retrovirus can be used as vehicles that carry foreign DNA molecules into another cell. The mechanism of DNA transfer mediated by viruses is known as transduction. Both lentiviruses and retroviruses are used in  to correct defective genes that are responsible for disease development.

Key Areas Covered

1. What is a Lentivirus
      – Definition, Properties, Types
2. What is a Retrovirus
     – Definition, Properties, Types
3. What are the Similarities Between Lentivirus and Retrovirus
     – Outline of Common Features
4. What is the Difference Between Lentivirus and Retrovirus
     – Comparison of Key Differences

Key Terms: HIV, Lentivirus, Recombinant DNA Technology, Retrovirus

What is Lentivirus

Lentivirus is a type of retrovirus that consists of long incubation periods and cause chronic, progressive, and typically fatal diseases in animals. Lentiviruses can be subdivided into five serotypes based on the type of vertebrate host they infect; bovine, equine, feline, ovine/caprine, and primate. The human immunodeficiency viruses (HIV) type and 2, simian (SIV), and feline (FLV) are examples of lentiviruses. Lentiviruses are used to introduce large DNA segments into the cell line (dividing), primary cells (dividing and non-dividing), neuronal cells, stem cells, and hematopoietic cells. Most lentiviral vectors are based on HIV. The structure of HIV is shown in figure 1.

Figure 1: HIV

The size of the HIV genome is 9.7 kb. The three major structural genes present in the genome are the gag (group-specif antigen), pol (polymerase), and env (envelope). The other regulatory genes are tat (HIV transactivator) and rev (regulator of expression of virion protein). In addition, four types of accessory genes are also present in the HIV genome: vif (viral infectivity), vpr (virus protein R), vpu (virus protein U), and nef (negative factor). Replication, integration, and packaging of lentiviruses are mediated by cis-acting elements of the lentiviral genome.

What is Retrovirus

Retrovirus is any type of RNA viruses that insert a DNA copy into the host genome for replication. Retroviruses are characterized by their ability to reverse transcribe their RNA genome into a cDNA copy that can be integrated into the host genome. They consist of two copies of positive sense ssRNA molecules in the genome. Retroviruses can be classified into three subfamilies based on the different types of accessory and regulatory genes present in the genome. They are oncoviruses, lentiviruses, and spumaviruses. Oncoviruses are subclassified into three categories based on the morphology; B-type, C-type, and D-type. The different subfamilies of retroviruses with examples are described in table 1.

Retrovirus Subfamilies and Examples

Retroviruses consist of reverse transcriptase enzyme for the reverse transcription of the RNA genome. Structural and enzymatic proteins such as capsid (CA), nucleocapsid (NC), integrase (IN), and protease (PR) are located inside the retroviral compartment.

Figure 2: HIV Infection Mechanism

The inner core of the retrovirus is surrounded by an outer protein layer, consisting of the matrix (MA) protein. The envelope of the retrovirus is derived from the host cell membrane. Retroviruses infect dividing cell lines and primary cells, stem cells, and hematopoietic cells.

Similarities Between Lentivirus and Retrovirus

• Lentivirus and retrovirus are two types of viruses that infect living cells.
• The capsid of both lentivirus and retrovirus is icosahedral in shape and both are enveloped viruses.
• Both lentivirus and retrovirus consist of two copies of positive sense ssRNA genome.
• Both lentivirus and retrovirus consist of reverse transcriptase (RT).
• Both lentivirus and retrovirus are capable of reverse transcribing their RNA genome into a cDNA copy.
• The genome of both lentivirus and retrovirus are encoded for polymerases.
• Both lentivirus and retrovirus can be used as vehicles that carry foreign DNA molecules into another cell.
• Both lentivirus and retrovirus are used in recombinant DNA technology to introduce comparatively large foreign DNA segments into animal cells.
• Both lentiviruses and retroviruses are used in gene therapy to correct defective genes that are responsible for disease development.
• Both lentivirus and retrovirus use different isoforms of gag, pol, and env genes for packaging.
• Both lentivirus and retrovirus can infect dividing cells, stem cells, and hematopoietic cells.
• Both lentivirus and retrovirus have a broad range of host range.
• The size of the insert of both lentivirus and retrovirus is around 8.0 kb.
• Both lentivirus and retrovirus DNA are integrated into the genome.
• Both lentivirus and retrovirus can be integrated up to 10 copies.
• Both lentivirus and retrovirus do not have a very high level of protein expression.
• The recommended biosafety level of both lentivirus and retrovirus is BSL-2.

Difference Between Lentivirus and Retrovirus

Definition

Lentivirus: Lentivirus is a type of retrovirus, consisting of long incubation periods and causing chronic, progressive, and typically fatal diseases in animals.

Retrovirus: Retrovirus is any type of RNA virus that inserts a DNA copy into the host genome for replication.

Types of Infecting Cells

Lentivirus: Lentivirus can infect both actively-dividing and non-dividing cells.

Retrovirus: Retroviruses can only infect mitotically-active cell types.

Types

Lentivirus: Lentivirus is a type of retroviruses.

Retrovirus: The three types of retroviruses are oncoviruses, lentiviruses, and spumaviruses.

Range

Lentivirus: Lentivirus can infect a wide range of cell stages. 

Retrovirus: Retrovirus can infect a narrow range of cell stages.

Size of the Genome

Lentivirus: The size of the wild-type lentiviral genome is 9.7 kb.

Retrovirus: The size of the wild-type retroviral genome is 8.3 kb.

Accessory Genes

Lentivirus: Lentiviruses consist of accessory genes in their genome.

Retrovirus: Some retroviruses such as oncoviruses lack accessory genes.

Conclusion

Lentivirus and retrovirus are two types of viruses that infect living cells. Lentivirus is a type of retroviruses. Both lentivirus and retrovirus are used in recombinant DNA technology to introduce comparatively large foreign DNA segments into animal cells. Lentivirus can infect both dividing and non-dividing cells but, retroviruses can infect only dividing cells. This is the main difference between lentivirus and retrovirus.

Reference:

1. O’Keefe, Eric P. “Nucleic Acid Delivery: Lentiviral and Retroviral Vectors.” Materials and Methods, 15 June 2015, Available here.

Image Courtesy:

1. “HI-Virion-en” By US National Institute of Health (redrawn by en:User:Carl Henderson) – US National Institute of Health (redrawn by en:User:Carl Henderson) (Public Domain) via Commons Wikimedia
2. “Hiv gross” By Translated by Raul654 – Originally from GFDL image Image:Hiv gross german.png (CC BY-SA 3.0) via Commons Wikimedia