Question

Which chemokine receptors have been identified as coreceptors for HIV?

Short answer

Answer: The two major chemokine receptors that act as coreceptors for HIV are CCR5 and CXCR4. CCR5 is primarily involved in the infection of R5-tropic viruses, which are commonly seen in the early stages of HIV infection and are less aggressive. CXCR4 is mainly involved in the infection of X4-tropic viruses, which are typically observed in the later stages of HIV infection and are associated with rapid disease progression, leading to AIDS.

Step-by-step solution

Understand HIV coreceptors

Human Immunodeficiency Virus (HIV) infects human cells by attaching to specific receptors on the surface of the cell. Chemokine receptors, which are a family of G protein-coupled receptors, play a key role in this process, acting as coreceptors alongside the primary receptor, CD4. This allows the HIV virus to enter the cell, leading to infection and spread of the virus.

Identify the main chemokine receptors

Two major chemokine receptors have been identified as coreceptors for HIV. These are: 1. CCR5: C-C chemokine receptor type 5 2. CXCR4: C-X-C chemokine receptor type 4

Learn about the role of CCR5 in HIV infection

CCR5 is expressed on the surface of various immune cells such as macrophages, dendritic cells, and T cells. It is mainly involved in the infection of HIV strains known as R5-tropic viruses, which preferentially use CCR5 as a coreceptor. R5-tropic viruses are commonly seen in the early stages of HIV infection and are known to be less aggressive compared to other strains.

Learn about the role of CXCR4 in HIV infection

CXCR4 is mainly expressed on T cells and is involved in the infection of HIV strains known as X4-tropic viruses. These viruses preferentially use CXCR4 as a coreceptor instead of CCR5. X4-tropic viruses are generally observed in the later stages of HIV infection and are associated with a more rapid progression of the disease, leading to the onset of Acquired Immunodeficiency Syndrome (AIDS).

Recap the chemokine receptors for HIV

The main chemokine receptors identified as coreceptors for HIV are CCR5 and CXCR4. R5-tropic viruses use CCR5 for entry into host cells, and X4-tropic viruses use CXCR4. Both of these coreceptors play a crucial role in the infection process and disease progression.

Key concepts

Chemokine Receptors

Chemokine receptors are part of a large family of G protein-coupled receptors. These receptors are primarily involved in the immune system, directing the migration of cells towards sites of inflammation or injury. In the context of HIV infection, chemokine receptors have a significant role as they function as coreceptors that the virus uses to enter human cells. The two main chemokine receptors identified as crucial for HIV entry are CCR5 and CXCR4.

• CCR5: C-C chemokine receptor type 5 is expressed mainly on macrophages, dendritic cells, and some T cells.
• CXCR4: C-X-C chemokine receptor type 4 is generally found on T cells.

Both CCR5 and CXCR4 help HIV gain entry into the host's immune cells, assisting in the infection process. Understanding these receptors enables researchers to develop targeted treatments against HIV, potentially preventing the virus from binding and infecting cells.

CD4 Receptor

The CD4 receptor is critical in the immune system, primarily found on the surface of T-helper cells, macrophages, and dendritic cells. This receptor is responsible for recognizing antigens presented by certain cells, initiating an immune response. Regarding HIV, the CD4 receptor is the primary binding site for the virus. It serves as a gateway through which HIV can initially attach to the host cell.

Once HIV binds to the CD4 receptor, chemokine receptors such as CCR5 or CXCR4 act as coreceptors. They facilitate the fusion of the viral membrane with the cell membrane, allowing the viral genetic material to enter the host cell. The interaction between HIV and the CD4 receptor is crucial for the virus's ability to infect and spread within the host. As a primary target, the CD4 receptor is also a focus for medical interventions aiming to block HIV entry and halt disease progression.

Tropism in HIV Infection

Tropism refers to the preference of a virus for infecting specific types of cells, and in the case of HIV, it describes the selective use of chemokine coreceptors, CCR5 or CXCR4. Understanding HIV tropism provides insights into how different strains of the virus behave and progress throughout the infection.

• R5-tropic viruses: These HIV strains predominantly use the CCR5 receptor, often present during the initial stages of infection. R5-tropic strains tend to be less aggressive, but they are more common in person-to-person transmission.
• X4-tropic viruses: These strains shift to using the CXCR4 receptor and usually appear in the later stages of HIV infection. They are associated with faster progression to AIDS due to their intense replication rates.

Understanding the tropism of HIV strains can be critical for treatment planning, as therapies may vary based on which receptor the HIV variant prefers. By examining tropism, healthcare providers can better predict the disease's progression and tailor treatment to effectively contain the virus.