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The MHC-binding and gp120-binding functions of CD4 are separable
D Lamarre1, A Ashkenazi, S Fleury
1Laboratoire d'Immunologie, Institut de Recherches Cliniques de Montréal, Québec, Canada.
Science (New York, N.Y.)
|August 18, 1989
Summary
Researchers identified distinct binding sites on CD4 for HIV and MHC class II molecules. This separation allows for designing CD4 analogs to block HIV without disrupting normal immune function.
Area of Science:
- Immunology
- Virology
- Molecular Biology
Background:
- CD4 is a cell surface glycoprotein involved in immune responses and serves as the receptor for Human Immunodeficiency Virus (HIV).
- CD4 interacts with class II Major Histocompatibility (MHC) molecules, crucial for immune system communication.
- HIV-1's gp120 envelope glycoprotein binds to CD4, initiating viral entry.
Purpose of the Study:
- To identify CD4 regions critical for class II MHC binding.
- To determine if CD4 binding sites for gp120 and class II MHC are related.
- To explore the possibility of separating these binding functions.
Main Methods:
- Utilized homolog-scanning mutagenesis to alter CD4 protein regions.
- Assessed the impact of mutations on both class II MHC binding and gp120 binding.
- Analyzed mutations affecting one binding function without altering the other.
Main Results:
- Mutations in the first three immunoglobulin-like domains of CD4 abolished class II MHC binding.
- gp120 binding could be abolished independently of class II MHC binding.
- One mutation significantly reduced binding for both gp120 and class II MHC, suggesting some overlap.
Conclusions:
- The binding sites for gp120 (HIV) and class II MHC on CD4 are distinct and separable.
- It is feasible to engineer CD4 analogs that block HIV infection.
- Such analogs could potentially avoid interfering with normal immune responses mediated by class II MHC interactions.