Which viral protein of rabies virus is the primary target of neutralizing antibodies and is essential for viral attachment and entry into host cells?

Explanation

## Rabies Virus Glycoprotein (G Protein) **Key Point:** The **glycoprotein (G protein)** is the sole surface antigen of rabies virus and is the primary target of neutralizing antibodies. It is essential for viral attachment to host cell receptors and membrane fusion during viral entry. ### Structure and Function of G Protein | Feature | Details | |---------|----------| | **Location** | Embedded in viral envelope as trimeric spikes | | **Molecular weight** | ~65 kDa | | **Function** | Receptor binding and membrane fusion | | **Immunogenicity** | Highly immunogenic; induces neutralizing antibodies | | **Epitopes** | Multiple conformational and linear epitopes | ### Role in Pathogenesis 1. **Receptor binding:** G protein binds to acetylcholine receptors (AChR) and other receptors (NGFR, AMPAR) on host cells 2. **Viral entry:** Mediates pH-dependent membrane fusion in endosomes 3. **Neurotropism:** Determines tropism for neurons and CNS invasion 4. **Immune evasion:** Undergoes antigenic variation in some strains ### Immunological Significance **High-Yield:** Post-exposure prophylaxis (PEP) with rabies vaccine works by inducing **G protein-specific neutralizing antibodies** that prevent viral entry and dissemination. **Mnemonic:** **GAG** = **G**lycoprotein is the **A**ntigen that **G**enerates neutralizing antibodies. **Clinical Pearl:** Monoclonal antibodies against G protein are used in passive immunotherapy (rabies immunoglobulin) for post-exposure prophylaxis.