The body responds to Respiratory Syncytial Virus (RSV) via which receptor?

AIIMS CRE, SNO-2024

Applied Microbiology & Infection control

Easy

Appeared in: AIIMS CRE, SNO-2024

Explanation

TLR4 is a key pattern recognition receptor of the innate immune system located on the cell's plasma membrane.
While famous for detecting bacterial LPS, TLR4 also specifically recognizes the Fusion (F) protein of the Respiratory Syncytial Virus (RSV).
This binding initiates a powerful inflammatory response by activating signaling pathways that lead to the production of cytokines and interferons.
This TLR4-mediated inflammation is a major contributor to the pathology of RSV-induced bronchiolitis.

Option B: TLR8 recognizes single-stranded RNA (ssRNA) within endosomes. While RSV is an ssRNA virus, the primary recognition of the viral particle on the cell surface that drives the characteristic inflammatory disease is via TLR4 binding to the F-protein.
Option C: TLR2 primarily recognizes lipoproteins and peptidoglycan, which are characteristic components of bacterial cell walls, particularly Gram-positive bacteria.
Option D: TLR9 recognizes unmethylated CpG DNA motifs found in the genomes of bacteria and DNA viruses. RSV is an RNA virus and does not contain DNA.

Visual 1: Diagram: Illustrating a host cell membrane with the TLR4 receptor binding to the Fusion (F) protein on the surface of the Respiratory Syncytial Virus (RSV). This visualizes the initial step of immune recognition.
Visual 2: Flowchart: Showing the signaling pathway after TLR4 activation, starting with the MyD88-dependent pathway, leading to NF-κB activation and the production of inflammatory cytokines. This explains the downstream consequences of receptor binding.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Innate immunity and viral recognition by Toll-like receptors (TLRs) as background academic context rather than a clinical decision trigger.
The severe inflammation in RSV-induced bronchiolitis, which causes airway narrowing and respiratory distress in infants, is largely driven by the TLR4 signaling pathway. Understanding this helps explain the disease's severity.
Knowledge of the TLR4-RSV interaction is critical for developing targeted antiviral therapies and vaccines. Drugs that modulate the TLR4 response could potentially reduce lung inflammation and damage.
What if the patient was an adult? Adults are frequently reinfected with RSV, but the disease is much milder. This is due to a more mature and regulated immune response, including memory components, which prevents the hyper-inflammatory TLR4-driven response seen in immunologically naive infants.

How to Approach the Question

First, identify the core elements of the question: the pathogen is Respiratory Syncytial Virus (RSV) and the question asks for the host receptor involved in the response.
Recall the basic properties of RSV: it's an RNA virus with important surface proteins (F and G proteins).
Next, review the function of the Toll-like receptors (TLRs) provided in the options. This is a foundational topic in immunology.
Systematically evaluate each option against your knowledge of RSV. TLR9 detects DNA, so it's incorrect for an RNA virus. TLR2 detects bacterial components, so it's also incorrect.
This leaves TLR4 and TLR8. TLR8 detects ssRNA, which RSV has, making it a plausible distractor. However, recall that TLR4 is a major surface receptor known to bind viral proteins and is famously implicated in the inflammatory response to RSV's F-protein.
Conclude that TLR4 is the most accurate answer for the primary recognition event that drives the characteristic pathology of RSV infection.

Concept Tested & Keywords

Concept Tested: Innate immunity and viral recognition by Toll-like receptors (TLRs)
Stem keywords: Respiratory Syncytial Virus (RSV), receptor, body responds
Lead-in keywords: via which
Negative lead-in flag: false

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