This is an antiviral immune-mechanism / drug-mechanism module structured as a biological pathway, not a specific disease. Its nodes are the steps of the innate interferon response (viral PAMP sensing by pattern-recognition receptors -> type I/III interferon induction and JAK-STAT signaling -> interferon-stimulated-gene antiviral state -> restriction of viral replication), with a viral-evasion branch (dedicated interferon antagonists). The canonical conformance / treatment target is "Interferon-Stimulated Gene Antiviral State" — the broad-spectrum, host-encoded effector state. An innate-immunity-modulator treatment (recombinant/pegylated interferon such as peginterferon lambda, or a RIG-I/STING agonist) points its target_mechanisms edge at that node to pharmacologically reinforce it; this is the conceptual inverse of the viral-antagonism (adaptive_escape) node, which records how viruses suppress the same pathway. The drug classes are described in the node text rather than modelled as separate nodes, mirroring the other antiviral modules. See projects/ANTIVIRAL.md and projects/RESPIRATORY_INFECTIONS.md.
Viral PAMP Sensing by Pattern-Recognition Receptors
trigger
The innate antiviral response begins when an infected cell detects viral pathogen-associated molecular patterns — principally viral nucleic acid — through germline-encoded pattern-recognition receptors (PRRs). The cytosolic RIG-I-like receptors RIG-I and MDA5 sense viral RNA, the cGAS-STING axis senses cytosolic DNA, and endosomal Toll-like receptors sense nucleic-acid ligands. This sensing step is the committed trigger of the entire pathway: it converts the physical presence of a virus into a signal-transduction event that initiates the antiviral program.
Used by disorders
Influenza
as Toll-like Receptor Signaling and Innate Immune Activation
Downstream
-
Type I and III Interferon Induction and JAK-STAT Signaling
PAMP sensing activates transcription factors that induce interferons, which then signal through the JAK-STAT pathway.
Type I and III Interferon Induction and JAK-STAT Signaling
effector
PAMP sensing activates transcription factors (IRF3/IRF7 and NF-kB) that induce type I (IFN-alpha/beta) and type III (IFN-lambda) interferons. Secreted interferons act back on the producing cell and on neighbouring cells through their receptors, triggering canonical JAK-STAT signaling: receptor-associated Janus kinases phosphorylate STAT transcription factors, which drive transcription of interferon-stimulated genes. This induction-and-signaling step is the amplifier of the pathway — it converts a localized sensing event into a tissue-wide antiviral transcriptional program, and it is the level at which recombinant or pegylated interferons act when given therapeutically.
Downstream
-
Interferon-Stimulated Gene Antiviral State
JAK-STAT signaling transcribes interferon-stimulated genes whose products establish the antiviral state.
Interferon-Stimulated Gene Antiviral State
therapeutic vulnerability
The products of interferon-stimulated genes (ISGs) collectively establish a cell-intrinsic antiviral state that is highly effective at resisting and controlling pathogens. Individual ISGs directly inhibit viral infection at early and late stages of the life cycle — blocking entry, degrading viral RNA, restricting translation, and impeding assembly and egress. Because this effector state is broad-spectrum (active against many unrelated viruses) and host-encoded, it is the canonical conformance/treatment target of the module: innate-immunity modulators reinforce it pharmacologically — recombinant or pegylated interferons (peginterferon lambda) supply the upstream cytokine, and RIG-I/STING agonists drive the sensing-to-interferon axis that feeds it. A treatment of that class points its target_mechanisms edge at this node.
Downstream
-
Restriction of Viral Replication
The antiviral state directly restricts viral replication, the protective output of the pathway.
-
Viral Interferon Antagonism and Innate Immune Evasion
Successful viruses encode dedicated antagonists that suppress this interferon pathway to escape restriction.
Restriction of Viral Replication
consequence
The protective output of the pathway is restriction of viral replication and a measurable clinical benefit when the response is intact or therapeutically augmented. Clinically, supplying the pathway's upstream cytokine reproduces this output: in a randomized trial a single dose of pegylated interferon lambda significantly reduced COVID-19 hospitalization/emergency events, lowered viral load, and — reflecting the broad-spectrum, host-directed nature of the interferon response — worked consistently across dominant SARS-CoV-2 variants. This consequence node is the antiviral effect the innate interferon response is deployed (or pharmacologically reinforced) to achieve.
Viral Interferon Antagonism and Innate Immune Evasion
adaptive escape
Every virus that succeeds in a host must blunt the interferon response, so dedicated viral antagonists that suppress interferon induction or signaling are near-universal. The prototype is the influenza A virus NS1 protein, a multifunctional immune modulator whose functions include inhibition of the type I interferon system in infected cells and sequestration of double-stranded RNA so it escapes sensing; together these let the virus evade immune surveillance and establish infection. This evasion branch off the antiviral-state node is the conceptual mirror of therapeutic interferon augmentation — where a drug reinforces the pathway, the virus tears it down — and explains why an otherwise competent innate response can still fail to contain a well-adapted virus. Conforming entries can attach a virus-specific interferon antagonist (NS1, and the SARS-CoV-2 ORF and nsp antagonists) to this node.