PVRIG

PVRIG (CD112R) is an inhibitory immune checkpoint receptor on T cells and NK cells that suppresses antitumor and antigen-specific effector responses by engaging its high-affinity ligand PVRL2 (Nectin-2/CD112). PVRIG binds PVRL2 — but not PVR/CD155 — through a unique CC' loop and charged F-strand residues that form a double-lock-and-key interface, competing with the activating receptor CD226 for PVRL2 access (PMID:26755705, PMID:38626767). Genetic epistasis experiments place PVRIG strictly downstream of PVRL2 in the tumor microenvironment; PVRIG-deficient CD8+ T cells and NK cells mount stronger effector responses, and PVRIG blockade — especially combined with TIGIT or PD-1 pathway inhibition — enhances cytotoxicity and reduces tumor growth in vivo (PMID:30659055, PMID:34174928, PMID:38588410). On NK cells, PVRIG is constitutively trafficked from the ER/Golgi to the cell surface where it undergoes rapid turnover, with surface levels decreasing upon activation (PMID:33147937).

1. 2016 High

   Identification of PVRIG as a coinhibitory receptor and PVRL2 as its ligand established a new checkpoint axis competing with the activating receptor CD226 for the same ligand.

   Evidence Binding assays, competition assays, and T cell functional assays in human cells

   PMID:26755705

   Open questions at the time

   • Signaling pathway downstream of PVRIG engagement not defined
   • Relevance to NK cells not yet tested
   • In vivo role in tumor immunity unknown
2. 2017 Medium

   Demonstrating PVRIG expression and inhibitory function on NK cells extended the receptor's role beyond T cells and showed combinatorial benefit with TIGIT blockade for enhancing ADCC.

   Evidence Flow cytometry for NK subset expression, NK-mediated ADCC assays with trastuzumab against breast cancer cells

   PMID:28623459

   Open questions at the time

   • Single-lab study without in vivo validation of NK-specific blockade
   • Whether PVRIG signals via ITIM or other motifs on NK cells not addressed
   • Ligand specificity on NK cells not formally tested
3. 2019 High

   Establishing that PVRIG binds selectively to PVRL2 (not PVR) and is nonredundant with TIGIT-PVR demonstrated two parallel, independent inhibitory axes within the nectin/nectin-like receptor family, with combinatorial blockade yielding additive benefit.

   Evidence Binding specificity assays, CD8+ T cell functional assays, antibody blockade on primary TILs, PVRIG-KO mice in infection and tumor models

   PMID:30659054 PMID:30659055

   Open questions at the time

   • Intracellular signaling mechanism of PVRIG still undefined
   • Whether PVRIG contributes to T cell exhaustion programs not resolved
   • Role in human tumors beyond ex vivo TIL experiments not established
4. 2021 Medium

   Subcellular trafficking studies revealed that PVRIG is constitutively shuttled from the ER/Golgi to the NK cell surface and undergoes activation-induced downregulation, explaining why surface levels are dynamically regulated in the tumor microenvironment.

   Evidence Surface versus intracellular flow cytometry, subcellular fractionation/ER-Golgi trafficking assays, NK cell activation assays against AML blasts

   PMID:33147937

   Open questions at the time

   • Single-lab study; mechanism of activation-induced internalization or degradation not identified
   • Whether trafficking regulation occurs similarly in T cells not tested
   • Ubiquitination or other post-translational modifications governing turnover unknown
5. 2021 High

   In vivo depletion and Rag1-deficient experiments demonstrated that PVRIG blockade acts directly on both NK cells and CD8+ T cells to inhibit exhaustion and slow tumor growth, resolving the cellular mediators of therapeutic efficacy.

   Evidence PVRIG-KO mice, in vivo NK/CD8 depletion, Rag1−/− models, syngeneic and human xenograft tumor models

   PMID:34174928

   Open questions at the time

   • Molecular definition of how PVRIG drives exhaustion programs absent
   • Contribution of CD4+ T cells or other immune subsets not assessed
   • Human in vivo efficacy not yet demonstrated
6. 2024 High

   The crystal structure of the PVRIG–Nectin-2 complex revealed the structural basis for ligand selectivity: a unique CC' loop and charged F-strand residues create a double-lock-and-key interface that excludes PVR binding.

   Evidence X-ray crystallography of the PVRIG–Nectin-2 complex with mutagenesis validation

   PMID:38626767

   Open questions at the time

   • No structural information on how PVRIG cytoplasmic domain engages signaling mediators
   • Whether the CC' loop interface can be targeted by small molecules not explored
   • Dynamics of receptor oligomerization at the cell surface unknown
7. 2024 High

   Genetic epistasis showed PVRIG functions strictly downstream of PVRL2 and that PVRL2 possesses PVRIG-independent inhibitory functions, refining the hierarchy of the PVRL2 signaling axis in tumor immunity.

   Evidence PVRL2-KO, PVRIG-KO, and double-KO syngeneic tumor models with immune cell depletion

   PMID:38588410

   Open questions at the time

   • Identity of the PVRIG-independent inhibitory receptor(s) for PVRL2 not determined
   • Whether epistatic relationship holds in human tumors unknown
   • Relevance in immunologically cold tumor types not tested
8. 2024 Medium

   Therapeutic dissection of an anti-PVRIG antibody showed that both checkpoint blockade and FcγR-mediated effector function are required for maximal NK cell activation and antitumor efficacy, informing optimal antibody design.

   Evidence SPR/ELISA binding, Fc-variant antibody comparison, in vitro NK/T cell assays, in vivo tumor models

   PMID:38554184

   Open questions at the time

   • Single-lab finding; independent replication with different Fc-engineered antibodies needed
   • Mechanism of FcγR-dependent NK activation (co-stimulatory vs. ADCC-like) not fully dissected
   • Optimal combination partners in human trials remain undefined

• The intracellular signaling pathway activated by PVRIG engagement — including its proximal signaling mediators, ITIM/ITSM utilization, and transcriptional consequences — remains undefined.
• No phosphoproteomics or proximal signaling analysis reported
• Relationship between PVRIG signaling and T cell exhaustion transcriptional programs uncharacterized
• No structural data on the PVRIG cytoplasmic domain or its adaptor interactions