Transmission of integrin β7 transmembrane domain topology enables gut lymphoid tissue development

A CD25-CCR7 complex initiates non-canonical IL-2 signaling

IL-2, a central regulator of immune function, binds to its receptor subunit CD25 (IL-2Rα), promoting IL-2 interaction with β and γ subunits to trigger the canonical IL-2 signaling pathway. An anti-mouse CD25 antibody, PC61, triggers alternative IL-2 signaling, leading to integrin activation. PC61 induces a complex formed by the IL-2-dependent association of CD25 with CCR7, suggesting that the formation of this complex initiates alternative IL-2 signaling. Here, we used structure-based design together with combinatorial screening to identify an IL-2 mutant (denoted IL-2(E52K)) that spares canonical IL-2 signaling but disrupts both PC61-induced complex formation and integrin activation while retaining the full CD25 affinity of the parent molecule. We also report that heparan sulfate (HS), a physiological ligand of IL-2 that triggers alternative signaling, induced IL-2-dependent CD25-CCR7 association, whereas IL-2(E52K) failed to support both HS-induced CD25-CCR7 complex formation and integrin activation. Thus, both anti-CD25 antibody and HS require common features of IL-2 needed for CD25-CCR7 complex assembly and resulting integrin activation. Collectively, these data show that IL-2 promotes CD25 interaction with CCR7, thereby forming the signal initiating complex. Furthermore, canonical and alternative IL-2 signaling can be decoupled by an IL-2 mutation, creating a tool to specify the biological role of alternative IL-2 signaling in immune responses.

Anoikis in cell fate, physiopathology, and therapeutic interventions

The extracellular matrix (ECM) governs a wide spectrum of cellular fate processes, with a particular emphasis on anoikis, an integrin-dependent form of cell death. Currently, anoikis is defined as an intrinsic apoptosis. In contrast to traditional apoptosis and necroptosis, integrin correlates ECM signaling with intracellular signaling cascades, describing the full process of anoikis. However, anoikis is frequently overlooked in physiological and pathological processes as well as traditional in vitro research models. In this review, we summarized the role of anoikis in physiological and pathological processes, spanning embryonic development, organ development, tissue repair, inflammatory responses, cardiovascular diseases, tumor metastasis, and so on. Similarly, in the realm of stem cell research focused on the functional evolution of cells, anoikis offers a potential solution to various challenges, including in vitro cell culture models, stem cell therapy, cell transplantation, and engineering applications, which are largely based on the regulation of cell fate by anoikis. More importantly, the regulatory mechanisms of anoikis based on molecular processes and ECM signaling will provide new strategies for therapeutic interventions (drug therapy and cell-based therapy) in disease. In summary, this review provides a systematic elaboration of anoikis, thus shedding light on its future research.

Selective Targeting of α4β7/MAdCAM-1 Axis Suppresses Fibrosis Progression by Reducing Proinflammatory T Cell Recruitment to the Liver

Integrin α4β7+ T cells perpetuate tissue injury in chronic inflammatory diseases, yet their role in hepatic fibrosis progression remains poorly understood. Here, we report increased accumulation of α4β7+ T cells in the liver of people with cirrhosis relative to disease controls. Similarly, hepatic fibrosis in the established mouse model of CCl4-induced liver fibrosis was associated with enrichment of intrahepatic α4β7+ CD4 and CD8 T cells. Monoclonal antibody (mAb)-mediated blockade of α4β7 or its ligand mucosal addressin cell adhesion molecule (MAdCAM)-1 attenuated hepatic inflammation and prevented fibrosis progression in CCl4-treated mice. Improvement in liver fibrosis was associated with a significant decrease in the infiltration of α4β7+ CD4 and CD8 T cells, suggesting that α4β7/MAdCAM-1 axis regulates both CD4 and CD8 T cell recruitment to the fibrotic liver, and α4β7+ T cells promote hepatic fibrosis progression. Analysis of hepatic α4β7+ and α4β7- CD4 T cells revealed that α4β7+ CD4 T cells were enriched for markers of activation and proliferation, demonstrating an effector phenotype. The findings suggest that α4β7+ T cells play a critical role in promoting hepatic fibrosis progression, and mAb-mediated blockade of α4β7 or MAdCAM-1 represents a promising therapeutic strategy for slowing hepatic fibrosis progression in chronic liver diseases.

Immune cell trafficking: a novel perspective on the gut-skin axis

Immune cell trafficking, an essential mechanism for maintaining immunological homeostasis and mounting effective responses to infections, operates under a stringent regulatory framework. Recent advances have shed light on the perturbation of cell migration patterns, highlighting how such disturbances can propagate inflammatory diseases from their origin to distal organs. This review collates and discusses current evidence that demonstrates atypical communication between the gut and skin, which are conventionally viewed as distinct immunological spheres, in the milieu of inflammation. We focus on the aberrant, reciprocal translocation of immune cells along the gut-skin axis as a pivotal factor linking intestinal and dermatological inflammatory conditions. Recognizing that the translation of these findings into clinical practices is nascent, we suggest that therapeutic strategies aimed at modulating the axis may offer substantial benefits in mitigating the widespread impact of inflammatory diseases.

IL-2 can signal via chemokine receptors to promote regulatory T cells' suppressive function

Canonical interleukin-2 (IL-2) signaling via the high-affinity CD25-containing IL-2 receptor-Janus kinase (JAK)1,3-signal transducer and activator of transcription 5 (STAT5) pathway is essential for development and maintenance of CD4+CD25HiFoxp3+ regulatory T cells (Tregs) that support immune homeostasis. Here, we report that IL-2 signaling via an alternative CD25-chemokine receptor pathway promotes the suppressive function of Tregs. Using an antibody against CD25 that biases IL-2 signaling toward this alternative pathway, we establish that this pathway increases the suppressive activity of Tregs and ameliorates murine experimental autoimmune encephalomyelitis (EAE). Furthermore, heparan sulfate, an IL-2-binding element of cell surfaces and extracellular matrix, or an engineered IL-2 immunocytokine can also direct IL-2 signaling toward this alternative pathway. Overall, these data reveal a non-canonical mechanism for IL-2 signaling that promotes suppressive functions of Tregs, further elucidates how IL-2 supports immune homeostasis, and suggests approaches to promote or suppress Treg functions.

LRP12 is an endogenous transmembrane inactivator of α4 integrins

Dynamic regulation of integrin activation and inactivation is critical for precisely controlled cell adhesion and migration in physiological and pathological processes. The molecular basis for integrin activation has been intensively studied; however, the understanding of integrin inactivation is still limited. Here, we identify LRP12 as an endogenous transmembrane inhibitor for α4 integrin activation. The LRP12 cytoplasmic domain directly binds to the integrin α4 cytoplasmic tail and inhibits talin binding to the β subunit, thus keeping integrin inactive. In migrating cells, LRP12-α4 interaction induces nascent adhesion (NA) turnover at the leading-edge protrusion. Knockdown of LRP12 leads to increased NAs and enhanced cell migration. Consistently, LRP12-deficient T cells show an enhanced homing capability in mice and lead to aggravated chronic colitis in a T cell-transfer colitis model. Altogether, LRP12 is a transmembrane inactivator for integrins that inhibits α4 integrin activation and controls cell migration by maintaining balanced NA dynamics.

Targeting integrin pathways: mechanisms and advances in therapy

Integrins are considered the main cell-adhesion transmembrane receptors that play multifaceted roles as extracellular matrix (ECM)-cytoskeletal linkers and transducers in biochemical and mechanical signals between cells and their environment in a wide range of states in health and diseases. Integrin functions are dependable on a delicate balance between active and inactive status via multiple mechanisms, including protein-protein interactions, conformational changes, and trafficking. Due to their exposure on the cell surface and sensitivity to the molecular blockade, integrins have been investigated as pharmacological targets for nearly 40 years, but given the complexity of integrins and sometimes opposite characteristics, targeting integrin therapeutics has been a challenge. To date, only seven drugs targeting integrins have been successfully marketed, including abciximab, eptifibatide, tirofiban, natalizumab, vedolizumab, lifitegrast, and carotegrast. Currently, there are approximately 90 kinds of integrin-based therapeutic drugs or imaging agents in clinical studies, including small molecules, antibodies, synthetic mimic peptides, antibody-drug conjugates (ADCs), chimeric antigen receptor (CAR) T-cell therapy, imaging agents, etc. A serious lesson from past integrin drug discovery and research efforts is that successes rely on both a deep understanding of integrin-regulatory mechanisms and unmet clinical needs. Herein, we provide a systematic and complete review of all integrin family members and integrin-mediated downstream signal transduction to highlight ongoing efforts to develop new therapies/diagnoses from bench to clinic. In addition, we further discuss the trend of drug development, how to improve the success rate of clinical trials targeting integrin therapies, and the key points for clinical research, basic research, and translational research.

The Connection Between Rap1 and Talin1 in the Activation of Integrins in Blood Cells

Integrins regulate the adhesion and migration of blood cells to ensure the proper positioning of these cells in the environment. Integrins detect physical and chemical stimuli in the extracellular matrix and regulate signaling pathways in blood cells that mediate their functions. Integrins are usually in a resting state in blood cells until agonist stimulation results in a high-affinity conformation ("integrin activation"), which is central to integrins' contribution to blood cells' trafficking and functions. In this review, we summarize the mechanisms of integrin activation in blood cells with a focus on recent advances understanding of mechanisms whereby Rap1 regulates talin1-integrin interaction to trigger integrin activation in lymphocytes, platelets, and neutrophils.

Direct Binding of Rap1 to Talin1 and to MRL Proteins Promotes Integrin Activation in CD4+ T Cells

Agonist-induced Rap1 GTP loading results in integrin activation involved in T cell trafficking and functions. MRL proteins Rap1-interacting adapter molecule (RIAM) and lamellipodin (LPD) are Rap1 effectors that can recruit talin1 to integrins, resulting in integrin activation. Recent work also implicates direct Rap1-talin1 interaction in integrin activation. Here, we analyze in mice the connections between Rap1 and talin1 that support integrin activation in conventional CD4+ T (Tconv) and CD25HiFoxp3+CD4+ regulatory T (Treg) cells. Talin1(R35E, R118E) mutation that disrupts both Rap1 binding sites results in a partial defect in αLβ2, α4β1, and α4β7 integrin activation in both Tconv and Treg cells with resulting defects in T cell homing. Talin1(R35E,R118E) Tconv manifested reduced capacity to induce colitis in an adoptive transfer mouse model. Loss of RIAM exacerbates the defects in Treg cell function caused by the talin1(R35E,R118E) mutation, and deleting both MRL proteins in combination with talin1(R35E,R118E) phenocopy the complete lack of integrin activation observed in Rap1a/b-null Treg cells. In sum, these data reveal the functionally significant connections between Rap1 and talin1 that enable αLβ2, α4β1, and α4β7 integrin activation in CD4+ T cells.

Integrin α6 overexpression promotes lymphangiogenesis and lymphatic metastasis via activating the NF-κB signaling pathway in lung adenocarcinoma

OBJECTIVE

It has been reported that tumor-associated lymphangiogenesis plays an important role in lymph node metastasis and contributes to the poor survival of lung adenocarcinoma (LUAD) patients. As yet, however, the molecular mechanism underlying LUAD-associated lymphangiogenesis has remained elusive.

METHODS

Immunohistochemistry (IHC) was used to determine the expression of integrin subunit alpha 6 (ITGA6) and the lymphatic vessel endothelial hyaluronan receptor 1 (Lyve1) in clinicopathologically characterized LUAD specimens. The effect of ITGA6 overexpression on lymphangiogenesis and lymphatic metastasis was examined by tube formation, scratch wound-healing, and cell migration assays in vitro and a popliteal lymph node metastasis model in vivo. Mechanistically, overexpression of ITGA6 and activation of NF-κB signaling were examined by real-time PCR, ubiquitination and dual-luciferase reporter assays. Finally, high ITGA6 expression in LUAD tissue samples was related to copy number variation (CNV) using the TCGA database.

RESULTS

We found that ITGA6 overexpression correlated with microlymphatic vessel density in LUAD specimens (p < 0.01). Importantly, by using a popliteal lymph node metastasis model, we found that ITGA6 upregulation significantly enhanced lymphangiogenesis and lymphatic metastasis in vivo (p < 0.05). In addition, we found that ITGA6 overexpression enhanced the capability of A549 and H1299 LUAD cells to induce tube formation and migration in human lymphatic endothelial cells (HLECs). Mechanistically, we found that ITGA6 sustained NF-κB activity via binding and promoting K63 polyubiquitination of TNF receptor-associated factor 2 (TRAF2). Finally, CNV analysis revealed ITGA6 amplification of 27.5% in the LUAD tissue samples in the TCGA database.

CONCLUSIONS

Taken together, our results uncover a plausible role for ITGA6 in mediating lymphangiogenesis and lymphatic metastasis and may provide a basis for targeting ITGA6 to treat LUAD lymphatic metastasis.

Insight Into Pathological Integrin αIIbβ3 Activation From Safeguarding The Inactive State

The inhibition of physiological activation pathways of the platelet adhesion receptor integrin αIIbβ3 may fail to prevent fatal thrombosis, suggesting that the receptor is at risk of activation by yet an unidentified pathway. Here, we report the discovery and characterization of a structural motif that safeguards the receptor by selectively destabilizing its inactive state. At the extracellular membrane border, an overpacked αIIb(W968)-β3(I693) contact prevents αIIb(Gly972) from optimally assembling the αIIbβ3 transmembrane complex, which maintains the inactive state. This destabilization of approximately 1.0 kcal/mol could be mitigated by hydrodynamic forces but not physiological agonists, thereby identifying hydrodynamic forces as pathological activation stimulus. As reproductive life spans are not generally limited by cardiovascular disease, it appears that the evolution of the safeguard was driven by fatal, hydrodynamic force-mediated integrin αIIbβ3 activation in the healthy cardiovascular system. The triggering of the safeguard solely by pathological stimuli achieves an effective increase of the free energy barrier between inactive and active receptor states without incurring an increased risk of bleeding. Thus, integrin αIIbβ3 has evolved an effective way to protect receptor functional states that indicates the availability of a mechanical activation pathway when hydrodynamic forces exceed physiological margins.

The Activation and Regulation of β2 Integrins in Phagocytes and Phagocytosis

Phagocytes, which include neutrophils, monocytes, macrophages, and dendritic cells, protect the body by removing foreign particles, bacteria, and dead or dying cells. Phagocytic integrins are greatly involved in the recognition of and adhesion to specific antigens on cells and pathogens during phagocytosis as well as the recruitment of immune cells. β2 integrins, including αLβ2, αMβ2, αXβ2, and αDβ2, are the major integrins presented on the phagocyte surface. The activation of β2 integrins is essential to the recruitment and phagocytic function of these phagocytes and is critical for the regulation of inflammation and immune defense. However, aberrant activation of β2 integrins aggravates auto-immune diseases, such as psoriasis, arthritis, and multiple sclerosis, and facilitates tumor metastasis, making them double-edged swords as candidates for therapeutic intervention. Therefore, precise regulation of phagocyte activities by targeting β2 integrins should promote their host defense functions with minimal side effects on other cells. Here, we reviewed advances in the regulatory mechanisms underlying β2 integrin inside-out signaling, as well as the roles of β2 integrin activation in phagocyte functions.

Visualization of integrin molecules by fluorescence imaging and techniques

Integrin molecules are transmembrane αβ heterodimers involved in cell adhesion, trafficking, and signaling. Upon activation, integrins undergo dynamic conformational changes that regulate their affinity to ligands. The physiological functions and activation mechanisms of integrins have been heavily discussed in previous studies and reviews, but the fluorescence imaging techniques -which are powerful tools for biological studies- have not. Here we review the fluorescence labeling methods, imaging techniques, as well as Förster resonance energy transfer assays used to study integrin expression, localization, activation, and functions.

Distinct integrin activation pathways for effector and regulatory T cell trafficking and function

Integrin activation mediates lymphocyte trafficking and immune functions. Conventional T cell (Tconv cell) integrin activation requires Rap1-interacting adaptor molecule (RIAM). Here, we report that Apbb1ip-/- (RIAM-null) mice are protected from spontaneous colitis due to IL-10 deficiency, a model of inflammatory bowel disease (IBD). Protection is ascribable to reduced accumulation and homing of Tconv cells in gut-associated lymphoid tissue (GALT). Surprisingly, there are abundant RIAM-null regulatory T cells (T reg cells) in the GALT. RIAM-null T reg cells exhibit normal homing to GALT and lymph nodes due to preserved activation of integrins αLβ2, α4β1, and α4β7. Similar to Tconv cells, T reg cell integrin activation and immune function require Rap1; however, lamellipodin (Raph1), a RIAM paralogue, compensates for RIAM deficiency. Thus, in contrast to Tconv cells, RIAM is dispensable for T reg cell integrin activation and suppressive function. In consequence, inhibition of RIAM can inhibit spontaneous Tconv cell-mediated autoimmune colitis while preserving T reg cell trafficking and function.

Blocking integrin α4β7-mediated CD4 T cell recruitment to the intestine and liver protects mice from western diet-induced non-alcoholic steatohepatitis

BACKGROUND & AIMS

The heterodimeric integrin receptor α₄β₇ regulates CD4 T cell recruitment to inflamed tissues, but its role in the pathogenesis of non-alcoholic steatohepatitis (NASH) is unknown. Herein, we examined the role of α₄β₇-mediated recruitment of CD4 T cells to the intestine and liver in NASH.

METHODS

Male littermate F11r^+/+ (control) and junctional adhesion molecule A knockout F11r^-/- mice were fed a normal diet or a western diet (WD) for 8 weeks. Liver and intestinal tissues were analyzed by histology, quantitative reverse transcription PCR (qRT-PCR), 16s rRNA sequencing and flow cytometry. Colonic mucosa-associated microbiota were analyzed using 16s rRNA sequencing. Liver biopsies from patients with NASH were analyzed by confocal imaging and qRT-PCR.

RESULTS

WD-fed knockout mice developed NASH and had increased hepatic and intestinal α₄β₇⁺ CD4 T cells relative to control mice who developed mild hepatic steatosis. The increase in α₄β₇⁺ CD4 T cells was associated with markedly higher expression of the α₄β₇ ligand mucosal addressin cell adhesion molecule 1 (MAdCAM-1) in the colonic mucosa and livers of WD-fed knockout mice. Elevated MAdCAM-1 expression correlated with increased mucosa-associated Proteobacteria in the WD-fed knockout mice. Antibiotics reduced MAdCAM-1 expression indicating that the diet-altered microbiota promoted colonic and hepatic MAdCAM-1 expression. α₄β₇ blockade in WD-fed knockout mice significantly decreased α₄β₇⁺ CD4 T cell recruitment to the intestine and liver, attenuated hepatic inflammation and fibrosis, and improved metabolic indices. MAdCAM-1 blockade also reduced hepatic inflammation and fibrosis in WD-fed knockout mice. Hepatic MAdCAM-1 expression was elevated in patients with NASH and correlated with higher expression of α₄ and β₇ integrins.

CONCLUSIONS

These findings establish α₄β₇/MAdCAM-1 as a critical axis regulating NASH development through colonic and hepatic CD4 T cell recruitment.

LAY SUMMARY

Non-alcoholic steatohepatitis (NASH) is an advanced and progressive form of non-alcoholic fatty liver disease (NAFLD), and despite its growing incidence no therapies currently exist to halt NAFLD progression. Herein, we show that blocking integrin receptor α₄β₇-mediated recruitment of CD4 T cells to the intestine and liver not only attenuates hepatic inflammation and fibrosis, but also improves metabolic derangements associated with NASH. These findings provide evidence for the potential therapeutic application of α₄β₇ antibody in the treatment of human NASH.

Chapter 22: Structural and signaling functions of integrins

The integrin family of transmembrane adhesion receptors is essential for sensing and adhering to the extracellular environment. Integrins are heterodimers composed of non-covalently associated α and β subunits that engage extracellular matrix proteins and couple to intracellular signaling and cytoskeletal complexes. Humans have 24 different integrin heterodimers with differing ligand binding specificities and non-redundant functions. Complex structural rearrangements control the ability of integrins to engage ligands and to activate diverse downstream signaling networks, modulating cell adhesion and dynamics, processes which are crucial for metazoan life and development. Here we review the structural and signaling functions of integrins focusing on recent advances which have enhanced our understanding of how integrins are activated and regulated, and the cytoplasmic signaling networks downstream of integrins.

Frontline Science: A flexible kink in the transmembrane domain impairs β2 integrin extension and cell arrest from rolling

β2 integrins are the main adhesion molecules in neutrophils and other leukocytes and are rapidly activated by inside-out signaling, which results in conformational changes that are transmitted through the transmembrane domain (TMD). Here, we investigated the biologic effect of introducing a proline mutation in the β2 integrin TMD to create a flexible kink that uncouples the topology of the inner half of the TMD from the outer half and impairs integrin activation. The β2 integrin alpha chains, αL, αM, αX, and αD, all contain an inserted (I) domain with homology to von Willebrand factor A domain. β2 activation was monitored in a homogenous binding assay of 2 reporter monoclonal antibodies: KIM127 reporting extension (E+ ) and mAb24 reporting the high-affinity (H+ ) conformation of the β2 I-like domain. The proline mutation partially diminished chemokine-induced extension, but not the high-affinity conformation. The proline mutation in the TMD of β2 completely inhibited arrest of rolling HL-60 cells in response to the chemokine IL-8. TMD mutant HL-60 cells rolling on P-selectin and ICAM-1 were unable to reduce their rolling velocity in response to IL-8. Quantitative dynamic footprinting live-cell imaging showed that blocking TMD topology transmission impaired the chemokine-induced activation of β2, limiting the appearance of extended high-affinity (E+ H+ ) β2. This also resulted in a defect in early spreading (3 min after arrest), which could be overcome by forced integrin activation using Mn2+ . We conclude that the TMD proline mutation severely impairs β2 integrin extension, cell arrest, and early spreading.

Kinky integrins reveal a new wrinkle in neutrophil activation

Discussion on the flexible kink produced in the β₂ -integrin transmembrane domain blocking mechanotransduction of signals necessary for neutrophil arrest and spreading.

Rap1 binding and a lipid-dependent helix in talin F1 domain promote integrin activation in tandem

Rap1 GTPases bind effectors, such as RIAM, to enable talin1 to induce integrin activation. In addition, Rap1 binds directly to the talin1 F0 domain (F0); however, this interaction makes a limited contribution to integrin activation in CHO cells or platelets. Here, we show that talin1 F1 domain (F1) contains a previously undetected Rap1-binding site of similar affinity to that in F0. A structure-guided point mutant (R118E) in F1, which blocks Rap1 binding, abolishes the capacity of Rap1 to potentiate talin1-induced integrin activation. The capacity of F1 to mediate Rap1-dependent integrin activation depends on a unique loop in F1 that has a propensity to form a helix upon binding to membrane lipids. Basic membrane-facing residues of this helix are critical, as charge-reversal mutations led to dramatic suppression of talin1-dependent activation. Thus, a novel Rap1-binding site and a transient lipid-dependent helix in F1 work in tandem to enable a direct Rap1-talin1 interaction to cause integrin activation.

Talin-2 regulates integrin functions in exosomes

Integrins on exosomes have been shown to mediate binding to recipient cells, potentially playing important roles in controlling exosomal internalization and organ distributions. Although the ability of cellular integrins to mediate cell adhesion is known to be regulated by the cytoplasmic adaptor protein talin, whether the activity of exosomal integrins is similarly regulated by talin remains to be elucidated. Here we have studied this question in T-cell exosomes that surface express the integrins αLβ2 and α4β7. T-cells and T-cell exosomes engineered to lack talin-2 showed reduced binding to the integrin ligand ICAM-1 and MAdCAM-1 compared with control T-cells and exosomes, despite the fact that those T cells and exosomes express intact levels of the other isoform talin-1. In addition, talin-2-deficient T-cell exosomes were less efficiently internalized by endothelial cells, compared with control exosomes. These results suggest that the mechanisms of talin-mediated integrin regulation operate similarly in cells and exosomes.

Oral immunization with recombinant Lactococcus lactis NZ9000 expressing human papillomavirus type 16 E7 antigen and evaluation of its immune effects in female C57BL/6 mice

The ORFs of both native and codon-optimized E7 genes were successfully fused to SPusp45 signal peptide and expressed by a nisin-controlled gene expression system in the NZ9000 strains of Lactococcus lactis. Recombinant strains were confirmed by Western blot analysis. To measure immune responses against the E7 antigen, specific-pathogen-free C57BL/6 mice were inoculated with L lactis harboring pNZ8123-rE7 by oral gavage. Then, specific antibodies and cytokines were measured by enzyme-linked immunosorbent assay and enzyme-linked immunospot assay, respectively. Oral administration of L lactis strains expressing rE7 elicited the highest levels of E7-specific antibody and greatest numbers of E7-specific CD4⁺ T helper and CD8⁺ T cell precursors. Our outcomes indicated that the HPV-16 E7 specific IL-2- and IFN-γ-secreting T cells in antigen-stimulated splenocytes and intestinal mucosal lymphocytes were significantly higher than the control groups. Our data also demonstrated that mice vaccinated with recombinant L lactis were able to generate potent protective effects against challenge with the E7-expressing tumor cell line (TC-1). Moreover, L lactis containing pNZ8123-HPV16-optiE7 showed strong therapeutic antitumor effects against established tumors in vivo. These findings demonstrate that recombinant L lactis induce both humoral and cellular immune responses in mice and are therefore recommended for therapeutic treatments in humans after oral administration.