The effects of TLR activation on T-cell development and differentiation

Invading pathogens have unique molecular signatures that are recognized by Toll-like receptors (TLRs) resulting in either activation of antigen-presenting cells (APCs) and/or costimulation of T cells inducing both innate and adaptive immunity. TLRs are also involved in T-cell development and can reprogram Treg cells to become helper cells. T cells consist of various subsets, that is, Th1, Th2, Th17, T follicular helper (Tfh), cytotoxic T lymphocytes (CTLs), regulatory T cells (Treg) and these originate from thymic progenitor thymocytes. T-cell receptor (TCR) activation in distinct T-cell subsets with different TLRs results in differing outcomes, for example, activation of TLR4 expressed in T cells promotes suppressive function of regulatory T cells (Treg), while activation of TLR6 expressed in T cells abrogates Treg function. The current state of knowledge of regarding TLR-mediated T-cell development and differentiation is reviewed.

Low incidence of complications from endoscopic gastric variceal obturation with butyl cyanoacrylate

BACKGROUND & AIMS

Endoscopic variceal obturation with tissue adhesive is used to control gastric variceal bleeding. We investigated the prevalence of serious complications from this therapy.

METHODS

We performed a retrospective analysis of complications that occurred in 753 patients with gastric variceal hemorrhages who were hospitalized in 2 tertiary referral hospitals. All patients received N-butyl-2-cyanoacrylate as therapy for endoscopic variceal obturation.

RESULTS

Complications occurred in 51 patients. Thirty-three patients experienced rebleeding because of early-onset (within 3 months) extrusion of the N-butyl-2-cyanoacrylate glue cast (4.4%), 10 patients developed sepsis (1.3%), and 5 patients developed distant embolisms (0.7%; 1 pulmonary, 1 brain, and 3 splenic). One patient had major gastric variceal bleeding after endoscopic variceal obturation (0.1%), 1 developed a large gastric ulcer (0.1%), and 1 had mesentery hematoma, hemoperitoneum, and infection in the abdominal cavity (0.1%). The complication-related mortality was 0.53% (3 deaths from sepsis and 1 death from rebleeding after early-onset glue cast extrusion).

CONCLUSIONS

The occurrence of complications after endoscopic variceal obturation with N-butyl-2-cyanoacrylate in gastric varices treatment is rare.

Immunomodulatory effects of dsRNA and its potential as vaccine adjuvant

dsRNA can be detected by pattern recognition receptors, for example, TLR3, MDA-5, NLRP3 to induce proinflammatory cytokines responsible for innate/adaptive immunity. Recognized by endosomal TLR3 in myeloid DCs (mDCs), dsRNA can activate mDCs into mature antigen presenting cells (mAPCs) which in turn present antigen epitopes with MHC-I molecules to naïve T cells. Coadministration of protein and synthetic dsRNA analogues can elicit an antigen-specific Th1-polarized immune response which stimulates the CD8+ CTL response and possibly dampen Th17 response. Synthetic dsRNA analogues have been tested as vaccine adjuvant against viral infections in animal models. However, a dsRNA receptor, TLR3 can be expressed in tumor cells while other members of TLR family, for example, TLR4 and TLR2 have been shown to promote tumor progression, metastasis, and chemoresistance. Thus, the promising potential of dsRNA analogues as a tumor therapeutic vaccine adjuvant should be evaluated cautiously.

Induction of potent cellular immune response in mice by hepatitis C virus NS3 protein with double-stranded RNA

Double-stranded RNA is produced during virus replication and, together with the viral antigen, is responsible for inducing host antivirus immunity. The hepatitis C virus (HCV) non-structural protein-3 (NS3) has been implicated in the immune evasion of HCV, and is one of the prime targets for inducing immunity against HCV infection. Mice were immunized with recombinant NS3 protein (rNS3) and poly (I:C) emulsified in Montanide ISA 720 (M720). Cytokine production was assayed by enzyme-linked immunospot assay, and CD4(+) IFN-gamma(+) T helper (Th) cells or CD8(+) IFN-gamma(+) cytotoxic T lymphocytes were detected by flow cytometry. Anti-NS3 titre and immunoglobulin G2a (IgG2a) and IgG1 levels were monitored by enzyme-linked immunosorbent assay. Administration of rNS3 formulated in poly (I:C) and M720 induced anti-NS3 titres with a predominantly IgG2a isotype comparable to those induced by rNS3 in CpG-ODN and M720. The cytokine profiles showed that this formulation induced a Th1-biased immune response with several-fold more interferon-gamma (IFN-gamma)-producing cells than interleukin-4-producing cells. In contrast, rNS3 in M720 induced a Th2-biased immune response. The frequency of IFN-gamma-producing CD4(+) and CD8(+) cells induced by rNS3 in poly (I:C) and M720 was significantly higher than that induced by rNS3, rNS3 in M720, or rNS3 in poly (I:C), and was comparable to that induced by rNS3 in CpG-ODN with M720. The antigen-specific CD8(+) T-cell immune response persisted for up to 7 months after immunization. In conclusion, poly (I:C) with rNS3 in M720 can elicit a strong and persistent Th1-biased immune response and a cytotoxic T-lymphocyte response through cross-priming in mice. This study highlighted a promising formulation for inducing an efficient cellular immune response against HCV that has potential for HCV vaccine development.

Induction of multispecific Th-1 type immune response against HCV in mice by protein immunization using CpG and Montanide ISA 720 as adjuvants

Recent studies demonstrate that Th1-type immune responses against a broad spectrum of hepatitis C virus (HCV) gene products are crucial to the resolution of acute HCV infection. We investigated new vaccine approaches to augment the strength of HCV-specific Th1-type immune responses. ELISPOT assay revealed that single or multiple protein immunization using both CpG ODN and Montanide ISA 720 as adjuvants induced much stronger IFN-gamma-producing Th1 responses against core, NS3 and NS5b targets than did the formulation without these adjuvants. Protein vaccination using CpG ODN and Montanide ISA 720 as adjuvants also greatly enhanced humoral responses to HCV core, E1/E2 and NS3. When specific IgG isotypes were assayed, protein immunization using CpG ODN and Montanide ISA 720 as adjuvants produced higher titers of IgG2a dominant antibodies than did protein immunization alone, indicating a more Th1-biased pathway. This increase in IgG2a is consistent with the induction of Th1 cells secreting IFN-gamma demonstrated by ELISPOT assay. In conclusion, protein immunization using CpG ODN and Montanide ISA 720 as adjuvants greatly enhanced cellular (Th1 type) as well as humoral immune responses against HCV in Balb/c mice. The use of adjuvants appears critical to the induction of Th1 immune responses during HCV vaccination with recombinant proteins.

Vigorous hepatitis C virus-specific CD4+ and CD8+ T cell responses induced by protein immunization in the presence of Montanide ISA720 plus synthetic oligodeoxynucleotides containing immunostimulatory cytosine-guanine dinucleotide motifs

BACKGROUND

A prophylactic vaccine for hepatitis C virus (HCV) requires generation of strong humoral as well as CD4(+) and CD8(+) T cell responses.

METHODS

The immunomodulatory effects of the combination of 2 adjuvants, synthetic oligodeoxynucleotides containing immunostimulatory cytosine-guanine dinucleotide motifs emulsified with Montanide ISA720 (M-ISA720/CpG), were investigated using the murine model.

RESULTS

Administration of recombinant HCV (rHCV) nonstructural (NS) 3 and NS5B proteins plus M-ISA720/CpG (hereafter, "M-ISA720/CpG/rHCV protein") induced high anti-NS3 and anti-NS5B immunoglobulin (Ig) G titers, with the IgG2a isotype being predominant. NS3- and NS5B-specific interferon (IFN)- gamma - and interleukin-2-producing CD4(+) T cell responses, as assessed by enzyme-linked immunospot assay, were significantly more vigorous in mice immunized with M-ISA720/CpG/rHCV protein than in control mice immunized without adjuvant. NS3- and NS5B-specific IFN- gamma -producing CD8(+) T cell percentages, as measured by direct ex vivo intracellular cytokine staining assay, were, respectively, a mean+/-SD of 0.14% +/- 0.04% and 0.15% +/- 0.05% in mice immunized with M-ISA720/CpG/rHCV protein. Furthermore, boosting with recombinant NS3 expression plasmid DNA after priming with M-ISA720/CpG-adjuvanted rNS3 strikingly enhanced both CD4(+) and CD8(+) T cell responses.

CONCLUSION

Immunization with M-ISA720/CpG/rHCV protein is capable of inducing potent humoral as well as HCV-specific T helper type 1-biased CD4(+) and CD8(+) T cell responses. A DNA boost after a protein prime--a reversal of the conventional approach--may provide an alternative path to the development of an effective HCV vaccine.

Reversibility of experimental rabbit liver cirrhosis by portal collagenase administration

The regression of cirrhosis is associated with increased intrahepatic collagenolytic enzyme activity. We investigated whether collagenase supplementation via portal vein infusion can retard cirrhosis development and/or reverse cirrhosis. In all, 35 rabbits were initially assigned to study. However, because of high surgical mortality and infection, only 15 animals completed study. Four normal controls (group I) received olive oil subcutaneously (SC) for 12 weeks followed by normal saline portal perfusion for 12 weeks. Four (group II) received CCl(4) SC for 6 weeks followed by portal vein collagenase, 6 mg twice weekly, plus SC CCl(4) for 6 additional weeks and then killed. Four rabbits (group III) received CCl(4) SC for 12 weeks and then 6 mg of collagenase portally for 12 weeks, while three control rabbits (group IV) received CCl(4) for 12 weeks followed by saline for 12 weeks. After 12 weeks of CCl(4), liver hydroxyproline content of collagenase-treated group II (361.1+/-106.6 microg/g) was significantly reduced compared with group III+IV that had not yet received collagenase (589.0+/-162.9 microg/g; P<0.05). In the main comparison, hydroxyproline content of collagenase-treated group III (177.5+/-35.6 microg/g) was significantly decreased compared with saline-treated controls (446.3+/-150.1 microg/g; P<0.01). Further, liver histology showed complete regression of cirrhosis in the collagenase-treated animals. No toxicity of liver, kidney, lung, brain or heart was observed histologically. Anaphylaxis occurred in 2/35 original animals (one fatal). In conclusion, this study provides 'proof of principle' that collagenase portal administration can retard cirrhosis development and speed regression of established cirrhosis in the rabbit CCl(4) model. Potential application to humans is premature, but feasible, if these findings are confirmed in additional animal studies.

Application of dsRNA in cancer immunotherapy: current status and future trends

Cancer cells create a microenvironment that prevents tumor rejection by the host's immune system. The activation of pattern recognition receptors (PRRs) can elicit an innate immune response and guide the adaptive immune response to overcome this. dsRNA analogs can trigger TLR3, RIG-I, MDA5, NLRP3 and several other PRRs to induce not only robust immune response against cancer but also programmed cell death. This review focuses on the signal pathways activated by dsRNA and examines examples of their clinical application in cancer treatment.

Multiple Factors Determine the Oncolytic or Carcinogenic Effects of TLRs Activation in Cancer

Toll‐like receptors (TLRs) belong to a germline‐encoded protein family. These are pattern recognition receptors. They sense pathogen‐associated molecular patterns (PAMPs). When this occurs, activation of the NF‐ĸB pathway follows. This triggers the innate immune response of the host. The consequent inflammatory cytokine response usually contributes to the elimination of the pathogen. Activation of TLRs also induces an adaptive immune response by a cross‐prime mechanism. This mechanism is employed in cancer immunotherapy. Using TLR ligands as adjuvants induces upregulation of costimulatory signals which in turn activates a cytotoxic leukocyte response against cancer cells. However, TLRs are also overexpressed in human cancer cells resulting in increased cell proliferation, migration, invasion, and angiogenesis. An intracellular adaptor, myeloid differentiation factor 88 (MyD88) probably mediates this process. MyD88 is intimately involved with all TLRs except TLR3. One consequence of the interaction between a TLR and MyD88 is activation of NF‐ĸB. In this context of a variety of proinflammtory cytokines being produced, chronic inflammation may result. Inflammation is an important protective mechanism. However, chronic inflammation is also involved in carcinogenesis. Activation of NF‐ĸB inhibits apoptosis and under certain circumstances, tumor cell survival. In this review, the potential therapeutic value of TLRs in immunotherapy and its role in oncogenesis are explored. The emerging use of artificial intelligence is mentioned.