Oral-mucosal administration of IFN-alpha potentiates immune response in mice

Therapeutic and Prophylactic Use of Oral, Low-Dose IFNs in Species of Veterinary Interest: Back to the Future

Cytokines are important molecules that orchestrate the immune response. Given their role, cytokines have been explored as drugs in immunotherapy in the fight against different pathological conditions such as bacterial and viral infections, autoimmune diseases, transplantation and cancer. One of the problems related to their administration consists in the definition of the correct dose to avoid severe side effects. In the 70s and 80s different studies demonstrated the efficacy of cytokines in veterinary medicine, but soon the investigations were abandoned in favor of more profitable drugs such as antibiotics. Recently, the World Health Organization has deeply discouraged the use of antibiotics in order to reduce the spread of multi-drug resistant microorganisms. In this respect, the use of cytokines to prevent or ameliorate infectious diseases has been highlighted, and several studies show the potential of their use in therapy and prophylaxis also in the veterinary field. In this review we aim to review the principles of cytokine treatments, mainly IFNs, and to update the experiences encountered in animals.

Non-Lethal Sequential Individual Monitoring of Viremia in Relation to DNA Vaccination in Fish-Example Using a Salmon Alphavirus DNA Vaccine in Atlantic Salmon Salmo salar

Traditionally, commercial testing for vaccine efficacy has relied on the mass infection of vaccinated and unvaccinated animals and the comparison of mortality prevalence and incidence. For some infection models where disease does not cause mortality this approach to testing vaccine efficacy is not useful. Additionally, in fish experimental studies on vaccine efficacy and immune response the norm is that several individuals are lethally sampled at sequential timepoints, and results are extrapolated to represent the kinetics of immune and disease parameters of an individual fish over the entire experimental infection period. In the present study we developed a new approach to vaccine testing for viremic viruses in fish by following the same individuals over the course of a DNA vaccination and experimental infection through repeated blood collection and analyses. Injectable DNA vaccines are particularly efficient against viral disease in fish. To date, two DNA vaccines have been authorised for use in fish farming, one in Canada against Infectious Haemorrhagic Necrotic virus and more recently one in Europe against Salmon Pancreatic Disease virus (SPDv) subtype 3. In the current study we engineered and used an experimental DNA vaccine against SPDv subtype 1. We measured viremia using a reporter cell line system and demonstrated that the viremia phase was completely extinguished following DNA vaccination. Differences in viremia infection kinetics between fish in the placebo group could be related to subsequent antibody levels in the individual fish, with higher antibody levels at terminal sampling in fish showing earlier viremia peaks. The results indicate that sequential non-lethal sampling can highlight associations between infection traits and immune responses measured at asynchronous timepoints and, can provide biological explanations for variation in data. Similar to results observed for the SPDv subtype 3 DNA vaccine, the SPDv subtype 1 DNA vaccine also induced an interferon type 1 response after vaccination and provided high protection against SPDv under laboratory conditions when fish were challenged at 7 weeks post-vaccination.

Association between Interferon Response and Protective Efficacy of NS1-Truncated Mutants as Influenza Vaccine Candidates in Chickens

Influenza virus mutants that encode C-terminally truncated NS1 proteins (NS1-truncated mutants) are attractive candidates for avian live attenuated influenza vaccine (LAIV) development because they are both attenuated and immunogenic in chickens. We previously showed that a high protective efficacy of NS1-truncated LAIV in chickens corresponds with induction of high levels of type I interferon (IFN) responses in chicken embryonic fibroblast cells. In this study, we investigated the relationship between induction of IFN and IFN-stimulated gene responses in vivo and the immunogenicity and protective efficacy of NS1-truncated LAIV. Our data demonstrates that accelerated antibody induction and protective efficacy of NS1-truncated LAIV correlates well with upregulation of IFN-stimulated genes. Further, through oral administration of recombinant chicken IFN alpha in drinking water, we provide direct evidence that type I IFN can promote rapid induction of adaptive immune responses and protective efficacy of influenza vaccine in chickens.

In vivo assessment of NS1-truncated influenza virus with a novel SLSYSINWRH motif as a self-adjuvanting live attenuated vaccine

Mutants of influenza virus that encode C-terminally truncated NS1 proteins (NS1-truncated mutants) characteristically induce high interferon responses. The dual activity of interferon in blocking virus replication and enhancing the development of adaptive immune responses makes these mutants promising as self-adjuvanting live-attenuated influenza vaccine (LAIV) candidates. Yet, among the NS1-truncated mutants, the length of NS1 is not directly correlated with the interferon-inducing efficiency, the level of attenuation, or effectiveness as LAIV. Using quantitative in vitro biologically active particle subpopulation analysis as a tool to identify potential LAIV candidates from a pool of NS1-truncated mutants, we previously predicted that a NS1-truncated mutant pc2, which was less effective as a LAIV in chickens, would be sufficiently effective as a LAIV in mammalian hosts. In this study, we confirmed that pc2 protected mice and pigs against heterologous virus challenge in terms of preventing clinical signs and reducing virus shedding. pc2 expresses a unique SLSYSINWRH motif at the C-terminus of its truncated NS1. Deletion of the SLSYSINWRH motif led to ~821-fold reduction in the peak yield of type I interferon induced in murine cells. Furthermore, replacement of the SLSYSINWRH motif with the wildtype MVKMDQAIMD sequence did not restore the interferon-inducing efficiency. The diminished interferon induction capacity in the absence of the SLSYSINWRH motif was similar to that observed in other mutants which are less effective LAIV candidates. Remarkably, pc2 induced 16-fold or more interferon in human lung and monkey kidney cells compared to the temperature-sensitive, cold-adapted Ann Arbor virus that is currently used as a master backbone for LAIVs such as FluMist. Although the mechanism by which the SLSYSINWRH motif regulates the vaccine properties of pc2 has not been elucidated, this motif has potential use in engineering self-adjuvanting NS1-truncated-based LAIVs.

In vitro analysis of virus particle subpopulations in candidate live-attenuated influenza vaccines distinguishes effective from ineffective vaccines

Two effective (vac+) and two ineffective (vac-) candidate live-attenuated influenza vaccines (LAIVs) derived from naturally selected genetically stable variants of A/TK/OR/71-delNS1[1-124] (H7N3) that differed only in the length and kind of amino acid residues at the C terminus of the nonstructural NS1 protein were analyzed for their content of particle subpopulations. These subpopulations included total physical particles (measured as hemagglutinating particles [HAPs]) with their subsumed biologically active particles of infectious virus (plaque-forming particles [PFPs]) and different classes of noninfectious virus, namely, interferon-inducing particles (IFPs), noninfectious cell-killing particles (niCKPs), and defective interfering particles (DIPs). The vac+ variants were distinguished from the vac- variants on the basis of their content of viral subpopulations by (i) the capacity to induce higher quantum yields of interferon (IFN), (ii) the generation of an unusual type of IFN-induction dose-response curve, (iii) the presence of IFPs that induce IFN more efficiently, (iv) reduced sensitivity to IFN action, and (v) elevated rates of PFP replication that resulted in larger plaques and higher PFP and HAP titers. These in vitro analyses provide a benchmark for the screening of candidate LAIVs and their potential as effective vaccines. Vaccine design may be improved by enhancement of attributes that are dominant in the effective (vac+) vaccines.

Opening the flood gates: interferon-alpha treatment for Sjögren's syndrome

Interferon (IFN)-alpha is the main IFN produced in response to viral infection. Low levels of IFNalpha can be detected in nasal secretions after exposure to viruses in vivo. Radioimmunoassay has shown that endogenous IFNalpha is low in children, reaches a peak in young adults, and gradually declines with aging. Importantly, this endogenous IFNalpha is significantly decreased in patients with Sjögren's syndrome (SS). IFNalpha has been tested as a therapeutic agent in patients with SS. Intramuscular human leucocyte IFNalpha increases saliva production significantly in patients with SS. Improvements have been noted in lacrimal function and in dryness symptoms. Since IFNalpha infrequently induces autoimmune phenomena and high dose IFNalpha treatment sometimes has a serious adverse event profile, treatment focus has shifted to use of low dose orally-administered IFNalpha. In a single-masked controlled trial, 60 patients with SS randomly received natural human IFNalpha 150IU 3 times a day in an oral lozenge formulation or sucralfate as control for 6 months. At study end, 15 (50%) of the 30 IFNalpha-treated patients had saliva production increases at least 100% above baseline. IFNalpha treatment was well tolerated and no patients withdrew. Labial minor salivary gland biopsies indicated significant decreases in lymphocytic infiltration accompanied by a significant increase in intact salivary gland tissue after 6 months of treatment. In another 12-week double-masked, randomised, placebo-controlled trial, stimulated saliva production in patients with SS receiving IFNalpha lozenges 150IU 3 times daily was significantly increased. This dosage was also suggestive of benefit for 5 of 7 subjective measures of oral and ocular comfort. The tolerability profile of these low dose oral IFNalpha lozenges is excellent; no serious adverse events have been recorded. Adverse effects were generally mild and there were no clinically significant changes in laboratory or clinical safety measures. Low oral doses of natural human IFNalpha thus appear to improve secretory function and relieve dryness in patients with SS without causing significant adverse events. Endogenous or orally administered IFNalpha may activate oropharyngeal lymphoid and epithelial cells and induce production of potent soluble factors which could mediate immunological reactivity. It has been suggested that IFNalpha/beta potentiates clonal expansion and survival of CD8 T cells. Stimulating effects have also been demonstrated on natural killer cell activity, which has been shown to be depressed in patients with SS. It is likely that some combination of these immunological effects results in anti-inflammatory activity and ameliorates signs and symptoms of SS.

The role of IFN-alpha as homeostatic agent in the inflammatory response: a balance between danger and response?

Interferon-alpha (IFN-alpha) is thought of by most immunologists as a fundamental component of the antiviral innate immune response, with other, accessory properties. Several lines of evidence point to a fundamental reappraisal of this conceptual framework because it may neglect other crucial functions of this cytokine under both health and disease conditions. Among these, a regulatory role in the inflammatory response is probably of paramount importance, as shown by in vivo and in vitro studies on humans, pets, and farm and laboratory animals. This role would not conflict with the main functions of IFN-alpha in the innate immune system and would complement these in line with major, evolution-based needs of the host. A hinge role of IFN-alpha between innate and adaptive immunity was recognized in the past on the basis of compelling evidence. This concept should now be widened; not only does IFN-alpha act to trigger, amplify, and sustain the different phases of the immune response, but it could also promote a substantial balance between danger and inflammatory response when an infectious challenge is either declining or completely over.

Effects of IFN-α on the Inflammatory Response of Swine Leukocytes to Bacterial Endotoxin

Because low-dose interferon-alpha (IFN-alpha) treatment had proved effective in several models of chronic inflammation and autoimmune disease, a possible role of IFN-alpha in modulating the response of swine leukocytes to bacterial endotoxin was investigated in this study. Exposure of swine peripheral blood mononuclear cells (PBMC) to low concentrations of human IFN-alpha caused a strong, dose-dependent decrease in CD14 expression, the lowest level being observed at 5 U/ml IFN-alpha. This result was confirmed if PBMC were later exposed to purified lipopolysaccharide (LPS). A 10-fold lower IFN-alpha concentration (0.5 U/ml) caused the largest reduction of tumor necrosis factor-alpha (TNF-alpha) accumulation in the medium of pulmonary alveolar macrophages (PAM), stimulated with bacterial LPS. At 0.5 U/ml, the expression of the TNF-alpha gene in PAM was also strongly reduced, as opposed to cells pretreated with 50 U/ml IFN-alpha. In contrast, expression of the interleukin-1beta (IL- 1beta) gene was stimulated and that of the IL-6 gene was not significantly affected at both IFN-alpha concentrations. Results point to an important role of IFN-alpha in control of the inflammatory response to bacterial endotoxin in pigs.

Ingested type I interferon: a potential treatment for autoimmunity

We have proposed a unifying hypothesis of the etiopathogenesis of autoimmunity that defines autoimmunity as a type I interferon (IFN) immunodeficiency syndrome. We have examined toxicity and potential efficacy in three phase I (type 1 diabetes, rheumatoid arthritis, multiple sclerosis) and one phase II clinical trials in multiple sclerosis (MS). In a phase I open-label trial in type 1 diabetes, ingested IFN-alpha preserved residual beta cell function in recent onset patients. In a second phase I trial, treatment of rheumatoid arthritis (RA) with ingested IFN-alpha reduced the secretion of interleukin-1 (IL-1), a proinflammatory cytokine. In a third phase I trial in MS, there was a significant decrease in peripheral blood mononuclear cell (PBMC) IL-2 and IFN-gamma production after ingesting IFN-alpha. In a phase II randomized, placebo-controlled, double-blind trial in MS, 10,000 IU ingested IFN-alpha significantly decreased gadolinium enhancements compared with the placebo group at month 5. Tumor necrosis factor-alpha (TNF-alpha) and IFN-gamma cytokine secretion in the 10,000 IU group at month 5 showed a significant decrease that corresponded with the effect of ingested IFN-alpha on decreasing gadolinium enhancements. Ingested IFN-alpha was not toxic in any of these clinical trials. These studies suggest that ingested IFN-alpha may have a potential role in the treatment of autoimmunity.

The oropharyngeal delivery of interferons: where are we and where do we need to go?

The controversial concept of oral delivery of interferon (IFN) is reviewed in relation to possible mechanisms of action. Although there is a rational basis and some positive clinical results for believing that it may work, problems remain to understand which is the most effective IFN preparation and why. Owing to a minimal cost and lack of toxicity, the oral as well as other unconventional routes of IFN delivery deserve to be evaluated because they may become useful.

Autoimmunity is a type I interferon-deficiency syndrome corrected by ingested type I IFN via the GALT system

Type I interferons (IFN-alpha/beta), products of the innate immune system, can modulate immune function whereas proinflammatory IFN-gamma (type II IFN), a product of the acquired immune system upregulates inflammation and enhances cell mediated immunity. We have proposed a unifying hypothesis of the origin of autoimmunity as a type I IFN immunodeficiency syndrome involving inadequate regulation of the acquired immune system product IFN-gamma by the IFN-alpha/beta innate immune system. The common theme of ingested type I IFNs in autoimmunity is inhibition of proinflammatory type II IFN systemically or at the target organ. In multiple sclerosis (MS) and insulin-dependent diabetes mellitus (IDDM) at the target organ, and in rheumatoid arthritis (RA) as a regulator of other proinflammatory cytokines, IFN-gamma is the nexus of inflammation in autoimmunity. Ingested type I IFNs counteract type II IFN, overcome the relative lack of type I IFN activity, and ameliorate autoimmunity. The administration of type I IFNs (IFN-alpha/beta) via the gut offers an exciting alternative to systemic application for overcoming the type I IFN immunodeficiency in autoimmunity. Successful use of ingested type I IFN in three separate prototypical autoimmune diseases suggests a broad antiinflammatory therapeutic profile for this technology.

Oral use of interferon

Interferon-alpha (IFN-alpha) given orally has biological activity in humans and other animals. The dose providing the most benefit delivers IFN-alpha to the oral mucosa in a concentration (10(2)-10(3) IU), similar to that naturally produced in the nasal secretions during respiratory infections. In contrast, conventional IFN therapy employs parenteral doses of > 10(6) IU and, for this reason, orally administered IFN therapies have been called low-dose treatments. Efficacy in both animal disease models and human studies has been reported, and the mechanisms whereby oral administration has a systemic effect are under active study in a number of laboratories.

Suppression of late asthmatic response by low-dose oral administration of interferon-beta in the guinea pig model of asthma

We investigated the anti-asthmatic effects of low-dose oral and subcutaneous administration of interferon-beta (IFN-beta) on an ovalbumin (OVA)-sensitized and challenged guinea pig model of asthma. Subcutaneous administration of IFN-beta suppressed the eosinophil infiltration by 14.2% of the control and the respiratory resistance (Rrs) by 58.2% at 2.0 MIU/kg. Oral administration of IFN-beta inhibited the late asthmatic response (LAR) by suppressing the increase of Rrs by 29% of the control at 1 IU/ml and the eosinophil infiltration into the trachea and lung by 34.6% at the optimum dosage of 10 IU/ml. Both subcutaneous and oral administration could not inhibit the early asthmatic response (EAR). Additionally we found 2',5'-oligoadenylate synthetase (2',5'-OAS) induction by low-dose oral administration (LDOA) of IFN-beta to the same extent as by subcutaneous administration in whole blood in vivo. These data suggest that LDOA of IFN-beta would have some clinical benefit for patients with asthma.

Ectopic Expression of DNA Encoding IFN-α1 in the Cornea Protects Mice from Herpes Simplex Virus Type 1-Induced Encephalitis

A novel approach to combat acute herpes simplex virus type 1 (HSV-1) infection has recently been developed by administration with a plasmid DNA construct encoding cytokine genes. Cytokines, especially type I IFNs (IFN-α and IFN-β) play an important role in controlling acute HSV-1 infection. The purpose of the present study was to investigate the potential efficacy of ectopically expressed IFN-α1 against ocular HSV-1 infection following in situ transfection of mouse cornea with a naked IFN-α1-containing plasmid DNA. Topical administration of the IFN-α1 plasmid DNA exerted protection against ocular HSV-1 challenge in a time- and dose-dependent manner and antagonized HSV-1 reactivation. In addition, IFN-α1-transfected eyes expressed a fivefold increase in MHC class I mRNA over vector-treated controls. The protective efficacy of the IFN-α1 transgene antagonized viral replication, as evidenced by the reduction of the viral gene transcripts (infected cell polypeptide 27, thymidine kinase, and viral protein 16) and viral load in eyes and trigeminal ganglia during acute infection. The administration of neutralizing Ab to IFN-αβ antagonized the protective effect of the IFN-α1 transgene in mice. Collectively, these findings demonstrate the potential of using naked plasmid DNA transfection in the eye to achieve ectopic gene expression of therapeutically active agents.