Topical administration of HSV gD-IL-2 DNA is highly protective against murine herpetic stromal keratitis

Synergistic effects of oral inoculation with a recombinant Lactobacillus plantarum NC8 strain co-expressing interleukin-2 and interleukin-17B on the efficacy of the infectious bronchitis vaccine in chickens

Mucosal vaccination strategies are easier to implement than others in large-scale poultry farming. However, the adjuvants that are approved for veterinary use, which are predominantly aluminum- and oil-emulsion-based adjuvants, are not suitable for mucosal vaccination and carry a risk of adverse reactions. In this study, we engineered a novel Lactobacillus plantarum NC8 strain that co-expresses chicken interleukin-2 (IL-2) and IL-17B, which we designated NC8-ChIL2-17B, and evaluated its potential as an oral immunoadjuvant. The immunomodulatory properties of NC8-ChIL2-17B were evidenced by its ability to activate macrophages and inhibit the proliferation of infectious bronchitis virus (IBV) in vitro. We then confirmed its immunoadjuvant activity in vivo by orally administering NC8-ChIL2-17B along with a commercial IBV vaccine to chicks. The results indicated that NC8-ChIL2-17B enhanced the immune response elicited by the IBV vaccine and increased the levels of IBV-specific IgG and sIgA antibodies produced in response to IBV infection. Additionally, administration of NC8-ChIL2-17B promoted weight gain and beneficially modulated the gut microbiota, resulting in improved chicken performance. These findings suggest that oral administration of NC8-ChIL2-17B is a promising strategy to enhance the immune efficacy of the IBV vaccine in chickens, offering an efficacious alternative adjuvant.

Cytokines and their role as immunotherapeutics and vaccine Adjuvants: The emerging concepts

Cytokines are a protein family comprising interleukins, lymphokines, chemokines, monokines and interferons. They are significant constituents of the immune system, and they act in accordance with specific cytokine inhibiting compounds and receptors for the regulation of immune responses. Cytokine studies have resulted in the establishment of newer therapies which are being utilized for the treatment of several malignant diseases. The advancement of these therapies has occurred from two distinct strategies. The first strategy involves administrating the recombinant and purified cytokines, and the second strategy involves administrating the therapeutics which inhibits harmful effects of endogenous and overexpressed cytokines. Colony stimulating factors and interferons are two exemplary therapeutics of cytokines. An important effect of cytokine receptor antagonist is that they can serve as anti-inflammatory agents by altering the treatments of inflammation disorder, therefore inhibiting the effects of tumour necrosis factor. In this article, we have highlighted the research behind the establishment of cytokines as therapeutics and vaccine adjuvants, their role of immunotolerance, and their limitations.

Corneal gene therapy: Structural and mechanistic understanding

Cornea, a dome-shaped and transparent front part of the eye, affords 2/3rd refraction and barrier functions. Globally, corneal diseases are the leading cause of vision impairment. Loss of corneal function including opacification involve the complex crosstalk and perturbation between a variety of cytokines, chemokines and growth factors generated by corneal keratocytes, epithelial cells, lacrimal tissues, nerves, and immune cells. Conventional small-molecule drugs can treat mild-to-moderate traumatic corneal pathology but requires frequent application and often fails to treat severe pathologies. The corneal transplant surgery is a standard of care to restore vision in patients. However, declining availability and rising demand of donor corneas are major concerns to maintain ophthalmic care. Thus, the development of efficient and safe nonsurgical methods to cure corneal disorders and restore vision in vivo is highly desired. Gene-based therapy has huge potential to cure corneal blindness. To achieve a nonimmunogenic, safe and sustained therapeutic response, the selection of a relevant genes, gene editing methods and suitable delivery vectors are vital. This article describes corneal structural and functional features, mechanistic understanding of gene therapy vectors, gene editing methods, gene delivery tools, and status of gene therapy for treating corneal disorders, diseases, and genetic dystrophies.

Gene therapy in the anterior eye segment

This review provides comprehensive information about the advances in gene therapy in the anterior segment of the eye including cornea, conjunctiva, lacrimal gland, and trabecular meshwork. We discuss gene delivery systems including viral and non-viral vectors as well as gene editing techniques, mainly CRISPR-Cas9, and epigenetic treatments including antisense and siRNA therapeutics. We also provide a detailed analysis of various anterior segment diseases where gene therapy has been tested with corresponding outcomes. Disease conditions include corneal and conjunctival fibrosis and scarring, corneal epithelial wound healing, corneal graft survival, corneal neovascularization, genetic corneal dystrophies, herpetic keratitis, glaucoma, dry eye disease, and other ocular surface diseases. Although most of the analyzed results on the use and validity of gene therapy at the ocular surface have been obtained in vitro or using animal models, we also discuss the available human studies. Gene therapy approaches are currently considered very promising as emerging future treatments of various diseases, and this field is rapidly expanding.

Strategies for local gene therapy of corneal allograft rejection

Penetrating keratoplasty is the most common type of tissue transplant in humans. Irreversible immune rejection leads to loss of vision and graft failure. This complex immune response further predisposes future corneal transplants to rejection and failure. A diverse armamentarium of surgical and pharmacologic tools is available to improve graft survival. In this review, we will discuss the various gene therapeutic strategies aimed at potentiating the anterior chamber-associated immune deviation to extend graft survival.

Targeting herpetic keratitis by gene therapy

Ocular gene therapy is rapidly becoming a reality. By November 2012, approximately 28 clinical trials were approved to assess novel gene therapy agents. Viral infections such as herpetic keratitis caused by herpes simplex virus 1 (HSV-1) can cause serious complications that may lead to blindness. Recurrence of the disease is likely and cornea transplantation, therefore, might not be the ideal therapeutic solution. This paper will focus on the current situation of ocular gene therapy research against herpetic keratitis, including the use of viral and nonviral vectors, routes of delivery of therapeutic genes, new techniques, and key research strategies. Whereas the correction of inherited diseases was the initial goal of the field of gene therapy, here we discuss transgene expression, gene replacement, silencing, or clipping. Gene therapy of herpetic keratitis previously reported in the literature is screened emphasizing candidate gene therapy targets. Commonly adopted strategies are discussed to assess the relative advantages of the protective therapy using antiviral drugs and the common gene therapy against long-term HSV-1 ocular infections signs, inflammation and neovascularization. Successful gene therapy can provide innovative physiological and pharmaceutical solutions against herpetic keratitis.

Nasal-associated lymphoid tissue is not an absolute requirement for the induction of rat tear IgA antibody responses

PURPOSE/AIM OF STUDY: The purpose of this work was to determine whether rat nasal-associated lymphoid tissue is required for the induction of tear IgA responses.

MATERIALS AND METHODS

Particulate antigen in the form of DNP-BSA encapsulated in cationic microparticles was applied topically to the eyes (ocular topically) of rats that had the nasolacrimal ducts temporarily plugged with chromic gut suture material. Eye washes and serum were monitored for development of antigen specific IgA and IgG, respectively. To track the particulate uptake, fluorescent latex beads were applied topically to the eyes of plugged and unplugged animals. The nasal-associated lymphoid tissue and the draining lymph nodes were then examined for the presence of the fluorescent beads.

RESULTS

It was found that the chromic gut suture was effective in blocking the passage of antigen into the nasopharyngeal cavity for at least 24 hr. Tear antigen-specific IgA levels found in the eyes of plugged animals were not significantly lower from those of unplugged animals. Serum IgG antibody levels were also similar between the two groups. In animals with plugged nasolacrimal ducts, fluorescent beads were found predominately in the superficial cervical lymph nodes, which have been shown to drain the surface of the eye.

CONCLUSIONS

These results indicate that particulate antigen can be taken up by the conjunctiva and transported to the draining lymph nodes, showing that antigen does not need to access nasal-associated lymphoid tissue to induce tear IgA antibody responses.

Corneal gene therapy

Gene therapy to the cornea can potentially correct inherited and acquired diseases of the cornea. Factors that facilitate corneal gene delivery are the accessibility and transparency of the cornea, its stability ex vivo and the immune privilege of the eye. Initial corneal gene delivery studies characterized the relationship between intraocular modes of administration and location of reporter gene expression. The challenge of achieving effective topical gene transfer, presumably due to tear flow, blinking and low penetration of the vector through epithlelial tight junctions left no alternative but invasive administration to the anterior chamber and corneal stroma. DNA vaccination, RNA interference and gene transfer of cytokines, growth factors and enzymes modulated the corneal microenvironment. Positive results were obtained in preclinical studies for prevention and treatment of corneal graft rejection, neovascularization, haze and herpetic stromal keratitis. These studies, corneal gene delivery systems and modes of administration, and considerations regarding the choice of animal species used are the focus of this review. Opportunities in the field of corneal gene therapy lie in expanding the array of corneal diseases investigated and in the implementation of recent designs of safer vectors with reduced immunogenicity and longer duration of gene expression.

Ocular herpes simplex: changing epidemiology, emerging disease patterns, and the potential of vaccine prevention and therapy

PURPOSE

To review the changing epidemiology of herpes simplex virus infection, emerging patterns of herpetic ocular disease, and the challenges and promise of herpes simplex virus vaccine therapy.

DESIGN

Perspective.

METHODS

Literature review.

RESULTS

An epidemic increase in genital herpes simplex type 2 infection is reflected in a 30% increase in HSV-2 antibodies in the United States since 1976. Approximately one in four people in the United States over age 30 is infected with HSV-2. Primary acquisition of herpes simplex type 1 is becoming progressively delayed in many industrialized countries, in contrast to developing nations where the virus is acquired early in life and is ubiquitous. Changes in sexual behavior among young adults have been associated with a recent increase in genital HSV-1 infection, resulting from oral-genital rather than genital-genital contact. Clinical trials of HSV vaccines using selected herpes simplex virus type 2 proteins mixed in adjuvant have shown limited efficacy in seronegative women, but not in men.

CONCLUSIONS

The recent epidemic of genital herpes simplex type 2 infection is likely to result in an increase in neonatal ocular herpes and in delayed cases of acute retinal necrosis syndrome. The increase in genital HSV-1 may lead to industry production of vaccines that contain components of both HSV-1 and HSV-2 targeted toward limiting genital disease and transmission. As newer herpes simplex vaccines become available, ophthalmologists must be vigilant that a boost in immunity against HSV does not have a paradoxical effect in exacerbating break-through cases that develop immune-mediated herpes simplex stromal keratitis.

Gene therapy approaches to prolonging corneal allograft survival

Irreversible immunological rejection is the major cause of human corneal allograft failure and occurs despite the use of topical glucocorticoid immunosuppression. Systemic pharmacological interventions have not found widespread favour in corneal transplantation because of associated morbidities and inadequate demonstration of efficacy. Gene therapy offers tantalising prospects for improving corneal allograft survival, especially in those recipients at high risk of graft rejection. Donor corneas can be gene-modified ex vivo, while in storage prior to implantation, and the relative isolation of the transplanted cornea from the circulation decreases the risk of potential systemic complications. A wide variety of vectors have been found suitable for gene transfer to the cornea. The mechanisms involved in corneal graft rejection have been placed on a relatively secure footing over the past decade and in consequence a number of transgenes with promise for modulating rejection have been identified. However, relatively few studies have thus far demonstrated significant prolongation of corneal allograft survival after gene transfer to the donor cornea. In these instances, the therapeutic protein almost certainly acted at a proximal level in the afferent immune response, within the ocular environs.

Approaches to enhance the efficacy of DNA vaccines

DNA vaccines consist of antigen-encoding bacterial plasmids that are capable of inducing antigen-specific immune responses upon inoculation into a host. This method of immunization is advantageous in terms of simplicity, adaptability, and cost of vaccine production. However, the entry of DNA vaccines and expression of antigen are subjected to physical and biochemical barriers imposed by the host. In small animals such as mice, the host-imposed impediments have not prevented DNA vaccines from inducing long-lasting, protective humoral, and cellular immune responses. In contrast, these barriers appear to be more difficult to overcome in large animals and humans. The focus of this article is to summarize the limitations of DNA vaccines and to provide a comprehensive review on the different strategies developed to enhance the efficacy of DNA vaccines. Several of these strategies, such as altering codon bias of the encoded gene, changing the cellular localization of the expressed antigen, and optimizing delivery and formulation of the plasmid, have led to improvements in DNA vaccine efficacy in large animals. However, solutions for increasing the amount of plasmid that eventually enters the nucleus and is available for transcription of the transgene still need to be found. The overall conclusions from these studies suggest that, provided these critical improvements are made, DNA vaccines may find important clinical and practical applications in the field of vaccination.

Prospects for gene therapy in corneal disease

Transfer of cDNA to corneal cells has been accomplished using viral and nonviral vectors. Studies examining the feasibility and optimal methods for vector-mediated gene transfer to the cornea have, as in other tissues, been performed using histochemical or fluorescent marker genes. These have used corneal cells or cell lines in vitro, and whole corneas maintained in ex vivo culture. Gene-based interventions have been examined in specific corneal disorders such as allograft rejection, postexcimer laser scarring, and herpes simplex keratitis using experimental models. As the feasibility of genetic modification of corneal cells has been successfully demonstrated, there is great potential for gene therapy vectors in the treatment of human corneal disease. Continued improvements in vectors for gene transfer will improve the efficacy and safety of gene therapy. In addition to use of cDNA transfer as an alternative to drug or protein treatments in acquired corneal disorders, our expanding knowledge of the genetic basis of inherited corneal disorders will ultimately lead to the development of specific and effective gene therapies in this category of diseases.

Topical vaccination of DNA antigens: topical delivery of DNA antigens

Topical DNA vaccines have been shown to elicit both broad humoral and cellular immune responses in vivo. The skin is an attractive site for the delivery of DNA antigens for DNA vaccination. However, due to skin's barrier properties, the penetration of DNA and the applications of topical vaccination are limited. To improve permeability, chemical and physical approaches have been examined to decrease stratum corneum barrier properties. Topical vaccination has been achieved using topical application of naked DNA, DNA/liposomes or emulsion complex, liposomal cream, as well as physical methods such as stripping, electroporation, and micromechanical disruption methods. All methods resulted in a significant enhancement in humoral and cellular immune responses over naked DNA alone. To develop more cost-effective and needle-free vaccines, skin-targeted immunizations are required. This review focuses on the chemical and physical methods developed to enhance DNA delivery into skin.