Potent adjuvant activity of cationic liposome-DNA complexes for genital herpes vaccines

Identification of potent HSV antivirals using 3D bioprinted human skin equivalents

Herpes simplex virus (HSV) infection has worldwide public health concerns and lifelong medical impacts. The standard therapy, acyclovir, has limited efficacy in preventing HSV subclinical virus shedding, and drug resistance occurs in immunocompromised patients, highlighting the need for novel therapeutics. HSV infection manifests in the skin epidermal layer, but current drug discovery utilizes Vero cells and fibroblasts monolayer cultures, capturing neither in vivo relevance nor tissue environment. To bridge the gap, we established 3D bioprinted human skin equivalents that recapitulate skin architecture in a 96-well plate format amenable for antiviral screening and preclinical testing. Screening a library of 738 compounds with broad targets and mechanisms of action, we identified potent antivirals, including most of the known anti-HSV compounds, validating the translational relevance of our assay. Acyclovir was dramatically less potent for inhibiting HSV in keratinocytes compared to donor-matched fibroblasts. In contrast, antivirals against HSV helicase/primase or host replication pathways displayed similar potency across cell types and donor sources in 2D and 3D models. The reduced potency of acyclovir in keratinocytes, the primary cell type encountered by HSV reactivation, helps explain the limited benefit acyclovir and its congeners play in reducing sexual transmission. Finally, we demonstrated that our 3D bioprinted skin platform can integrate patient-derived cells, facilitating the incorporation of variable genetic backgrounds early into drug testing. Thus, these data indicate that the 3D bioprinted human skin equivalent assay platform provides a more physiologically relevant approach to identifying potential antivirals for HSV-directed drug development.

Alphaherpesvirus Vaccines

Prophylactic and therapeutic vaccines for the alphaherpesviruses including varicella zoster virus (VZV) and herpes simplex virus types 1 and 2 have been the focus of enormous preclinical and clinical research. A live viral vaccine for prevention of chickenpox and a subunit therapeutic vaccine to prevent zoster are highly successful. In contrast, progress towards the development of effective prophylactic or therapeutic vaccines against HSV-1 and HSV-2 has met with limited success. This review provides an overview of the successes and failures, the different types of immune responses elicited by various vaccine modalities, and the need to reconsider the preclinical models and immune correlates of protection against HSV.

A cationic liposome-DNA complexes adjuvant (JVRS-100) enhances the immunogenicity and cross-protective efficacy of pre-pandemic influenza A (H5N1) vaccine in ferrets

Influenza A (H5N1) viruses continue to pose a public health threat. As inactivated H5N1 vaccines are poorly immunogenic, adjuvants are needed to improve the immunogenicity of H5N1 vaccine in humans. Here, we investigated the immunogenicity and cross-protective efficacy in ferrets of a clade 2.2-derived vaccine with addition of JVRS-100, an adjuvant consisting of cationic liposome-DNA complexes (CLDC). After the first vaccination, significantly higher levels of hemagglutination-inhibition (HAI) and neutralizing antibody titers were detected in ferrets immunized with adjuvanted vaccine compared to unadjuvanted vaccine. Following a second dose of adjuvanted vaccine, HAI antibody titers of ≥ 40 were detected against viruses from multiple H5N1 clades. HAI antibodies against newly isolated H5N2 and H5N8 viruses were also augmented by JVRS-100. Ferrets were challenged with a heterologous H5N1 virus. All ferrets that received two doses of adjuvanted vaccine exhibited mild illness, significantly reduced nasal wash virus titers and protection from lethal challenge. In contrast, ferrets that received unadjuvanted vaccine showed greater weight loss, high viral titers and 3 of 6 animals succumbed to the lethal challenge. Our results indicate that the addition of JVRS-100 to H5N1 vaccine enhanced immunogenicity and cross-protection against lethal H5N1 virus disease in ferrets. JVRS-100 warrants further investigation as a potential adjuvant for influenza vaccines.

HSV-2 vaccine: current status and insight into factors for developing an efficient vaccine

Herpes simplex virus type 2 (HSV-2), a globally sexually transmitted virus, and also one of the main causes of genital ulcer diseases, increases susceptibility to HIV-1. Effective vaccines to prevent HSV-2 infection are not yet available, but are currently being developed. To facilitate this process, the latest progress in development of these vaccines is reviewed in this paper. A summary of the most promising HSV-2 vaccines tested in animals in the last five years is presented, including the main factors, and new ideas for developing an effective vaccine from animal experiments and human clinical trials. Experimental results indicate that future HSV-2 vaccines may depend on a strategy that targets mucosal immunity. Furthermore, estradiol, which increases the effectiveness of vaccines, may be considered as an adjuvant. Therefore, this review is expected to provide possible strategies for development of future HSV-2 vaccines.

Learning from the messengers: innate sensing of viruses and cytokine regulation of immunity - clues for treatments and vaccines

Virus infections are a major global public health concern, and only via substantial knowledge of virus pathogenesis and antiviral immune responses can we develop and improve medical treatments, and preventive and therapeutic vaccines. Innate immunity and the shaping of efficient early immune responses are essential for control of viral infections. In order to trigger an efficient antiviral defense, the host senses the invading microbe via pattern recognition receptors (PRRs), recognizing distinct conserved pathogen-associated molecular patterns (PAMPs). The innate sensing of the invading virus results in intracellular signal transduction and subsequent production of interferons (IFNs) and proinflammatory cytokines. Cytokines, including IFNs and chemokines, are vital molecules of antiviral defense regulating cell activation, differentiation of cells, and, not least, exerting direct antiviral effects. Cytokines shape and modulate the immune response and IFNs are principle antiviral mediators initiating antiviral response through induction of antiviral proteins. In the present review, I describe and discuss the current knowledge on early virus–host interactions, focusing on early recognition of virus infection and the resulting expression of type I and type III IFNs, proinflammatory cytokines, and intracellular antiviral mediators. In addition, the review elucidates how targeted stimulation of innate sensors, such as toll-like receptors (TLRs) and intracellular RNA and DNA sensors, may be used therapeutically. Moreover, I present and discuss data showing how current antimicrobial therapies, including antibiotics and antiviral medication, may interfere with, or improve, immune response.

Cationic liposomal vaccine adjuvants in animal challenge models: overview and current clinical status

Cationic liposome formulations can function as efficient vaccine adjuvants. However, due to the highly diverse nature of lipids, cationic liposomes have different physical-chemical characteristics that influence their adjuvant mechanisms and their relevance for use in different vaccines. These characteristics can be further manipulated by incorporation of additional lipids or stabilizers, and inclusion of carefully selected immunostimulators is a feasible strategy when tailoring cationic liposomal adjuvants for specific disease targets. Thus, cationic liposomes present a plasticity, which makes them promising adjuvants for future vaccines. This versatility has also led to a vast amount of literature on different experimental liposomal formulations in combination with a wide range of immunostimulators. Here, we have compiled information about the animal challenge models and administration routes that have been used to study vaccine adjuvants based on cationic liposomes and provide an overview of the applicability, progress and clinical status of cationic liposomal vaccine adjuvants.

HSV-1-induced chemokine expression via IFI16-dependent and IFI16-independent pathways in human monocyte-derived macrophages

Background

Innate recognition is essential in the antiviral response against infection by herpes simplex virus (HSV). Chemokines are important for control of HSV via recruitment of natural killer cells, T lymphocytes, and antigen-presenting cells. We previously found that early HSV-1-mediated chemokine responses are not dependent on TLR2 and TLR9 in human macrophages. Here, we investigated the role of the recently identified innate IFN-inducible DNA receptor IFI16 during HSV-1 infection in human macrophages.

Methods

Peripheral blood mononuclear cells were purified from buffy coats and monocytes were differentiated to macrophages. Macrophages infected with HSV-1 were analyzed using siRNA-mediated knock-down of IFI16 by real-time PCR, ELISA, and Western blotting.

Results

We determined that both CXCL10 and CCL3 are induced independent of HSV-1 replication. IFI16 mediates CCL3 mRNA accumulation during early HSV-1 infection. In contrast, CXCL10 was induced independently of IFI16.

Conclusions

Our data provide the first evidence of HSV-1-induced innate immune responses via IFI16 in human primary macrophages. In addition, the data suggest that at least one additional unidentified receptor or innate sensing mechanism is involved in recognizing HSV-1 prior to viral replication.

Cationic liposome-DNA complexes (CLDC) adjuvant enhances the immunogenicity and cross-protective efficacy of a pre-pandemic influenza A H5N1 vaccine in mice

The development of pre-pandemic influenza A H5N1 vaccines that confer both antigen-sparing and cross-clade protection are a high priority given the limited worldwide capacity for influenza vaccine production, and the antigenic and genetic heterogeneity of circulating H5N1 viruses. The inclusion of potent adjuvants in vaccine formulations may achieve both of these aims. Here we show that the addition of JVRS-100, an adjuvant consisting of cationic liposome-DNA complexes (CLDC) to a clade 1-derived H5N1 split vaccine induced significantly higher virus-specific antibody than unadjuvanted formulations, with a >30-fold dose-sparing effect and induction of increased antigen-specific CD4(+) T-cell responses in mice. All mice that received one dose of adjuvanted vaccine and subsequent H5N1 viral challenges exhibited mild illness, lower lung viral titers, undetectable spleen and brain viral titers, and 100% survival after either homologous clade 1 or heterologous clade 2 H5N1 viral challenges, whereas unadjuvanted vaccine recipients showed significantly increased weight loss, viral titers, and mortality. The protective immunity induced by JVRS-100 adjuvanted H5N1 vaccine was shown to last for over one year without significant waning. Thus, JVRS-100 adjuvanted H5N1 vaccine elicited enhanced humoral and T-cell responses, dose-sparing, and cross-clade protection in mice. CLDC holds promise as an adjuvant for human pre-pandemic inactivated H5N1 vaccines.

Sensing herpes: more than toll

To launch an effective antiviral immune response, cells must recognize the virus, activate a cytokine response, and initiate inflammatory processes. Herpes simplex virus 1 (HSV-1) and HSV-2 are nuclear-replicating viruses composed of a double-stranded DNA genome plus glycoproteins that are incorporated into a lipid bilayer envelope that surrounds an icosahedral capsid. Several novel receptors that mediate innate recognition of HSV and that activate the innate immune response have been identified in recent years. The host-virus interactions that lead to type I interferon (IFN), type III IFN, and cytokine production include cellular recognition of viral envelope and structural proteins, recognition of viral genomic DNA and recognition of virus-derived double-stranded RNAs. Such RNAs can interact with cellular pattern-recognition receptors, including Toll-like receptors and a number of cytoplasmic and nuclear receptors for virus DNA and virus-derived RNAs. In this review, I present a systematic overview of innate cellular recognition of HSV infection that leads to immune activation, and I discuss the implications of the known cell-host interactions. In addition, I discuss the use of innate stimulation to improve anti-HSV treatment and vaccine response and I discuss future research aims.

Cationic liposomes as vaccine adjuvants

The application of cationic liposomes as vaccine delivery systems and adjuvants has been investigated extensively over the last few decades. However, cationic liposomes are, in general, not sufficiently immunostimulatory, which is why the combination of liposomes with immunostimulating ligands has arisen as a strategy in the development of novel adjuvant systems. Within the last 5 years, two novel adjuvant systems based on cationic liposomes incorporating Toll-like receptor or non-Toll-like receptor immunostimulating ligands have progressed from preclinical testing in smaller animal species to clinical testing in humans. The immune responses that these clinical candidates induce are primarily of the Th1 type for which there is a profound unmet need. Furthermore, a number of new cationic liposome-forming surfactants with notable immunostimulatory properties have been discovered. In this article we review the recent progress on the application of cationic liposomes as vaccine delivery systems/adjuvants.

Mucosal immunization with liposome-nucleic acid adjuvants generates effective humoral and cellular immunity

Development of effective new mucosal vaccine adjuvants has become a priority with the increase in emerging viral and bacterial pathogens. We previously reported that cationic liposomes complexed with non-coding plasmid DNA (CLDC) were effective parenteral vaccine adjuvants. However, little is known regarding the ability of liposome-nucleic acid complexes to function as mucosal vaccine adjuvants, or the nature of the mucosal immune responses elicited by mucosal liposome-nucleic acid adjuvants. To address these questions, antibody and T cell responses were assessed in mice following intranasal immunization with CLDC-adjuvanted vaccines. The effects of CLDC adjuvant on antigen uptake, trafficking, and cytokine responses in the airways and draining lymph nodes were also assessed. We found that mucosal immunization with CLDC-adjuvanted vaccines effectively generated potent mucosal IgA antibody responses, as well as systemic IgG responses. Notably, mucosal immunization with CLDC adjuvant was very effective in generating strong and sustained antigen-specific CD8(+) T cell responses in the airways of mice. Mucosal administration of CLDC vaccines also induced efficient uptake of antigen by DCs within the mediastinal lymph nodes. Finally, a killed bacterial vaccine adjuvanted with CLDC induced significant protection from lethal pulmonary challenge with Burkholderia pseudomallei. These findings suggest that liposome-nucleic acid adjuvants represent a promising new class of mucosal adjuvants for non-replicating vaccines, with notable efficiency at eliciting both humoral and cellular immune responses following intranasal administration.

A live-attenuated HSV-2 ICP0 virus elicits 10 to 100 times greater protection against genital herpes than a glycoprotein D subunit vaccine

Glycoprotein D (gD-2) is the entry receptor of herpes simplex virus 2 (HSV-2), and is the immunogen in the pharmaceutical industry's lead HSV-2 vaccine candidate. Efforts to prevent genital herpes using gD-2 subunit vaccines have been ongoing for 20 years at a cost in excess of $100 million. To date, gD-2 vaccines have yielded equivocal protection in clinical trials. Therefore, using a small animal model, we sought to determine if a live-attenuated HSV-2 ICP0⁻ virus would elicit better protection against genital herpes than a gD-2 subunit vaccine. Mice immunized with gD-2 and a potent adjuvant (alum+monophosphoryl lipid A) produced high titers of gD-2 antibody. While gD-2-immunized mice possessed significant resistance to HSV-2, only 3 of 45 gD-2-immunized mice survived an overwhelming challenge of the vagina or eyes with wild-type HSV-2 (MS strain). In contrast, 114 of 115 mice immunized with a live HSV-2 ICP0⁻ virus, 0ΔNLS, survived the same HSV-2 MS challenges. Likewise, 0ΔNLS-immunized mice shed an average 125-fold less HSV-2 MS challenge virus per vagina relative to gD-2-immunized mice. In vivo imaging demonstrated that a luciferase-expressing HSV-2 challenge virus failed to establish a detectable infection in 0ΔNLS-immunized mice, whereas the same virus readily infected naïve and gD-2-immunized mice. Collectively, these results suggest that a HSV-2 vaccine might be more likely to prevent genital herpes if it contained a live-attenuated HSV-2 virus rather than a single HSV-2 protein.

Effects of herpes simplex virus type 2 glycoprotein vaccines and CLDC adjuvant on genital herpes infection in the guinea pig

Genital herpes simplex virus (HSV) infections are common but results from vaccine trials with HSV-2 glycoprotein D (gD) have been disappointing. We therefore compared a similar HSV gD2 vaccine, to a further truncated gD2 vaccine, to a vaccine with gD2 plus gB2 and gH2/gL2 and to a vaccine with only gB2 and gH2/gL2 in a guinea pig model of genital herpes. All vaccines were administered with cationic liposome-DNA complexes (CLDC) as an adjuvant. All vaccines significantly decreased the severity of acute genital disease and vaginal virus replication compared to the placebo group. The majority of animals in all groups developed at least one episode of recurrent disease but the frequency of recurrent disease was significantly reduced by each vaccine compared to placebo. No vaccine was significantly more protective than gD2 alone for any of the parameters described above. No vaccine decreased recurrent virus shedding. When protection against acute infection of dorsal root ganglia and the spinal cord was evaluated all vaccines decreased the per cent of animal with detectable virus and the quantity of virus but again no vaccine was significantly more protective than another. Improvements in HSV-2 vaccines may require inclusion of more T cell targets, more potent adjuvants or live virus vaccines.

Immunization with DNA vaccine expressing herpes simplex virus type 1 gD and IL-21 protects against mouse herpes keratitis

The development of novel vaccines to eradicate herpes simplex virus (HSV) is a global public health priority. In this study, we developed a DNA vaccine expressing HSV-1 glycoprotein D (gD) and mouse interleukin-21(IL-21) and intramuscularly inoculated mice 3 times at 2-week intervals with a total of 300 ?g/mouse. Two weeks after the last immunization the specific antibody, splenocyte proliferative response to gD, IFN-? and IL-4 as well as the cytotoxic activities of splenocytes and natural killer (NK) cells were assayed. Immune protection against herpes keratitis was concurrently evaluated in the immunized mice after HSV-1 challenge of the mouse cornea. The results showed that the DNA vaccine pRSC-gD-IL-21 generated higher levels of antibody, IFN-? and IL-4, and enhanced the splenocyte proliferative response to gD as well as the cytotoxic activity of splenocytes and NK cells to target cells compared with the response in either the pRSC-gD or mock plasmid pRSC immunized mice. Importantly, the pRSC-gD-IL-21 ameliorated herpes keratitis severity and time course after corneal infection with HSV-1. The findings suggest that the DNA vaccine pRSC-gD-IL-21 may induce an immune response that can limit HSV-1 infection and development of herpes keratitis in the immunized mice.

Treatment with cationic liposome-DNA complexes (CLDCs) protects mice from lethal Western equine encephalitis virus (WEEV) challenge

Having recently characterized a CD-1 outbred mouse model of pathogenesis for Western equine encephalitis virus, we examined the possible protective effects of cationic liposome-DNA complexes (CLDCs) against encephalitic arboviral infection. In this investigation, mice were pre-treated, co-treated, or post-treated with CLDC then challenged with a subcutaneous or aerosol dose of the highly virulent WEEV-McMillan strain, lethal in mice 4-5 days after inoculation. Pre-treatment with CLDCs provided a significant protective effect in mice, which was reflected in significantly increased survival rates. Further, in some instances a therapeutic effect of CLDC administration up to 12h after WEEV challenge was observed. Mice treated with CLDC had significantly increased serum IFN-gamma, TNF-alpha, and IL-12, suggesting a strong Th1-biased antiviral activation of the innate immune system. In virus-infected animals, large increases in production of IFN-gamma, TNF-alpha, MCP-1, IL-12, and IL-10 in the brain were observed by 72h after infection, consistent with neuroinvasion and viral replication in the CNS. These results indicate that strong non-specific activation of innate immunity with an immune therapeutic such as CLDC is capable of eliciting significant protective immunity against a rapidly lethal strain of WEEV and suggest a possible prophylactic option for exposed individuals.

Liposomal delivery of p-ialB and p-omp25 DNA vaccines improves immunogenicity but fails to provide full protection against B. melitensis challenge

Background

We have previously demonstrated protective efficacy against B. melitensis using formulations of naked DNA vaccines encoding genes ialB and omp25. The present study was undertaken to further understand the immune response generated by the protective vaccination regimens and to evaluate cationic liposome adsorption as a delivery method to improve vaccine utility.

Methods

The protective efficacy and immunogenicity of vaccines delivered as four doses of naked DNA, a single dose of naked DNA or a single dose of DNA surface adsorbed to cationic liposomes were compared using the BALB/c murine infection model of B. melitensis. Antigen-specific T cells and antibody responses were compared between the various formulations.

Results

The four dose vaccination strategy was confirmed to be protective against B. melitensis challenge. The immune response elicited by the various vaccines was found to be dependent upon both the antigen and the delivery strategy, with the IalB antigen favouring CD4+ T cell priming and Omp25 antigen favouring CD8+. Delivery of the p-ialB construct as a lipoplex improved antibody generation in comparison to the equivalent quantity of naked DNA. Delivery of p-omp25 as a lipoplex altered the profile of responsive T cells from CD8+ to CD4+ dominated. Under these conditions neither candidate delivered by single dose naked DNA or lipoplex vaccination methods was able to produce a robust protective effect.

Conclusions

Delivery of the p-omp25 and p-ialB DNA vaccine candidates as a lipoplex was able to enhance antibody production and effect CD4+ T cell priming, but was insufficient to promote protection from a single dose of either vaccine. The enhancement of immunogenicity by lipoplex delivery is a promising step toward improving the practicality of these two candidate vaccines, and suggests that this lipoplex formulation may be of value in situations where improvements to CD4+ responses are required. However, in the case of Brucella vaccine development it is suggested that further modifications to the candidate vaccines and delivery strategies will be required in order to deliver sustained protection.

The adjuvant CLDC increases protection of a herpes simplex type 2 glycoprotein D vaccine in guinea pigs

Herpes simplex virus (HSV) infections are common but there is no vaccine available. We evaluated cationic liposome-DNA complexes (CLDC) as an adjuvant for an HSV gD2 vaccine and compared it to an MPL/Alum adjuvant in a guinea pig model of genital herpes. The addition of CLDC to the gD2 vaccine significantly decreased acute and recurrent disease and most importantly the number of days with recurrent virus shedding compared to gD2 alone. Reductions in these outcomes were also detected when gD2+CLDC was compared to gD2+MPL/Alum. When the vaccine and adjuvants were evaluated as therapeutic vaccines, they were ineffective. CLDC enhanced protection compared to MPL/Alum and is the first vaccine to reduce recurrent virus shedding, a key to decreasing the spread of HSV-2.