Chemokine gene adjuvants can modulate immune responses induced by DNA vaccines

Two bicistronic DNA vaccines against Vibrio anguillarum and the immune effects on flounder Paralichthys olivaceus

Chemokines are cytokines that can promote the activation and migration of immune cells, and increase the recognition of antigen by antigen-presenting cells (APC). Previous studies showed that a DNA vaccine can induce humoral and cellular immune responses of flounder after immunization. To explore the improvement of chemokines on the efficiency of OmpK vaccine, two bicistronic DNA candidate vaccines were constructed and the immune responses they induced in the flounder were investigated by reverse transcription polymerase chain reaction (RT-PCR), indirect immunofluorescent assay (IFA), H&E staining, flow cytometry (FCM), and quantificational real-time polymerase chain reaction (qRT-PCR). pBudCE4.1 plasmid as an expression vector, bicistronic DNA vaccines encoding OmpK gene and CC-motif ligand 4 gene (p-OmpK-CCL4), or Ompk gene and CC-motif ligand 19 gene (p-OmpK-CCL19) were successfully constructed. The results showed that two bicistronic DNA vaccines expressed Ompk protein of Vibrio anguillarum and CCL4/CCL19 proteins of flounder both in vitro and in vivo. After immunization, a large number of leucocytes in muscle were recruited at the injection site in treatment groups. The constructed vaccines induced significant increases in CD4-1⁺ and CD4-2⁺ T lymphocytes, and sIgM⁺ B lymphocytes in peripheral blood, spleen, and head kidney. The percentage of T lymphocytes peaked on the 14^th post-vaccination day whereas that of B lymphocytes peaked in the 6^th post-vaccination week. Moreover, the expression profiles of 10 immune-related genes increased in muscles around the injection site, spleen, and head kidney. After the challenge, p-OmpK-CCL4 and p-OmpK-CCL19 conferred a relative percentage survival (RPS) of 74.1% and 63.3%, respectively, higher than p-OmpK alone (40.8%). In conclusion, both CCL4 and CCL19 can improve the protection of p-OmpK via evoking local immune response and then humoral and cellular immunity. CCL4 and CCL19 will be potential molecular adjuvants for use in DNA vaccines.

Protective efficacy of four heat-shock proteins as recombinant vaccines against photobacteriosis in Asian seabass (Lates calcarifer)

Photobacterium damselae subsp. piscicida (Phdp) is the causative agent of photobacteriosis in marine fish and is responsible for huge losses to marine aquaculture worldwide. Efforts have been made to develop a vaccine against this disease. Heat-shock proteins (HSPs) are a family of proteins that are ubiquitous in cellular life. Bacteria produce elevated levels of HSPs as a survival strategy when exposed to stressful environments in a host during infection. This group of proteins are also important antigens that can induce both humoral and cellular immune responses. In this study, four HSPs of Phdp, HSP90, HSP33, HSP70, and DnaJ, were selected for cloning and recombinant expression. Western blotting with rabbit anti-Phdp helped identify rHSP70 and rHSP33 as immunogenic proteins. Asian seabass (Lates calcarifer) immunised with rHSP90, rHSP33, rHSP70, and rDnaJ showed 48.28%, 62.07%, 51.72%, and 31.03% relative percent survival, respectively, after being challenged with Phdp strain AOD105021. High expression levels of immune-related genes and high antibody titres were observed in the rHSP33 group, and the sera of this group also exhibited a high level of bactericidal activity against Phdp. Collectively, our results suggest that HSP33 is a potential candidate for vaccine development against Phdp infection.

Molecular Adjuvants for DNA Vaccines: Application, Design, Preparation, and Formulation

Compared with conventional vaccines, the main advantage of DNA vaccine-based methods is its continued expression of the plasmid-encoded antigens followed by the induction of subsequent humoral and cellular immunities. DNA vaccines are currently used in animal models, but limited success has been obtained for use in clinical applications due to their poor immunogenicity. Various strategies are attempted to improve the induced immune response of DNA vaccines. It has been demonstrated that co-administration of molecular adjuvants with DNA vaccines is a promising approach to effectively elicit protective immunity by increasing the transfection efficiency of DNA vaccines. Genetic adjuvants are incorporated to promote activation of the transfected local antigen-presenting cells (APCs) and immune cells in the draining lymph node and polarization of T-cell subsets to decrease T-cell tolerance to the specific antigen. Here we provide an overview of different types of genetic adjuvants. The aim of the current chapter is to present a framework for the construction of a gene-based vaccine and adjuvant. Moreover, we describe the application of DNA vaccines co-administered with different types of genetic adjuvants and the methods to evaluate their potency in the mouse models.

Oral immunization with recombinant Lactobacillus casei displayed AHA1-CK6 and VP2 induces protection against infectious pancreatic necrosis in rainbow trout (Oncorhynchus mykiss)

Infectious pancreatic necrosis virus (IPNV) primarily infects larvae and young salmonid with serious economic losses, which causes haemorrhage and putrescence of hepatopancreas. To develop a more effective oral vaccine against IPNV infection, the aeromonas hydrophila adhesion (AHA1) gene was used as a targeting molecule for intestinal epithelial cells. A genetically engineered Lactobacillus casei (pPG-612-AHA1-CK6-VP2/L. casei 393) was constructed to express the AHA1-CK6-VP2 fusion protein. The expression of interest protein was confirmed by western blotting and the immunogenicity of pPG-612-AHA1-CK6-VP2/L. casei 393 was evaluated. And the results showed that more pPG-612-AHA1-CK6-VP2/L. casei 393 were found in the intestinal mucosal surface of the immunized group. The Lactobacillus-derived AHA1-CK6-VP2 fusion protein could induce the production of serum IgM and skin mucus IgT specific for IPNV with neutralizing activity in rainbow trouts. The levels of IL-1β, IL-8 and TNF-α isolated from the lymphocytes stimulated by AHA1-CK6-EGFP produced were significantly higher than EGFP group. For transcription levels of IL-1β, IL-8, CK6, MHC-II, Mx and TNF-1α in the spleen, the result indicated that the adhesion and target chemokine recruit more immune cells to induce cellular immunity. The level of IPNV in the immunized group of pPG-612-AHA1-CK6-VP2/L. casei 393 was significantly lower than that in the control groups. These data indicated that the adhesion and target chemokine could enhance antigen delivery efficiency, which provides a valuable strategy for the development of IPNV recombination Lactobacillus casei oral vaccine in the future.

The effects of CCL3, CCL4, CCL19 and CCL21 as molecular adjuvants on the immune response to VAA DNA vaccine in flounder (Paralichthys olivaceus)

The magnitude of the immune response induced by DNA vaccines depends on the amount and type of antigen-presenting cells attracted to the injection site. In our previous study, a DNA plasmid encoding the VAA gene of Vibrio anguillarum was constructed and shown to confer moderate protection against V. anguillarum challenge. To augment the protective efficacy of the VAA DNA vaccine and compare the adjuvant effects of CCL3, CCL4, CCL19 and CCL21, four bicistronic DNA plasmids containing the VAA gene of V. anguillarum together with the gene encoding the CCL3/CCL4/CCL19/CCL21 chemokines of flounder were successfully constructed and administered to fish, and the immune response of the animals and the enhancement of immunoprotection by the four chemokines were investigated. Vaccinated with pCCL3-VAA, pCCL4-VAA, pCCL19-VAA and pCCL21-VAA, flounder showed relative percent survivals of 62.16%, 83.78%, 78.38% and 72.97%, respectively, higher than the relative survival of flounder immunized with pVAA (40.54%). Compared with the pVAA group, the percentages of sIgM⁺, CD4-1⁺, and CD4-2⁺ lymphocytes and the levels of specific antibodies increased in pCCL3-VAA, pCCL4-VAA, pCCL19-VAA and pCCL21-VAA injection groups; CCL4 and CCL19 induced significantly higher levels of these parameters than CCL3 and CCL21 did. The amount of V. anguillarum in liver, spleen and kidney of pCCL3-VAA-, pCCL4-VAA-, pCCL19-VAA- and pCCL21-VAA-immunized flounder after V. anguillarum challenge was reduced compared to that in the pVAA group. Moreover, the co-expression of CCL3/CCL4/CCL19/CCL21 up-regulated immune-related gene expression associated with the local immune response. Our results indicate that CCL4 and CCL19 are promising adjuvants for use in VAA DNA vaccine against V. anguillarum.

The Genetic Adjuvants Interleukin-12 and Granulocyte-Macrophage Colony Stimulating Factor Enhance the Immunogenicity of an Ebola Virus Deoxyribonucleic Acid Vaccine in Mice

In previous studies, we showed that deoxyribonucleic acid (DNA) vaccines expressing codon-optimized filovirus envelope glycoprotein genes protect mice and nonhuman primates from viral challenge when delivered by intramuscular (IM) electroporation (EP). To determine whether we could achieve equivalent immunogenicity and protective efficacy by a simplified delivery method, we generated DNA vaccine plasmids expressing genetic adjuvants to potentiate immune responses. We tested the Th1-inducing cytokine interleukin-12 and the granulocyte growth factor granulocyte-macrophage colony stimulating factor, both of which have demonstrated significant adjuvant effect when included in clinical DNA vaccine formulations. In addition, because interferon (IFN)-αβ is required for DNA vaccine-induced immunity, we tested inclusion of a potent stimulator of the IFN-αβ pathway. Our data suggest that IM vaccination of mice with plasmid DNA encoding genetic adjuvants enhances vaccine immunogenicity, resulting in increased anti-Ebola virus (EBOV) immunoglobulin G and T-cell responses. Codelivery of genetic adjuvants also improved EBOV neutralizing capability compared with vaccine alone. Finally, IM vaccination with plasmid EBOV and genetic adjuvants provided complete protection against EBOV challenge. Overall, our data suggest that codelivery of genetic adjuvants with filovirus DNA vaccines using IM delivery can provide comparable efficacy to the same DNA vaccines when delivered using IM-EP devices.

The genetic adjuvant IL-12 enhances the protective efficacy of a DNA vaccine for Venezuelan equine encephalitis virus delivered by intramuscular injection in mice

We have previously shown that DNA vaccines expressing codon-optimized alphavirus envelope glycoprotein genes protect both mice and non-human primates from viral challenge when delivered by intramuscular electroporation (IM-EP). To determine if we could achieve equivalent immunogenicity and protective efficacy in the absence of electroporation, we co-delivered our Venezuelan equine encephalitis virus (VEEV) DNA vaccine with DNA plasmids expressing genetic adjuvants designed to augment immune responses. We tested the T_h1-inducing cytokine IL-12 as well as the granulocyte growth factor GM-CSF, both of which have demonstrated significant adjuvant effect when included in clinical DNA vaccine formulations. Additionally, as multiple reports have described the necessity of IFN-αβ in DNA vaccine immunogenicity, we tested vaccine plasmids encoding a potent stimulator of the IFN-αβ pathway. Our data suggest that IM vaccination of mice with plasmid DNA encoding genetic adjuvants enhances VEEV vaccine immunogenicity, resulting in improved T cell responses, as well as skewing of the anti-VEEV IgG antibody isotype. Additionally, IM vaccination of VEEV DNA vaccine and IL-12 provided complete protection against aerosol VEEV challenge. Overall, our data suggest that co-delivery of genetic adjuvants with alphavirus DNA vaccines using IM delivery can influence the type of immune response obtained and provide comparable protective immunity to that achieved by IM-EP delivery of the vaccine without adjuvants.

Coinjection of IL2 DNA enhances E7-specific antitumor immunity elicited by intravaginal therapeutic HPV DNA vaccination with electroporation

The generation and use of therapeutic human papillomavirus (HPV) DNA vaccines represent an appealing treatment method against HPV-associated cervical cancer owing to their safety and durability. Previously, we created a therapeutic HPV DNA vaccine candidate by linking the HPV16-E7 DNA sequence to calreticulin (CRT/E7), which we showed could generate significant E7-specific cytotoxic T lymphocyte (CTL)-mediated antitumor immune responses against HPV16 oncogenes expressing murine tumor model TC-1. Here we assess the therapeutic efficacy of intravaginal immunization with pcDNA3-CRT/E7 followed by electroporation. In addition, we examined whether coadministration of DNA-encoding interleukin 2 (IL2) with the pcDNA3-CRT/E7 could improve the T-cell responses elicited by pcDNA3-CRT/E7. TC-1 tumor-bearing mice vaccinated intravaginally with both pcDNA3-CRT/E7 and IL2 DNA followed by electroporation induced stronger local antitumor CTL response in comparison to mice that received other treatment regimens. Additionally, we found that coadministration of IL2 DNA with pcDNA3-CRT/E7 modified the tumor microenvironment by decreasing the population of regulatory T cells and myeloid-derived suppressor cells relative to that of CTLs. Our data demonstrate the translational potential of local administration of IL2 and pcDNA3-CRT/E7 followed by electroporation in treating cervicovaginal tumors.

A formalin-inactivated vaccine provides good protection against Vibrio harveyi infection in orange-spotted grouper (Epinephelus coioides)

Vibrio harveyi is one of the most common threats to farmed grouper, so considerable efforts are in practice to control the pathogen. This study presents a highly effective vaccine against V. harveyi in the orange-spotted grouper with the help of a single intraperitoneal immunization. The vaccine candidate was in form of whole, formalin-inactivated V. harveyi cells combined with a metabolizable ISA763 AVG adjuvant. Our results indicated that the vaccine triggered a remarkably higher expression level of interleukin (IL)-1β, IL-6, IL-8, and IL-10 in the groupers' kidneys and spleens, as recorded after 1 and 3 days of immunization. Antibody titers were significantly elevated in the vaccinated fish. A pivotal observation was that the vaccine highly protected the grouper from a homologous V. harveyi strain challenge with relative percentage survival values of 100% and 91.7% at 6 and 12 weeks post-immunization, respectively. Vaccinated fish also demonstrated strong cross-protection against a heterologous bacterial isolate challenge. Therefore, the inactivated V. harveyi vaccine is a promising candidate that could stimulate good immune responses and confer remarkable protection in farmed groupers.

An Interleukin 12 Adjuvanted Herpes Simplex Virus 2 DNA Vaccine Is More Protective Than a Glycoprotein D Subunit Vaccine in a High-Dose Murine Challenge Model

Vaccination is a proven intervention against human viral diseases; however, success against Herpes Simplex Virus 2 (HSV-2) remains elusive. Most HSV-2 vaccines tested in humans to date contained just one or two immunogens, such as the virion attachment receptor glycoprotein D (gD) and/or the envelope fusion protein, glycoprotein B (gB). At least three factors may have contributed to the failures of subunit-based HSV-2 vaccines. First, immune responses directed against one or two viral antigens may lack sufficient antigenic breadth for efficacy. Second, the antibody responses elicited by these vaccines may have lacked necessary Fc-mediated effector functions. Third, these subunit vaccines may not have generated necessary protective cellular immune responses. We hypothesized that a polyvalent combination of HSV-2 antigens expressed from a DNA vaccine with an adjuvant that polarizes immune responses toward a T helper 1 (Th1) phenotype would compose a more effective vaccine. We demonstrate that delivery of DNA expressing full-length HSV-2 glycoprotein immunogens by electroporation with the adjuvant interleukin 12 (IL-12) generates substantially greater protection against a high-dose HSV-2 vaginal challenge than a recombinant gD subunit vaccine adjuvanted with alum and monophosphoryl lipid A (MPL). Our results further show that DNA vaccines targeting optimal combinations of surface glycoproteins provide better protection than gD alone and provide similar survival benefits and disease symptom reductions compared with a potent live attenuated HSV-2 0ΔNLS vaccine, but that mice vaccinated with HSV-2 0ΔNLS clear the virus much faster. Together, our data indicate that adjuvanted multivalent DNA vaccines hold promise for an effective HSV-2 vaccine, but that further improvements may be required.

Interleukin-8 holds promise to serve as a molecular adjuvant in DNA vaccination model against Streptococcus iniae infection in fish

DNA vaccines had been widely used in animal models against various viral infections, while it was not so convincing for many infectious diseases especially bacterial disease in aquaculture. Interleukin-8(IL-8) as one of the CXC chemokines, its immunological role and adjuvant potential which had been proved in mammals were rarely reported in fish species. In this study, recombination plasmid pcDNA3.1/IL-8(pcIL-8) was conducted and the capacity of IL-8 as molecular adjuvant was explored from several aspects by co-injecting with a DNA vaccine encoding α-enolase(pcENO) against Streptococcus iniae infection in channel catfish. The results suggested that co-injection of pcIL-8 with DNA vaccine increased the innate immunity and specific antibody levels, as well as increased the immune-related genes involving in pro-inflammatory response, humoral and cellular immunity. Moreover, pcIL-8 enhanced the immunoprotection of pcENO with the relative percent survival(RPS) of 60% to 80% against S.iniae infection at 4 week post vaccination(p.v.), with the significantly higher RPS of 73.33% in pcENO+pcIL-8 group compared with that of pcENO alone(53.33%) at challenge test of 8 weeks p.v. Taken together, these results indicate pcIL-8 as a molecular adjuvant co-injected with DNA vaccine not only improves the immunoprotection but also maintains long period of immunity for channel catfish against S.iniae infection. Our study signifies that IL-8 holds promise to serve as a potential adjuvant in DNA vaccines against bacterial infections for long time.

Molecular cloning, expression and the adjuvant effects of interleukin-8 of channel catfish (Ictalurus Punctatus) against Streptococcus iniae

Interleukin-8 (IL-8) as an important cytokine involving in inflammatory and immune response, has been studied as effective adjuvants for vaccines in mammals. However, there are fewer reports about the characterization and adjuvant effects of IL-8 in fish. In this study, cloning and sequence analysis of IL-8 coding region of channel catfish (Ictalurus punctatus) were conducted, mature IL-8(rtIL-8) was expressed and evaluated for its adjuvant effects on the immunoprotection of subunit vaccine encoding α-enolase (rENO) of Streptococcus iniae from several aspects in channel catfish. The results showed co-vaccination of rENO with rtIL-8 enhanced immune responses including humoral and cellular immunity, with higher relative percent survival(RPS,71.4%) compared with the moderate RPS of rENO alone(50%) against S. iniae infection at 4 week post vaccination. While rtIL-8 failed to maintain long-lasting immune protection, only with RPS of 26.67% in rENO + rtIL-8-vaccinated fish compared with that of rENO alone(20%) at 8 week, signifying that IL-8 hold promise for use as potential immunopotentiator in vaccines against bacterial infections in fish, whereas it is insufficient to extend the immunoprotection for long time, and further studies are required to understand the mechanisms of IL-8 used as an adjuvant and seek for more effective way to strengthen the adjuvanticity of IL-8.

The catalytic A1 domains of cholera toxin and heat-labile enterotoxin are potent DNA adjuvants that evoke mixed Th1/Th17 cellular immune responses

DNA encoded adjuvants are well known for increasing the magnitude of cellular and/or humoral immune responses directed against vaccine antigens. DNA adjuvants can also tune immune responses directed against vaccine antigens to better protect against infection of the target organism. Two potent DNA adjuvants that have unique abilities to tune immune responses are the catalytic A1 domains of Cholera Toxin (CTA1) and Heat-Labile Enterotoxin (LTA1). Here, we have characterized the adjuvant activities of CTA1 and LTA1 using HIV and SIV genes as model antigens. Both of these adjuvants enhanced the magnitude of antigen-specific cellular immune responses on par with those induced by the well-characterized cytokine adjuvants IL-12 and GM-CSF. CTA1 and LTA1 preferentially enhanced cellular responses to the intracellular antigen SIVmac239-gag over those for the secreted HIVBaL-gp120 antigen. IL-12, GM-CSF and electroporation did the opposite suggesting differences in the mechanisms of actions of these diverse adjuvants. Combinations of CTA1 or LTA1 with IL-12 or GM-CSF generated additive and better balanced cellular responses to both of these antigens. Consistent with observations made with the holotoxin and the CTA1-DD adjuvant, CTA1 and LTA1 evoked mixed Th1/Th17 cellular immune responses. Together, these results show that CTA1 and LTA1 are potent DNA vaccine adjuvants that favor the intracellular antigen gag over the secreted antigen gp120 and evoke mixed Th1/Th17 responses against both of these antigens. The results also indicate that achieving a balanced immune response to multiple intracellular and extracellular antigens delivered via DNA vaccination may require combining adjuvants that have different and complementary mechanisms of action.

Molecular profiling of primary uveal melanomas with tumor-infiltrating lymphocytes

In contrast to other cancers, the presence of tumor-infiltrating lymphocytes (TILs) in uveal melanoma is associated with a poor prognosis. However, how TILs may promote disease progression and what regulates their infiltration has not yet been established. To address these clinically relevant outstanding questions, T cell, immune regulatory, and chemokine gene expression profiles of 57 enucleated uveal melanoma tumors were compared, encompassing 27 with TILs and 30 without,. Tumors with infiltrating lymphocytes expressed more CD8A mRNA, as well as IFNG, TGFB1, and FOXP3 transcripts. Other T helper associated cytokines and T helper transcription factors were not differentially expressed, nor were mediators of lymphocyte cytotoxicity. The immune inhibitors INDO, PDCA1, CTLA4, and LAG3, and the non-classical MHC Class I target of CD8⁺ T regulatory cells, HLA‑E, were significantly higher in tumors with TILs. FAS was also significantly higher. The C-C chemokine ligands CCL4, CCL5, and CCL20 were higher in tumors with TILs. Levels of CCL5 were most strongly correlated with levels of CD8A. Chemokine receptors were not differentially expressed. Molecular profiling of uveal melanoma tumors with TILs supports the existence of an immunosuppressive tumor microenvironment and suggests roles for CD8⁺ regulatory T cells, as well as specific chemokines, in fostering uveal melanoma disease progression.

Modulation of hepatitis C virus core DNA vaccine immune responses by co-immunization with CC-chemokine ligand 20 (CCL20) gene as immunoadjuvant

Plasmid DNA vaccination is a promising vaccine platform for prevention and treatment of infectious disease. Enhancement of the DNA vaccine potency by co-inoculation of immunoadjuvant has been shown to be an effective strategy. Modulation of dendritic cells and T-cells locomotion and trafficking to prime an immune response is mediated by distinct chemokines. The recent study was designed to elucidate the adjuvant activity of plasmid expressing CC-chemokine ligand 20 (pCCL20) in co-inoculation with hepatitis C virus (HCV) core DNA vaccine immunization. pCCL20 was constructed and evaluated for its functional expression. Sub-cutaneous inoculation of pCCL20 with HCV core DNA vaccine was performed via electroporation in BALB/c mice on day 0 and 14 and a HCV core protein booster was applied on day 28. On week after final immunization, both humoral and cell-mediated immune responses were assessed by indirect ELISA for core specific antibodies, lymphocyte proliferation, cytokine ELISA/ELISpot and cytotoxic Grenzyme B (GrzB) release assays. Mice were co-immunized with pCCL20 developed higher levels of core specific IFN-γ/IL-4 ratio and IL-2 release, IFN-γ producing cells, lymphocyte proliferation and cytotoxic Grenzyme B release in both draining lymph nodes and spleen cells of immunized mice. The core-specific serum total IgG and IgG2a/IgG1 ratio were significantly higher when the pCCL20 was co-inoculated. These results suggest the potential of CCL20 chemokine as vaccine adjuvant to enhance Th1 mediated cellular and humoral immune responses in HCV core DNA immunization.

The basics and advances of immunomodulators and antigen presentation: a key to development of potent memory response against pathogens

INTRODUCTION

Immunomodulators are agents, which can modulate the immune response to specific antigens, while causing least toxicity to the host system. Being part of the modern vaccine formulations, these compounds have contributed remarkably to the field of therapeutics. Despite the successful record maintained by these agents, the requirement of novel immunomodulators keeps increasing due to the increasing severity of diseases. Hence, research regarding the same holds great importance.

AREAS COVERED

In this review, we discuss the role of immunomodulators in improving performance of various vaccines used for counteracting most threatening infectious diseases, mechanisms behind their action and criteria for development of novel immunomodulators.

EXPERT OPINION

Understanding the molecular mechanisms underlying immune response is a prerequisite for development of effective therapeutics as these are often exploited by pathogens for their own propagation. Keeping this in mind, the present research in the field of immunotherapy focuses on developing immunomodulators that would not only enhance the protection against pathogen, but also generate a long-term memory response. With the introduction of advanced formulations including combination of different kinds of immunomodulators, one can expect tremendous success in near future.

Plasmid DNA vaccines against cancer: cytotoxic T-lymphocyte induction against tumor antigens

In recent years, a number of tumor vaccination strategies have been developed. Most of these rely on the identification of tumor antigens that can be recognized by the immune system. DNA vaccination represents one such approach for the induction of both humoral and cellular immune responses against tumor antigens. Studies in animal models have demonstrated the feasibility of utilizing DNA vaccination to elicit protective antitumor immune responses. However, most tumor antigens expressed by cancer cells in humans are weakly immunogenic, and therefore require the development of strategies to potentiate DNA vaccine efficacy in the clinical setting. This review focuses on recent advances in understanding of the immunology of DNA vaccines, as well as strategies used to increase DNA vaccine potency with respect to cytotoxic T-lymphocyte activity.

Protective Immunity againstBordetella pertussisby a Recombinant DNA Vaccine and the Effect of Coinjection with a Granulocyte-Macrophage Colony Stimulating Factor Gene

A recombinant pertussis DNA vaccine was described here with its immunogenicity and the ability to induce protection against B. pertussis infection in mice. Three immunodominant antigen gene fragments of pertussis, pertussis toxin subunit 1 (pts1), fragments of pertactin (prn) and filamentous hemagglutinin (fha), were recombined as fragment pts1-prn-fha named ppf, and it was cloned to plasmid pVAX1 as pVAX1/ppf. Compared to those injected with pVAX1, the mice injected with pVAX1/ppf significantly elicited more antigen specific antibody anti-PTS1, anti-PRN, anti-FHA and cytokine IL-10, IFN-gamma. When pGM-CSF was coinjected with pVAX1/ppf, the mice showed significantly increases of the three antibodies and cytokine IL-10, IL-4, IFN-gamma and TNF-alpha compared to those injected with pVAX1 only. The mice in group pVAX1/ppf & pGM-CSF, in particular; induced much more anti-PTS1, IL-4 and TNF-alpha than those in group pVAX1/ppf. In the intracerebral mouse protection test, the mice immunized with pVAX1/ppf or pVAX1/ppf & pGM-CSF induced protection to a lethal dose of B. pertussis. The results indicate that recombinant DNA vaccine and pGM-CSF coinjection can induce protective immunity against B. pertussis, demonstrating a valuable method to prevent pertussis.

Generation of antigen-specific immunity following systemic immunization with DNA vaccine encoding CCL25 chemokine immunoadjuvant

A significant hurdle in vaccine development for many infectious pathogens is the ability to generate appropriate immune responses at the portal of entry, namely mucosal sites. The development of vaccine approaches resulting in secretory IgA and mucosal cellular immune responses against target pathogens is of great interest and in general, requires live viral infection at mucosal sites. Using HIV-1 and influenza A antigens as models, we report here that a novel systemically administered DNA vaccination strategy utilizing co-delivery of the specific chemokine molecular adjuvant CCL25 (TECK) can produce antigen-specific immune responses at distal sites including the lung and mesenteric lymph nodes in mice. The targeted vaccines induced infiltration of cognate chemokine receptor, CCR9+/CD11c+ immune cells to the site of immunization. Furthermore, data shows enhanced IFN-λ secretion by antigen-specific CD3+/CD8+ and CD3+/CD4+ T cells, as well as elevated HIV-1-specific IgG and IgA responses in secondary lymphoid organs, peripheral blood, and importantly, at mucosal sites. These studies have significance for the development of vaccines and therapeutic strategies requiring mucosal immune responses and represent the first report of the use of plasmid co-delivery of CCL25 as part of the DNA vaccine strategy to boost systemic and mucosal immune responses following intramuscular injection.

Harnessing DNA-induced immune responses for improving cancer vaccines

DNA vaccines have emerged as an attractive strategy to promote protective cellular and humoral immunity against the encoded antigen. DNA vaccines are easy to generate, inexpensive to produce and purify at large-scale, highly stable and safe. In addition, plasmids used for DNA vaccines act as powerful "danger signals" by stimulating several DNA-sensing innate immune receptors that promote the induction of protective adaptive immunity. The induction of tumor-specific immune responses represents a major challenge for DNA vaccines because most of tumor-associated antigens are normal non-mutated self-antigens. As a consequence, induction of potentially self-reactive T cell responses against such poorly immunogenic antigens is controlled by mechanisms of central and peripheral tolerance as well as tumor-induced immunosuppression. Although several DNA vaccines against cancer have reached clinical testing, disappointing results have been observed. Therefore, the development of new adjuvants that strongly stimulate the induction of antitumor T cell immunity and counteract immune-suppressive regulation is an attractive approach to enhance the potency of DNA vaccines and overcome tumor-associated tolerance. Understanding the DNA-sensing signaling pathways of innate immunity that mediate the induction of T cell responses elicited by DNA vaccines represents a unique opportunity to develop novel adjuvants that enhance vaccine potency. The advance of DNA adjuvants needs to be complemented with the development of potent delivery systems, in order to step toward successful clinical application. Here, we briefly discuss recent evidence showing how to harness DNA-induced immune response to improve the potency of cancer vaccines and counteract tumor-associated tolerance.

CCL5: a double-edged sword in host defense against the hepatitis C virus

C-C motif ligand 5 (CCL5) facilitates induction of chemotaxis in immune cells and activation of hepatic stellate cells (HSC) at sites of liver inflammation during chronic hepatitis C virus (HCV) infection. Importantly, CCL5 participates in the establishment of T-helper 1 responses crucial in controlling liver disease and HCV infection outcome and demonstrates distinct gene expression patterns between the blood and the liver, stressing the importance of immunoregulatory networks differentially functioning between these compartments. This review illustrates the significance of CCL5-dependent pathways in HCV-related immunopathogenesis by elaborating on biological mechanisms interconnecting peripheral and tissue immunology, liver pathology, HSC activation, and interferon-α immunotherapy.

Technologies for enhanced efficacy of DNA vaccines

Despite many years of research, human DNA vaccines have yet to fulfill their early promise. Over the past 15 years, multiple generations of DNA vaccines have been developed and tested in preclinical models for prophylactic and therapeutic applications in the areas of infectious disease and cancer, but have failed in the clinic. Thus, while DNA vaccines have achieved successful licensure for veterinary applications, their poor immunogenicity in humans when compared with traditional protein-based vaccines has hindered their progress. Many strategies have been attempted to improve DNA vaccine potency including use of more efficient promoters and codon optimization, addition of traditional or genetic adjuvants, electroporation, intradermal delivery and various prime-boost strategies. This review summarizes these advances in DNA vaccine technologies and attempts to answer the question of when DNA vaccines might eventually be licensed for human use.

CCL5 mRNA is a marker for early fibrosis in chronic hepatitis C and is regulated by interferon-α therapy and toll-like receptor 3 signalling

Mechanisms causing liver fibrosis during chronic hepatitis C virus infection (cHCV) are not sufficiently understood. This study was aimed to identify biomarkers for early fibrosis (EF) and to investigate their potential role in cHCV-related fibrogenesis. To this end, peripheral whole blood (PB) samples from 36 patients with cHCV recruited from two independent cohorts were subjected to microarray analysis 12 h before initiation of peginterferon-alpha (Peg-IFN-α) and ribavirin therapy. Liver biopsies were evaluated using the Batts-Ludwig staging (BL-S) classification system for fibrosis. We showed that gene expression profiles (N = 8) distinguished between EF (BL-S: 0,1) and late fibrosis (LF; BL-S: 2,3,4) with 88.9% accuracy. Fibrosis-related functional annotations for chemokine-'C-C-motif'' ligand 5 (CCL5) provided foundation for focused investigation, and qRT-PCR confirmed that CCL5 mRNA levels (PB) reliably discriminate EF from LF (accuracy: 86.7%). Positive correlations (P < 0.05) with CCL5 mRNA levels and EF discovered gene expression profiles (PB) reflecting stable expression of IFN-α receptor 1, negative regulation of the MyD88-dependent toll-like receptor (TLR) pathway and decreased expression of TLR3 in vivo. Remarkably, Peg-IFN-α suppressed CCL5 mRNA levels (PB) in EF in vivo. These findings along with results from parallel in vitro investigation into the effect of IFN-α or poly I:C (TLR3-agonist) on CCL5 gene expression in hepatic stellate cells (HSC) attest to the multi-site involvement of these pathways in regulating fibrogenesis. In conclusion, we identified novel, reliable biomarkers for EF and exposed functional properties of the molecular network regulating CCL5 biosynthesis in peripheral or hepatic cell types with key roles in cHCV-related liver and/or immune pathogenesis.

CCL28 induces mucosal homing of HIV-1-specific IgA-secreting plasma cells in mice immunized with HIV-1 virus-like particles

Mucosae-associated epithelial chemokine (MEC or CCL28) binds to CCR3 and CCR10 and recruits IgA-secreting plasma cells (IgA-ASCs) in the mucosal lamina propria. The ability of this chemokine to enhance migration of IgA-ASCs to mucosal sites was assessed in a mouse immunization model using HIV-1(IIIB) Virus-like particles (VLPs). Mice receiving either HIV-1(IIIB) VLPs alone, CCL28 alone, or the irrelevant CCL19 chemokine were used as controls. Results showed a significantly increased CCR3 and CCR10 expression on CD19(+) splenocytes of HIV-1(IIIB) VPL-CCL28-treated mice. HIV-1 Env-specific IFN-γ, IL-4 and IL-5 production, total IgA, anti-Env IgA as well as gastro-intestinal mucosal IgA-secreting plasma cells were also significantly augmented in these mice. Notably, sera and vaginal secretions from HIV-1(IIIB) VLP-CCL28-treated mice exhibited an enhanced neutralizing activity against both a HIV-1/B-subtype laboratory strain and a heterologous HIV-1/C-subtype primary isolate. These data suggest that CCL28 could be useful in enhancing the IgA immune response that will likely play a pivotal role in prophylactic HIV vaccines.

Importance of the CCR5-CCL5 axis for mucosal Trypanosoma cruzi protection and B cell activation

Trypanosoma cruzi is an intracellular parasite and the causative agent of Chagas disease. Previous work has shown that the chemokine receptor CCR5 plays a role in systemic T. cruzi protection. We evaluated the importance of CCR5 and CCL5 for mucosal protection against natural oral and conjunctival T. cruzi challenges. T. cruzi-immune CCR5(-/-) and wild-type C57BL/6 mice were generated by repeated infectious challenges with T. cruzi. CCR5(-/-) and wild-type mice developed equivalent levels of cellular, humoral, and protective mucosal responses. However, CCR5(-/-)-immune mice produced increased levels of CCL5 in protected gastric tissues, suggesting compensatory signaling through additional receptors. Neutralization of CCL5 in CCR5(-/-)-immune mice resulted in decreased mucosal inflammatory responses, reduced T. cruzi-specific Ab-secreting cells, and significantly less mucosal T. cruzi protection, confirming an important role for CCL5 in optimal immune control of T. cruzi replication at the point of initial mucosal invasion. To investigate further the mechanism responsible for mucosal protection mediated by CCL5-CCR5 signaling, we evaluated the effects of CCL5 on B cells. CCL5 enhanced proliferation and IgM secretion in highly purified B cells triggered by suboptimal doses of LPS. In addition, neutralization of endogenous CCL5 inhibited B cell proliferation and IgM secretion during stimulation of highly purified B cells, indicating that B cell production of CCL5 has important autocrine effects. These findings demonstrate direct effects of CCL5 on B cells, with significant implications for the development of mucosal adjuvants, and further suggest that CCL5 may be important as a general B cell coactivator.

Natural killer cells that respond to human immunodeficiency virus type 1 (HIV‐1) peptides are associated with control of HIV‐1 infection

Human immunodeficiency virus (HIV)-specific natural killer (CD3- cells), CD4, and CD8 T cellular responses were determined in 79 HIV‐1-infected women in response to HIV‐1 peptide pools (Gag, Pol, Nef, Reg, and Env) with use of a whole‐blood intracellular cytokine staining assay that measures interferon-γ and/or interleukin-2. HIV‐specific CD3- cell responses to any region (Env and Reg predominantly targeted) were associated with lower viral load (P = .031) and higher CD4 T cell count (P = .015). Env‐specific CD3- cell responses were stronger in women who had both Gag CD4 and CD8 T cell responses and, in turn, was associated with lower viral load (P = .005). CD3- cell responders had significantly higher representation of CD4 T cell responses to Env and Reg (P = .012 and P = .015, respectively) and higher magnitudes of CD4 T cell responses (P = .017 and P = .037, respectively) than did nonresponders. Peptide‐specific natural killer cells are associated with markers of less severe disease progression among HIV‐1-infected women (lower viral load and higher CD4 T cell count) and with stronger HIV‐specific T cell responses.

Systemic immunization with CCL27/CTACK modulates immune responses at mucosal sites in mice and macaques

Plasmid DNA is a promising vaccine platform that has been shown to be safe and able to be administered repeatedly without vector interference. Enhancing the potency of DNA vaccination through co-delivery of molecular adjuvants is one strategy currently under investigation. Here we describe the use of the novel chemokine adjuvant CCL27/CTACK to enhance immune responses to an HIV-1 or SIV antigen in mice and rhesus macaques. CCL27 has been shown to play a role in inflammatory responses through chemotaxis of CCR10+ cells, and we hypothesized that CCL27 may modulate adaptive immune responses. Immunizations in mice with HIV-1gag/CCL27 enhanced immune responses both at peripheral and, surprisingly, at mucosal sites. To confirm these findings in a large-animal model, we created optimized CCL27 and SIV antigenic plasmid constructs for rhesus macaques. 10 macaques (n=5/group) were immunized intramuscularly with 1mg/construct of antigenic plasmids+/-CCL27 with electroporation. We observed significant IFN-gamma secretion and CD8+ T-cell proliferation in peripheral blood. Interestingly, CCL27 co-immunized macaques exhibited a trend toward greater effector CD4+ T cells in the bronchiolar lavage (BAL). CCL27 co-delivery also elicited greater antigen-specific IgA at unique sites including BAL and fecal samples but not in the periphery. Future studies incorporating CCL27 as an adjuvant in vaccine or therapy models where eliciting immune responses in the lung are warranted.

Plasmids encoding the mucosal chemokines CCL27 and CCL28 are effective adjuvants in eliciting antigen-specific immunity in vivo

A hurdle facing DNA vaccine development is the ability to generate strong immune responses systemically and at local immune sites. We report a novel systemically administered DNA vaccination strategy using intramuscular codelivery of CCL27 or CCL28, which elicited elevated peripheral IFN-gamma and antigen-specific IgG while driving antigen-specific T-cell secretion of cytokine and antibody production in the gut-associated lymphoid tissue and lung. This strategy resulted in induction of long-lived antibody responses that neutralized influenza A/PR8/34 and protected mice from morbidity and mortality associated with a lethal intranasal viral challenge. This is the first example of the use of CCL27 and CCL28 chemokines as adjuvants to influence a DNA vaccine strategy, suggesting further examination of this approach for manipulation of vaccine-induced immunity impacting both quality and phenotype of responses.

Immune effects observed after the injection of plasmids coding for rainbow trout (Oncorhynchus mykiss) CK5B, CK6 and CK7A chemokines demonstrate their immunomodulatory capacity and reveal CK6 as a major interferon inducer

In the current study, we have determined the immune effects of the intramuscular injection of eukaryotic expression plasmids coding for rainbow trout (Oncorhynchus mykiss) CK5B, CK6 or CK7A CC chemokines (pCK5B, pCK6 and pCK7A) as a first step towards the establishment of their biological role. We have studied the levels of expression of several immune genes in the spleen and head kidney by real-time PCR in comparison to the levels observed in animals injected with the empty plasmid. Concerning the levels of expression of these CC chemokines and the CXC chemokine, interleukin 8 (IL-8), each plasmid induced up-regulation on expression levels of its coded chemokine in the head kidney and spleen, but also affected the expression of other chemokines. Both pCK6 and pCK7A induced the expression of the other two CC chemokines, while pCK5B induced CK7A but not CK6. Both pCK5B and pCK7A induced IL-8 as well. pCK6 was the only plasmid that induced IL-1beta in the head kidney, whereas in the spleen, this occurred only with pCK5B. Different effects on the head kidney and spleen were also visible for tumour necrosis factor alpha (TNF-alpha), since the three plasmids induced this cytokine in the head kidney, but only pCK5B and pCK6 in the spleen. Concerning the effects on type I interferon (IFN), again pCK6 induced the strongest enhancement in the head kidney, while in the spleen it was pCK5B. However, the levels of expression of the Mx gene, know to be induced by type I IFN correlated with the CK6-induced IFN levels in the head kidney, but not with the CK5B-induced IFN in head kidney or spleen, suggesting an inhibition of Mx mRNA levels independent of IFN due to CK5B. The clear effect of pCK6 on the levels of expression of IFN-gamma and its strong effects on type I IFN, in contrast with its recent adscription to the CCL17/22 group linked to Th2 responses, were verified by studying the in vitro effects of recombinant CK6 on head kidney leukocytes. Again in this case, recombinant CK6 strongly induced type I IFN, Mx and IFN-gamma to a lesser extent, revealing CK6 as a potent IFN inducer in contrast to its mammalian homologues. Finally, effects on major histocompatibility complex (MHC)-IIalpha, CD4 and CD8alpha expression demonstrate that the three chemokines are able to mobilize antigen-presenting cells, CD4(+) and CD8(+) lymphocytes.

Immunisation route-dependent expression of IL-4/IL-13 can modulate HIV-specific CD8(+) CTL avidity

All HIV-1 'systemic vaccine trials' in humans have yielded poor outcomes. Thus, it is important to understand whether the route of delivery influences the quality of protective CTL immunity. Using heterologous poxvirus immunisation we have shown that systemically (i.m./i.m.) immunised CD8(+) T cells generated higher levels of IL-4/IL-13 compared to mucosal delivery and expression also correlated with i.m./i.m. immunised mice eliciting CTL of lower avidity. Studies using IL-4(-/-) and IL-13(-/-) KO mice have shown that the capacity to express IFN-gamma, IL-4 and/or IL-13 by K(d)Gag(197-205)-specific CTL differed between these groups and was inversely correlated with CTL avidity (IL-13(-/-)>IL-4(-/-)>BALB/c), although no significant differences in the magnitude of CTL responses were observed between IL-13(-/-) and wild type mice. When IL-13 was reconstituted in IL-13(-/-) splenocytes in vitro, their ability to bind tetramers also decreased significantly. Our data reveal that total absence of IL-13 can greatly enhance CTL avidity. In contrast, extracellular IL-4 appears to be important in maintaining long-term Th1/Th2 balance in CTL, even though expression of IL-4 by CTL markedly reduced avidity. STAT6(-/-) mice also showed memory CTL of higher avidity. Furthermore, CCL5 expression in K(d)Gag(197-205)-specific CTL was also regulated by IL-4/IL-13.

Enhancing immune responses against SARS-CoV nucleocapsid DNA vaccine by co-inoculating interleukin-2 expressing vector in mice

The immunogenicity of SARS-CoV nucleocapsid DNA vaccine and the immunoregulatory activity of interleukin-2 (IL-2) were investigated. DNA vaccine plasmids, pcDNA-N and pcDNA-IL2, were constructed and inoculated into BALB/c mice with or without pcDNA-IL2 by intramuscular injection. Cellular and humoral immune responses were assessed by indirect ELISA, lymphocyte proliferation assays, ELISPOT and FACS. The nucleocapsid DNA vaccine had good immunogenicity and can induce specific humoral and cellular immunity in BALB/c mice, while IL-2 plays an immunoadjuvant role and enhances specific immune responses. This study provides a frame of reference for the design of DNA vaccines against SARS-CoV.

Enhancement of immunogenicity of a therapeutic cervical cancer DNA-based vaccine by co-application of sequence-optimized genetic adjuvants

Treatment of patients with cervical cancer by conventional methods (mainly surgery, but also radiotherapy and chemotherapy) results in a significant loss in quality of life. A therapeutic DNA vaccine directed to tumor-specific antigens of the human papilloma virus (HPV) could be an attractive treatment option. We have developed a nontransforming HPV-16 E7-based DNA vaccine containing all putative T cell epitopes (HPV-16 E7SH). DNA vaccines, however, are less immunogenic than protein- or peptide-based vaccines in larger animals and humans. In this study, we have investigated an adjuvant gene support of the HPV-16 E7SH therapeutic cervical cancer vaccine. DNA encoded cytokines (IL-2, IL-12, GM-CSF, IFN-gamma) and the chemokine MIP1-alpha were co-applied either simultaneously or at different time points pre- or post-E7SH vaccination. In addition, sequence-optimized adjuvant genes were compared to wild type genes. Three combinations investigated lead to an enhanced IFN-gamma response of the induced T cells in mice. Interestingly, IFN-gamma secretion of splenocytes did not strictly correlate with tumor response in tumor regression experiments. Gene-encoded MIP-1alpha applied 5 days prior to E7SH-immunization combined with IFN-gamma or IL-12 (3 days) or IL-2 (5 days) postimmunization lead to a significantly enhanced tumor response that was clearly associated with granzyme B secretion and target cells lysis. Our results suggest that a conditioning application and combination with adjuvant genes may be a promising strategy to enhance synergistically immune responses by DNA immunization for the treatment of cervical cancer.

Host CCL3L1 gene copy number in relation to HIV-1-specific CD4+ and CD8+ T-cell responses and viral load in South African women

HIV-specific T-cell responses play an important role in control of infection. Because CCL3 has immune modulatory and antiviral activities, we hypothesized that host CCL3 genotype (CCL3L1 gene duplications) would influence the development of effective HIV-specific immune responses. Copy numbers of CCL3L1 were determined for 71 HIV-infected women, and HIV-specific CD4 and CD8 T-cell responses to overlapping peptide pools spanning the HIV-1 subtype C genome were simultaneously measured by an interferon-gamma and interleukin-2 whole-blood flow cytometric assay. Host CCL3L1 copy number correlated negatively with viral load (r=-0.239, P=0.045), as did magnitudes of Gag CD4 (r=-0.362, P=0.002) and CD8 (r=-0.261, P=0.028) T-cell responses. Patients with a Gag CD4 response (P=0.002) or dominant Gag CD8 (P=0.006) response had significantly lower viral loads than those whose dominant response targeted another region of the genome, whereas a dominant Nef-specific CD8 T-cell response was associated with higher HIV viral load. CCL3L1 copy number greater than or equal to the population median of 5 was significantly associated with increased magnitude of CD4 Gag responses (P=0.017), and women who had CD4 and CD8 Gag-specific responses had significantly lower viral loads (P=0.004) and higher CCL3L1 copy number (P=0.015) than those women with only CD8 Gag-specific responses.

Effects of MIP-1 alpha, MIP-3 alpha, and MIP-3 beta on the induction of HIV Gag-specific immune response with DNA vaccines

Transfection of DNA vaccines with chemokines may recruit dendritic cells (DCs) locally to capture the antigenic genes and their gene products to generate enhanced CD8(+) cytotoxic T lymphocytes (CTLs). In this study, we investigated the effects of macrophage inflammatory protein (MIP)-1 alpha, MIP-3 alpha, and MIP-3beta on human immunodeficiency virus (HIV) Gag DNA vaccination. The chemokine plasmids markedly enhanced the local infiltration of inflammatory cells and increased the presence of CD11c(+) B7.2(+)-activated DCs. MIP-1 alpha and MIP-3 alpha were potent adjuvants in augmenting CTLs and afforded strong protection to immunized animals against challenge with vaccinia virus expressing Gag (vv-Gag). However, decreased humoral response was observed. MIP-3beta plasmid did not dramatically alter immunity. The chemokine inoculation time with respect to DNA vaccine priming was also investigated. The injection of pMIP-3 alpha three days before Gag plasmid (pGag) vaccination markedly increased specific CTLs compared with simultaneous injection and led to higher protection against vv-Gag. Immunity was also shifted toward a T-helper type-1 (Th1) response. In contrast, inoculation with pMIP-3 alpha three days after pGag vaccination shifted immunity toward a Th2 response. Our data suggest that administration of a chemokine with DNA vaccines offers a valuable strategy to modulate the efficacy and polarization of specific immunity and that chemokine-antigen timing is critical in determining overall biological effects.

Granulocyte-macrophage colony-stimulating factor DNA prime-protein boost strategy to enhance efficacy of a recombinant pertussis DNA vaccine

AIM

To investigate a new strategy to enhance the efficacy of a recombinant pertussis DNA vaccine. The strategy is co-injection with cytokine plasmids as prime, and boosted with purified homologous proteins.

METHOD

A recombinant pertussis DNA vaccine containing the pertussis toxin subunit 1 (PTS1), fragments of the filamentous hemagglutinin (FHA) gene and pertactin (PRN) gene encoding filamentous hemagglutinin and pertactin were constructed. Balb/c mice were immunized with several DNA vaccines and antigen-specific antibodies anti-PTS1,anti-PRN, anti-FHA,cytokines interleukin (IL)-10, IL-4, IFN-gamma,TNF-alpha,and splenocyte-proliferation assay were used to describe immune responses.

RESULTS

The recombinant DNA vaccine could elicit similar immune responses in mice as that of separate plasmids encoding the 3 fragments, respectively. Mice immunized with DNA and boosted with the corresponding protein elicited more antibodies than those that received DNA as boost. In particular, when the mice were co-immunized with murine granulocyte-macrophage colony-stimulating factor plasmids and boosted with proteins, all 4 cytokines and the 3 antigen-specific antibodies were significantly increased compared to the pVAX1 group. Anti-PTS1, anti- FHA, IL-4 and TNF-alpha elicited in the colony stimulating factor (CSF) prime-protein boost group showed significant increase compared to all the other groups.

CONCLUSION

This prime and boost strategy has proven to be very useful in improving the immunogenicity of DNA vaccines against pertussis.

Immunostimulatory combinations: designing the next generation of vaccine adjuvants

Agents that activate dendritic cells are essential components for vaccines and can be conceptualized as molecular adjuvants. Other molecular adjuvants affect downstream factors that shape the resulting immune response. This review provides a compendium of recently studied molecular adjuvants, focusing on CD8+ T cell responses, which have important roles in HIV vaccines. Reference is also made to CD8+ T cell antitumor responses, where parallel studies of molecular adjuvants are being pursued. Molecular adjuvants can be considered in the following groups: TNF superfamily molecules such as CD40 ligand; agonists for TLRs; agonists for NAIP, CIITA, HET-E, TP-1-leucine-rich repeat pathway receptors, such as nucleotide-binding and oligomerization domain (NOD)1, NOD2, and cryopyrin; chemokines; ILs; CSFs; IFNs; alarmins; and purinergic P2X7 receptor agonists. Complementing these positively acting agents are strategies to reduce the immunosuppressive effects of CD4+CD25+ regulatory T cells and negatively acting factors such as TGF-beta, IL-10, suppressor of cytokine signaling 1, and programmed cell death-1 using neutralizing antibodies, antisense, and small interfering RNA. Especially effective are combinations of molecular adjuvants, which can elicit a massive expansion of antigen-specific CD8+ T cells and show unprecedented efficacy in vaccine and tumor models. Taken together, these new approaches provide significant incremental progress in the development of vaccines to elicit cell-mediated immunity against HIV and other pathogens.

Co-injection of interleukin 8 with the glycoprotein gene from viral haemorrhagic septicemia virus (VHSV) modulates the cytokine response in rainbow trout (Oncorhynchus mykiss)

Since previous results showed that interleukin 8 (IL-8) was induced in rainbow trout (Oncorhynchus mykiss) in response to viral hemorrhagic septicemia virus (VHSV) infection, we have cloned IL-8 in an expression vector (pIL8+) and studied its possible adjuvant effect on the early response to a VHSV immunization model, focusing on the early response of several cytokines induced by a vector coding for the glycoprotein of VHSV (pMCV1.4-G) in the spleen and head kidney. First, we demonstrated that the pIL8+ successfully transcribed IL-8, by induction of IL-8 transcription in the muscle and blood, and by a massive infiltration of neutrophils at the muscle inoculation site. We have studied the effect of pIL8+ co-administration on the expression of two pro-inflammatory cytokines, such as IL-1beta and tumour necrosis factor alpha (TNF-alpha); cytokines that have mainly an inhibitory role, IL-11 and transforming growth factor beta (TGF-beta); and a Th1 type cytokine, IL-18. We demonstrated that the co-administration of pIL8+ with pMCV1.4-G modulates the cytokine response that is induced, mainly by having its effect increasing pro-inflammatory cytokines (IL-1beta and TNF-alpha1), with a greater impact on the spleen, and to a lesser extent in the head kidney. All these data suggest that IL-8 is able to modulate the early cytokine immune response that is produced in response to a DNA vaccine, and therefore, might be a potential immune adjuvant in fish viral vaccination. More work should be done to determine if this modulation has a beneficial effect on protection as seen in other mammal viral models.

Positive inductive effect of IL-2 on virus-specific cellular responses elicited by a PRRSV-ORF7 DNA vaccine in swine

This study investigated the effect of swine interleukin 2 (IL-2) and swine interleukin 4 (IL-4) on the development of immune responses induced by a PRRSV-ORF7 DNA vaccine (phCMV-ORF7). The two cytokines were cloned separately in the eukaryotic expression vector phCMV, and delivered via gene gun as adjuvants for the DNA vaccine. Groups of 3-week-old certified PRRSV-free, castrated male, Yorkshire crossbred pigs, were vaccinated with or without the IL-2 or IL-4. The ensuing humoral and cellular immune responses were analyzed by a PRRSV-specific ELISA, and by an in vitro blastogenic response of peripheral blood mononuclear cells (PBMC) stimulated by viral antigen, respectively. The animals were boosted 21 days post-vaccination and challenged 28 days afterward. The virus loads post-challenge were measured by real time PCR. The group of swine receiving the vaccine plus IL-2 had significant virus-specific blastogenic responses 3 weeks after the vaccine-cytokine boost, when compared to those of the experimental pigs that received the vaccine plus IL-4, vaccine alone, unvaccinated controls or the pigs vaccinated with the DNA vaccine cloned in the reverse orientation (phCMV-ORF7(Rev)). None of the experimental swine had detectable specific antibodies against the virus during the vaccination phase. The virus load peak in vaccinated animals was delayed by about 72h as compared to that of the control pigs (unvaccinated and vaccinated with the phCMV-ORF7(Rev) construct). Interestingly, animals that received the phCMV-ORF7 vaccine alone consistently had low virus loads throughout the study. These results demonstrate that IL-2 has a positive inductive effect on the activation of vaccine-induced virus-specific cellular immunity, while IL-4 appeared to have a suppressive effect. Our data also suggest that ORF7 may play a role in reducing the virus load in PRRSV infected animals.

Developing DNA vaccines that call to dendritic cells

DNA vaccination is a novel immunization strategy that has great potential for the development of vaccines and immune therapeutics. This strategy has been highly effective in mice, while less immunogenic in nonhuman primates and humans. Enhancing DNA vaccine potency remains a challenge. It is likely that APCs, and especially DCs, play a paramount role in the presentation of vaccine antigen to the immune system. A new study reports the synergistic recruitment, expansion, and activation of DCs in vivo in a mouse model through covaccination with plasmids encoding macrophage inflammatory protein-1alpha (MIP-1alpha), fms-like tyrosine kinase 3 ligand (Flt3L), and the DNA vaccine. Such cooperative strategies delivering vaccine in a single, simple platform result in improved cellular immunity in vivo, including enhanced tetramer responses and IFN-gamma secretion by antigen-specific cells.

Molecular adjuvants for mucosal immunity

Mucosal surfaces represent the entry route of a multitude of viral pathogens. For many of these viruses, such as the herpes simplex viruses and human immunodeficiency virus, no effective vaccine exists. Hence, it is important that prospective vaccines engender maximal immunity at these susceptible sites. Genetic vaccines encoding adjuvant molecules represent one approach to optimize mucosal as well as systemic immunity. Promising candidates include various inflammatory cytokines and chemokines that might be used to enhance the primary response to a level sufficient for protection. Encouraging studies involving cytokines such as granulocyte/macrophage colony-stimulating factor, interleukin-2 (IL-2), IL-12, IL-18, and many others are examined. Notable chemokines that may offer hope in such efforts include IL-8, RANTES, CCL19, CCL21, and a few others. Combinatorial approaches utilizing several cytokines and chemokines will most likely yield the greatest success. In addition, as more is discovered regarding the requirements for memory development of T cells, boosters involving key cytokines such as IL-15 and IL-23 may prove beneficial to long-term maintenance of the memory pool. This review summarizes the progress in the use of genetic vaccines to achieve mucosal immunity and discusses the needed strategies to maximize long-term prospective immunity at this vulnerable entry site.