Plasmid DNA malaria vaccine: tissue distribution and safety studies in mice and rabbits

DNA vaccination with VP2 gene fragment confers protection against Infectious Bursal Disease Virus in chickens

Infectious Bursal Disease Virus (IBDV) causes immunosuppression in young chickens by destruction of antibody producing B cells in the Bursa of Fabricius and poses a potential threat to the poultry industry. We have examined the protective efficacy of a subunit DNA vaccine against IBDV infection in chickens in this study. An immunodominant VP2 gene fragment (VP252-417) was cloned into CMV promoter based DNA vaccine vector pVAX1 and in vitro expression of the DNA encoded antigens was confirmed by transfection of CHO cells with vaccine constructs followed by RT-PCR and western blot analysis using IBDV-antiserum. Two weeks old chickens were immunized intramuscularly with pVAXVP252-417 and the in vivo transcription of the plasmid DNA was confirmed by RT-PCR analysis of DNA injected muscle tissue at different intervals of post immunization. Tissue distribution analysis revealed that the plasmid DNA was extensively distributed in muscle, spleen, kidney, liver, and bursa tissues. Chickens immunized with pVAXVP252-417 developed high titer (1:12,000) of anti-VP252-417 antibodies. Further, chicken splenocytes from pVAXVP252-417 immunized group showed a significantly high proliferation to the whole viral and recombinant antigen (P<0.01) compared to control groups, which implies that pVAXVP252-417 codes for immunogenic fragment which has epitopes capable of eliciting both B and T cell responses. This is evident by the fact that, pVAXVP252-417 immunized chicken conferred 75% protection against virulent IBDV (vIBDV) challenge compared to the control group. Thus, the present study confirms that the immunodominant VP2 fragment can be used as a potential DNA vaccine against IBDV infection in chickens.

Latest developments and future directions in dengue vaccines

Dengue is a mosquito-borne disease which is currently an expanding global health problem. The disease is caused by four closely related viruses, the dengue virus. There are no specific dengue therapeutics and prevention is currently limited to vector control measures. Development of an effective tetravalent dengue vaccine would therefore represent a major advance in the control of the disease and is considered a high public health priority. While a licensed dengue vaccine is not yet available, the scope and intensity of dengue vaccine development has increased dramatically in the last decade. The uniqueness of the dengue viruses and the spectrum of disease resulting from infection have made dengue vaccine development difficult. Several vaccine candidates are currently being evaluated in clinical studies. The candidate currently at the most advanced clinical development stage, a live-attenuated tetravalent vaccine based on chimeric yellow fever dengue virus, has progressed to phase III efficacy studies. Several other live-attenuated vaccines, as well as subunit, DNA and purified inactivated vaccine candidates, are at earlier stages of clinical development. Additional technological approaches, such as virus-vectored and virus-like particle-based vaccines, are under evaluation in preclinical studies.

Immunogenicity, protective efficacy and safety of a recombinant DNA vaccine encoding truncated Plasmodium yoelii sporozoite asparagine-rich protein 1 (PySAP1)

Although great efforts have been undertaken for the development of malaria vaccines, no completely effective malaria vaccines are available yet. Despite being clinically silent, the pre-erythrocytic stage is considered an ideal target for the development of malaria vaccines. Sporozoite asparagine-rich protein 1 (SAP1) is a sporozoite-localized protein that regulates the expression of UIS (upregulated in infectious sporozoites) genes, which are essential for the infectivity of sporozoites. In this study, a recombinant DNA vaccine encoding a predicted antigenic determinant region of Plasmodium yoelii SAP1 (PySAP1) was constructed. Immunization of mice with this DNA vaccine construct resulted in significant elevation of cytokines such as IFN-γ, IL-2, IL-4 and IL-10, and total IgG as compared with control groups immunized with either the empty DNA vector or saline. After challenge with sporozoites, the group receiving the DNA vaccine showed delayed development of parasitemia and prolonged survival time compared with the control group. The DNA vaccine provided partial protection against P. yoelii 17XL infection, with an overall protection rate of 20%. In addition, the DNA vaccine did not show integration into the host genome. Further studies of SAP1 are needed to test whether it can be used as subunit vaccine candidate.

Pharmacokinetics and risk evaluation of DNA vaccine against Schistosoma japonicum

DNA plasmid immunization is a novel approach of preventive and therapeutic vaccine. More than 100 DNA vaccines have been on preclinical or clinical phase trials, and four kinds of DNA vaccines for livestock have been approved by USDA, CFIA, and APVMA. Schistosomiasis is a worldwide parasitic disease, and vaccine immunization is supposed to be a promising approach to control the health crisis. On the basis of former preclinical studies, we further focused on the pharmacokinetics and risk evaluation of DNA vaccine in vivo. In the present study, enhanced green fluorescent protein (EGFP) report gene was fused with Schistosoma japonicum 23 kDa transmembrane protein antigen gene (Sj23) and constructed into DNA vaccine pVIVO2-Sj23.EGFP. After intramuscularly injecting 100 μg of purified DNA vaccine plasmid to immunizate BALB/c mice, we studied the tissue distribution of DNA plasmid and expressed Sj23.EGFP antigen, the persistence time of elicited antibodies, and the risk of DNA vaccine transferred into intestinal microorganisms. The results showed that DNA vaccine plasmid could be distributed into all tissues of the body after injection; however, only few organs including the injected muscle were detected DNA vaccine at postimmunization until the 100 days by PCR technology; the detection of green fluorescence protein displayed that DNA vaccine could be expressed in almost every tissue and organs; the ELISA assay indicated the immune antibody against Sj23 could persist over 70 days; and the DNA vaccine transferring intestinal flora results was negative. The results indicated that the DNA vaccine has systemic protection and long-lasting effectivity and is safe to intestinal flora.

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.

Biodistribution, persistence and lack of integration of a multigene HIV vaccine delivered by needle-free intradermal injection and electroporation

It is likely that gene-based vaccines will enter the human vaccine area soon. A few veterinary vaccines employing this concept have already been licensed, and a multitude of clinical trials against infectious diseases or different forms of cancer are ongoing. Highly important when developing novel vaccines are the safety aspects and also new adjuvants and delivery techniques needs to be carefully investigated so that they meet all short- and long-term safety requirements. One novel in vivo delivery method for plasmid vaccines is electroporation, which is the application of short pulses of electric current immediately after, and at the site of, an injection of a genetic vaccine. This method has been shown to significantly augment the transfection efficacy and the subsequent vaccine-specific immune responses. However, the dramatic increase in delivery efficacy offered by electroporation has raised concerns of potential increase in the risk of integration of plasmid DNA into the host genome. Here, we demonstrate the safety and lack of integration after immunization with a high dose of a multigene HIV-1 vaccine delivered intradermally using the needle free device Biojector 2000 together with electroporation using Derma Vax™ DNA Vaccine Skin Delivery System. We demonstrate that plasmids persist in the skin at the site of injection for at least four months after immunization. However, no association between plasmid DNA and genomic DNA could be detected as analyzed by qPCR following field inversion gel electrophoresis separating heavy and light DNA fractions. We will shortly initiate a phase I clinical trial in which healthy volunteers will be immunized with this multiplasmid HIV-1 vaccine using a combination of the delivery methods jet-injection and intradermal electroporation.

FDA guidance on prophylactic DNA vaccines: analysis and recommendations

The FDA has been regulating the conduct of prophylactic DNA vaccine trials in the US for nearly 15 years. This work describes the evolution of FDA policy over that period, the status of current regulatory guidance, and provides recommendations for further changes to facilitate development in this field.

DNA vaccines and intradermal vaccination by DNA tattooing

Over the past two decades, DNA vaccination has been developed as a method for the induction of immune responses. However, in spite of high expectations based on their efficacy in preclinical models, immunogenicity of first generation DNA vaccines in clinical trials was shown to be poor, and no DNA vaccines have yet been licensed for human use. In recent years significant progress has been made in the development of second generation DNA vaccines and DNA vaccine delivery methods. Here we review the key characteristics of DNA vaccines as compared to other vaccine platforms, and recent insights into the prerequisites for induction of immune responses by DNA vaccines will be discussed. We illustrate the development of second generation DNA vaccines with the description of DNA tattooing as a novel DNA delivery method. This technique has shown great promise both in a small animal model and in non-human primates and is currently under clinical evaluation.

Gene doping

Gene doping abuses the legitimate approach of gene therapy. While gene therapy aims to correct genetic disorders by introducing a foreign gene to replace an existing faulty one or by manipulating existing gene(s) to achieve a therapeutic benefit, gene doping employs the same concepts to bestow performance advantages on athletes over their competitors. Recent developments in genetic engineering have contributed significantly to the progress of gene therapy research and currently numerous clinical trials are underway. Some athletes and their staff are probably watching this progress closely. Any gene that plays a role in muscle development, oxygen delivery to tissues, neuromuscular coordination, or even pain control is considered a candidate for gene dopers. Unfortunately, detecting gene doping is technically very difficult because the transgenic proteins expressed by the introduced genes are similar to their endogenous counterparts. Researchers today are racing the clock because assuring the continued integrity of sports competition depends on their ability to develop effective detection strategies in preparation for the 2012 Olympics, which may mark the appearance of genetically modified athletes.

From Plasmids to Protection: A Review of DNA Vaccines Against Infectious Diseases

The field of DNA vaccine development began over 16 years ago with the observation that plasmid DNA could be injected into and expressed in vivo and drive adaptive immune responses. Since then, there has been great interest in developing this technology to create a new generation of vaccines with the ability to elicit both humoral and cellular immune responses from an inherently innocuous injection. However, DNA vaccines have yet to proceed past phase I/II clinical trials in humans--primarily due to a desire to induce more potent immune responses. This review will examine how DNA vaccines function to induce an immune response and how this information might be useful in future vaccine design.

Vaccination with vif-deleted feline immunodeficiency virus provirus, GM-CSF, and TNF-alpha plasmids preserves global CD4 T lymphocyte function after challenge with FIV

Feline immunodeficiency virus (FIV) DNA vaccine approaches that included a vif-deleted FIV provirus (FIV-pPPRDeltavif) and feline cytokine expression plasmids were tested for immunogenicity and efficacy by immunization of specific pathogen free cats. Vaccine protocols included FIV-pPPRDeltavif plasmid alone; a combination of FIV-pPPRDeltavif DNA and feline granulocyte macrophage-colony stimulating factor (GM-CSF) and tumor necrosis factor (TNF)-alpha expression plasmids; or a combination of FIV-pPPRDeltavif and feline interleukin (IL)-15 plasmids. Cats immunized with FIV-pPPRDeltavif, GM-CSF and TNF-alpha plasmids demonstrated an increased frequency of FIV-specific T cell proliferation responses compared to other vaccine groups. Immunization with FIV-pPPRDeltavif and IL-15 plasmids was distinguished from other vaccine protocols by the induction of antiviral antibodies. Suppression of virus loads was not observed for any of the FIV-pPPRDeltavif DNA vaccine protocols after challenge with the FIV-PPR isolate. However, prior immunization with FIV-pPPRDeltavif, GM-CSF, and TNF-alpha plasmids resulted in preservation of CD4 T cell functions, including mitogen-induced cytokine expression and antigen-specific proliferation upon infection with FIV. These findings justify further examination of cytokine combinations as adjuvants for lentiviral DNA vaccines.

Quantitative real-time PCR study on persistence of pDNA vaccine pVax-Hsp60 TM814 in beef muscles

Background

Application of plasmid DNA for immunization of food-producing animals established new standards of food safety. The addition of foreign products e.g. pDNA into the food chain should be carefully examined to ensure that neither livestock animals nor consumers develop unpredicted or undesirable side-effects.

Methods

A quantitative real-time PCR (QRTPCR) methodology was developed to study the biodistribution and persistence of plasmid DNA vaccine pDNAX (pVAX-Hsp60 TM814) in mice and beef cattle. The linear quantification range and the sensitivity of the method was found to be 10 – 10⁹ copies per reaction (500 ng/gDNA) and 3 copies per reaction, respectively.

Results

Persistence of pDNAX in mice muscle tissue was restricted to injection site and the amount of pDNAX showed delivery formulation dependent (naked pDNA, electroporation, cationic liposome complexes) and mouse age-dependent clearance form injection site but pDNAX was still detectable even after 365 days. The QRTPCR analysis of various muscle tissue samples of vaccinated beef bulls performed 242–292 days after the last revaccination proved that residual pDNAX was found only in the injection site. The highest plasmid levels (up to 290 copies per reaction) were detected in the pDNAX:CDAN/DOPE group similarly to mice model. No pDNA was detected in the samples from distant muscles and draining lymph nodes.

Conclusion

Quantitative real-time PCR (QRTPCR) assay was developed to assess the residual pDNA vaccine pVAX-Hsp60 TM814 in mice and beef cattle. In beef cattle, ultra low residual level of pDNA vaccine was only found at the injection site. According to rough estimation, consumption of muscles from the injection site represents almost an undetectable intake of pDNA (400 fg/g muscle tissue) for consumers. Residual plasmid in native state will hardly be found at measurable level following further meat processing. This study brings supportive data for animal and food safety and hence for further approval of pDNA vaccine field trials.

Preclinical safety and biodistribution of Sindbis virus measles DNA vaccines administered as a single dose or followed by live attenuated measles vaccine in a heterologous prime-boost regimen

Measles still causes considerable morbidity and mortality among infants and young children in developing countries. To develop a new public health tool to reduce this burden, we designed two Sindbis virus replicon vaccines encoding measles virus (MV) hemagglutinin (H) and fusion (F) proteins (pMSIN-H and pMSINHFdU). Our goal is to administer the vaccines to young infants at 6 and 10 weeks of age to prime the immune system to safely and effectively respond to subsequent immunization at age approximately 14 weeks with the licensed attenuated measles vaccine. In preparation for a phase 1 clinical trial, studies of plasmid distribution, integration, and toxicology were performed in rabbits. Biodistribution was assessed after a single DNA immunization delivered intradermally by needle-free injection. Toxicity was assessed using a heterologous prime-boost regimen consisting of a repeat-dose DNA prime followed by a live-attenuated measles vaccine boost. The only vaccine-related adverse effects observed were minimal transient erythema, edema, and inflammation confined to the injection site. Plasmids were detected in the subcutis and muscle at the site of inoculation. A small proportion of animals exhibited plasmids in the regional lymph nodes. There was no evidence of plasmid integration into the host genome. Both Sindbis-based vaccine plasmids were immunogenic in rabbits; pMSIN-H elicited higher virus-neutralizing antibody levels. Both vaccines were shown to be well tolerated and suitable for clinical trials and they are currently being tested in phase 1 studies in young adults.

What happens to the DNA vaccine in fish? A review of current knowledge

The primary function of DNA vaccines, a bacterial plasmid DNA containing a construct for a given protective antigen, is to establish specific and long-lasting protective immunity against diseases where conventional vaccines fail to induce protection. It is acknowledged that less effort has been made to study the fate, in terms of cellular uptake, persistence and degradation, of DNA vaccines after in vivo administration. However, during the last year some papers have given new insights into the fate of DNA vaccines in fish. By comparing the newly acquired information in fish with similar knowledge from studies in mammals, similarities with regard to transport, blood clearance, cellular uptake and degradation of DNA vaccines have been found. But the amount of DNA vaccine redistributed from the administration site after intramuscular administration seems to differ between fish and mammals. This review presents up-to-date and in-depth knowledge concerning the fate of DNA vaccines with emphasis on tissue distribution, cellular uptake and uptake mechanism(s) before finally describing the intracellular hurdles that DNA vaccines need to overcome in order to produce their gene product.

Detection of supercoiled plasmid DNA and luciferase expression in Atlantic salmon (Salmo salar L.) 535 days after injection

In this study our aim was to investigate the persistence and distribution of plasmid DNA in Atlantic salmon. Atlantic salmon (mean weight 70 g) were injected with 100 microg of plasmid DNA in 100 microl of phosphate buffered saline. The fish were reared in running fresh water at temperature 0-12 degrees C and injections were performed at 8 degrees C. After intramuscular injection, samples were obtained from blood and different tissues and organs up to day 535 after injection. We found by use of Southern blotting open circular and supercoiled plasmid DNA at the injection site and plasmid DNA fragments, assessed by real-time PCR, were detected in some of the examined tissues up to day 535. A co-persistence of luciferase transcript and activity were identified at the injection site up to day 535, however analysis of DAM methylation pattern suggested that the plasmid DNA did not replicate in vivo. Our study indicated that the plasmid DNA can persist for a prolonged time after intramuscular injection.

Genetic vaccination approaches against malaria based on the circumsporozoite protein

Malaria is the world's major parasitic disease, for which effective control measures are urgently needed. Despite considerable efforts, no successful vaccine against malaria has been developed so far. The method of DNA-based immunization offers the possibility to induce both antibody- and cell-mediated immune responses to a variety of antigens. The flexibility of the DNA vaccine technology permits the combination of several antigens from different developmental stages of the parasite's complicated life cycle. This review covers the development of DNA-based immunization against malaria from initial experiments in small animals to recently conducted clinical studies. Focusing on one of the best characterized malaria vaccine candidate antigens, the circumsporozoite protein, an overview of strategies to enhance vaccine efficacy is provided. Advanced application methods such as the gene gun technology or the needle-less jet injection device are described. As DNA vaccination represents a relatively new methodology, safety concerns associated with planned clinical applications are discussed. In summary, this novel type of vaccine has to be considered as a promising tool for future malaria vaccination strategies.

Uptake, biodistribution, and time course of naked plasmid DNA trafficking after intratumoral in vivo jet injection

Nonviral jet injection is an applicable technology for in vivo gene transfer of naked DNA. However, little is known about the biodistribution and clearance of jet-injected DNA, or about its localization within tissue and cells. Therefore, in this study we analyzed the intratumoral and systemic biodistribution of jet-injected naked DNA in human colon carcinoma-bearing NCr-nu/nu mice, which were jet-injected with the pCMVbeta plasmid DNA. Intratumoral and systemic plasmid DNA biodistribution was analyzed 5, 10, 20, and 40 min and 3, 6, 24, 48, and 72 hr after jet injection, using quantitative real-time polymerase chain reaction. In the tumors, a rapid drop in naked DNA load within 24 hr of jet injection was shown. Detailed analysis of intratumoral distribution of rhodamine-labeled DNA revealed the presence of plasmid DNA within tumor cells 5 min after jet injection and further accumulation of significant DNA amounts in the cell nuclei 30 to 60 min after jet injection. In the blood, DNA amounts rapidly dropped within 10 to 40 min of jet injection to less than 0.001 pg of plasmid per 250 ng of tissue DNA and only minimal plasmid DNA dissemination was detected in liver, lung, spleen, kidney, and ovaries, which was cleared 3 to 6 hr after jet injection. By contrast, in heart, bone marrow, and brain almost no plasmid DNA was detectable.

Inhibition of type I allergic responses with nanogram doses of replicon-based DNA vaccines

BACKGROUND

Allergic diseases have become a major public health problem in developed countries; yet, no reliable, safe and consistently effective treatment is available. DNA immunization has been shown to prevent and balance established allergic responses, however, the high dose of conventional DNA vaccines necessary for the induction of anti-allergic reactions and their poor immunogenicity in primates require the development of new allergy DNA vaccines. We evaluated protective and therapeutic effects of a Semliki-Forest Virus replicase-based vs a conventional DNA vaccine in BALB/c mice using the model allergen beta-galactosidase.

METHODS

Immunoglobulin (Ig)E suppression was determined by a basophil release assay as an in vitro correlate for allergen-specific crosslinking capacity of IgE reflecting the in vivo situation in an allergic individual. Th1 memory responses were measured by cytokine detection via enzyme-linked immunosorbent assay (ELISA) and enzyme-linked immunospot assay (ELISPOT).

RESULTS

Nanogram amounts of a replicase-based vector triggered a Th1 response comparable with that achieved with the injection of 20,000-times more copies of a conventional DNA plasmid, and induced IgE suppression in both a protective and a therapeutic setting.

CONCLUSIONS

Replicase-based DNA vaccines fulfill the stringent criteria for an allergy DNA vaccine, i.e. low dose, strong Th1 immunogenicity and memory, lack of 'therapy-induced' IgE production and anaphylactic side effects. Moreover, by triggering apoptosis in transfected cells, their unique 'immunize and disappear' feature minimizes the hypothetical risks of genomic integration or induction of autoimmunity.

Dose-response studies for the elicitation of CD8 T cells by a DNA vaccine, used alone or as the prime for a modified vaccinia Ankara boost

Here, we conduct dose-response studies in mice for the elicitation of CD8 T cells by a DNA vaccine that expresses HIV Gag. For DNA doses ranging from 1 to 100 microg, the studies revealed greater than 10-fold increases in anti-Gag CD8 T cells following a DNA prime or a DNA prime and a constant modified vaccinia Ankara (MVA) boost. These results are in contrast to dose-response studies for MVA vectors expressing Gag, where only 2-3-fold increases in anti-Gag CD8 T cells were elicited by 100-fold increases in dose.

Evaluation of the persistence and gene expression of an anti-Chlamydophila psittaci DNA vaccine in turkey muscle

BACKGROUND

DNA vaccination has been shown to elicit specific cellular and humoral immune responses to many different agents in a broad variety of species. However, looking at a commercial use, the duration of the immune response against the vaccine is critical. Therefore the persistence of the DNA vaccine, as well as its expression, should be investigated. We conducted these investigations on a DNA vaccine against Chlamydophila psittaci, a Gram-negative intracellular bacterium which causes respiratory disease in turkeys and humans. Previous studies showed that the DNA vaccine confers partial protection against C. psittaci infection in turkeys. Turkeys were injected intramuscularly with the DNA vaccine : a eukaryotic expression vector (pcDNA1::MOMP) expressing the major outer membrane protein (MOMP) of an avian C. psittaci serovar D strain. Over a period of 11 weeks, cellular uptake of the DNA vaccine was examined by PCR, transcription of the insert by reverse transcript-PCR (RT-PCR) and mRNA translation by immunofluorescence staining of muscle biopsies.

RESULTS

The results indicate that the DNA vaccine persists in turkey muscle for at least 10 weeks. Moreover, during this period of time MOMP was continuously expressed, as evidenced by the immunofluorescence staining and RT-PCR.

CONCLUSION

Since C. psittaci infections occur at the age of 3 to 6 and 8 to 12 weeks, a vaccine persistence of 10 weeks seems adequate. Therefore, further research should concentrate on improving the elicited immune response, more specifically the cell-mediated immune response, rather than prolonging the lifespan of the plasmid.

Long-term persistence of hepatitis B surface antigen and antibody induced by DNA-mediated immunization results in liver and kidney lesions in mice

DNA-mediated immunization has been recognized as a new approach for prevention and treatment of hepatitis B virus (HBV) infection. However, the side effects of this approach have not been well described. Here we report that DNA-mediated immunization by intramuscular injection of plasmid DNA encoding HBV surface antigen (HBsAg) induced long-term persistence of HBsAg and HBsAg-specific antibody (anti-HBs) in the sera of the immunized BALB/c mice and resulted in liver and kidney lesions. The lesions persisted for 6 months after injection. Lesions were also found in normal mice injected with the sera from immunized mice, and in HBV-transgenic mice injected with anti-HBs antibody, or sera from immunized mice. Furthermore, lesions were accompanied by deposition of circulating immune complex (CIC) of HBsAg and anti-HBs antibody in the damaged organs. These results indicate that long-term persistence of HBsAg and anti-HBs in the immunized mice can result in deposited CIC in liver and kidney, and in development of lesions. The use of DNA containing mammalian replication origins, such as the plasmids used in this study, is not appropriate for human vaccines due to safety concerns relating to persistence of DNA; nevertheless, the safety of DNA-mediated immunization protocols still needs to be carefully evaluated before practical application.

Feasibilty of in utero DNA vaccination following naked gene transfer into pig fetal muscle: Transgene expression, immunity and safety

The high toll of death among first-week infants is due to infections occurring at the end of pregnancy, during birth or by breastfeeding. This problem significantly concerns industrialized countries also. To prevent the typical "first-week infections", a vaccine would be protective as early as at the birth. In utero DNA immunization has demonstrated the effectiveness in inducing specific immunity in newborns. We have already published results of a 2-year follow-up showing long-term safety, protective antibody titers at birth and long-term immune memory, following intramuscular in utero anti-HBV DNA immunization in 90-days pig fetuses. We have now analyzed further parameters of short-term safety. Two different reporter genes were injected in the thigh muscles of 90-days fetuses. At 8 days following DNA injection, we found high-level of transgenes expression in all injected fetuses. A step gradient of expression from the area of injection was observed with both reporter genes. CMV promoter/enhancer produced higher levels of expression compared to SV40 promoter/enhancer. Moreover, no evidence of local or systemic flogistic alterations or fetal malformations, mortality or haemorrhage following intramuscular injection were observed. A single anti-HBV s-antigen DNA immunization in 90-days fetuses supported protective antibody levels in all immunized newborns, lasting at least up to 4 months after birth. Our report further sustains safety and efficacy of intramuscular in utero naked gene transfer and immunization. This approach may support therapeutic or prophylactic procedure in many early life-threatening pathologic conditions.

Tissue distribution of a plasmid DNA encoding Hsp65 gene is dependent on the dose administered through intramuscular delivery

In order to assess a new strategy of DNA vaccine for a more complete understanding of its action in immune response, it is important to determine the in vivo biodistribution fate and antigen expression. In previous studies, our group focused on the prophylactic and therapeutic use of a plasmid DNA encoding the Mycobacterium leprae 65-kDa heat shock protein (Hsp65) and achieved an efficient immune response induction as well as protection against virulent M. tuberculosis challenge. In the present study, we examined in vivo tissue distribution of naked DNA-Hsp65 vaccine, the Hsp65 message, genome integration and methylation status of plasmid DNA. The DNA-Hsp65 was detectable in several tissue types, indicating that DNA-Hsp65 disseminates widely throughout the body. The biodistribution was dose-dependent. In contrast, RT-PCR detected the Hsp65 message for at least 15 days in muscle or liver tissue from immunized mice. We also analyzed the methylation status and integration of the injected plasmid DNA into the host cellular genome. The bacterial methylation pattern persisted for at least 6 months, indicating that the plasmid DNA-Hsp65 does not replicate in mammalian tissue, and Southern blot analysis showed that plasmid DNA was not integrated. These results have important implications for the use of DNA-Hsp65 vaccine in a clinical setting and open new perspectives for DNA vaccines and new considerations about the inoculation site and delivery system.

Multigene/Multisubtype HIV-1 Vaccine Induces Potent Cellular and Humoral Immune Responses by Needle-Free Intradermal Delivery

Gene vaccination encounters problems different from those of gene therapy since both a short half-life of the gene and a strong immune response to the gene product are desirable. We have evaluated a DNA vaccine consisting of seven plasmids encoding nine HIV-1 proteins. Using a needle-free delivery device, the Biojector, together with recombinant mouse GM-CSF, this vaccine induced strong gp160 Env- and p24 Gag-specific cellular and humoral immune responses in mice. The rGM-CSF was crucial for inducing both antibodies and antigen-specific CD8(+) T cell responses against both gp160 and p24. A GMP-produced lot of this vaccine, intended for human use, was delivered intradermally or intramuscularly into BALB/c mice at a GLP-accredited animal facility. This vaccine induced strong cellular responses independent of the route of immunization; moreover, no signs of toxicity were detected after histopathological examination of various tissues. Overall, the results indicate that the intradermal delivery of multigene/multisubtype HIV DNA in combination with recombinant GM-CSF is a safe and efficacious strategy for inducing high levels of specific CD8(+) T cells and unusually high titers of antibodies. This vaccine has been approved by the Swedish Medicinal Products Agency and is currently in a Phase I clinical trial.

Adjuvant Action of MurineIL-2/IgPlasmid After Intramuscular Immunization With Indian HIV-1 Subtype C Recombinantenv.gp120 Construct

The human immunodeficiency virus (HIV) epidemic is probably the greatest scourge to affect mankind in the 20th century. Containment of the acquired immunodeficiency syndrome (AIDS) epidemic will require an effective vaccine. Of various vaccine approaches, immunization with DNA plasmids containing HIV-1 structural genes is the most popular approach. However, an important limitation of DNA immunization is that these responses are relatively weak and are often only transient in their nature. The use of immunologic adjuvants together with DNA vaccines is a promising way to enhance and to optimize DNA-derived immunity. Cytokines have been widely used to enhance the immune responses of DNA vaccines. In the present investigation, we studied the in vivo immunomodulation of HIV-1 Indian subtype C plasmid construct (pJWSK3, encoding envgp120 gene) by plasmid-based murine IL-2/Ig construct. Subcloning of mIL-2/Ig gene from pVRCmIL-2/Ig construct into pJW4304 vector was done followed by its in vitro expression study on the COS-7 cell line. Co-immunization of the recombinant HIV-1 env-gp120 construct with the IL-2/Ig construct in the female Balb/c mice by the intramuscular route resulted in induction of significantly higher levels of both HIV-1-specific antibody response and cell mediated immune response than by DNA plasmid construct alone (p < 0.001 and p < 0.05, respectively). The induced HIV-1-specific murine IFN-gamma response was robust, broad based, and seen even at the end of 6 months after immunization. Taken together these results indicate that the strategy of using IL-2/Ig plasmid can be highly effective when used along with recombinant DNA constructs and serve as the potential tool for the development of more rationally designed vaccines against HIV-1.

Tissue distribution of a plasmid DNA containing epitopes of foot-and-mouth disease virus in mice

It is known that only the minority of plasmid DNAs effect a cure or prevention after intramuscular injection into host. But what is the fate of the majority? And indeed how many of the injected DNAs work? Till now, little is known about it. To answer these questions, two methods including PCR and autoradiography were used in distribution study in mice that had received a single muscular inoculation of plasmid DNA containing antigenic epitopes of foot-and-mouth disease virus. The results showed that the plasmid DNAs were distributed by blood circulation and degraded soon. The degradation ratio of super coiled plasmid DNA was 20.9% in 10 min, 34.1% in 1h, 86.8% in 1 day and 97.8% in 1 week in sera in vivo. And over a half of the whole were output in urine and faeces. The rest resided most in muscles as 'antigen pool', next in immune organs, kidney, liver, heart, lung and little in brain or gonad. About 40% or 0.5% of total plasmid DNAs, inferring to be effective, resided in muscles or immune organs, respectively. Collective results suggested that 'nude' DNA, as water injection, was characterized as quick absorbent, extensive distribution, but low utilization rate. Finally, the immune mechanism for the DNA vaccine was discussed.

Pharmacokinetics and Biodistribution of a pGT2-VEGF Plasmid DNA After Administration in Rats

Intramyocardial administration of gene therapy vectors expressing angiogenic factors have been attempted as an alternative to conventional surgical methods for the management of myocardial ischemia. In this study, we have developed the pGT2-VEGF, a plasmid DNA vector expressing human VEGF165, for the management of ischemic cardiovascular disease and investigated in vivo pharmacokinetics and tissue distribution of pGT2-VEGF after intramyocardial and intravenous administration in rats. A high concentration of pGT2-VEGF was observed in the heart after intramyocardial injection of 300 microg, which is in line with the assumption that direct intramyocardial delivery enables extended localization at the administration site. Leakage of the pGT2-VEGF to the blood circulation was observed after intramyocardial injection, with an area under the curve (AUC) of 3.8 microg min/mL, as compared with 37.3 microg min/mL after intravenous injection of the same dose. The pGT2-VEGF concentration in blood peaked at 5 minutes after intramyocardial administration and declined rapidly to undetectable levels by 2 hours post-administration. In tissue distribution studies, pGT2-VEGF peaked at 5 minutes post-administration in various organs but was undetectable at 2 hours in all organs except heart, lung, and liver. Taken together, the results suggest that intramyocardial-delivered pGT2-VEGF was degraded rapidly in vivo and mainly persisted in target tissues, the heart. In addition, intramyocardial-administered pGT2-VEGF was expressed for longer periods than the persistence of the pGT2-VEGF plasmid DNA in a target tissue. Therefore, a direct myocardial injection of pGT2-VEGF might be useful for local therapeutic angiogenesis.

Effects of Epitopes Combination and Adjuvants on Immune Responses to Anti-Alzheimer Disease DNA Vaccines in Mice

Alzheimer disease (AD) is a neurodegenerative disorder characterized by neuropathological hallmarks including deposits of the beta-amyloid peptide (AssP). Studies have shown that immunization with Abeta42 peptide reduces both the spatial memory impairments and Alzheimer disease-like neuropathologic changes in Alzheimer disease transgenic mice, but can cause side effect of a cell-mediated autoimmune meningoencephalitis. Recently, some studies showed that DNA vaccination could be used to generate an antibody response to Abeta without the adverse cell-mediated immune effect. In the current study, we generate four DNA vaccine plasmids (pV-GE1, pV-GE2, pV-GE3, and pV-GE4) against Alzheimer disease by separately fusing Abeta epitope sequences (coding for EFGH, DAEFGH, EFGH+EFGH, and EFGH+DAEFGH) with IgG heavy chain coding region of mouse. Meanwhile, the full-length gene Abeta encoding plasmid (pV-Abeta), empty vector (pVAX) and synthetic AssP were also included as control. The sera of BALB/c mice immunized via intramuscular with plasmids and peptide were tested by indirect ELISA for auto-AssP immunoreactivity. The results showed that all the DNA vaccine plasmids induced AssP-specific antibodies; moreover pV-GE2 and pV-Abeta constructs elicited higher antibody titers than other constructs (P < 0.05). To further enhance the immune response, GM-CSF encoding plasmid (pGM-CSF) and purified BCG-DNA were used as molecular adjuvants. BCG-DNA could enhance humoral and cellular immune responses simultaneously and did not alter the phenotype of the immune responses, whereas pGM-CSF showed no obvious effect on immune response. These results suggest that this immunization strategy of using Abeta epitope encoding plasmid plus BCG-DNA adjuvant may serve as the basis for developing anti-Alzheimer disease vaccines.

I. Poloxamer-Formulated Plasmid DNA-Based Human Cytomegalovirus Vaccine: Evaluation of Plasmid DNA Biodistribution/Persistence and Integration

Preclinical studies were conducted in mice and rabbits to evaluate biodistribution/persistence and potential integration of plasmid DNA (pDNA) after intramuscular administration of a poloxamer-formulated pDNAbased vaccine, VCL-CT01, encoding gB, pp65, and IE1 human cytomegalovirus (hCMV) immunogens. Tissue distribution in mice vaccinated with VCL-CT01 was compared with that in mice vaccinated with a phosphate- buffered saline (PBS)-formulated control pDNA vaccine. Residual pDNA copy number (PCN), in selected tissues collected on days 3, 30, and 60 after vaccination, was measured by quantitative polymerase chain reaction. In VCL-CT01-vaccinated mice and in control pDNA-vaccinated mice, pDNA was below the limit of detection by day 60 in all tissues except the injection site. Clearance of pDNA from the injection site was slower in VCL-CT01-vaccinated mice compared with PBS-pDNA-vaccinated mice. An integration study was conducted in rabbits to determine whether pDNA integration into the genome of the vaccinated animal contributed to pDNA persistence. Residual pDNA in VCL-CT01-injected rabbit muscle collected 60 days after vaccination (geometric mean of 1085 PCN/microg total DNA) was comparable to that observed in VCL-CT01- injected mouse muscle (geometric mean of 1471 PCN/microg total DNA) collected at the same time point. pDNA integration was not detectable by column agarose gel electrophoresis despite the persistence of pDNA at the injection site 60 days after vaccination. Therefore the risk of genomic integration of hCMV pDNA formulated with poloxamer was considered negligible.

A differential proteome in tumors suppressed by an adenovirus-based skin patch vaccine encoding human carcinoembryonic antigen

We created an anti-tumor vaccine by using adenovirus as a vector which contains a cytomegalovirus early promoter-directed human carcinoembryonic antigen gene (AdCMV-hCEA). In an attempt to develop the skin patch vaccine, we epicutaneously vaccinated Balb/c mice with AdCMV-hCEA. After nine weeks post-immunization, vaccinated mice evoked a robust antibody titer to CEA and demonstrated the capability of suppressing in vivo growth of implanted murine mammay adenocarioma cell line (JC-hCEA) tumor cells derived from a female Balb/c mouse. Proteomic analysis of the tumor masses in the non-vaccinated naive and vaccinated mice reveal that six proteins change their abundance in the tumor mass. The levels of adenylate kinase 1, beta-enolase, creatine kinase M chain, hemoglobin beta chain and prohibitin were statistically increased whereas the level of a creatine kinase fragment, which is undocumented, was decreased in the tumor of vaccinated mice. These proteins may provide a vital link between early-stage tumor suppression and immune response of skin patch vaccination.

Analysis of DNA-vaccinated fish reveals viral antigen in muscle, kidney and thymus, and transient histopathologic changes

A highly efficacious DNA vaccine against a fish rhabdovirus, infectious hematopoietic necrosis virus (IHNV), was used in a systematic study to analyze vaccine tissue distribution, persistence, expression patterns, and histopathologic effects. Vaccine plasmid pIHNw-G, containing the gene for the viral glycoprotein, was detected immediately after intramuscular injection in all tissues analyzed, including blood, but at later time points was found primarily in muscle tissue, where it persisted to 90 days. Glycoprotein expression was detected in muscle, kidney, and thymus tissues, with levels peaking at 14 days and becoming undetectable by 28 days. Histologic examination revealed no vaccine-specific pathologic changes at the standard effective dose of 0.1 mug DNA per fish, but at a high dose of 50 mug an increased inflammatory response was evident. Transient damage associated with needle injection was localized in muscle tissue, but by 90 days after vaccination no damage was detected in any tissue, indicating the vaccine to be safe and well tolerated.

Human Clinical Trials of Plasmid DNA Vaccines

This article gives an overview of DNA vaccines with specific emphasis on the development of DNA vaccines for clinical trials and an overview of those trials. It describes the preclinical research that demonstrated the efficacy of DNA vaccines as well as an explication of the immunologic mechanisms of action. These include the induction of cognate immune responses, such as the generation of cytolytic T lymphocytes (CTL) as well as the effect of the plasmid DNA upon the innate immune system. Specific issues related to the development of DNA as a product candidate are then discussed, including the manufacture of plasmid, the qualification of the plasmid DNA product, and the safety testing necessary for initiating clinical trials. Various human clinical trials for infectious diseases and cancer have been initiated or completed, and an overview of these trials is given. Finally, because the early clinical trials have shown less than optimal immunogenicity, methods to increase the potency of the vaccines are described.

Biodistribution and general safety of a naked DNA plasmid, GTU®-MultiHIV, in a rat, using a quantitative PCR method

We studied the general safety, biodistribution and persistence of a naked DNA plasmid in a rat model using intramuscular, intradermal and intravenous routes of administration. Clinical signs were followed up throughout the study and at the necropsy. Tissue samples were collected at the necropsy at 2, 14 and 28 days after injection of 200 microg of plasmid DNA and analysed with validated quantitative polymerase chain reaction (QPCR). The plasmid (GTU-MultiHIV) was shown to be well tolerated and no clinical observations related to the vaccine were found. Within 2 days after the intramuscular and intradermal injections, the plasmid could be detected in the lymph nodes and also at 14 days in a few test animals. The quantitative PCR analysis indicated that in positive lymph nodes one of 15-213 dendritic cells could be carrying the plasmid. No plasmid was detected in gonads or brain samples in any of the study groups. In intramuscular and intradermal administration, low amounts of the plasmid DNA persisted at the injection site 28 days after the injection, whereas a complete clearance with intravenous route was observed already at 14 days. The results show that the GTU-MultiHIV plasmid is safe and suitable for human clinical trials.

Microparticles for the delivery of DNA vaccines

DNA vaccines have demonstrated a lack of adequate potency in humans, which has necessitated the exploration of various adjunct technologies. Inefficient delivery of DNA vaccines, particularly to antigen-presenting cells, may be contributing to this lack of potency. One effective means of facilitating delivery of DNA vaccines to APCs is through the use of microparticles. In this article, we review the background and rationale for microparticles as a vaccine delivery system, data demonstrating their utility and mode of action for DNA delivery, and the prospects for their development.

Recent advancement in flavivirus vaccine development

Lately, the magnitude of cumulative diseases burden caused by flaviviruses, such as dengue virus, Japanese encephalitis virus, tick-borne encephalitis virus, West Nile virus and yellow fever virus, has reached an unprecedented level with the sizes of human and animal populations at risk increasing sharply. These diseases present highly complex medical, economic and ecologic problems, some effecting primarily human and others affecting human, livestock and wildlife. The large body of recent publications on the development of vaccines taking advantage of new generations of bio-engineering techniques clearly reflects the profound interests and deep sense of urgency in the scientific and medical communities in combating those diseases. This review reveals a collection of remarkable progresses thus far made in flaviviral vaccine research not only employing a diverse range of new strategies but also re-tooling old techniques to improve the existing vaccines. The efficacy and safety of some of the new vaccine candidates have been evaluated and proven in human clinical trials. Besides the technical advancement in vaccine development, in this review, the importance of somewhat neglected and yet critical subjects, such as adequacy of animal model, vaccine safety, vaccine formulation and delivery, complication in serodiagostics and economic factor, was examined in-depth.

Gene transfer vector biodistribution: pivotal safety studies in clinical gene therapy development

Techniques allowing for gene transfer vectors biodistribution investigation, in the frame of preclinical gene therapy development, are exposed. Emphasis is given on validation and test performance assessment. In the second part, specific gene vector distribution properties are reviewed (adenovirus, AAV, plasmid, retroviruses, herpes-derived vectors, germline transmission risks). The rationale for biodistribution by quantitative PCR, animal study and result interpretation is discussed. The importance and pivotal role of biodistribution study in gene transfer medicine development is shown through the determination of target organs for toxicity, germline transmission assessment and determination of risks of shedding and spreading of vectors in the gene transfer recipient and the environment.

Enhancement of DNA vaccine potency in rhesus macaques by electroporation

The potency of an HIV DNA vaccine was enhanced in rhesus macaques by in vivo electroporation, as judged by increased onset, magnitude and duration of antibody and cell-mediated immune responses against both components of a combination Gag and Env vaccine. These data demonstrate the utility of the electroporation technology for use in large animals.

Immune response at birth, long-term immune memory and 2 years follow-up after in-utero anti-HBV DNA immunization

Infections occurring at the end of pregnancy, during birth or by breastfeeding are responsible for the high toll of death among first-week infants. In-utero DNA immunization has demonstrated the effectiveness in inducing specific immunity in newborns. A major contribution to infant immunization would be achieved if a vaccine proved able to be protective as early as at the birth, preventing the typical 'first-week infections'. To establish its potential for use in humans, in-utero DNA vaccination efficiency has to be evaluated for short- and long-term safety, protection at delivery, efficacy of boosts in adults and effective window/s for modulation of immune response during pregnancy, in an animal model suitable with human development. Here we show that a single intramuscular in-utero anti-HBV DNA immunization at two-thirds of pig gestation produces, at birth, antibody titers considered protective in humans. The boost of antibody titers in every animal following recall at 4 and 10 months demonstrates the establishment of immune memory. The safety of in-utero fetus manipulation is guaranteed by short-term (no fetus loss, lack of local alterations, at-term spontaneous delivery, breastfeeding) and long-term (2 years) monitoring. Treatment of fetuses closer to delivery results in immune ignorance without induction of tolerance. This result highlights the repercussion of selecting the appropriate time point when this approach is used to deliver therapeutic genes. All these findings illustrate the relevance of naked DNA-based vaccination technology in therapeutic efforts aimed to prevent the high toll of death among first-week infants.

Protection against collagen-induced arthritis by intramuscular gene therapy with an expression plasmid for the interleukin-1 receptor antagonist

The interleukin-1 receptor antagonist (IL-1Ra) is an endogenous protein that can prevent the binding of IL-1 to its cell-surface receptors. Among a number of techniques for gene transfer in vivo, the direct injection of naked DNA into muscle is simple, inexpensive and safe. In this study, we evaluated the potential of intramuscular gene therapy with plasmid DNA containing the cDNA for IL-1Ra in the prevention of murine collagen-induced arthritis (CIA). DBA/1 mice were immunized with bovine type II collagen. At 4 weeks after the initial immunization, expression plasmid for IL-1Ra was injected into four selected sites in the thigh and calf muscles of DBA/1 mice. Control mice received the same plasmid, but lacking the IL-1Ra coding sequence. Macroscopic analysis of paws for redness, swelling and deformities showed that the onset of moderate to severe CIA in the paws of mice injected with IL-1Ra DNA was significantly prevented (P<0.05). In addition, both the synovitis and the cartilage erosion in knee joints were dramatically reduced in mice treated with IL-1Ra DNA (P<0.05). The expression of IL-1beta was significantly decreased in the ankle joints of mice treated with IL-1Ra (P<0.01). Interestingly, the levels of IL-1Ra in sera and joints after intramuscular injection of IL-1Ra DNA were significantly lower than when protein had been used in previous reports, suggesting that the therapeutic effect may be achieved by an alternative mechanism(s) rather than by systemic elevation of IL-1Ra. These observations provide the first evidence that direct intramuscular injection of expression plasmid for IL-1Ra may effectively suppress the inflammatory pathology in arthritis.

Safety of interleukin-12 gene therapy against cancer: a murine biodistribution and toxicity study

As a prerequisite for a human clinical trial using interleukin (IL)-12 gene therapy, the biodistribution and safety of IL-12, administered as an intradermal naked DNA injection, was evaluated in mice. The pNGVL3-mIL12 plasmid used in this study is a nonviral vector designed to induce a high level of IL-12 protein expression during a transient transfection of the host cell. The biodistribution was evaluated by a polymerase chain reaction (PCR) assay that is capable of detecting less than 100 copies of the plasmid in the context of host DNA. Twenty-four hours after three intradermal injections of 0.5 microg or 5 microg of pNGVL3-mIL12 plasmid, the plasmid was detectable in various internal organs, the blood, and the injection site. The plasmid was detectable in the gonads of only one animal at the high-dose treatment 24 hr after the injections. In the majority of the organs the plasmid was undetectable throughout the study. Possible side effects were monitored by histology and clinical chemistry, and the level of IL-12 protein expression was assessed by enzyme-linked immunosorbent assay (ELISA). No treatment-related histologic abnormalities were detected and the blood chemistry parameters showed no toxicity. The IL-12 protein was undetectable at all times at the injection site and interferon (IFN)-gamma levels at the injection site and in the serum were at background levels. The results of this murine safety study indicate that based on the distribution pattern of the plasmid in the body and the undetectable toxicities in the tissues, the use of the pNGVL3-hIL12 plasmid in cancer gene therapy clinical trials can be considered as safe.