Phase I randomized clinical trial of VRC DNA and rAd5 HIV-1 vaccine delivery by intramuscular (i.m.), subcutaneous (s.c.) and intradermal (i.d.) administration (VRC 011)

Clinical perspective on topical vaccination strategies

Vaccination is one of the most successful measures in modern medicine to combat diseases, especially infectious diseases, and saves millions of lives every year. Vaccine design and development remains critical and involves many aspects, including the choice of platform, antigen, adjuvant, and route of administration. Topical vaccination, defined herein as the introduction of a vaccine to any of the three layers of the human skin, has attracted interest in recent years as an alternative vaccination approach to the conventional intramuscular administration because of its potential to be needle-free and induce a superior immune response against pathogens. In this review, we describe recent progress in developing topical vaccines, highlight progress in the development of delivery technologies for topical vaccines, discuss potential factors that might impact the topical vaccine efficacy, and provide an overview of the current clinical landscape of topical vaccines.

Targeting enhanced neutralizing antibody responses via increased germinal center activity: early-phase vaccine trials with novel clinical designs

PURPOSE OF REVIEW

Recent advances in the understanding of the difficult immunologic requirements for the induction of broadly neutralizing antibodies for HIV have spurred interest in optimizing vaccine approaches intended to stimulate a robust germinal center reaction. In preclinical models, techniques to optimize the germinal center response have included alterations in the timing, dose, and delivery method of immunogens and have resulted in substantially enhanced germinal center responses in lymph nodes and neutralizing antibodies in serum. One of the most promising approaches involves splitting the initial dose of vaccine into a series of gradual escalating doses administration ("fractional escalating doses"). In principle, these techniques may have broad implications for vaccines targeting a robust antibody response.

RECENT FINDINGS

We review the upcoming vaccine trials that will test these concepts in clinical practice. The trials include both HIV and non-HIV immunogens, and will involve testing these concepts in both healthy adults and immunocompromised persons.

SUMMARY

There are multiple trials that will test whether techniques to alter vaccine delivery such as fractional escalating doses enhances immunologic outcomes.

Lipid nanoparticles technology in vaccines: Shaping the future of prophylactic medicine

Throughout decades, the intrinsic power of the immune system to fight pathogens has inspired researchers to develop techniques that enable the prevention or treatment of infections via boosting the immune response against the target pathogens, which has led to the evolution of vaccines. The recruitment of Lipid nanoparticles (LNPs) as either vaccine delivery platforms or immunogenic modalities has witnessed a breakthrough recently, which has been crowned with the development of effective LNPs-based vaccines against COVID-19. In the current article, we discuss some principles of such a technology, with a special focus on the technical aspects from a translational perspective. Representative examples of LNPs-based vaccines against cancer, COVID-19, as well as other infectious diseases, autoimmune diseases, and allergies are highlighted, considering the challenges and promises. Lastly, the key features that can improve the clinical translation of this area of endeavor are inspired.

Effectiveness and safety of tetanus vaccine administration by intramuscular vs. subcutaneous route in anticoagulated patients: Randomized clinical trial in primary care

Design

Prospective, double-blind clinical trial comparing tetanus-diphtheria vaccine administration routes, intramuscular (IM) vs. subcutaneous (SC) injection, in patients with oral anticoagulants. ISRCTN69942081.

Study population

Patients treated with oral anticoagulants, 15 health centers, Vigo (Spain). Sample size, 117 in each group.

Outcome variables

Safety analysis: systemic reactions and, at the vaccine administration site, erythematic, swelling, hematoma, granuloma, pain.Effectiveness analysis: differences in tetanus toxoid antibody titers.Independent variables: route, sex, age, baseline serology, number of doses administered.

Analysis

Following the CONSORT guidelines, we performed an intention-to-treat analysis. We conducted a descriptive study of the variables included in both groups (117 in each group) and a bivariate analysis. Fewer than 5% of missing values. Imputation in baseline and final serology with the median was performed. Lost values were assumed to be values missing at random. We conducted a descriptive study of the variables and compared routes. For safety, multivariate logistic regression was applied, with each safety criterion as outcome and the independent variables. Odds ratios (ORs) were calculated. For effectiveness, a generalized additive mixed model, with the difference between final and initial antibody titers as outcome. Due to the bimodal distribution of the outcome, the normal mixture fitting with gamlssMX was used. All statistical analyses were performed with the gamlss.mx and texreg packages of the R free software environment.

Results

A previously published protocol was used across the 6-year study period. The breakdown by sex and route showed: 102 women and 132 men; and 117 IM and 117 SC, with one dose administered in over 80% of participants. There were no differences between groups in any independent variable. The second and third doses administered were not analyzed, due to the low number of cases. In terms of safety, there were no severe general reactions. Locally, significant adjusted differences were observed: in pain, by sex (male, OR: 0.39) and route (SC, OR: 0.55); in erythema, by sex (male, OR: 0.34) and route (SC, OR: 5.21); and in swelling, by sex (male, OR: 0.37) and route (SC, OR: 2.75). In terms of effectiveness, the model selected was the one adjusted for baseline serology.

Nanovaccine Delivery Approaches and Advanced Delivery Systems for the Prevention of Viral Infections: From Development to Clinical Application

Viral infections causing pandemics and chronic diseases are the main culprits implicated in devastating global clinical and socioeconomic impacts, as clearly manifested during the current COVID-19 pandemic. Immunoprophylaxis via mass immunisation with vaccines has been shown to be an efficient strategy to control such viral infections, with the successful and recently accelerated development of different types of vaccines, thanks to the advanced biotechnological techniques involved in the upstream and downstream processing of these products. However, there is still much work to be done for the improvement of efficacy and safety when it comes to the choice of delivery systems, formulations, dosage form and route of administration, which are not only crucial for immunisation effectiveness, but also for vaccine stability, dose frequency, patient convenience and logistics for mass immunisation. In this review, we discuss the main vaccine delivery systems and associated challenges, as well as the recent success in developing nanomaterials-based and advanced delivery systems to tackle these challenges. Manufacturing and regulatory requirements for the development of these systems for successful clinical and marketing authorisation were also considered. Here, we comprehensively review nanovaccines from development to clinical application, which will be relevant to vaccine developers, regulators, and clinicians.

Intramuscular and Intradermal Electroporation of HIV-1 PENNVAX-GP® DNA Vaccine and IL-12 Is Safe, Tolerable, Acceptable in Healthy Adults

Background: Several techniques are under investigation to improve the immunogenicity of HIV-1 DNA vaccine candidates. DNA vaccines are advantageous due to their ease of design, expression of multiple antigens, and safety.

METHODS

The HVTN 098 trial assessed the PENNVAX^®-GP DNA vaccine (encoding HIV env, gag, pol) administered with or without plasmid IL-12 at 0-, 1-, 3-, and 6-month timepoints via intradermal (ID) or intramuscular (IM) electroporation (EP) in healthy, adult participants. We report on safety, tolerability, and acceptability.

RESULTS

HVTN 098 enrolled 94 participants: 85 received PENNVAX^®-GP and nine received placebo. Visual analog scale (VAS) pain scores immediately after each vaccination were lower in the ID/EP than in the IM/EP group (medians 4.1-4.6 vs. 6-6.5, p < 0.01). IM/EP participants reported greater pain and/or tenderness at the injection site. Most ID/EP participants had skin lesions such as scabs/eschars, scars, and pigmentation changes, which resolved within 6 months in 51% of participants (24/55). Eighty-two percent of IM/EP and 92% of ID/EP participant survey responses showed acceptable levels of discomfort.

CONCLUSIONS

ID/EP and IM/EP are distinct experiences; however, HIV-1 DNA vaccination by either route was safe, tolerable and acceptable by most study participants.

Subcutaneous vaccine administration - an outmoded practice

Subcutaneous vaccine (SC) administration is an outmoded practice which complicates vaccine administration recommendations. Local adverse events following immunization (AEFIs) are a recognized determinant of vaccine hesitancy/refusal which can lead to an increased prevalence of vaccine-preventable disease.

This extensive narrative review provides high-grade evidence that intramuscular (IM) administration of all vaccine types [adjuvanted, live virus and non-adjuvanted (inactivated whole cell, split cell and subunit)] significantly reduces the likelihood of local adverse events. This, combined with moderate grade evidence that IM injection generates significantly greater immune response compared with SC injection, allows a strong recommendation to be made for the IM injection of all vaccines except BCG and Rotavirus.

This will simplify vaccination practice, minimize the inadvertent misadministration of vaccines and potentially improve public trust in vaccination.

Safety and immunogenicity of the therapeutic vaccine TG1050 in chronic hepatitis B patients: a phase 1b placebo-controlled trial

Treatment of chronic hepatitis B (CHB) typically requires life-long administration of drugs. Cohort and pre-clinical studies have established the link between a functional T-cell-mounted immunity and resolution of infection. TG1050 is an adenovirus 5-based vaccine that expresses HBV polymerase and domains of core and surface antigen and has shown immunogenicity and antiviral effects in mice. We performed a phase 1 clinical trial to assess safety and explore immunogenicity and early efficacy of TG1050 in CHB patients. This randomized, double blind, placebo-controlled study included two sequential phases: one single dose cohort (SD, n = 12) and one multiple (3) doses cohort (MD, n = 36). Patients, virally suppressed under nucleoside(d)tide analog NUC therapy, were randomized 1:1:1 across 3 dose levels (DL) and assigned to receive 10⁹, 10¹⁰, 10¹¹ virus particles (vp) of TG1050 and then randomized within each DL to placebo (3:1 and 9:3 vaccines/placebo in each DL, respectively, for the SD and MD cohorts). Cellular (ELISPOT) and antibody responses (anti-Adenovirus), as well as evolution of circulating HBsAg and HBcrAg, were monitored. All doses were well tolerated in both cohorts, without severe adverse event. TG1050 was capable to induce IFN-γ producing T-cells targeting 1 to 3 encoded antigens, in particular at the 10¹⁰vp dose. Overall, minor decreases of HBsAg were observed while a number of vaccinees reached unquantifiable HBcrAg by end of the study. In CHB patients under NUC, TG1050 exhibited a good safety profile and was capable to induce HBV-specific cellular immune response. These data support further clinical evaluation, especially in combination studies.

Protective effect of a polyvalent influenza DNA vaccine in pigs

BACKGROUND

Influenza A virus in swine herds represents a major problem for the swine industry and poses a constant threat for the emergence of novel pandemic viruses and the development of more effective influenza vaccines for pigs is desired. By optimizing the vector backbone and using a needle-free delivery method, we have recently demonstrated a polyvalent influenza DNA vaccine that induces a broad immune response, including both humoral and cellular immunity.

OBJECTIVES

To investigate the protection of our polyvalent influenza DNA vaccine approach in a pig challenge study.

METHODS

By intradermal needle-free delivery to the skin, we immunized pigs with two different doses (500μg and 800μg) of an influenza DNA vaccine based on six genes of pandemic origin, including internally expressed matrix and nucleoprotein and externally expressed hemagglutinin and neuraminidase as previously demonstrated. Two weeks following immunization, the pigs were challenged with the 2009 pandemic H1N1 virus.

RESULTS

When challenged with 2009 pandemic H1N1, 0/5 vaccinated pigs (800μg DNA) became infected whereas 5/5 unvaccinated control pigs were infected. The pigs vaccinated with the low dose (500μg DNA) were only partially protected. The DNA vaccine elicited binding-, hemagglutination inhibitory (HI) - as well as cross-reactive neutralizing antibody activity and neuraminidase inhibiting antibodies in the immunized pigs, in a dose-dependent manner.

CONCLUSION

The present data, together with the previously demonstrated immunogenicity of our influenza DNA vaccine, indicate that naked DNA vaccine technology provides a strong approach for the development of improved pig vaccines, applying realistic low doses of DNA and a convenient delivery method for mass vaccination.

An escalating dose study to assess the safety, tolerability and immunogenicity of a Herpes Simplex Virus DNA vaccine, COR-1

This paper describes a single site, open-label Phase I clinical trial evaluating the safety, tolerability and immunogenicity in healthy volunteers of a herpes simplex polynucleotide vaccine that has previously been shown to enhance immunogenicity and protect against lethal herpes simplex virus type 2 (HSV-2) challenge in mice. Five escalating doses of the vaccine, COR-1, were given by intradermal injection to HSV-1 and 2 seronegative healthy individuals. COR-1 was found to be safe and well-tolerated; the only vaccine-related adverse events were mild. While vaccine-induced antibody responses were not detectable, cell-mediated immune responses to HSV-specific peptide groups were identified in 19 of the 20 subjects who completed the study, and local inflammation at the immunisation site was observed. This study indicates COR-1 has potential to be used as a therapeutic vaccine for HSV-2 infection.

A Plasmodium vivax Plasmid DNA- and Adenovirus-Vectored Malaria Vaccine Encoding Blood-Stage Antigens AMA1 and MSP142 in a Prime/Boost Heterologous Immunization Regimen Partially Protects Aotus Monkeys against Blood-Stage Challenge

Malaria is caused by parasites of the genus Plasmodium, which are transmitted to humans by the bites of Anopheles mosquitoes. After the elimination of Plasmodium falciparum, it is predicted that Plasmodium vivax will remain an important cause of morbidity and mortality outside Africa, stressing the importance of developing a vaccine against P. vivax malaria. In this study, we assessed the immunogenicity and protective efficacy of two P. vivax antigens, apical membrane antigen 1 (AMA1) and the 42-kDa C-terminal fragment of merozoite surface protein 1 (MSP1₄₂) in a plasmid recombinant DNA prime/adenoviral (Ad) vector boost regimen in Aotus monkeys. Groups of 4 to 5 monkeys were immunized with plasmid DNA alone, Ad alone, prime/boost regimens with each antigen, prime/boost regimens with both antigens, and empty vector controls and then subjected to blood-stage challenge. The heterologous immunization regimen with the antigen pair was more protective than either antigen alone or both antigens delivered with a single vaccine platform, on the basis of their ability to induce the longest prepatent period and the longest time to the peak level of parasitemia, the lowest peak and mean levels of parasitemia, the smallest area under the parasitemia curve, and the highest self-cure rate. Overall, prechallenge MSP1₄₂ antibody titers strongly correlated with a decreased parasite burden. Nevertheless, a significant proportion of immunized animals developed anemia. In conclusion, the P. vivax plasmid DNA/Ad serotype 5 vaccine encoding blood-stage parasite antigens AMA1 and MSP1₄₂ in a heterologous prime/boost immunization regimen provided significant protection against blood-stage challenge in Aotus monkeys, indicating the suitability of these antigens and this regimen for further development.

Clinical Use of DNA Vaccines

Owing to their unique advantages in simplicity, safety, scalability, and possibility of repeated administrations, DNA vaccines represent an appealing and competitive immunization approach for a wide array of conditions, including but not limited to infectious diseases and cancer immunotherapy. Despite the exciting efficacy observed in preclinical studies, DNA vaccines have faced challenges in inducing strong immune responses in humans. This unexpected poor immunogenicity has severely hampered the translation of DNA vaccines from investigational medications to licensed products. To overcome this obstacle, tremendous efforts have been made to improve antigen expression and enhance immunogenicity. Among these endeavors, in vivo DNA electroporation (EP) has proved to be a breakthrough technology capable of mediating efficient DNA uptake and resulting in enhanced antigen expression and vaccine immunogenicity. EP-mediated DNA delivery has become one of the major platforms used in clinical trials to evaluate DNA vaccines in humans. In this chapter, in addition to EP delivery, other progress made in DNA vaccine development including plasmid optimization, antigen design, and immunologic adjuvants is also reviewed. Finally, the use of DNA vaccines in the context of clinical trials for infectious diseases and cancer immunotherapy is summarized. Specifically, the strategies that allow DNA vaccines to overcome antigenic diversity for viral infection and break immune tolerance for cancer therapy are explored. Based on the advantages of DNA vaccines and the immense progress, led by the electroporation-mediated vaccine delivery, DNA vaccines appear to have the potential to fundamentally transform the vaccine field, providing important benefits for preventing and curing diseases.

Safety and Immunogenicity of a rAd35-EnvA Prototype HIV-1 Vaccine in Combination with rAd5-EnvA in Healthy Adults (VRC 012)

BACKGROUND

VRC 012 was a Phase I study of a prototype recombinant adenoviral-vector serotype-35 (rAd35) HIV vaccine, the precursor to two recently published clinical trials, HVTN 077 and 083. On the basis of prior evaluation of multiclade rAd5 HIV vaccines, Envelope A (EnvA) was selected as the standard antigen for a series of prototype HIV vaccines to compare various vaccine platforms. In addition, prior studies of rAd5-vectored vaccines suggested pre-existing human immunity may be a confounding factor in vaccine efficacy. rAd35 is less seroprevalent across human populations and was chosen for testing alone and in combination with a rAd5-EnvA vaccine in the present two-part phase I study.

METHODS

First, five subjects each received a single injection of 109, 1010, or 1011 particle units (PU) of rAd35-EnvA in an open-label, dose-escalation study. Next, 20 Ad5/Ad35-seronegative subjects were randomized to blinded, heterologous prime-boost schedules combining rAd5-EnvA and rAd35-EnvA with a three month interval. rAd35-EnvA was given at 1010 or 1011 PU to ten subjects each; all rAd5-EnvA injections were 1010 PU. EnvA-specific immunogenicity was assessed four weeks post-injection. Solicited reactogenicity and clinical safety were followed after each injection.

RESULTS

Vaccinations were well tolerated at all dosages. Antibody responses measured by ELISA were detected at 4 weeks in 30% and 50% of subjects after single doses of 1010 or 1011 PU rAd35, respectively, and in 89% after a single rAd5-EnvA 1010 PU injection. EnvA-specific IFN-γ ELISpot responses were detected at four weeks in 0%, 70%, and 50% of subjects after the respective rAd35-EnvA dosages compared to 89% of subjects after rAd5. T cell responses were higher after a single rAd5-EnvA 1010 PU injection than after a single rAd35-EnvA 1010 PU injection, and humoral responses were low after a single dose of either vector. Of those completing the vaccine schedule, 100% of rAd5-EnvA recipients and 90% of rAd35-EnvA recipients had both T cell and humoral responses after boosting with the heterologous vector. ELISpot response magnitude was similar in both regimens and comparable to a single dose of rAd5. A trend toward more robust CD8 T cell responses using rAd5-EnvA prime and rAd35-EnvA boost was observed. Humoral response magnitude was also similar after either heterologous regimen, but was several fold higher than after a single dose of rAd5. Adverse events (AEs) related to study vaccines were in general mild and limited to one episode of hematuria, Grade two. Activated partial thromboplastin time (aPTT) AEs were consistent with an in vitro effect on the laboratory assay for aPTT due to a transient induction of anti-phospholipid antibody, a phenomenon that has been reported in other adenoviral vector vaccine trials.

CONCLUSIONS

Limitations of the rAd vaccine vectors, including the complex interactions among pre-existing adenoviral immunity and vaccine-induced immune responses, have prompted investigators to include less seroprevalent vectors such as rAd35-EnvA in prime-boost regimens. The rAd35-EnvA vaccine described here was well tolerated and immunogenic. While it effectively primed and boosted antibody responses when given in a reciprocal prime-boost regimen with rAd5-EnvA using a three-month interval, it did not significantly improve the frequency or magnitude of T cell responses above a single dose of rAd5. The humoral and cellular immunogenicity data reported here may inform future vaccine and study design.

TRIAL REGISTRATION

ClinicalTrials.gov NCT00479999.

Influenza nucleoprotein DNA vaccination by a skin targeted, dry coated, densely packed microprojection array (Nanopatch) induces potent antibody and CD8(+) T cell responses

DNA vaccines have many advantages such as thermostability and the ease and rapidity of manufacture; for example, in an influenza pandemic situation where rapid production of vaccine is essential. However, immunogenicity of DNA vaccines was shown to be poor in humans unless large doses of DNA are used. If a highly efficacious DNA vaccine delivery system could be identified, then DNA vaccines have the potential to displace protein vaccines. In this study, we show in a C57BL/6 mouse model, that the Nanopatch, a microprojection array of high density (>21,000 projections/cm(2)), could be used to deliver influenza nucleoprotein DNA vaccine to skin, to generate enhanced antigen specific antibody and CD8(+) T cell responses compared to the conventional intramuscular (IM) delivery by the needle and syringe. Antigen specific antibody was measured using ELISA assays of mice vaccinated with a DNA plasmid containing the nucleoprotein gene of influenza type A/WSN/33 (H1N1). Antigen specific CD8(+) T cell responses were measured ex-vivo in splenocytes of mice using IFN-γ ELISPOT assays. These results and our previous antibody and CD4(+) T cell results using the Nanopatch delivered HSV DNA vaccine indicate that the Nanopatch is an effective delivery system of general utility that could potentially be used in humans to increase the potency of the DNA vaccines.

Using Plasmids as DNA Vaccines for Infectious Diseases

DNA plasmids can be used to induce a protective (or therapeutic) immune response by delivering genes encoding vaccine antigens. That naked DNA (without the refinement of coat proteins or host evasion systems) can cross from outside the cell into the nucleus and be expressed is particularly remarkable given the sophistication of the immune system in preventing infection by pathogens. As a result of the ease, low cost, and speed of custom gene synthesis, DNA vaccines dangle a tantalizing prospect of the next wave of vaccine technology, promising individual designer vaccines for cancer or mass vaccines with a rapid response time to emerging pandemics. There is considerable enthusiasm for the use of DNA vaccination as an approach, but this enthusiasm should be tempered by the successive failures in clinical trials to induce a potent immune response. The technology is evolving with the development of improved delivery systems that increase expression levels, particularly electroporation and the incorporation of genetically encoded adjuvants. This review will introduce some key concepts in the use of DNA plasmids as vaccines, including how the DNA enters the cell and is expressed, how it induces an immune response, and a summary of clinical trials with DNA vaccines. The review also explores the advances being made in vector design, delivery, formulation, and adjuvants to try to realize the promise of this technology for new vaccines. If the immunogenicity and expression barriers can be cracked, then DNA vaccines may offer a step change in mass vaccination.

Analysis of T cell responses to chimpanzee adenovirus vectors encoding HIV gag-pol-nef antigen

Adenoviruses have been shown to be both immunogenic and efficient at presenting HIV proteins but recent trials have suggested that they may play a role in increasing the risk of HIV acquisition. This risk may be associated with the presence of pre-existing immunity to the viral vectors. Chimpanzee adenoviruses (chAd) have low seroprevalence in human populations and so reduce this risk. ChAd3 and chAd63 were used to deliver an HIV gag, pol and nef transgene. ELISpot analysis of T cell responses in mice showed that both chAd vectors were able to induce an immune response to Gag and Pol peptides but that only the chAd3 vector induced responses to Nef peptides. Although the route of injection did not influence the magnitude of immune responses to either chAd vector, the dose of vector did. Taken together these results demonstrate that chimpanzee adenoviruses are suitable vector candidates for the delivery of HIV proteins and could be used for an HIV vaccine and furthermore the chAd3 vector produces a broader response to the HIV transgene.

Effect of vaccine administration modality on immunogenicity and efficacy

The many factors impacting the efficacy of a vaccine can be broadly divided into three categories: features of the vaccine itself, including immunogen design, vaccine type, formulation, adjuvant and dosing; individual variations among vaccine recipients and vaccine administration-related parameters. While much literature exists related to vaccines, and recently systems biology has started to dissect the impact of individual subject variation on vaccine efficacy, few studies have focused on the role of vaccine administration-related parameters on vaccine efficacy. Parenteral and mucosal vaccinations are traditional approaches for licensed vaccines; novel vaccine delivery approaches, including needless injection and adjuvant formulations, are being developed to further improve vaccine safety and efficacy. This review provides a brief summary of vaccine administration-related factors, including vaccination approach, delivery route and method of administration, to gain a better understanding of their potential impact on the safety and immunogenicity of candidate vaccines.

A Comparison of Red Fluorescent Proteins to Model DNA Vaccine Expression by Whole Animal In Vivo Imaging

DNA vaccines can be manufactured cheaply, easily and rapidly and have performed well in pre-clinical animal studies. However, clinical trials have so far been disappointing, failing to evoke a strong immune response, possibly due to poor antigen expression. To improve antigen expression, improved technology to monitor DNA vaccine transfection efficiency is required. In the current study, we compared plasmid encoded tdTomato, mCherry, Katushka, tdKatushka2 and luciferase as reporter proteins for whole animal in vivo imaging. The intramuscular, subcutaneous and tattooing routes were compared and electroporation was used to enhance expression. We observed that overall, fluorescent proteins were not a good tool to assess expression from DNA plasmids, with a highly heterogeneous response between animals. Of the proteins used, intramuscular delivery of DNA encoding either tdTomato or luciferase gave the clearest signal, with some Katushka and tdKatushka2 signal observed. Subcutaneous delivery was weakly visible and nothing was observed following DNA tattooing. DNA encoding haemagglutinin was used to determine whether immune responses mirrored visible expression levels. A protective immune response against H1N1 influenza was induced by all routes, even after a single dose of DNA, though qualitative differences were observed, with tattooing leading to high antibody responses and subcutaneous DNA leading to high CD8 responses. We conclude that of the reporter proteins used, expression from DNA plasmids can best be assessed using tdTomato or luciferase. But, the disconnect between visible expression level and immunogenicity suggests that in vivo whole animal imaging of fluorescent proteins has limited utility for predicting DNA vaccine efficacy.