Protective properties of vaccinia virus-based vaccines: skin scarification promotes a nonspecific immune response that protects against orthopoxvirus disease

A novel intradermal tattoo-based injection device enhances the immunogenicity of plasmid DNA vaccines

In recent years, tattooing technology has shown promising results toward evaluating vaccines in both animal models and humans. However, this technology has some limitations due to variability of experimental evaluations or operator procedures. The current study evaluated a device (intradermal oscillating needle array injection device: IONAID) capable of microinjecting a controlled dose of any aqueous vaccine into the intradermal space. IONAID-mediated administration of a DNA-based vaccine encoding the glycoprotein (GP) from the Ebola virus resulted in superior T- and B-cell responses with IONAID when compared to single intramuscular (IM) or intradermal (ID) injection in mice. Moreover, humoral immune responses, induced after IONAID vaccination, were significantly higher to those obtained with traditional passive DNA tattooing in guinea pigs and rabbits. This device was well tolerated and safe during HIV vaccine delivery in non-human primates (NHPs), while inducing robust immune responses. In summary, this study shows that the IONAID device improves vaccine performance, which could be beneficial to the animal and human health, and importantly, provide a dose-sparing approach (e.g., monkeypox vaccine).

Pattern Recognition Receptors of Nucleic Acids Can Cause Sublethal Activation of the Mitochondrial Apoptosis Pathway during Viral Infection

The mitochondrial apoptosis pathway has the function to kill the cell, but recent work shows that this pathway can also be activated to a sublethal level, where signal transduction can be observed but the cell survives. Intriguingly, this signaling has been shown to contribute to inflammatory activity of epithelial cells upon infection with numerous agents. This suggests that microbial recognition can generate sublethal activity in the mitochondrial apoptosis pathway. Because this recognition is achieved by pattern recognition receptors (PRRs), it also implies that PRR signals are linked to the mitochondrial apoptosis apparatus. We here test this hypothesis during infection of epithelial cells with modified vaccinia virus Ankara (MVA). MVA recognition is achieved through receptors specific for nucleic acids, and we present evidence that the three receptors, Toll-like receptor 3 (TLR3), RIG-I/MDA5, and cyclic GMP-AMP synthase (cGAS)/stimulator of interferon genes (STING), are involved in this signaling. When stimulated directly by specific ligands, all three receptors could trigger sublethal apoptosis signals. During infection with MVA, sublethal apoptosis signals were unmasked in X-linked IAP (XIAP)-deficient cells, where apoptosis induction was observed. Deletion of any of the three signaling adapters, TRIF, MAVS, and STING, reduced the DNA damage response, a sensitive measure of sublethal apoptosis signals. Our results suggest that PRRs signal via mitochondria, where they generate sublethal signals through the BCL-2-family, which may contribute to the response to infectious agents. IMPORTANCE A contribution of the mitochondrial apoptosis apparatus, in the absence of cell death, to the reaction of nonprofessional immune cells to viruses is suggested to play a role as a broad alert system of an infected cell: the apoptosis system can be activated by many upstream signals and could therefore act as a central coordinator of viral recognition. The proapoptotic activity of PRRs has been documented in multiple situations, but this activity seems too low to be meaningful, and a physiological significance of such activity is not immediately obvious. This work suggests the alternative interpretation that PRRs do not have the primary function to induce apoptosis but to trigger sublethal signals in the apoptosis system. A number of lines of recent research suggest that mitochondria contribute to cellular reactions, and this pathway may be a way of triggering an early host response.

Two DNA vaccines protect against severe disease and pathology due to SARS-CoV-2 in Syrian hamsters

The SARS-CoV-2 pandemic is an ongoing threat to global health, and wide-scale vaccination is an efficient method to reduce morbidity and mortality. We designed and evaluated two DNA plasmid vaccines, based on the pIDV-II system, expressing the SARS-CoV-2 spike gene, with or without an immunogenic peptide, in mice, and in a Syrian hamster model of infection. Both vaccines demonstrated robust immunogenicity in BALB/c and C57BL/6 mice. Additionally, the shedding of infectious virus and the viral burden in the lungs was reduced in immunized hamsters. Moreover, high-titers of neutralizing antibodies with activity against multiple SARS-CoV-2 variants were generated in immunized animals. Vaccination also protected animals from weight loss during infection. Additionally, both vaccines were effective at reducing both pulmonary and extrapulmonary pathology in vaccinated animals. These data show the potential of a DNA vaccine for SARS-CoV-2 and suggest further investigation in large animal and human studies could be pursued.

Low-Temperature Multiple Micro-Dispensing on Microneedles for Accurate Transcutaneous Smallpox Vaccination

Smallpox is an acute contagious disease caused by the variola virus. According to WHO guidelines, the smallpox vaccine is administrated by scarification into the epidermis using a bifurcated needle moistened with a vaccine solution. However, this invasive vaccination method involving multiple skin punctures requires a special technique to inoculate, as well as a cold chain for storage and distribution of vaccine solutions containing a live virus. Here, we report a transcutaneous smallpox vaccination using a live vaccinia-coated microneedle (MN) patch prepared by a low-temperature multiple nanoliter-level dispensing system, enabling accurate transdermal delivery of live vaccines and maintenance of bioactivity. The live vaccinia in hyaluronic acid (HA) solutions was selectively coated on the solid MN tips, and the coating amount of the vaccine was precisely controlled through a programmed multiple dispensing process with high accuracy under low temperature conditions (2–8 °C) for smallpox vaccination. Inoculation of mice (BALB/C mouse) with the MN patch coated with the second-generation smallpox vaccine increased the neutralizing antibody titer and T cell immune response. Interestingly, the live vaccine-coated MN patch maintained viral titers at −20 °C for 4 weeks and elevated temperature (37 °C) for 1 week, highlighting improved storage stability of the live virus formulated into coated MN patches. This coated MN platform using contact dispensing technique provides a simple and effective method for smallpox vaccination.

Imaging viral infection in vivo to gain unique perspectives on cellular antiviral immunity

The past decade has seen near continual global public health crises caused by emerging viral infections. Extraordinary increases in our knowledge of the mechanisms underlying successful antiviral immune responses in animal models and during human infection have accompanied these viral outbreaks. Keeping pace with the rapidly advancing field of viral immunology, innovations in microscopy have afforded a previously unseen view of viral infection occurring in real-time in living animals. Here, we review the contribution of intravital imaging to our understanding of cell-mediated immune responses to viral infections, with a particular focus on studies that visualize the antiviral effector cells responding to infection as well as virus-infected cells. We discuss methods to visualize viral infection in vivo using intravital microscopy (IVM) and significant findings arising through the application of IVM to viral infection. Collectively, these works underscore the importance of developing a comprehensive spatial understanding of the relationships between immune effectors and virus-infected cells and how this has enabled unique discoveries about virus/host interactions and antiviral effector cell biology.

Skin Viral Infections: Host Antiviral Innate Immunity and Viral Immune Evasion

The skin is an active immune organ that functions as the first and largest site of defense to the outside environment. Serving as the primary interface between host and pathogen, the skin’s early immune responses to viral invaders often determine the course and severity of infection. We review the current literature pertaining to the mechanisms of cutaneous viral invasion for classical skin-tropic, oncogenic, and vector-borne skin viruses. We discuss the skin’s evolved mechanisms for innate immune viral defense against these invading pathogens, as well as unique strategies utilized by the viruses to escape immune detection. We additionally explore the roles that demographic and environmental factors, such as age, biological sex, and the cutaneous microbiome, play in altering the host immune response to viral threats.

Recombinant Myxoma Virus Expressing Walleye Dermal Sarcoma Virus orfC Is Attenuated in Rabbits

The poxvirus, myxoma virus (MYXV) has shown efficacy as an oncolytic virus (OV) in some cancer models. However, MYXV replication within murine cancer models and spontaneous canine sarcomas is short-lived. In mice, successful treatment of tumors requires frequent injections with MYXV. We hypothesize that treatment of cancer with a recombinant MYXV that promotes apoptosis could improve the efficacy of MYXV. The orfC gene of walleye dermal sarcoma virus (WDSV), which induces apoptosis, was recombined into the MYXV genome (MYXVorfC). A marked increase in apoptosis was observed in cells infected with MYXVorfC. To ensure that expression of WDSV orfC by MYXV does not potentiate the pathogenesis of MYXV, we evaluated the effects of MYXVorfC inoculation in the only known host of MYXV, New Zealand white rabbits. Virus dissemination in rabbit tissues was similar for MYXVorfC and MYXV. Virus titers recovered from tissues were lower in MYXVorfC-infected rabbits as compared to MYXV-infected rabbits. Importantly, rabbits infected with MYXVorfC had a delayed onset of clinical signs and a longer median survival time than rabbits infected with MYXV. This study indicates that MYXVorfC is attenuated and suggests that MYXVorfC will be safe to use as an OV therapy in future studies.

Phase-out of smallpox vaccination and the female/male HIV-1 prevalence ratio: an ecological study from Guinea-Bissau

OBJECTIVE

In Guinea-Bissau, West Africa, we observed that having a smallpox vaccination scar was associated with lower HIV-1 prevalence, more strongly for women than men. If this represents a causal effect, the female/male HIV-1 prevalence ratio would increase for birth cohorts no longer receiving smallpox vaccination due to the phase-out of this vaccine.

DESIGN

An ecological design using HIV surveys and information about smallpox vaccination coverage.

SETTING

Urban and rural Guinea-Bissau.

PARTICIPANTS

Participants in HIV surveys were grouped into an age group with decreasing smallpox vaccination coverage (15-34 years) and an age group with steady smallpox vaccination coverage (≥35 years).

INTERVENTIONS

The exposure of interest was the phase-out of the smallpox vaccine in Guinea-Bissau.

PRIMARY AND SECONDARY OUTCOME MEASURES

HIV-1 prevalence.

RESULTS

At both sites, the female/male HIV-1 prevalence ratio increased by calendar time for the age group with decreasing smallpox vaccination coverage; the combined female/male HIV-1 prevalence ratio among people aged 15-34 years was 1.00 (95% CI 0.17 to 5.99) in 1987-1990, 1.16 (95% CI 0.69 to 1.93) in 1996-1997, 2.32 (95% CI 1.51 to 3.56) in 2006-2007 (p value for no trend=0.04). There was no increase in the female-to-male HIV-1 prevalence ratio for the age group >35 years with steady smallpox vaccination coverage; 1.93 (95% CI 0.40 to 9.25) in 1987-1990, 1.32 (95% CI 0.83 to 2.10) in 1996-1997, 0.81 (95% CI 0.56 to 1.16) in 2006-2007 (p value for no trend=0.07).

CONCLUSIONS

Thus, data was compatible with the deduction that the phase-out of smallpox vaccination may have increased the susceptibility to HIV-1 relatively more for women than men. Hence, phasing out smallpox vaccination may have contributed to the global increase in the female/male HIV-1 prevalence ratio among young individuals. Due to the potential fallacies of ecological studies, the results should be interpreted carefully, and this hypothesis needs further assessment. If the hypothesis is true, studies of smallpox vaccination could inform HIV-1 vaccine research.

Cellular metabolism and pore lifetime of human skin following microprojection array mediation

Skin-targeting microscale medical devices are becoming popular for therapeutic delivery and diagnosis. We used cryo-SEM, fluorescence lifetime imaging microscopy (FLIM), autofluorescence imaging microscopy and inflammatory response to study the puncturing and recovery of human skin ex vivo and in vivo after discretised puncturing by a microneedle array (Nanopatch®). Pores induced by the microprojections were found to close by ~25% in diameter within the first 30 min, and almost completely close by ~6 h. FLIM images of ex vivo viable epidermis showed a stable fluorescence lifetime for unpatched areas of ~1000 ps up to 24 h. Only the cells in the immediate puncture zones (in direct contact with projections) showed a reduction in the observed fluorescence lifetimes to between ~518-583 ps. The ratio of free-bound NAD(P)H (α1/α2) in unaffected areas of the viable epidermis was ~2.5-3.0, whereas the ratio at puncture holes was almost double at ~4.2-4.6. An exploratory pilot in vivo study also suggested similar closure rate with histamine administration to the forearms of human volunteers after Nanopatch® treatment, although a prolonged inflammation was observed with Tissue Viability Imaging. Overall, this work shows that the pores created by the microneedle-type medical device, Nanopatch®, are transient, with the skin recovering rapidly within 1-2 days in the epidermis after application.

Time to Micromanage the Pathogen-Host-Vector Interface: Considerations for Vaccine Development

The current increase in vector-borne disease worldwide necessitates novel approaches to vaccine development targeted to pathogens delivered by blood-feeding arthropod vectors into the host skin. A concept that is gaining traction in recent years is the contribution of the vector or vector-derived components, like salivary proteins, to host-pathogen interactions. Indeed, the triad of vector-host-pathogen interactions in the skin microenvironment can influence host innate and adaptive responses alike, providing an advantage to the pathogen to establish infection. A better understanding of this "bite site" microenvironment, along with how host and vector local microbiomes immunomodulate responses to pathogens, is required for future vaccines for vector-borne diseases. Microneedle administration of such vaccines may more closely mimic vector deposition of pathogen and saliva into the skin with the added benefit of near painless vaccine delivery. Focusing on the 'micro'⁻from microenvironments to microbiomes to microneedles⁻may yield an improved generation of vector-borne disease vaccines in today's increasingly complex world.

Epithelial boost enhances antigen expression by vaccinia virus for the generation of potent CD8+ T cell-mediated antitumor immunity following DNA priming vaccination

While both pNGVL4a-Sig/E7(detox)/HSP70 DNA vaccine and TA-HPV recombinant vaccinia viral vector-based vaccines have elicited HPV-specific CD8+ T cell responses in HPV16/E7-expressing tumor models, and been used as prime-boost regimen to enhance HPV-specific immune responses in humans (NCT00788164), the optimal route of administration for TA-HPV remains unclear. In a preclinical model, we examined the immunogenicity of priming with intramuscular pNGVL4a-Sig/E7(detox)/HSP70 followed by TA-HPV boost through different administration routes. We observed that priming twice with a pNGVL4a-Sig/E7(detox)/HSP70 followed by a single TA-HPV immunization boost through skin scarification generated the strongest antigen-specific CD8+ T cell response in C57BL/6 mice. These data translate to tumor control and prolonged survival of treated mice. Our results provide rationale for future clinical testing of intramuscular pNGVL4a-Sig/E7(detox)/HSP70 DNA vaccine prime, TA-HPV vaccine skin scarification boost immunization regimen for the control of HPV-associated diseases.

Development of potent class II transactivator gene delivery systems capable of inducing de novo MHC II expression in human cells, in vitro and ex vivo

Class II transactivator (CIITA) induces transcription of major histocompatibility complex (MHC) II genes and can potentially be used to improve genetic immunotherapies by converting non-immune cells into cells capable of presenting antigens to CD4⁺ T cells. However, CIITA expression is tightly controlled and it remains unclear whether distinct non-immune cells differ in this transactivator regulation. Here we describe the development of gene delivery systems capable of promoting the efficient CIITA expression in non-immune cell lines and in primary human cells of an ex vivo skin explant model. Different human cell types undergoing CIITA overexpression presented high-level de novo expression of MHC II, validating the delivery systems as suitable tools for the CIITA evaluation as a molecular adjuvant for gene therapies.

Percutaneous Vaccination as an Effective Method of Delivery of MVA and MVA-Vectored Vaccines

The robustness of immune responses to an antigen could be dictated by the route of vaccine inoculation. Traditional smallpox vaccines, essentially vaccinia virus strains, that were used in the eradication of smallpox were administered by percutaneous inoculation (skin scarification). The modified vaccinia virus Ankara is licensed as a smallpox vaccine in Europe and Canada and currently undergoing clinical development in the United States. MVA is also being investigated as a vector for the delivery of heterologous genes for prophylactic or therapeutic immunization. Since MVA is replication-deficient, MVA and MVA-vectored vaccines are often inoculated through the intramuscular, intradermal or subcutaneous routes. Vaccine inoculation via the intramuscular, intradermal or subcutaneous routes requires the use of injection needles, and an estimated 10 to 20% of the population of the United States has needle phobia. Following an observation in our laboratory that a replication-deficient recombinant vaccinia virus derived from the New York City Board of Health strain elicited protective immune responses in a mouse model upon inoculation by tail scarification, we investigated whether MVA and MVA recombinants can elicit protective responses following percutaneous administration in mouse models. Our data suggest that MVA administered by percutaneous inoculation, elicited vaccinia-specific antibody responses, and protected mice from lethal vaccinia virus challenge, at levels comparable to or better than subcutaneous or intramuscular inoculation. High titers of specific neutralizing antibodies were elicited in mice inoculated with a recombinant MVA expressing the herpes simplex type 2 glycoprotein D after scarification. Similarly, a recombinant MVA expressing the hemagglutinin of attenuated influenza virus rgA/Viet Nam/1203/2004 (H5N1) elicited protective immune responses when administered at low doses by scarification. Taken together, our data suggest that MVA and MVA-vectored vaccines inoculated by scarification can elicit protective immune responses that are comparable to subcutaneous vaccination, and may allow for antigen sparing when vaccine supply is limited.