Codelivery of the chemokine CCL3 by an adenovirus-based vaccine improves protection from retrovirus infection

Early spatiotemporal evolution of the immune response elicited by adenovirus serotype 26 vector vaccination in mice

As the first responder to immunological challenges, the innate immune system shapes and regulates the ensuing adaptive immune response. Many clinical studies evaluating the role of innate immunity in initiating vaccine-elicited adaptive immune responses have largely been confined to blood due to the inherent difficulty in acquiring tissue samples. However, the absence of vaccine-site and draining lymph node information limits the understanding of early events induced by vaccination that could potentially shape vaccine-elicited immunity. We, therefore, utilized a mouse model to investigate the spatiotemporal evolution of the immune response within the first 24 hours following intramuscular adenovirus serotype 26 (Ad26) vector vaccination in tissues. We show that the Ad26 vaccine-elicited innate immune response commences by 1 hour and rapidly evolves in tissues and blood within the first 24 hours, as reflected by the detection of cytokines, chemokines, cellular responses, and transcriptomic pathways. Furthermore, serum levels of IL-6, MIG, MIP-1α, MIP-1β, and TNF-α at 6 hours post-vaccination correlated with the frequency of vaccine-elicited memory CD8+ T cell responses evaluated at 60 days post-vaccination in blood and tissues. Taken together, our data suggest that the immune response to Ad26 vector vaccination commences quickly in tissues by 1 hour and that events by as early as 6 hours post-vaccination can shape vaccine-elicited CD8+ T cell responses at later memory time points.IMPORTANCEPrior studies have largely concentrated on innate immune activation in peripheral blood following vaccination. In this study, we report the detailed spatial and temporal innate immune activation in tissues following Ad26 vaccination in mice. We observed rapid innate activation not only in peripheral blood but also in draining lymph nodes and at the site of inoculation. Our findings provide a more detailed picture of the host response to vaccination than previously reported.

Early spatiotemporal evolution of the immune response elicited by adenovirus serotype 26 vector vaccination in mice

As the first responder to immunological challenges, the innate immune system shapes and regulates the ensuing adaptive immune response. Many clinical studies evaluating the role of innate immunity in initiating vaccine-elicited adaptive immune responses have largely been confined to blood due to inherent difficulty in acquiring tissue samples. However, the absence of vaccine-site and draining lymph node information limits understanding of early events induced by vaccination that could potentially shape vaccine-elicited immunity. We therefore utilized a mouse model to investigate the spatiotemporal evolution of the immune response within the first 24 hours following intramuscular adenovirus serotype 26 (Ad26) vector vaccination in tissues. We show that the Ad26 vaccine-elicited innate immune response commences by one hour and rapidly evolves in tissues and blood within the first 24 hours as reflected by the detection of cytokines, chemokines, cellular responses, and transcriptomic pathways. Furthermore, serum levels of IL-6, MIG, MIP-1α, and MIP-1β at 6 hours post-vaccination correlated with the frequency of vaccine-elicited memory CD8+ T cell responses evaluated at 60 days post-vaccination in blood and tissues. Taken together, our data suggests that the immune response to Ad26 vector vaccination commences quickly in tissues by one hour and that events by as early as 6 hours post-vaccination can shape vaccine-elicited CD8+ T cell responses at later memory time points.

Comparative Evaluation of the Vaccine Efficacies of Three Adenovirus-Based Vector Types in the Friend Retrovirus Infection Model

Adenovirus (AdV)-based vectors are popular experimental vaccine vectors, but despite their ability to induce strong immune responses, their application is impeded by widespread preexisting immunity against many AdV types that can impair or even abrogate the induction of transgene-specific immune responses. Therefore, the development of vectors based on AdV types with a low seroprevalence is important for effective AdV-based immunization in humans. We investigated the immunization efficacy of vectors based on AdV type 48 (Ad48) and Ad50 in the ovalbumin (ova) model as well as the Friend retrovirus (FV) model, which allows testing of the protective effect of vaccine-induced immunity. Using ova-encoding vectors, we found a significantly lower induction of ova-specific CD8⁺ T cells and antibody responses by Ad48- and Ad50-based vectors than by Ad5-based vectors. Similarly, we found a reduced induction of FV-specific CD8⁺ T cell responses in Ad48- and Ad50.Leader-Gag-immunized mice compared with that in Ad5-immunized mice; however, some of those mice were able to control the FV infection, and protection correlated with the level of neutralizing antibodies 10 days after FV challenge. Analyses of the AdV-specific antibodies and CD8⁺ T cells induced by the individual AdV types revealed a high level of cross-reactivity, and the efficacy of Ad48-based immunization was impaired in Ad5-preimmune mice. Our results show that the immunity induced by Ad48- and Ad50-based vectors is reduced compared to that induced by Ad5 and is sufficient to control FV infection in only some of the immunized mice. A high level of cross-reactivity suggests that AdV preimmunity must be considered even when applying rare AdV-based vectors.IMPORTANCE AdV-based vectors are important tools for the development of vaccines against a wide range of pathogens. While AdV vectors are generally considered safe and highly effective, their application can be severely impaired by preexisting immunity due to the widespread seroprevalence of some AdV types. The characterization of different AdV types with regard to immunogenicity and efficacy in challenge models is of great importance for the development of improved AdV-based vectors that allow for efficient immunization despite anti-AdV immunity. We show that the immunity induced by an Ad48-based vector is inferior to that induced by an Ad5-based vector but can still mediate the control of an FV infection in highly FV-susceptible mice. However, the efficacy of Ad48-based immunization was impaired in Ad5-preimmune mice. Importantly, we found cross-reactivity of both the humoral and cellular immune responses raised by the individual AdV types, suggesting that switching to a different AdV type may not be sufficient to circumvent preexisting anti-AdV immunity.

Immunization with a murine cytomegalovirus based vector encoding retrovirus envelope confers strong protection from Friend retrovirus challenge infection

Immunization vectors based on cytomegalovirus (CMV) have attracted a lot of interest in recent years because of their high efficacy in the simian immunodeficiency virus (SIV) macaque model, which has been attributed to their ability to induce strong, unusually broad, and unconventionally restricted CD8⁺ T cell responses. To evaluate the ability of CMV-based vectors to mediate protection by other immune mechanisms, we evaluated a mouse CMV (MCMV)-based vector encoding Friend virus (FV) envelope (Env), which lacks any known CD8⁺ T cell epitopes, for its protective efficacy in the FV mouse model. When we immunized highly FV-susceptible mice with the Env-encoding MCMV vector (MCMV.env), we could detect high frequencies of Env-specific CD4⁺ T cells after a single immunization. While the control of an early FV challenge infection was highly variable, an FV infection applied later after immunization was tightly controlled by almost all immunized mice. Protection of mice correlated with their ability to mount a robust anamnestic neutralizing antibody response upon FV infection, but Env-specific CD4⁺ T cells also produced appreciable levels of interferon γ. Depletion and transfer experiments underlined the important role of antibodies for control of FV infection but also showed that while no Env-specific CD8⁺ T cells were induced by the MCMV.env vaccine, the presence of CD8⁺ T cells at the time of FV challenge was required. The immunity induced by MCMV.env immunization was long-lasting, but was restricted to MCMV naïve animals. Taken together, our results demonstrate a novel mode of action of a CMV-based vaccine for anti-retrovirus immunization that confers strong protection from retrovirus challenge, which is conferred by CD4⁺ T cells and antibodies.

CMV-based vectors have attracted a lot of attention in the vaccine development field, since they were shown to induce unconventionally restricted CD8⁺ T cell responses and strong protection in the SIV rhesus macaque model. In a mouse retrovirus model, we show now that immunization with a mouse CMV-based vector encoding retrovirus envelope conferred very strong protection, even though it was not designed to induce any CD8⁺ T cell responses. In this MCMV.env immunization, protection relied on the induction of CD4⁺ T cells and the ability to mount a strong anamnestic neutralizing antibody response upon retrovirus infection, but it was restricted to MCMV pre-naïve mice. In our model system, the MCMV based vector shows very high efficacy that is comparable to an attenuated retrovirus-based vaccine, and encourages the pursuit of this vaccination strategy.

Interference of retroviral envelope with vaccine-induced CD8+ T cell responses is relieved by co-administration of cytokine-encoding vectors

Background

Retroviral envelope (Env) proteins are known to exhibit immunosuppressive properties, which become apparent not only in retroviral infections, but also in gene-based immunizations using retroviral immunogens, where envelope interferes with the induction of CD8⁺ T cell responses towards another, simultaneously or subsequently delivered, immunogen.

Results

In the Friend retrovirus mouse model, immunization with a plasmid encoding the Friend murine leukemia virus (F-MuLV) Leader-Gag protein resulted in induction of a strong GagL_85–93-specific CD8⁺ T cell response, while the response was completely abrogated by co-immunization with an F-MuLV Env-encoding plasmid. In order to overcome this interference of retroviral envelope, we employed plasmids encoding the cytokines interleukin (IL) 1β, IL2, IL12, IL15, IL21, IL28A or granulocyte–macrophage colony-stimulating factor (GM-CSF) as genetic adjuvants. Co-application of plasmids encoding IL2, IL12, IL21, IL28A and especially GM-CSF rescued the induction of GagL_85–93-specific CD8⁺ T cells in mice vaccinated with FV Leader-Gag and Env. Mice that were immunized with plasmids encoding Leader-Gag and Env and the cytokines IL1β, IL12, IL15, IL28A or GM-CSF, but not Leader-Gag and Env without any cytokine, showed significantly reduced viral loads upon a high-dose Friend virus challenge infection.

Conclusions

Our data demonstrate the potency of cytokine-encoding vectors as adjuvants and immune modulators in composite vaccines for anti-retroviral immunization.

Electronic supplementary material

The online version of this article (doi:10.1186/s12977-017-0352-7) contains supplementary material, which is available to authorized users.

Induction of complex immune responses and strong protection against retrovirus challenge by adenovirus-based immunization depends on the order of vaccine delivery

Background

In the Friend retrovirus mouse model we developed potent adenovirus-based vaccines that were designed to induce either strong Friend virus GagL_85–93-specific CD8⁺ T cell or antibody responses, respectively. To optimize the immunization outcome we evaluated vaccination strategies using combinations of these vaccines.

Results

While the vaccines on their own confer strong protection from a subsequent Friend virus challenge, the simple combination of the vaccines for the establishment of an optimized immunization protocol did not result in a further improvement of vaccine effectivity. We demonstrate that the co-immunization with GagL_85–93/leader-gag encoding vectors together with envelope-encoding vectors abrogates the induction of GagL_85–93-specific CD8⁺ T cells, and in successive immunization protocols the immunization with the GagL_85–93/leader-gag encoding vector had to precede the immunization with an envelope encoding vector for the efficient induction of GagL_85–93-specific CD8⁺ T cells. Importantly, the antibody response to envelope was in fact enhanced when the mice were adenovirus-experienced from a prior immunization, highlighting the expedience of this approach.

Conclusions

To circumvent the immunosuppressive effect of envelope on immune responses to simultaneously or subsequently administered immunogens, we developed a two immunizations-based vaccination protocol that induces strong immune responses and confers robust protection of highly Friend virus-susceptible mice from a lethal Friend virus challenge.

Electronic supplementary material

The online version of this article (doi:10.1186/s12977-017-0336-7) contains supplementary material, which is available to authorized users.

Bovine adenovirus-3 as a vaccine delivery vehicle

The use of vaccines is an effective and relatively inexpensive means of controlling infectious diseases, which cause heavy economic losses to the livestock industry through animal loss, decreased productivity, treatment expenses and decreased carcass quality. However, some vaccines produced by conventional means are imperfect in many respects including virulence, safety and efficacy. Moreover, there are no vaccines for some animal diseases. Although genetic engineering has provided new ways of producing effective vaccines, the cost of production for veterinary use is a critical criterion for selecting the method of production and delivery of vaccines. The cost effective production and intrinsic ability to enter cells has made adenovirus vectors a highly efficient tool for delivery of vaccine antigens. Moreover, adenoviruses induce both humoral and cellular immune responses to expressed vaccine antigens. Since nonhuman adenoviruses are species specific, the development of animal specific adenoviruses as vaccine delivery vectors is being evaluated. This review summarizes the work related to the development of bovine adenovirus-3 as a vaccine delivery vehicle in animals, particularly cattle.

The influence of delivery vectors on HIV vaccine efficacy

Development of an effective HIV/AIDS vaccine remains a big challenge, largely due to the enormous HIV diversity which propels immune escape. Thus novel vaccine strategies are targeting multiple variants of conserved antibody and T cell epitopic regions which would incur a huge fitness cost to the virus in the event of mutational escape. Besides immunogen design, the delivery modality is critical for vaccine potency and efficacy, and should be carefully selected in order to not only maximize transgene expression, but to also enhance the immuno-stimulatory potential to activate innate and adaptive immune systems. To date, five HIV vaccine candidates have been evaluated for efficacy and protection from acquisition was only achieved in a small proportion of vaccinees in the RV144 study which used a canarypox vector for delivery. Conversely, in the STEP study (HVTN 502) where human adenovirus serotype 5 (Ad5) was used, strong immune responses were induced but vaccination was more associated with increased risk of HIV acquisition than protection in vaccinees with pre-existing Ad5 immunity. The possibility that pre-existing immunity to a highly promising delivery vector may alter the natural course of HIV to increase acquisition risk is quite worrisome and a huge setback for HIV vaccine development. Thus, HIV vaccine development efforts are now geared toward delivery platforms which attain superior immunogenicity while concurrently limiting potential catastrophic effects likely to arise from pre-existing immunity or vector-related immuno-modulation. However, it still remains unclear whether it is poor immunogenicity of HIV antigens or substandard immunological potency of the safer delivery vectors that has limited the success of HIV vaccines. This article discusses some of the promising delivery vectors to be harnessed for improved HIV vaccine efficacy.

Induction of Potent and Long-Lived Antibody and Cellular Immune Responses in the Genitorectal Mucosa Could be the Critical Determinant of HIV Vaccine Efficacy

The field of HIV prevention has indeed progressed in leaps and bounds, but with major limitations of the current prevention and treatment options, the world remains desperate for an HIV vaccine. Sadly, this continues to be elusive, because more than 30 years since its discovery there is no licensed HIV vaccine. Research aiming to define immunological biomarkers to accurately predict vaccine efficacy have focused mainly on systemic immune responses, and as such, studies defining correlates of protection in the genitorectal mucosa, the primary target site for HIV entry and seeding are sparse. Clearly, difficulties in sampling and analysis of mucosal specimens, as well as their limited size have been a major deterrent in characterizing the type (mucosal antibodies, cytokines, chemokines, or CTL), threshold (magnitude, depth, and breadth) and viral inhibitory capacity of HIV-1-specific immune responses in the genitorectal mucosa, where they are needed to immediately block HIV acquisition and arrest subsequent virus dissemination. Nevertheless, a few studies document the existence of HIV-specific immune responses in the genitorectal mucosa of HIV-infected aviremic and viremic controllers, as well as in highly exposed persistently seronegative (HEPS) individuals with natural resistance to HIV-1. Some of these responses strongly correlate with protection from HIV acquisition and/or disease progression, thus providing significant clues of the ideal components of an efficacious HIV vaccine. In this study, we provide an overview of the key features of protective immune responses found in HEPS, elite and viremic controllers, and discuss how these can be achieved through mucosal immunization. Inevitably, HIV vaccine development research will have to consider strategies that elicit potent antibody and cellular immune responses within the genitorectal mucosa or induction of systemic immune cells with an inherent potential to home and persist at mucosal sites of HIV entry.

Pseudo-mannosylated DC-SIGN ligands as potential adjuvants for HIV vaccines

The development of new and effective adjuvants may play a fundamental role in improving HIV vaccine efficacy. New classes of vaccine adjuvants activate innate immunity receptors, notably toll like receptors (TLRs). Adjuvants targeting the C-Type lectin receptor DC-SIGN may be alternative or complementary to adjuvants based on TRL activation. Herein we evaluate the ability of the glycomimetic DC-SIGN ligand Polyman 19 (PM 19) to modulate innate immune responses. Results showed that PM 19 alone, or in combination with TLR agonists, induces the expression of cytokines, β chemokines and co-stimulatory molecules that may, in turn, modulate adaptive immunity and exert anti-viral effects. These results indicate that the suitability of this compound as a vaccine adjuvant should be further evaluated.

Interleukin-encoding adenoviral vectors as genetic adjuvant for vaccination against retroviral infection

Interleukins (IL) are cytokines with stimulatory and modulatory functions in the immune system. In this study, we have chosen interleukins which are involved in the enhancement of T_H2 responses and B cell functions to analyze their potential to improve a prophylactic adenovirus-based anti-retroviral vaccine with regard to antibody and virus-specific CD4⁺ T cell responses. Mice were vaccinated with an adenoviral vector which encodes and displays the Friend Virus (FV) surface envelope protein gp70 (Ad.pIXgp70) in combination with adenoviral vectors encoding the interleukins IL4, IL5, IL6, IL7 or IL23. Co-application of Ad.pIXgp70 with Ad.IL5, Ad.IL6 or Ad.IL23 resulted in improved protection with high control over FV-induced splenomegaly and reduced viral loads. Mice co-immunized with adenoviral vectors encoding IL5 or IL23 showed increased neutralizing antibody responses while mice co-immunized with Ad.IL6 or Ad.IL23 showed improved FV-specific CD4⁺ T cell responses compared to mice immunized with Ad.pIXgp70 alone. We show that the co-application of adenoviral vectors encoding specific interleukins is suitable to improve the vaccination efficacy of an anti-retroviral vaccine. Improved protection correlated with improved CD4⁺ T cell responses and especially with higher neutralizing antibody titers. The co-application of selected interleukin-encoding adenoviral vectors is a valuable tool for vaccination with regard to enhancement of antibody mediated immunity.

Beta-defensin 2 enhances immunogenicity and protection of an adenovirus-based H5N1 influenza vaccine at an early time

Reports of human infections with highly pathogenic H5N1 avian influenza viruses in many countries in Asia and Africa with varying case fatality rates highlight the pandemic potential of these viruses. In order to contain a rapidly spreading influenza virus in a pandemic scenario, a vaccine which can induce rapid and robust immune responses, preferably in a single dose, is necessary. Murine beta-defensin 2 (Mbd2), a small molecular weight protein expressed by epithelial cells, has been shown to enhance antigen-specific immune responses by recruiting and activating professional antigen presenting cells to the site of vaccination. This study assessed the potential of Mbd2 to enhance the immunogenicity and protective efficacy of a human adenovirus (HAd)-based vaccine expressing the hemagglutinin (HA) and nucleoprotein (NP) [HAd-HA-NP] of an H5N1 influenza virus. A single inoculation of mice with both HAd-HA-NP and a HAd vector expressing Murine β-defensin 2 (HAd-Mbd2) resulted in significantly higher levels of both humoral and cell-mediated immune responses compared to the groups vaccinated only with HAd-HA-NP. These responses were evident even at day 7 post-immunization. Furthermore, the HAd-HA-NP+HAd-Mbd2-immunized group receiving the lowest vector dose (2 × 10(7)+1 × 10(7)) was completely protected against an rgH5N1 virus challenge on day 7 post-vaccination. These results highlight the potential of Mbd2 as a genetic adjuvant in inducing rapid and robust immune responses to a HAd-based vaccine.

Adenoviral vector expressing murine β-defensin 2 enhances immunogenicity of an adenoviral vector based H5N1 influenza vaccine in aged mice

The ability to resist infections and respond to vaccinations is greatly reduced in the older adult population owing to a general decline in innate and adaptive immune functions with aging. Over the years several strategies such as increasing the vaccine dose, number of immunizations and using adjuvants have been evaluated to improve the immunogenicity and efficacy of vaccines in the older adult population. Murine β-defensin 2 (Mbd2) has been shown to function as a molecular adjuvant by recruiting and activating immature dendritic cells (DCs), professional antigen-presenting cells (APC), to the site of the immunization. In this study, we evaluated the potential utility of Mbd2 to enhance the efficacy of an adenoviral vector-based H5N1 influenza vaccine expressing hemagglutinin (HA) and nucleoprotein (NP) (HAd-HA-NP) in an aged mouse model. Our results indicated that immunostimulation with an adenoviral vector expressing Mbd2 (HAd-Mbd2) activated DCs and significantly enhanced the humoral and cellular immune responses induced by HAd-HA-NP. Furthermore, immunostimulation with HAd-Mbd2 followed by immunization with HAd-HA-NP resulted in significantly lower virus titers in the lungs following challenge with a H5N1 influenza virus compared to the group immunized with HAd-HA-NP without immunostimulation. Overall, our results highlight the potential utility of Mbd2 as a molecular adjuvant to enhance the immunogenicity and protective efficacy of vaccines for the elderly.

Chemokine-based immunotherapy: delivery systems and combination therapies

A major role of chemokines is to mediate leukocyte migration through interaction with G-protein-coupled receptors. Various delivery systems have been developed to utilize the chemokine properties for combating disease. Viral and mutant viral vectors expressing chemokines, genetically modified dendritic cells with chemokine or chemokine receptors, engineered chemokine-expressing tumor cells and pDNA encoding chemokines are among these methods. Another approach for inducing a targeted immune response is fusion of a targeting antibody or antibody fragment to a chemokine. In addition, chemokines induce more effective antitumor immunity when used as adjuvants. In this regard, chemokines are codelivered along with antigens or fused as a targeting unit with antigenic moieties. In this review, several chemokines with their role in inducing immune response against different diseases are discussed, with a major emphasis on cancer.

Influence of intragenic CCL3 haplotypes and CCL3L copy number in HIV-1 infection in a sub-Saharan African population

Two CCL3 haplotypes (HapA1 and Hap-A3) and two polymorphic positions shared by the haplotypes (Hap-2SNP (single nucleotide polymorphism)) were investigated together with CCL3L copy number (CN), for their role in HIV-1 disease. Hap-A1 was associated with protection from in utero HIV-1 infection: exposed uninfected (EU) infants had higher representation of wild type (WT)/Hap-A1 than infected infants (excluding intrapartum (IP)-infected infants), which maintained significance post maternal Nevirapine (mNVP) and viral load (MVL) correction (P=0.04; odds ratio (OR)=0.33). Mother-infant pair analyses showed the protective effect of Hap-A1 is dependent on its presence in the infant. Hap-A3 was associated with increased IP transmission: WT/Hap-A3 was increased in IP-transmitting vs non-transmitting (NT) mothers, and remained significant post mNVP and MVL correction (P=0.02; OR=3.50). This deleterious effect of Hap-A3 seemed dependent on its presence in the mother. Hap-2SNP was associated with lower CD4 count in the NT mothers (P=0.03). CCL3 Hap-A1 was associated with high CCL3L CN in total (P=0.001) and EU infants (P=0.006); the effect was not additive, however, having either Hap-A1 or high CCL3L CN was more significantly (P=0.0008) associated with protection from in utero infection than Hap-A1 (P=0.028) or high CCL3L CN (P=0.002) alone. Linkage disequilibrium between Hap-A1 and high CCL3L CN appears unlikely given that a Nigerian population showed an opposite relationship.