Optimized adenovirus-antibody complexes stimulate strong cellular and humoral immune responses against an encoded antigen in naive mice and those with preexisting immunity

Immune Complex Vaccination

Antibody/antigen binding results in immune complexes (IC) that have a variety of regulatory functions. One important feature is the enhanced host immune activation against antigen contained in the complex. ICs play important roles at several critical steps that lead to B and T cell activation, including antigen targeting/retention, facilitated antigen uptake, antigen presenting cell activation and proper balancing of positive and negative stimulatory signals. In both poultry industry and clinical health care, ICs have been used as preventive and therapeutic vaccines. With our deepening understanding of antibody biology, particularly in light of new revelations of regulatory functions of Fc receptors, mechanistically more precise engineering has spearheaded tailored use of this tool for infection control and cancer therapy. IC-based treatment and prophylaxis have been tested to different extents in HBV, HIV and influenza viral infection control and are actively examined as an alternative treatment for several forms of tumor. As a part of this book series, this chapter aims to discuss the mechanistic aspects of IC signaling and their impact on immune cells. We give samples how this old technology has been used by practitioners over the last several decades and suggest potential paths for future development of IC-based immune therapy.

A recombinant trivalent vaccine candidate against human adenovirus types 3, 7, and 55

Human adenoviruses types 3 (HAdV-3), 7 (HAdV-7) and 55 (HAdV-55) are major pathogens of acute respiratory infections (ARI) in children and adults. More than one type of HAdV can infect patients simultaneously, and the infections are sometimes fatal. However, there is currently no vaccine approved for general use in children and adults. Thus, development of a multivalent HAdV vaccine to combat HAdV infection becomes imperative. In this study, we constructed a new recombinant trivalent human adenovirus vaccine (rAdMHE3-h55), which expresses the hexon protein of HAdV-55 in the E3 region of rAdMHE3, a previously prepared bivalent vaccine candidate against HAdV-3 and HAdV-7. The results of in vitro neutralization assays indicate that rAdMHE3-h55 can induce the production of neutralizing antibodies against HAdV-3, HAdV-7, and HAdV-55 in mice. Furthermore, immunization with the recombinant trivalent vaccine candidate completely protected the mice challenged with HAdV-3, HAdV-7, orHAdV-55, respectively, showing lower lung viral loads and less lung Pathological changes was compared with those in unvaccinated mice. The current findings contribute to the development of a new adenovirus vaccine candidate and also advance this construction method for the generation of recombinant adenovirus vaccines. In conclusion, our recombinant trivalent vaccine rAdMHE3-h55 can provides protection against challenge with HAdV-3, HAdV-7, or HAdV-55 in mice. Future work of optimizing this vaccine candidate may lead to a more effective way of preventing respiratory diseases caused by common human adenoviruses.

Bolstering Components of the Immune Response Compromised by Prior Exposure to Adenovirus: Guided Formulation Development for a Nasal Ebola Vaccine

The severity and longevity of the current Ebola outbreak highlight the need for a fast-acting yet long-lasting vaccine for at-risk populations (medical personnel and rural villagers) where repeated prime-boost regimens are not feasible. While recombinant adenovirus (rAd)-based vaccines have conferred full protection against multiple strains of Ebola after a single immunization, their efficacy is impaired by pre-existing immunity (PEI) to adenovirus. To address this important issue, a panel of formulations was evaluated by an in vitro assay for their ability to protect rAd from neutralization. An amphiphilic polymer (F16, FW ∼39,000) significantly improved transgene expression in the presence of anti-Ad neutralizing antibodies (NAB) at concentrations of 5 times the 50% neutralizing dose (ND₅₀). In vivo performance of rAd in F16 was compared with unformulated virus, virus modified with poly(ethylene) glycol (PEG), and virus incorporated into poly(lactic-co-glycolic) acid (PLGA) polymeric beads. Histochemical analysis of lung tissue revealed that F16 promoted strong levels of transgene expression in naive mice and those that were exposed to adenovirus in the nasal cavity 28 days prior to immunization. Multiparameter flow cytometry revealed that F16 induced significantly more polyfunctional antigen-specific CD8⁺ T cells simultaneously producing IFN-γ, IL-2, and TNF-α than other test formulations. These effects were not compromised by PEI. Data from formulations that provided partial protection from challenge consistently identified specific immunological requirements necessary for protection. This approach may be useful for development of formulations for other vaccine platforms that also employ ubiquitous pathogens as carriers like the influenza virus.

A pilot study showing differences in glycosylation patterns of IgG subclasses induced by pneumococcal, meningococcal, and two types of influenza vaccines

The presence of a carbohydrate moiety on asparagine 297 in the Fc part of an IgG molecule is essential for its effector functions and thus influences its vaccine protective effect. Detailed structural carbohydrate analysis of vaccine induced IgGs is therefore of interest as this knowledge can prove valuable in vaccine research and design and when optimizing vaccine schedules. In order to better understand and exploit the protective potential of IgG antibodies, we carried out a pilot study; collecting serum or plasma from volunteers receiving different vaccines and determining the IgG subclass glycosylation patterns against specific vaccine antigens at different time points using LC-ESI-MS analysis. The four vaccines included a pneumococcal capsule polysaccharide vaccine, a meningococcal outer membrane vesicle vaccine, a seasonal influenza vaccine, and a pandemic influenza vaccine. The number of volunteers was limited, but the results following immunization indicated that the IgG subclass which dominated the response showed increased galactose and the level of sialic acid increased with time for most vaccinees. Fucose levels increased for some vaccinees but in general stayed relatively unaltered. The total background IgG glycosylation analyzed in parallel varied little with time and hence the changes seen were likely to be caused by vaccination. The presence of an adjuvant in the pandemic influenza vaccine seemed to produce simpler and less varied glycoforms compared to the adjuvant-free seasonal influenza vaccine. This pilot study demonstrates that detailed IgG glycosylation pattern analysis might be a necessary step in addition to biological testing for optimizing vaccine development and strategies.

Modeling pre-existing immunity to adenovirus in rodents: immunological requirements for successful development of a recombinant adenovirus serotype 5-based ebola vaccine

Pre-existing immunity (PEI) to human adenovirus serotype 5 (Ad5) worldwide is the primary limitation to routine clinical use of Ad5-based vectors in immunization platforms. Using systemic and mucosal PEI induction models in rodents (mice and guinea pigs), we assessed the influence of PEI on the type of adaptive immune response elicited by an Ad5-based vaccine for Ebola with respect to immunization route. Splenocytes isolated from vaccinated animals revealed that immunization by the same route in which PEI was induced significantly compromised Ebola Zaire glycoprotein (ZGP)-specific IFN-γ+ CD8+ T cells and ZGP-specific multifunctional CD8+ T cell populations. ZGP-specific IgG1 antibody levels were also significantly reduced and a sharp increase in serum anti-Ad5 neutralizing antibody (NAB) titers were noted following immunization. These immune parameters correlated with poor survival after lethal challenge with rodent-adapted Ebola Zaire virus (ZEBOV). Although the number of IFN-γ+ CD8+ T cells was reduced in animals given the vaccine by a different route from that used for PEI induction, the multifunctional CD8+ T cell response was not compromised. Survival rates in these groups were higher than when PEI was induced by the same route as immunization. These results suggest that antigen-specific multifunctional CD8(+) T cell and Th2 type antibody responses compromised by PEI to Ad5 are required for protection from Ebola. They also illustrate that methods for induction of PEI used in preclinical studies must be carefully evaluated for successful development of novel Ad5-based vaccines.

Hexon-modified recombinant E1-deleted adenovirus vectors as dual specificity vaccine carriers for influenza virus

To determine if an ordered and repetitive display of an epitope promoted induction of superior antibody responses, we compared B-cell responses to an influenza A virus epitope that was either encoded as a transgene by an adenovirus (Ad) vector or expressed on the vector's surface. To this end, we constructed a panel of influenza A virus vaccines based on chimpanzee-derived replication-defective adenovirus (AdC) vectors of serotype SAd-V25 also called AdC68. AdC68 vectors were modified to express a linear B-cell epitope of the ectodomain of matrix 2 (M2e) within variable regions 1 (VR1) or 4 (VR4) of the adenovirus hexon. Additional vectors with wild-type or M2e-modified hexon encoded M2e fused to the influenza A virus nucleoprotein (NP) as a transgene product. Hexon-modified vectors were tested for immunogenicity and efficacy in mice in comparison to vectors with native hexon expressing the M2e-NP fusion protein. Upon priming, vectors expressing M2e within VR1 of hexon induced M2e-specific antibody responses of higher magnitude and avidity than those carrying M2e within VR4 or vectors expressing the M2e as part of a transgene product. CD8(+) T-cell responses to the transgenic NP were comparable between vectors. M2e-specific antibody responses could be boosted by a second dose of the VR1 hexon-modified vector but not by repeated immunization with the VR4 hexon-modified vector.