Bolstering Components of the Immune Response Compromisedby Prior Exposure to Adenovirus: Guided Formulation Development fora Nasal Ebola Vaccine

摘要

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 adenovirusin the nasal cavity 28 days prior to immunization. Multiparameterflow cytometry revealed that F16 induced significantly more polyfunctionalantigen-specific CD8⁺ T cells simultaneously producingIFN-γ, IL-2, and TNF-α than other test formulations. Theseeffects were not compromised by PEI. Data from formulations that providedpartial protection from challenge consistently identified specificimmunological requirements necessary for protection. This approachmay be useful for development of formulations for other vaccine platformsthat also employ ubiquitous pathogens as carriers like the influenzavirus.