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

Abstract

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.

Novel technology for storage and distribution of live vaccines and other biological medicines at ambient temperature

“…Calorimetric assessment of the optimized film matrix indicates that it has a Tg' above 140°C, suggesting that at each of the temperatures used in the assessment of adenovirus stability, none of the excipients were susceptible to crystallization, which could compromise the adenovirus capsid and facilitate precipitation of buffer components and other excipients, allowing the virus to remain stably suspended in an amorphous polymer matrix during long-term storage. We have shown previously that addition of a zwitterionic surfactant to our preparations at the concentration used here significantly improves the potency of an adenovirus-based Ebola vaccine (29,30) and attributed it to the fact that it is capable of significantly reducing the energy barrier for the virus to cross the lipid bilayer of the cell membrane (57). Here, we show that it is paramount for conferring stability of virus in the film matrix and rehydrated films when stored at ambient and elevated temperatures (Figs.…”

“…In this paper, we summarize our efforts to develop a novel platform that can reduce costs associated with storage, distribution, and administration of vaccines and other biological drug products. Initially, more than 400 formulations were screened for their ability to enhance the immune response of an adenovirus-based Ebola vaccine (29). Formulations providing favorable in vivo data were then assessed for their ability to stabilize recombinant adenoviruses in a thin, peelable film matrix (Fig.…”

Innate immunity to adenovirus: lessons from mice

“…These approaches have demonstrated both a significantly improved persistence of HAdv in the circulation after intravenous virus administration and a reduction in the amount of inflammatory cytokines in the blood [48,131]. Although shielding of HAdv with PEG effectively prevents virus neutralization by preexisting neutralizing antibodies, allowing for repeated gene delivery in a gene transfer or vaccination setting [132,133], the utility of this approach in other applications has limitations. Specifically, although shielding oncolytic HAdv with PEG or protein conjugates significantly increases the efficacy of oncolytic HAdvbased vectors in mouse models [130,132], after the initial round of replication, the progeny of oncolytic virus produced in tumor sites would not be covered with PEG or protein shields, thus exposing the virus to receptors and cells of the innate immune system.…”

A Respiratory Vaccine for Ebola: Close to a Reality?

“…Formulations of currently marketed biologics for nasal administration support stability at refrigerated and ambient temperatures [13,14]. Several formulations that support stability of recombinant adenoviruses (the platform of two of the vaccine candidates) for nasal administration have been described [15,16]. Information about the stability of attenuated vesicular stomatitis V viruses (VSV), the third vaccine platform is limited and should be evaluated further since storing this vaccine at ultralow temperatures currently poses a significant administrative challenge and additional expense and delay in setting up clinical trials in Africa [17].…”

“…VSV vectors have been evaluated for nasal immunization against HIV [24,25]. Formulations that stabilize recombinant adenovirus at ambient temperatures and improve the immune response have been developed for intranasal administration and could be implemented in products currently in the clinic [15][16]26].…”