Protein subunit vaccines offer important potential advantages over live vaccine vectors, but generally elicit weaker and shorter-lived cellular immune responses. Here we investigate the use of pH-responsive, endosomolytic polymer nanoparticles that were originally developed for RNA delivery as vaccine delivery vehicles for enhancing cellular and humoral immune responses. Micellar nanoparticles were assembled from amphiphilic diblock copolymers composed of an ampholytic core-forming block and a re-designed polycationic corona block doped with thiol-reactive pyridyl disulfide groups to enable dual-delivery of antigens and immunostimulatory CpG oligodeoxynucleotide (CpG ODN) adjuvants. Polymers assembled into 23 nm particles with simultaneous packaging of CpG ODN and a thiolated protein antigen, ovalbumin (ova). Conjugation of ova to nanoparticles significantly enhanced antigen cross-presentation in vitro relative to free ova or an unconjugated, physical mixture of the parent compounds. Subcutaneous vaccination of mice with ova-nanoparticle conjugates elicited a significantly higher CD8+ T cell response (0.5% IFN-ɣ+ of CD8+) compared to mice vaccinated with free ova or a physical mixture of the two components. Significantly, immunization with ova-nanoparticle conjugates electrostatically complexed with CpG ODN (dual-delivery) enhanced CD8+ T cell responses (3.4% IFN-ɣ+ of CD8+) 7-, 18-, and 8-fold relative to immunization with conjugates, ova administered with free CpG, or a formulation containing free ova and CpG complexed to micelles, respectively. Similarly, dual-delivery carriers significantly increased CD4+IFN-ɣ+ (Th1) responses, and elicited a balanced IgG1/IgG2c antibody response. Intradermal administration further augmented cellular immune responses, with dual-delivery carriers inducing ~7% antigen-specific CD8+ T cells. This work demonstrates the ability of pH-responsive, endosomolytic nanoparticles to actively promote antigen cross-presentation and augment cellular and humoral immune responses via dual-delivery of protein antigens and CpG ODN. Hence, pH-responsive polymeric nanoparticles offer promise as a delivery platform for protein subunit vaccines.

Background: Rheumatic heart disease (RHD) has declined dramatically in wealthier countries in the past three decades, but it remains endemic in many lower-resourced regions and can have significant costs to households. The objective of this study was to quantify the economic burden of RHD among Ugandans affected by RHD.Methods: This was a cross-sectional cost-of-illness study that randomly sampled 87 participants and their households from the Uganda National RHD registry between December 2018 and February 2020. Using a standardized survey instrument, we asked participants and household members about outpatient and inpatient RHD costs and financial coping mechanisms incurred over the past 12 months. We used descriptive statistics to analyze levels and distributions of costs and the frequency of coping strategies. Multivariate Poisson regression models were used to assess relationships between socioeconomic characteristics and utilization of financial coping mechanisms.Results: Most participants were young or women, demonstrating a wide variation in socioeconomic status. Outpatient and inpatient costs were primarily driven by transportation, medications, and laboratory tests, with overall RHD direct and indirect costs of $78 per person-year. Between 20 and 35 percent of households experienced catastrophic healthcare expenditure, with participants in the Northern and Western Regions 5–10 times more likely to experience such hardship and utilize financial coping mechanisms than counterparts in the Central Region, a wealthier area. Increases in total RHD costs were positively correlated with increasing use of coping behaviors.Conclusion: Ugandan households affected by RHD, particularly in lower-income areas, incur out-of-pocket costs that are very high relative to income, exacerbating the poverty trap. Universal health coverage policy reforms in Uganda should include mechanisms to reduce or eliminate out-of-pocket expenditures for RHD and other chronic diseases.

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