Intranasal Delivery of Antigen-Coated Polymer Particles Protects against Pseudomonas aeruginosa Infection

Intranasal Epitope-Polymer Vaccine Lodges Resident Memory T Cells Protecting Against Influenza Virus

Intranasal vaccines, unlike injectable vaccines, boost immunity along the respiratory tract; this can significantly limit respiratory virus replication and shedding. There remains a need to develop mucosal adjuvants and vaccine delivery systems that are both safe and effective following intranasal administration. Here, biopolymer particles (BP) densely coated with repeats of MHC class I restricted immunodominant epitopes derived from influenza A virus namely NP366, a nucleoprotein-derived epitope and PA224, a polymerase acidic subunit derived epitope, are bioengineered. These BP-NP366/PA224 can be manufactured at a high yield and are obtained at ≈93% purity, exhibiting ambient-temperature stability. Immunological characterization includes comparing systemic and mucosal immune responses mounted following intramuscular or intranasal immunization. Immunization with BP-NP366/PA224 without adjuvant triggers influenza-specific CD8+ T cell priming and memory CD8+ T cell development. Co-delivery with the adjuvant poly(I:C) significantly boosts the size and functionality of the influenza-specific pulmonary resident memory CD8+ T cell pool. Intranasal, but not intramuscular delivery of BP-NP366/PA224 with poly(I:C), provides protection against influenza virus challenge. Overall, the BP approach demonstrates as a suitable antigen formulation for intranasal delivery toward induction of systemic protective T cell responses against influenza virus.

Synthetic Particulate Subunit Vaccines for the Prevention of Q Fever

Coxiella burnetti is an intracellular bacterium that causes Q fever, a disease of worldwide importance. Q-VAX® , the approved human Q fever vaccine, is a whole cell vaccine associated with safety concerns. Here a safe particulate subunit vaccine candidate is developed that is ambient-temperature stable and can be cost-effectively manufactured. Endotoxin-free Escherichia coli is bioengineered to efficiently self-assemble biopolymer particles (BPs) that are densely coated with either strings of 18 T-cell epitopes (COX-BP) or two full-length immunodominant antigens (YbgF-BP-Com1) all derived from C. burnetii. BP vaccine candidates are ambient-temperature stable. Safety and immunogenicity are confirmed in mice and guinea pig (GP) models. YbgF-BP-Com1 elicits specific and strong humoral immune responses in GPs with IgG titers that are at least 1 000 times higher than those induced by Q-VAX® . BP vaccine candidates are not reactogenic. After challenge with C. burnetii, YbgF-BP-Com1 vaccine leads to reduced fever responses and pathogen burden in the liver and the induction of proinflammatory cytokines IL-12 and IFN-γ inducible protein (IP-10) when compared to negative control groups. These data suggest that YbgF-BP-Com1 induces functional immune responses reducing infection by C. burnetii. Collectively, these findings illustrate the potential of BPs as effective antigen carrier for Q fever vaccine development.

Q fever immunology: the quest for a safe and effective vaccine

Q fever is an infectious zoonotic disease, caused by the Gram-negative bacterium Coxiella burnetii. Transmission occurs from livestock to humans through inhalation of a survival form of the bacterium, the Small Cell Variant, often via handling of animal parturition products. Q fever manifests as an acute self-limiting febrile illness or as a chronic disease with complications such as vasculitis and endocarditis. The current preventative human Q fever vaccine Q-VAX poses limitations on its worldwide implementation due to reactogenic responses in pre-sensitized individuals. Many strategies have been undertaken to develop a universal Q fever vaccine but with little success to date. The mechanisms of the underlying reactogenic responses remain only partially understood and are important factors in the development of a safe Q fever vaccine. This review provides an overview of previous and current experimental vaccines developed for use against Q fever and proposes approaches to develop a vaccine that establishes immunological memory while eliminating harmful reactogenic responses.

Polymeric epitope-based vaccine induces protective immunity against group A Streptococcus

Group A Streptococcus (Strep A) is a life-threatening human pathogen with no licensed vaccine. Here, we used a biopolymer particle (BP) approach to display repeats of Strep A vaccine candidate peptides p*17 and K4S2 derived from M and non-M protein, respectively. BPs densely displaying both peptides (BP-p*17-S2) were successfully assembled in one-step inside an engineered endotoxin-free Escherichia coli strain. Purified BP-p*17-S2 showed a spherical core-shell morphology with a biopolymer core and peptide shell. Upon formulation with aluminum hydroxide as adjuvant, BP-p*17-S2 exhibited a mean diameter of 2.9 µm and a positive surface charge of 22 mV. No cytotoxicity was detected when tested against HEK-293 cells. Stability studies showed that BP-p*17-S2 is ambient-temperature stable. Immunized mice showed no adverse reactions, while producing high titers of peptide specific antibodies and cytokines. This immune response could be correlated with protective immunity in an animal model of infection, i.e. intranasal challenge of mice with Strep A, where a significant reduction of >100-fold of pathogen burden in nose-associated lymphoid tissue, lung, and spleen was obtained. The cost-effective scalable manufacture of ambient-temperature stable BPs coated with Strep A peptides combined with their immunogenic properties offer an attractive alternative strategy to current Strep A vaccine development.

Precision-engineering of subunit vaccine particles for prevention of infectious diseases

Vaccines remain the best approach for the prevention of infectious diseases. Protein subunit vaccines are safe compared to live-attenuated whole cell vaccines but often show reduced immunogenicity. Subunit vaccines in particulate format show improved vaccine efficacy by inducing strong immune responses leading to protective immunity against the respective pathogens. Antigens with proper conformation and function are often required to induce functional immune responses. Production of such antigens requiring post-translational modifications and/or composed of multiple complex domains in bacterial hosts remains challenging. Here, we discuss strategies to overcome these limitations toward the development of particulate vaccines eliciting desired humoral and cellular immune responses. We also describe innovative concepts of assembling particulate vaccine candidates with complex antigens bearing multiple post-translational modifications. The approaches include non-covalent attachments (e.g. biotin-avidin affinity) and covalent attachments (e.g. SpyCatcher-SpyTag) to attach post-translationally modified antigens to particles.

Pseudomonas aeruginosa: Recent Advances in Vaccine Development

Pseudomonas aeruginosa is an important opportunistic human pathogen. Using its arsenal of virulence factors and its intrinsic ability to adapt to new environments, P. aeruginosa causes a range of complicated acute and chronic infections in immunocompromised individuals. Of particular importance are burn wound infections, ventilator-associated pneumonia, and chronic infections in people with cystic fibrosis. Antibiotic resistance has rendered many of these infections challenging to treat and novel therapeutic strategies are limited. Multiple clinical studies using well-characterised virulence factors as vaccine antigens over the last 50 years have fallen short, resulting in no effective vaccination being available for clinical use. Nonetheless, progress has been made in preclinical research, namely, in the realms of antigen discovery, adjuvant use, and novel delivery systems. Herein, we briefly review the scope of P. aeruginosa clinical infections and its major important virulence factors.