Structural and antigenic stability of H5N1 hemagglutinin trimer upon release from polyanhydride nanoparticles

Abstract

Although H5N1 avian influenza has not yet acquired the capacity to readily infect humans, should it do so, this viral pathogen would present an increasing threat to the immunologically naïve human population. Subunit vaccines based on the viral glycoprotein hemagglutinin (HA) can provide protective immunity against influenza. Polyanhydride nanoparticles have been shown to enhance efficacy of subunit vaccines, providing the dual advantages of adjuvanticity and sustained delivery resulting in enhanced protein stability and immunogenicity. In this work, a recombinant trimer of H5 (H53 ) was encapsulated and released from polyanhydride nanoparticles. Release kinetics of the encapsulated H53 were found to be dependent on polymer chemistry (i.e., hydrophobicity and molecular weight). Polyanhydride nanoparticles composed of sebacic anhydride and 1,6-bis(p-carboxyphenoxy)hexane (CPH; that degrade into more acidic monomers) released structurally stable HA H53 , while H53 released from formulations composed of CPH and 1,8-bis(p-carboxyphenoxy)-3,6-dioxaoctane (CPTEG) (that are amphiphilic and whose degradation products are less acidic) displayed unfolding of tertiary structure. However, the antigenicity of the H53 based on binding of a H5-specific monoclonal antibody was preserved upon release from all the formulations studied, demonstrating the value of polyanhydride nanoparticles as a viable platform for HA-based influenza vaccines.

Hemagglutinin-based polyanhydride nanovaccines against H5N1 influenza elicit protective virus neutralizing titers and cell-mediated immunity

“…18,19 Previously, soluble H5 HA trimers (sH5 3 ) from H5N1 influenza virus A/Whooper Swan/Mongolia/244/05 were produced using a baculovirus insect cell expression system and shown to maintain their oligomeric structure and antigenicity upon release from polyanhydride nanoparticles. 20 In this study, the immunogenicity and virus-neutralizing antibody titer in response to nanovaccine immunization were observed for approximately 2 months, and concluded with an analysis of memory T cell responses. Finally, the efficacy of the nanovaccine formulations was examined using a lowpathogenic, live-viral challenge.…”

“…By encapsulating H5 antigen into polyanhydride nanoparticles, the foundation has been laid for the design of pandemic influenza vaccines with improved efficacy by demonstrating reduced variability in the neutralizing antibody titer, enhanced T cell responses, and greater stability. 20 As mentioned above, the recent seasonal influenza vaccine is approximately 60% effective; however, this estimate has a 95% confidence interval of 5%-68%, 35 which is a substantial range that indicates the large (and unacceptable) variability of the host responses to the vaccine. Variability of vaccine effectiveness can be influenced by a large number of factors, including age, obesity, nutrition, or other disease(s) present in the host.…”

Vaccine Technologies Against Avian Influenza: Current Approaches and New Directions

“…231 Finally, a recent study demonstrated the structural and antigenic stability of HA encapsulated into polyanhydride nanoparticles. 232 When designing HA-based vaccines, preserving antigen stability is essential to enable recognition of conformational epitopes that may lead to enhanced production of neutralizing antibody titers and cross-protection. The release of stable HA immunogen after encapsulation into polyanhydride nanoparticles ultimately led to robust, cross-clade neutralizing antibody responses postimmunization that protected mice from a live viral challenge.…”

Sustained release and stabilization of therapeutic antibodies using amphiphilic polyanhydride nanoparticles

“…Biodegradable polyanhydride particles have high biocompatibility, controllable degradation rates due to their surface erosion degradation mechanism, and a favorable microenvironment resulting from their less acidic degradation products (Determan et al, 2004;Kipper et al, 2002Kipper et al, , 2006Lopac et al, 2009;Torres et al, 2007;Torres et al, 2011;Ulery et al, 2011a). Specifically, polyanhydride micro-and nanoparticles have been successfully used for sustained delivery and stabilization of several protein-based vaccines (Carrillo-Conde et al, 2010;Determan et al, 2006a;Haughney et al, 2013;Petersen et al, 2012;Ross et al, 2014;Torres et al, 2007;Ulery et al, 2011aUlery et al, , 2011b.…”