Microparticle RSV Vaccines Presenting the G Protein CX3C Chemokine Motif in the Context of TLR Signaling Induce Protective Th1 Immune Responses and Prevent Pulmonary Eosinophilia Post-Challenge

Abstract

Layer-by-layer microparticle (LbL-MP) fabrication was used to produce synthetic vaccines presenting a fusion peptide containing RSV G protein CX3C chemokine motif and a CD8 epitope of the RSV matrix protein 2 (GM2) with or without a covalently linked TLR2 agonist (Pam3.GM2). Immunization of BALB/c mice with either GM2 or Pam3.GM2 LbL-MP in the absence of adjuvant elicited G-specific antibody responses and M2-specific CD8+ T-cell responses. Following challenge with RSV, mice immunized with the GM2 LbL-MP vaccine developed a Th2-biased immune response in the lungs with elevated levels of IL-4, IL-5, IL-13, and eotaxin in the bronchoalveolar lavage (BAL) fluid and a pulmonary influx of eosinophils. By comparison, mice immunized with the Pam3.GM2 LbL-MP vaccine had considerably lower to non-detectable levels of the Th2 cytokines and chemokines and very low numbers of eosinophils in the BAL fluid post-RSV challenge. In addition, mice immunized with the Pam3.GM2 LbL-MP also had higher levels of RSV G-specific IgG2a and IgG2b in the post-challenge BAL fluid compared to those immunized with the GM2 LbL-MP vaccine. While both candidates protected mice from infection following challenge, as evidenced by the reduction or elimination of RSV plaques, the inclusion of the TLR2 agonist yielded a more potent antibody response, greater protection, and a clear shift away from Th2/eosinophil responses. Since the failure of formalin-inactivated RSV (FI-RSV) vaccines tested in the 1960s has been hypothesized to be partly due to the ablation of host TLR engagement by the vaccine and inappropriate Th2 responses upon subsequent viral infection, these findings stress the importance of appropriate engagement of the innate immune response during initial exposure to RSV G CX3C.

Immunogenicity and protective efficacy of an RSV G S177Q central conserved domain nanoparticle vaccine

“…Blocking CX3C-CX3CR1 interaction or ablating the CX3C motif is correlated with protection against RSV disease in mice and cotton rats ( 43 , 49 , 50 , 68 ). To evaluate the efficacy of G protein CX3C-CX3CR1 blocking Abs generated in response to NP-WT or NP-S177Q vaccination, serum IgG from NP-vaccinated mice was isolated and tested.…”

“…Taken together, these support lung disease protection in mice vaccinated with NP-S177Q vaccine compared to vehicle control vaccinated mice. We also examined intracellular cytokine production by splenocytes stimulated with RSV G peptide encompassing the CCD and M2 as previously described ( 42 , 68 ), however, there were no statistical differences detected in the production of IFNγ+ or IL-4+ by CD3+/CD4+ T cells between groups (data not shown).…”

Recent Developments in Layer‐by‐Layer Assembly for Drug Delivery and Tissue Engineering Applications

“…These particles were further optimized using an immunostimulant in order to specifically direct the immune response toward a more protective immunity against RSV infection. [ 118 ]…”

“…These particles were further optimized using an immunostimulant in order to specifically direct the immune response toward a more protective immunity against RSV infection. [118] Micro-needle platforms were thoroughly developed for intradermal vaccine administration through LbL assemblies of lipids or polymers. [119,120] LbL-coated micro-needles were used for delivering the protein antigen OVA with a sustained release over 3 days after a 1-min skin injection to implant LbL films in vivo.…”

Layer-by-Layer Nanoassemblies for Vaccination Purposes

“…The study of the use of LbL particles for the vaccination against the respiratory syncytial virus was further extended by Powell et al [ 97 ]. They extended the system fabricated by Jorquera et al [ 95 ] by including CD8 epitope of the virus matrix protein (GM2) with or without covalently linked TLR2 agonist (Pam3.GM2).…”