Hydroxypropyltrimethyl ammonium chloride chitosan-based hydrogel as the split H5N1 mucosal adjuvant: Structure-activity relationship.

In this study, 2-hydroxypropyltrimethyl ammonium chloride chitosan (HTCC)-based hydrogel was devised as a mucosal adjuvant for H5N1 vaccine. Aimed to investigate the structure activity relationship between HTCC hydrogel and immune response, we prepared a series of HTCC hydrogel with defined quaternization degrees (DQs, 0%, 21%, 41%, 60%, 80%). Results suggested that with DQ increasing, the positive charge and gelation time of HTCC hydrogel increased but the viscosity decreased. We applied in vivo imaging system and found that the moderate DQ 41% prolonged antigen residence time in nasal cavity, resulting in the most potent systemic responses (IgG, IgG1, IgG2a, HI). While, the lowest DQ 0% produced the best mucosal IgA antibody responses, most likely due to the closer contact with mucosa. Furthermore, the influence of animal gender was also discussed. These data add to the growing understanding of the relationship between physicochemical features of chitosan-based hydrogel and how they influence the immune responses.

Fan Q ，Miao C ，Huang Y ，Yue H ，Wu A ，Wu J ，Wu J ，Ma G ... -  《-》

Thermal-sensitive hydrogel as adjuvant-free vaccine delivery system for H5N1 intranasal immunization.

For H5N1 influenza immunization, we developed a thermal-sensitive hydrogel as intranasal vaccine delivery system, which was formulated with N-[(2-hydroxy-3-trimethylammonium) propyl] chitosan chloride (HTCC) and α, β-glycerophosphate (α, β-GP). The flowing solution of HTCC/GP under room temperature could gelate rapidly at body temperature, which significantly prolonged the H5N1 split antigen residence time in nasal cavity. This system also enhanced the transepithelial transport via the paracellular routes due to the disorganization of ZO-1 protein in nasal epithelial tissue. In comparison to naked H5N1 split antigen and MF59 adjuvanted antigen, as designed hydrogel/H5N1 vaccine induced greater antigen-specific systemic immune responses and mucosal IgA immunity without adjuvants. Furthermore, a boosted cellular and humoral response was also obtained by examination of IFN-γ and IL-4 cytokines, respectively. In addition, hydrogel based formulation promoted the antigen-specific CD8(+) T cell immune memory as determined by the proportion of central and effector memory CD8(+) T cells in nasal associated lymphoid tissue (NALT). These results demonstrate that the HTCC hydrogel has potential as an adjuvant-free platform for H5N1 split antigen intranasal vaccination.

Wu Y ，Wei W ，Zhou M ，Wang Y ，Wu J ，Ma G ，Su Z ... -  《-》

A study of Chitosan and c-di-GMP as mucosal adjuvants for intranasal influenza H5N1 vaccine.

Highly pathogenic avian influenza A/H5N1 virus remains a potential pandemic threat, and it is essential to continue vaccine development against this subtype. A local mucosal immune response in the upper respiratory tract may stop influenza transmission. It is therefore important to develop effective intranasal pandemic influenza vaccines that induce mucosal immunity at the site of viral entry. We evaluated the humoral and cellular immune responses of two promising mucosal adjuvants (Chitosan and c-di-GMP) for intranasal influenza H5N1 vaccine in a murine model. Furthermore, we evaluated the concept of co-adjuvanting an experimental adjuvant (c-di-GMP) with chitosan. BALB/c mice were intranasally immunised with two doses of subunit NIBRG-14 (H5N1) vaccine (7·5, 1·5 or 0·3 μg haemagglutinin (HA) adjuvanted with chitosan (CSN), c-di-GMP or both adjuvants. All adjuvant formulations improved the serum and local antibody responses, with the highest responses observed in the 7·5 μg HA CSN and c-di-GMP-adjuvanted groups. The c-di-GMP provided dose sparing with protective single radial haemolysis (SRH), and haemagglutination inhibition (HI) antibody responses found in the 0·3 μg HA group. CSN elicited a Th2 response, whereas c-di-GMP induced higher frequencies of virus-specific CD4+T cells producing one or more Th1 cytokines (IFN-γ+, IL-2+, TNF-α+). A combination of the two adjuvants demonstrated effectiveness at 7·5 μg HA and triggered a more balanced Th cytokine profile. These data show that combining adjuvants can modulate the Th response and in combination with ongoing studies of adjuvanted intranasal vaccines will dictate the way forward for optimal mucosal influenza vaccines.

Svindland SC ，Pedersen GK ，Pathirana RD ，Bredholt G ，Nøstbakken JK ，Jul-Larsen Å ，Guzmán CA ，Montomoli E ，Lapini G ，Piccirella S ，Jabbal-Gill I ，Hinchcliffe M ，Cox RJ ... -  《-》

Chitosan, N,N,N-trimethyl chitosan (TMC) and 2-hydroxypropyltrimethyl ammonium chloride chitosan (HTCC): The potential immune adjuvants and nano carriers.

Vaccine is an important means to prevent diseases, which have attracted the attention of many researchers. However, the immune efficacy of vaccine is limited and requires effective antigen delivery and adjuvant systems to provide appropriate vaccines or immunotherapy antigens for improving the immune efficacy of the mucosal immune system. Recent years, the application of chitosan and its derivatives in immunization have attracted a lot of attention. Many research results proved that chitosan and its derivatives were promising vaccine adjuvants and carriers, which improved immune response for its promising mucoadhesive properties. Among the derivatives, TMC and HTCC are currently the most studied quaternized chitosans. In the first part of our review, we elucidate the preparation methods of chitosan, TMC and HTCC and the factors that may affect their immunity. In the second part, not only we introduce their application as adjuvants and carriers to improve the efficacy of vaccines, but also their application as surface modification materials to improve immune response. All in all, we hold that chitosan, TMC and HTCC are promising biomaterials that can be used to improve immune efficacy, of which TMC may have good development potential.

Zhao J ，Li J ，Jiang Z ，Tong R ，Duan X ，Bai L ，Shi J ... -  《-》

Preparation and characterization of curdlan-chitosan conjugate nanoparticles as mucosal adjuvants for intranasal influenza H1N1 subunit vaccine.

Intranasal vaccination offers crucial protection against influenza virus pandemics. However, antigens, especially subunit antigens, often fail to induce effective immune responses without the help of immune adjuvants. Our research has demonstrated that a polyelectrolyte complex, composed of curdlan sulfate/O-(2-hydroxyl) propyl-3-trimethyl ammonium chitosan chloride (CS/O-HTCC), effectively triggers both mucosal and systemic immune responses when administrated intranasal. In this study, stable nanoparticles formed by curdlan-O-HTCC conjugate (CO NP) were prepared and characterized. Furthermore, the efficacy of CO NP was evaluated as a mucosal adjuvant in an intranasal influenza H1N1 subunit vaccine. The results revealed that CO NP exhibits uniform and spherical morphology, with a size of 190.53 ± 4.22 nm, and notably, it remains stable in PBS at 4 °C for up to 6 weeks. Biological evaluation demonstrated that CO NP stimulates the activation of antigen-presenting cells (APCs), including macrophages and dendritic cells (DCs), both in vitro and in vivo. Furthermore, intranasal administration of CO NP effectively elicits cellular and humoral immune responses, notably enhancing mucosal immunity. Thus, CO NP emerges as a promising mucosal adjuvant for influenza subunit vaccines.

Jiang H ，Zhang S ，Chen Y ，Wang F ，Jiang W ... -  《-》