Intranasal immunization against influenza virus using polymeric particles.

The aim of this study was to evaluate the potential of poly(D,L-lactide-co-glycolide) nano-and microspheres, with a mean diameter of 220 nm and 8 microm, respectively, to enhance the nasal and systemic immune responses against influenza virus antigen. High encapsulation levels of antigen were achieved in all cases. Neither the molecular weight nor the antigenicity of the entrapped antigen were affected by the encapsulation procedure. Following nasal immunization, the nasal washes IgA and the serum IgG responses were evaluated. With the soluble antigen, relatively high immune responses were observed. With nanospheres, nasal washes IgA levels were significantly lower (p<0.01) and serum IgG levels were not significantly different (p>0.05) from those obtained with the soluble antigen. With microspheres, both nasal washes IgA and serum IgG levels were significantly lower (p<0.01 and <0.05, respectively) as compared to the levels found for the soluble antigen. In addition, fluorescent microspheres administered intranasally failed to reach the nasal-associated lymphoid tissue (NALT). This lack of particle uptake by NALT and the high immunogenicity of the antigen used in this study, could explain the absence of enhancement of the immune responses by the polymeric particles.