An influenza vaccine, constructed with nanoparticles that enhance immune response, and administered through the nose, offers strong protection against different influenza virus strains, finds a new study.

The intranasal vaccine contributed to multifaceted immune responses, leading to robust cross-protection against influenza, indicates the study published in the journal ACS Applied Materials & Interfaces. "Nanoparticle platforms have shown intriguing characteristics and great potentials in the development of next-generation cross-protective influenza vaccines," said researchers Chunhong Dong from Georgia State University.

The vaccine consists of PEI-HA/CpG nanoparticles. PEI (polyethyleneimine), a robust and versatile delivery system, can simultaneously carry antigens (haemagglutinin, HA) that induce an immune response in the body, and adjuvants (CpG) that enhance the body's immune response to an antigen for optimal immunoenhancement.

These comprehensive immune responses and cross-protection were long-lasting, exhibiting defence from the influenza virus over six months after immunisation. Intranasal vaccination is an ideal approach for infectious respiratory diseases such as influenza. Seasonal influenza vaccines generally induce narrow immune responses that rapidly decline, which leaves populations vulnerable to novel influenza strains, the study said.

Advancements in influenza vaccine technology are needed to protect against a wide range of influenza viruses. Intranasal vaccination can improve local mucosal immune responses by preventing influenza infection at the portal of virus entry, it added. In the influenza virus, HA is a protein that plays a crucial role in the early stages of virus infection. Influenza HA has a head region and stalk region.

Current influenza vaccines elicit immune responses against the HA head, but this head region is highly changeable and accounts for lowered efficiency against different strains.

The HA stalk region is more conservative across different strains of influenza viruses. Protein antigens that are administered intranasally are usually less able to provoke an immune response, so adjuvants are needed to have highly efficient intranasal vaccines. Adjuvants, such as CpG, can enhance and manipulate immune responses, thus improving the potency and breadth of protection.