Nanovectors: An Alternative to Traditional Biological Vaccine Methods

Nanovectors are a type of targeted delivery vehicle that transports nanoscale material. Current research is exploring their use as an alternative to traditional biological vaccine methods. Current vaccines are being enhanced through the use of nanovectors, along with the production of new methods of vaccine delivery.

The development of DNA vaccines which can directly express antigens in cells is being aided by implementation through nanovectors, allowing for improved immunological protection. Nanotechnology is also providing the potential for cancer immunotherapy, using nanovectors to produce vaccines against cancers by triggering an anti-tumor response in the body. Nanovector vaccines provide the following advantages over traditional vaccine methods:

1. Nanovectors are uniform, easily reproducible and provide precise production potential
2. Improved immune response targeting
3. Nanoscale materials can provide increased ease in application
4. Improved stability
5. Enhanced effectiveness with longer lasting protection

Nanovectors for Producing DNA Vaccines

Traditional vaccines require live or attenuated foreign material such as viruses to produce an immune response and have proved ineffective for infections such as HIV. DNA vaccines are an alternative method of providing immunological protection by introducing genetically engineered DNA into cells to directly produce antigens that form an immune response. Though studies have found that both long-term humoral and cellular immune responses have been produced from DNA vaccines, DNA plasmids injected in clinical trials were inefficiently expressed. Therefore, DNA vaccines require a delivery system in order to produce the desired enhanced immune response.

Peptide-based nanofibrous hydrogel has been highlighted as a potential nanovector for transporting a HIV DNA vaccine. Hydrogel is constructed from nanofibers in aqueous solutions and has good biocompatibility, a high loading capacity and will work in mild conditions.  The peptide-based nanofibrous hydrogel nanovector is able to condense DNA, protecting the vaccine agent from degradation and promoting the entry of the DNA into cells. Pre-clinical results found that this method strongly activated humoral and cellular immune responses, increasing the possibility of a nanovecter DNA vaccine for the HIV virus.

Nanovectors for Use in Transcutaneous Vaccination

The epidermis and dermis are abundant in antigen presenting cells which when activated, produce a strong immune response. Therefore, enhanced effectiveness may be produced through intradermal vaccinations in comparison to injected vaccines. Needle-free vaccination also has the advantage of improved patient acceptance and reduced risk of infection. Nanomaterials are able to penetrate the skin and can be modified as nanovectors for transporting compounds through follicular and interfollicular routes.

Topical application of nanoparticles causes accumulation around hair follicles before dispersing into the skin via epidermal cells.  A rat model study found that topically applied nanoparticulate agents can generate an immune response, necessary for their application as vaccines.

Nanovectors for Cancer Vaccines

Adjuvants are important immunological agents for vaccinations that can trigger innate immunity, providing a boost to vaccine effectiveness as well as reducing the amount of foreign material required for the vaccine. The glycolipid a-galactosylceramide (a-GalCer) has adjuvant properties that produce an anti-tumor effect by activating an explosive cytokine response through type I natural killer T (NKT) cells. However, clinical trials utilizing free soluble a-GalCer produced poor results potentially due to the uncontrolled delivery of a-GalCer.

shuiBy encapsulating a-GalCer into a nanovector, increase anti-tumor immunity is produced through preferential uptake by antigen presenting cells.  Nanovectors containing antibodies or ligands on the surface provide specificity through determined marker binding. This vaccine delivery system can also slow the release of a-GalCer and reduce the possibility of side effects by requiring small volumes of material.

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Sources:

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