Parenteral vaccine delivery

The success of vaccination depends primarily on the method of presenting the antigen to the host immune system. Antigens have usually been delivered by parenteral (such as intravenous, intramuscular, intraperito-neal, intradermal, and subcutaneous) administration, but recent studies have shown that other routes of delivery such as intranasal, oral, and transdermal delivery have also been effective. In some cases, vaccination through mucosal routes resulted in better responses in IgA production. Because non-parenteral vaccine delivery presents many obvious advantages, numerous attempts have been made on the development of non-parenteral delivery of vaccines. 

The induction of an immune response by various mucosal routes is an important approach for the control of mucosally acquired infections. The apparent linked nature of the mucosal immune system enables the delivery of an antigen to any mucosal surface to have the secondary effect of potentially inducing immunity at others. Induction of a combination of systemic and secretory immune responses can be determined by the nature of the antigen, the route of administration, and the delivery system utilized. For example, traditional parenteral vaccines primarily induce IgM and IgG responses, whereas mucosal vaccination can elicit both IgG and secretory IgA responses (Corthesy, 2007). 

Payne LG, Jenkins SA, Andrianov A, Roberts BE. Water-soluble phosphazene polymers for parenteral and mucosal vaccine delivery. Pharm Biotechnol 1995 6 473-493. 

Multiple emulsions have been widely studied as means of delivering drugs via oral, topical, and parenteral routes. The applications include protein delivery (Cournarie et al., 2004), delivery of antibiotics to the vagina (Tedajo et al., 2005), sustained delivery (Vaziri and Warburton, 1994), and vaccine delivery (Bozkir and Hayta, 2004). The immunological response to a vaccine also depends on the route of administration. Most current vaccines are administered intramuscularly, which induces immunization as a systemic immunity. However, the live polio vaccine and the live typhoid vaccine are administered orally. Local immunization (oral, intranasal, or intravagina) may be preferred, since mucosal surfaces are the common entrance to many pathogens. Moreover local immunization induces both mucosal and systemic immunity. Ease of administration and avoidance of systemic side effects are additional advantages of local immunization (Walker, 1994 Shalaby, 1995). Nevertheless, successful local immunization has only been achieved with a limited number of oral vaccines. Also there are very few studies on multiple emulsions used in the immunization process, especially on parenteral and oral administration. 

In this paper after explaining why particulate systems are preferred for vaccine delivery, a brief introduction to chitosan will be given, and the importance of chitosan in particulate systems for vaccine delivery will be emphasized according to administration routes, particularly focused on needle-free routes including, oral, mucosal and pulmonary mucosa as well as skin. For comparison, examples on parenteral route will also be mentioned. 

In the following sections, the application of chitosan-based particulate systems for vaccine delivery will be reviewed according to the administration routes (mucosal, dermal and parenteral) after giving a brief introduction to each route. 

Morein, B., M. Villacres-Eriksson, and K. Lovgren-Bengtsson, Iscom, a delivery system for parenteral and mucosal vaccination. Dev Biol Stand, 1998. 92 33-9. 

Davis, S. S. (2005), The use of soluble polymers and polymer microparticles to provide improved vaccine responses after parenteral and mucosal delivery, Vaccine, 24, Suppl. 2, S7-S10. 

---