Respiratory diseases represent a serious threat to health in both the young and old. Viruses and bacteria that cause these diseases enter the body through the mucosal surfaces of the nose, lungs and gastrointestinal tract. A vaccine that provides protection against initial infection would be very advantageous. Classical vaccines are normally administered by injection but they do not provide protection in terms of preventing invasion. In contrast, a mucosal vaccine that is administered to the site(s) of pathogen ingress can provide good long term protection.
Mucosal vaccines achieve this effect by the induction of a secretary antibody (IgA) that interacts and neutralises the invading antigen (pathogen). Moreover, inoculation at one mucosal site can provide protection at other distant mucosal sites through the Common Mucosal Pathway. Mucosal vaccines also have the advantage that they can be easily administered and do not require injection.
As a spin off from a programme on the nasal administration of biotechnology products in the form of peptide and protein drugs, West Pharmaceutical Services has discovered that some of its proprietary nasal delivery systems for drugs could also be appropriate for the delivery of mucosal vaccines. Diphtheria, caused by the organism Corynebacterium diphtheriae was chosen as the target disease. The project aimed to validate the nasal vaccines system before being optimised and scaled up for testing in human trials.
A new non-injectable mucosal vaccine for the prophylaxis of diphtheria cough could have enormous potential in both social and financial terms. The existing diphtheria toxoid vaccine is associated with certain side effects and does not induce mucosal immunoglobulin A (IgA) antibodies to diphtheria that are usually detected following the disease and maybe provide long-lived immunity. A nasal vaccine that induced potent local respiratory response would be advantageous. The fact that it could be administered easily into the nasal cavity of children would be especially advantageous in the developing world where injections are still associated with problems of carrying the risk of spreading infections.