HOW DO THE NEW GENERATION VACCINES WORK?

New generation vaccines act in a similar way to conventional vaccines, but with some important advantages.

New generation vaccines act upon the immune system in different ways depending on the type of vaccine. Subunit vaccines or vaccines based on synthetic proteins (inactivated proteins) act in a way similar to that of conventional inactivated vaccines, although usually more antigen is required to induce similar responses (because they are are less antigenic).

The most important advantage of these vaccines is the lack of the entire infectious agent. This  makes it possible to differentiate between vaccinated and sick animals. This characteristic is even more important in deleted live vaccines or recombinant vaccines, which being live vaccines, induce better immune responses than those of the inactivated proteins by expressing antigens with similar characteristics to those of conventional attenuated vaccines. It is also possible to differentiate them.  

Diagram of the competitive ELISA method for the diagnosis of Aujeszky´s disease. Vaccinated animals show antibodies only against gB, while infected animals have antibodies against gE.

DNA vaccines, consisting of a DNA fragment bound to a promoter, evoke both humoral and cell-mediated immunity. This type of vaccine seems very promising for future therapy. 

Image of the last phase of the ELISA technique.

What are the problems that are we are trying to solve?

New generation vaccines solve some of the problems usually produced by the use of conventional vaccines. The following are some of them:

Safety: Sub-unit or synthetic protein vaccines avoid the problem of incomplete inactivation that can be present in some of the inactivated conventional vaccines.  These new vaccines do not need to be inactivated because they are made only of proteins. Deleted or recombinant vaccines also solve  the problem of a potential reversion to the virulent form.  

Cold chain: Sub-unity and synthetic vaccines do not require a cold chain as conventional vaccines do. 

Discrimination between sick and vaccinated animals: This is one of the most important advantages of new generation vaccines compared to conventional vaccines. In the case of Aujeszky´s disease, for example, the use of gE-negative vaccines (known before as gI-negative) allows the implementation of eradication programs because the differentiation of sick from vaccinated animals is possible thanks to the fact that vaccinated ones have only antibodies against gpII (not against gE) while carriers or sick animals have antibodies against both gE and gpII. The same approach is experimentally tested using a new sub-unity vaccine against the CPF virus.

Process of cloning and expression protein E2 of Baculovirus in order to produce the sub-unity vaccine against CPF virus. 

Sick animals suffering CSF have antibodies against the different proteins of the virus, while animals vaccinated using the sub-unity vaccine E2 only have antibodies against E2.

ELISA method can discern between vaccinated animals (with sub-unity vaccine E2). Vaccinated animals have antibodies only against E2; carriers of the disease or sick animals have antibodies both against E2 and Erns.