Vaccines have limited the spread of a number of infectious diseases such as smallpox, polio, and measles. However, vaccines against some diseases, including influenza and malaria, do not work well enough, and one of the reasons may be the timing of the presentation of the antigen and adjuvant to the immune system. Researchers at ACS Central Science have developed an injectable hydrogel that provides sustained release of vaccine components, increasing the effectiveness, quality, and duration of immune responses in mice.
Infectious diseases are caused by viruses and bacteria, toxins secreted by them, protozoa, and disease-causing fungi. Vaccination provides protection against many infectious diseases.
To defeat an infectious disease, the immune system must first recognize the causative agent of the disease. This is done by white blood cells (leukocytes), and they also begin to produce antibodies corresponding to the virus or bacteria. Antibodies serve two purposes:
attack the causative agent of the disease in order to destroy it and defeat the infection;
protect a person from this disease in the future.
Antibodies do not start to be produced immediately, as soon as a person becomes infected, this usually takes 2-3 weeks. At the next meeting with the same pathogen, the immune system is already ready to neutralize it and reacts faster. In this case, an infectious disease does not arise or is mild, that is, a person receives immunity against this disease.
Vaccination is close to a natural way of forming immunity. The vaccine contains particles of disease-causing viruses or bacteria that are recognized by the immune system. In this case, the disease itself is not formed. Thus, as a result of vaccination, the same immunity is developed as in the case of a previous illness, only without risk and suffering.
If a person vaccinated against the disease becomes infected, his immune system is immediately ready to defend the body. The causative agents of the disease are destroyed before they have time to multiply in the body. As a result, the further spread of the infection stops. However, this shield only works when a sufficient number of people are vaccinated. In parallel with the decline in the number of vaccinated inhabitants, disease outbreaks have re-emerged in many European countries. Measles is a striking example of this.
Vaccines usually contain an additional ingredient called an adjuvant that helps stimulate the immune system. In natural infections, the body is usually exposed to antigens within 2-3 weeks, compared to 1-2 days for vaccines. Eric Appel and his colleagues wondered if they could develop an injectable hydrogel that would slowly release the vaccine. components over a longer period of time, more similar to what the body is used to, which can boost the immune response.
Researchers have developed a polymer nanoparticle hydrogel that can be mixed with vaccine components. When injected under the skin of mice, the material created a localized area of inflammation that attracted certain types of immune cells, slowly releasing the antigen and adjuvant over several days. As a result, the mice that received the hydrogel produced more antibodies over a longer period of time than the mice that received the conventional vaccine.
While the new system still needs testing to see if it improves vaccine protection against specific diseases, this study demonstrates a simple and effective vaccine delivery platform that increases the effectiveness and duration of antibody-mediated immunity in mice, the researchers say.