Nanoparticles for dengue fever vaccine

To date, researchers have struggled to create effective vaccines against the dengue virus, due to the fact that four different strains cause the disease and the vaccine must contain all of them. Now, a new type of nanoparticle allows effective vaccination of mice against one of the strains and, in addition, may harm the other strains as well

Every year, more than three hundred and fifty million people in more than one hundred and twenty countries come into contact with dengue fever, which can cause symptoms ranging from aching muscles and skin rashes to life-threatening fever. To date, researchers have struggled to create effective vaccines against the dengue virus, due to the fact that four different strains cause the disease and the vaccine must contain all of them. Now, a new type of nanoparticle, described in an article published in the scientific journal PLOS Neglected Tropical Diseases, enables effective vaccination of mice against one of the strains and, in addition, may harm the other strains as well.

Attempts to use live dengue viruses to develop a dengue vaccine have generally led to an imbalance in immunity against all four strains—for example, one potential vaccine recently tested has been shown to have poor efficacy against strain 2. Previous infections with one strain of dengue, or vaccination against Only one of the strains may lead to worsening of the disease if the patient is infected by another strain, so it is essential to have vaccines capable of attacking all four strains. In order to produce a new vaccine against the dengue virus, researchers from the University of Carolina have developed nanoparticles with a variety of shapes and sizes. Each nanoparticle binds to a key protein from strain 2 of the virus. In the next step, the researchers immunized 31 mice with a control sample or one of five different compositions of nanoparticles, each with a different particle size ranging from 55×70 to 200×200 nanometers. During the experiment, the researchers took blood samples as well as samples from the bone marrow and lymph nodes at different time points.

After mice were injected with the nanoparticles to which the selective strain 2 protein was attached, the mice developed a selective immune response to strain 2 of the dengue virus, but not to other strains. Compared to the control sample, the compositions of the nanoparticles led to a stronger immune response. Although in previous studies about similar nanoparticles a dependence of the immune response on the structure and size of the particle was found, such a trend was not clearly evident for this vaccine. Further studies will be required to determine if the antibody levels are what prevented dengue infection, and if similar nanoparticles can be developed for other strains. "Although our study focused only on strain 2 of the dengue virus, our findings form the basis for a safe and effective vaccine against all strains of the virus," say the researchers. "In addition, our research can be used to develop safe vaccines for other viruses, for example the Zika virus that affects pregnant women in South America."

The full article

Microscope image showing several round dengue virus particles in a tissue sample. [Courtesy: CDC/ Frederick Murphy]