Synthetic particles that mimic viruses pave way for new vaccines

The nanoparticles have already been used to protect mice and monkeys against flu. Scientists hope to develop hybrid natural-synthetic vaccines that can prevent serious infections for a lifetime.

The experimental vaccine consists of a natural viral component, or antigen, plus two tiny synthetic nanoparticles.

The artificial particles are designed to stimulate specific immune system elements called toll-like receptors (TLRs).

TLRs sense molecules in viruses, bacteria and parasites and trigger signalling pathways that activate immune responses.

Lead scientist Professor Bali Pulendran, from Emory University in Atlanta, Georgia, US, said: “These particles could provide an instant way to stretch scarce supplies when access to viral material is limited, such as pandemic flu or during an emerging infection. In addition, there are many diseases, such as HIV, malaria, tuberculosis and dengue, that still lack effective vaccines, where we anticipate that this type of immunity enhancer could play a role.”

The research, reported in the journal Nature, stems from work on the yellow fever vaccine, one of the most successful ever developed.

One jab of live vaccine can protect against disease-causing versions of the virus for decades.

The Emory scientists designed particles that mimic the immune-stimulating effects of yellow fever vaccine by targeting TLRs.

Further studies showed that a vaccine incorporating two TLR-stimulating nanoparticles completely protected mice against lethal bird and swine flu strains.

Combining a viral protein with the two nanoparticles also made rhesus macaque monkeys immune to pandemic H1N1 swine flu. The monkeys showed a response five times greater than that induced by the same viral protein minus the nanoparticles.

“TLRs are like the sixth sense in our bodies, because they have an exquisite capacity to sense viruses and bacteria, and convey this information to stimulate the immune response,” said Prof Pulendran.

“We found that to get the best immune response, you need to hit more than one kind of toll-like receptor. Our aim was to create a synthetic particle that accomplishes this task.”

Emory colleague Dr Sudhir Pai Kasturi said: “We are very excited about building on this platform to design improved vaccines for existing and emerging infectious diseases.”

The particles are made from PLGA, a synthetic polymer used in biodegradable grafts and sutures.