RBCs coated in antigen nanoparticles elicits stronger immune response, Harvard scientists find
Scientists have found ways to attach chemical payloads to red blood cells (RBCs) in recent years which can then be delivered to specific organs or tissues. The latest development comes from scientists from the Wyss Institute at Harvard University, who have developed a new way to produce vaccines – their technique involves loading RBCs with antigens that they can then use to generate a specific immune response
RBCs carry neutralised pathogens to the spleen, where they’re passed onto antigen-presenting cells (APCs). From there, white blood cells (WBCs) also within the spleen learn to recognize these antigens, which are the molecules of a pathogen that the body uses to launch a counter-attack. This new system ensures an improved the immune response against those pathogens.
The system is named Erythrocyte-Driven Immune Targeting (EDIT).The antigen-loaded nanoparticles are made of polystyrene and coated with an antigenic protein called ovalbumin. The RBCs also had to express a lipid molecule called phosphatidyl serine (PS) in just the right amounts – too much and the spleen would register the RBCs as damaged and destroy them.
In tests on mice, the antigen nanoparticles accumulated and remained in the spleen for 24 hours after injection. The team found that the amount of EDIT RBCs in the body didn’t change. That shows that they weren’t being destroyed by the spleen.
Mice that had received the EDIT treatment also had eight times more ovalbumin T cells than mice that had just received the nanoparticles not attached to RBCs, and 2.2 times higher than in mice that had received no treatment. More antibodies against ovalbumin were also found in the blood of the EDIT mice than the others.
Most importantly, after injecting the mice with lymphoma cells, the scientists noticed that tumours grew three times slower in mice that had received EDIT than in the control or free nanoparticle groups. The EDIT mice also had lower numbers of viable cancer cells in their bodies.
The scientists believe that the new technique could be used as a new delivery system for vaccines targeting a range of infections and illnesses. But the real advantage is that it works without adjuvants – agents added to vaccines to boost the immune response – which could help speed up vaccine development.
