Scientists have injected foreign substances into the body to elicit immune responses at tumor sites, but results have been limited. An NIH team is working to overcome these issues, testing a nanovaccine in mice, which has the potential to make cancer immunotherapy more effective while also reducing side effects.
National Institute for Biomedical Imaging and Bioengineering scientists developed a nanovaccine based on the injection of unmethylated cytosine-guanine oligodeoxynucleotides (CpG), a substance that occurs in bacteria, but is uncommon in mammals. While CpG does stimulate the immune response when injected into a tumor, it doesn’t spend long inside the tumor due to its molecules’ small size and negative charge, the NIBIB said in a statement.
The team’s vaccine packages CpG in a way that keeps the body from clearing it so quickly. The vaccine is dubbed a DNA-inorganic hybrid nanovaccine because it combines CpG DNA with an inorganic compound, magnesium pyrophosphate, into tiny flowerlike complexes that immune cells take up, they said in the statement. This packaging prevents the CpG molecules from degrading and can also be manipulated in size to avoid being eliminated as quickly from the body.
Adding fluorescent molecules into the mix, the team demonstrated that the nanovaccine was efficiently taken up by two different mouse immune cells. They then pitted the nanovaccine against regular CpG molecules in mice that were given melanoma. Both treatments were given in two doses 6 days apart. The nanovaccine remained in the tumors longer than the CpG molecules, and it also inhibited tumor growth to a greater degree than the CpG molecules did.
This hybrid nanovaccine could potentially improve cancer immunotherapy with its enhanced inhibitory effect on tumor growth and ability to stay inside the tumor, which cuts down on side effects on other parts of the body. In the study, the researchers used an enlarged spleen as an indicator of immunotherapy side effects. The mice treated with the nanovaccine had spleens that weighed half of what the mice treated with CpGs did, they said in the statement.
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