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Oral Vaccine Could Prevent Breast Cancer

Virus initiates two-pronged attack on tumors in early study (Jan. 17)

A new oral vaccine that produces a two-pronged immune-system attack on cancer cells could be effective in preventing the recurrence of breast cancer, according to researchers at the University of Cincinnati Cancer Institute and the National Institutes of Health (NIH).

This is the first scientific report of using oral delivery of a unique virus — recombinant adeno-associated virus (AAV) — as a cancer vaccine. The new findings were reported in Molecular Therapy.

Although other oral breast vaccines have been studied in animal models, these vaccines raised human safety concerns because they used bacteria known to have potential harm to human health.

The researchers sought to develop a vaccine using AAV, a virus that has been shown to have minimal negative effects on human health and that is currently being investigated as a gene-therapy platform for treating inherited genetic disorders.

“AAV is special because the virus survives in the stomach,” said lead author Jason Steel, PhD. “Normally, you introduce a virus by mouth and it is broken down in the stomach. This virus is resistant to breakdown, which opened up the possibility of administering it orally as a cancer vaccine.”

In a preclinical animal study, the researchers tested two strains of AAV — one that was able to escape the stomach and move into the bloodstream, and the other staying in the stomach. Studies were conducted to show both the short-term and long-term effects on the reduction of breast cancer tumors. The investigators also evaluated which delivery method was more effective — oral versus the traditional intramuscular injection.

"The strain that remained in the stomach was more effective at preventing breast cancer tumors than the strain that traveled systemically — 100% of study subjects had no tumors for over a year following the treatment,” Steel said. “Additionally, we showed that oral delivery (versus intramuscular injection) was more effective, resulting in a stronger immune response with greater than a 100% increase in anti-tumor antibodies at the lower doses and increased survival.”

The researchers say that the AAV-based oral cancer vaccine holds potential as a human breast cancer prevention tool in individuals who have been treated for a certain type of breast cancer or in those judged to be at increased risk for the disease.

“We have done similar studies with different virus strains that have produced an antibody response,” Steel added. “With this virus, we get both an antibody and a tumor-killer T-cell response. By combining the two mechanisms of action in one vaccine, we are creating a two-pronged immune-system attack on the cancer cells that appears to be more effective.”

Source: University of Cincinnati Cancer Institute; January 17, 2013.

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