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Vaccines using usually harmless adeno-associated virus vectors may exhaust key immune cells, according to new research. Human vaccine trials using the vectors should be stopped until there is more research to assure their safety, the authors suggested. The news could further complicate HIV vaccine research; however, some experts said the study was interesting but no cause for alarm.

The adeno-associated viruses (AAVs) may themselves be causing harm, said Dr. Hildegund Ertl, report co-author and director of Philadelphia's Wistar Institute Vaccine Center. In the study, which used mice, AAV vaccines directly interfered with the CD8 T-cells an HIV vaccine is supposed to muster to attack HIV, the researchers reported.

"The immune cells become exhausted," Ertl said. "It is simply a defense mechanism of T-cells: if there is too much antigen for too long a time they simply turn themselves off." Shut-down T-cells could leave a person more susceptible to infection.

from Reuters