Prior Exposure Does Not Preclude Use of Parainfluenza Virus as a Vaccine Vector

Prior infection with Parainfluenza virus 5 (PIV5) does not prevent use of this virus, which does not cause a disease in humans, as a vector for vaccines against pathogens such as influenza or HIV.

PIV5 is a paramyxovirus that infects dogs – but not humans or other animals - and is thought to be a contributing factor to kennel cough. Kennel cough vaccines containing live PIV5 have been used in dogs for many decades, and recently PIV5 has been suggested as a possible vector for human vaccines.

One critical question concerning the use of PIV5 as a vector is whether prior exposure to PIV5 would prevent the use of PIV5-based vaccines. To answer this question investigators at the University of Georgia (Athens, USA) examined the immunogenicity of a recombinant PIV5 vector expressing the hemagglutinin (HA) of influenza A virus subtype 3 (rPIV5-H3) in dogs that were immunized against PIV5.

They reported in the November 20, 2012, online edition of the journal PLOS ONE that vaccination of the dogs containing neutralizing antibodies against PIV5 with rPIV5-H3 generated immunity against influenza A virus, indicating that PIV5-based vaccine was immunogenic in dogs with prior exposure.

Examination of a human population showed that about 29% of the individuals had been exposed to PIV5 and had developed neutralizing antibodies against it. The antibody titers in humans were lower than that in vaccinated dogs, suggesting that neutralizing antibodies in humans would be unlikely to prevent PIV5 from being an effective vector in humans.

"Safety is always our number one concern," said senior author Dr. Biao He, professor of infectious diseases at the University of Georgia. "PIV5 makes it much easier to vaccinate without having to use live pathogens. We can use this virus as a vector for all kinds of pathogens that are difficult to vaccinate against. We have developed a very strong H5N1 flu vaccine with this technique, but we are also working on vaccines for HIV, tuberculosis, and malaria."

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University of Georgia