Researchers Zero in on Long-Awaited RSV Vaccine

New research showed that a virus-like particle (VLP) vaccine prevented the development of the respiratory syncytial virus (RSV), a leading cause of hospitalization in infants for which a licensed inoculation is currently unavailable.

Expression of one or more viral structural proteins from cDNA results in spontaneous assembly of VLPs that resemble the real virus morphologically and immunologically, according to study lead author Dr. Pramila Walpita, an assistant professor at the University of Hawaii’s John A. Burns School of Medicine.

She said these particles are safe because they are devoid of any viral genetic material, and therefore not infectious. For this reason, Dr. Walpita and her team of researchers thought respiratory syncytial virus (RSV) VLPs would induce robust neutralizing antibody response and protect cotton rats or other animal models when challenged with live virus.

Cotton rats vaccinated with RSV VLPs adjuvanted with alum and monophosphoryl-lipid-A-induced robust neutralizing antibodies response to confer protection in the lower and upper respiratory tract based on substantial virus clearance from these sites, according to Dr. Walpita.

The VLPs induced a Th1-biased cytokine response, indicating that they are also potentially safe, noted Dr. Walpita. “To the best of our knowledge, this is the only VLP-virosomal RSV vaccine study to report protection of the lower as well as the upper respiratory tract,” she commented. “These observations warrant further evaluation of our VLPs as vaccine for prevention against RSV disease.”

That the VLP-based vaccine offered protection in the nose is important if the target patient population is younger than a year old, added Dr. Walpita, because continued virus replication in the nose results in nasal congestion, and infants obligate nasal breathing.

The Centers for Disease Control and Prevention considers RSV to be the most common cause of bronchiolitis and pneumonia in children younger than 1 year, noted the study, which reported that as many as 144,000 infants are hospitalized each year for the treatment of RSV. The virus also endangers the elderly as well as adults with cardiopulmonary disease and immunodeficiency.

Although the need for a RSV vaccination has been discussed for decades, several barriers have prevented its development, including how young infants are when infected and the virus’s ability to block long-term immunity and adapt to prevent innate immunity. In addition, noted the study, an impaired vaccine tested in the 1960s resulted in the death of 2 infants, which raised safety concerns of RSV vaccination and pumped the brakes on the development of a safe and effective vaccine.

The wait might be over. “This vaccine has the potential to become a licensed vaccine for human use,” said Dr. Walpita.

The authors reported no support from industry.

The study was published online in the journal Plos One.

—Dan Cook

Reference:

1. Walpita P, Johns LM, Tandon R, Moore ML. Mammalian cell-derived respiratory syncytial virus-like particles protect the lower as well as the upper respiratory tract. PLoS One. 2015;10(7):e0130755.