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Norovirus vaccine elicits antibody response
Researchers from the University of North Carolina have found that an investigational multivalent norovirus vaccine elicited an antibody response in sera from 10 volunteers.
According to the report in PLoS Medicine, the vaccine elicited responses to several norovirus strains, including strains not included in the vaccine or to which the participants had previously been exposed.
The researchers evaluated the potential cross-strain immunity of a multivalent virus-like particles (VLP) candidate vaccine for norovirus genotypes GI.1 and GII.4. The investigators said GII.4 strains are responsible for 70% to 80% of documented norovirus outbreaks and are most commonly associated with outbreaks related to long-term care facilities and vacation/cruise ship outbreaks.
In this phase 1 clinical trial, 10 participants aged 18 to 49 years received a dose of the adjuvanted vaccine on days 0 and 28. Sera were collected on day 0 before the first dose was given, on day 7 after the first dose, on day 35, 7 days after the second dose, and on day 180. One participant did not return for the day 180 serum collection.
At baseline, the immunoglobulin G (IgG) geometric mean titers (GMTs) and blockade antibody titers were low, but there were significant increases in the geometric mean fold rise (GMFR) at days 7 and 35. The GMFRs for IgG and blockade antibody titers peaked at day 7, and they did not increase after the booster dose. At day 180, the IgG titers were less than twofold higher than the baseline titers for all GII.4 strains. The blockade antibody titers approached baseline by day 180.
There were cross-reactive IgG increases for GII.4 strains not included in the vaccine and not in circulation at the time of vaccination or sample collection. The blockade antibody titers for nonvaccine GII strains also increased significantly on day 7, but were not maintained at days 35 or 180.
“The success of the rotavirus vaccination campaign has elevated norovirus to the main cause of acute viral gastroenteritis in infants and young children in the U.S. and elsewhere, and, subsequently, has focused attention on the development of a norovirus vaccine,” the researchers wrote. “Here we provide evidence that a norovirus VLP-based vaccine induced broadly reactive IgG and blockade antibody response among antigenically diverse norovirus VLPs, as has been shown for mice immunized with a multivalent norovirus VLP vaccine.” – by Emily Shafer
Disclosure: Lindesmith reports receiving royalties from a licensing agreement with LigoCyte (now Takeda Pharmaceutical). Please see the full study for a list of all other authors’ relevant financial disclosures.