PhD candidate Austin Hertel’s (PMI) first, first author publication from the Hartman lab has been published in NPJ Vaccines!
RVFV remains a threat to livestock, particularly sheep, goats and cattle, where outbreaks of RVFV can result in high rates of mortality among pregnant and young animals. Though several livestock vaccine candidates exist, their use in pregnant animals is limited due in part to retained virulence. A next-generation vaccine candidate, RVFV-delNSs/Nsm, was developed to overcome these challenges. Importantly, it’s been shown to be safe when administered to pregnant sheep.
In this study, Austin sought to determine if this next-generation RVFV vaccine would protect offspring following maternal vaccination.
Using a model of vertical transmission previously developed in our lab by co-author Cindy McMillen, rats were vaccinated mid-gestation with RVFV-delNSs/NSm. For this study, Austin (and lab tech Ryan) learned how to milk rats in order to quantify the levels of anti-RVFV antibodies circulating in milk!
In fact, the group was able to detect anti-RVFV IgG antibodies in milk up to 28 days post vaccination! The pups themselves also had anti-RVFV IgG antibodies in their blood, which decreased over time following a peak at the time of weaning. The next question was would these maternal antibodies protect offspring to RVFV challenge?
Pups from vaccinated and unvaccinated dams were challenged with pathogenic RVFV at 23 days old and all pups from moms who received RVFV-delNSs/NSm survived challenge to 21 days!
Finally, Austin aimed to determine if pups were fully protected by maternal antibodies by applying DIVA: Differentiation of Infected from Vaccinated Animals. Given RVFV-delNSs/NSm lacks both non-structural proteins, animals who develop antibodies against NSs or NSm have been exposed to the pathogenic virus (infected) while animals who were fully protected from antibodies of vaccinated dams would not have antibodies against these proteins (vaccinated). Of the subset of pups from vaccinated moms who were tested, 3/20 pups had low levels of anti-NSs antibodies.
The assessment of vaccination during pregnancy, and protection of offspring, is a critical component in the development of countermeasures against emerging viral diseases. Great work Austin!!
— Kaleigh Connors