Sin Nombre virus (SNV) and Andes virus (ANDV) cause most of the hantavirus pulmonary syndrome (HPS)
cases in North and South America, respectively. The chances of a patient surviving HPS are only two in three. Previously,
we demonstrated that SNV and ANDV DNA vaccines encoding the virus envelope glycoproteins elicit high-titer neutralizing
antibodies in laboratory animals, and (for ANDV) in nonhuman primates (NHPs). In those studies, the vaccines were
delivered by gene gun or muscle electroporation. Here, we tested whether a combined SNV/ANDV DNA vaccine (HPS
DNA vaccine) could be delivered effectively using a disposable syringe jet injection (DSJI) system (PharmaJet, Inc).
PharmaJet intramuscular (IM) and intradermal (ID) needle-free devices are FDA 510(k)-cleared, simple to use, and do not
require electricity or pressurized gas. First, we tested the SNV DNA vaccine delivered by PharmaJet IM or ID devices in
rabbits and NHPs. Both IM and ID devices produced high-titer anti-SNV neutralizing antibody responses in rabbits and
NHPs. However, the ID device required at least two vaccinations in NHP to detect neutralizing antibodies in most animals,
whereas all animals vaccinated once with the IM device seroconverted. Because the IM device was more effective
in NHP, the Stratis® (PharmaJet IM device) was selected for follow-up studies. We evaluated the HPS DNA vaccine delivered
using Stratis® and found that it produced high-titer anti-SNV and anti-ANDV neutralizing antibodies in rabbits
(n=8/group) as measured by a classic plaque reduction neutralization test and a new pseudovirion neutralization assay. We
were interested in determining if the differences between DSJI delivery (e.g., high-velocity liquid penetration through tissue)
and other methods of vaccine injection, such as needle/syringe, might result in a more immunogenic DNA vaccine.
To accomplish this, we compared the HPS DNA vaccine delivered by DSJI versus needle/syringe in NHPs (n=8/group).
We found that both the anti-SNV and anti-ANDV neutralizing antibody titers were significantly higher (p-value 0.0115)
in the DSJI-vaccinated groups than the needle/syringe group. For example, the anti-SNV and anti-ANDV PRNT50 geometric
mean titers (GMTs) were 1,974 and 349 in the DSJI-vaccinated group versus 87 and 42 in the needle/syringe
group. These data demonstrate, for the first time, that a spring-powered DSJI device is capable of effectively delivering a
DNA vaccine to NHPs. Whether this HPS DNA vaccine, or any DNA vaccine, delivered by spring-powered DSJI will
elicit a strong immune response in humans, requires clinical trials.
Virology Division, U.S. Army Medical Research Institute of Infectious Diseases, Ft. Detrick, Maryland 21702, USA.