Lipoprotein lipase is active as a monomer.

Lipoprotein lipase (LPL), the enzyme that hydrolyzes triglycerides in plasma lipoproteins, is assumed to be active only as a homodimer. In support of this idea, several groups have reported that the size of LPL, as measured by density gradient ultracentrifugation, is ∼110 kDa, twice the size of LPL monomers (∼55 kDa). Of note, however, in those studies the LPL had been incubated with heparin, a polyanionic substance that binds and stabilizes LPL. Here we revisited the assumption that LPL is active only as a homodimer. When freshly secreted human LPL (or purified preparations of LPL) was subjected to density gradient ultracentrifugation (in the absence of heparin), LPL mass and activity peaks exhibited the size expected of monomers (near the 66-kDa albumin standard). GPIHBP1-bound LPL also exhibited the size expected for a monomer. In the presence of heparin, LPL size increased, overlapping with a 97.2-kDa standard. We also used density gradient ultracentrifugation to characterize the LPL within the high-salt and low-salt peaks from a heparin-Sepharose column. The catalytically active LPL within the high-salt peak exhibited the size of monomers, whereas most of the inactive LPL in the low-salt peak was at the bottom of the tube (in aggregates). Consistent with those findings, the LPL in the low-salt peak, but not that in the high-salt peak, was easily detectable with single mAb sandwich ELISAs, in which LPL is captured and detected with the same antibody. We conclude that catalytically active LPL can exist in a monomeric state.

Rapidly produced SAM(®) vaccine against H7N9 influenza is immunogenic in mice.

The timing of vaccine availability is essential for an effective response to pandemic influenza. In 2009, vaccine became available after the disease peak, and this has motivated the development of next generation vaccine technologies for more rapid responses. The SAM(®) vaccine platform, now in pre-clinical development, is based on a synthetic, self-amplifying mRNA, delivered by a synthetic lipid nanoparticle (LNP). When used to express seasonal influenza hemagglutinin (HA), a SAM vaccine elicited potent immune responses, comparable to those elicited by a licensed influenza subunit vaccine preparation. When the sequences coding for the HA and neuraminidase (NA) genes from the H7N9 influenza outbreak in China were posted on a web-based data sharing system, the combination of rapid and accurate cell-free gene synthesis and SAM vaccine technology allowed the generation of a vaccine candidate in 8 days. Two weeks after the first immunization, mice had measurable hemagglutinin inhibition (HI) and neutralizing antibody titers against the new virus. Two weeks after the second immunization, all mice had HI titers considered protective. If the SAM vaccine platform proves safe, potent, well tolerated and effective in humans, fully synthetic vaccine technologies could provide unparalleled speed of response to stem the initial wave of influenza outbreaks, allowing first availability of a vaccine candidate days after the discovery of a new virus.