The continued threat of emerging, highly lethal infectious pathogens such as Middle East respiratory syndrome coronavirus (MERS-CoV) calls for the development of novel vaccine technology that offers safe and effective prophylactic measures. Here, a novel nanoparticle vaccine is developed to deliver subunit viral antigens and STING agonists in a virus-like fashion. STING agonists are first encapsulated into capsid-like hollow polymeric nanoparticles, which show multiple favorable attributes, including a pH-responsive release profile, prominent local immune activation, and reduced systemic reactogenicity. Upon subsequent antigen conjugation, the nanoparticles carry morphological semblance to native virions and facilitate codelivery of antigens and STING agonists to draining lymph nodes and immune cells for immune potentiation. Nanoparticle vaccine effectiveness is supported by the elicitation of potent neutralization antibody and antigen-specific T cell responses in mice immunized with a MERS-CoV nanoparticle vaccine candidate. Using a MERS-CoVpermissive transgenic mouse model, it is shown that mice immunized with this nanoparticle-based MERS-CoV vaccine are protected against a lethal challenge of MERS-CoV without triggering undesirable eosinophilic immunopathology. Together, the biocompatible hollow nanoparticle described herein provides an excellent strategy for delivering both subunit vaccine candidates and novel adjuvants, enabling accelerated development of effective and safe vaccines against emerging viral pathogens.

Starch phosphorylase (SP) is an enzyme used for the reversible phosphorolysis of the alpha-glucan in plant cells. When compared to its isoform in an animal cell, glycogen phosphorylase, a peptide containing 78 amino acids (L78) is inserted in the centre of the low-affinity type starch phosphorylase (L-SP). We found that the amino acid sequence of L78 had several interesting features including the presence of a PEST region, which serves as a signal for rapid degradation. Indeed, most L-SP molecules isolated from mature sweet potato roots were nicked in the middle of a molecule, but still retained their tertiary or quaternary structures, as well as full catalytic activity. The nicking sites on the L78 were identified by amino acid sequencing of these peptides, which also enabled us to propose a proteolytic process for L-SP. Enzyme kinetic studies of L-SP in the direction of starch synthesis indicated that the Km decreased during the proteolytic process when starch was used as the limiting substrate, but the Km for the other substrate (Glc-1-P) increased. On the other hand, the maximum velocities (Vmax) increased for both substrates. Mobility of the nicked L-SP was retarded on a native polyacrylamide gel containing soluble starch, indicating the increased affinity for starch. Results in this study suggested that L78 and its proteolytic modifications might play a regulatory role on the catalytic behaviour of L-SP in starch biosynthesis.

A cDNA clone of 1114 bp encoding a putative Mn-superoxide dismutase (Mn-SOD) from diatom Thallassiosira weissflogii was cloned by the PCR technique. Nucleotide sequence analysis of this cDNA clone revealed that it was translated into 201 amino acid residues. When the sequence was compared with Mn-SODs from Vibrio mimicus and Escherichia coli, as well as two Fe-SODs from E. coli and Photobacterium leiognathi, this SOD showed higher homology to Mn-SOD. The amino acid residues required to coordinate the single manganese ion were conserved in all reported Mn-SOD sequences. This cDNA was introduced in an expression vector, pET-20b(+), and transformed into E. coli BL21(DE3)pLysS. The expressed SOD protein was then purified by a His-tag column. The recombinant enzyme was heated at 55 degrees C with a time-dependent assay; the time interval for 50% inactivation was 23 min, and its thermal inactivation rate constant K(d) was 3.03 x 10(-)(2) min(-)(1). The enzyme was inactivated either in acidic pH (below 4.0) or in the presence of imidazole (above 1.6 M) and had only a moderate effect under SDS (above 4%), whereas it was not affected under an alkaline pH (above 9.0). The atomic absorption spectrometric assay showed that 0.6 atom of iron/manganese (3:1) was present in each subunit of SOD. Reconstitution study was suggested that diatom SOD was cambialistic (Fe/Mn)-SOD. The finding of this SOD cDNA could be used for a reference in comparing the differences among marine phytoplankton species and as a probe to detect the transcription level of this enzyme, which can be applied in cosmetics for skin protection or defending unesthetic effects caused by oxygen-containing free radicals.