Structural insights into the CP312R protein of the African swine fever virus.

African swine fever (ASF) is a lethal hemorrhagic disease that affects domestic pigs and wild boars. There is no medication available for ASF to date. The ability to mount antigen-specific responses to viral vectored CP312R makes it a crucial potential target for designing vaccines or drugs. This study determined the crystal structure of ASFV CP312R at 2.32 Å and found it to be a monomer with a single-stranded DNA binding core domain with a clear five-strands ß-barrel OB-fold architecture. Electrophoretic mobility shift assay and size-exclusion chromatography characterization assay further confirmed the single-stranded DNA (ssDNA)-binding property of ASFV CP312R. This study revealed the structure and preliminary ssDNA interaction mechanisms of ASFV CP312R, providing new clues for developing new antiviral strategies.

Structural Characteristics of Polysaccharide GP2a in Gardenia jasminoides and Its Immunomodulatory Effect on Macrophages.

Here, we elucidated the structural characteristics of a polysaccharide isolated from Gardenia jasminoides Ellis (labeled as GP2a) and its immunomodulatory activity. GP2a is an acidic polysaccharide with a molecular weight of 44.8 kDa, mostly comprising galacturonic acid. Methylation analysis revealed 4-GalpA (74.8%) to be the major sugar residue in GP2a. Nuclear magnetic resonance analysis indicated that its main chain comprised →4)-α-D-GalpA-6-OMe-(1→4)-α-D-GalpA-(1→ and →4)-α-D-GalpA-6-OMe-(1→2)-α-L-Rhap-(1→, with galactan and arabinans linked to the C-4 position of →2)-α-L-Rhap-(1→ residue as branched chains. Furthermore, GP2a showed no obvious toxicity to macrophages (RAW 264.7) while enhancing cell viability in a dose- and time-dependent manner. Compared with untreated cells, nitric oxide production and secretion of cytokines, such as tumor necrosis factor-α, interferon-γ, interleukin (IL)-1ß, IL-6, and granulocyte macrophage colony stimulating factor, in GP2a-treated cells significantly increased after 48 h. At 300 µg/mL GP2a concentration, there was no significant difference in the cytokine levels in GP2a- and lipopolysaccharide-treated cells (the positive control). In summary, GP2a is a pectic polysaccharide with homogalacturonan and rhamnogalacturonan-I structural regions in the main chain. Based on its immunomodulatory effects in vitro, GP2a may have potential uses in functional food and medicine.

Characterization and evaluation of an oral vaccine via nano-carrier for surface immunogenic protein (Sip) delivery against Streptococcus agalactiae infection.

Streptococcus agalactiae causes systemic disease in a variety of wild and farmed fish, resulting in high levels of morbidity and mortality, as well as serious economic losses to the Nile tilapia aquaculture industry. The development of economic and applicable oral vaccines is therefore urgently needed for the sustainable development of Nile tilapia aquaculture. In this study, mesoporous silica nanoparticles (MSNs) were fabricated using sol-gel synthesis technology, and the antigens of surface immunogenic protein (Sip) was loaded into MSNs to develop a nanovaccine MSNs-Sip@HP55. The results showed that the prepared nanovaccine exhibited pH-controlled release, which could survive in the simulated gastric environment (pH 1.5), and release antigens in the simulated intestinal environment at pH 7.4. The nanovaccine could induce innate and adaptive immune responses in Nile tilapia. When the challenge doses were 1.5 × 106, 1.18 × 106, and 0.88 × 106 CFU/mL, the relative protection rates in immunized Nile tilapia were 63.33 %, 64.23 %, and 76.31 %, respectively. Taken together, the nanovaccine exhibited a high antigen utilization rate and was easily administered orally via feeding, which could protect Nile tilapia against challenge with S. agalactiae in large-scale farms. Oral vaccine based on MSNs carriers is a potentially promising strategy for the development of fish vaccines.

Salts of 2-hydroxybenzylamine with improvements on solubility and stability: Virtual and experimental screening.

2-Hydroxybenzylamine (2-HOBA) is a drug used to effectively treat oxidative stress. To improve its aqueous solubility and thermal stability, salt screening and synthesis was carried out. The conductor-like screening model for the real solvents model (COSMO-RS) was applied to virtual screening of coformers among 200 commonly used candidates for salification of 2-HOBA. As a result, 40 hit compounds were subjected to experimental liquid-assisted grinding (LAG) with 2-HOBA, then 21 systems were characterized as new solid phases by PXRD. Nine multicomponent single crystals of 2-HOBA with succinic acid, p-aminobenzoic acid, p-nitrobenzoic acid, o-nitrobenzoic acid, p-toluic acid, 2,3-dihydroxybenzoic acid, 3,4-dihydroxybenzoic acid, p-nitrophenol, and 5-hydroxyisophthalic acid were obtained and characterized by single-crystal X-ray diffraction, powder X-ray diffraction, differential scanning calorimetry, and thermogravimetric analysis. All of them were salts and exhibited higher decomposition temperatures compared with pure 2-HOBA. The apparent aqueous solubility of three new salts, i.e., those with succinic acid, p-aminobenzoic acid, and p-nitrophenol were higher than the equilibrium solubility of 2-HOBA. The accelerated stability test indicated that all salts show excellent stability under conditions (40 °C and 75% RH) for 4 weeks. Overall, this work introduced a protocol that combined the virtual screening tool based on the COSMO-RS model and the experimental LAG method to screen new salts for a target compound. The feasibility of this protocol was confirmed in the case of 2-HOBA whose new salts were successfully obtained and represented an improvement for aqueous solubility and thermal stability.

Structural insight into African swine fever virus I73R protein reveals it as a Z-DNA binding protein.

African Swine Fever (ASF) is a highly contagious viral haemorrhagic disease of swine, leading to enormous economic losses in the swine industry. However, vaccines and drugs to treat ASF have yet to be developed. African swine fever virus (ASFV) encodes more than 150 proteins, but 50% of them have unknown functions. Here, we present the crystal structure of the ASFV I73R protein at a resolution of 2.0 Å. Similar search tools based solely on amino acid sequence shows that it has no relationships to any proteins of known function. Interestingly, the overall structure of the I73R protein shares a winged helix-turn-helix fold, structural similarity with the Z-DNA binding domain (Zα). In accordance with this result, the I73R is capable of binding to a CpG repeats DNA duplex, which has a high propensity for forming Z-DNA during the DNA binding assays. In addition, the I73R protein was shown to be expressed at both early and late stages of ASFV post-infection in PAM cells as an 8.9 kDa protein. Immunofluorescence studies revealed that the I73R protein is expressed in the nucleus at early times post-infection and gradually translocated from the nucleus to the cytoplasm. Taken together, these data indicate that the I73R could be a member of Zα family that is important in host-pathogen interaction, which paves the way for the design of inhibitors to target this severe pathogen. Further exploring the biological role of I73R during ASFV infection in vitro and in vivo will provide new clues for development of new antiviral strategies.