No abstract

Staphylococcus aureus causes a broad variety of diseases. The spread of multidrug-resistant S. aureus highlights the need to develop new ways to combat S. aureus infections. Sortase A (SrtA) can anchor proteins containing LPXTG binding motifs to the bacteria surface and plays a key role in S. aureus infections, making it a promising antivirulence target. In the present study, we used a SrtA activity inhibition assay to discover that isovitexin, a Chinese herbal product, can inhibit SrtA activity with an IC 5 0 of 28.98 µg/ml. Using a fibrinogen-binding assay and a biofilm formation assay, we indirectly proved the SrtA inhibitory activity of isovitexin. Additionally, isovitexin treatment decreased the amount of staphylococcal protein A (SpA) on the surface of the cells. These data suggest that isovitexin has the potential to be an anti-infective drug against S. aureus via the inhibition of sortase activity.

Streptococcus mutans (S. mutans) is the primary etiological agent of dental caries. The S. mutans enzyme sortase A (SrtA) is responsible for anchoring bacterial cell wall surface proteins involved in host cell attachment and biofilm formation. Thus, SrtA is an attractive target for inhibiting dental caries caused by S. mutans-associated acid fermentation. In this study, we observed that astilbin, a flavanone compound extracted from Rhizoma Smilacis Glabrae, has potent inhibitory activity against the S. mutans SrtA, with an IC50 of 7.5 μg/mL. In addition, astilbin was proven to reduce the formation of biofilm while without affecting the growth of S. mutans. The results of a molecular dynamics simulation and a mutation analysis revealed that the Arg213, Leu111, and Leu116 of SrtA are important for the interaction between SrtA and astilbin. The results of this study demonstrate the potential of using astilbin as a nonbactericidal agent to modulate pathogenicity of S. mutans by inhibiting the activity of SrtA.

No abstract

Classical swine fever (CSF) is a highly contagious swine disease found worldwide that has caused devastating economic losses. However, there are few efficacious mAbs against the CSF virus (CSFV) that can be used for treatment because most mAbs against CSFV are derived from mouse hybridoma cells and these murine mAbs have disadvantages of inefficient effector functions elicitations and high immunogenicity in vivo. Accordingly, we characterized whole-porcine anti-CSFV neutralizing mAbs (NAbs) isolated directly from single B cells sorted from a CSFV-vaccinated pig using the fluoresceinated conserved linear neutralizing epitope of the CSFV E2 protein and fluorophore conjugated goat anti-pig IgG.Immunoglobulin (Ig) genes were isolated via nested PCR, and two porcine mAbs termed HK24 and HK44 were produced. We determined that these mAbs can bind to E2 protein and recognize sites within this major antigenic epitope. In addition, we found that mAbs HK24 and HK44 exhibit potent neutralizing activity against CSFV, and they can protect PK-15 cells from infections in vitro with potent IC 50 values of 9.3 μg/ml and 0.62 μg/ml, respectively.Notably, we demonstrated that these two mAbs can be used as novel reagents for detecting virus infection. These data suggest that our results not only provide a method for efficiently obtaining mAbs against CSFV but also offer promising mAb candidates for development of antibody-based diagnostic and antiviral agents.