DNA aptamer-based rolling circle amplification product as a novel immunological adjuvant

Single-stranded DNA aptamer-based rolling circle amplification as anti-chicken Salmonella bacteriostatic

Background and Aim:

Salmonella is a major foodborne pathogen in the poultry industry, wherein the control measures may include sanitation and antibacterial and vaccines. However, there have been severe global restrictions on using anti-Salmonella antibacterial agents in livestock. This situation, along with rapidly increasing drug-resistant bacterial species, has led to the exploration of unconventional methods to control Salmonella infection in poultry. In recent years, selection techniques of promising DNA aptamers have begun to permeate several medical branches, resulting in the development of numerous anti-Salmonella DNA aptamers, most of which are used as sensing molecules for diagnostic purposes. These DNA aptamers have been demonstrated to interfere with bacterial growth, multiplication, and viability. Aptamers formed in rolling circle amplification products (RCA-p) could improve the potential action of aptamer interference with bacteria. This study aimed to test the use of single-stranded DNA aptamers in the form of RCA-p as a bacteriostatic to Salmonellain vitro.

Materials and Methods:

Salmonella Typhimurium and Salmonella Enteritidis isolates were subjected to the action of anti-ST and anti-SE DNA aptamers in the form of RCA-p. Each isolate was grown on MacConkey and Luria-Bertani agar media separately in different concentrations in the presence or absence of the cognate RCA-p.

Results:

The anti-Salmonella species DNA aptamer-based RCA-p were capable of reducing bacterial growth to significant levels in vitro.

Conclusion:

We describe a potential solution for the rapidly developing drug resistance of several bacterial species. Our findings suggested that the use of non-toxic, non-immunogenic, and low-cost DNA aptamers targeting Salmonella in the form of RCA-p could inhibit the bacterial growth rate. Unlike polymerase chain reaction, RCA yields tandem repeats of single-stranded DNA at isothermal conditions, which would increase the probability of receptor-ligand clustering and increase affinity. Furthermore, as our RCA template was bivalent with two DNA aptamer sequences, we could target multiple sites or antigens on a bacterial cell.

Structural characteristics and immunomodulatory effects of sulfated polysaccharides derived from marine algae

Marine algae are becoming an important source of valuable candidates of functional food that remain unexplored. Compositional analysis showed that marine algae contain essential nutrients, such as carbohydrates, proteins, fats, and minerals, of which polysaccharides are the main bioactive component. Depending on the source, marine algae polysaccharides are sulfated, which have diverse structures and compositions that influence their biological activities. A growing body of evidence has demonstrated that sulfated polysaccharides derived from marine algae (SPs) exhibit various bioactivities, especially immunomodulation. This review aims at summarizing the structural characteristics of SPs, their immunomodulatory effects, and the structural-immunomodulatory activity relationships between them from articles in recent decade, in order to provide a theoretical basis for the further applications of SPs as promising food or feed additives and possible health products to modulate the immune response.

A sensing system constructed by combining a structure-switchable molecular beacon with nicking-enhanced rolling circle amplification for highly sensitive miRNA detection

A novel amplification assay strategy is developed for the highly sensitive detection of miRNA-21 based on a combination of a structure-switchable molecular beacon with nicking-enhanced rolling circle amplification.

Development of Hydrophobic Interaction-based DNA Supramolecules as Efficient Delivery Carriers of CpG DNA to Immune cells

Unmethylated cytosine-phosphate-guanine (CpG) DNA stimulates mammalian immune cells through recognition by Toll-like receptor 9 (TLR9). Therefore, CpG DNA is expected to be an effective adjuvant for the treatment of immune and allergic diseases. However, challenges, such as low stability against DNase and low delivery efficiency for immune cells, still need to be resolved for the application of CpG DNA. To overcome these challenges, we developed DNA supramolecules consisting of long single-stranded DNA (lss-DNA) synthesized using rolling circle amplification (RCA) and cholesterol-modified DNA (chol-DNA). Lss-DNAs containing multiple CpG motifs were annealed with complementary chol-DNAs to form DNA supramolecules through hydrophobic interactions. Transmission electron microscopy revealed that lss-DNA mixed with chol-DNA formed micrometer-sized DNA supramolecules. The formation of DNA supramolecules increased their stability against DNase compared to lss DNA, which was evaluated using FBS. Furthermore, DNA supramolecules induced three-times higher TNF-α release from RAW264.7 cells than lss-DNA alone. These results demonstrate that DNA supramolecules are efficient delivery carriers of CpG DNA to immune cells.