High-affinity five/six-letter DNA aptamers with superior specificity enabling the detection of dengue NS1 protein variants beyond the serotype identification

Genetic alphabet expansion of DNA by introducing unnatural bases (UBs), as a fifth letter, dramatically augments the affinities of DNA aptamers that bind to target proteins. To determine whether UB-containing DNA (UB-DNA) aptamers obtained by affinity selection could spontaneously achieve high specificity, we have generated a series of UB-DNA aptamers (KD: 27-182 pM) targeting each of four dengue non-structural protein 1 (DEN-NS1) serotypes. The specificity of each aptamer is remarkably high, and the aptamers can recognize the subtle variants of DEN-NS1 with at least 96.9% amino acid sequence identity, beyond the capability of serotype identification (69-80% sequence identities). Our UB-DNA aptamers specifically identified two major variants of dengue serotype 1 with 10-amino acid differences in the DEN-NS1 protein (352 aa) in Singaporeans' clinical samples. These results suggest that the high-affinity UB-DNA aptamers generated by affinity selection also acquire high target specificity. Intriguingly, one of the aptamers contained two different UBs as fifth and sixth letters, which are essential for the tight binding to the target. These two types of unnatural bases with distinct physicochemical properties profoundly expand the potential of DNA aptamers. Detection methods incorporating the UB-DNA aptamers will facilitate precise diagnoses of viral infections and other diseases.

Pulmonary function and scoliosis in children with spinal muscular atrophy types II and III

AIMS

The objectives were to evaluate the clinical course of spinal muscular atrophy (SMA) types II and III patients necessitating scoliosis surgery at the National University Hospital, Singapore.

METHODS

A retrospective review of SMA types II and III patients, born over a 10-year period between 1983 and 1992, was conducted.

RESULTS

There were eight patients: four with SMA type II and four with SMA type III. The mean age at scoliosis surgery was 9 years 7 months (range 7 years 6 months-12 years 4 months). The mean preoperative Cobb angle was 65.4 degrees (range 43-90 degrees ) and the mean postoperative Cobb angle was 22.6 degrees (range 12-45 degrees ), with a mean correction of 64.8% (range 47.7-77.8%). The decline in percentage predicted forced vital capacity (FVC) was 7.7% (95% CI: 12.4% to 3.0%) per year preoperatively and this was reduced to 3.8% (95% CI: 5.8% to 1.9%) per year postoperatively. The mean length of preoperative and postoperative lung function follow-up was 6.3 months (range 0.03-31 months) and 44 months (range 0-110 months), respectively.

CONCLUSIONS

This study suggests that pulmonary function in SMA types II and III continues to decline after scoliosis surgery, though the rate of decline is less marked. Overall, the combined results from this study and all other previously published studies are conflicting in regard to the effect of scoliosis surgery on pulmonary function in SMA types II and III, though half of the studies (3 of 6) did demonstrate a continued decline in lung function postoperatively. This decline in pulmonary function despite spinal stabilization is likely secondary to the progressive neuromuscular weakness of the disease.