Efforts have been made to improve the biological stability of phosphodiester (PO) oligonucleotides by the addition of various modifications to either the 3', 5' or both the 3' and 5' ends of an oligonucleotide. ISIS 1080, a phosphorothioate (PS) 21-mer oligonucleotide complementary to the internal AUG codon of UL13 mRNA in HSV-1, reduces the infectious yield of HSV-1 in HeLa cells to 9.0% +/- 11%. PO analogs of ISIS 1080 containing three PS linkages placed on the 3' (ISIS 1365), 5' (ISIS 1370), both the 3' and 5' (ISIS 1364) ends or with four linkages in the middle (ISIS 1400) demonstrated reduced antiviral efficacy compared to fully PS ISIS 1080. Thermal denaturation profiles demonstrated that these oligonucleotides hybridized to complementary DNA or RNA with equivalent binding affinities. All were able to support E. coli RNAse H cleavage of the HSV mRNA to which they were targeted. The stability of the congeners in cell culture medium containing 10% fetal calf serum (FCS), HeLa cytosolic extract, HeLa nuclear extract and in intact HeLa cells revealed that ISIS 1080 was most resistant to nucleolytic digestion through 48 hours. Partial PS oligonucleotides exhibited increased degradation compared to the fully thioated oligonucleotide by exonuclease activity in FCS and endonuclease activity in cell extracts or intact cells. Thus, the reduced efficacy of partial compared to fully PS oligonucleotides against HSV-1 in HeLa cells may result from increased degradation of the mixed PO/PS oligonucleotides.

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6-Azathymidine, 6-aza-2'-deoxycytidine, 6-methyl-2'-deoxyuridine, and 5,6-dimethyl-2'-deoxyuridine nucleosides have been converted to phosphoramidite synthons and incorporated into oligodeoxynucleotides (ODNs). ODNs containing from 1 to 5 of these modified pyrimidines were compared with known 2'-deoxyuridine, 5-iodo-2'-deoxyuridine, 5-bromo-2'-deoxyuridine, 5-fluoro-2'-deoxyuridine, 5-bromo-2'-deoxycytidine, and 5-methyl-2'-deoxycytidine nucleoside modifications. Stability in 10% heat inactivated fetal calf serum, binding affinities to RNA and DNA complements, and ability to support RNase H degradation of targeted RNA in DNA-RNA heteroduplexes were measured to determine structure-activity relationships. 6-Azathymidine capped ODNs show an enhanced stability in serum (7- to 12-fold increase over unmodified ODN) while maintaining hybridization properties similar to the unmodified ODNs. A 22-mer ODN having its eight thymine bases replaced by eight 6-azathymines or 5-bromouracils hybridized to a target RNA and did not inhibit RNase H mediated degradation.

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High-dose folic acid (HDFA; vitamin B9)-5 mg, given daily, has not been evaluated as a treatment to improve early stage-diabetic foot ulcer (ES-DFU) wound healing. However, HDFA has been demonstrated to correct: (a) endothelial dysfunction and decreased nitric oxide (NO) bioavailability, associated with type-2 diabetes mellitus (T2DM); and (b) hyperhomocysteinemia (HHcy) that may promote impaired DFU-wound healing. Measures of wound area (cm 2) reduction (wound closure; WC), over a 4-week period (4 W-WC), greater than 50% of the wound area, have been reported as a robust indicator of the potential for DFU-wound healing. By using this model, we examined the effectiveness of a wound treatment in promoting progressive healing and complete wound closure for the chronic, nonhealing DFU-wound. To investigate this possible relationship between HDFA and ES-DFU wound healing, a retrospective cohort study of medical records, between November 2018 and April 2019, was performed for Veterans with T2DM and ES-DFUs following treatment with HDFA. During the study period 29 (n = 29) Veterans with ES-DFU wounds who received HDFA treatment were identified. Medical record reviews of this retrospective cohort of ES-DFU Veterans receiving HDFA report 90% (26/29) experiencing complete DFU-wound closure during the study period. Of the 29 Veterans with ES-DFUs receiving HDFA, the medical records of nine (30%), with healed wounds, provided documentation suitable for 4 W-WC, pre-and post-HDFA treatment study comparisons. This study documents significant (P < .05) improvements comparing 4 W-WC values for standard treatment for Veterans with poorly progressing, worsening or stagnating ES-DFU-wounds to those for the same subjects following HDFA treatment. These observations suggest that chronic ES-DFUs treated with HDFA may experience significantly improved wound closure and complete healing (re-epithelialization) when compared with standard treatments without HDFA. With validation from RCTs, HDFA may be established as an effective treatment to promote wound healing and closure for nonhealing ES-DFUs.