Therapeutic nucleic acid-3' -conjugates
Methods are described for improvement of the serum half life of therapeutic nucleic acids by 3′ conjugation to useful target proteins, or other large molecules with useful function. In one embodiment, a 3′ A, C or G overhang is added to ds-DNA and the primary amines conjugated using biocompatible bifunctional linkers to proteins. The resulting nucleic acid-3′-conjugates are serum nuclease-resistant and retained in vivo for long periods without rapid kidney clearance. Further, the choice of conjugate imparts additional functionality to the nucleic acid-3-conjugate. For example, if the protein in the DNA-protein conjugate is the first component of the complement cascade (Clq or Clqrs) and the DNA aptamer has been developed against surface components of a target cell, it can be used to treat bacterial or parasitic infections and cancers. If the protein is serum albumin or another common (nonimmunogenic) blood protein and the aptamer is directed against a toxin or venom, the aptamer-protein conjugate can be used as an antidote that binds and neutralizes the toxin or venom. Similar DNA (aptamer)-nanotube, -enzyme, and -toxin conjugates could also be used to target and selectively kill bacteria, parasites, and cancer cells in vivo. If the protein is an Fc antibody fragment or C3b protein from the complement system and the aptamer is developed against a bacterial cell capsular material, other cell surface component or viral cell surface component, then the aptamer-3′-protein conjugate can aid in opsonization of the target cells or viruses by phagocytic leukocytes.
1. A polymerase chain reaction (PCR)-based method of preparing a therapeutically effective amount of a DNA-3′-protein conjugate comprising:
a) preparing through PCR a ds-DNA with a 3′ overhang of adenine (A), cytosine (C), or guanine (G) deoxynucleotides on a ss-DNA strand of interest;
b) coupling the ss-DNA's primary aryl amine of the 3′ overhang to a protein conjugate via a biocompatible bifunctional linker; and
c) separating the ds DNA into ss DNA and ss-DNA-3′-protein conjugate and purifying the ss DNA-3′-protein conjugate for therapeutic use, or optionally
d) purifying the ds-DNA-3′-protein conjugate for therapeutic use.
2. The method of claim 1 , wherein said 3′ overhang is added to said ds-DNA by two rounds of amplification.
3. The method of claim 1 , wherein said 3′ overhang is added to said ds-DNA by terminal deoxynucleotide transferase (TdT).
4. The method of claim 1 , wherein the ds-DNA is an aptamer.