CiteAb started life as an antibody search engine. We are still actively interested in learning about how antibodies are being used in the industry and want to ensure our search engine and data is as comprehensive as it can be to reflect this.
We have noticed more than a ten-fold increase in citations for oligo-conjugated antibodies since 2019. As a result, we sought to understand more about these interesting reagents, which you can filter for in the CiteAb search.
An antibody oligonucleotide conjugate (ab-oligo), as the name would suggest, describes an antibody and oligonucleotide joined together. This opens the door for applications which combine the sensitive targeting of antibodies with the many functions of oligonucleotides.
What are oligo-conjugated antibodies used for?
Ab-oligos have peaked interest at CiteAb, given their increasing citation share and our long standing interest and involvement in the antibody sector.
Below we outline a few examples of their uses, ranging from detection, to visualisation and quantification, to multiplexing.
Immuno-PCR is a powerful protein detection technique that can be compared to traditional ELISA. In ELISA, an antibody is used to detect and quantify an analyte from a mixed sample. Similarly, in immuno-PCR the antibody, with oligonucleotide attached, is able to specifically bind to the analyte. The difference is that RT-PCR is then used to amplify the attached oligo sequence. This is more sensitive than traditional ELISA techniques which use an enzyme-substrate reaction for detection and quantification. 
Immuno-PCR has a variety of applications, ranging from immunological research to clinical diagnostics. An interesting example is immuno-PCR being used in the development of a new, highly sensitive COVID-19 serological test. 
Proximity ligation assay (PLA)
PLA is a technique used for in situ detection, visualisation and quantification of proteins or protein-protein interactions. In this assay, two antibodies bind two distinct protein targets, or epitopes of the same protein. When in close proximity oligos form circular DNA. Upon addition of DNA polymerase, rolling circle amplification takes place to amplify this DNA which is visualised by fluorescently labelled complementary oligo probes. 
PLA can be direct (using primary antibodies in the ab-oligo) or indirect (secondary ab-oligos which bind to primary antibodies). It is a commonly used method in adherent cell lines, cytospin preparations or tissue samples. As an example, a recent study developed a tau-proximity ligation assay to further understanding of Alzheimer’s disease by measuring early tau pathology. 
This term describes a field which integrates research areas such as transcriptomics and proteomics. Here we discuss CITE-seq in particular (Cellular Indexing of Transcriptomes and Epitopes by sequencing), a multimodal single cell phenotyping method. In CITE-seq, ab-oligos are used to detect proteins and then convert this into a quantitative, sequenceable readout. The antibody will detect the protein, and the readout is from the oligonucleotide. As the readout is not dependent on fluorophores, the number of simultaneous markers that can be analysed is exceptionally vast. [5,6]
Another interesting technique is ‘Cell Hashing’. This enables sample multiplexing on an independent single-cell run due to ab-oligos acting as a ‘barcode’ on each cell. The ab-oligos are used against ubiquitously expressed surface proteins, such as the MHC class I complex (beta-2-microglobulin) and the sodium-potassium ATPase-subunit (CD298). 
Can I find ab-oligo products on CiteAb?
By applying the ‘Oligo’ conjugate filter in the CiteAb antibody search, you can find ab-oligo products – see two example searches below:
We encourage you to get in touch if you offer oligo-conjugated antibodies which currently aren’t on CiteAb. We are really keen to grow our data on this fascinating reagent!
Please do contact us with any questions, queries about data we have on ab-oligo products, or if you are a supplier with these products to list.
- Rhys and the CiteAb team