SPRING 2011 VOLUME 4 ISSUE 1

New Protein L Biosensor For Antibody Fragment Quantitation

Wesley McGinn-Straub, Product Manager, Fortebio

Antibodies are so rich in biochemical features that nearly every piece and parcel of their structure has been harvested and put to use, leading to widespread adoption of whole molecules, Fabs, Fvs and scFvs in both medicine and biotechnology. In conjunction with the Octet instruments, ForteBio's Protein A and Protein G biosensors have accelerated protein science research and development by enabling easy, fast and accurate quantitation of whole molecule and Fc fusion proteins. However, due to the absence of an Fc domain, — to which both Protein A and Protein G bind — detection of Fab, Fv and scFv fragments on the Octet platform has required custom biosensor preparation and validation by the end user.

ForteBio's new Protein L biosensor now brings the capability for direct detection of most kappa light chain-containing antibodies to the Octet platform, providing a reliable , time-saving "out-of-box" solution for Fab, Fv and scFv fragment quantitation. The Protein L biosensor can, of course, be used to detect whole molecule antibodies that contain kappa light chains, and may be particularly useful when the target antibody demonstrates weak affinity towards both Protein A and Protein G.

Protein L, an immunoglobulin binding protein originally isolated from Peptostreptococcus magnus, binds human kappa I, III and IV and mouse kappa I light chains of antibodies and antibody fragments. This broad specificity allows the Protein L biosensor to recognize a wider range of antibody isotypes than either Protein A or G, including IgG, IgM, IgA, IgE and IgD. Across mouse, rat and human IgG subtypes, Protein L possesses "strong" binding to nearly all species and subtypes — whereas Protein A and Protein G show "weak" or "no binding" to several species and subtypes. The Protein L biosensor is especially useful for quantifying antibodies and antibody fragments from serum–based culture because Protein L does not bind bovine immunoglobulins, which often contaminate serum supplement and thereby generate significant background signal.

As has been done for both Protein A and Protein G biosensors, standard-sensitivity and high-sensitivity acquisition parameters on the Octet platform have been developed as starting points for assay development with the Protein L biosensor. Standard sensitivity conditions (2 minute read time, 400 rpm shake speed) generated a dynamic range of 0.5–2000 µg/mL using a human IgG Fab on an Octet RED96 system. Extending the read time and increasing the shake speed (10 minute read time, 1000 rpm shake speed) produced a dynamic range of 0.05–300 µg/mL. Using the same model system, the Protein L biosensor has been shown to regenerate at least 10 times in conditioned medium with less than 5% loss in capacity, making the biosensor a cost-effective solution for screening experiments. Because the interaction of each antibody with Protein L is different, results can vary with both analyte and matrix.

The Protein L biosensor can be used for a wide variety of applications in the antibody laboratory. During cell line development, it can be used to determine the productivity of pools and individual clones. During process development, rapid determination of antibody concentration using the Protein L biosensor and the Octet platform expedites the iterative process of optimizing growth conditions and culture media. The Protein L biosensor can also be used in formulation development and quality control of biologics.

For more information, visit the Protein L biosensor web page and download the Protein L datasheet and technical note. To request a quote for Protein L biosensors, visit the ordering page.

ForteBio Spreads its Wings — A Profitable Life Sciences Tools Company

Terry Salyer, VP Sales, Fortebio

The end of 2010 marked the completion of my third exciting year leading ForteBio's global distribution team, and another year of sales growth among the highest in the industry. ForteBio's continued investment in building a global sales and support team has earned the company a world-class customer list with Octet platforms placed in 21 countries. Awareness of the Octet platform continues to build as ForteBio's customers publish their successful research and share their positive opinions with other scientists regarding the value of the Octet platform. ForteBio has grown rapidly from a small start-up company to a profitable solution leader within the life science industry.

After spending almost 20 years in the life sciences industry working with scientists that use detection systems, I have found customer applications to always be interesting and diverse. ForteBio's customers in pharmaceutical, biotech, academia, diagnostics, medical and government sectors use Octet systems to detect proteins and small molecule interactions in samples originating from human, animal, and plant material. The Octet platform has enabled research to be "label-free" by allowing measurement in crude unfiltered matrices and has provided the unique ability to conduct multiple experiments on a reusable sample volume. ForteBio's customers have used the Octet platform to monitor analytes as small as molecular fragments and as large as virus particles. The company has reached out to its customers for their feedback and has strengthened the Octet platform with innovative instrument capabilities and workflows, software tools, and new biosensor chemistries through aggressive product development initiatives. The company now offers five Octet instruments with varying capabilities and affordable price points, enabling access to even budget-limited laboratories.

I sincerely believe that the biggest complement a customer can give an instrumentation company is to purchase a second instrument. The purchase of another system signifies that ForteBio's products offer a solution that has true value in the customer's workflow. As a testament to the products' usefulness and reliable performance, over one third of the ForteBio customer base have purchased two or more Octet instruments, replacing cumbersome ELISA and SPR techniques in many departments of their organizations. Many of the company's customers are upgrading to the new Octet 384 platform. In 2010, the company sold 55% more Octet 384 systems than it initially estimated for the year. The improved workflow automation and reduced sample volume requirements in the Octet 384 systems have allowed more SPR and ELISA applications to be converted to the Octet platform.

I envision 2011 to be another successful year for ForteBio, and look forward to working with new customers that will fuel future product innovations. I would like to thank all current customers for their business, feedback and loyalty.