Fuller Laboratories
Assays for Vector-Borne Disease Diagnosis

Lee Fuller is a pioneer in generating antigens corresponding to specific vector-borne diseases. A microbiology veteran, Fuller had started a testing lab with two colleagues more than 40 years ago. From three members and an initial emphasis on testing for infectious diseases, the lab expanded to over a hundred employees and split off a manufacturing company to produce commercial tests for the clientele. Fuller describes, “In the case of Lyme disease during the 1980s, we developed one of the first commercial assays for the largest testing lab in the country, the one that had been sending us 200 blood samples a day. We then initiated Hillcrest Biologicals to encompass commercially available reagents using the same process that had previously gone into the development of in-house assays.” Following the sale of both the testing and manufacturing companies, Fuller left to continue this work—without partners—as Fuller Laboratories. The initial plan was to work with manufacturers, but he soon realized that freelance product development doesn’t pay the bills and began manufacturing assays.

As Fuller explains, “You can be consumed by running a small business unless you truly love the work and look forward to it every morning. Hence, the products began to reflect the vector-borne bias I had enjoyed in the previous company, which continued to market my assays. I then began the task of developing better assays than I had done previously, which was even more enjoyable than the original work. This means parsing the antigens for IgG testing, then doing the same for IgM assays, and eventually, realizing they are often quite different antigens.”

Fuller Laboratories generally develops indirect immunofluorescence assays (IFA) for new or emerging agents. This reflects the most basic immunology, namely testing a bacterium or parasite against the immune (positive) or non-immune (negative) serum and then detecting this reaction with anti-human antibody tagged with fluorescein (FITC) microscopically. The positive reaction shows the pathogen in a host cell in most of the assays, the cell in which the intracellular pathogen is propagated in the BSL-2 or BSL-3 laboratory.

There are generally two basic reasons Fuller Laboratories’ clients change from IFA to an automatable assay—one being the need to automate for high specimen numbers and the other being improved accuracy. The enzyme-linked immunosorbent assay (ELISA) developed by Fuller Laboratories have an extra factor that the antigens used are custom made for either IgG or IgM testing, and rarely include both.

Most of our products are unique, and we are the only ones manufacturing them. As a result, we hardly have to market these products

For rickettsia antibody testing, the dominant antigen for IgG testing is the sole cause of false-positives in IgM testing; hence, the whole cell antigen (the bacterium) used in IFA assays cannot be reliably used for IgM testing. For the uninitiated, IgM testing allows the detection of recently produced antibody (acute phase) by the patient, whereas IgG antibody continues to rise once IgM antibody levels begin to decline after several weeks (convalescent phase).

In some diseases, it is difficult to use just a single or few distinct antigens for immunodiagnosis, which is why the western immunoblot assay displays all or most of the antigens on a paper strip—usually cellulose acetate— and the test detects the antibody reactive with an entire antigen profile. This assay serves to analyze and confirm specific patient reactivity to a particular pathogen and is the third level of assays Fuller Laboratories develops, basically when the IFA and ELISA still require further confirmation.

In order to both develop specialized assays and meet payroll demands, Fuller Laboratories serves a worldwide clientele with the assays that larger manufacturers see as “limited markets.” Most of these clients are regional, state, and national laboratories, including two of the most dominant players in the U.S.—LabCorp and Quest Diagnostics—along with various larger commercial labs as well as medical and veterinary schools across every continent. In addition, Fuller Laboratories collaborates with major universities to continually improve its products, which has helped the company initiate a new antigen specialty after one of its primary academic suppliers of Babesia antigen retired a few years ago.

The absence of alternate supply was a wake-up call and immediately led to the emergence of special interest in Babesia as a pathogen of medical and veterinary importance. With a new-found ability to propagate these hemoparasites, came the breakthrough of successfully propagating Babesia microti—a parasite transmitted by ticks—long-term in vitro and the granting of an international patent on this process. Fuller Laboratories observed that babesiosis—a malaria-like disease— was transmitted through people who were apparently healthy but had a history of the disease. The parasite lay dormant in the bodies of these individuals even after they were cured. Fuller Laboratories devised a novel method to propagate this parasite and eventually, earned the patent for “in vitro propagation of Babesia microti.”

“We are also involved in Medical Device Single Audit Program (MDSAP) to add to our winter export market because when the ticks are under the snow in the U.S. and Europe, it is summer in the Southern Hemisphere. Hence, it’s a big opportunity for us,” concludes Lee.