Evaluating the Costs of Endotoxin Testing


Recently, I had the opportunity to attend a fascinating symposium held at Promega featuring conservationist Steward Brand, where he described some of the projects developed by his foundation, Revive & Restore.

The organization’s mission is to apply emerging biotechnology techniques to endangered and extinct species with the intent to increase genetic diversity, provide disease resistance and facilitate adaptation to changing climates. Although the overall message of enhancing biodiversity through the application of new genetic technology was inspiring, the project that resonated most for me was related to the plight of horseshoe crabs.

Horseshoe crabs, often referred to as living fossils, include four extant species with origins dating back about 450 million years. Although they look like crabs, they belong to their own subphylum and are more closely related to spiders. When horseshoe crabs spawn, they leave their usual habitat on the ocean floor and migrate to shore in large numbers. As a result, they have been exploited for bait and fertilizer for decades.

Enter endotoxins, an indicator for bacterial contamination in biologicals, drugs and medical devices. U.S. Food & Drug Administration regulations dictate that finished products be tested for the presence of endotoxins. These pyrogenic compounds, found in the cell wall of Gram-negative bacteria, can cause fever and affect a wide range of biological activity, possibly leading to aseptic shock and death. The most common method for testing is the gel clot and Limulus Amebocyte Lysate (LAL) Test.

I first learned about the LAL test during graduate school, where it was presented as a ubiquitous and standard requirement for testing bacterial contamination in injectable drugs. I remember being fascinated that horseshoe crabs (Limulus sp.), contain a substance that could be used to detect endotoxins. Although the instructors mentioned the need to collect blood from horseshoe crabs in order to produce the test, the method or scale of this harvest wasn’t discussed, nor were the true costs of using this method of endotoxin testing.

The LAL test has served as a faster, more inexpensive replacement for the rabbit pyrogens test for the past 35 years. Every year during mating season horseshoe crabs move to shallow water, where they are removed in huge numbers. (To get an idea of scale for the harvest and read a much more comprehensive investigation of the issue, check out this article in The Atlantic, which features an archive photo of Delaware Bay horseshoe crab harvest from 1928—for fertilizer, not pharmaceutical testing.)

After collection, the crabs end up in a lab where up to 30% of their blood is drained from a needle stuck in tissue around their heart. The LAL is extracted from the blood and can yield a product worth up to $15,000/quart. In order to avoid recollection, the crabs are returned to the ocean far from the shore where they were collected a few days before. Although it’s estimated that only 10-30% of these crabs die as a result of the process, there are indications that the horseshoe crab population and their ecosystems are impacted in other ways.

Researchers at the University of New Hampshire and Plymouth State University used accelerometers attached to recently bled female horseshoe crabs to test the hypothesis that harvesting for LAL was affecting their ability to spawn. While the research supported previous estimates with a death rate of 18%, females were found to be less likely to mate after being bled.

During his talk, Brand shared results from a study still in review that confirm the effect of over-harvesting Limulus on the survival of long distance migratory shorebirds. These birds synchronize their migration with horseshoe crab spawning, which provides a needed feast of eggs before the homestretch of their journey. Along with other ecosystem threats from climate change, the accelerated decline in the horseshoe crab population and dependency of migratory birds will likely to lead to a devastating ecological domino effect.

Fortunately, a synthetic alternative to LAL, recombinant factor C (rFC), has been available for nearly 20 years. Alas, there has been no significant shift by pharmaceutical companies away from the test based on horseshoe crab blood. rFC was patented and licensed to one company, Lonza, which Brand posited as one reason for the reluctance of drug companies to adopt its use.

Obviously, relying on one source for an essential testing reagent with no competition to temper cost is quite unattractive. But that argument has less bearing now that the patent is scheduled to expire in a few months, opening the door for additional manufacturers and creating an economic incentive for switching to the synthetic test.

Another reason may be that implementing a new test would require additional resources to validate the synthetic test for products that are already being tested with the LAL. Since the LAL has been specified in FDA guidance documents on endotoxin testing for decades, quality standards for existing products are based on the LAL, limiting momentum to change.

If both tests offered the same benefits, these arguments would make sense; however, research by one of the discoverers of rFC, Jeak Ling Ding of the National University of Singapore, shows that in many respects rFC is more efficacious than LAL. Since the raw material for the LAL test depends on an organism, there is seasonal variation in the components of the processed blood that must be taken into account. The reaction of the LAL also depends on a cascade of multiple compounds that can be affected by temperature, pH and proteins—leaving the test vulnerable to false positive results.

Although Eli Lilly is the only pharmaceutical company to date to use rFC in place of LAL, It seems the tide may be turning. According to Brand, others are interested in making the transition. It seems foolish not to, given the source for LAL shows signs of dwindling due to overexploitation. Perhaps pharmaceutical companies are beginning to see the value of a “slower/better” philosophy (the cornerstone of the Long Now Foundation, another brainchild of Brand’s), rather than “faster/cheaper.” I have certainly gained a new perspective on endotoxin testing and a deep appreciation for the work of Brand and his foundation.

Does your organization use the LAL test? What is preventing you from switching to the synthetic alternative? Let us know!

The Bacteria that are Good for Us

Chains of StreptococciSalmonella. Streptococcus. Shigella. The most well-known bacteria are those that cause disease. Our relationship with them is one of combat. With good reason, we look for ways to avoid encountering them and to eliminate them when we do meet.

But not all bacteria are bad for us. Of course we have known for years that we are colonized by harmless bacteria, but recently, studies on the human microbiome have revealed many surprising things about these bacterial tenants. Studies are showing that the teeming multitudes of organisms living in and on the human body are not just harmless bystanders, but complex, interrelated communities that can have profound effects on our health.

Three studies published last week in Science add more to the growing body of microbiome surprises, showing that certain gut bacteria are not only good for us, but may even be required for the effectiveness of some anti-cancer immunotherapies.

Continue reading

Elephant Endotheliotropic Herpesvirus—A Tiny Virus Threatens the World’s Elephants

My favorite ice-breaker of all time is: “List one fact about you that no one would guess”. It is my favorite because I have an awesome answer (if I do say so myself). My go-to answer is: I spent a summer working with elephants.

It was the summer before I graduated from college, and it was really only one elephant, a five-year-old African elephant named Connie. Connie was intelligent, curious and mischievous—her favorite game with me was trying to untie my shoelaces (hint: double knotting is important). Working with her was one of the most amazing experiences of my life and left me with an abiding love for these creatures.

Elephant Endotheliotropic Herpesviruses threaten captive breeding programs. Copyright.

Understandably, I was excited last year when one of my fellow bloggers wrote about Promega helping support the work of Virginia Riddle Pearson, who was working to identify and track strains of elephant endotheliotropic herpesvirus (EEHV) in African Elephant populations. EEHV is associated with the lethal elephant hemorrhagic disease (EHD) (1). This disease is a serious threat to the captive breeding programs of these endangered creatures. Between 1962 and 2007, it accounted for 58% of the deaths of North American captive-born Asian elephants between 4 months and 15 years of age (1). These deaths include the first Asian elephant calves born at the National, Oakland and Bronx Zoos. EHD also claimed the first live-born Asian elephant calves conceived by artificial insemination in both North America and Europe. Continue reading

CRISPR: Gene Editing and Movie Madness

There are new developments in genetics coming to light every day, each with the potential to dramatically change life as we know it. The increasingly controversial gene editing system, dubbed CRISPR (Clustered Regularly Interspaced Short Palindromic Repeats), is at the root of it all. Harnessed for use in genome editing in 20131, CRISPR has given hope to researchers looking to solve various biological problems. It’s with this technology that researchers anticipate eventually having the means to genetically modify humans and rid society of genetic disorders, such as hemophilia. While this is not yet possible, the building blocks are steadily being developed. Most recently, two groundbreaking studies concerning CRISPR have been released to the public. Continue reading

Predicting the Future with Dirty Diapers

Microbiome research is booming right now, with more and more evidence that our personal health and environment are shaped and influenced by the microbes we harbor and encounter. One area of study I find particularly interesting is how the microbiome we acquire at birth affects our long-term health.

A flood of new findings have emerged related to infant microbiome research, leaving parents like me scratching their heads about whether the secrets to our children’s future health may exist in the seemingly endless stream of dirty diapers we change.

The human microbiome evolves and develops in utero and then during and after delivery is colonized by bacteria encountered during exposure to the external environment. The initial composition of microbes an infant is populated with influences their lifelong microbiome signature and can be influenced by many factors along the way, including the microbiome community of the mother, use of antibiotics or other antibacterial substances, breastfeeding, C-section birth. These variables have been correlated with disruption of the infant microbiome and associated with differences in cognitive development and the development of disease, such as asthma and allergies.

In general, these correlations are discovered by taking a fecal sample from an infant and analyzing the DNA sequences of the bacteria present. The microbiome composition of the individual is then compared against different individual characteristics (such as presence or absence of a disease) at the time of the sample and/or at later points in time. Finally researchers look for statistically significant patterns among individuals with similar characteristics or microbiome communities. This type of study can reveal associations between the microbiome and individual traits, but further experiments are needed to show causation. Continue reading

Preventing Viral Infection by Blocking Cellular Receptors with a Tethered Antibody

Cross section of mature HIV. Copyright David S. Goodsell, The Scripps Research Institute.

Cross section of mature HIV. Copyright David S. Goodsell, The Scripps Research Institute.

Finding a way to neutralize or block infection by HIV has long been pursued by viral researchers. Various treatments have been developed, driven by the need to find effective drugs to manage HIV in infected individuals. The ultimate goal is to develop a vaccine to prevent HIV from even taking hold in the body. With all of our knowledge about the cellular receptors HIV needs to enter the cell, there has to be a method to prevent a viral particle from binding and being internalized. Many researchers are pursuing neutralizing antibodies to the virus as one method. What about antibodies that target the cellular receptor recognized by the virus? In a recently published article in Proceedings of the National Academy of Sciences, antibodies to cellular receptors for rhinovirus and HIV were tethered to the plasma membrane and tested for the ability to prevent infection. Continue reading

Gut Microbes and Hypertension: Demonstrating a Causal Link

Most of us are aware that the human body is covered by and full of microorganisms. And we understand that most of these microorganisms are helpful, both in terms of competition with and protection against invading microorganisms, and in the gut, as agents of digestion.

Bacillus subtilis, an example of Firmicutes, and not a good gut microbe. By Y tambe (original uploader) - Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=49528

Bacillus subtilis, an example of Firmicutes, and not a good gut microbe. By Y tambe (original uploader) – Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=49528

In the past decade, however, research has brought compelling details implicating gut microbes in obesity, cancer, insulin resistance and such central nervous system disorders as depression, austism spectrum disorder and multiple sclerosis (Adnan, S. et al.). Yet the mechanisms and details of these associations have not been fully demonstrated.

Gut bacteria have been proven to be connected to thickening of heart vasculature, known as atherosclerosis. Researchers have demonstrated that bacteria metabolize choline and L-carnitine from food to trimethylamine, which crosses the gut barrier into circulation and reaches the liver. In the liver, trimethylamine is metabolized to the atherogenic molecule triethylamine-N-oxide (Gregory, J.C. et al., Brown and Hazen). These studies are among the few that provide a direct connection between gut microbes and a pathological condition. Continue reading

Weaving Tangled Webs with Cell-Free DNA

The ability to isolate and assay circulating cell-free DNA from plasma holds promise for improved diagnostics and treatment in the clinic. The use of blood-based non-invasive prenatal testing (NIPT) has been well described. Such testing is based on circulating cell-free fetal DNA in blood of a pregnant woman for diagnosis and screening  of chromosomal anueploidy (e.g. Trisomy 21, Down Syndrome), sex-linked diseases, and genetic diseases that are known to result from a specific mutation in a single gene (1). Additionally, most cancers carry somatic mutations that are unique to the tumors, and dying tumor cells release small pieces of their DNA into the blood stream (2). This circulating cell-free tumor DNA can be used as a biomarker to “follow” cancer progression or regression during treatment, and diagnostic methods also are being developed to detect even early stage cancers from circulating tumor DNA (3). Further, increases in circulating cell-free DNA have been well documented after intense exercise, trauma, sepsis and even associated with autoimmune diseases such as system lupus erythematosus (SLE; 1,4). In these latter examples increases in extracellular DNA are associated with evolutionarily conserved innate immune responses involving the production of neutrophil extracellular traps (NETs). Monitoring the circulating cell-free DNA of NETs has implications for treatment and diagnosis of autoimmune diseases, cardiovascular events and traumatic injuries (4–7).

How Neutrophils Weave a Defensive Web

Blood smear showing two prominent neutrophils in the field of view

Blood smear showing two prominent neutrophils in the field of view

Neutrophils are the most abundant type of white blood cell and are part of the innate immune response, participating in non-specific immune responses to injury or pathogens. They are one of three types of granuolcytes, and can be recognized by their multi-lobed nucleus and the prominent granules that fill their cytoplasm. Generally they are first to the scene of injury or infection. Early in my scientific career, I was taught that neutrophils fought disease via phagocytosis and occasionally by firing a barrage of toxic enzymes and molecules at invaders. Mostly though they released cytokines that recruited the “important” cells of the specific immune system to the area.

For these reasons, I never really thought much about neutrophils. That is until recently, when I learned about Neutrophil Extracellular Traps (NETs). It turns out that neutrophils are pretty awesome, sacrificing themselves in a cloud-like explosion of DNA, chromatin, and granule proteins Continue reading

Of Elephant Research and Wildlife Crime – Molecular Tools that Matter

Here at Promega we receive some interesting requests…

Take the case of Virginia Riddle Pearson, elephant scientist. Three years ago we received an email from Pearson requesting a donation of GoTaq G2 Taq polymerase to take with her to Africa for her field work on elephant herpesvirus. Working out of her portable field lab (a tent) in South Africa and Botswana, she needed a polymerase she could count on to perform reliably after being transported for several days (on her lap) at room temperature. Through the joint effort of her regional sales representative in New Jersey/Pennsylvania (Pearson’s lab was based out of Princeton University at the time) and our Genomics product marketing team, she received the G2 Taq she needed to take to Africa. There she was able to conduct her experiments, leading to productive results and the opportunity to continue pursuing her work. Continue reading

The Birth of a Disease? A New Anthrax-Like Disease Found in Sub-Saharan Africa

It usually starts with one; one dead animal, one sick individual, one case that a doctor thinks is unusual. These are all ways that a new disease makes its presence known. In the case of Bacillus cereus biovar anthracis, it started with a dead chimpanzee (1).  

The wild western chimpanzee was found dead in Côte d’Ivoire in 2001. An investigation led by scientists from the Robert Koch Institute in Berlin identified the pathogenic cause of death to be an atypical B. cereus isolate that caused an anthrax-like disease. Continue reading