infectious disease

A fierce champion fighter in action, representing the incredible power of the human immune system.

(© elnariz/Fotolia)


It's vacation time. You and your family visit a country where you've never been and, in fact, your parents or grandparents had never been. You find yourself hiking beside a beautiful lake. It's a gorgeous day. You dive in. You are not alone.

How can your T cells and B cells react to a pathogen they've never seen?

In the water swim parasites, perhaps a parasite called giardia. The invader slips in through your mouth or your urinary tract. This bug is entirely new to you, and there's more. It might be new to everyone you've ever met or come into contact with. The parasite may have evolved in this setting for hundreds of thousands of years so that it's different from any giardia bug you've ever come into contact with before or that thrives in the region where you live.

How can your T cells and B cells react to a pathogen they've never seen, never knew existed, and were never inoculated against, and that you, or your doctors, in all their wisdom, could never have foreseen?

This is the infinity problem.

For years, this was the greatest mystery in immunology.

As I reported An Elegant Defense -- my book about the science of the immune system told through the lives of scientists and medical patients -- I was repeatedly struck by the profundity of this question. It is hard to overstate: how can we survive in a world with such myriad possible threats?

Matt Richtel's new book about the science of the immune system, An Elegant Defense, was published this month.

To further underscore the quandary, the immune system has to neutralize threats without killing the rest of the body. If the immune system could just kill the rest of the body too, the solution to the problem would be easy. Nuke the whole party. That obviously won't work if we are to survive. So the immune system has to be specific to the threat while also leaving most of our organism largely alone.

"God had two options," Dr. Mark Brunvand told me. "He could turn us into ten-foot-tall pimples, or he could give us the power to fight 10 to the 12th power different pathogens." That's a trillion potential bad actors. Why pimples? Pimples are filled with white blood cells, which are rich with immune system cells. In short, you could be a gigantic immune system and nothing else, or you could have some kind of secret power that allowed you to have all the other attributes of a human being—brain, heart, organs, limbs—and still somehow magically be able to fight infinite pathogens.

Dr. Brunvand is a retired Denver oncologist, one of the many medical authorities in the book – from wizened T-cell innovator Dr. Jacques Miller, to the finder of fever, Dr. Charles Dinarello, to his eminence Dr. Anthony Fauci at the National Institutes of Health to newly minted Nobel-Prize winner Jim Allison.

In the case of Dr. Brunvand, the oncologist also is integral to one of the book's narratives, a remarkable story of a friend of mine named Jason. Four years ago, he suffered late, late stage cancer, with 15 pounds of lymphoma growing in his back, and his oncologist put him into hospice. Then Jason became one of the first people ever to take an immunotherapy drug for lymphoma and his tumors disappeared. Through Jason's story, and a handful of other fascinating tales, I showcase how the immune system works.

There are two options for creating such a powerful immune system: we could be pimples or have some other magical power.

Dr. Brunvand had posited to me that there were two options for creating such a powerful and multifaceted immune system: we could be pimples or have some other magical power. You're not a pimple. So what was the ultimate solution?

Over the years, there were a handful of well-intentioned, thoughtful theories, but they strained to account for the inexplicable ability of the body to respond to virtually anything. The theories were complex and suffered from that peculiar side effect of having terrible names—like "side-chain theory" and "template-instructive hypothesis."

This was the background when along came Susumu Tonegawa.

***

Tonegawa was born in 1939, in the Japanese port city of Nagoya, and was reared during the war. Lucky for him, his father was moved around in his job, and so Tonegawa grew up in smaller towns. Otherwise, he might've been in Nagoya on May 14,1944, when the United States sent nearly 550 B-29 bombers to take out key industrial sites there and destroyed huge swaths of the city.

Fifteen years later, in 1959, Tonegawa was a promising student when a professor in Kyoto told him that he should go to the United States because Japan lacked adequate graduate training in molecular biology. A clear, noteworthy phenomenon was taking shape: Immunology and its greatest discoveries were an international affair, discoveries made through cooperation among the world's best brains, national boundaries be damned.

Tonegawa wound up at the University of California at San Diego, at a lab in La Jolla, "the beautiful Southern California town near the Mexican border." There, in multicultural paradise, he received his PhD, studying in the lab of Masaki Hayashi and then moved to the lab of Renato Dulbecco. Dr. Dulbecco was born in Italy, got a medical degree, was recruited to serve in World War II, where he fought the French and then, when Italian fascism collapsed, joined the resistance and fought the Germans. (Eventually, he came to the United States and in 1975 won a Nobel Prize for using molecular biology to show how viruses can lead, in some cases, to tumor creation.)

In 1970, Tonegawa—now armed with a PhD—faced his own immigration conundrum. His visa was set to expire by the end of 1970, and he was forced to leave the country for two years before he could return. He found a job in Switzerland at the Basel Institute for Immunology.

***

Around this time, new technology had emerged that allowed scientists to isolate different segments of an organism's genetic material. The technology allowed segments to be "cut" and then compared to one another. A truism emerged: If a researcher took one organism's genome and cut precisely the same segment over and over again, the resulting fragment of genetic material would match each time.

When you jump in that lake in a foreign land, filled with alien bugs, your body, astonishingly, well might have a defender that recognizes the creature.

This might sound obvious, but it was key to defining the consistency of an organism's genetic structure.

Then Tonegawa found the anomaly.

He was cutting segments of genetic material from within B cells. He began by comparing the segments from immature B cells, meaning, immune system cells that were still developing. When he compared identical segments in these cells, they yielded, predictably, identical fragments of genetic material. That was consistent with all previous knowledge.

But when he compared the segments to identical regions in mature B cells, the result was entirely different. This was new, distinct from any other cell or organism that had been studied. The underlying genetic material had changed.

"It was a big revelation," said Ruslan Medzhitov, a Yale scholar. "What he found, and is currently known, is that the antibody-encoding genes are unlike all other normal genes."

The antibody-encoding genes are unlike all other normal genes.

Yes, I used italics. Your immune system's incredible capabilities begin from a remarkable twist of genetics. When your immune system takes shape, it scrambles itself into millions of different combinations, random mixtures and blends. It is a kind of genetic Big Bang that creates inside your body all kinds of defenders aimed at recognizing all kinds of alien life forms.

So when you jump in that lake in a foreign land, filled with alien bugs, your body, astonishingly, well might have a defender that recognizes the creature.

Light the fireworks and send down the streamers!

As Tonegawa explored further, he discovered a pattern that described the differences between immature B cells and mature ones. Each of them shared key genetic material with one major variance: In the immature B cell, that crucial genetic material was mixed in with, and separated by, a whole array of other genetic material.

As the B cell matured into a fully functioning immune system cell, much of the genetic material dropped out. And not just that: In each maturing B cell, different material dropped out. What had begun as a vast array of genetic coding sharpened into this particular, even unique, strand of genetic material.

***

This is complex stuff. But a pep talk: This section is as deep and important as any in describing the wonder of the human body. Dear reader, please soldier on!

***

Researchers, who, eventually, sought a handy way to define the nature of the genetic change to the material of genes, labeled the key genetic material in an antibody with three initials: V, D, and J.

The letter V stands for variable. The variable part of the genetic material is drawn from hundreds of genes.

D stands for diversity, which is drawn from a pool of dozens of different genes.

And J is drawn from another half dozen genes.

In an immature B cell, the strands of V, D, and J material are in separate groupings, and they are separated by a relatively massive distance. But as the cell matures, a single, random copy of V remains, along with a single each of D and J, and all the other intervening material drops out. As I began to grasp this, it helped me to picture a line of genetic material stretching many miles. Suddenly, three random pieces step forward, and the rest drops away.

The combination of these genetic slices, grouped and condensed into a single cell, creates, by the power of math, trillions of different and virtually unique genetic codes.

In anticipation of threats from the unfathomable, our defenses evolved as infinity machines.

Or if you prefer a different metaphor, the body has randomly made hundreds of millions of different keys, or antibodies. Each fits a lock that is located on a pathogen. Many of these antibodies are combined such that they are alien genetic material—at least to us—and their locks will never surface in the human body. Some may not exist in the entire universe. Our bodies have come stocked with keys to the rarest and even unimaginable locks, forms of evil the world has not yet seen, but someday might. In anticipation of threats from the unfathomable, our defenses evolved as infinity machines.

"The discoveries of Tonegawa explain the genetic background allowing the enormous richness of variation among antibodies," the Nobel Prize committee wrote in its award to him years later, in 1987. "Beyond deeper knowledge of the basic structure of the immune system these discoveries will have importance in improving immunological therapy of different kinds, such as, for instance, the enforcement of vaccinations and inhibition of reactions during transplantation. Another area of importance is those diseases where the immune defense of the individual now attacks the body's own tissues, the so-called autoimmune diseases."

Indeed, these revelations are part of a period of time it would be fair to call the era of immunology, stretching from the middle of the 20th century to the present. During that period, we've come from sheer ignorance of the most basic aspects of the immune system to now being able to tinker under the hood with monoclonal antibodies and other therapies. And we are, in many ways, just at the beginning.

Matt Richtel
Matt Richtel is a best-selling author and Pulitzer Prize-winning reporter for the New York Times based in San Francisco. He joined the staff in 2000, and his work has focused on science, technology, business and narrative-driven story telling around these issues, including cancer immunotherapy, electronic cigarettes, and the impact of heavy technology use on behavior and the brain. In 2010 he won the Pulitzer Prize for National Reporting, for his series of articles on the hazardous use of cell phones, computers and other devices while driving. His non-fiction thriller A Deadly Wandering explored these issues, was a New York Times bestseller. He is also the author of four acclaimed science and tech-centric thrillers, including, most recently, The Doomsday Equation.

A sick woman sneezing into a tissue.

(© Subbotina Anna/Fotolia)


It's a familiar scenario: You show up at the doctor feeling miserable—sneezing, coughing, lethargic. We've all been there. And we've all been told the same answer: we're suffering from "a virus."

Failing to establish a specific microbial cause undermines the health of individual patients—and potentially the public at large.

Some patients may be satisfied with that diagnosis, others may be frustrated, and still others may demand antibiotic treatment for a bacterial infection that is usually not even present. As an infectious disease doctor who specializes in pandemic preparedness, I detest using the catch-all "virus" diagnosis for a range of symptoms from common colds to life-threatening pneumonias to unexplained fevers. Failing to establish a specific microbial cause undermines the health of individual patients—and potentially the public at large.

Confirming a specific diagnosis to determine which virus is behind those nasty symptoms is not just an academic exercise. The benefits are plentiful. Patients can forego antibiotic treatment, possibly benefit from antiviral treatment, understand their illness, and be given a prognosis. Additionally, if hospitalized, patients with certain viral infections require specific types of precautions so as not to spread the virus within the hospital.

Another largely undervalued benefit of such an approach is that it allows experts to begin assembling an arsenal of tools that might stave off a global health catastrophe. With severe pandemics, such as the 1918 influenza pandemic that killed 50 to 100 million people, it can be challenging to predict which of the myriad microbial species (bacteria, viruses, fungi, parasites, prions) will be the most likely cause. Many different approaches to prediction exist, but there is a general lack of rigorous analysis about what it takes for any microorganism to reach the pantheon of pandemic pathogens. My colleagues and I at the Johns Hopkins Center for Health Security recently developed a new framework to understand the characteristics of pandemic pathogens.

One of our major conclusions is that the most likely pandemic pathogen will be viral and spread through respiratory means. Viruses rise to the top of the list because, when compared to other types of infectious agents, they have several features that confer pandemic potential: they mutate a lot, the speed of infection is rapid, and there are no broad-spectrum antivirals akin to broad-spectrum antibacterial agents. Contagion through breathing, coughing, and sneezing is likely because it is much more difficult for standard public health measures to extinguish respiratory spread agents compared to other routes of transmission like food, body fluids, or mosquitoes.

With this information, physicians and scientists can begin taking actions to prevent spread of the infection by developing vaccines, testing antiviral compounds, and making diagnostic tests for concerning viruses.

Many of the viral families that could pose a pandemic threat are very common causes of upper respiratory infections like influenza, the common cold, and bronchitis. These viruses cause a wide range of illnesses from mild coughs to serious pneumonias. Indeed, the 2009 H1N1 influenza pandemic virus was discovered in San Diego in a child with very mild illness in whom viral diagnostic testing was pursued. This event highlights the fact that such diseases are not only found in exotic locations in the developing world, but could appear anywhere.

Understanding the patterns of respiratory virus infections -- how frequent they are, which strains are predominating, changes in severity of disease, expanding geographic range -- may provide a glimpse into the first forays of a new human virus or an alert to changing behavior from a well-known virus. With this information, physicians and scientists can begin taking actions to prevent spread of the infection by developing vaccines, testing antiviral compounds, and making diagnostic tests for concerning viruses. Additionally, alerts to healthcare providers will provide greater situational awareness of the patterns of infection.

So, the next time you are given a wastebasket diagnosis of "viral syndrome," push your doctor a little harder. In 2018, we have countless diagnostic tests for viral infections available, many at the point-of-care, that too few physicians use. Not only will you be more satisfied with a real diagnosis, you may be spared an unnecessary course of antibiotics. You can also rest assured that having a name for your virus will help epidemiologists doing a very important job. While we have not yet technologically achieved the famed Tricorder of Star Trek fame that diagnoses everything with a sweep of the hand, using the tools we do have could be one of the keys to detecting the next pandemic virus early enough to intervene.

Amesh A. Adalja
Dr. Adalja is a Senior Scholar at the Johns Hopkins University Center for Health Security. His work is focused on emerging infectious disease, pandemic preparedness, and biosecurity. He has served on US government panels tasked with developing guidelines for the treatment of plague, botulism, and anthrax in mass casualty settings and the system of care for infectious disease emergencies, and as an external advisor to the New York City Health and Hospital Emergency Management Highly Infectious Disease training program, as well as on a FEMA working group on nuclear disaster recovery. Dr. Adalja is an Associate Editor of the journal Health Security. He was a coeditor of the volume Global Catastrophic Biological Risks, a contributing author for the Handbook of Bioterrorism and Disaster Medicine, the Emergency Medicine CorePendium, Clinical Microbiology Made Ridiculously Simple, UpToDate’s section on biological terrorism, and a NATO volume on bioterrorism. He has also published in such journals as the New England Journal of Medicine, the Journal of Infectious Diseases, Clinical Infectious Diseases, Emerging Infectious Diseases, and the Annals of Emergency Medicine. He is a board-certified physician in internal medicine, emergency medicine, infectious diseases, and critical care medicine. Follow him on Twitter: @AmeshAA
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Hand-counting bacteriophage plaques during a titer test.

(© borzywoj/Fotolia)


In my hometown of Pittsburgh, it is not uncommon to read about cutting-edge medical breakthroughs, because Pittsburgh is the home of many innovations in medical science, from the polio vaccine to pioneering organ transplantation. However, medical headlines from Pittsburgh last November weren't heralding a new discovery for once. They were carrying a plea—for a virus.

Phages are weapons of bacterial destruction, but despite recognition of their therapeutic potential for over 100 years, there are zero phage products commercially available to medicine in the United States.

Specifically, a bacteria-killing virus that could attack and control a certain highly drug-resistant bacterial infection ravaging the newly transplanted lungs of a 25-year-old woman named Mallory Smith. The culprit bacteria, Burkholderia cepacia, is a notoriously vicious bacterium that preys on patients with cystic fibrosis who, throughout their life, are exposed to course after course of antibiotics, often fostering a population of highly resistant bacteria that can become too formidable for modern medicine to combat.

What Smith and her physicians desperately needed was a tool that would move beyond failed courses of antibiotics. What they sought was called a bacteriophage. These are naturally occurring ubiquitous viruses that target not humans, but bacteria. The world literally teems with "phages" and one cannot take a bite or drink of anything without encountering them. These weapons of bacterial destruction are exquisitely evolved to target bacteria and, as such, are not harmful to humans. However, despite recognition of their therapeutic potential for over 100 years, there are zero bacteriophage products commercially available to medicine in the United States, at a time when antibiotic resistance is arguably our most pressing public health crisis. Just this week, a new study was published in the Proceedings of the National Academy of Sciences detailing the global scope of the problem.

Why Were These Promising Tools Forgotten?

Phages weren't always relegated to this status. In fact, in the early 20th century phages could be found on American drug store shelves and were used for a variety of ailments. However, the path-breaking discovery and development of antimicrobials agents such as the sulfa drugs and, later the antibiotic penicillin, supplanted the world of phage therapeutics in the United States and many other places.

Fortunately, phage therapy never fully disappeared, and research and clinical use continued in Eastern European nations such as Georgia and Poland.

The antibiotic age revolutionized medicine in a way that arguably no other innovation has. Not only did antibiotics tame many once-deadly infectious diseases, but they made much of modern medicine – from cancer chemotherapy to organ transplantation to joint replacement – possible. Antibiotics, unlike the exquisitely evolved bacteriophage, possessed a broader spectrum of activity and were active against a range of bacteria. This non-specificity facilitated antibiotic use without the need for a specific diagnosis. A physician does not need to know the specific bacterial genus and species causing, for example, a skin infection or pneumonia, but can select an antibiotic that covers the likely culprits and use it empirically, fully expecting the infection to be controlled. Unfortunately, this non-specificity engendered the overuse of antibiotics whose consequences we are now suffering. A bacteriophage, on the other hand, will work against one specific bacterial species and is evolved for just that role.

Phages to the Rescue

As the march of antibiotic resistance has predictably continued since the dawn of the antibiotic age, the prospect of resurrecting phage therapy has been increasingly viewed as one solution. Fortunately, phage therapy never fully disappeared, and research and clinical use continued in Eastern European nations such as Georgia and Poland. However, much of that experience has remained opaque to the medical community at large and questions about dosage, toxicity, efficacy, and method of delivery left many questions without full answers.

Though real questions remained regarding phage use, dire circumstances of prolific antibiotic resistance necessitated their use in the U.S. in two prominent instances involving life-threatening infections. The first case involved an Acinetobacter baumanii infection of the pancreas in a San Diego man in which phages were administered intravenously in 2016. The other case, also in 2016, involved the instillation of phages, fished out of a pond, into the chest cavity of man with a Pseudmonas aeruginosa infection of a prosthetic graft of the aorta. Both cases were successful and were what fueled the Pittsburgh-based plea for Burkholderia phages.

The phages you begin with may not be the ones you end up with, as Darwinian evolutionary pressures will alter the phage in order to keep up with the ongoing evolution of its bacterial target.

How Phages Differ from Other Medical Products

It might seem surprising that in light of the urgent need for new treatments for drug-resistant infections, the pharmaceutical armamentarium is not teeming with phages like a backyard pond. However, phages have been difficult to fit into the current regulatory framework that operates in most developed countries such as the U.S. because of their unique characteristics.

Phages are not one homogenous product like a tablet of penicillin, but a cocktail of viruses that change and evolve as they replicate. The phages you begin with may not be the ones you end up with, as Darwinian evolutionary pressures will alter the phage in order to keep up with the ongoing evolution of its bacterial target. The cocktail may not just contain one specific phage, but a range of phages that all target some specific bacteria in order to increase efficacy. These phage cocktails might also need adjusting to keep pace with bacterial resistance. Additionally, the concentration of phage in a human body after administration is not so easy to predict as phage numbers will rise and fall based on the number of target bacteria that are present.

All of these characteristics make phages very unique when viewed through a regulatory lens, and necessitate the creation of new methods to evaluate them, given that regulatory approval is required. Using phages in the U.S. now requires FDA permission through an investigational new drug application, which can be expedited during an emergency situation. FDA scientists are actively involved in understanding the best means to evaluate bacteriophage therapy and several companies are in early-stage development, though no major clinical trials in the U.S. are currently underway.

One FDA-approved application of phages has seen them used on food products at delis and even in slaughterhouses to diminish the quantity of bacteria on certain meat products.

Would That Humans Were As Lucky As Bologna

Because of the regulatory difficulties with human-use approval, some phage companies have taken another route to develop phage products: food safety. Food safety is a major public health endeavor, and keeping food that people consume safe from E.coli, Listeria, and Salmonella, for example, are rightfully major priorities of industry. One FDA-approved application of phages has seen them used on food products at delis and even in slaughterhouses to diminish the quantity of bacteria on certain meat products.

This use, unlike that for human therapeutic purposes, has found success with regulators: phages, not surprisingly, have been granted the "generally regarded as safe (GRAS)" designation.

A Phage Directory

Tragically Mallory Smith succumbed to her infection despite getting a dose of phages culled from sludge in the Philippines and Fiji. However, her death and last-minute crusade to obtain phages has prompted the call for a phage directory. This directory could catalog the various phages being studied and the particular bacteria they target. Such a searchable index will facilitate the rapid identification and – hopefully – delivery of phages to patients.

If phage therapy is to move from a last-ditch emergency measure to a routine tool for infectious disease physicians, it will be essential that the hurdles they face are eliminated.

Moving Beyond Antibiotics

As we move increasingly toward a post-antibiotic age in infectious disease, moving outside of the traditional paradigm of broad-spectrum antibiotics to non-traditional therapeutics such as bacteriophages and other novel products will become increasingly necessary. Already, clinical trials are underway in various populations, including a major trial in European burn patients.

It is important to understand that there are important scientific and therapeutic questions regarding dose, route of administration and other related questions that need to be addressed before phage use becomes more routine, and it is only through clinical trials conducted with the hope of eventual commercialization that these answers will be found. If phage therapy is to move from a last-ditch emergency measure to a routine tool for infectious disease physicians, it will be essential that the hurdles they face are eliminated.

Amesh A. Adalja
Dr. Adalja is a Senior Scholar at the Johns Hopkins University Center for Health Security. His work is focused on emerging infectious disease, pandemic preparedness, and biosecurity. He has served on US government panels tasked with developing guidelines for the treatment of plague, botulism, and anthrax in mass casualty settings and the system of care for infectious disease emergencies, and as an external advisor to the New York City Health and Hospital Emergency Management Highly Infectious Disease training program, as well as on a FEMA working group on nuclear disaster recovery. Dr. Adalja is an Associate Editor of the journal Health Security. He was a coeditor of the volume Global Catastrophic Biological Risks, a contributing author for the Handbook of Bioterrorism and Disaster Medicine, the Emergency Medicine CorePendium, Clinical Microbiology Made Ridiculously Simple, UpToDate’s section on biological terrorism, and a NATO volume on bioterrorism. He has also published in such journals as the New England Journal of Medicine, the Journal of Infectious Diseases, Clinical Infectious Diseases, Emerging Infectious Diseases, and the Annals of Emergency Medicine. He is a board-certified physician in internal medicine, emergency medicine, infectious diseases, and critical care medicine. Follow him on Twitter: @AmeshAA