Tuesday, February 26, 2019

Secret Science Club Post-Lecture Recap: Sneaky Ebola, Sneakier Antibodies

Last night, I headed down the the beautiful Bell House, in the Gowanus section of Brooklyn, for this month's Secret Science Club lecture featuring microbiologist and immunologist Dr Kartik Chandran of the Albert Einstein College of Medicine. The topic of Dr Chandran's lecture was 'Unraveling and Counteracting the Infection Strategies of Emerging Viruses', with a specific focus on the Ebola virus. Dr Chandran researches how emerging viruses invade cells, and how medical practitioners could use 'jujutsu flips' to counteract their takeover strategies. Viruses such as Ebola emerge for a variety of reasons: clear-cutting forests, herding livestock which can allow viruses to change hosts, and climate change. Viruses can jump from various animal hosts into human populations. It takes a long time to figure out strategies to combat viruses when they jump to humans.

The Ebola virus was named after the Ebola River in the Democratic Republic of Congo. The Ebola virus was discovered in 1976 in a remote missionary station run by Belgian nuns. The events behind the emergence of the Ebola virus were the topic of Richard Preston's bestselling thriller The Hot Zone, which will be dramatized as a National Geographic miniseries which Dr Chandran ruefully predicted will probably be 'a hot mess'. The Ebola virus is lethal but rare, and strikes in remote places. For a long time, charities such as the Gates Foundation did not consider Ebola to be a major healthcare problem compared to infant mortality and malaria. That changed with the 2013-2016 outbreak of Ebola in West Africa, which set healthcare in the region back by a decade. A lot of healthcare personnel died in that outbreak. Currently, there is an outbreak of Ebola in the Democratic Republic of Congo, in an active warzone. A lot was learned during the West African outbreak- there is an urgent need for vaccines, but where do we begin?

The Ebola virus is a filovirus, a virus that forms a filament, a single strand of RNA. Viruses can be likened to molecular machine assemblies, they reproduce by taking over cells and turning them into virus factories. Viruses have an 'invasion machine' which gets them into cell cytoplasm and a 'payload', a genetic code which turns the cell into a virus factory. Dr Chandran is primarily interested in the delivery system of the virus, which is a glycoprotein. This large molecule sticks to the cell and enters the cell's lysosome in order to reproduce more viruses.

Dr Chandran posed a darkly jocular question: how do we study viruses without losing grad students? The invasion mechanism of Ebola can be attached to the vesicular stomatitis virus, a cattle pathogen which only causes minor illness in humans. In effect, this altered VSV is a 'sheep in wolf's clothing'. This invasion mechanism could then be used to develop antibodies to fight the Ebola virus. This therapy, named ZMapp, was dubbed by Newsweek magazine 'The Secret Serum that Could Cure Ebola'. Antibodies are 'tailor made' by the immune system to bind to viruses. Viruses evolve rapidly, though, and Dr Chandran compared harnessing antibodies to pin down the Ebola virus to burly wrestlers trying to pin down agile ballet dancers.

Dr Kent Brantly, an American doctor infected by Ebola while serving in Liberia, was treated with ZMapp. Dr Ada Igonoh of Nigeria contracted Ebola virus, was left for dead, but survived the infection (as an aside, I have to mention Nigeria's Dr Ameyo Adadevoh who quarantined Liberia's 'patient zero', containing the outbreak, and died of the disease). The ZMapp antibodies 'lasso' the Ebola virus' glycoprotein and targets it for destruction. The problem with ZMapp is that it only works on the Ebola Zaire strain (other strains are Bundibugyo, Sudan, Reston and Taï Forest). The Zaire strain is the most common Ebola strain, but epidemiologists cannot predict which strain of Ebola virus will jump out of nature.

Dr Chandran likened the interaction of viruses and antibodies to a lock and key- not all antibodies can be useful to all viruses. Viruses mutate to be resistant to antibodies- they 'bob and weave' so the antibodies can't bind. The search is on for a 'Rainbow Unicorn Antibody', an antibody which could recognize proteins that a virus cannot change and act on those proteins, effectively beating Ebola and other viruses at their own game. Viruses stick to certain receptors, they 'figure out' what sort of cells they need to affect. For example, the polio virus cannot bond to mouse cells unless the mouse receives the human receptor gene. Ebola has a 'homing beacon' on the lysosome, the NPC1 gene (Niemann-Pick, type C1). The NPC1 gene transports cholesterol from the lysosomes, and is present in eukaryotes from yeast to humans. Dr Chandran likened NPC1 to a janitor working in the basement who is coerced by the Ebola virus to allow a break-in. If the NPC1 gene can be knocked out, Ebola is ineffective at invading the cell. The NPC1 gene is rapidly evolving in 125 African bat species. Usually, 'housekeeping' genes such as NPC1 evolve slowly. It appears that bats are evolving to disallow Ebola's use of NPC1 as a receptor, which suggests that Ebola is a bat virus, new to primates. The most promising treatments for Ebola would target the virus' ability to dock with the NPC1 gene in human patients.

The Ebola virus glycoprotein uses a staged invasion strategy. Dr Chandran quipped that he is not a rocket scientist, but he likened the invasion strategy to a multi-staged rocket. The NPC1 gene is not located on the cell's surface, but is sequestered within the cell membrane. The virus must be 'eaten' by the cell, and once inside the lysosome, it 'takes off its disguise' and multiplies. All primates have the same NPC1 gene, it is the perfect site to put an antibody which can prevent the Ebola virus from docking in the lysosome. Combining antibodies increases their effectiveness, and one antibody, mAb-548, binds to the NPC1 gene better than the virus- it beats the virus every time. Other antibodies dock with the virus better than the NPC1 gene does. Combining antibodies blocks the binding sites of both virus and cell. Antibodies need to be in the right place at the right time- Ebola viruses can sneak into lysosomes without either antibody tagging along. Antibodies typically can only bind to one thing- there is an effort to develop antibodies with 'second arms' that can grab onto two sites. Such a 'two armed' antibody could bind to either the virus or the NPC1 gene. These bispecific antibodies were tested on mice infected with the Ebola Sudan strain, and two shots of the antibody were sufficient to protect the mice. Eventually, the virus was beat at its own game and mice could be protected from multiple Ebola strains.

Dr Chandran then shifted the subject of the lecture to the Rainbow Unicorn Antibody, a naturally occurring antibody which could work against all Ebola strains. Blood obtained from an Ebola survivor was tested, and the antibodies were 'gold that has to be fished out' of the sample. Memory B cells function as a library of everything than an individual has survived- if Ebola antibodies are sought, they must be fished out of these cells. The B cells are sequenced, the Ebola antibodies are obtained, and injected into yeast cells to produce additional antibodies. The yeast cells are then screened to obtain the desired gene sequences. The entire process takes about a month to complete. Using this technique, 350 antibodies were found from one Ebola survivor and twenty of them turned out to be 'Rainbow Unicorn Antibodies'. The task then is to make cocktails, starting with one antibody, then adding additional antibodies and testing them on monkeys. These cocktails are effective up to day seven of an infection.

In the field, administering medications is difficult, considering the protective gear that medical personnel need to wear, and the hot conditions that prevail in the regions where Ebola outbreaks occur. A intramuscular injection delivered cocktail would allow more people to be treated quickly. Such a cocktail is now being developed for human use, and it has the potential to be used to treat multiple viruses: filoviruses, hantaviruses, nairoviruses, pneumoviruses, alphaviruses, and flaviviruses.

Dr Chandran ended his lecture by mentioning his participation in an organization called the Prometheus Group, which was formed to transform human antibodies into antiviral treatments in three years. He likened the group's approach to 'jazz improvisation' to develop many tools to fight viral diseases.

The lecture was followed by a Q&A session. The first question concerned the unintended consequences of turning off the NPC1 gene... when the gene is turned off, cells can get clogged with cholesterol and cause neurological damage. This naturally occurs in individuals with Niemann-Pick Disease Type C. Turning off the NPC1 gene will cause cholesterol to accumulate over the course of several years, while Ebola can kill a patient in two weeks. Turning off one of two copies of the NPC1 gene can prevent Ebola infections while not leading to Niemann-Pick. Another question concerned the reasons why the West African Ebola outbreak died out- it was mainly due to quarantining patients and treating them with IV fluids. Individuals infected with Ebola must be isolated for 28 days in order to ensure the safety of others. Another question involved the lysosome... lysosome delivery systems are used by many viruses. Regarding the effects of different strains affecting different primates, it seems that crab-eating macaques are particularly vulnerable to the various Ebola virus strains. A question regarded Africa's genetic diversity, which is the greatest on the planet, and the possibility that it is a result from evolutionary responses to emerging viral outbreaks- the human genome contains a lot of genetic sequences from viruses. There was a question regarding the vulnerability of antibodies to viral mutation- if one antibody is involved, there is a good chance that the virus will evolve and thwart it, so multi-antibody cocktails are necessary. There was a question regarding using the same approach to combat HIV- therapies are under development, and it is possible that one will be available in the next two years or so.

Some bastard in the audience decided to ask a sociopolitical question- what is the role of conflict in Ebola outbreaks? The recent Ebola epidemics took place in regions wracked by civil war. Dr Chandran noted that conflict prevents responses by medical personnel, it destroys or degrades infrastructure, increases distrust of government. One necessary strategy to deal with outbreaks is to find influencers who can combat anti-medical social media memes, to convince people to get treatment. Trusted voices are needed to convince people to seek aid, not just voices from people in 'space suits'.

The last question concerned Dr Chandran's 'origin story', how did he end up studying Ebola. Dr Chandran indicated that he had been studying HIV early in his virology career, but was drawn to study Ebola by reading The Hot Zone. How's that for the power of books?

Once again, the Secret Science Club delivered the goods. Dr Chandran knocked it out of the park- he delivered an informative lecture on a topic which has been sensationalized by the media, conveying hard science fact in terms accessible to the layperson, discussing terrifying topics with just enough humor to leaven this heavy topic. I left the lecture more hopeful about humanity than I was when I entered. The 'good guys' are out there, and Dr Chandran is one of them. I also have a personal interest in Ebola, my brother Vin was deployed to Liberia in 2014 to build a medical infrastructure in the early days of the Ebola outbreak. It's good to know that scientists such as Dr Chandran are working to protect people who live in these 'hot zones', and people going to the hot zones to combat the disease, and other emergent diseases. Kudos to Dr Chandran, Dorian and Margaret, and the staff of the beautiful Bell House.

Here's a video on this topic by Dr Chandran, which showcases the fantastic imagery he displayed while he delivered his lecture. My recaps are mainly black-and-white, which isn't always up to the colorful, animated presentations utilized by the speakers:

Pour yourself a nice, refreshing beverage and soak in that SCIENCE!


mistah charley, ph.d. said...

there ARE good guys out there - the war between good and evil overlaps the war between knowledge and ignorance, and who knows what twists and turns the story will take?

as always, thanks for this interesting account

Big Bad Bald Bastard said...

Thanks, mistah charley. These recaps are my most important posts, so I try to put extra effort in them. I owe that to Margaret and Dorian, and the lecturers who appear onstage at the beautiful Bell House.

authorlink said...

This article is very good .check for lysosomes