Why Scientists Are Puzzled By This Virus

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Why Scientists Are Puzzled By This Virus You’ve got trillions of viruses inside you – right now! But these aren’t the viruses you fear. Some of them are your body’s secret protectors, keeping deadly bacteria in check and even killing cancer cells. But what happens when they turn against you? Let's look at the wild world of the human virome.

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00:00Very recently, scientists discovered that your body is teeming with trillions of the

00:04most bizarre viruses.

00:06These viruses are not your enemies, but critical to your health, protecting you from disease,

00:11maybe even killing cancer.

00:13A new frontier of science, something truly new that we're only just beginning to understand.

00:19Let's dive into the wild world of the human virome.

00:23You are an ecosystem.

00:25You're a living, breathing ecosystem, made of up to 40 trillion cells.

00:32This metropolis of flesh is home to the human microbiome, another 40 trillion bacteria that

00:38have a contract with your body.

00:40They get to live here, and in return, they break down your meals.

00:44They synthesize vitamins in your gut, neutralize acid in your mouth, help balance your immune

00:49system, and they take up space, preventing harmful bacteria from getting in.

00:55This is a fragile balance.

00:57Bacteria really only look out for themselves, multiplying and testing their boundaries.

01:02To keep their numbers in check, your body's ecosystem needs a group of deadly predators,

01:07viruses, at least 10 trillion.

01:09They're literally everywhere in your body, tens of thousands of different species.

01:14At least a few trillion live in your gut, where also most of your resident bacteria are.

01:19At least 18 billion on your skin, 100 million in each drop of your saliva, dozens of millions

01:25in your urinary tract.

01:26Even in a single drop of the cerebrospinal fluid surrounding your nerves and brain, researchers

01:32found up to 10,000 viruses.

01:34While this sounds like a horrible idea at first, at least in the gut, around 97% of them are

01:40bacteriophages, or phages, bizarre creatures that are specialized in hunting down and killing

01:45resident bacteria and are not able to infect your cells.

01:48Instead, they kill trillions of bacteria every single day.

01:52Together, these viruses make up the human virome, a symbiotic virus ecosystem that's completely

01:58unique to you and that seems to be crucial for your health.

02:02Let's get to know them and see how they support you and what happens if things go wrong.

02:07The silent mass murderers of your body.

02:10Inside your gut, a stealthy lambda phage floats through the buzzing crowds of bacteria looking

02:15for a victim.

02:17It has six legs, a long, thin body, and a big head, made of geometric shapes filled with

02:22genetic material.

02:23Each species is specialized in hunting one specific species of bacteria and ignores all

02:28others.

02:29Lambda is looking for Asherichia coli.

02:32This versatile bacteria is numerous in your gut, usually a good boy synthesizing vitamins

02:37for you.

02:38But it also has a dark side.

02:40Some of them would much rather live inside your flesh and feast on your resources.

02:44If there are too many or if they manage to invade your tissue, they can cause serious diseases.

02:49So one of the most important jobs of the virome is to control the numbers of different bacteria

02:54populations by killing them.

02:57Lambda has found a victim.

02:59Spider-like legs get hold of a bacteria and grip it hard.

03:03Like an angry syringe, it violently rams its sharp bottom into the victim's body and releases

03:08its DNA.

03:09Once inside, the proteins disable the defenses of the bacterium.

03:13It is now a factory under new management.

03:15It is forced to build new viruses until the victim is filled up and bursts open, releasing

03:20a horde of fresh lambda viruses.

03:23But its goal is not genocide.

03:26Phages need a healthy population of bacteria to survive.

03:29So sometimes they choose a way more sinister tactic.

03:32Instead of killing their victim, the virus integrates its DNA into the genome of the bacteria

03:37and goes to sleep.

03:39When the bacteria multiplies, the virus DNA is multiplied too, until one day the viral

03:44DNA reawakens and suddenly decides to kill its unsuspecting victim.

03:49And here things become exciting.

03:51Your virome also needs you to thrive.

03:54It's in its best interest that you're healthy.

03:56So some viruses inject genes into bacteria that actively make them support your body.

04:02Some force their bacteria hosts to support your gut's mucus layer, break down complex carbohydrates

04:07from your food more efficiently, creating substances that protect against inflammation.

04:12And they alter what signals bacteria send to your immune cells.

04:15Basically, they're letting them know, we have things under control, you can chill out.

04:20This may prevent allergic reactions or even protect you against autoimmune diseases.

04:26But of course, there's also a dark side to this story.

04:29Some viruses don't care about our health.

04:32Instead of helping, they turn harmless bacteria into deadly monsters.

04:37When viruses turn bacteria into killers.

04:41Some species of bacteriophage carry dangerous genes for toxic substances.

04:45When they take over their hosts, they can integrate into the genetic code of the bacteria, where they

04:50lay as a deadly gift.

04:52Like the case of the Vibrio cholerae and the CTX-phi bacteriophage hunting them.

04:57Most strains of the cholerae bacteria are harmless, and billions of them may live in your gut right

05:02now.

05:03When CTX-phi infect the bacteria, they gift them the genes for the cholera toxin, which

05:08permanently becomes part of their genetic lineage forever.

05:12It's like handing a house cat a shotgun.

05:15Vibrio cholerae shower these toxins at the cells lining your gut, making them sick.

05:20They vomit large amounts of salt, which pulls out a flood of water into your intestines.

05:24This causes explosive diarrhea and vomiting, draining your body of fluid.

05:28If untreated, about half of patients die.

05:31But for the phage and bacteria, this is great.

05:34They're carried out of the body to infect more humans, spreading and multiplying further.

05:40This strain of Vibrio cholerae is now a dangerous enemy of humanity thanks to this virus.

05:45Or the bacteria Staphylococcus aureus, which is hunted by the phage with the amazing name

05:50Phi-SA-3-MS.

05:52Usually the bacteria is mostly harmless and lives on your skin and inside your nose.

05:57It doesn't do anything useful per se.

05:59Its main job is to take up space, making it harder for hostile bacteria to colonize your

06:04body.

06:05But Phi-SA-3-MS can change this quickly.

06:08It carries multiple dangerous genes, like giving account flamethrowers and grenades.

06:13If such a modified Staphylococcus aureus bacteria gets into your body through a tiny cut, it becomes

06:19extremely dangerous.

06:20One of its new weapons are super antigens, which basically is like injecting your immune

06:25cells with cocaine.

06:26The toxin completely breaks your carefully fine-tuned immune system.

06:30It activates all of your T-cells all at once and makes them flip out.

06:35They release a tsunami of cytokines, activating all of your defenses at once.

06:39The infection is flooded with cells that can't fight the bacteria and cause heavy inflammation.

06:45Your broken and confused immune cells have a really hard time fighting Staphylococcus

06:50aureus, which now invades, penetrating deep into your tissue.

06:54Your body is trying to seal the wounds and isolate the invader, but another new weapon it

06:58gained has the ability to just dissolve the barriers and penetrate even deeper.

07:03Before the onset of antibiotics, an infection with Staphylococcus aureus was very deadly,

07:07and we have Phi-SA3-MS to thank for making it even deadlier.

07:12But the viruses of our virome may also directly save your life by killing cancer.

07:19Cancer-killing viruses Oncolytic viruses specialize in hunting

07:23and killing cancer, like the Newcastle disease virus or the Rheovirus, who mostly ignore your

07:29healthy cells and instead hunt down tumors.

07:32Cancer cells are broken mutants that evolve various ways to hide and fight back against

07:36your immune system.

07:38But as they get better at this, they get worse at other things, like fighting back viruses.

07:43A weakness to be exploited.

07:46Oncolytic viruses target the specific adaptations of cancer cells, hitting them where they are

07:50not ready to be hit.

07:52And worse for these cells, since their internal machinery is compromised, they can't defend themselves.

07:57They are taken over and turned into virus production factories.

08:01Eventually, the new viruses leave the cancer cell, often killing it, and carry on infecting

08:06other cancer cells nearby.

08:08This death and destruction is not subtle, and one side effect is that it attracts immune

08:12cells that immediately begin attacking the tumor with full force.

08:17What's even more impressive, these viruses seem to disrupt the artificial environment that

08:21tumors create to keep your immune system at bay.

08:24Oncolytic viruses are like infiltrators in a city at siege, opening the gates while killing

08:29defenders left and right, helping your immune cells to win the fight.

08:34In 2024, we don't know yet to what degree oncolytic viruses are part of your virome or more of

08:40a happy accident, but they seem to go well together with chemotherapy or radiation.

08:44Eventually, they may become an important new tool to enable us to eliminate cancer and save

08:50millions of lives.

08:52We don't know what we'll learn in the next few years, but we now know that there are

08:55trillions of potential allies within us, killing and manipulating for better or worse.

09:02What an exciting time to be alive!

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