“Virus” – the word alone can send shivers down your spine. We associate it with pandemics, suffering, and global lockdowns. But what if we told you that some viruses help you stay healthy? Learning about viruses can transform people’s opinion on what once seemed like straightforward agents of disease and death, from the origin of life to technologies that preserve it.
What Is the Human Virome?
Welcome to the emerging world of the human virome, a hidden universe of viruses that live in and on us, quietly shaping our immune system, mental health, and metabolism. While bacteria often steal the spotlight through probiotics and gut health campaigns, viruses got their due credit, not as invaders, but as potential partners in health.
All the viruses in the body are collectively known as human viromes. It includes: – Bacteriophages – viruses that infect bacteria, helping control harmful bacterial overgrowth. Eukaryotic viruses are those that infect human cells (some harmless, others not). Endogenous retroviruses – ancient viral DNA integrated into our genes over millions of years.
Training the Immune System
Many viruses play a crucial role in educating our immune system. From birth, exposure to various viruses helps fine-tune immune responses, teaching the body when to fight and tolerate. For example, when a virus attacks our immune system, it responds by providing adaptive immunity (either kills infected cells or produces antibodies that destroy the virus). After the infection is clear, it will train the memory cells in the system to respond more strongly and rapidly if the viruses return.
Viruses as Microbiome Architects
Bacteriophages, viruses that infect bacteria, are the unsung heroes of your gut health. These tiny regulators help keep bacterial populations in check, preventing harmful species from taking over. By targeting dominant species, they create spaces for less competitive species. For example, infection of antibiotic-treated mice with a single eukaryotic virus (murine norovirus) protected the mice against antibiotic-associated intestinal injury and bacterial infection. These finding highlights the ability of eukaryotic viruses to shape mucosal immunity.
Can Viruses Be the Next Probiotics?
Probiotics are generally beneficial bacteria which confer health benefits to the host. For example, the strain Lactobacillus rhamnosus is found in yoghurt, which is effective for antibiotic-related diarrhoea in children and adults. Similarly, the concept of “viral probiotics” is gaining ground. If we can isolate beneficial viruses, we could one day supplement them to promote gut and immune health.
Viruses respond to antibiotic resistance
James Collins and Lu (Boston University) showed that phages can break up biofilm, stubborn webs of bacteria and extracellular matrix that immune cells and antibiotics have difficulty penetrating. Identifying the bacterium causing a patient’s illness and finding a phage that kills it could wipe out the troublemaker and leave beneficial bacteria unharmed.
Viruses and the Mind
The gut “virome” is colonised starting at birth, shaped by diet and unique to each person. While the data is early, there’s research suggesting that alternation in the gut virome may impact the brain. Some research has found that people with increased gut concentration of Caudovirales phages (a diverse group of phages abundant in the gut) performed better in processing and verbal memory. Recent research has begun linking viruses to mental health.
Virotherapy
In this technique, genetically engineered oncolytic viruses are used as an immunotherapeutic method. It’s basically used in cancer treatment to selectively target and kill cancer cells while sparing healthy cells. To date, scientists have made a number of preclinical attempts and clinical trials of both naturally occurring OVs (e.g., reovirus and vesicular stomatitis virus) and genetically engineered OVs (e.g., adenovirus, vaccinia virus and herpesvirus), with some encouraging data.
Some researchers are interested in viruses that infect humans without causing disease and fend off more dangerous viruses and bacteria. Like the hepatitis A virus can protect against hepatitis C, and researchers have used lymphoma-associated viruses to cure type 1 diabetes in mice.
Viruses in gene therapy
Gene therapy aims to treat or prevent diseases by modifying a patient’s genes. The new gene is delivered to the patient’s cells using a vector, which can be a virus. Viruses are naturally adept at delivering materials into cells. This ability is harnessed in gene therapy, where viruses are modified to act as vectors or carriers. Adeno-associated viruses are a popular choice, but other viruses, like lentiviruses and retroviruses, are also popular.
When Things Go Wrong
Of course, it’s not all good news. Already our body has a lot of latent infections (viruses hiding from the immune system and won’t cause any symptoms or diseases with no active replication) with specific viruses (Herpes Simplex virus, varicella zoster virus, Epstein-Barr virus and many more).
Under certain conditions, like weakened immune system, organ transplantation (using an immune suppressor) and autoimmune disorders, people can have disturbed virome conditions, which can lead to infections and chronic diseases like cancer. As we know, in space missions, thorough disinfection happens, but astronauts face a compromised immune system, increasing their susceptibility to viral infections like herpes infection, varicella zoster and many more. Like in the Apollo 7 mission, astronauts had a cold outbreak, and in the International Space Station, reactivation of the herpes viruses was seen.
It’s time to rewrite the viral narrative. Yes, some viruses are deadly. But many are just part of who we are, silent contributors to our survival and health. Studying viruses isn’t easy. Many of them can’t be cultured in labs, and virome analysis requires powerful bioinformatics tools.
(Jaishi is currently a Research scholar in Dr Ritu Gaur’s lab (virology), South Asian University, New Delhi. They have been working on finding an alternative to HIV treatment and Srihari is an MSc Biotechnology student at South Asian University, New Delhi. With a passion for unravelling the mysteries of host-pathogen interactions, he aims to translate science beyond the lab to make a real impact on society.)
