Editorial 1 : New type of host defence against Zika, dengue viruses revealed
Context
The mere presence of a virus in a bodily fluid doesn’t mean it is transmitted via that route. A team of researchers have finally explained why viruses like Zika, dengue, and chikungunya are present in fluids like saliva and semen but don’t spread orally or sexually.
Viruses and their transmission
- Transmission is a crucial event in a virus’s life cycle, yet studying it has been very tricky. A virus that can’t transmit is of no consequence to anyone.
- Successful viruses have extraordinary adaptations selected through years of evolution to ensure they can jump to new hosts.
- Most human viruses achieve this by ensuring they are present in bodily fluids that contact the outer environment, and subsequently, a new host.
- Once inside the new host, a virus must be present at the correct location to infect new target cells.
- Viruses are usually highly selective in the cells they infect. This phenomenon, called tropism, occurs because most viruses have special proteins on their outer surface that make contact with a receptor on the host cell. Any cell-type that makes the receptor can be infected by the virus.
- For example, the receptor for HIV is a protein called CD4. Only cells that make the CD4 protein, such as T-cells and macrophages, can be infected by HIV.
- Similarly, SARS-CoV-2 uses a receptor called ACE2. Cells of the respiratory tract and some cardiovascular cells all express ACE2, and are target cells for SARS-CoV-2.
- HIV can’t infect respiratory cells, and SARS-CoV-2 can’t infect T-cells or macrophages.
- Viral transmission is an outcome of a chase inside the host: between the virus making copies of itself and the immune system trying to destroy the virus and infected cells.
- The virus must transmit before the immune system beats it or the host dies. One strategy viruses use to achieve this is by making proteins on the surface that have receptors on multiple cell-types.
- Such a strategy will allow them to infect different cell-types, allowing access to multiple body fluids, enabling faster transmission.
The PS receptor
- One such receptor is for a protein called phosphatidyl serine (PS).
- The PS protein is usually expressed by dying cells in the body, as a signal to the immune cells to destroy them.
- The immune cells express the PS receptor and fuse themselves with these cells, quietly destroying them.
- Viruses hijack this pathway with a process called apoptotic mimicry: by expressing the PS protein on their own surfaces, allowing them to infect the very cells that will destroy them.
- Since the PS receptor is expressed by many cells — apart from some cells of the immune system — the virus tends to be present in multiple compartments.
- Yet, the mere presence of a virus in a given compartment wouldn’t guarantee transmission from that route.
The body’s defence
- The body uses extracellular vesicles in these bodily fluids to inhibit viral infection.
- Vesicles are small structures enclosed by fat that a cell uses to transport substances from one part of the cell to another.
- When they are secreted outside the cell, they’re called extracellular vesicles.
- The researchers discovered that these extracellular vesicles are abundant in saliva and semen and contain the same PS proteins on their surface that viruses like Zika use for infection.
- The team also discovered that the concentration of these extracellular vesicles that contain PS is low in the blood and high in saliva and semen.
- The PS-containing vesicles compete for the same receptors the viruses use for entry, thus crowding the latter out and preventing an infection.
Conclusion
The discovery of PS-coated vesicles for immunity represents a novel type of host defence against viral infection. While it is too early to speculate on potential therapeutic applications from this discovery, it opens up avenues for further research.
Editorial 2 : Toss out the junk food, bring back the healthy food plate
Introduction
India, like in many other countries, is undergoing a major “nutrition transition”. In what characterises rapidly changing dietary patterns, there is a significant shift away from traditional diets, which were high in fibre and comprised mostly whole foods, to more western-style diets, which are processed and high in calories.
The surge in junk food
- The change has coincided with rapid economic progress and urbanisation along with a surge in the consumption of packaged and processed foods (popularly called “junk foods”)
- These foods are nutritionally low in vitamins, minerals, fibre but are high in calories, fats, salt, sugar, and innumerable preservatives.
- Categorised as high in fats, salts and sugars (HFSS) foods, scientific evidence shows how junk food has been medically found to weaken the body’s defences against infection, increase blood pressure, lead to a spike in blood sugar, cause weight gain, and also contribute to increased risk of cancer.
- The Indian Council of Medical Research (ICMR) study published in 2023 estimates that in India the prevalence of metabolic disorders is glaringly high where 11% has diabetes, 35% is hypertensive and almost 40% are suffering from abdominal obesity.
Court’s concern
- A ruling by the Supreme Court of India, in 2013, stated that that any food article which is hazardous or injurious to public health is a potential danger to the fundamental right to life guaranteed under Article 21 of the Constitution of India.
- Recognising the need to promote people’s health and well-being, the Government of India has prioritised the promotion of healthy foods and an active lifestyle through its initiatives such as Eat Right India, the Fit India Movement, and Prime Minister’s Overarching Scheme for Holistic Nutrition (Poshan) 2.0.
- As children are more exposed to the advertising of unhealthy foods, the Food Safety and Standards Authority of India (FSSAI) released the Food Safety and Standards (Safe food and balanced diets for children in school) Regulations, 2020, restricting the sale of HFSS in school canteens/mess premises/hostel kitchens, or within 50 metres of the school campus.
- Recently, the National Commission for Protection of Child Rights also issued notice to a health drink giant to evaluate and withdraw all misleading advertisements, packaging and labels that brand the product as a “health drink”, citing the product’s high sugar content that can adversely impact the health of children.
- Despite a policy intention to provide a safe food environment, there is still much work that needs to be done in ensuring effective implementation of interventions that can have an impact on the consumption of junk foods.
Formulating a clear definition
- First, a good starting point for the government is to protect growing children from the harmful impact of junk foods.
- Second, Front-of-Pack Labelling (FOPL) appears to be a low-hanging fruit which can enable consumers to make informed choices about what foods they choose to eat. The nutrition labelling practice that draws one’s attention with clear and understandable signals can help you make an informed food choice.
- Third, policies can also be developed to facilitate the positive subsidies for healthy foods such as whole foods, millets, fruits and vegetables that will improve their availability, affordability, and thus greater consumption in rural and urban areas.
- Fourth, in addition to the policies, a behavioural change campaign targeting children and young adults alike can play a critical role in helping youth adopt healthy dietary habits and mindful eating practices.
Way forward
It is critical to acknowledge the urgency of switching to healthier diets and creating public demand, or, as Prime Minister Narendra Modi calls it, a “Jan Andolan” or people’s movement, for healthy and nutritionally diverse diets.