Type: Prelims Only

A new study from Wuhan has studied the role of T-Cell Immunity against prolonged and sever COVID-19.

What are T-Cells?

• Like B cells, which produce antibodies, T cells are central players in the immune response to viral infection.
• For your immune system to fight off any kind of invader, such as a virus, you need a kind of white blood cell called a B cell, which makes antibodies, and a similar-looking white blood cell called a T cell.
• T cells can play different roles altogether.
• They can act as “killer cells”, attacking cells which have been infected with a virus or another kind of pathogen, or they can act as “helper cells” by supporting B cells to produce antibodies.

How do they function?

• Alongside antibodies, the immune system produces a battalion of T cells that can target viruses.
• Some of these, known as killer T cells (or CD8⁺ T cells), seek out and destroy cells that are infected with the virus.
• Others, called helper T cells (or CD4⁺ T cells) are important for various immune functions, including stimulating the production of antibodies and killer T cells.
• T cells do not prevent infection, because they kick into action only after a virus has infiltrated the body. But they are important for clearing an infection that has already started.
• In the case of COVID-19, killer T cells could mean the difference between a mild infection and a severe one that requires hospital treatment.

What did the latest research find?

• The researchers found that neutralising antibodies were detectable even 12 months after infection in “most individuals”.
• It remained stable 6-12 months after initial infection in people younger than 60 years.
• The researchers found that “multifunctional T cell responses were detected for all SARS-CoV-2 viral proteins tested”.
• And most importantly, the magnitude of T cell responses did not show any difference immaterial of how severe the disease was.
• While the ability of antibodies to neutralise was nearly absent against the Beta variant, it was reduced in the case of the Delta variant.

Neutralizing antibodies

• SARS-CoV-2-specific neutralising antibody and T cell responses were retained 12 months after initial infection.
• Neutralising antibodies to the D614G, Beta, and Delta were reduced compared with those for the original strain, and were diminished in general.
• Memory T cell responses to the original strain were not disrupted by new variants.
• The findings show that robust antibody and T cell immunity against SARS-CoV-2 is present in majority of recovered patients 12 months after moderate-to-critical infection.

Robustness of antibodies

• The study reveals the durability and robustness of the T cell responses against variants, including Delta, even after one year of infection.
• Most importantly, the robust and longstanding T cell responses were seen in people who have not been reinfected or vaccinated.
• This would mean even in the absence of vaccination, a person who has been infected by the virus even one year ago would have robust immune responses.
• It would offer protection against disease progressing to a severe form requiring hospitalization.

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Russia said that it had unleashed hypersonic missiles against an arms depot in Ukraine, the first use of the next-generation weapons in combat.

Kinzhal Missile

• It is a nuclear-capable air-launched ballistic missile that flies at 10 times the speed of sound and can overcome air-defence systems. Kinzhal means ‘dagger’.
• The missile has a range of approximately 1,500-2,000km and can carry a nuclear payload or conventional payload of 480 kg.
• The Kinzhal was one of an array of new weapons Russian President Vladimir Putin unveiled in his state-of-the-nation address in 2018. Putin had termed Kinzhal as “an ideal weapon”.
• This is the first time that Russia has admitted to using the high-precision weapon in combat.
• Following launch, the Kinzhal rapidly accelerates to Mach 4 (4,900 km/h), and may reach speeds of up to Mach 10 (12,350 km/hr).

What is a hypersonic weapon?

• They are normally defined as fast, low-flying, and highly manoeuvrable weapons designed to be too quick and agile for traditional missile defence systems to detect in time, according to Bloomberg.
• Unlike ballistic missiles, hypersonic weapons don’t follow a predetermined, arched trajectory and can maneuver on the way to their destination.
• The term “hypersonic” describes any speed faster than five times that of sound, which is roughly 760 miles (1,220 kilometers) per hour at sea level.
• At hypersonic speeds, the air molecules around the flight vehicle start to change, breaking apart or gaining a charge in a process called ionization.
• This subjects the hypersonic vehicle to “tremendous” stresses as it pushes through the atmosphere.

Types of hypersonic weapons

• There are two main types of these weapons — glide vehicles and cruise missiles.
• Most of the attention is focused on the former, which are launched from a rocket before gliding to their target, because of the challenges of achieving hypersonic propulsion of missiles.
• The missiles have engines called scramjets that use the air’s oxygen and produce thrust during their flight, allowing them to cruise at a steady speed and altitude.

Who has these weapons?

• US, China and Russia have the most advanced capabilities.
• Several other countries are investigating the technology, including India, Japan, Australia, France, Germany and North Korea, which claims to have tested a hypersonic missile.
• In fact, India is also closing in on having such weapons in its arsenal.
• Last year, India successfully tested its hypersonic technology demonstrator vehicle (HSTDV), powered by a scramjet engine.
• The HSTDV will serve as a crucial building block in the development of long-range hypersonic weapons, which will take at least another four to five years to become a reality.

Back2Basics: Types of Missiles

(1) Subsonic missiles

• They travel at a rate slower than the speed of sound.
• Most well-known missiles, such as the US Tomahawk cruise missile, the French Exocet, and the Indian Nirbhay, fall into this category.
• These travel at about Mach-0.9 (705 mph), and are slower and easier to intercept, but they continue to play a significant role in modern battlefields.
• They significantly less expensive to produce because the technological challenges have already been overcome and mastered.
• Due to their low speed and small size, subsonic missiles provide an additional layer of strategic value.

(2) Supersonic missiles

• They are the one that travels faster than the speed of sound (Mach 1) but not faster than Mach-3.
• Most supersonic missiles travel at speeds ranging from Mach-2 to Mach-3, or up to 2,300 mph.
• The Indian/Russian BrahMos, currently the fastest operational supersonic missile capable of speeds of around 2,100–2,300 mph, is the most well-known supersonic missile.

(3) Hypersonic Missiles

Explained above