How do antibodies target corona virus?

People who have recovered from mild corona virus infections produce antibodies that target three different parts of the virus's spike protein that it uses to latch on to human cells

  • A National Institutes of Health-funded study, published recently in the journal Science, offers the most detailed picture yet of the array of antibodies against SARS-CoV-2 found in people who've fully recovered from mild cases of corona virus.
  • Most studies of natural antibodies that block corona virus have focussed on those that target a specific portion of the spike protein known as the receptor-binding domain (RBD). The RBD is the portion of the spike that attaches directly to human cells. As a result, antibodies explicitly targeting the RBD are an excellent place to begin searching for antibodies capable of fighting the virus.
  • However, researchers at The University of Texas at Austin found that most antibodies target other portions of the spike protein than the RBD. The study led by Gregory Ippolito and Jason Lavinder, likens the spike protein to an umbrella, with the RBD at the tip of the "canopy." While some antibodies bind to the RBD, many others target the protein's canopy, known as the N-terminal domain (NTD).
  • The team also found that about 40 % of antibodies target yet another portion of the spike called the S2 subunit. Additionally, the S2 subunit could make an ideal target for a possible pan-corona virus vaccine since fewer mutations exist at this portion of the spike.
  • The study will prove helpful in designing vaccine booster shots or future vaccines tailored to fight coronavirus variants of concern.

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What is dengue and what are its causes?

Hospitals in Haryana, Kerala, Punjab, Rajasthan, Tamil Nadu, Uttar Pradesh, Uttarakhand, Delhi, and Jammu and Kashmir are witnessing a surge in dengue cases with the number of cases reported exceeding one lakh. The Union health ministry has sent teams of experts to the nine States and Union Territories to support them in public health measures for control and management of the disease. What is dengue, what causes it, what are the symptoms to look out for, and how is it treated? Let's find out.

A mosquito-borne infection Dengue is a mosquito-borne viral infection that is transmitted to people through the bite of an infected Aedes aegypti mosquito. When a mosquito bites us, it not only sucks blood but also secretes saliva that enters our bloodstream. This is how an infected mosquito passes on the infection. Dengue is a seasonal disease which witnesses a surge in cases post-rain. Dengue virus causes fever and haemorrhagic symptoms.

Dengue infections are caused by four related viruses namely DEN-1, DEN-2, DEN-3, and DEN-4 belonging to the genus Flavivirus. These four viruses are called serotypes because each has different interactions with the antibodies in our blood serum. The four dengue virus serotypes mean it is possible to be infected more than once. In other words, being infected from one dengue virus does not guarantee protection from the other three. Once a person gets infected, he becomes the main carrier of the virus and passes it to uninfected mosquitoes. After recovery, he becomes immune to that particular serotype for lifetime.

Flying killers

Mosquitoes thrive in tropical regions. Dengue mosquitoes breed only in clear water. They lay eggs on the surface of the water which hatch in eight days (or even less in extremely warm weather).

Mosquitoes take refuge in dark spaces indoors and use puddles, tree holes, discarded vehicle tyres, and plant pots around homes to breed. If water is not allowed to stagnate, mosquitoes cannot multiply. Did you know that only female mosquitoes are capable of biting us? They feed on our blood to source protein for their eggs.

According to the World Health Organization, mosquito-borne diseases kill several million people worldwide, every year.

Dengue symptoms

Dengue causes a severe flu-like illness that may last up to a week. In some cases, the fever could be life-threatening, resulting in bleeding, a fall platelet count, and sometimes extremely low blood pressure. Dengue symptoms include high fever, severe headache, pain behind the eyes, nausea, vomiting, acute stomach ache, muscle and joint pain, and skin rash. They begin to manifest three to 14 days after the bite. The severity of the symptoms increases if the infection is not treated properly and in time. Seek medical advice immediately if you have a fever or develop any of the dengue symptoms.

At present, there are no vaccines for dengue or specific medications to treat it. Pain killers are prescribed for relief from symptoms. Drinking plenty of fluids and taking ample rest are also advised. So the best way to protect ourselves from dengue is to avoid mosquito bites by sleeping under the net using mosquito repellent, etc.

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What is RTS,S/AS01 malaria vaccine?

October 6, 2021, marks a historic day in humanity's fight against malaria, as the World Health Organization (WHO) approved the rollout of the malaria vaccine, RTS.S/AS01 (RTS.S) among children living in sub-Saharan Africa and other at-risk regions.

Malaria is a deadly infectious disease that claims more than 4 lakh lives every year around the world. It is caused by Plasmodium parasites that are transmitted to people through the bites of infected female Anopheles mosquitoes, called the malaria vector. Among the five parasite species that cause malaria in humans, Plasmodium falciparum and Plasmodium vivax pose the greatest threat.

Who will get the vaccines and how efficient is it in preventing the spread of malaria?

WHAT is RTS,S/AS01?

RTS,S/AS01 or Mosquirix (trade name) has been developed by British drug manufacturer GlaxoSmithKline in collaboration with Seattle-based health non-profit PATH and a network of African research centres, with partial funding from the Bill and Melinda Gates Foundation. The vaccine is the result of 30 years of research and it targets Plasmodium falciparum, the most common parasite causing malaria in Africa. The vaccine offers no protection against the other four species such as P vivax, P ovale, P knowlesi and P malariae which are prevalent in Southeast Asia, Americas and Europe.

RTS,S was created in 1987 by scientists working in GlaxoSmithKline laboratories. The European Medicines Agency issued a positive scientific opinion on the vaccine in July 2015, concluding that the benefits of the vaccine outweigh the risks

RTS.S has been rigorously tested through a series of clinical trials since 2019 in seven African countries (Burkina Faso, Gabon, Ghana, Kenya, Malawi, Mozambique, and Tanzania).

Who is it for?

The WHO has recommended that the RTS,S/AS01 malaria vaccine be used for the prevention of P. falciparum malaria in children living in regions with moderate to high transmission as defined by it. The vaccine has been recommended to be provided in a schedule of four doses in children from 5 months of age.

What is its efficacy?

The current approval of the vaccine is based on the results of the ongoing pilot programme in Ghana, Kenya and Malawi. More than 2.3 million doses of the vaccine have been administered in these countries so far as part of the pilot. The following observations have been made since:

  • The vaccine offers 39% protection against malaria in children between the ages of five and 17 months.
  • The vaccine prevents approximately 4 in 10 (39%) cases of malaria and about 3 in 10 (29%) cases of severe malaria.
  • There is significant reductions in overall malaria admissions as well as malaria-induced anaemia.
  • The vaccine also reduced the need for blood transfusions, which are required to treat life-threatening malaria anaemia by 29%.

How does the vaccine work?

RTS,S works by introducing the immune system to a fragment of a protein that is naturally present on the surface of Plasmodium parasite when it enters the bloodstream through an infected mosquito. The protein in the vaccine stimulates the production of antibodies, and allows the body to mount a swift response to the parasite the next time it is encountered. The vaccine is designed to prevent the parasite from infecting the liver, where it can mature, multiply, re-enter the bloodstream, and infect red blood cells, which can lead to disease symptoms.

Why is developing a vaccine against malaria tough?

Malaria vaccines have been in development since the 1960s, with substantial progress only in the last decade.

  • Developing a vaccine against malaria parasite has been a difficult task, chiefly because of the parasite's complex lifecycle and genetical make-up. It has a multistage lifecycle occurring within two living beings, the vector mosquitoes and the vertebrate hosts (humans for instance). The survival and development of the parasite within the invertebrate and vertebrate hosts, in intracellular and extracellular environments, is made possible by more than 5,000 genes and their specialised proteins that help the parasite to invade and grow within multiple cell types and to evade host immune responses. The surface proteins and metabolic pathways keep changing during these different stages, that help the parasite to evade the immune clearance, while also creating problems for the development of drugs and vaccines.
  • The technical complexity of developing any vaccine against a parasite is another obstacle.
  • With no real market for a malaria vaccine in resource-rich countries like the U.S., pharmaceutical companies did not have a strong financial incentive to accelerate vaccine development. Hence there are a few malaria vaccine developers.

What are the symptoms and consequences of malaria?

Symptoms usually appear 10-15 days after the infective mosquito bite. According to the WHO, the first symptoms-fever, headache, and chills - may be mild and difficult to recognise as malaria. In no time, it can progress into severe illness and possible death.

Children may develop severe anaemia, respiratory distress or cerebral malaria, while adults can face multi-organ failure. Children under 5 years of age are the most vulnerable group affected by malaria.

Some facts about malaria

  • There are more than 400 species of Anopheles mosquito, of which around 30 are malaria vectors. All the important vector species bite between dusk and dawn.
  • Anopheles mosquitoes lay their eggs in water, usually shallow pools of fresh water, such as puddles, which are abundant during the rainy season in tropical countries. .
  • Vector control is the main way to prevent and reduce malaria transmission. The two WHO-recommended methods are - insecticide-treated mosquito nets and indoor residual spraying. Early diagnosis and treatment of malaria reduces disease and prevents deaths.
  • Exposure to malaria parasites does not confer lifelong protection.

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What does an allergic reaction to mosquito bites look like?

The more times a person has been bitten by mosquitoes, the more likely it is that they’ll become desensitized over time. That means adults typically have less serious reactions to mosquito bites than children do.

Common symptoms of mosquito bites include soft bumps on the skin that may become pink, red, and itchy. In most cases, redness and puffiness appears minutes after the mosquito punctures the skin. A firm, dark red bump often appears the next day, although these symptoms may occur up to 48 hours after the initial bite. According to the American Academy of Allergy, Asthma, & Immunology (AAAAI), contact with a mosquito must be six seconds or longer to produce a reaction.

As your mosquito bite heals, the itching sensation will fade, and skin will gradually take on a less red or pink hue until it returns to its normal color. This usually takes about three to four days. Swelling will also go down after about a week.

A typical mosquito bite is less than a ½-inch across.

Credit : Healthline

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What is Nipah and how does it spread?

Kerala was on high alert after a 12-year-old boy died of the deadly Nipah virus in Kozhikode, early this month. The State ramped up efforts to stop a potential outbreak, as health officials began to trace contacts and isolate hundreds of people who came into contact with the boy.

The virus has an estimated fatality rate of between 40% and 75%, according to the World Health Organisation (WHO), making it deadlier than the coronavirus.

The state dealt with Nipah in 2018, when more than a dozen people died from the virus. This time around, the concern is compounded by the fact that the state has grabbed national headlines in recent weeks for seeing the highest number of daily COVID-19 cases across India.

Nipah is a rare viral infection. Infected patients show symptoms of fever and respiratory problems in the early stages that quickly advance to fatal encephalitis (inflammation of the brain). Fruit bats or flying foxes of the Pteropodidae family are the natural host of the Nipah virus.

The WHO has listed Nipah as among the 10 priority pathogens requiring urgent research. The organisation takes into consideration the virus' ability to trigger lethal outbreaks and the non-availability of drugs against it.

What is Nipah?

Nipah is a zoonotic disease (zoonotic is a disease transmitted to humans from animals), spread by bats, pigs and infected people, according to the WHO. Outbreaks have been reported in Southeast Asia since 1998, when the virus was first identified in Malaysia. The 1998-99 outbreak spread from pigs to humans in Malaysia. It caused severe respiratory illness in pigs and encephalitic disease in humans. It killed 100 people and affected thousands of pigs. The Nipah virus has a mortality rate of 75%, according to the WHO.

How does it spread?

Fruit bats, the natural host of the Nipah virus, show no signs of infection. However, the virus spreads through the bats saliva or excreta. Humans and animals such as pigs become infected through contact or ingestion of materials contaminated with saliva or urine of such bats. In 2004, in Bangladesh, humans became infected after consuming date palm sap that had been contaminated by infected fruit bats. Humans also get affected when they come in contact with infected pigs or when they consume the meat of the animal. Human-to-human transmission happens through body fluids, including nasal or respiratory droplets, urine, or blood. Such transmission was recorded in Siliguri, West Bengal, in 2001, and in the 2018 outbreak in Kerala. In Siliguri, 75% of cases occurred among hospital staff or visitors.

What are the symptoms?

Symptoms typically present one to two weeks after exposure to the virus. Initial symptoms are flu-like. They include fever, headache, respiratory problems and muscle pain. This may be followed by neurological signs such as disorientation and dizziness. In severe cases, the infection can cause encephalitis, which is the inflammation of the brain, and eventually death. Survivors can have long-term neurological issues such as a seizure disorder or personality changes, according to the WHO.

What can be done to diagnose it?

According to the U.S. Centers for Disease Control and Prevention (CDC), during the early stages of the illness, laboratory testing can be conducted using real-time polymerase chain reaction (RT-PCR) from throat and nasal swabs, cerebrospinal fluid, urine, and blood. Later in the course of illness and after recovery, testing for antibodies is conducted using an enzyme-linked immunosorbent assay (ELISA).

What is the treatment?

There are no drugs or vaccine available against Nipah. The primary treatment is supportive care. Rest, hydration, and treatment of symptoms are advised. Individuals infected need to be hospitalised and isolated to avoid spread of disease to others. Identifying potential victims, testing them and treating them as early as possible are the way forward.

What should you do to protect yourself from Nipah?

  • Avoid exposure to animals such as bats and pigs.
  • Avoid eating fruits bitten by bats or that may have been contaminated by them.
  • Avoid contact with infected people.
  • Maintain personal hygiene. Practise handwashing regularly with soap and water.
  • Consume only well-cooked, home-made food.
  • Spread awareness among your friends and family members.

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