Tuesday January 21, 2020

Novel Experimental Vaccine Offering Hope Against Malaria

A year later, the vaccinated non-human primates still had immunity against malaria, while eight control animals that were not vaccinated did not

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Malaria, Vaccines
This new type of bed net can help prevent malaria: Lancet. (VOA)

An experimental new malaria vaccine is offering potentially long-lasting immunity against the persistent parasite that sickens hundreds of millions of people each year, a study suggests.

Most vaccines are designed to encourage the human body to respond to invading, disease-causing pathogens by creating antibodies that disable those pathogens.

However, the new vaccine takes a different approach by using a weakened form of a common herpes virus – cytomegalovirus, or CMV – that infects most people without causing the disease.

This new vaccine reduced the malaria-causing parasite’s release from the liver and into the blood of infected rhesus macaques by 75 to 80 per cent, reported the paper published in the journal PLOS ONE.

“The problem with most vaccines is that their effectiveness is often short-lived,” said lead author Klaus Fruh, professor at the Oregon Health and Science University in the US.

More people die of malaria than anything else in the world.
More people die of malaria than anything else in the world.

“Our cytomegalovirus-based vaccine platform can create and keep immunity for life. With further research and development, it could offer a lifetime of protection against malaria,” Fruh added.

Malaria is a serious and sometimes fatal disease caused by Plasmodium parasites, which are spread to humans through mosquito bites.

It can cause high fevers, shaking chills, flu-like illness and, in the worst cases, death.

Worldwide, 216 million people were infected with malaria in 2016, leading to 445,000 deaths.

Fruh and his team weaved tiny bits of their target pathogen into CMV, which is already being used in vaccines being developed to battle HIV and tuberculosis.

Those who receive the resulting, re-engineered CMV vaccine produce memory T-cells that can search for and destroy pathogen-infected cells.

A health service worker takes a blood sample for a malaria test in Dajabon, Dominican Republic, on the border with Haiti, Oct. 6, 2009. A test that doesn't require a needle or blood has won the Africa Prize for Engineering Innovation
A health service worker takes a blood sample for a malaria test in Dajabon, Dominican Republic, on the border with Haiti, Oct. 6, 2009. A test that doesn’t require a needle or blood has won the Africa Prize for Engineering Innovation, VOA

The team developed two different versions of their CMV-based malaria vaccine while using four different proteins made by the Plasmodium parasite.

The resulting vaccines delayed the parasite’s appearance in the blood of 16 infected and vaccinated rhesus macaques by eliminating between 75 and 80 per cent of parasites from the liver.

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A year later, the vaccinated non-human primates still had immunity against malaria, while eight control animals that were not vaccinated did not.

The CMV vaccine platform has been licensed by San Francisco-based Vir Biotechnology, which plans to lead a human clinical trial for a CMV-based HIV vaccine in 2019.  (IANS)

Next Story

Changing the Dose of TB Vaccination may Improve its Efficacy: Study

New approach improves efficacy of TB vaccine says a new study

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TB vaccination
Tuberculosis (TB) is the leading infectious cause of death globally, yet the world's only licensed TB vaccine, Bacille Calmette-Guerin (BCG), was developed a century ago. Pixabay

Researchers have shown that simply changing the dose and route of administration from intradermal (ID) to intravenous (IV) greatly increases the vaccine’s ability to protect rhesus macaques from infection following exposure to Mycobacterium tuberculosis (Mtb), the bacterium that causes TB.

Tuberculosis (TB) is the leading infectious cause of death globally, yet the world’s only licensed TB vaccine, Bacille Calmette-Guerin (BCG), was developed a century ago.

Given to infants via a needle placed just under the skin, BCG protects babies from a form of the disease called disseminated TB but is far less effective at preventing pulmonary TB.

The findings from University of Pittsburgh in US, provide a new understanding of the mechanisms of BCG-elicited protection against tuberculosis infection and disease.

In addition, the finding, published in the journal Nature, supports investigation of IV BCG administration in clinical trials to determine whether this route improves its effectiveness in teens and adults.

According to the researchers, to control Mtb infection and prevent clinical disease, a TB vaccine must elicit strong, sustained responses from the immune system’s T cells, specifically those in the lungs. However, the standard, ID, route of BCG administration may not generate enough of these critical cells in the lungs.

TB
A TB vaccine must elicit strong, sustained responses from the immune system’s T cells, specifically those in the lungs. Pixabay

The research team hypothesized that administration of BCG by IV or aerosol (AE) routes would overcome this hurdle and thus confer substantially better protection from infection and disease in rhesus macaques following challenge with virulent Mtb. In their study, groups of animals received the BGC vaccine by ID, AE or IV routes.

The scientists assessed immune responses in blood and in fluid drawn from the lungs for a 24-week period following vaccination. IV BCG vaccination resulted in the highest durable levels of T cells in the blood and lungs.

Six months after vaccination, the researchers exposed groups of vaccinated rhesus macaques (immunized via ID, AE or IV routes) and a group of unvaccinated macaques to a virulent strain of Mtb by introducing the bacteria directly into the animals’ lungs. They then tracked the infection and disease development over three months.

Nine out of 10 animals vaccinated with IV BCG were highly protected; six showed no detectable infection in any tissue tested and three had only very low counts of Mtb bacteria in lung tissue.

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All unvaccinated animals and those immunized via ID or AE routes showed signs of significantly greater infection.

The investigators concluded that IV BCG conferred an unprecedented degree of protection in an animal model of severe TB and ‘represents a major step forward in the field of TB vaccine research.’ (IANS)