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Zika, dengue fever and West Nile virus: Why vaccinations against tropical viruses are complicated

Thanks to global warming, diseases such as dengue fever and West Nile virus will also become a problem in Germany in the next five to ten years, predicts Leipzig researcher Sebastian Ulbert.

Thanks to global warming, diseases such as dengue fever and West Nile virus will also become a problem in Germany in the next five to ten years, predicts researcher Sebastian Ulbert. Since 2011, he has been checking which vaccines and active ingredients could help us. In other parts of the world, the dengue virus already has pandemic-like status. But: Vaccination against the virus is complex and not without risk.

Zika, dengue fever or the West Nile virus – all of these tropical diseases are caused by so-called flaviviruses. These pathogens, which are mostly transmitted by mosquitoes, have been known for a long time in many warmer countries. In Germany, infections are still very rare, but they are becoming more common.

Sebastian Ulbert researches flaviviruses at the Fraunhofer Institute for Cell Therapy and Immunology (IZI) in Leipzig. He says: “This will also be a very important topic for us in Germany in the future.” Responsible for the increase in infections the climate change. Ever higher temperatures are allowing the mosquitoes that transmit the virus to survive further and further north.

This is currently particularly clear in Italy. Ulbert reports: “I was just in northern Italy, in the area around Padua. In the summer of 2022, the intensive care units there were full of people infected with the West Nile virus.”

Dengue will not be like Corona – but mosquito bites will become more dangerous

In his opinion, panic is not appropriate, but he assumes that the situation in Germany could be similar in five to ten years - provided that climate change continues to cause higher temperatures. “One consequence, for example, will be that you will no longer be able to sit relaxed in the garden and let a mosquito bite you,” predicts Ulbert.

Flaviviruses will not reach dimensions similar to the corona pandemic, says the researcher. With regard to dengue fiber, one could currently speak of a pandemic, it's just not happening here. “There have already been strong outbreaks in Brazil and other parts of the world this year. Dengue fever is particularly dangerous for smaller children, and we are currently seeing many seriously ill people. “This is already a serious problem worldwide.”

Three pillars against flaviviruses: vaccines, test systems and active ingredients

There are three important pillars to better protect people from flaviviruses: vaccines, test systems and active ingredients that work directly against the viruses when they are already in the body. Sebastian Ulbert and his team have been working on the topic since 2011 and are developing both vaccines and active ingredients. A working vaccine is usually the better option, says Ulbert. “Active ingredients are usually very expensive to produce. This is particularly a problem with diseases that spread quickly and occur in emerging and developing countries.”

However, administering a vaccine against flaviviruses is not without risk. Ulbert explains: “As a rule, you become infected with a virus or are vaccinated and are then immune. In dengue fever, there are four different serotypes that circulate. If you were infected with one of the types or are only vaccinated against one and then become infected with one of the other three types, you are not only unprotected against that type, but sometimes even become more seriously ill.”

A vaccination or infection can cause more severe cases

This is due to a phenomenon called “antibody dependent enhancement of infection”, which means: If the body has already developed antibodies against a virus, it attacks a very similar virus with the same antibodies. These bind to the virus, but do not make it harmless because it is different from the virus that was originally “trained”.

The virus gets into the cells of the immune system and can multiply best there. “This also makes it more difficult to develop vaccines against other flaviviruses, such as the Zika virus. This could potentially predispose people to a serious infection with the similar-looking dengue virus.”

An already approved dengue vaccine gives people a mix of four vaccines that are supposed to work against all four serotypes. However, this doesn't work for everyone. A small proportion of those treated were also found to have a higher risk of severe dengue, says the researcher. “So you need vaccines that are so specific that they only work against a certain type of flavivirus or vaccines that are so comprehensive that you cover all flaviviruses at once.”

Vaccines that are particularly targeted can reduce the problems

He is currently researching vaccines that ignore certain parts of the so-called E protein (E for “envelope”). This E protein is common to many flaviviruses. The aim is to ensure that a possible vaccine addresses the virus subtypes and various serotypes particularly precisely.

In addition, an active ingredient against flaviviruses could still play a crucial role. The advantage here is that no cross-reactions take place. The active ingredients work against all flaviviruses equally, similar to how a broad-spectrum antibiotic works against bacteria. The active ingredient inhibits viruses in the body.

“The virus hijacks a cell and brings some enzymes with it; it uses other substances from the body cell itself to multiply.” This is where you can start by attacking the virus enzymes during the replication process in the cell. This stops the virus from multiplying. “Especially for people who are already infected with a virus and then come to the hospital seriously ill, an active ingredient would be a very good option.” said Sebastian Ulbert.

There is still a long way to go until the “super active ingredient”.

From Ulbert's point of view, one goal would be to develop an active ingredient that works against several viruses at the same time. But because they differ in their enzyme composition, it is not that easy. We are still a long way from the “super active ingredient” that eliminates all viruses at once.

Which pandemics will threaten humanity in the coming years and what researchers are already doing about them will be discussed in the MDR knowledge documentaries “What will be the next pandemic?” or “How do we prevent the next pandemic”. The second part also provides more insights into the work of Sebastian Ulbert and his team.

Article from “mdr” from November 14.11.2023, XNUMX

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