Setback in the fight against polio

Mutated polio virus apparently immune to vaccines

08/19/2014

Setback in the fight against polio? So far, vaccination has been considered the only effective protection against poliovirus-induced infectious disease. But researchers from the Institute of Virology in Bonn have now discovered a virus strain that could possibly be ineffective against currently existing vaccines. As a result, the worldwide fight against the disease continues to be a major problem.

WHO wants to completely eradicate polio by 2018
Until recently, the so-called „poliomyelitis“ almost extinct. Through the wide use of the oral vaccine and the program „Global Polio Eradication Initiative“ According to the World Health Organization (WHO), the virus was largely suppressed, so that the WHO formulated the goal of completely eradicating the disease by 2018. But the fight against the poliovirus-induced infectious disease seems to be more difficult than expected, because the existing vaccines might not be effective against all variants of the virus. An international research team from the Institute of Virology in Bonn has now come to this conclusion. The scientists around Christian ‎Drosten had examined the poliovirus virus type I, which had led in 2010 in the Congo to a serious polio wave. As reported by the University of Bonn, 445 mostly young adults had been proven to be infected, and in 209 cases the disease had ended fatally.

Antibody in the blood serum against the three types of poliovirus
The polio wave in the Congo was an important subject of investigation for the scientists, not only because of the high number of victims. At that time it was also noticeable that the people who suffered from paralysis in the wake of a contagion were relatively old compared to other outbreaks of polio. Accordingly, the researchers wondered how far the then-rampant polio virus type I differs from other viruses and whether the currently existing vaccines are effective against the pathogen ‎can be used. For this purpose, they examined the genome of the virus and found that the surface was slightly altered compared to other polioviruses. In addition, the researchers analyzed the blood serum of 24 people who had fallen victim to polio at that time and came to an interesting conclusion: In almost all samples could be found antibodies against the three types of poliovirus. Because antibodies are caused by infection with or vaccination against a pathogen such as the poliovirus, this fact indicated that these individuals had previously been in contact with polioviruses.

New findings through elaborate neutralization tests
But how dangerous is the Congolese Poliovirus Type 1? To answer this question, the researchers led one ‎so-called „Neutralization test“ (short: NT, too „Plaque reduction assay“ gennat), by means of which neutralizing antibodies against certain viruses in blood serum can be detected. For this purpose, antibodies to the surface of the virus „bound“, which prevents its uptake into the cell and stops further propagation. As a result, the number of plaques in a cell culture decreases, so that ultimately can be measured, ‎how the cells could be protected from being destroyed by the virus. As the scientists report in the "Proceedings" of the US Academy of Sciences, they performed the elaborate neutralization test with the blood serum of the 24 deceased patients as well as the ‎of 63 control persons who had been vaccinated against polio (12 persons from Gabon and 51 persons from Germany). The result: The antibodies of the "PV1-RC2010" showed in comparison to other virus variants a significantly lower activity - so that in the case of some vaccinated persons even the vaccine protection would not have been sufficient to fend off the virus. Accordingly, according to the researchers to assume that the slightly altered surface of the Congo virus would cause the antibodies do not bind so well to them ‎can. „We isolated polio viruses from the deceased and examined them more closely“, so Dr. Jan Felix Drexler, who conducted the study at the Institute of Virology of the University Hospital Bonn under the direction of Prof. Dr. med. Christian Drosten together with his colleagues from Gabon Gilda Grard and dr. Eric Leroy had performed. „The pathogen carries a mutation that changes its shape at a crucial point“, the expert explains further. As a result, the antibodies induced by the vaccine could barely recognize the mutated virus and therefore could not be put out of action.

Risk of fatal respiratory paralysis
A potentially severe setback in the fight against poliomyelitis, although colloquially as „poliomyelitis“ but may also affect adults. However, mostly children between the ages of three and eight years are affected by the disease, for which there has been no causal treatment. Polio can take a very different course, usually it remains asymptomatic, so that affected people do not notice the infection, but sometimes there are also general symptoms of illness such as fever, headache, diarrhea or sore throat. The "classic" polio or a severe course, however, is rather rare. This is mainly characterized by paralysis of the legs, in addition to other muscles (such as in the arm, stomach, chest or eyes) can show symptoms of paralysis, typical are also strong back, neck and muscle pain. It is particularly dangerous when the respiratory muscles are affected, because then there is a risk of fatal respiratory paralysis.

„We must not put our hands in our lap“
Since the polio epidemic in the Congo could be stopped at that time by a massive vaccination program and hygiene measures, according to the researchers, the current vaccines were generally classified as effective - provided they were used in a timely and consistent manner. Nevertheless, the mutated pathogen is one „warning“: „We must not put our hands in our lap“, so the warning of the scientists. „We need to further increase the vaccination rate and develop new, more potent vaccines. Only then is there a chance to permanently defeat polio.“ (No)