The complex structure of monkeypox virus and insufficient basic research have brought challenges to the development of existing vaccines. At present, the number of confirmed monkeypox cases in non endemic countries and regions has exceeded 1000. Vaccine is a powerful weapon to stop the spread of the virus, but only one monkeypox vaccine has been approved for marketing in the world. Recently, some companies announced that they are launching new vaccine research and development, but they still face some challenges.
Recently, at the 14th China biological industry conference, zhenghaifa, vice chairman of Shenzhen Kangtai Biological Products Co., Ltd., said that monkeypox virus is not only large in shape, but also very complex in structure. It has a brick double membrane structure. The surface of the virus membrane contains rich tubular or filament structural proteins. However, the function of each protein on the virus is still unclear, and basic research is not done enough, which brings difficulties to the development of existing vaccines.
Monkeypox monkeypox is a zoonotic disease. Its initial symptoms include fever, chills, sweating, headache, muscle soreness, back pain, swollen lymph nodes and so on. Later, it can develop into a large-scale skin rash on the face and body.
Monkeypox virus and smallpox virus are close relatives, both belong to the family poxviridae, and smallpox virus has caused great harm to human beings, and it is also the first virus to be eliminated in the world. Since smallpox was eradicated, monkeypox virus is still the most pathogenic smallpox virus. Originally, monkeypox virus often occurred in West and Central Africa. Since May this year, confirmed cases of monkeypox have been found continuously in many countries and regions where monkeypox virus is not prevalent, which has aroused great concern all over the world. Although no imported monkeypox cases have been found in China, the General Administration of customs is deploying the health quarantine work at customs ports nationwide to prevent the superposition of epidemics.
Zhenghaifa said that monkeypox virus and smallpox virus belong to the same family and share many surface antigens. The corresponding vaccines have a certain cross protective effect. Smallpox vaccine (vaccinia virus) may have a certain protective effect against monkeypox. However, since smallpox virus disappeared in the 1980s, most countries have not conducted smallpox vaccine production and vaccination.
So far, there are two approved smallpox vaccines in the United States, developed by Acambis and Bavarian Nordic, respectively. The smallpox vaccine jynneos developed by Bavarian Nordic was approved by the U.S. FDA in 2018 for the prevention of skyflower and monkeypox infection among high-risk adults over 18 years old. It is the only non replicative smallpox vaccine approved by the FDA and the only monkeypox vaccine approved in the world.
It is worth noting that the infection rate of monkeypox virus seems to be on the rise since the global smallpox vaccination rate has declined. "Monkeypox virus is in the process of mutation, and some mutations found at present suggest that the virus may be developing towards higher infectivity. From the perspective of the basic infection number RO, in the 1980s, due to smallpox vaccine immunization, the immune level of the population was greater than 80%, and the RO of monkeypox virus was far less than 1; in 2012, the immune level of smallpox vaccine was about 60%, and the RO of monkeypox virus was slightly less than 1; at present, the immune level of smallpox vaccine was about 20%, and the RO of monkeypox virus was greater than 1 This also suggests that monkeypox still has a large-scale epidemic trend. " Zhenghaifa believes that, on the whole, monkeypox is still relatively harmful and should be prevented as soon as possible.
The existing vaccine development technologies can be divided into three generations. The first generation technologies include inactivated vaccine and live attenuated vaccine; The second generation technology includes subunit vaccine, virus like particles, etc; The third generation includes virus vector vaccine and nucleic acid vaccine. Can a new monkeypox vaccine be developed by combining these technologies?
Zhenghaifa said that in the development of poxvirus vaccine, the technical route of inactivated vaccine has been proved invalid, so it cannot be adopted. The vaccine "cowpox" used for prevention in history belongs to live attenuated vaccine. The protection rate against monkeypox is confirmed to be about 80%, but the toxicity is relatively large. It can be considered to attenuate on the basis of smallpox vaccine.
"The side effects of the technical route of subunit vaccine are relatively low. However, in view of the insufficient understanding of monkeypox virus protein and the unclear understanding of protective antigen, there are still challenges to develop a vaccine with this technology at this stage. In terms of virus vector vaccine, we can use the current live virus vectors, such as adenovirus, measles virus, yellow fever virus, poxvirus, to transfer the protective antigen gene of monkeypox into it, so as to be used in the development of vaccine It is a direction that can be explored at present, but it also has challenges; In terms of nucleic acid vaccine, it mainly includes DNA vaccine and mRNA. The former has not been applied in human body, while the latter has been successfully applied in the fight against COVID-19. The idea of using mRNA technology to develop monkeypox vaccine is worth exploring. "
It is worth mentioning that on May 24, 2022, Moderna company, an mRNA vaccine R & D enterprise, announced that it would use its mRNA vaccine R & D platform to carry out the R & D of monkeypox mRNA vaccine.