Development of malaria vaccine: vaccination to weaken live malaria parasites, taking chloroquine, etc.

US scientists develop malaria vaccine: vaccination to weaken live malaria parasites, taking drugs such as chloroquine

American scientists develop malaria vaccines: vaccination to weaken live malaria parasites and take chloroquine and other drugs.

In April 2016, China reported the last case of local primary malaria.
More than five years later, the World Health Organization (WHO) announced that China had passed the malaria elimination certification
.

However, on a global scale, the burden of malaria is still serious, especially in Africa, the hardest-hit area, where more than 90% of global malaria cases are in Africa each year

Professor Patrick Duffy, director of the Malaria Immunization and Vaccinology Laboratory of the National Institute of Allergy and Infectious Diseases, and others believe that the development of a vaccine with durable immunity is imminent when the global burden of malaria has stagnated
.

On the evening of June 30th, Beijing time, the top academic journal Nature published an online paper by Duffy and his colleagues titled "Two chemoattenuated PfSPZ malaria vaccines induce sterile hepatic immunity", reporting a malaria vaccine strategy : Inoculation with weakened malaria parasites and then use preventive medications, showing a high level of protection in a trial involving 56 subjects

"Nature" also published a commentary on the opinions of Nana K.
Minkah and others from the Global Infectious Disease Research Center of Seattle Children's Research Institute at the same time
.

Minkah et al.

Although scientists have identified the malaria parasite as a malaria pathogen 140 years ago, there has not yet been a vaccine that provides a high level of protection against malaria parasite infections on the market
.

Plasmodium has about 5,300 genes.

The sporangia and the hepatic stage are called the PE stage together, and have been the target of malaria vaccine development since more than 50 years ago
.

Duffy et al.

However, considering the limitations of the single-protein vaccine approach, vaccines using live PE parasites that infect the liver but do not cause malaria have gradually received greater attention
.

Immunization with replication-deficient Plasmodium falciparum radiation-attenuated sporozoites (PfSPZ-RAS) is the most studied pan-parasite vaccine so far

In this latest study, Duffy and his colleagues optimized the chemopreventive vaccination (CVac) protocol, that is, under the preventive effect of pyrimethamine (PYR) or chloroquine (CQ), inoculation sterile, purified, cryopreserved, Infectious Plasmodium falciparum sporozoites (PfSPZ), pyrimethamine and chloroquine can kill parasites in the liver and blood stages, respectively
.

The research team provided immunizations to 56 healthy adult volunteers, and a few days later, provided the volunteers with a dose of pyrimethamine or chloroquine
.

They evaluated the efficacy of the vaccine against both homologous and heterologous controlled human malaria infections (CHMI) after 3 months of immunization

Studies have found that higher doses of vaccines are related to higher levels of vaccine efficacy
.

After PfSPZ-CVac (PYR) of 4-fold increase in dose, CHMI homologous vaccine protective efficacy increased from 22.
2% to 8 7.
5 ; at high doses, the protective efficacy of the vaccine for the heterologous CHMI 77.
8%
.
The PfSPZ-CVac (CQ) program is better, using high doses of chloroquine while immunizing with infectious spores, against the 7G8 strain found in Brazil, achieving 100% protection on 6 people for up to three months
.
This validates the important non-specific protective effect, because an effective vaccine must be protective against various strains of Plasmodium falciparum in natural circulation
.
Minkah and others also mentioned that a major obstacle to the development of a successful malaria vaccine is the large diversity of Plasmodium falciparum strains around the world
.

7.
5

Minkah et al.
also commented that the reported vaccine still has several limitations that require attention
.
One of the most concerning is that this live parasite vaccine requires strict compliance with the regulations on taking concomitant drugs to prevent malaria caused by vaccination
.
This is feasible in controlled clinical trials, but if vaccinating billions of people, it will be difficult to implement
.

Another issue that needs to be considered is that any current pan-parasite vaccine strategy requires the production of sporozoites in live mosquitoes, so there is a huge challenge in expanding production
.