The paradoxical vaccine
For decades, scientists have been trying to create a vaccine that would prevent the spread of malaria among people through mosquito bites. One of the potential approaches to solving this issue is to immunize people with a vaccine that blocks the transmission of the pathogen. Several variants of such a vaccine have shown good results, but have not been thoroughly tested due to undesirable side effects and limited effectiveness.
A group of researchers led by Associate Professor Jonathan Lovell from the University of Buffalo has proposed a simple way to increase the effectiveness of this type of vaccine. If successful, their development will reduce the spread of the disease, which annually claims more than 400 thousand lives, mainly of young children in sub-Saharan Africa.
To develop vaccines that block the transmission of the pathogen, specialists were pushed by the method of spreading malaria. It consists in the fact that a mosquito infected with the pathogen bites a person and infects him. Subsequently, an infected person transmits the pathogen when bitten to another mosquito, which, in turn, finds and bites a new victim, infecting her.
The emergence of an effective vaccine that blocks the transmission of the pathogen in combination with the use of mosquito nets, insecticides, antiparasitic drugs and other types of vaccines can break this vicious circle. Such a vaccine will not prevent infection of an immunized person, but it will radically reduce the likelihood of malaria infection of people living together.
Previously, research in this area focused on technologies such as genetic engineering and chemical binding of toxic proteins to enhance reactions to a vaccine that blocks the transmission of the pathogen. Each of these strategies has its own potential, but they are very costly in terms of time and finances. The biotechnological approach developed by the authors is characterized by relative simplicity of implementation and high efficiency.
The life cycle of malarial plasmodium consists of many stages. Various parasite proteins are the best targets for a vaccine that will form an immune response to these proteins. Purification of these proteins for the manufacture of vaccines often involves their modification by small chains of amino acids, known as polyhistidine tags.
The authors found that antigens can be mixed with nanoparticles containing a small amount of cobalt-containing porphyrin and phospholipid. Cobalt-containing porphyrin, whose structure is similar to that of the vitamin B12 molecule, is responsible for binding nanoparticles to antigens. The resulting structure is a next–generation adjuvant - an immunological agent that increases the effectiveness of vaccines. The vaccine triggers the production of antibodies to malaria plasmodium in the human body, which are transmitted to a mosquito when an immunized person is bitten.
In experiments on mice and rabbits, the researchers demonstrated that antibodies to the Pfs25 protein effectively block the development of malaria plasmodium in the intestines of mosquitoes. In additional formulations, the adjuvant was combined with a variety of malaria antigens, which presumably should block the spread of malaria at different stages of the disease.
The next stage of the work will be the preparation and conduct of additional experiments necessary to transfer the technology to the stage of clinical trials.
Article by Wei-Chiao Huang et al. A malaria vaccine adjuvant based on recombinant antigen binding to liposomes is published in the journal Nature Nanotechnology.
Evgenia Ryabtseva, portal "Eternal Youth" http://vechnayamolodost.ru based on the materials of University at Buffalo: Vaccinating humans to protect mosquitoes from malaria.