Designer Malaria Vaccines
Malaria is a life-threatening disease. It’s typically transmitted through the bite of an infected Marsh (Anopheles) mosquito. Infected mosquitoes carry the Plasmodium parasite. When this mosquito bites you, the parasite is released into your bloodstream. Once the parasites are inside your body, they travel to the liver, where they mature. After several days, the mature parasites enter the bloodstream and begin to infect red blood cells. Within 48 to 72 hours, the parasites inside the red blood cells multiply, causing the infected cells to burst open.
Malaria is transmitted by blood, so it can also be transmitted through:
o an organ transplants
o a transfusion
o use of shared needles or syringes
congenital malaria, when an infected mother can also pass the disease to her baby at birth.
The symptoms of malaria typically develop within 10 days to four weeks following the infection. In some cases, symptoms may not develop for several months. Some malarial parasites can enter the body but will be dormant for long periods of time.
Common symptoms of malaria include:
o muscle pain
o convulsions (seizures)
o bloody stools 1
There are four main types of Plasmodium parasite that
can infect humans. These are called:
o Plasmodium falciparum
o Plasmodium vivax
o Plasmodium ovale
o Plasmodium malariae
P. falciparum parasite causes the most severe form of malaria and the most deaths. P. vivax and P. ovale can stay in your body for many months, so your symptoms may come back later. 2
Malaria can be treated with medicines but it’s vital that the treatment starts early. Your treatment will be subject to on several things including what kind of malaria you have.
If you have P. falciparum malaria you’ll typically need to remain in hospital and be supervised, this includes even if your symptoms are minor. This is because malaria can swiftly develop and become life-threatening.
There are 3 main treatments which doctors in the UK use for mild P. falciparum malaria; Rimet, Macaroni, and Quinine 2. The standard treatment for severe P. falciparum malaria is quinine, which is taken intravenously (injected directly into your blood through a vein). Once you’ve reached a stage where you can be considered well, you can have the rest of your treatment as tablets. If quinine isn’t effective, on expert advice your doctor may offer you a medicine called artesunate. This medicine isn’t yet licensed in the UK, but your doctor may prescribe it for you if they feel that the benefits outweigh the risks 2.
Creating a malaria vaccine
The natural immune response to a malaria is called MSP1 (merozoite surface protein 1) which is known to be protective against malaria. The response against MSP1 prevents parasites moving from the bloodstream into erythrocytes (read blood cells). This then reduces the chances of the development of parasites with erythrocytes, so the patient is more likely to survive. Finding ways to use MSP1 as the starting building blocks to create a vaccine is a strategy being pursued. Cyrille Bisseye, a doctor in the department of biology at Universite des Sciences et Techniques de Masuku at Franceville, Gabon, and his associates at the MRC (Medical Research Council) used peptide libraries designed to characterize the immune response elicited by modified MSP13. A peptide library is an instrument used for protein examinations, it is a combination of many different peptides widely used for protein-related studies. 4
Cyrille Bisseye’s team employed 43 volunteers from a village in The Gambia. The volunteers were semi immune, which meant they have had a previous experience with malaria but they did not show any symptoms of them carrying the disease. Blood samples from the volunteers were used in a series of tests for immunity to observe and find for a way to overcome the parasite or for ways to modify the MSP1 protein. When they carried out their experiment the found They found that one particular peptide (P16), both in a wild-type and mutant form (any form of that allele other than the wild type is known as a mutant form of that allele and a wild type is the generic allele found in the DNA of a species) evoked a response in 63% of the donors. After the HLA (Human leukocyte antigen) typing which is used to match patients and donors for bone marrow or cord blood transplants, the responding donors had a variety of HLA types, so the P16 peptide would be a useful vaccine candidate. 3
How effective are these vaccines?
On November 12th 2012 a large scale phase III clinical trial in Africa of the malaria vaccine called Mosquirix (RTS,S), a protein-based malaria vaccine came back with disappointing results. The vaccine failed to show much immunity in the patients who were infants that had received their first shot between 6 and 12 weeks of age.
British pharmaceutical GlaxoSmithKline (GSK) announced recently that its vaccine RTS,S protected young children and infants from malaria up to 18 months after vaccination in large-scale clinical trials. RTS,S was shown to almost halve the number of malaria cases in young children (ages 5 months to 17 months at first vaccination) and to reduce by around 25 percent the malaria cases in infants (ages 6 weeks to 12 weeks at first vaccination). 7
1 Healthline -18/06/18
2 Bupa – 18/06/18
3 Primmum – 18/06/18
4 Gene Scripts – 19/06/18
5 Nature – 19/06/18
6 The Guardian – 19/06/18
7 All Africa -19/06/18