"Clinical Infection Sciences - Malaria Vaccines" is an engrossing example of a paper on the virus. The malaria parasite is known to be very complex hence making the development of the malaria vaccine a very difficult task; resultantly, there is no commercially available malaria vaccine despite the many years of deep research and development effort. However, more than twenty sub-unit vaccine constructs have been under evaluation either in form of clinical trials or even advanced preclinical development; appreciably, from the list RTS, S malaria vaccine is said to be currently the most advanced in development internationally (created in 1987 by scientists in GlaxoSmithKline’ s (GSK) laboratories). Initially, there were other candidate malaria vaccines that were not effectual as such, which led to the urge for more developments and ample research on the matter.
For instance, the plasmodium falciparum/pre-erythrocytic vaccine that had no compromise if its immune responses were gained through natural exposure or whether antibody or cell-mediated immunity, contribute substantially to naturally acquired immunity (Lauren, 2012, 1). Significantly, this vaccine had its merits and demerits but the most worrying challenge was based on the notion whether “ sterile immunity conferred by pre-erythrocytic subunit vaccines or attenuated whole organisms would not be mimicking naturally acquired immunity, yet this induced "non-natural" immunity could be more effective than is seen in nature, whether it supplements or replaces that usually seen in an endemic area” (Lauren, 2012, 1).
This brought about a lot of questions leading to how candidate vaccine antigens are targets of the antibodies that prevent sporozoite invasion of hepatocytes; however, deep focus on the matter led to a lot of concentration on Plasmodium circumsporozoite protein (CS).
It is expressed during the sporozoite and early life stages of parasitic infection whose protein is involved in the adhesion of the sporozoite to the hepatocyte and the invasion of the hepatocyte; moreover, anti-CS antibodies have been known to inhibit parasite invasion and are also associated with a reduced risk of clinical malaria in some studies. All the same, to date only the RTS, S/AS01E remains to be at the top of the list of candidate malaria vaccines, having been reviewed extensively making it the only vaccine in the third phase of evaluation; moreover, it is at least five to ten years ahead of all projects (Lauren, 2012, 1).
The vaccine showed a fifty-one percent efficacy in reducing the rate of all episodes of clinical malaria over fifteen months of follow up in the second phase trial in children residents in Kilifi, Kenya; the third phase trial began in May 2009 and completed enrolment in 2009 with over fifteen thousand children in sub-Saharan countries of Africa: Burkina Faso, Gabon, Ghana, Kenya, Malawi, Mozambique, and the United Republic of Tanzania. The RTS, S is said to aim at triggering the immune system to guard against the P, Falciparum parasite after it first enters the host’ s bloodstream through a mosquito bite and/or when the parasite infects liver cells: moreover, it is designed to prevent the parasite from infecting, maturing, and multiplying in the liver, after which the parasite would re-enter the bloodstream and infect red blood cells, leading to disease symptoms.
ReferencesLauren, S. 2012. A Review of Malaria Vaccine Projects Based on the WHO Rainbow Table: Malaria Journal. Web, < http://www.malariajournal.com/content/11/1/11> [Accessed 26th January 2014]