[health-vn] Antibiotics could vaccinate against malaria, says study

[vern weitzel]

http://www.scidev.net/en/news/antibiotics-could-vaccinate-against-malaria-says-study.html

Antibiotics could vaccinate against malaria, says study
Duncan Mboya

5 August 2010 | EN | 中文
[NAIROBI] Malaria sufferers might be able to protect themselves against life-threatening bouts of the disease by taking a single course of antibiotics, research in mice has shown.

Preventive treatment with 'needle-free'  antibiotic vaccines could be used to control the infection in areas with high levels of transmission, a study published last month (14 July) in Science Translational Medicinesuggests.

There are still no available vaccines against malaria. And although some antibiotics with anti-malarial properties, such as doxycycline, that kill the parasites directly are already in use as one-off, short-term prophylaxis, their  prolonged use is not an option for millions of people in the developing world where malaria is endemic.

Now, azithromycin and clindamycin, two common antibiotics, have been shown to provide additional and long-term protection against malaria, even after they are no longer taken.

"The combination of the prophylactic effect with the subsequent immune-mediated protection may be enough to protect population groups at risk, such as infants and young children, from severe forms of malaria," Steffen Borrmann, a lead author of the study and parasitologist at the Kenya Medical Research Institute, told SciDev.Net.

The team treated mice with the antibiotics before infecting them with malaria. After taking the drugs, the mice developed vaccine-like immunity lasting at least 40 days, and almost all were protected from complications that are often lethal.

It is still not clear how long the immunity would last in humans, but Borrmann toldSciDev.Net that "life-long would be the ultimate goal but we would be happy to achieve 1–2 year protection, [to last] during the most critical years in early childhood in high transmission areas".

The antibiotics work by causing small cavities in malaria parasites during their passage into the liver of the infected host. This stops the parasites from entering the blood stream,  giving time for the immune system to launch a sustained defence against the parasites.

This mode of action is similar to experimental vaccines that use weakened, whole parasites to elicit an immune response, said Borrmann.   

The tested antibiotics are available as safe, generic drugs, and there are no patent issues preventing their use in clinical trials or in clinical practice.

But they would likely not work in areas with low transmission levels, since the degree of immunity to subsequent infections depends on the quantity of malaria parasites already infecting the patient, Borrmann said.

Willis Akhwale, head of Kenya's Disease Prevention and Control department at the Ministry of Public Health and Sanitation, welcomed the findings, adding that the fight against malaria requires new tools to fully eliminate the disease.

"As we move from control to elimination, countries in Sub-Saharan Africa need new tools towards the eradication of malaria since insecticide treated nets and artemesinin combination therapies may not sustain the fight," he said.

Link to full article in Science Translational Medicine

http://stm.sciencemag.org/content/2/40/40ra49.full?ijkey=OAfu5Q9bUdH4Q&keytype=ref&siteid=scitransmed

Sci Transl Med 14 July 2010: 
Vol. 2, Issue 40, p. 40ra49 
DOI: 10.1126/scitranslmed.3001058
RESEARCH ARTICLE
Natural Immunization Against Malaria: Causal Prophylaxis with Antibiotics
Johannes Friesen1,2, Olivier Silvie1,2, Elyzana Dewi Putrianti1,2, Julius C. R. Hafalla3, Kai Matuschewski1,2,* andSteffen Borrmann1,4,*
+Author Affiliations

1Department of Infectious Diseases, Heidelberg University School of Medicine, 69120 Heidelberg, Germany.
2Parasitology Unit, Max Planck Institute for Infection Biology, 10117 Berlin, Germany.
3Immunology Unit, Department of Infectious and Tropical Diseases, London School of Tropical Medicine and Hygiene, London WC1E 7HT, UK.
4Kenya Medical Research Institute–Wellcome Trust Research Programme, Kilifi 80108, Kenya.
*To whom correspondence should be addressed. E-mail: matuschewski at mpiib-berlin.mpg.de (K.M.);steffen.borrmann at urz.uni-heidelberg.de (S.B.)
Malaria remains the most prevalent vector-borne infectious disease and has the highest rates of fatality. Current antimalarial drug strategies cure malaria or prevent infections but lack a sustained public health impact because they fail to expedite the acquisition of protective immunity. We show that antibiotic administration during transmission of the parasite Plasmodium berghei results in swift acquisition of long-lived, life cycle–specific protection against reinfection with live sporozoites in mice. Antibiotic treatment specifically inhibits the biogenesis and inheritance of the apicoplast in Plasmodium liver stages, resulting in continued liver-stage maturation but subsequent failure to establish blood-stage infection. Exponential expansion of these attenuated liver-stage merozoites from a single sporozoite induces potent immune protection against malaria. If confirmed in residents of malaria-endemic areas, periodic prophylaxis with safe and affordable antibiotics may offer a powerful shortcut toward a needle-free surrogate malaria immunization strategy.


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