GM virus holds promise against cattle disease
- Malignant catarrh fever (MCF) kills many Maasai cattle in East Africa
- A modified MCF virus stops disease progression in an animal model
- It's early stage research and a potential vaccine is some way off
[NAIROBI] A new type of vaccine against malignant catarrh fever (MCF) ― a disease that kills thousands of cattle in East Africa each year ― could be in sight, according to a research group in Belgium.
Much of the disease has its reservoir in wildebeest, which are common in the savannah of East Africa. While it does not induce illness in these animals, it infects cattle owned by the Maasai people in large numbers and causes death in the majority of its victims.
The Maasai lose between seven and ten per cent of their cattle to MCF each year, mainly from migrating wildebeest, and other vaccine approaches have yet to be successful.
Now, researchers at the Faculty of Veterinary Medicine's Immunology-Vaccinology lab at the University of Liege, say they have genetically modified the version of the virus in wildebeest that causes MCF — acelaphine herpesvirus 1 (AlHV-1) — such that it does not cause the disease to develop after infection.
In a study published in the Proceedings of the National Academy of Sciences last month (29 April), they describe how an alteration to a synthetic version of the virus stops it from producing a protein that causes uncontrolled division of infected white blood cells, and the cancer-like MCF disease.
This 'neutered' virus has only so far been exposed to a small number of rabbits in a controlled experiment, but those that were infected by the synthetic version survived and were also then protected against the wild virus.
"In this study we have generated a virus that does not induce MCF, does not persist in the infected host and protects against a subsequent infection with a virulent virus," research group leader Benjamin Dewals tells SciDev.Net.
Besides the description of this vaccine candidate, we also have strong evidence that MCF is an acute disease that is not caused by the multiplication of the virus in cattle, but by the latent, or dormant, persistence of the virus and the induction of some kind of very aggressive lymphoma," he adds.
Despite the optimism by Dewals and his team, they acknowledge that it may take five to ten years before a vaccine is available to pastoralists.
George Russell, a specialist in cattle infections at the Moredun Research Institute in Scotland, and who has participated in a separate search for a MCF vaccine, says the study by Dewals' team is informative.
"The efficacy of such a vaccine will need to be demonstrated in cattle and the protection conferred will need to be evaluated in terms of dosage and duration of protection before field trials can be considered," he says.
The category of viruses to which MCF belongs, herpes viruses, are also among some of the most difficult to develop a vaccine for, according to Joseph Mbai, a lecturer in the veterinary department at the University of Nairobi, Kenya.
Their ability to mimic the host cell in the body is what makes them difficult to tame, he says.
This article has been produced by SciDev.Net's Sub-Saharan Africa news desk.
PNAS doi:10.1073/iti2113110 (2013)