The marmoset is a small primate that weighs about one pound when fully grown, but it has many genetic and physiological similarities to humans. An advantage of using marmosets is that the animal’s response to Lassa infection completely mimics the response found in people who develop symptoms.

The availability of the marmoset for this research is expected to speed the testing of potential vaccines against Lassa fever, including a number of candidate vaccines that already have been developed and are waiting on a model like this for testing, said Jean Patterson n, chairman of the Department of Virology and Immunology at Southwest Foundation for Biomedical Research (SFBR).

Already, the scientists have been working with marmosets at SFBR to test a promising Lassa fever vaccine developed at the University of Maryland Biotechnology Institute. “Having this model will allow investigators to test their vaccines more quickly than they would be able to without it,” Ricardo Carrion Jr. said. “And because it mimics the human response to Lassa more faithfully than existing models, it might become the preferred model.”

Lassa fever is a viral illness that occurs in West Africa, spread by the “multimammate rat,” known for frequent breeding and a tendency to colonize where people live. Only about 20 percent of people infected with Lassa develop severe symptoms. Of those who get sick, the mortality rate is from 15-20 percent, but the mortality rate rises to 60 percent for those who are pregnant. Like humans, marmosets that die from the disease do so within 20 days of becoming ill. Of those people who recover, 30-40 percent suffer hearing loss and liver damage.

Lassa fever also causes a marked suppression of the immune system, an aspect of the disease that the researchers are tracking with the current marmoset vaccine study. “Pregnant women have such a high mortality rate from Lassa because pregnancy already causes immunosuppression, and Lassa compounds it,” Patterson said.; Source: Southwest Foundation for Biomedical Research