New Hanta Study - Virus May Not Clear Body

A group of international collaborators has observed that a hantavirus responsible for the often-lethal disease hantavirus cardiopulmonary syndrome may also be capable of establishing a long-term infection in the human body, raising the possibility that infection is not inevitably cleared by the body's immune system.

The results of their research, being published in this month’s issue ofPLoS Pathogens, showing that antiviral immunity not only persists at high levels but actually increases in intensity over a number of years were completely unanticipated.

“The long term consequences of such persistence for person-to-person transmission or for immunosuppressed patients are not known’ said Dr. Tobias Manigold who led the international research team from Clínica Alemana - Universidad del Desarollo, Santiago, Chile. “One of our next steps will be investigate what viral mechanisms are used by hantaviruses so that they can persist even after intense attack by the human immune system”

The investigators hope, through future investigations, to determine the basis for the continuation of the patients' immune reaction to a viral infection.

“While we had been aware that hantaviruses, normally carried by specific strains of wild field mice, develop persistent infection in their native wild rodent hosts, hantavirus experts had long considered that human infection was acute and self-limited,” said Brian Hjelle, a professor in the Departments of Pathology, Biology, and Molecular Genetics & Microbiology, who was the lead researcher from UNM.

The evidence in favor of such a hypothesis is based upon indirect observations, specifically the observation that the immune response to the infection does not wane over time as is expected for acute infections, but actually appears to gain steam over a period of months to years after the clinical illness has resolved. T

hese observations in patients who became ill after infection with the Andes strain of hantavirus that is native to South America, may indicate that patients who appear to have completely recovered from hantavirus infection, may in fact continue to harbor the virus in a location where it is protected from clearance by the patient's immune system. The researchers don’t yet know where that site might be.

“This is part of a growing body of research that suggests that ‘acute’ viral infections, infections that everyone ‘knew’ to be acute and self-limited may actually be persisting somewhere in the human body,” said Hjelle.

Globally, there are a number of hantaviruses that, all told, may cause as many as 200,000 cases of human disease per year. In man, two clinical conditions may arise: hemorrhagic fever with renal syndrome, caused by the Asian and European strains or hantavirus cardiopulmonary syndrome (HCPS) which is caused by the Sin Nombre virus (SNV – first identified in North America in New Mexico in the 1990s) and the Andes virus (ANDV) among others in the Americans.

In humans, hantavirus cardiopulmonary syndrome (HCPS) caused by the ANDV is endemic in the southern cone of Chile and Argentina but cases of HCPS are being increasingly reported all over South America since 1995. HCPS is an emerging infectious disease in North and South American and currently, Chile represents among the most endemic regions for HCPS with more than 580 cases since 1995. HCPS is characterized by fulminant pulmonary edema which progresses to shock and death in about 36 percent of patients with HCPS.

Transmission of ANDV to man is followed by infection of lung endothelial cells and, after an incubation period of 7 to 39 days, the development of vascular leakage syndrome, eventually leading to massive pulmonary edema, shock, and in a little more than one-third of cases, death.

Contact: Cindy Foster, 272-3322

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