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NIAID Researchers Take Aim at Filarial Infections

In the NIAID Laboratory of Parasitic Diseases (LPD), Thomas B. Nutman, M.D., heads several projects studying filarial diseases, which include neglected diseases such as onchocerciasis and lymphatic filariasis.

Helping Decode Filarial Genomes and Proteomes

Mapping the genes and proteins of humans, animals, and even viruses has proven an important modern technology that helps researchers to pinpoint the “why” and “where” of what they study. Dr. Nutman and fellow LPD scientists were part of the group that mapped the genes and proteins of the parasitic worm Brugia malayi, one of the causes of the debilitating and disfiguring disease lymphatic filariasis.

LPD researchers also have worked to decode B. malayi proteins at the different stages of the parasite’s life when it interacts with humans. This mapping helps to define the biology of the parasite and could eventually be used to identify targets in the parasite that are vulnerable to potential new drugs or vaccines.

photo of Brugia malayi
Parasitic worm Brugia malayi in a thick blood smear. B. malayi can inhabit the lymph nodes and tissues of humans and is one of the causative agents for lymphatic filariasis.
Credit: CDC/M. Melvin

Studying How the Parasite Manipulates Cells

When B. malayi infects a human, the immune system dispatches natural killer (NK) cells to destroy the invading parasite. NK cells are a vital part of the human body’s natural response to infection. When their job is done, NK cells die, undergoing a process called apoptosis.

A study by LPD scientists and colleagues found that when B. malayi enters the body, it causes a more powerful initial reaction from NK cells than usual. However, this strong initial response also is followed by apoptosis more rapidly than usual. While the significance of this is not yet fully clear, it means that NK cells are gone from the body sooner than normal after fighting the filarial parasite.

Recent findings also indicate that B. malayi causes dendritic cells to undergo apoptosis. Dendritic cells are often called the sentinels of the immune system; they direct how and when the immune system responds to invading parasites. While LPD researchers do not yet fully understand why the parasite kills dendritic cells, this finding is important in understanding how B. malayi manipulates the immune system and provides new insights into possible therapies for filarial infections.

Finding that Travelers are at Risk

While filarial diseases like onchocerciasis mostly affect those living in tropical regions, travelers to regions where these diseases are widespread can also be exposed. Dr. Nutman and his colleagues found that filarial infections accounted for 271 of the 43,722 medical conditions reported to the GeoSentinel Surveillance Network, a network of travel/tropical medicine clinics on six continents. They also found that long-term travel of more than a month was more likely to be associated with a filarial infection than shorter trips.

This new analysis defines the characteristics of those who acquire filarial infections following travel, helping to provide a backdrop to pre-travel advice and post-travel treatment for those at risk of acquiring a filarial infection.

Read more about these findings in Neglected Tropical Diseases Burden Those Overseas, But Travelers Also at Risk.

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Last Updated January 13, 2009

Last Reviewed January 13, 2009