IMMUNOLOGY: A Mixed Blessing
Stephen J. Simpson

Hepatitis B virus (HBV) and the parasite that causes malaria, both remain
health concerns of immense proportion. In certain parts of the world
individuals frequently become infected with both pathogens, raising the
question of how each disease might influence the course of the other.

In an established mouse model of HBV infection, Pasquetto et al. show that
the presence of malarial parasites can profoundly influence the course of
HBV infection. Expression of HBV genes in the liver was considerably
diminished upon co-infection with the malarial parasite Plasmodium yoeli.
Infection with both the liver and blood stages of the malaria parasite
resulted in this anti-viral effect, which was closely associated with intra
-hepatic inflammation. Although the induction of several proinflammatory
genes was detected within the liver, only interferons a/b and g were
identified as being critical for inhibiting HBV replication. This study may
help to explain some of the protective effects of malaria on the course of
HBV infection in man. -- SJS

Detains in: J. Exp. Med. 192, 529 (2000).