Background Information to the Lassa Virus
Lassa fever virus (LASV) causes severe hemorrhagic fever and is highly endemic in western Africa. Lassa fever was first described in 1969, in the town of Lassa, Nigeria (Frame et al, 1970). It is thought to cause 300,00 - 500,00 infections per year, resulting in more than 5000 deaths (Ogbu et al, 2007). In the most acute infections, LASV can cause severe immunosuppression, septic shock-like syndrome, high fever and ultimately multisystem failure (Hastie et al, 2010). Recent studies (Holmes et al, 1990; Haas 2003) have shown LASV to be the hemorrhagic fever that is most frequently transported out of Africa to the USA and Europe. The development of therapeutics is a high priority for global public health and biodefense efforts.
Figure 1: False colour TEM micrograph of Lassa virus virions, adjacent to cell debris (Image courtesy of BBC health website:http://news.bbc.co.uk/1/hi/health/4626637.stm)Genome:
The lassa virus is a member of the arenaviridae family, a genus of viruses which primarily infect rodents, however at least 8 viruses have been shown to cause human disease. Many other arenaviruses also cause hemorrhagic fever, such as the Junin and Machupo viruses, all of which have fast replication rates. LASV has a bisegmented, ambisense† ssRNA genome which is illustrated in figure 1 (below).
The L-RNA codes for a viral RNA dependent RNA polymerase (L) and zinc ring finger motif (Z)
The S-RNA codes for the viral nucleoprotein (NP) and a viral glycoprotein (GP)
† Glossary:
Ambisense - A single-stranded genome that contains both positive-sense and negative-sense
RDRP - RNA-Dependent RNA Polymerase