Figure 5. Morphology (A), Genome structure (B)
andreplication (C) of A renaviruses.
Arenaviruses merit significant interest as clinically important human pathogens, including several causative agents of hemorrhagic fever disease (Figure 5).
Using Lymphocytic Choriomeningitis Virus (LCMV), the prototype member in the family, Dr. Martinez-Sobrido have found that the viral nucleoprotein (NP) inhibits the IFN response in infected cells by interfering with the activation of the Interferon Regulatory Factor-3 (Figure 6, Inhibition of IRF-3). This was the first nucleoprotein described to block production of Type I interferon during viral infection as well as the first member of the Arenaviridae family described to counteract the Type I IFN response.
Additionally, he found that the nucleoprotein encoded by other members in the family (with the exception of Tacaribe virus) is able to counteract the IFN response. By creating several LCMV-NP mutants, Dr. Martinez-Sobrido have been able to undercover the LCMV-NP domain involve in inhibition of type I IFN, including amino acids at positions 382-386 (Figure 6, NP functional domains).
Figure 6. Inhibition of IRF-3 by influenza virus NS1 and
arenavirus NPs (left): HA-tagged influenza NS1 and NPs
from the indicated members of the Arenaviridae family(red)
were tested for inhibiting nuclear translocation of a
GFP-tagged IRF-3 (green), after Sendai Virus infection.
NP functional domains (right): A domain in the C-terminal
region of LCMV-NP (residues 370-553) was identified
as critical for the anti-IFN function of the viral protein.
Amino acid residues at positions 382, 385, and 386
on LCMV-NP were identified as critical for counteracting
the IFN response. All primary structure of the viral
protein, with the exception of the last 5 amino acid
residues is required for the replication and
transcription activity of the viral polypeptide.
He is currently using reverse genetics techniques (Figure 7) to rescue recombinant viruses carrying mutations on NP that affect its ability to counteract the IFN response and determine its contribution in viral pathogenesis.
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Figure 7. Arenavirus plasmid-based reverse genetics
techniques: Plasmids encoding the viral proteins required for
replication and transcription and the two viral RNA segments
are co-transfected into BHK21 cells. Tissue culture
supernatants containing recombinant viruses are used
to study different aspects of the biology of arenaviruses.