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Journal of Clinical Microbiology, November 1998, p. 3143-3148, Vol. 36, No. 11
Medical Microbiology Section, Department of
Virology, Bernhard Nocht Institute for Tropical Medicine, 20359 Hamburg, Germany,1 and
Hôpital
Gueckedou, Gueckedou, Republic of Guinea2
Received 2 April 1998/Returned for modification 7 July
1998/Accepted 11 August 1998
The nucleoprotein of Lassa virus, strain Josiah, was expressed in
Escherichia coli as an N-terminally truncated,
histidine-tagged recombinant protein. Following affinity purification
the protein was completely denatured and spotted onto nitrocellulose
membrane. A total of 1 µg of protein was applied for detection of
Lassa virus antibodies (LVA) in a simple immunoblot assay. Specific anti-Lassa immunoglobulin M (IgM) antibodies could be detected by
increasing the amount of protein to 5 µg. A panel of 913 serum specimens from regions in which Lassa virus was endemic and from regions in which Lassa virus was not endemic was used for
evaluating the sensitivity and specificity of the LVA immunoblot in
comparison to those of an indirect immunofluorescence (IIF) assay. The
sera originated from field studies conducted in the Republic of Guinea (570 serum samples) and Liberia (99 serum samples), from inpatients of
the clinical department of the Bernhard-Nocht-Institute, Hamburg, Germany (94 serum samples), and from healthy German blood donors (150 serum samples). In comparison to the IIF assay the LVA immunoblot assay
had a specificity of 90.0 to 99.3%, depending on the origin of the specimens. The sensitivity was found to be highest for the
Guinean samples (90.7%) and was lower for the Liberian samples (75%).
Acute Lassa fever was diagnosed by PCR in 12 of 59 (20.3%) patients
with fever of unknown origin (FUO) from the Republic of Guinea. On
admission to the hospital, nine Lassa fever patients (75%) were
reactive by the IgM immunoblot assay. One of the patients was infected
with a new Lassa variant, which showed 10.4% variation on the amino
acid level in comparison to the prototype strain of Lassa virus,
Josiah. Seven PCR-negative patients were reactive by immunoblotting.
The positive and negative predictive values of a single IgM immunoblot
result for acute, PCR-confirmed Lassa fever were therefore 53.6 and
93.0%, respectively. Because of its high negative predictive value, a
single IgM immunoblot result will be valuable for excluding acute Lassa
fever for cases of FUO in areas where Lassa fever is endemic.
0095-1137/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
Detection of Lassa Virus Antinucleoprotein Immunoglobulin G (IgG)
and IgM Antibodies by a Simple Recombinant Immunoblot Assay for
Field Use
*
Corresponding author. Mailing address: Medical
Microbiology Section, Department of Virology, Bernhard Nocht Institute
for Tropical Medicine, Bernhard-Nocht-Str. 74, 20359 Hamburg, Germany. Phone: 0049-40-31182-421. Fax: 0049-40-31182-378. E-mail:
termeulen{at}bni.uni-hamburg.de.
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