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Journal of Virology, March 2000, p. 2186-2192, Vol. 74, No. 5
Departments of
Virology1 and
Immunology,3 Bernhard Nocht Institute
for Tropical Medicine, and Department of Hemotransfusion,
University Hospital Eppendorf,4 Hamburg,
Germany; Projet sur le Recherche de Fièvres Hemorragiques
en Guinée (PFHG), Conakry, Republic of
Guinea5; and EPICENTRE (Groupe
Europeénne d'Expertise en Epidemiologie), Paris,
France2
Received 11 August 1999/Accepted 2 December 1999
T cells must play the major role in controlling acute human Lassa
virus infection, because patients recover from acute Lassa fever in the
absence of a measurable neutralizing antibody response. T cells alone
seem to protect animals from a lethal Lassa virus challenge, because
after experimental vaccination no neutralizing antibodies are
detectable. In order to study human T-cell reactivity to single Lassa
virus proteins, the nucleoprotein (NP) of Lassa virus, strain Josiah,
was cloned, expressed in Escherichia coli, and affinity
purified. Peripheral blood mononuclear cells (PBMC) obtained from 8 of
13 healthy, Lassa virus antibody-positive individuals living in the
Republic of Guinea, western Africa, were found to proliferate in
response to the recombinant protein (proliferation index
0022-538X/00/$04.00+0
Characterization of Human CD4+ T-Cell
Clones Recognizing Conserved and Variable Epitopes of the Lassa
Virus Nucleoprotein
10). PBMC
obtained from one individual with a particularly high proliferative
response were used to generate 50 NP-specific T-cell clones (TCC). For
six of these the epitopes were mapped with overlapping synthetic
peptides derived from the sequence of the NP. These CD4+
TCC displayed high specific proliferation and produced mainly gamma
interferon upon stimulation with NP. Because variation of up to 15% in
the amino acid sequences of the structural proteins of naturally
occurring Lassa virus variants has been observed, the reactivity of the
TCC with peptides derived from the homologous epitopes of the Nigeria
strain of Lassa virus and of the eastern Africa arenavirus Mopeia was
tested. With the Nigeria strain of Lassa virus the levels of homology
were 100% for two of these epitopes and 85% for three of them,
whereas homology with the respective Mopeia epitopes ranged from 92 to
69%. Reactivity of the TCC with peptides derived from the variable
epitopes of the Nigeria strain and of Mopeia was reduced or completely
abolished. This report shows for the first time that seropositive
individuals from areas of endemicity have very strong memory
CD4+ T-cell responses against the NP of Lassa virus, which
are partly strain specific and partly cross-reactive with other Lassa
virus strains. Our findings may have important implications for the strategy of designing recombinant vaccines against this mainly T-cell-controlled human arenavirus infection.
*
Corresponding author. Mailing address: Department of
Virology, Bernhard Nocht Institute for Tropical Medicine,
Bernhard-Nocht-Str. 74, 20359 Hamburg, Germany. Phone: 49 40 42828 421. Fax: 49 40 42818 378. E-mail:
termeulen{at}bni.uni-hamburg.de.
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