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Infect. Immun., May 1996, 1679-1684, Vol 64, No. 5
M Susa, J Hacker and R Marre
Legionella pneumophilia is a gram-negative rod which is able to multiply
within phagocytic cells. The process of phagocytosis leads to a rapid
environmental change that might require a coordinate regulation of gene
expression to ensure intracellular survival. Since there is little
information on up- and downregulation of genes during the early phases of
phagocytosis, we radiolabeled intracellular L. pneumophila at different
times after phagocytosis by macrophages of the Mono Mac 6 cell line and
immunoprecipitated antigens with antilegionella sera or monoclonal
antibodies. We could identify two antigens which were upregulated, one of
which was the Mip protein, three antigens which were downregulated, and
three antigens which were not detectable in extracellularly grown L.
pneumophila. The Mip protein was stained most intensively 4 to 8 h after
intracellular infection, suggesting that it is needed during intracellular
multiplication rather than initiation of infection. A 44-kDa antigen which
was not detectable during extracellular growth was most prominent from 2 to
4 h postinfection when Mono Mac 6 cells were used as phagocytic cells. The
44-kDa antigen was also expressed during growth with Acanthamoeba
castelanii, MRC-5, and U937 cells but with different kinetics. Synthesis of
this antigen was not dependent on protein synthesis of the host cell. Since
the 44- kDa antigen could be precipitated by an antiserum produced against
a recombinant Escherichia coli harboring a plasmid with an L. pneumophila
insert which also codes for the mip gene, we believe that the corresponding
gene is within the vicinity of the mip gene. We named this protein
legionella intracellular growth antigen (LIGA), since it could be found
exclusively in intracellularly grown L. pneumophila.
Copyright © 1996, American Society for Microbiology
De novo synthesis of Legionella pneumophila antigens during intracellular growth in phagocytic cells
Abteilung fur Medizinische Mikrobiologie und Hygiene, Universitat Ulm, Germany.
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