Ameobal pathogen mimivirus infects macrophages through phagocytosis.
Mimivirus, or Acanthamoeba polyphaga mimivirus (APMV), a giant double-stranded DNA virus that grows in amoeba, was identified for the first time in 2003. Entry by phagocytosis within amoeba has been suggested but not demonstrated. We demonstrate here that APMV was internalized by macrophages but not by non-phagocytic cells, leading to productive APMV replication. Clathrin- and caveolin-mediated endocytosis pathways, as well as degradative endosome-mediated endocytosis, were not used by APMV to invade macrophages. Ultrastructural analysis showed that protrusions were formed around the entering virus, suggesting that macropinocytosis or phagocytosis was involved in APMV entry. Reorganization of the actin cytoskeleton and activation of phosphatidylinositol 3-kinases were required for APMV entry. Blocking macropinocytosis and the lack of APMV colocalization with rabankyrin-5 showed that macropinocytosis was not involved in viral entry. Overexpression of a dominant-negative form of dynamin-II, a regulator of phagocytosis, inhibited APMV entry. Altogether, our data demonstrated that APMV enters macrophages through phagocytosis, a new pathway for virus entry in cells. This reinforces the paradigm that intra-amoebal pathogens have the potential to infect macrophages.
URMITE CNRS UMR 6236 - IRD 3R198, Université de la Méditerranée, Marseille, France.
Eric
E
Ghigo
Jürgen
J
Kartenbeck
Pham
P
Lien
Lucas
L
Pelkmans
Christian
C
Capo
Jean-Louis
JL
Mege
Didier
D
Raoult
D000656:Amoeba / Q000821:virology*; D000818:Animals; D004267:DNA Viruses / Q000472:pathogenicity*; D034285:Dynamin II / Q000502:physiology; D008264:Macrophages / Q000821:virology*; D010587:Phagocytosis; D010873:Pinocytosis; D053586:Virus Internalization
D034285:Dynamin II