AcpA is a Francisella acid phosphatase that affects intramacrophage survival and virulence

Nrusingh P. Mohapatra, Ashwin Balagopal, Shilpa Soni, Larry S. Schlesinger, John S. Gunn

Research output: Contribution to journalArticlepeer-review

63 Scopus citations


AcpA of Francisella spp. is a respiratory-burst-inhibiting acid phosphatase that also exhibits phospholipase C activity. To better understand the molecular basis of AcpA in virulence, a deletion of acpA was constructed in Francisella novicida. The phosphatase and lipase activities were reduced 10-fold and 8-fold, respectively, in the acpA mutant compared to the wild type and were found mostly associated with the outer membrane. The acpA mutant was more susceptible to intracellular killing than the wild-type strain in the THP-1 human macrophage-like cell line. In addition, mice infected with the acpA mutant survived longer than the wild-type strain and were less fit than the wild-type strain in competition infection assays. Transmission electron microscopy showed that the acpA mutant was delayed in escape from macrophage phagosomes, as more than 75% of acpA mutant bacteria could still be found inside phagosomes after 12 h of infection in THP-1 cells and human monocyte-derived macrophages, whereas most of the wild-type bacteria had escaped from the phagosome by 6 h postinfection. Thus, AcpA affects intracellular trafficking and the fate of Francisella within host macrophages.

Original languageEnglish (US)
Pages (from-to)390-396
Number of pages7
JournalInfection and immunity
Issue number1
StatePublished - Jan 2007

ASJC Scopus subject areas

  • Parasitology
  • Microbiology
  • Immunology
  • Infectious Diseases


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