Modulation of a CD59-like protein in Naegleria fowleri amebae by bacteria

Found in soil and freshwater habitats, Naegleria fowleri are free-living amebae that cause a fatal disease in humans called Primary Amebic Meningoencephalitis. In the natural environment, amebae feed on bacteria. In the infected host, the amebae lyse and ingest nerve tissue. Recently, we have established that N. fowleri expresses a CD59-like surface protein, but the function of this protein in the ameba has not been elucidated. In mammalian cells, CD59 is a complement-regulatory protein that inhibits complement-mediated lysis of cells expressing this protein. In the present study, expression of the CD59-like protein in response to bacteria and bacterial toxins was investigated by Western immunoblot analysis. Co-culture of N. fowleri with log phase Escherichia coli or Pseudomonas aeruginosa resulted in differential expression of the CD59-like protein. Co-cultures of amebae and bacteria were examined by electron microscopy. The results of our study implicate a possible protective role of the CD59-like protein in response to bacterial predators and bacterial toxins, because amebae remained intact after co-culture with bacteria.