Background. Mimiviridae Mimivirus, including the largest known viruses, multiply in amoebae. Mimiviruses
have been linked to pneumonia, but they have never been isolated from patients. To further understand the pathogenic
role of these viruses, we aimed to isolate them from a patient presenting with pneumonia.
Methods. We cultured, on Acanthamoeba polyphaga amoebae, pulmonary samples from 196 Tunisian patients
with community-acquired pneumonia during the period 2009–2010. An improved technique was used for Mimivirus
isolation, which used agar plates where the growth of giant viruses is revealed by the formation of lysis plaques.
Mimivirus serology was tested by microimmunofluorescence and by bidimensional immunoproteomic analysis
using Mimivirus strains, to identify specific immunoreactive proteins. The new Mimivirus strain genome sequencing
was performed on Roche 454 GS FLX Titanium, then AB SOLiD instruments.
Results. We successfully isolated a Mimivirus (LBA111), the largest virus ever isolated in a human sample, from
a 72-year-old woman presenting with pneumonia. Electron microscopy revealed a Mimivirus-like virion with a size
of 554 +/- 10 nm. The LBA111 genome is 1.23 megabases, and it is closely related to that of Megavirus chilensis. Furthermore,
the serum from the patient reacted specifically to the virus compared to controls.
Conclusions. This is the first Mimivirus isolated from a human specimen. The findings presented above together
with previous works establish that mimiviruses can be associated with pneumonia. The common occurrence of
these viruses in water and soil makes them probable global agents that are worthy of investigation