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Infection and Immunity, February 2006, p. 1352-1359, Vol. 74, No. 2
0019-9567/06/$08.00+0 doi:10.1128/IAI.74.2.1352-1359.2006
Copyright © 2006, American Society for Microbiology. All Rights Reserved.
Role of AFR1, an ABC Transporter-Encoding Gene, in the In Vivo Response to Fluconazole and Virulence of Cryptococcus neoformans 
Maurizio Sanguinetti,*
Brunella Posteraro,
Marilena La Sorda,
Riccardo Torelli,
Barbara Fiori,
Rosaria Santangelo,
Giovanni Delogu, and
Giovanni Fadda
Istituto di Microbiologia, Università Cattolica del Sacro Cuore, Rome, Italy
Received 28 June 2005/ Returned for modification 15 August 2005/ Accepted 22 November 2005
We have recently demonstrated that upregulation of the ATP binding cassette (ABC) transporter-encoding gene AFR1 in Cryptococcus neoformans is involved in the in vitro resistance to fluconazole of this yeast. In the present study, we investigated the role of AFR1 in the in vivo response to fluconazole in a mouse model of systemic cryptococcosis. Mice were infected with a wild-type fluconazole-susceptible strain of C. neoformans, strain BPY22; an afr1 mutant, BPY444, which displayed hypersusceptibility to fluconazole in vitro; or an AFR1-overexpressing strain, BPY445, which exhibited in vitro resistance to the drug. In each of the three groups, infected animals were randomly assigned to fluconazole treatment or untreated-control subgroups. As expected, fluconazole prolonged survival and reduced fungal tissue burdens (compared with no treatment) in BPY22- and BPY444-infected mice, whereas it had no significant effects in mice infected with BPY445. When the pathogenicities of these strains in mice were investigated, strain BPY445 was significantly more virulent than BPY22 following inhalational or intravenous inoculation, but mice infected with BPY444 survived significantly longer than BPY22-infected animals only when infection was acquired via the respiratory tract. In in vitro macrophage infection studies, strain BPY445 also displayed enhanced intracellular survival compared with strains BPY22 and BPY444, suggesting that its increased virulence may be due to its reduced vulnerability to the antimicrobial factors produced by phagocytic cells. These findings indicate that the upregulation of the AFR1 gene is an important factor in either determining the in vivo resistance to fluconazole or influencing the virulence of C. neoformans.
* Corresponding author. Mailing address: Istituto di Microbiologia, Università Cattolica del Sacro Cuore, Largo F. Vito 1, Rome 00168, Italy. Phone: 39 06 30154964. Fax: 39 06 3051152. E-mail: msanguinetti{at}rm.unicatt.it.
Supplemental material for this article may be found at http://iai.asm.org/.
Infection and Immunity, February 2006, p. 1352-1359, Vol. 74, No. 2
0019-9567/06/$08.00+0 doi:10.1128/IAI.74.2.1352-1359.2006
Copyright © 2006, American Society for Microbiology. All Rights Reserved.
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