Epidemiological network analysis in HIV-1 B infected patients diagnosed in Italy between 2000 and 2008

Annapaola Callegaro, Valentina Svicher, Claudia Alteri, Alessandra Lo Presti, Daniela Valenti, Antonio Goglio, Marco Salemi, Eleonora Cella, Carlo Federico Perno, Massimo Ciccozzi, Franco Maggiolo

Research output: Contribution to journalArticlepeer-review


This study, through a phylogenetic analysis, is aimed to identify potential epidemiological networks and sequence interrelationships between acute/early and chronic infections in both drug-naïve and drug-experienced individuals within a local, well-defined setting and to investigate the population dynamics of transmitted resistance and the potential contribution of untreated patients to the spread of antiretroviral resistance. A total of 884 HIV-1 B subtype pol gene sequences from 306 drug-naïve (40 recently and 266 chronically infected) and 578 drug-treated HIV-1 infected patients were collected through routine drug-resistance testing between 2000 and 2008 in a single center (Division of Infectious Disease, Bergamo, Northern Italy). Bayesian phylogenetic tree was reconstructed and transmission clusters were recognized using a posterior probability as statistical support of each cluster. Differences among clustered and non-clustered drug-resistance mutations were assessed by Fisher's exact test.In our cohort we identified five clusters including ≥6 sequences with the root posterior probability of 100%. Dated phylogenies reconstructed through Bayesian Markov chain Monte Carlo model was possible for only two main clade (≥10 sequences) originated between 1990 and 2002.Among the 306 drug-naïve individuals, 12% carried a viral strain with at least 1 major mutation associated with transmitted drug resistance and 36% of these strains were involved in significant clusters.We report for the first time that many (34%) of HIV-1 subtype B transmission clusters indentified in Italy were only composed by drug-naïve individuals and that the 14% of transmitted drug resistance was linked to transmission clusters composed only of newly diagnosed individuals. The phylogenetic analysis was performed on a large cohort of drug-naïve recently/chronically infected individuals where drug-experienced patients represent almost all infected individuals in a restricted geographical area.Our findings highlight the role of newly diagnosed individuals, not yet exposed to antiretroviral drugs, in the transmission of drug-resistant HIV-1 strains, providing new insights for the planning and management of treatment programs in developing countries.

Original languageEnglish
Pages (from-to)624-632
Number of pages9
JournalInfection, Genetics and Evolution
Issue number3
Publication statusPublished - Apr 2011


  • Epidemiological network
  • HIV-1 subtype B epidemic
  • Phylogenetic analysis
  • Time-scaled phylogenies
  • Transmitted drug-resistance (TDR)

ASJC Scopus subject areas

  • Ecology, Evolution, Behavior and Systematics
  • Genetics
  • Molecular Biology
  • Microbiology
  • Infectious Diseases
  • Microbiology (medical)


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