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O20.1 The challenges of diversity: hiv-1 subtype distribution and transmission networks within the australian molecular epidemiology network-hiv 2005–2012
  1. A Castley1,
  2. S Sawleshwarkar2,
  3. R Varma2,
  4. B Herring2,
  5. K Thapa2,
  6. D Chibo3,
  7. N Nguyen4,
  8. K Hawke5,6,
  9. R Ratcliff5,6,
  10. DE Dwyer2,
  11. D Nolan1 The Australian Molecular Epidemiology Network-HIV (AMEN-HIV)
  1. 1Department of Clinical Immunology, Royal Perth Hospital, Perth WA 6000, Australia
  2. 2Western Sydney Sexual Health Centre and Centre for Infectious Diseases and Microbiology Laboratory Services, ICPMR-Pathology West, Westmead Hospital and University of Sydney, Westmead NSW 2145, Australia
  3. 3HIV Characterisation Laboratory, Victorian Infectious Diseases Reference Laboratory, North Melbourne, Victoria, 3051, Australia
  4. 4Division of Immunology, HSSA Pathology Queensland Central Laboratory, RBWH Herston, QLD 4029, Australia
  5. 5Clinic 275, Royal Adelaide Hospital, Adelaide, Australia
  6. 6Department of Microbiology and Infectious Diseases, SA Pathology, Adelaide South Australia


Introduction Rates of new HIV diagnoses are increasing in Australia, with evidence of an increasing proportion of non-B subtypes reflecting a growing impact of sexual networks, migration and travel. This present study aims to further define HIV-1 subtype diversity and investigate HIV-1 transmission networks within Australia.

Methods The Australian Molecular Epidemiology Network (AMEN) HIV collaborating sites in Western Australia, South Australia, Victoria, Queensland and Western Sydney, provided baseline HIV-1 partial pol sequence, age and gender information for a total of 4929 patients during 2005–2012. HIV-1 phylogenetic analyses utilised MEGA V6, with a stringent classification of transmission clusters (bootstrap ≥98%, genetic distance ≤1.5%).

Results HIV-1 B subtype represented 74.9% of 4929 sequences (WA 59.3%, SA 68.6%, W Syd 75.2%, Vic 75.7%, Qld 82.3%), with a greater proportion of clusters compared to non-B subtypes (27.6% vs 22.4% of sequences, p = 0.003), larger cluster size (36.0% with >2 sequences vs 24.8% of non-B clusters, p = 0.03) and more male-only groups (90%). The largest cluster comprised 29 B subtype sequences from Vic + WA (age range 23–70 years). HIV-1 subtype C networks (38 groups) included more female/male groups (73.6%) and a smaller proportion of groups >2 (16%), while CRF01_AE networks (44 groups) included 59.1% male-only groups, with groups >2 accounting for 22.7%.

Conclusion This nationwide study of HIV-1 sequences involving 4929 patients’ highlights the increasing diversity of HIV-1 subtypes within the Australian epidemic, as well as differences in transmission networks within Australia that are associated with these HIV-1 subtypes. These findings provide epidemiological insights not readily available using standard surveillance methods and can inform the development of effective strategies for prevention of new HIV-1 diagnoses across Australian state boundaries.

Disclosure of interest statement None declared.

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