Lower prevalence of primary antiretroviral resistance among clade C infected individuals as compared to clade B in South Brazil’s emerging clade C HIV-1 epidemic
Background: A growing epidemic by clade C viruses is occurring in the south of Brazil. We sought to characterize the prevalence of primary HIV-1 resistance among newly diagnosed, ARV-naive HIV infected individuals in the epicenter of this south Brazilian clade C epidemic.
Methods: We studied 109 consecutive HIV positive samples collected from October 2006 to August 2007 at 4 anonymous HIV testing sites in Rio Grande do Sul, Brazil. HIV-1 pol regions were DNA sequenced, and infections were classified as recent or established infections according to the BED CEIA incidence assay (OD cutoff < 0.80).
Results: 15 out of 109 (13.7%) HIV+ individuals were classified as recently infected and 94 as established infections. 13.3% of those with recent infection and 7.2% of established infections presented ARV resistance to at least one antiretroviral class. According to pol sequences, 61.5% of individuals were infected by clade C viruses, 28.4% were infected by clade B, and 10.1% by non-B non-C strains, and proportions of recent infection were similar between clades. The prevalence of primary drug resistance was 9% among clade C infected vs. 22.6% among clade B infected, vs. 27% among non-B non-C infected individuals. The odds of resistance were significantly higher among HIV positives with subtype B and non-B non-C (p=0.03). 43% of patients with resistance mutations showed resistance to NRTI, 25% had TAMs, 25% had other NAMs, and 6.2% showed resistance to PIs.
Conclusions: In south Brazil, where clade C infections have overgrown clade B infections, clade C viruses show a lower prevalence of primary ARV resistance. These observations may be explained in part by more recent introduction of clade C to south Brazil; by less diagnosis or ARV use in populations affected by clade C (heterosexuals); and/or by biologic factors.
R.S. Diaz1, R.S. De Souza2, M.C. Sucupira1, E. Cavalieri1, K.M. Ribeiro3, L. Mondini4, K. Page-Shafer5, L.G.A. Borges2, M.P. Paganella2, C.D. Pilcher5
1Universidade Federal de São Paulo, São Paulo, Brazil, 2Laboratório de Pesquisa em HIV/AIDS, Universidade de Caxias do Sul, Caxias do Sul, Brazil, 3Serviço Especializado DST/AIDS Herbert de Souza, Viamão, Brazil, 4Hospital Sanatório Partenon, Porto Alegre, Brazil, 5University of California-San Francisco, San Francisco, United States