A marked decrease of HIV 1 viremia in a population of potential transmitters in the 1997-2007 interval reduced the proportion of acute seroconverters but minimally affected the transmission of drug resistance

BACKGROUND: HIV-1 viremia is a major determinant of HIV-1 transmission at population level. We analysed the relationship between viremia levels of drug-experienced patients as potential transmitters (PTs), number of HIV-1 seroconversions and transmitted drug resistance (TDR) in newly diagnosed drug-naive patients (NDs) by an ecological longitudinal study. METHODS: We evaluated 95,832 HIV-1 RNA results from 4,615 treated patients followed at ‘L. Sacco’ Hospital during 1997-2007. HIV-1 RNA levels and CD4 cells for these patients ranged from 1.69 to 6.63 Log cp/ml and from 0 to 988 cells/L. NDs, enrolled from 2002 to 2007, were 369, 103 of whom were seroconverters (SCs, 27.9%). HIV-1 RNA levels and CD4 cells for these patients ranged from 3.09 to 6.48 Log cp/ml and from 3 to 1,870 cells/L. Pol sequences were obtained either by commercial kits or an home-made procedure. Resistance mutations were identified from 2008 IAS-USA list. Differences among proportions and temporal trends were tested using the chi-square and the Cochran-Armitage test, respectively. RESULTS: PTs were 72.2% males; modality of infection was 37.8%, 34.9% and 22.6% for IDUs, HEs MSMs, respectively. By dividing the study period in 5 biennial intervals the proportions of patients below 3 Log HIV-1 RNA significant increased from 49.5%, 56.6%, 66.1%, 70.0% to 81.6% overtime (p<.0001). NDs were males in 83.7% of cases; MSMs and HEs represented 51.7% and 44.4% of cases, respectively. When considering three biennial intervals in the year period ‘02-’07 for ND patients, a significant SCs decrease could be detected (from 35.3% in ’02-’03 to 19.2% in ’06-’07, p=.0057). Among individuals with established infection, MSM risk factor and female gender rose, although not significantly, from 58.8% to 68.0% and from 9.3% to 17.1% in the same interval. No changes were observed regarding other characteristics. Overall, TDR was 12.2% (45/369; 18.4% in SCs and 9.7% in NDs), fluctuating from 15.2% to 10.9% and 11.5% in the study period. Of note, 67.4% (29/45) of patients with TDR were MSMs. No primary resistance was detected in female SCs, while it was 11.5% (3/26) in female with unknown duration of infection. Among individuals with TDR, MSMs were 83.3% (15/18) for SCs and 56% (14/25) for individuals with established infection. CONCLUSIONS: This surveillance of an Italian metropolitan area at high prevalence of HIV-1 infection indicates that first generation HAART, as well as new potent antiretroviral combinations, achieved a marked reduction of HIV-1 viremia, reducing the proportions of SCs among NDs overtime. Nonetheless, TDR in naïve patients remained at substantial level and clustered in males who acquired HIV-1 infection through sex with man, thus representing an ongoing public health concern.