Prevalence of HIV-1 Primary Drug Resistance in Seroconverters of the ICoNA Cohort Over the Period 1996???2001

To the Editor: Highly active antiretroviral therapy (HAART) has reduced HIV-1–related mortality and morbidity over the past few years, partially driving the epidemic evolution in developed countries. 1 Nevertheless, the use of antiretroviral therapy (ART) as part of suboptimal regimens in the pre-HAART era and a limited adherence to HAART caused a large development of HIV-1–resistant mutants. 2,3 These strains can potentially be transmitted to newly HIV-1–infected individuals, posing serious concerns about the efficacy of ART in these subjects. 4 Patients with unsuppressed viral load on HAART are likely to retain some degree of infectivity that may lead to the spread of resistant variants, particularly if coupled with increased risk behavior. 5 At present, knowledge regarding HIV-1 primary resistance indicates that the prevalence of transmitted resistant strains increased to substantial levels over the past few years, with a large variation, depending upon a number of factors. 6–8 Among them, the calendar period of the surveillance may be of crucial importance because the increasing prevalence of primary resistance has been detected during the early years of ART usage and a reduction has been observed after HAART introduction. 9,10 We studied 112 seroconverters who were enrolled in the Italian Cohort of Naive for Antiretrovirals (ICoNA) and had a resistance testing within 12 months of the estimated date of seroconversion. We estimated the prevalence of primary ART resistance and the temporal trend in transmission of ART-resistant strains before and after the impact of HAART on the control of HIV-1 replication at population level over the 1996–2001 period. Protease (PR) and reverse transcriptase (RT) mutations were defined as major or minor on the basis of the latest update of Recommendations of the International AIDS Society-USA panel. 11 We also studied the spread of non-B subtypes to ascertain whether their circulation has an impact on the transmission of primary resistance. 9 The phylogenetic and recombination analysis were performed using 85 reference sequences of HIV-1 M group (A-D, F-H, J, and K subtypes and 15 CRFs) by the PHYLIP package, version 3.5 (http://evolution.gs.washington.edu/phylip.html) and Simplot software, version 2.5 (www.med.jhu.edu/deptmed/sray). To evaluate the trend of prevalence of class-related drug resistance and non-B subtypes over the study period, we stratified the patients according to the year of seroconversion divided in biannual periods. The proportion of patients with undetectable viral load on therapy at various calendar years in all ICoNA seroconverters (564 patients) was calculated considering the viral load measurements closest to the date of June 30th of each year. Table 1 reports the demographics, the median values of laboratory markers, and the proportions of patients with drug resistance mutations according to the year of seroconversion.TABLE 1: Characteristics of the Study Population According to the Calendar Period of SeroconversionOverall, the genotypic analysis detected the presence of mutations associated with drug resistance in 18 patients (16.1%). Mutations in the RT and PR regions were detected in 15.2 and 2.7% of patients, respectively. Only 1 patient carried the mutation 103N related to non-nucleoside reverse transcriptase inhibitor resistance. Two patients (1.8%) had resistance to >1 class of ART. Nucleoside RT inhibitor–associated mutations (NAMs) were present in 11.6% of patients (n = 13). One and 2 NAMs were detected in 9 and 4 subjects, respectively. In addition, 2 patients with 41L mutation also had 215E or D changes and another patient had 215E alone. 12 The lamivudine-associated mutation 184V was present in only 1 patient. Three patients (2.7%) harbored HIV-1 variants with PR major mutations. HIV-1 drug resistance variants were comparable in men (17.6%) and in women (9.5%, P = 0.36). Analogously, the proportion of patients with resistant strains was similar irrespective of HIV modality: 17.4% among injection drug users, 21.6% among men who have sex with men (MSM), 11.1% among heterosexuals (HEs), and 14.3% among other modalities (n = 1) (P = 0.63). The proportion of all ICoNA patients on HAART having <500 copies/mL of HIV-1 RNA on therapy went from 48.9% in 1997 to 69.4 in 2000–2001. Over the same period, the prevalence of patients with drug-related mutations by calendar period of seroconversion first declined from 22.5% in 1996–1997 to 9.5% in 1998–1999 and then increased to 23.9% in 2000–2001 (P = 0.62). Table 1 shows the proportions of patients with RT and major protease inhibitor (PI) mutations by calendar years. A biphasic pattern was observed for nucleoside RT and PIs while the proportion of patients with polymorphic substitutions at positions 77, 36, 10, 71, and 63 remained stable in the study period. The phylogenetic analysis of 1229 bp of pol gene encompassing PR and RT regions revealed 4 pure non-B subtypes (F1, n = 3 and A, n = 1) and 4 recombinant variants (CRF02_AG, n = 3; CRF06_cpx, n = 1). All were white individuals. Non-B subtypes appeared to increase from 4.1% in 1996–1997 to 9.5% in 1998–1999 and 2000–2001 (P = 0.33). A significant association was found between the HE mode of infection and non-B subtypes (15.6% in HEs vs. 2.7% in MSMs; P = 0.04). When analyzing the distribution by gender, non-B subtypes were significantly more frequent in women (23.8%) than in men (3.3%) (P = 0.006). No RT or major PR mutations associated to resistance were detected in patients carrying non-B subtypes. Our data show a picture similar to that observed in other European countries and Australia. 9,10,13 In these other settings it has been suggested that the introduction of HAART may account for the initial decrease of primary resistance in individuals who seroconverted in the following years. A low viral load in treated subjects may be responsible for the reduction of transmitted resistance observed in the years 1998–1999 at population level. In the ICoNA study, the proportion of individuals with viral load suppressed to <500 copies/mL had increased from 1998–1999 to 2000–2001 and, concomitantly, the number of patients with drug resistance first decreased and then increased to previous levels in 2000–2001, mimicking a biphasic pattern. The observed reduction is in agreement with a theoretical approach according to which the main determinant of drug resistance transmission is the number of patients on failing therapy. 14 Some limitations were present in our analysis. Firstly, our results were obtained by studying the genotype of RNA-associated HIV-1 major species in subjects within 12 months from the estimated date of seroconversion. Secondly, a limited number of patients could be studied by us in the last 2 years, restricting the potency of our analyses. Our data suggest that currently there is no evidence that the rate of ART-resistant transmitted virus is increasing in Italy. Nevertheless, we cannot rule out that the duration of time spent with a non-suppressed viral load on therapy, the long-term toxicity of ART, and the limited adherence of patients to therapy will eventually lead to the selection of resistance in a larger number of HIV-1 patients, resulting in an increase in virus replication and, possibly, in primary transmitted resistance. Therefore, from a public health point of view, it is crucial that the rate of virologic failure on HAART and the rate of selection of HIV-1 resistance both in seroconverters and in treated individuals is constantly pursued at population level. Resistance testing of HIV-1–infected individuals at seroconversion may support these efforts. Members of the ICONA Study Group Cinelli. Bari: G. Pastore, N. Ladisa, G. Minafra. Bergamo: F. Suter, C. Arici. Bologna: F. Chiodo, V. Colangeli, C. Fiorini, O. Coronado. Brescia: G. Carosi, G.P. Cadeo, C. Torti, C. Minardi, D. Bertelli. Busto Arsizio: G. Rizzardini, G. Migliorino. Cagliari: P.E. Manconi, P. Piano. Catanzaro: T. Ferraro, A. Scerbo. Chieti: E. Pizzigallo, M. D'Alessandro. Como: D. Santoro, L. Pusterla. Cremona: G. Carnevale, D. Galloni. Cuggiono: P. Viganò, M. Mena. Ferrara: F. Ghinelli, L Ancona: M. Montroni, G. Scalise, A. Zoli, M.S. Del Prete. Aviano (PN): U. Tirelli, R.. Sighinolfi. Firenze: F. Leoncini, F. Mazzotta, M. Pozzi, S. Lo Caputo. Foggia: G. Angarano, B. Grisorio, A. Saracino, S. Ferrara. Galatina (LE): P. Grima, P. Tundo. Genova: G. Pagano, G. Cassola, A. Alessandrini, R. Piscopo. Grosseto: M. Toti, S. Chigiotti. Latina: F. Soscia, L. Tacconi. Lecco: A. Orani, P. Perini. Lucca: A. Scasso, A. Vincenti. Macerata: F. Chiodera, P. Castelli. Mantova: A. Scalzini, G. Fibbia. Milano: M. Moroni, A. Lazzarin, A. Cargnel, G.M. Vigevani, L. Caggese, A. d'Arminio Monforte, D. Repetto, R. Novati, A. Galli, S. Merli, C. Pastecchia, M.C. Moioli. Modena: R. Esposito, C. Mussini. Napoli: N. Abrescia, A. Chirianni, C. Izzo, M. Piazza, M. De Marco, R. Viglietti, E. Manzillo, M. Graf. Palermo: A. Colomba, V. Abbadessa, T. Prestileo, S. Mancuso. Parma: C. Ferrari, P. Pizzaferri. Pavia: G. Filice, L. Minoli, R. Bruno, S. Novati. Perugia: F. Baldelli, K. Loso. Pesaro: E. Petrelli, A. Cioppi. Piacenza: F. Alberici, A. Ruggieri. Pisa: F. Menichetti, C. Martinelli. Potenza: C. De Stefano, A. La Gala. Ravenna: G. Ballardini, E. Briganti. Reggio Emilia: G. Magnani, M.A. Ursitti. Rimini: M. Arlotti, P. Ortolani. Roma: R. Cauda, F. Dianzani, G. Ippolito, A. Antinori, G. Antonucci, S. D'Elia, P. Narciso, N. Petrosillo, V. Vullo, A. De Luca, L. Del Forno, M. Zaccarelli, R. Acinapura, P. De Longis, M. Ciardi, G. D'Offizi, M.P. Trotta, P. Noto, M. Lichtner, M.R. Capobianchi, E. Girardi, P. Pezzotti, G. Rezza. Sassari: M.S. Mura, M. Mannazzu. Torino: P. Caramello, A. Sinicco, M.L. Soranzo, L. Gennero, M. Sciandra, M. Bonasso . Varese: P.A. Grossi, C. Basilico . Verbania: A. Poggio, G. Bottari. Venezia: E. Raise, S. Pasquinucci. Vicenza: F. De Lalla, G. Tositti. Taranto: F. Resta, L. Cristiano. London, UK: A. Cozzi Lepri.