Abstract
Limited information is available to describe the molecular epidemiology of HIV-1 in Bulgaria. To better understand the genetic diversity and the epidemiologic dynamics of HIV-1 we analyzed 125 new polymerase (pol) sequences from Bulgarians diagnosed through 2009 and 77 pol sequences available from our previous study from persons infected prior to 2007. Epidemiologic and demographic information was obtained from each participant and phylogenetic analysis was used to infer HIV-1 evolutionary histories. 120 (59.5%) persons were infected with one of five different HIV-1 subtypes (A1, B, C, F1 and H) and 63 (31.2%) persons were infected with one of six different circulating recombinant forms (CRFs; 01_AE, 02_AG, 04_cpx, 05_DF, 14_BG, and 36_cpx). We also for the first time identified infection with two different clusters of unique A-like and F-like sub-subtype variants in 12 persons (5.9%) and seven unique recombinant forms (3.5%), including a novel J/C recombinant. While subtype B was the major genotype identified and was more prevalent in MSM and increased between 2000–2005, most non-B subtypes were present in persons ≥45 years old. CRF01_AE was the most common non-B subtype and was higher in women and IDUs relative to other risk groups combined. Our results show that HIV-1 infection in Bulgaria reflects the shifting distribution of genotypes coincident with the changing epidemiology of the HIV-1 epidemic among different risk groups. Our data support increased public health interventions targeting IDUs and MSM. Furthermore, the substantial and increasing HIV-1 genetic heterogeneity, combined with fluctuating infection dynamics, highlights the importance of sustained and expanded surveillance to prevent and control HIV-1 infection in Bulgaria.
Highlights
The rapidly evolving human immunodeficiency virus type 1 (HIV-1) is characterized by enormous genetic heterogeneity and is divided phylogenetically into four major groups: M, N, O, and the recently identified group P from a crossspecies transmission from an SIV-infected gorilla [1]
The majority of persons (140 (69.3%)) attributed their infection to heterosexual contact, 34 (16.8%) were men who have sex with men (MSM), 19 (9.4%) were intravenous drug use (IDU), 5 (2.5%) persons were infected by blood transfusion and 4 (2%) newborns were infected by vertical transmission (Table 1)
High diversity of HIV-1 circulating in Bulgaria Phylogenetic analysis using maximum likelihood (ML) and Bayesian MCC methods of pol sequences classified 120 (59.5%) of the 202 Bulgarian HIV-1 samples to five different major subtypes (Figs. 1, 2, 3, 4, 5, 6, 7, Table 2). 104 (51.5%) were subtype B (Figs. 1 and 2), 7 (3.5%) subtype C, and 2 (1.0%) were subtype H (Fig. 3). 5 (2.5%) subtype A1, and 2 (1.0%) subtype F1 (Fig. 4)
Summary
The rapidly evolving human immunodeficiency virus type 1 (HIV-1) is characterized by enormous genetic heterogeneity and is divided phylogenetically into four major groups: M (major), N (new), O (outlier), and the recently identified group P from a crossspecies transmission from an SIV-infected gorilla [1]. Subtype B is predominant in the Americas, Western Europe, and Australia [3,4], subtype A prevails in Russia and the former Soviet Union (FSU) countries, and is prevalent in Africa. Subtype C is the most abundant genetic form in South and Eastern Africa, South East Asia, and worldwide followed by subtypes A and B. CRFs and URFs are widely distributed in countries where different subtypes co-circulate [5,6]. In Eastern Europe, Russia, Ukraine, Belarus and Moldova the HIV-1 epidemic is dominated by subtype A, followed by subtype B and CRF03_AB [7,8,9,10]. In the Baltic countries, subtype B predominates in Lithuania, subtype A1 is more common in Latvia, and the rare genetic form CRF06_cpx prevails in Estonia [11,12,13]
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