The Changing Molecular Epidemiology of HIV Type 1 among Northern Thai Drug Users, 1999 to 2002

Abstract

CRF01_AE and subtype B have dominated the HIV-1 epidemic in Thailand since 1989. We reported a new circulating recombinant form of HIV-1, CRF15_01B, as well as other unique CRF01_AE/B recombinants among prevalent HIV infections in Thailand. We sought to study this challenging molecular picture through assessment of subtypes among recent HIV-1 seroconverters in northern Thai drug users. A total of 847 HIV-1 seronegative drug users (342 IDU and 505 non-IDU) were enrolled, from 1999 to 2002, in a prospective study; 39 HIV-1 incident cases were identified and characteristics were collected. The overall HIV-1 incidence rate was 2.54/100PY, but it was 10.0/100PY among male IDU. HIV was strongly associated with injection history; 38 of 39 seroconverters gave a history of IDU. A near full-length genome of HIV-1 was recovered by PCR amplification and sequenced from peripheral mononuclear cell extracted DNA of 38 seroconverters. Phylogenetic analysis revealed that 33 (86.8%) were CRF01_AE and 5 (13.2%) were CRF01_AE/B recombinants. These recombinants had different structure but shared some common breakpoints, indicating an ongoing recombination process. Recombinant infection increased with year of sampling (0 to 57.1%). The molecular epidemiology of HIV-1 among drug users in northern Thailand has thus entered a new era. CRF01_AE remains predominant while pure subtype B is becoming rare, and now a substantial component of the epidemic. These findings support the need for CRF01_AE and subtype B components in clade-matched vaccine strategies for Thai phase III trials. Ongoing molecular surveillance of circulating HIV-1 strains is imperative for the evaluation of HIV vaccine efficacy.

Molecular Evolution of the HIV-1 Thai Epidemic between the Time of RV144 Immunogen Selection to the Execution of the Vaccine Efficacy Trial

“…First, it was noted that the withinsubtype interhost genetic divergence had increased significantly compared to that noted in earlier surveys (9,10,17,(22)(23)(24)(25). Second, the barriers that maintained the segregation of subtypes on the basis of risk factors started to efface; the representation of CRF01_AE among IDUs increased, especially among new infections (26), to the point where CRF01_AE accounted for 80 to 90% of the cases in Bangkok and the northern province of Chiang Mai (27,28). Coinfections (29) and superinfections (30) with subtype B and CRF01_AE were documented, and intersubtype recombinants were detected among individuals with either IDU (28,31) or heterosexual (32,33) exposure.…”

“…Second, the barriers that maintained the segregation of subtypes on the basis of risk factors started to efface; the representation of CRF01_AE among IDUs increased, especially among new infections (26), to the point where CRF01_AE accounted for 80 to 90% of the cases in Bangkok and the northern province of Chiang Mai (27,28). Coinfections (29) and superinfections (30) with subtype B and CRF01_AE were documented, and intersubtype recombinants were detected among individuals with either IDU (28,31) or heterosexual (32,33) exposure. While most of the recombinants were URFs, a new CRF, CRF15_01B, was found throughout the country among individuals with either risk factor, reinforcing the linkage between the different epidemics in Thailand (31,32).…”

HIV Recombination and Pathogenesis – Biological and Epidemiological Implications

“…Subtype A (sub-subtypes 1 and 2) strains are highly predominant in Kenya, with one study showing 93% of all strains found in the region being subtype A or a recombinant containing subtype A (Dowling et al, 2002). In addition, CRF01_AE is one of the major strains found in Thailand and Southeast Asia (McCutchan et al, 1992;Tovanabutra et al, 2004). Subsubtype A2 was first identified from sequences originating in the Democratic Republic of Congo and Cyprus (Gao et al, 2001), and is now also found in Kenya (Visawapoka et al, 2006).…”

Snapshot of HIV pathogenesis in China

“…Other South East Asian (SEA) countries, proximal to China, have also experienced similar epidemiological shifts, for example Thailand [18]. China is also no exception to this phenomenon and currently the Chinese HIV epidemic is dominated by high prevalence of a variety CRFs [7,19].…”