Isolation and characterization of a replication-competent molecular clone of an HIV-1 circulating recombinant form (CRF33_01B)

Potential Role of the Formation of Tunneling Nanotubes in HIV-1 Spread in Macrophages

Tunneling nanotubes (TNTs), the long membrane extensions connecting distant cells, have emerged as a novel form of cell-to-cell communication. However, it is not fully understood how and to what extent TNTs contribute to intercellular spread of pathogens including HIV-1. In this study, we show that HIV-1 promotes TNT formation per se via its protein Nef and a cellular protein M-Sec, which appears to mediate approximately half of viral spread among monocyte-derived macrophages (MDMs). A small compound that inhibits M-Sec-induced TNT formation reduced HIV-1 production by almost half in MDMs. Such inhibition was not observed with Nef-deficient mutant HIV-1 that fails to promote TNT formation and replicates less efficiently than the wild-type HIV-1 in MDMs. The TNT inhibitor-sensitive/Nef-promoting viral production was also observed in a T cell line ectopically expressing M-Sec, but not in another M-Sec(-) T cell line. Our results suggest the importance of TNTs in HIV-1 spread among MDMs and might answer the long-standing question how Nef promotes HIV-1 production in a cell type-specific manner.

Current Trends of HIV Recombination Worldwide

One of the major characteristics of HIV-1 is its high genetic variability and extensive heterogeneity. This characteristic is due to its molecular traits, which in turn allows it to vary, recombine, and diversify at a high frequency. As such, it generates complex molecular forms, termed recombinants, which evade the human immune system and so survive. There is no sequence constraint to the recombination pattern as it appears to occur at inter-group (between groups M and O), as well as interand intra-subtype within group M. Rapid emergence and active global transmission of HIV-1 recombinants, known as circulating recombinant forms (CRFs) and unique recombinant forms (URFs), requires urgent attention. To date, 55 CRFs have been reported around the world. The first CRF01_AE originated from Central Africa but spread widely in Asia. The most recent CRF; CRF55_01B is a recombinant form of CRF01_AE and subtype B, although its origin is yet to be publicly disclosed. HIV-1 recombination is an ongoing event and plays an indispensable role in HIV epidemics in different regions. Africa, Asia and South America are identified as recombination hot-spots. They are affected by continual emergence and cocirculation of newly emerging CRFs and URFs, which are now responsible for almost 20% of HIV-1 infections worldwide. Better understanding of recombinants is necessary to determine their biological and molecular attributes.

Two unique recombinant forms identified in incident HIV type 1 infections in Thai blood donors

HIV-1 genetic diversity of recently seroconverting (<12 months) Thai repeated blood donors attending the National Blood Centre, Thai Red Cross Society (NBC, TRCS) from September 2007 until March 2008 was assessed. Ten HIV-1 recent seroconvertors (10/239,134 donations) were identified during the study period. The estimated median time to seroconversion was 67.3 days (range: 45.5-102.0 days), and viral load ranged from 307 to 341,805 copies HIV-1 RNA/ml. MHAbce, a real-time-based PCR genotyping assay, identified six CRF01_AE, two CRF01_AE/B recombinants, one subtype B, and one CRF01_AE/B dual infection. Nine samples were further characterized by full genome sequencing, identifying CRF01_AE (N=6), unique CRF01_AE/B recombinants (N=2), and subtype B (N=1). One recombinant contained 13 breakpoints located in gag, pol, vif, vpr, env, and nef while the other recombinant contained 10 breakpoints located in pol, vif, env, and nef. This study found two unique CRF01B recombinants circulating in 10 recent HIV-1-positive subjects from a blood donor population in Thailand.

Parental LTRs are important in a construct of a stable and efficient replication-competent infectious molecular clone of HIV-1 CRF08_BC

Circulating recombinant forms (CRFs) of HIV-1 have been identified in southern China in recent years. CRF08_BC is one of the most predominant subtypes circulating in China. In order to study HIV subtype biology and to provide a tool for biotechnological applications, the first full-length replication-competent infectious molecular clone harboring CRF08_BC is reported. The construction of this clone pBRGX indicates that a moderate-copy number vector is required for its amplification in E. coli. In addition, it is shown that the parental CRF08_BC LTRs are important for generating this efficient replication-competent infectious clone. These observations may aid in the construction of infectious clones from other subtypes. Both the pBRGX-derived virus and its parental isolate contain CCR5 tropism. Their full-length genomes were also sequenced, analyzed, compared and deposited in GenBank (JF719819 and JF719818, respectively). The availability of pBRGX as the first replication-competent molecular clone of CRF08_BC provides a useful tool for a wide range of studies of this newly emergent HIV subtype, including the development of HIV vaccine candidates, antiviral drug screening and drug resistance analysis.