DOI: 10.1097/QAI.0b013e318053754c
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PMID: 17592338
Issn Print: 1525-4135
Publication Date: 2007/07/01
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Excerpt
One of the most significant biologic characteristics of HIV-1 is its broad genetic diversity, which is revealed by the existence of 3 groups (M, N, and O), various subtypes (A-D, F-H, J, and K) and sub-subtypes (A1-A4, F1, and F2), and numerous circulating recombinant forms (CRFs) or unique recombinant forms (URFs) within HIV-1 group M (Los Alamos HIV/AIDS Sequence Database, available at: http://hiv-web.lanl.gov). In areas where CRFs spread widely, second-generation recombinant viruses (SGRs) have been reported to contain the genetic material of at least 1 CRF. The extensive genetic variation, the heterogeneous geographic distribution of HIV-1, and, in particular, the continuous emergence of HIV-1 variants pose potential public health and clinical challenges. It is thus necessary to monitor the evolution of HIV-1 on an ongoing basis.
In 2002, we initiated a serologic survey in Douala and Yaoundé, Cameroon, where the pandemic infection of HIV-1 with broad genetic diversity and the natural reservoir of HIV-1 groups M and N have been identified. A total of 240 unlinked plasma samples were collected from 2 blood centers from urban areas in Douala and Yaoundé, Cameroon, and 135 samples were confirmed to be HIV-1-positive by US Food and Drug Administration (FDA)-licensed HIV diagnostic tests (results are to be published elsewhere). Eighty-eight HIV-1-positive samples were successfully amplified by polymerase chain reaction (PCR) and sequenced in gag (p17) and env (gp41) genes. In addition, 3 samples were sequenced in the gag (p17) gene only, and another 36 samples were sequenced in the env (gp41) gene only. The nucleotide sequences have been deposited in the GenBank under the following accession numbers: DQ056863 through DQ056984 (gp41) and DQ056985 through DQ057075 (p17). Phylogenetic analysis based on HIV-1 gag (p17) and env (gp41) sequences indicated that all analyzed sequences were classified as HIV-1 group M. HIV-1 group N or group O viruses were not found in these samples.
Table 1 summarizes the genotyping results and indicates that HIV-1 CRF02_AG was dominant (69% in gag, 72% in env, and 60% in gag/env, respectively) in our study, followed by HIV-1 subtypes (15% in gag, 10% in env, and 5.7% in gag/env, respectively) and CRFs or URFs (15% in gag, 18% in env, and 34% in gag/env, respectively). Aghokeng et al1 also reported that 74% of the HIV-1 strains collected from blood donors in 7 localities in Cameroon in 2001 were CRF02_AG based on the sequences of gp41 gene. The prevalence of HIV-1 CRF02_AG is much lower in the general population in Cameroon, however, where HIV-1 CRF02_AG was identified in 20% to 32% of HIV-1-infected persons.2,3 HIV-1 CRF02_AG is also less prevalent in the surrounding countries, such as Congo (2.7%) and Central African Republic (2.6%), although a relatively high prevalence of 26% has been reported in Gabon.4
We also included in our analysis the recently listed reference strains of CRF17 to CRF33 at the Web site of Los Alamos National Laboratory (available at: http://www.hiv.lanl.gov/content/hiv-db/CRFs/CRFs.html). We thus identified CRF19_cpx- and CRF22_01A1-like sequences in 2 and 7 samples in gag (p17) gene, 2 and 4 samples in env (gp41) gene, and 0 and 4 in gag/env genes, respectively. Within the phylogenetic trees, CRF19_cpx-like sequences clustered together to form a separate branch, which is close to the CRF02_AG cluster. The branch of CRF22_01A1-like sequences was closer to the CRF01_AE cluster, but the CRF22_01A1 and CRF01_AE clusters were within the subtype A group of HIV-1. The homology of these CRF22_01A1 sequences was 80% in gag (p17) and 85% in env (gp41), respectively.
