Diverse BF recombinants have spread widely since the introduction of HIV-1 into South America

Single Nef proteins from HIV type 1 subtypes C and F fail to upregulate invariant chain cell surface expression but are active for other functions

HIV-1 Nef protein plays a major role in viral immunopathogenesis, modulating surface expression of several immune receptors, altering signal transduction pathways, and enhancing viral infectivity, among other activities. Nef also exhibits great intersubtype diversity, but most studies have been focused only on Nef proteins from subtype B. Thus, little is known about the functional capacities of nonsubtype B Nef proteins in host cells. Here, we investigated cell surface regulation of MHC-I, MHC-II, the MHC-II-associated chaperone invariant chain (Ii), CD4, CD3, and CD28 in cells transfected or infected with five different Nef alleles including one HIV-1 subtype C and F allele. No significant difference among the Nef proteins regarding CD3, CD28, and MHC-II downregulation was observed. The NefC showed a slightly, yet significant, diminished capacity to downregulate MHC-I in all cells, as well as to downregulate CD4 in Jurkat cells and PBMCs. Strikingly, the two alleles from NefC and NefF were unable to upregulate the Ii chain both in transfected and infected cells. Moreover, the internalization rate of the surface Ii chain was only slightly affected by NefC and NefF, whereas it was drastically reduced by NefB. Nef domains known to be involved in Ii chain upregulation were conserved among the five alleles analyzed here. In summary, we identified two primary HIV-1 NefC and NefF alleles that are selectively impaired for Ii upregulation and that may help to elucidate the mechanism of this Nef function in the future. It will be important to determine whether the observed differences are HIV-1 subtype dependent and influence viral immunopathogenesis.

Genetic variability of human immunodeficiency virus-1 in Bahia state, Northeast, Brazil: high diversity of HIV genotypes

The HIV-1 genetic variability in Bahia state, Brazil, was investigated. DNA samples from 229 and 213 HIV-1-infected individuals were analyzed using the heteroduplex mobility assay (HMA) in gag and env fragments, respectively. One hundred seventy-five samples were characterized in both genes. Thirty-two subtype F and BF recombinant viruses were sequenced and analyzed by phylogenetic methods. The combination of HMA and sequencing results showed that seven different HIV-1 genotypes comprised this sample: 147 (84%) B/B, 4 (2.3%) F/F, 3 (1.7%) B/F, 1 (0.6%) F/B, 1 (0.6%) F/D, 1 (0.6%) BF/F, and 18 (10.3%) BF/B. A significant divergence was observed between these two techniques results (84.4%). This is explained by the low accuracy of the HMA for detecting recombinant viruses. These recombinants were unrelated to CRF12, while two sequences were related to CRF28 and CRF29. Nineteen BF mosaics shared the same gag breakpoint. In conclusion, the use of HMA may be inappropriate in regions where different subtypes are co-circulating. Subtype B is the most common genotype, however, an increased prevalence (13.1%) of different BF variants and a potentially new CRF suggest that recombination is occurring frequently in Bahia. These viruses were associated with women infected heterosexually. Finally, this study identified the presence of an F/D recombinant HIV-1 in Brazil.

Lack of viral selection in human immunodeficiency virus type 1 mother-to-child transmission with primary infection during late pregnancy and/or breastfeeding

Mother-to-child transmission (MTCT) of human immunodeficiency virus type 1 (HIV-1) as described for women with an established infection is, in most cases, associated with the transmission of few maternal variants. This study analysed virus variability in four cases of maternal primary infection occurring during pregnancy and/or breastfeeding. Estimated time of seroconversion was at 4 months of pregnancy for one woman (early seroconversion) and during the last months of pregnancy and/or breastfeeding for the remaining three (late seroconversion). The C2V3 envelope region was analysed in samples of mother-child pairs by molecular cloning and sequencing. Comparisons of nucleotide and amino acid sequences as well as phylogenetic analysis were performed. The results showed low variability in the virus population of both mother and child. Maximum-likelihood analysis showed that, in the early pregnancy seroconversion case, a minor viral variant with further evolution in the child was transmitted, which could indicate a selection event in MTCT or a stochastic event, whereas in the late seroconversion cases, the mother's and child's sequences were intermingled, which is compatible with the transmission of multiple viral variants from the mother's major population. These results could be explained by the less pronounced selective pressure exerted by the immune system in the early stages of the mother's infection, which could play a role in MTCT of HIV-1.

Short communication: Molecular characterization of HIV type 1 BF pol recombinants from São Paulo, Brazil

In the Brazilian HIV-1 epidemic, subtypes B, C, and F1 are cocirculating in the population. Sequences of the partial pol gene from 463 HIV-1-infected patients were obtained from plasma samples and viral subtype was characterized. BF recombinants were found in 8% of the samples. Fifteen different patterns were observed. A CRF28_BF and CRF29_BF structure was found in 29.7% of the samples, CRF12_BF in 13.5%, and CRF39_BF in 2.7%. Two other patterns were identified in each of three samples. These findings could indicate a new CRF description, but to determine this a full length study is required.

StepBrothers: inferring partially shared ancestries among recombinant viral sequences

Phylogeneticists have developed several statistical methods to infer recombination among molecular sequences that are evolutionarily related. Of these methods, Markov change-point models currently provide the most coherent framework. Yet, the Markov assumption is faulty in that the inferred relatedness of homologous sequences across regions divided by recombinant events is not independent, particularly for nonrecombinant sequences as they share the same history. To correct this limitation, we introduce a novel random tips (RT) model. The model springs from the idea that a recombinant sequence inherits its characters from an unknown number of ancestral full-length sequences, of which one only observes the incomplete portions. The RT model decomposes recombinant sequences into their ancestral portions and then augments each portion onto the data set as unique partially observed sequences. This data augmentation generates a random number of sequences related to each other through a single inferable tree with the same random number of tips. While intuitively pleasing, this single tree corrects the independence assumptions plaguing previous methods while permitting the detection of recombination. The single tree also allows for inference of the relative times of recombination events and generalizes to incorporate multiple recombinant sequences. This generalization answers important questions with which previous models struggle. For example, we demonstrate that a group of human immunodeficiency type 1 recombinant viruses from Argentina, previously thought to have the same recombinant history, actually consist of 2 groups: one, a clonal expansion of a reference sequence and another that predates the formation of the reference sequence. In another example, we demonstrate that 2 hepatitis B virus recombinant strains share similar splicing locations, suggesting a common descent of the 2 viruses. We implement and run both examples in a software package called StepBrothers, freely available to interested parties.

Epidemiological and molecular characteristics of HIV-1 infection among female commercial sex workers, men who have sex with men and people living with AIDS in Paraguay

An HIV seroprevalence and molecular study was conducted among 935 subjects: 723 female commercial sex workers, 92 men who have sex with men and 120 HIV-positive volunteers. The reported injection drug use rates were 0.7% in female commercial sex workers and 3% in men who have sex with men. Sexually transmitted infections were reported in 265 (37%) of the female commercial sex workers and 38 (41%) of the men who have sex with men. A total of 20 (2.8%) female commercial sex workers and 12 (13%) men who have sex with men became HIV infected during the study period. A history of sexually transmitted infection increased the risk of subsequent HIV infection twofold (adjusted odds ratio of 2.5) among the female commercial sex workers, while cocaine use had an adjusted odds ratios of 6.61 among men who have sex with men. From 130 samples, and based on heteroduplex mobility assaying for the env gene, with sequencing of part of pol and/or full genomes, subtype B was the predominant subtype identified (66%); followed by subtype F (22%) and subtype C (4%). Recombinant CRF12-BF strains were identified in 6% and CRF17_BF was identified in 2%.

Human immunodeficiency virus and tuberculosis in Argentina: prevalence, genotypes and risk factors

The objective of this study was to determine the prevalence and genetic variability of human immunodeficiency virus type 1 (HIV-1) and other sexually transmitted infections (STIs) among 205 patients with clinical diagnosis of tuberculosis (TB) in Buenos Aires in 2001. Infections with hepatitis B virus (HBV), HIV-1, hepatitis C virus (HCV), Treponema pallidum and human T-cell lymphotropic virus types I/II were diagnosed in 37/187 (19.8 %), 35/205 (17.1 %), 22/187 (11.8 %), 13/187 (7.0 %) and 4/181 (2.2 %) patients, respectively. Almost one in three participants (33.1 %) presented at least one infection in addition to TB. Multiresistance to TB drugs (isoniazid plus rifampicin) was detected in the isolates recovered from three patients. Injecting drug use was detected as the main risk factor for HIV, HBV and HCV infections. Of ten patients who died, eight were infected with HIV. HIV genetic characterization showed the presence of two different subtypes. Env subtype F was found in 13/24 samples (54.2 %) and subtype B in 11/24 samples (45.8 %) by heteroduplex mobility assay. Sequencing of the protease/RT region was performed in ten samples: three were characterized as subtype B and seven as B/F recombinants by bootscanning analysis. Phylogenetic analysis of four full-length sequences showed that three were the circulating recombinant form CRF12_BF. The results of this study suggest an urgent need to detect HIV infection in high-risk groups to prevent future HIV transmission as well as morbidity and mortality associated with TB by providing highly active antiretroviral therapy (HAART) and/or TB treatment. Collaboration between TB and HIV programmes seems to be the best approach to decrease the incidence of these diseases, especially in high-prevalence HIV settings.

Magnitude, breadth, and functional profile of T-cell responses during human immunodeficiency virus primary infection with B and BF viral variants

The molecular pattern of the human immunodeficiency virus (HIV) epidemic in Argentina provides an appropriate scenario to study cellular immune responses in patients with non-clade B infection. We aimed to map T-cell responses in patients infected with BF recombinant variants and compare them with those of clade B patients. Sixteen recently infected patients were enrolled and grouped by viral subtype. Nef-specific responses were evaluated with a peptide matrix-based gamma interferon (IFN-gamma) enzyme-linked immunospot (ELISPOT) assay using B and BF overlapping peptides. Cross-clade and clade-specific responses were found. A correlation between B versus BF Nef-specific responses was identified. Detailed analysis at the single-peptide level revealed that BF patients show a narrower response but greater magnitude. Nef immunodominant responses agreed with previous publications, although the B loop was targeted at an unexpectedly high frequency. The putative HLA allele(s) restricting each positive response was determined. Single-peptide level screening with two different peptide sets uncovered discordant responses (mostly caused by peptide offsetting) and allowed detection of increased breadth. Positive responses identified by ELISPOT assay were further studied by intracellular cytokine staining. These were almost exclusively mediated by CD8 T cells. Characterization of concordant responses revealed that cells show distinct functional profiles, depending on the peptide presented. Last, quality (in terms of polyfunctionality) of T cells was associated with better viral replication containment. Overall, interclade differences in the frequency of epitopes recognized, structural domains targeted, and magnitude of responses were identified. Screening T-cell responses with multiple sets increased sensitivity. Further support for the notion of polyfunctional CD8(+) T-cell requirement to better control viral replication is also provided.

HIV type 1 genetic variability in central Brazil

This study analyzed the genes pol and env to determine the genetic variability of HIV-1 in Central Brazil. Forty-one isolates of HIV-1-infected individuals had protease, reverse transcriptase, and C2C3/ env amplified by nested PCR and sequenced. The subtype was determined by the program REGA and phylogenetic analyses. The samples identified as putative recombinant forms were analyzed by SimPlot. A high prevalence of subtype B (95.1%) was observed, followed by mosaic viruses B/F (4.9%). The amino acid sequences from 30 HIV-1 isolates were analyzed for the antigenic intrasubtype diversity. The most prevalent gp120 V3 loop motif was the GPGR (United States/Europe) (43.3%), described in B and F subtypes, followed by the GPGK tetrapeptide (10%). The Brazilian variant B" (GWGR), GFGR, and GLGR tetrapeptides were found in 6.7%. Other V3 variants were found in eight isolates (26.7%). Phylogenetic tree analysis was also performed in order to verify the relationship of the HIV-1 samples from Central Brazil with other HIV-1 sequences that circulate in Brazil. The subtype B sequences from Central Brazil formed a polyphyletic cluster in the tree, indicating that these strains are similar to those from other geographic regions. These results contribute to the understanding of HIV in Brazil, and may prove useful for the development of vaccine candidates.

HIV type 1 subtype C and CB Pol recombinants prevail at the cities with the highest AIDS prevalence rate in Brazil

HIV-1 B is predominant in Brazil, but HIV-1 C has increasingly been reported in the south of the country. However, many samples clustering with clade C are actually a recombinant, with a small B segment at RT (CRF31). Samples (209) from the three cities with the highest aids prevalence rate are analyzed. Partial polymerase sequences from HIV RNA made it possible to determine HIV clades and recombination patterns and to identify primary drug resistance mutations (DRMs). The incidence was estimated with a BED assay. HIV-1 C and CRF31 patterns were twice as frequent as clade B at all sites, but the proportion of C and CRF31 patterns was significantly different among sites. The incidence estimate for SC was 2.6 persons-years. Infection in recent or younger cases showed no association with clade C. Surveillance DRM was observed in 8.3% (95% CI 5-13), mostly to NNRTIs. Clade F pol genomes had significantly more primary DRM.

Buenos Aires cohort of men who have sex with men: prevalence, incidence, risk factors, and molecular genotyping of HIV type 1

The prevalence, incidence, risk factors, and molecular genotyping of HIV-1 infection among men who have sex with men (MSM) were assessed through a prospective cohort study. The study was conducted in Buenos Aires from February 2003 to December 2004. Sociodemographic, sexual risk behavior data, and blood samples for HIV testing were collected at baseline and at 6 and 12 months. Cox regression analysis was applied to determine risk factors associated with HIV seroconversion. HIV-positive samples were analyzed by partial (pro/RT) and full-length genome sequencing. Of 811 HIV-negative participants evaluated at baseline, 327 volunteers that fulfilled the inclusion criteria were enrolled. Retention rates at 6 and 12 months were 97.2% and 91.5%, respectively. Twelve MSM seroconverted for HIV infection [incidence rate = 3.9 (95% CI = 2.0-6.7) per 100 person-years]. HIV seroconversion was associated with a greater number of different sexual contacts in the preceding 6 months (> or =10, hazard ratio = 3.3, 95% CI: 1.1-10.4). By partial pro/RT genotyping analysis, 83% HIV-positive samples were subtype B and 17% samples were BF recombinants, most of these being unique recombinant forms. This study describes for the first time the recruitment and follow-up of a cohort of MSM in Argentina. Retention rates and HIV incidence rate were high. These data should be considered as a promising potential population for HIV vaccine trials.

Description of the first full-length HIV type 1 subtype F1 strain in Argentina: implications for the origin and dispersion of this subtype in South America

HIV-1 subtype F1 in South America is mainly found as part of diverse BF1 recombinant forms and only five full-length "pure" F1 strains from Brazil were characterized to date. In the present study we describe the first near full-length sequence of a nonrecombinant F1 HIV-1 strain from Argentina, and explore the epidemiological history of this subtype in South America. Three separate phylogenetic analyses were carried out: with all available F1 full-length sequences, with concatenated F1 sequences contained in F1 and BF1 strains, and with partial F1 env sequences derived from worldwide strains. All analyses were consistent in showing a local origin of the newly reported Argentine subtype F1 strain, and a common ancestry of the South American subtype F1 sequences, present either in pure or recombinant genomes. By coalescent analysis, the onset date of the HIV-1 subtype F1 epidemic in South America was estimated to be around the late 1970s. The results indicate for the first time that nonrecombinant F1 HIV-1 strains are present in Argentina, and suggest that the subtype F1 epidemic in South America was initiated by the introduction of a very small group of genetically related viruses during late 1970s.

HIV type 1 genetic diversity surveillance among newly diagnosed individuals from 2003 to 2005 in Buenos Aires, Argentina

To perform a diversity surveillance study we characterized viral subtypes among newly diagnosed individuals in Buenos Aires city. Plasma samples were collected from 322 drug-naive newly diagnosed HIV-1 individuals attending two voluntary counseling and testing centers. Sequences of pol and vpu genes were obtained from 283 samples and viral subtype was characterized by Neighbor-joining trees and Bootscanning analysis. BF recombinants were found in 56.9% followed by subtype B strains (39.2%). CRF12_BF structure was found in 27% of BF while another 27% had that structure only in one of both genes analyzed. Unusual non-B-non-BF strains were found in 3.9% (11/283). They were further analyzed by database searching and maximum likelihood trees in order to track their origin. Two subtype C sequences were found to be related to South American isolates while another two subtype C sequences and the subtype C segment of a BC recombinant were found to be related to isolates from Senegal. We also identified the CRF16_A2D previously found in Argentina and the CRF06_cpx commonly prevalent in Africa. The B segment of a BD recombinant was also found to be related to the Argentinean Bs suggesting a recombination between an African and a local strain. We also found a BK and two BA recombinants. In conclusion, CRF16_A2D and a new line of subtype C (of Senegalese origin) seem to be successfully established and are now spreading in Buenos Aires. BF recombinants keep recombining with local strains losing the CRF12_BF structure. Altogether they are changing the diversity of HIV in Argentina.

High genetic variability of HIV-1 in female sex workers from Argentina

Background

A cross-sectional study on 625 Female Sex Workers (FSWs) was conducted between 2000 and 2002 in 6 cities in Argentina. This study describes the genetic diversity and the resistance profile of the HIV-infected subjects.

Results

Seventeen samples from HIV positive FSWs were genotyped by env HMA, showing the presence of 9 subtype F, 6 subtype B and 2 subtype C. Sequence analysis of the protease/RT region on 16 of these showed that 10 were BF recombinants, three were subtype B, two were subtype C, and one sample presented a dual infection with subtype B and a BF recombinant. Full-length genomes of five of the protease/RT BF recombinants were also sequenced, showing that three of them were CRF12_BF. One FSW had a dual HIV-1 infection with subtype B and a BF recombinant. The B sections of the BF recombinant clustered closely with the pure B sequence isolated from the same patient. Major resistance mutations to antiretroviral drugs were found in 3 of 16 (18.8%) strains.

Conclusion

The genetic diversity of HIV strains among FSWs in Argentina was extensive; about three-quarters of the samples were infected with diverse BF recombinants, near twenty percent had primary ART resistance and one sample presented a dual infection. Heterosexual transmission of genetically diverse, drug resistant strains among FSWs and their clients represents an important and underestimated threat, in Argentina.

Human immunodeficiency virus type-1 subtypes of infected patients in Espírito Santo, Brazil

Genetic variability of human immunodeficiency virus type-1(HIV-1) is a potential threat for both diagnosis and treatment of HIV/AIDS, as well as the development of effective vaccines. Up to now, HIV subtypes circulating among HIV-positive patients in the state of Espírito Santo were not known. In the present study, blood samples from 100 therapy-naïve HIV-1 infected patients were collected and the HIV subtype was determined through the Heteroduplex Mobility Assay (HMA). Ninety-seven out of 100 studied samples were subtyped by HMA, 73 samples (75.2%) were from subtype B, 9 (9.3%) from subtype F, 3 (3.1%) from subtype C, 6 (6.2%) Benv/Fgag, and another 6 (6.2%) Fenv/Bgag, what suggests that recombinant viruses were present in the studied samples. Twenty-eight percent of the subtype B samples were represented by the Brazilian B" subtype, which were identified by RFLP with Fok I. Data presented here demonstrate that the epidemiological characteristics of the HIV epidemic in the state of Espírito Santo are similar to those from the other Southeastern states and helped to better understand the genetic polymorphism of HIV in Brazil.

HyperPack: a software package for the study of levels, contexts, and patterns of APOBEC-mediated hypermutation in HIV

G-to-A hypermutation, a massive substitution of G for A, was first observed in HIV genomes 15 years ago. Initially ascribed to fluctuating nucleotide pools or PCR errors, it has now been recognized as the result of an important host-defense mechanism mediated by APOBECs, a family of sequence-specific cytidine deaminases. Levels of hypermutation vary, and APOBECs have different preferences for the sequence context of cytidines targeted for deamination; analysis of hypermutation provides important information about the host-virus interaction during viral replication. Here we present HyperPack, a software package to support systematic characterization of hypermutated sequences. Users can define the context of substitution for independent study of the effects of different APOBECs. The SubstrateScan and HyperScan modules are overlapping sliding-window strategies to analyze the distribution of targeted motifs and their substitution levels, respectively, across the viral genome. HyperPack is a platform-flexible, Java stand-alone application available through http://www.hivresearch.org/hyperpack/.

Antiretroviral drug resistance and phylogenetic diversity of HIV-1 in Chile

This study reports the analysis of human immunodeficiency virus type 1 (HIV-1) protease (PR) and reverse transcriptase (RT) coding sequences from 136 HIV-1-infected subjects from Chile, 66 (49%) of them under antiretroviral (ARV) treatment. The prevalence of mutations conferring high or intermediate resistance levels to ARVs was 77% among treated patients and 2.5% among drug-naïve subjects. The distribution of resistance prevalence in treated patients by drug class was 61% to nucleoside RT inhibitors, 84% to nonnucleoside RT inhibitors, and 46% to PR inhibitors. Phylogenetic analysis revealed that 115 (85%) subjects were infected with subtype B viruses, 1 with a subtype F1 virus, and 20 (15%) carried BF intersubtype recombinants. Most BF recombinants grouped into two clusters, one related to CRF12_BF, while the other could represent a new circulating recombinant form (CRF). In conclusion, this is the first report analysing the prevalence of ARV resistance which includes patients under HAART from Chile. Additionally, phylogenetic analysis of the PR-RT coding sequences reveals the presence of BF intersubtype recombinants.

Examination of real-time PCR for HIV-1 RNA and DNA quantitation in patients infected with HIV-1 BF intersubtype recombinant variants

The impact of HIV-1 genetic diversity on the performance of laboratory testing is an issue that has to be monitored continuously. An "in-house" real-time PCR assay was developed by the Agence Nationale de Recherche sur le SIDA (ANRS) in France for viral load (VL) quantitation based on the amplification of the HIV-1 long terminal repeat (LTR) region. This technology has not been used in Argentina yet and considering the HIV-1 diversity in the country, a comparative analysis of this assay was undertaken versus the Versant HIV-1 RNA 3.0 Assay (b-DNA). The performance was assessed on 30 drug-naïve HIV-1 infected patients who were characterized previously by phylogenetic analysis of the pol and vpu gene. The results showed that there is a significant linear correlation between values of transformed viral load logarithms measured by both, bDNA and real-time PCR assay and that this assay can be used to quantify viral load in samples from BF-infected patients with the same accuracy and reliability as for B subtype samples. The use of "in-house" real-time PCR to measure DNA in PBMCs correlated strongly with the HIV-1 RNA levels in all specimens.

Analysis of HIV type 1 diversity in pregnant women from four Latin American and Caribbean countries

Worldwide, the distribution of HIV-1 subtypes and intersubtype recombinants is not homogeneous. In Latin America and the Caribbean, HIV-1 subtype B predominates. However, in the south of Brazil and in countries of the Southern cone (Argentina, Chile, Paraguay, and Uruguay) there is a different distribution of viral subtypes and intersubtype recombinants. The aim of this work was to analyze HIV-1 diversity in a cohort of pregnant women (with primarily heterosexual acquisition of the infection) who were diagnosed with HIV-1 infection during their current pregnancy and who received ARVs during pregnancy for perinatal transmission prophylaxis. Analysis of 121 partial pol sequences from subjects enrolled in Argentina, Brazil, the Bahamas, and Mexico was performed by phylogenetic and recombinant characterization. Different prevalences of subtype B were observed (100% for specimens from Mexico and the Bahamas, 61% for Brazil, and 30% for Argentina). Subtypes C and F were found, along with BC, BF, FC, and CBF recombinants in specimens from Brazilians. A high prevalence of BF recombinants was found (70%) in specimens from Argentina. The different patterns of HIV- 1 subtypes and intersubtype recombinants in South America (Argentina and Brazil) compared to those in Central and North America should be considered in the design of future HIV-1 vaccine trials.

Extremely rapid spread of human immunodeficiency virus type 1 BF recombinants in Argentina

The epidemic of human immunodeficiency virus type 1 (HIV-1) in Argentina is distinctive in that many infections are caused by subtype BF recombinant viruses. To determine their demographic history, we estimated the evolutionary rate, mode of population growth, and age of genetic diversity among 40 BF vpu sequences. This revealed one of the highest substitution rates reported for HIV-1, at 10.793 x 10(-3) substitutions per site per year, and a very rapid rate of population growth, with an initial mean epidemic doubling time of 3.72 months. This rapid population growth is compatible with an elevated fitness for subtype BF compared to that for "pure" B and F viruses.

First report of an HIV-1 triple recombinant of subtypes B, C and F in Buenos Aires, Argentina

We describe the genetic diversity of currently transmitted strains of HIV-1 in men who have sex with men (MSM) in Buenos Aires, Argentina between 2000 and 2004. Nearly full-length sequence analysis of 10 samples showed that 6 were subtype B, 3 were BF recombinant and 1 was a triple recombinant of subtypes B, C and F. The 3 BF recombinants were 3 different unique recombinant forms. Full genome analysis of one strain that was subtype F when sequenced in pol was found to be a triple recombinant. Gag and pol were predominantly subtype F, while gp120 was subtype B; there were regions of subtype C interspersed throughout. The young man infected with this strain reported multiple sexual partners and sero-converted between May and November of 2004. This study reported for the first time the full genome analysis of a triple recombinant between subtypes B, C and F, that combines in one virus the three most common subtypes in South America.

Global epidemiology of HIV

HIV is among the most generically variable of human pathogens. A comprehensive and detailed description of HIV strains in the pandemic is an important foundation for diagnosis, treatment, and prevention. The current sequence database for HIV includes almost 800 complete genome sequences, documenting HIV-1 groups M, O, and N, and HIV-2. Among HIV-1 group M strains, responsible for the vast majority of HIV infections worldwide, 743 sequences represent 9 genetic subtypes, 16 circulating recombinant forms (CRF) that are spreading in populations, and a variety of unique recombinant forms (URF), identified so far only from a single individual. The global distribution of HIV is complex and dynamic with regional epidemics harboring only a subset of the global diversity. HIV strains differ enormously in terms of global prevalence. Six strains account for the majority of HIV infections: HIV-1 subtypes A, B, C, D, and two of the CRF, CRF01-AE and CRF02_AG, respectively. Many of the known subtypes and recombinant forms are currently rare in the epidemic, but could spread more widely if favorable conditions arise. HIV-2 is largely restricted to West Africa at relatively low prevalence there. Groups O and N of HIV-1 are very rare in the pandemic. The goal of universal coverage of HIV-1 strains by diagnostic tests can be met by minimizing false negative test rates for the six globally prevalent HIV-1 group M strains and HIV-2, and by evaluating systematically coverage of rare subtypes and recombinant forms.

Update on primary HIV-1 resistance in Argentina: emergence of mutations conferring high-level resistance to nonnucleoside reverse transcriptase inhibitors in drug-naive patients

Here we present a survey including 52 drug-naive recently HIV-1-infected subjects from Buenos Aires City and province (79%) and 3 other regions in Argentina (21%). Recent infections were established from previous negative serology (32/52), indeterminate Western blot (12/52), or acute retroviral syndrome after high-risk HIV exposure (8/52) within 9 months before genotyping (median time, 4.2 months). Genotyping was performed from plasma by sequencing both protease and reverse transcriptase. Phylogenetic analysis combined with bootscanning resulted in 21 subtype B sequences and 31 B/F recombinants (RecBF). On protease, minor resistance-related mutations were found in both subtype B and RecBF with low frequencies. The substitution L89M, recently suggested as a resistance-related mutation in some subtype F viruses, was observed in 1 RecBF. On reverse transcriptase, major resistance-related mutations were found in 4 of 52 (7.7%) patients from different health centers: M41L (subtype B) and K103N+/-P225H (1 RecBF and 2 subtype B). The greater than 5% resistance threshold found indicates a need for sentinel resistance surveillances calling for an update in the current resistance testing guidelines in Argentina.

First case of HIV Type 1 subtype F among men who have sex with men in Colombia

To study the molecular epidemiology of human immunodeficiency virus (HIV) strains among men who have sex with men (MSM), the main high-risk group for HIV infection in Colombia, 113 HIV-positive MSM subjects recruited in Bogotá during the year 2002 were genotyped. By heteroduplex mobility assay (env HMA) all samples were classified as subtype B. Partial sequencing of the protease and the reverse transcriptase (Pro/RT) regions performed on a random subset of 10 samples revealed that nine were classified as subtype B, and one sample was subtype F. The specimen that is subtype F in pol and subtype B in env is likely to be is either a recombinant or a dual infection. In this study, we identify the HIV F subtype for the first time in Colombia.

Trends in drug resistance mutations in antiretroviral-naïve intravenous drug users of Rio de Janeiro

DNA sequencing of a pol gene fragment from drug-naive injecting drug users samples obtained at two time points of the Brazilian AIDS epidemic (Pre-HAART era: 1994 to early 1997, n = 27; post-HAART era: 1999-2001, n = 38) was undertaken to assess HIV-1 antiretroviral drug resistance mutations and subtyping profiles. Genotypic analysis revealed the presence of PR primary L90M, D30N, M46I, and V82A mutations in 7.9% of the post-HAART group, and a high frequency of secondary mutations (84.2%). Nucleoside RT-associated mutations were observed in 13.2%. In the pre-HAART group, a higher frequency of RT mutations was observed (22.2%) and no PR primary mutations were found, in agreement with the introduction of protease inhibitors (PIs) in therapy during the same period. The identification of 7.9% of drug-naive injecting drug users already bearing RT/PR primary resistance mutations in the post-HAART era group constitutes a major concern in terms of dissemination of drug resistant viruses. The resistance mutations profile of the individuals may reflect the context of antiretroviral treatment in Brazil at the sample collection periods (1994-1997 and 1999-2001). In spite of the differences observed in the drug resistance profiles, similar frequencies of subtype B (63.0 vs. 73.7%), F (22.2 vs. 10.5%), and recombinant B/F (14.8 vs. 15.8%) viruses were found, respectively, in the pre- and post-HAART groups.

Circulating and unique recombinant forms of HIV type 1 containing subsubtype A2

HIV-1 strains containing subsubtype A2 are relatively rare in the pandemic but have been repeatedly identified in Kenya, where candidate vaccines based in part on subtype A, but not A2 strains, may be evaluated. Among the most recent is CRF16_A2D, a circulating recombinant form (CRF) whose prototypes are complete or partial HIV-1 sequences from Kenya, Korea, and Argentina. Using samples from blood bank discards in Kenya and complete genome sequencing, this report further documents CRF16_A2D and related recombinants and identifies a second CRF, CRF21_A2D. The two A2-containing CRFs, and two recombinants related to CRF16_A2D, share common structural elements but appear to have been independently derived. Concerted selection may have influenced the emergence and spread of certain A2-containing strains in Kenya. The second complete subtype C sequence from Kenya is also reported here. Monitoring of A2-containing recombinants and subtype C strains, both relatively rare in Kenya, may be informative in the course of cohort development and evaluation of candidate vaccines.

Worldwide molecular epidemiology of HIV

Human immunodeficiency virus (HIV) is the worldwide disseminated causative agent of acquired immunodeficiency syndrome (AIDS). HIV is a member of the Lentivirus genus of Retroviridae family and is grouped in two types named HIV-1 and HIV-2. These viruses have a notable ability to mutate and adapt to the new conditions of human environment. A large incidence of errors at the transcriptional level results in changes on the genetic bases during the reproductive cycle. The elevated genomic variability of HIV has carried important implications for the diagnosis, treatment and prevention as well as epidemiologic investigations. The present review describes important definitions and geographical distribution of subtypes, circulating recombinant forms and other genomic variations of HIV. The present study aimed at leading students of Biomedical Sciences and public health laboratory staff guidance to general and specific knowledge about the genomic variability of the HIV.

Evolutionary history of HIV-1 subtype B and F infections in Brazil

OBJECTIVE

To reconstruct the onset date of the HIV-1 B and F epidemics in Brazil based on virus diversification over time.

DESIGN

We studied HIV-1 env V3 sequences (210 nt) with a known sampling year isolated from HIV-1 positive patients from Brazil between 1989 and 1997: 101 subtype B sequences and 41 subtype F sequences.

METHODS

HIV-1 V3 env sequences were grouped by year of collection and the relationship between the sampling years of HIV-1 sequences and their genetic distance to the reconstructed common ancestor (intra-population divergence) or to other sequences from the same year (intra-population diversity) was examined by using linear regression analysis.

RESULTS

Regression analysis of nucleotide distances, revealed a highly significant positive correlation between sampling years of subtype B and F V3 sequences and their intra-population divergence (P < 0.001) or diversity (P < 0.0001). In both subtype populations, the divergence and diversity increased at a rate of 0.5 and 0.9% per year, respectively. Considering these evolutionary rates, we estimate the onset of the subtype B and F HIV-1 epidemics in Brazil during early 1970s and early 1980s, respectively.

CONCLUSIONS

The consistent correlation between divergence and diversity of the V3 sequences with their sampling years indicates that the molecular clock is operational in the evolution of the HIV-1 in Brazil's epidemic, and show that subtypes B and F are evolving at a similar rate over time. The dating results suggest a discontinuous introduction of these subtypes in the Brazilian population.

Analysis of the near full length genomes of HIV-1 subtypes B, F and BF recombinant from a cohort of 14 patients in São Paulo, Brazil

The human immune deficiency virus (HIV) exhibits strikingly tremendous amount of genetic variability. Such feature is critically important for the virus to adapt to environmental changes by escaping the host immune system and by escaping candidate vaccine. Therefore, understanding of such diversity is fundamental for the design of successful drugs or vaccine, which is urgently needed to bring the HIV/AIDS epidemic under control. In this study, we investigated the magnitude of diversity of the HIV-1 near full-length genomes from patients previously assigned as infected with non-recombinant HIV-1 subtypes B and F1 variants based on small portion of viral genome. HIV-1 proviral DNA was extracted from 14 samples previously classified in our laboratory as six subtypes B and eight subtypes F on the basis of small amplicon sequencing. Reamplifications of DNA from these samples were carried out by an overlapping PCR followed by direct sequencing. The data were phylogenetically inferred. Sequence analysis revealed that two out of six partially identified subtype B and six out of eight partially identified subtype F were in fact BF recombinants throughout their full genomes. Two pairs BF recombinants had identical genomic recombination structure and distinct from the Argentinean CRF 12_BF strains, probably represents a novel circulating recombinant forms in Brazil. Our data provided new genetic material of some of the HIV-1 subtypes currently circulating in the country and points to the widespread of BF recombinants which are expected to change the epidemic nature by approaching the level of subtype B in Brazil.

Higher transactivation activity associated with LTR and Tat elements from HIV-1 BF intersubtype recombinant variants

Background

HIV-1 is characterized by its rapid genetic evolution and high diversity as a consequence of its error-prone reverse transcriptase and genetic recombination. This latter mechanism is responsible for the creation of circulating recombinant forms (CRFs) found in nature. Previous studies from our lab group have shown that the epidemic in Argentina is characterized by one highly prevalent circulating recombinant form, CRF12_BF, and many related BF recombinant forms. Since transcriptional transactivation of the HIV-1 long terminal repeat (LTR) promoter element requires the essential viral Tat protein, since these genetic structures underwent recombination in variants widely spread in South America, the aim of this work was to study transcriptional activity associated with the recombinant LTR and Tat elements.

Results

Differential transcriptional activity was measured for the BF recombinant LTR/Tat complex that is present in widely spread viral variants was demonstrated. This analysis demonstrated a higher activity for the BF complex when compared to its B subtype counterpart.

Conclusion

This study indicates structural and functional consequences of recombination events within the LTR promoter and Tat transactivator protein of a naturally occurring HIV-1 recombinant form.

The Effect of a Single Nucleotide Substitution in the Splicing Silencer in the tat/rev Intron on HIV Type 1 Envelope Expression

A complex mRNA splicing pattern, which remains to be fully characterized, influences HIV-1 gene expression. In this study, poor envelope expression of a primary HIV-1 isolate was observed and linked to increased splicing of the two coding exons of tat/rev. The substitution of a nucleotide G, located 28 nucleotides upstream of the splice acceptor site SA7 in the recently identified intron splicing silencer sequence, was found to be responsible for the poor envelope expression. A single nucleotide substitution of G with A at this position results in a poor envelope expression phenotype. Moreover, substitution of the nucleotide G with any other nucleotide in an infectious HIV-1 proviral clone, HXB2RU3, results in poor envelope expression. The substitution of this nucleotide reduces the hnRNP A1 binding affinity but increases the splicing of env mRNA. The nucleotide G at this position is highly conserved among HIV-1 isolates and appears to play a critical role in HIV-1 splicing.

Identification of two HIV type 1 circulating recombinant forms in Brazil

Recombination is an important way to generate genetic diversity. Accumulation of HIV-1 full-length genomes in databases demonstrated that recombination is pervasive in viral strains collected globally. Recombinant forms achieving epidemiological relevance are termed circulating recombinant forms (CRFs). CRF12_BF was up to now the only CRF described in South America. The objective was to identify the first CRF in Brazil conducting full genome analysis of samples sharing the same partial genome recombinant structure. Ten samples obtained from individuals residing in Santos, Brazil, sharing the same recombination pattern based on partial genome sequence data, were selected from a larger group to undergo full length genome analysis. Near full length genomes were assembled from overlapping fragments. Mosaic genomes were evaluated by Bootscan, alignment inspection, and phylogenetic analysis using neighbor joining and maximum likelihood. Full genomes were also analyzed by split decomposition. We were able to identify five mosaic genomes. Two of these structures were represented by at least three samples derived from epidemiologically unlinked individuals. These structures were named CRF28_BF and CRF29_BF and are the second and third CRFs composed exclusively by subtypes B and F as well as the second and third CRFs encountered in South America. Other recombinant forms studied here resembled CRF28_BF and CRF29_BF. Our results suggest that a diverse population of related recombinants, including CRFs may play an important part in the Brazilian and South American epidemic.

Neutralization and infectivity characteristics of envelope glycoproteins from human immunodeficiency virus type 1 infected donors whose sera exhibit broadly cross-reactive neutralizing activity

In this study, we tested the hypothesis that donors with broadly cross-reactive HIV-1 neutralizing (BCN) sera are infected with viruses encoding envelope glycoproteins (Envs) with unusual immunogenic properties. Cloned env genes were from samples of donors previously identified as having BCN antibodies (BCN donors) and from other donors not known to have such antibodies (non-BCN donors). Neutralization properties of viruses pseudotyped with BCN and non-BCN Envs were determined using BCN, non-BCN sera and broadly cross-neutralizing monoclonal antibodies (Mabs). BCN sera neutralized with higher frequency and geometric mean titers than non-BCN sera. Viruses pseudotyped with BCN Envs were mostly resistant to neutralization by anti-gp120 Mabs but tended to be more sensitive to the anti-gp41 Mabs, 2F5 and 4E10 than non-BCN Env-pseudotyped viruses. Sequence analysis of clones obtained from sequential samples of two BCN donors revealed respective 2F5 epitope mutations T662A and K665T. The K665T mutation evolved as the predominant genotype in the respective donor, consistent with an escape mutation event. The A662T mutation reduced sensitivity to 4E10, as well as 2F5 and homologous sera, consistent with neutralization escape mutation and targeting of the 2F5 epitope region by the serum. Our study suggests that viruses infecting these BCN donors encoded Envs that may have been unusually competent for induction of antibodies against the membrane proximal epitope region (MPER) of gp41, and these Envs may be useful vaccine components.

Sampling designs for HIV molecular epidemiology with application to Honduras

Proper sampling is essential to characterize the molecular epidemiology of human immunodeficiency virus (HIV). HIV sampling frames are difficult to identify, so most studies use convenience samples. We discuss statistically valid and feasible sampling techniques that overcome some of the potential for bias due to convenience sampling and ensure better representation of the study population. We employ a sampling design called stratified cluster sampling. This first divides the population into geographical and/or social strata. Within each stratum, a population of clusters is chosen from groups, locations, or facilities where HIV-positive individuals might be found. Some clusters are randomly selected within strata and individuals are randomly selected within clusters. Variation and cost help determine the number of clusters and the number of individuals within clusters that are to be sampled. We illustrate the approach through a study designed to survey the heterogeneity of subtype B strains in Honduras.

HIV type 1 CRF13_cpx revisited: identification of a new sequence from Cameroon and signal for subsubtype J2

A nearly full-length genome sequence of an HIV-1 isolate originating from Cameroon, 02CM.3226MN, was found to cluster together with previously reported CRF13 sequences 96CM-4164 and 96CM-1849. Similarity plotting, bootscanning, breakpoint analysis, and phylogenetic trees confirmed similar genomic structures with almost identical breakpoint positions among these three isolates. Thus, CRF13 now fulfills the HIV-1 nomenclature requirements. A X2 analysis across all three genomes simultaneously was applied to more accurately determine breakpoints and address the uncertainty in such estimates. Some fragments were found to be difficult to classify, as indicated by a low branching index (BI), due to limited knowledge about parental and reference subtype sequences. One fragment with low BI association to reference subtype J sequences (BI = 0.27, cut-off for subtype classification >0.55) was found to be closer to J fragments of CRF11 similar to the way that A1-A2 and F1-F2 subsubtypes associate. This suggests that subtype J may need to be reclassified into subsubtypes J1 and J2. The CRF13 genome consists of fragments from subtypes A1, G, and both J1 and J2 as well as CRF01 and one region that was left unclassified.

Sequence analysis of a South American HIV type 1 BC recombinant

We report the characterization of a near full-length sequence of a South American HIV-1 BC intersubtype recombinant, ARE195FL. This isolate contains a C(gag/pol) B(vpr/vpu/gp160(env)) C(gp41(env)/nef) mosaic structure differing from any BC full-length sequence described to date, and is the first full-length sequence obtained from a South American BC strain. Neighbor-joining analysis revealed that subtype C genomic segments of ARE195FL clustered with the South American group of subtype C strains, suggesting a local emergence of the BC recombinant. Despite having dissimilar genomic structures, ARE195FL shares a common recombination breakpoint in vif, which is a "hot spot" for recombinatory events, with the Chinese BC recombinant prototype CRF07_BC. Further full-length sequence analysis of South American HIV-1 C and BC strains is necessary to determine the relevance and spread of emerging HIV-1 BC recombinants in Latin America.

A statistical model for HIV-1 sequence classification using the subtype analyser (STAR)

MOTIVATION

HIV-1 antiretroviral drug resistance testing produces large amounts of HIV-1 protease and reverse transcriptase sequences. These provide an excellent resource to study the incidence, spread and clinical significance of HIV-1 subtypes. We have produced a program, Subtype Analyser (STAR) that rapidly and accurately subtypes HIV-1. Here we have determined a robust and statistically validated model for subtype assignment.

RESULTS

We have significantly extended our HIV-1 subtyping tool (STAR), such that each query sequence when evaluated against subtype profile alignments, returns a discriminating score based on the ratio of subtype positive to negative amino acid positions. These scores were transformed into a Z-score distribution and evaluated. Of the 141 sequences used to define the subtype alignments, 98% were correctly reclassified. Inclusion of additional recombination detection within STAR increased the detection of known recombinant sequences to 95%.

AVAILABILITY

STAR is available as compiled (Linux Fedora 3) or source code from http://pgv19.virol.ucl.ac.uk/download/star_linux.tar

CONTACT

p.kellam@ucl.ac.uk

SUPPLEMENTARY INFORMATION

http://pgv19.virol.ucl.ac.uk/download/star_supplement

Identification of a novel HIV-1 complex circulating recombinant form (CRF18_cpx) of Central African origin in Cuba

BACKGROUND

Analysis of partial pol and env sequences have indicated a high diversity of HIV-1 genetic forms in Cuba, including two potential novel circulating recombinant forms (CRF): U/H and D/A.

OBJECTIVES

To determine whether U/H recombinant viruses from Cuba, detected in 7% of samples, represent a novel HIV-1 CRF, and to identify non-Cuban viruses related to this recombinant form.

METHODS

Near full-length genome amplification was carried out by nested polymerase chain reaction in four overlapping DNA segments of two epidemiologically unlinked viruses in uncultured peripheral blood mononuclear cells. The sequences were analysed phylogenetically. Recombinant structures and phylogenetic relationships were analysed by bootscanning and by maximum likelihood. Searches for related viruses in databases were initially based on sequence homology and sharing of signature nucleotides.

RESULTS

Both Cuban viruses clustered uniformly in bootscans all along the genome with each other and with a virus from Cameroon, CM53379, indicating that all three represent the same recombinant form. Their genome comprised multiple segments clustering with subtypes A1, F, G, H and K, as well as segments failing to cluster with recognized subtypes. The newly defined CRF, designated CRF18_cpx, was phylogenetically related in partial segments to CRF13_cpx, CRF04_cpx and 36 additional viruses, most of them from Central Africa. One of the viruses from Cameroon, sequenced in the near full-length genome, was a CRF18_cpx/subtype G secondary recombinant.

CONCLUSIONS

A novel HIV-1 complex circulating recombinant form (CRF18_cpx) has been identified that is circulating in Cuba and Central Africa.

Molecular characteristics of HIV type 1 circulating in São Paulo, Brazil

Partial sequences of HIV-1 polymerase from 185 patients, 141 ARV experienced and 44 naive, of gag (p24) and env (C2V3) from a subset of naive cases were evaluated in São Paulo, Brazil. Antiretroviral resistance mutations were detected in 4% of 26 recently (<2 years) infected patients. Polymorphisms at the protease gene were common both in contemporary and pre-HAART era isolates, some significantly associated with the viral clade. HIV-1 clade B was preponderant, in 79%, with 11% clade F and one case of HIV-1 C. Recently infected women had a significantly higher proportion of non-B clade HIV-1. A mosaic pol was observed in 9%, all B/F except for one G mosaic. A CRF-12-BF structure, observed in 20% of B/F pol mosaics, provides evidence for an epidemic relationship in the major South American metropolitan areas.

Circulation of novel HIV type 1 A, B/C, and F subtypes in Argentina

The Argentine HIV-1 epidemic is considered to be represented mainly by subtype B and diverse B/F recombinants, with apparent absence of pure subtype F. In this study we describe three novel HIV-1 variants isolated from four infants born in different and distant provinces of Argentina. Partial analysis of different gene fragments spanning 18.5-40.8% of the HIV-1 complete genome revealed two subtype A HIV-1 strains in siblings, a B/C recombinant with a novel mosaic structure, and a putative subtype F. Characteristic patterns of genomic and amino acid sequences of the newly reported subtype F isolate suggest a closer genetic relationship to Argentine B/F recombinants than any other subtype F strain described so far, while the A and B/C subtypes found correspond to unusual genotypes in Argentina. Understanding the origin, diversity, and spread of HIV-1 strains worldwide will be necessary for the development of an effective vaccine approach.

HIV type 1 BF recombinant strains exhibit different pol gene mosaic patterns: descriptive analysis from 284 patients under treatment failure

Different complex structures of the pol gene have been identified in 284 HIV-1 B/F recombinant sequences obtained from a group of 587 patients under treatment failure from Argentina. To analyze the mosaic structures of these viral sequences and to determine their phylogenetic relationship, the 284 partial pol gene sequences of BF recombinant viruses were amplified by RT-PCR and sequenced. Intersubtype breakpoints were analyzed by bootscanning. Phylogenetic relationships were determined by means of neighbor-joining trees. The analysis of the sequences showed multiple phylogenetic topologies clustering within intersubtype BF reference sequences. At least three different mosaic patterns were found compared to previously described BF-type viruses with unequal distribution in the studied population. The analysis also showed that HIV-1 BF recombinant viruses with diverse mosaic structures are phylogenetically related in their F segments and in selected B fragments with the F1 subtype and with BF recombinant viruses from Brazil, respectively, suggesting a common recombinant ancestor. No association was observed between the prevalence of each mosaic pattern and the frequency of major drug-resistance mutations in PR and RT.

Analysis of near full-length genome sequences of HIV type 1 BF intersubtype recombinant viruses from Brazil reveals their independent origins and their lack of relationship to CRF12_BF

We analyze the recombinant structures and phylogenetic relationships of nine near full-length genome sequences of HIV-1 BF intersubtype recombinant viruses from Brazil, eight of them newly derived. These were obtained by PCR amplification from peripheral blood mononuclear cells (PBMCs) DNA or PBMCs culture supernantant RNA. The recombinants exhibited unique mosaic structures, except two viruses with a single near coincident breakpoint. Comparison with CRF12_BF revealed only two coincident breakpoints in two recombinants. Phylogenetic analyses failed to support a common ancestry of Brazilian recombinants or their relationship to CRF12_BF, which widely circulates in Argentina. Intersubtype breakpoint distribution along the genome was uneven, with the highest mean frequency in the polymerase domain of reverse transcriptase, and the lowest in env. These results indicate that HIV-1 BF recombinants from Brazil have independent origins and are unrelated to CRF12_BF, and that intersubtype breakpoints are frequent in pol segments analyzed for drug resistance detection.

The evolution of HIV and its consequences

Since the beginning of the AIDS epidemic in 1981, HIV-1 has demonstrated an amazing ability to mutate. HIV-1 was introduced into the human population in the early to mid twentieth century in central Africa. During ensuing decades, this extraordinary mutational capacity has resulted in the circulation of HIV-1 strains that are quite different from one another, yet still remarkably pathogenic. The potential impact of this viral diversity on treatment, monitoring,and vaccine development is discussed.

Epidemiological and molecular evidence of two events of father-to-child HIV type 1 horizontal transmission

HIV-1 infection in children less than 15 years of age is mainly due to mother-to-child transmission. The aim of this work was to investigate molecular evidence to prove father-to-be horizontal transmission in two possible events of transmission. In the first event a boy was identified as HIV infected at 2-3 years of age. At the same time infection was confirmed in the father, while mother and siblings were negative. In the second event a girl was negative for HIV at age 1 and identified as HIV-1 infected at age 6. The father's HIV infection was diagnosed in the same period while the mother was repeatedly negative. No evidence of sexual assault or transfusion was recorded in any case. Peripheral blood mononuclear cells were obtained from both fathers and children. After PCR amplification, the C2V3 region of the envelope gene and the region coding for amino acid 132 of p24 up to amino acid 40 of p7 of the gag gene were sequenced. Genetic distance measurements and phylogenetic tree analysis showed that in both cases the father's and child's viral sequences were closely related. They were distinct when compared to Argentina sequences including sequences from the same geographic region. Epidemiological and molecular data strongly suggest that horizontal transmission had occurred, probably related to the close father-to-child contact.

Drug resistance testing provides evidence of the globalization of HIV type 1: a new circulating recombinant form

To monitor HIV-1 diversity in Argentina, a phylogenetic-based analysis of HIV-1 partial pol sequences obtained for resistance testing in 587 treatment failure patients was performed in Buenos Aires city between 2001 and 2003. HIV-1 RNA was isolated from plasma samples and partial pol fragments amplified by RT-PCR. Sequences were obtained by automated sequencing. Phylogenetic analysis was performed and recombination patterns characterized. A total of 299 sequences grouped into clade B (50.94%) and 284 were B/F recombinants (48.38%). Four sequences were grouped into clades A, C, and F (0.68%). The clade C sample, 96105, was found to be a BC recombinant and samples 103396 and 104575 showed the same mosaic pattern with Kisii5009 from Kenya and 97KR004 from Korea, previously described as A2D recombinants. With the presence of two full-length genomes, one from Kenya and one from Korea, and now two partial genomes from Argentina, this recombinant is designated CRF16_A2D. Its presence on three continents shows that CRF16_A2D has a global distribution.

Intersubtype BF Recombinants of HIV-1 in a Population of Injecting Drug Users in Argentina

The presence of recombinant intersubtypes of HIV-1 in Argentina has been reported since the mid-1990s. In this study, sequences of a region of the gag, pol, and vpu genes of HIV-1 were analyzed in samples of 21 injection drug users (IDUs) residing in the suburbs of the city of Buenos Aires. Genomic characterization and identification of recombination sites were made comparing the 3 regions with reference isolation sequences of subtypes B, F, C, A, and B/F recombinants: CRF12_BF and non-CRF12_BF sequences. Subtype assignment of the analyzed segments was phylogenetically confirmed. All the samples turned out to be BF recombinants in at least 1 of the 3 studied genes. Twelve samples (57%) had the same pattern as the Argentinean CRF12_BF, whereas in the rest, the pattern differed in at least 1 of the 3 genes. The relation of these fragments to the CRF12_BF was phylogenetically verified. These results indicate the predominance of BF recombinants and the presence of a high percentage of sequences closely related to the CRF12_BF in the IDU population in Argentina and suggest a possible association between viral variants and the transmission route.

Human immunodeficiency virus type 1 superinfection was not detected following 215 years of injection drug user exposure

Evidence for human immunodeficiency virus type 1 (HIV-1) superinfection was sought among 37 HIV-1-positive street-recruited active injection drug users (IDUs) from the San Francisco Bay area. HIV-1 sequences from pairs of samples collected 1 to 12 years apart, spanning a total of 215 years of exposure, were generated at p17 gag, the V3-V5 region of env, and/or the first exon of tat and phylogenetically analyzed. No evidence of HIV-1 superinfection was detected in which a highly divergent HIV-1 variant emerged at a frequency >20% of the serum viral quasispecies. Based on the reported risk behavior of the IDUs and the HIV-1 incidence in uninfected subjects in the same cohort, a total of 3.4 new infections would have been expected if existing infection conferred no protection from superinfection. Adjusted for risk behaviors, the estimated relative risk of superinfection compared with initial infection was therefore 0.0 (95% confidence interval, 0.00, 0.79; P = 0.02), indicating that existing infection conferred a statistically significant level of protection against superinfection with an HIV-1 strain of the same subtype, which was between 21 and 100%.

Near full-length genome characterization of an HIV type 1 CRF05_DF virus from Spain

We report the near full-length sequence characterization of a HIV-1 DF intersubtype recombinant virus from Spain, X492, directly amplified from peripheral blood mononuclear cells' DNA. This isolate shares an identical mosaic structure and exhibits consistent phylogenetic clustering along the genome with VI961, a previously characterized DF recombinant virus. By contrast, VI1310, which may represent the same recombinant form as VI961 (CRF05_DF), is only partially homologous to VI961 and X492. Of three additional DF recombinant viruses previously characterized in gag-pol, only one, VI1267, clusters uniformly with VI961 and X492; the other two branch separately in a segment of pol. These results allow us to define an HIV-1 circulating recombinant form (CRF05_DF), characterized in near full-length genomes of two isolates (VI961 and X492) and in partial gag-pol sequences of a third virus (VI1267). Three other reported DF recombinant viruses, including the fully sequenced VI1310, exhibit incomplete homology to VI961 and X492.