High HIV-1 genetic diversity in Cuba

Cuban history of CRF19 recombinant subtype of HIV-1

CRF19 is a recombinant form of HIV-1 subtypes D, A1 and G, which was first sampled in Cuba in 1999, but was already present there in 1980s. CRF19 was reported almost uniquely in Cuba, where it accounts for ∼25% of new HIV-positive patients and causes rapid progression to AIDS (∼3 years). We analyzed a large data set comprising ∼350 pol and env sequences sampled in Cuba over the last 15 years and ∼350 from Los Alamos database. This data set contained both CRF19 (∼315), and A1, D and G sequences. We performed and combined analyses for the three A1, G and D regions, using fast maximum likelihood approaches, including: (1) phylogeny reconstruction, (2) spatio-temporal analysis of the virus spread, and ancestral character reconstruction for (3) transmission mode and (4) drug resistance mutations (DRMs). We verified these results with a Bayesian approach. This allowed us to acquire new insights on the CRF19 origin and transmission patterns. We showed that CRF19 recombined between 1966 and 1977, most likely in Cuban community stationed in Congo region. We further investigated CRF19 spread on the Cuban province level, and discovered that the epidemic started in 1970s, most probably in Villa Clara, that it was at first carried by heterosexual transmissions, and then quickly spread in the 1980s within the "men having sex with men" (MSM) community, with multiple transmissions back to heterosexuals. The analysis of the transmission patterns of common DRMs found very few resistance transmission clusters. Our results show a very early introduction of CRF19 in Cuba, which could explain its local epidemiological success. Ignited by a major founder event, the epidemic then followed a similar pattern as other subtypes and CRFs in Cuba. The reason for the short time to AIDS remains to be understood and requires specific surveillance, in Cuba and elsewhere.

Molecular Epidemiology of HIV-1 Virus in Puerto Rico: Novel Cases of HIV-1 Subtype C, D, and CRF-24BG

HIV-1 subtype B virus is the most prevalent subtype in Puerto Rico (PR), accounting for about 90% of infection in the island. Recently, other subtypes and circulating recombinant forms (CRFs), including F(12_BF), A (01_BF), and CRF-39 BF-like, have been identified. The purpose of this study is to assess the distribution of drug resistance mutations and subtypes in PR. A total of 846 nucleotide sequences from the period comprising 2013 through 2017 were obtained from our "HIV Genotyping" test file. Phylogenetic and molecular epidemiology analyses were performed to evaluate the evolutionary dynamics and prevalence of drug resistance mutations. According to our results, we detected a decrease in the prevalence of protease inhibitor, nucleoside reverse transcriptase inhibitor (NRTI), and non-NRTI (NNRTI) resistance mutations over time. In addition, we also detected recombinant forms and, for the first time, identified subtypes C, D, and CRF-24BG in PR. Recent studies suggest that non-subtypes B are associated with a high risk of treatment failure and disease progression. The constant monitoring of viral evolution and drug resistance mutation dynamics is important to establish appropriate efforts for controlling viral expansion.

HIV-1 subtype B: Traces of a pandemic

Human migration is a major process that shaped the origin and dissemination of HIV. Within HIV-1, subtype B (HIV-1B) is the most disseminated variant and it is assumed to be the causative agent in approximately 11% of all cases of HIV worldwide. Phylogenetic studies have revealed that HIV-1B emerged in Kinshasa (Africa) and was introduced into the Caribbean region via Haiti in or around 1966 by human migration. After localized dispersion, the virus was brought to the United States of America via homosexual/bisexual contact around 1969. Inside USA, the incidence of HIV-1B infection increased exponentially and it became established in the population, affecting not only homosexual individuals but also heterosexual individuals and injecting drug users. Soon after, the virus was disseminated and became established in other regions, including Europe, Asia, Latin America, and Australia. Recent studies suggest that, in addition to this pandemic clade, several lineages have emerged from Haiti and reached other Caribbean and Latin American countries via short-distance dissemination. Different subtype B genetic variants have also been detected in these epidemics. Four genetic variants have been described to date: subtype B', which mainly circulates in Thailand and other Asian countries; a specific variant mainly found in Trinidad and Tobago; the GPGS variant, which is primarily detected in Korea; and the GWGR variant, which is mainly detected in Brazil. This paper reviews the evolution of HIV-1B and its impact on the human population.

Spatiotemporal dynamics of dissemination of non-pandemic HIV-1 subtype B clades in the Caribbean region

The Human immunodeficiency virus type-1 (HIV-1) epidemic in the Caribbean region is mostly driven by subtype B; but information about the pattern of viral spread in this geographic region is scarce and different studies point to quite divergent models of viral dissemination. In this study, we reconstructed the spatiotemporal and population dynamics of the HIV-1 subtype B epidemic in the Caribbean. A total of 1,806 HIV-1 subtype B pol sequences collected from 17 different Caribbean islands between 1996 and 2011 were analyzed together with sequences from the United States (n = 525) and France (n = 340) included as control. Maximum Likelihood phylogenetic analyses revealed that HIV-1 subtype B infections in the Caribbean are driven by dissemination of the pandemic clade (BPANDEMIC) responsible for most subtype B infections across the world, and older non-pandemic lineages (BCAR) characteristics of the Caribbean region. The non-pandemic BCAR strains account for >40% of HIV-1 infections in most Caribbean islands; with exception of Cuba and Puerto Rico. Bayesian phylogeographic analyses indicate that BCAR strains probably arose in the island of Hispaniola (Haiti/Dominican Republic) around the middle 1960s and were later disseminated to Trinidad and Tobago and to Jamaica between the late 1960s and the early 1970s. In the following years, the BCAR strains were also disseminated from Hispaniola and Trinidad and Tobago to other Lesser Antilles islands at multiple times. The BCAR clades circulating in Hispaniola, Jamaica and Trinidad and Tobago appear to have experienced an initial phase of exponential growth, with mean estimated growth rates of 0.35-0.45 year(-1), followed by a more recent stabilization since the middle 1990s. These results demonstrate that non-pandemic subtype B lineages have been widely disseminated through the Caribbean since the late 1960s and account for an important fraction of current HIV-1 infections in the region.

Spatiotemporal dynamics of the HIV-1 subtype G epidemic in West and Central Africa

The human immunodeficiency virus type 1 (HIV-1) subtype G is the second most prevalent HIV-1 clade in West Africa, accounting for nearly 30% of infections in the region. There is no information about the spatiotemporal dynamics of dissemination of this HIV-1 clade in Africa. To this end, we analyzed a total of 305 HIV-1 subtype G pol sequences isolated from 11 different countries from West and Central Africa over a period of 20 years (1992 to 2011). Evolutionary, phylogeographic and demographic parameters were jointly estimated from sequence data using a Bayesian coalescent-based method. Our analyses indicate that subtype G most probably emerged in Central Africa in 1968 (1956–1976). From Central Africa, the virus was disseminated to West and West Central Africa at multiple times from the middle 1970s onwards. Two subtype G strains probably introduced into Nigeria and Togo between the middle and the late 1970s were disseminated locally and to neighboring countries, leading to the origin of two major western African clades (G_WA-I and G_WA-II). Subtype G clades circulating in western and central African regions displayed an initial phase of exponential growth followed by a decline in growth rate since the early/middle 1990s; but the mean epidemic growth rate of G_WA-I (0.75 year⁻¹) and G_WA-II (0.95 year⁻¹) clades was about two times higher than that estimated for central African lineages (0.47 year⁻¹). Notably, the overall evolutionary and demographic history of G_WA-I and G_WA-II clades was very similar to that estimated for the CRF06_cpx clade circulating in the same region. These results support the notion that the spatiotemporal dissemination dynamics of major HIV-1 clades circulating in western Africa have probably been shaped by the same ecological factors.

Profile of the HIV epidemic in Cape Verde: molecular epidemiology and drug resistance mutations among HIV-1 and HIV-2 infected patients from distinct islands of the archipelago

HIV-1 and HIV-2 have been detected in Cape Verde since 1987, but little is known regarding the genetic diversity of these viruses in this archipelago, located near the West African coast. In this study, we characterized the molecular epidemiology of HIV-1 and HIV-2 and described the occurrence of drug resistance mutations (DRM) among antiretroviral therapy naïve (ARTn) patients and patients under treatment (ARTexp) from different Cape Verde islands. Blood samples, socio-demographic and clinical-laboratory data were obtained from 221 HIV-positive individuals during 2010–2011. Phylogenetic and bootscan analyses of the pol region (1300 bp) were performed for viral subtyping. HIV-1 and HIV-2 DRM were evaluated for ARTn and ARTexp patients using the Stanford HIV Database and HIV-GRADE e.V. Algorithm Homepage, respectively. Among the 221 patients (169 [76.5%] HIV-1, 43 [19.5%] HIV-2 and 9 [4.1%] HIV-1/HIV-2 co-infections), 67% were female. The median ages were 34 (IQR = 1–75) and 47 (IQR = 12–84) for HIV-1 and HIV-2, respectively. HIV-1 infections were due to subtypes G (36.6%), CRF02_AG (30.6%), F1 (9.7%), URFs (10.4%), B (5.2%), CRF05_DF (3.0%), C (2.2%), CRF06_cpx (0.7%), CRF25_cpx (0.7%) and CRF49_cpx (0.7%), whereas all HIV-2 infections belonged to group A. Transmitted DRM (TDRM) was observed in 3.4% (2/58) of ARTn HIV-1-infected patients (1.7% NRTI, 1.7% NNRTI), but not among those with HIV-2. Among ARTexp patients, DRM was observed in 47.8% (33/69) of HIV-1 (37.7% NRTI, 37.7% NNRTI, 7.4% PI, 33.3% for two classes) and 17.6% (3/17) of HIV-2-infections (17.6% NRTI, 11.8% PI, 11.8% both). This study indicates that Cape Verde has a complex and unique HIV-1 molecular epidemiological scenario dominated by HIV-1 subtypes G, CRF02_AG and F1 and HIV-2 subtype A. The occurrence of TDRM and the relatively high level of DRM among treated patients are of concern. Continuous monitoring of patients on ART, including genotyping, are public policies to be implemented.

Phylodynamics of the HIV-1 epidemic in Cuba

Previous studies have shown that the HIV-1 epidemic in Cuba displayed a complex molecular epidemiologic profile with circulation of several subtypes and circulating recombinant forms (CRF); but the evolutionary and population history of those viral variants remains unknown. HIV-1 pol sequences of the most prevalent Cuban lineages (subtypes B, C and G, CRF18_cpx, CRF19_cpx, and CRFs20/23/24_BG) isolated between 1999 and 2011 were analyzed. Maximum-likelihood analyses revealed multiple introductions of subtype B (n≥66), subtype C (n≥10), subtype G (n≥8) and CRF18_cpx (n≥2) viruses in Cuba. The bulk of HIV-1 infections in this country, however, was caused by dissemination of a few founder strains probably introduced from North America/Europe (clades B_CU-I and B_CU-II), east Africa (clade C_CU-I) and central Africa (clades G_CU, CRF18_CU and CRF19_CU), or locally generated (clades CRFs20/23/24_BG). Bayesian-coalescent analyses show that the major HIV-1 founder strains were introduced into Cuba during 1985–1995; whereas the CRFs_BG strains emerged in the second half of the 1990s. Most HIV-1 Cuban clades appear to have experienced an initial period of fast exponential spread during the 1990s and early 2000s, followed by a more recent decline in growth rate. The median initial growth rate of HIV-1 Cuban clades ranged from 0.4 year⁻¹ to 1.6 year⁻¹. Thus, the HIV-1 epidemic in Cuba has been a result of the successful introduction of a few viral strains that began to circulate at a rather late time of the AIDS pandemic, but then were rapidly disseminated through local transmission networks.

Characterizing viral subtypes to assess patterns of HIV transmission

We characterized HIV-1 subtypes among 204 persons newly diagnosed with HIV in Ontario from 2003 to 2005 using samples from the Canadian HIV Strain and Drug Resistance Surveillance Program. We examined HIV-1 subtype by demographic characteristics and exposure category, and determined independent predictors of infection with a non-B HIV subtype using multivariate logistic regression. The distribution of HIV subtypes was: B 77.0%, C 10.3%, AG 4.9%, A 2.5%, AE 2.5% and others 3.0%. Overall, 23.0% were non-B, greater in women than in men (62.8% versus 12.4%, P < 0.0001) and persons under 35 years (31.1% versus 18.5% in those ≥35, P = 0.04). Non-B subtype was predominant (78.9%) among persons from HIV-endemic regions and considerable (28.6%) among other persons infected heterosexually. In multivariate modelling adjusted for gender, non-B subtype was significantly associated with birth in an HIV-endemic region (adjusted odds ratio [aOR] 59.2, P < 0.0001) and heterosexual exposure (aOR 6.3, P = 0.02). Additionally, compared with men who had sex with men, non-B subtype was greater among heterosexual women (aOR 17.8, P < 0.001) and women who injected drugs (injection drug use, aOR 13.4, P = 0.01). We found a non-negligible proportion of non-B subtypes among women infected heterosexually not from HIV-endemic countries, providing interesting insights into HIV transmission patterns.

HIV type 1 genetic diversity in newly diagnosed Cuban patients

Knowledge of the genetic diversity of HIV-1 constitutes a fundamental premise in the epidemiological surveillance. In the present study, the HIV-1 genetic variability from 142 Cuban patients who were diagnosed with HIV-1 infection during 2009 and 2010 was determined. HIV-1 subtypes were determined by partial RT-PCR and sequencing of the HIV-1 pol gene. The phylogenetic analysis showed that 47 (33.1 %) samples were subtypes B and 95 (66.9 %) were non-B subtypes, where G, H, and C subtypes, as well as the recombinant forms CRF19_cpx, CRF18_cpx, and CRFs BG, were included. The circulation of CRF05_DF was detected for the first time in Cuba. The analyses of recombinants showed the presence of recombinant CRF18_cpx/CRF19_cpx. The study confirms the high genetic diversity of HIV-1 and the circulation of new genetic variants in the studied population, which indicates the importance of maintaining constant epidemiological surveillance in Cuba.

Reviewing the history of HIV-1: spread of subtype B in the Americas

The dispersal of HIV-1 subtype B (HIV-1B) is a reflection of the movement of human populations in response to social, political, and geographical issues. The initial dissemination of HIV-1B outside Africa seems to have included the passive involvement of human populations from the Caribbean in spreading the virus to the United States. However, the exact pathways taken during the establishment of the pandemic in the Americas remain unclear. Here, we propose a geographical scenario for the dissemination of HIV-1B in the Americas, based on phylogenetic and genetic statistical analyses of 313 available sequences of the pol gene from 27 countries. Maximum likelihood and Bayesian inference methods were used to explore the phylogenetic relationships between HIV-1B sequences, and molecular variance estimates were analyzed to infer the genetic structure of the viral population. We found that the initial dissemination and subsequent spread of subtype B in the Americas occurred via a single introduction event in the Caribbean around 1964 (1950–1967). Phylogenetic trees present evidence of several primary outbreaks in countries in South America, directly seeded by the Caribbean epidemic. Cuba is an exception insofar as its epidemic seems to have been introduced from South America. One clade comprising isolates from different countries emerged in the most-derived branches, reflecting the intense circulation of the virus throughout the American continents. Statistical analysis supports the genetic compartmentalization of the virus among the Americas, with a close relationship between the South American and Caribbean epidemics. These findings reflect the complex establishment of the HIV-1B pandemic and contribute to our understanding between the migration process of human populations and virus diffusion.

Current molecular epidemiology and recombination of HIV type 1 subtypes in northern Thailand

HIV subtype characterization is an important tool to monitor the genetic variation of the HIV epidemic. This study investigated the current HIV subtype distribution and recombination among the northern Thai population. An in-house genotypic assay of HIV protease and reverse transcriptase genes was performed on 420 plasma specimens from HIV-infected patients residing in several northern Thai provinces. HIV subtyping was determined by phylogenetic analysis. Three hundred and ninety-eight sequences (94.8%) were identified as CRF01_AE with the genetic distance of 1.848 ± 0.957% and 12 (2.9%) as subtype B with the genetic distance of 4.186 ± 0.849%. In addition, two sequences (0.5%) of HIV subtype C were found, suggesting that these patients were either immigrants from another country or were infected through heterosexual contact with HIV-infected subjects from another country. Bootscan analysis showed that there were eight (1.9%) unique recombinant forms (URFs) consisting of a recombinant of CRF01_AE with subtype B or subtype C. The information from this study is useful for prevention programs to halt the onward transmission of a particular HIV outbreak. However, characterization of the full genome of these CRF01_AE/B and CRF01_AE/C intersubtype recombinants, and also subtype C, is required for confirmation and elucidation.

Mechanisms and factors that influence high frequency retroviral recombination

With constantly changing environmental selection pressures, retroviruses rely upon recombination to reassort polymorphisms in their genomes and increase genetic diversity, which improves the chances for the survival of their population. Recombination occurs during DNA synthesis, whereby reverse transcriptase undergoes template switching events between the two copackaged RNAs, resulting in a viral recombinant with portions of the genetic information from each parental RNA. This review summarizes our current understanding of the factors and mechanisms influencing retroviral recombination, fidelity of the recombination process, and evaluates the subsequent viral diversity and fitness of the progeny recombinant. Specifically, the high mutation rates and high recombination frequencies of HIV-1 will be analyzed for their roles in influencing HIV-1 global diversity, as well as HIV-1 diagnosis, drug treatment, and vaccine development.

Near full-length sequence of HIV type 1 subtype J strain 04CMU11421 from Cameroon

Although Cameroon, in west central Africa, has a relatively low HIV prevalence of 5-6%, all HIV-1 groups (M, N, O, and P), nearly all HIV-1 group M subtypes, and numerous intersubtype recombinant forms have been identified in Cameroon. In this report, we describe the near full-length sequence of 04CMU11421, an HIV-1 group M subtype J strain collected in Cameroon in 2004. Phylogenetic analysis of the genome sequence shows high bootstrap support with three subtype J reference sequences in the HIV Sequence database. Therefore, 04CMU11421 represents a fourth pure subtype J isolate and the first reported in Cameroon.

Identification of 3 phylogenetically related HIV-1 BG intersubtype circulating recombinant forms in Cuba

BG intersubtype recombinants represented 11.6% of HIV-1 isolates in a recent survey in Cuba based on pol sequences, most of them forming a single clade further subdivided into 3 subclades. Here, we analyze 8 near full-length genomes and 1 gag-pol sequence from epidemiologically unlinked Cuban BG recombinants from these 3 subclades (3 from each). Near full-length sequences were also obtained from 3 subtype G and 2 subtype B Cuban viruses. Phylogenetic relationships were estimated via maximum likelihood, and mosaic structures of the recombinants were inferred with the bootscanning, MaxChi, Genconv, and GARD methods. For the near full-length genomes, all recombinants formed a strongly supported clade further subdivided into the same subclades previously defined in pol. Mosaic structures were identical within each subclade and different among subclades, although 5 breakpoints were coincident among all recombinants. Individual phylogenetic trees for nonrecombinant fragments (concatenated B and G subtype segments) indicated a common ancestry for the parental viruses and their relationships to local subtype B and G strains. These results allow us to identify 3 new BG intersubtype circulating recombinant forms in Cuba derived from a common recombinant ancestor, which originated from B and G subtype parental strains circulating in Cuba.

Genotypic resistance to antiretroviral drugs in patients infected with several HIV type 1 genetic forms in Cuba

The main objective of this study is to evaluate the prevalence of resistance-associated mutations to reverse transcriptase (RT) and protease (PR) inhibitors (I) 2 years after the introduction of antiretroviral treatment in Cuba, analyzing the mutations corresponding to different HIV-1 genetic forms circulating in Cuba. A total of 425 plasma samples were collected in 2003, corresponding to 175 (41.2%) subtype B and 250 (58.8%) non-B genetic forms, including 56 (22.4 %) non-B subtypes, 112 (44.8%) circulating recombinant forms (CRFs), and 82 (32.8%) unique RFs (URFs). Of these, 175 (41.2%) patients were under highly active antiretroviral therapy (HAART) and 250 (58.8%) were treatment-naive. The presence of RT and PR resistance-associated mutations was established by sequencing. Levels of resistance were evaluated according to the Stanford Database program (http://hivdb.stanford.edu). The prevalence of resistance to RTI was 52.2% among RTI-treated patients, 51.5% for subtype B, and 53.2% for non-B genetic forms, including CRF18_cpx, CRF19_cpx, subtype C, and BG URF. In treatment-naive patients it was 6.4% in subtype B and 4.2% in non-B subtypes and RFs. The prevalence of resistance to PRI was 30% among PRI-treated patients, 28% in subtype B and 31% in non-B genetic forms, and 3.2% among treatment-naive subjects, mostly BG recombinants. In conclusion, significant differences in the prevalence of resistance to RTI and PRI were not detected among the most frequent genetic forms from treated patients, suggesting that the genetic diversity of HIV-1 in Cuba does not play a main role in the development of resistance to antiretroviral drugs. The presence of transmitted resistance mutations supports the study of resistance at baseline of treatment.

Limitations to contact tracing and phylogenetic analysis in establishing HIV type 1 transmission networks in Cuba

Sequence analysis can be used to evaluate transmission networks. We have used retrospective samples to examine two HIV-1 transmission networks established by contact tracing. Regions of the HIV-1 region representing segments of gag and env were amplified by RT-PCR from frozen plasma samples and the sequence of each PCR product was determined. Within one of the networks (composed of 38 subjects) we found only a subset of the tested sequence clusters was consistent with the reported epidemiological linkage. Of 15 presumed transmission events where sequence data were available, 9 could be rejected either by subtype mismatch or by phylogenetic tests. In the other network (composed of 89 subjects) we were able to assess sequences for 26 presumed transmission events, 18 of which were rejected based on subtype discordance. Long lags in time between the time of transmission and the time of sequence sampling (ranging from 2 to 18 years) may limit the sensitivity for the detection of sequence linkage. Also, superinfection and incomplete epidemiological information are other factors that will limit the concordance of phylogenetic reconstruction and reported epidemiological linkage.

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.

Origins of HIV and the evolution of resistance to AIDS

The cross-species transmission of lentiviruses from African primates to humans has selected viral adaptations which have subsequently facilitated human-to-human transmission. HIV adapts not only by positive selection through mutation but also by recombination of segments of its genome in individuals who become multiply infected. Naturally infected nonhuman primates are relatively resistant to AIDS-like disease despite high plasma viral loads and sustained viral evolution. Further understanding of host resistance factors and the mechanisms of disease in natural primate hosts may provide insight into unexplored therapeutic avenues for the prevention of AIDS.

HIV Type 1 molecular epidemiology in cuba: high genetic diversity, frequent mosaicism, and recent expansion of BG intersubtype recombinant forms

Highly diverse HIV-1 genetic forms are circulating in Cuba, including subtypes B and G and two recombinant forms of African origin (CRF18_cpx and CRF19_cpx). Here we phylogenetically analyze pol sequences from a large collection of recent samples from Cuba, corresponding to 425 individuals from all Cuban provinces, which represents approximately 12% of prevalent infections in the country. RNA from plasma was used to amplify a pol segment by reverse transcription-polymerase chain reaction; phylogenetic analyses were performed with neighbour-joining trees and bootscanning. The distribution of genetic forms was subtype B, 41.2%; CRF19_cpx, 18.4%; BG recombinants, 11.6%; CRF18_cpx, 7.1%; subtype C, 6.1%; subtype G, 3.8%; B/CRF18 recombinants, 2.6%; subtype H, 2.1%; B/CRF19 recombinants, 1.7%; and others, 5.4%. Seventy-five (17.6%) viruses were recombinant between genetic forms circulating in Cuba. In logistic regression analyses, adjusting by gender and region, subtype B was more prevalent (OR 5.0, 95% CI 2.0-12.3) and subtype G less prevalent (OR 0.1, 95% CI 0.0-0.5) among men who have sex with men (MSM) than among heterosexuals. Within the main genetic forms of Cuba there were phylogenetic subclusters, several of which correlated with risk exposure or region. BG recombinants formed three phylogenetically related subclusters, corresponding to three different mosaic structures; most of these recombinants were from MSM from Havana City, among whom they have expanded recently, reaching 31% HIV-1 infections diagnosed in 2003. This study confirms the high HIV-1 diversity and frequent recombination in Cuba and reveals the recent expansion of diverse related BG recombinant forms in this country.

Coinoculation with hepatitis B surface and core antigen promotes a Th1 immune response to a multiepitopic protein of HIV-1

It has been defined that strong and multispecific cellular immune responses correlate with a better prognosis during the course of chronic diseases. A cross-enhancing effect on the resulting immune response obtained by the coadministration of recombinant hepatitis B virus (HBV) surface and core Ag was recently observed. With the objective of studying the effect of such Ag on the immune response to coinoculated heterologous Ag and vice versa, several formulations containing the recombinant HBV Ag and a multiepitopic protein (CR3) composed by CTL and Th epitopes from HIV-1 were evaluated by s.c. and mucosal administration. Combinations of two and three Ag were evaluated for cellular and humoral immune responses. The results showed that the best Ag combination for nasal immunization was the mixture comprising the CR3 recombinant HIV protein and both HBV Ag. Similarly, it was also the best formulation for s.c. immunization in aluminium phosphate adjuvant. In conclusion, it is possible to induce a Th1 stimulation of the cellular immune response specific for a HIV-based recombinant protein by formulating this Ag with the recombinant HBV Ag.

Identification of a Novel HIV-1 Circulating ADG Intersubtype Recombinant Form (CRF19_cpx) in Cuba

Circulating recombinant forms (CRFs) represent a substantial proportion of HIV-1 isolates in the global pandemic. Characterization of HIV-1 genetic forms, including CRFs, may be relevant to studies on molecular epidemiology, recombination, superinfection, vaccine development, and antiretroviral therapy. This study analyzes near complete genomes of 4 epidemiologically unlinked viruses from Cuba, originally characterized as D/A intersubtype recombinants in pol and env segments. The genomes of 3 viruses exhibited virtually coincident mosaic structures, with multiple segments of subtypes A, D, and G and uniform phylogenetic clustering with each other along the genome. These results allow us to define a new CRF (CRF19_cpx). The 4th analyzed Cuban virus was recombinant between CRF19_cpx and CRF18_cpx (which also circulates in Cuba). CRF19_cpx exhibited homology to an AG intersubtype recombinant virus from Cameroon (CM53392) along approximately 5 kb and clustered with a subtype D virus from Gabon (G109) in gag. Four other viruses from central or west Africa were also phylogenetically related to CRF19_cpx in env fragments. These results allow us to define CRF19_cpx as a second novel CRF of African origin circulating in Cuba, to identify putative representative viruses of its parental strains, and to characterize a unique CRF18/CRF19 recombinant virus.

HIV diversity, molecular epidemiology, and the role of recombination

The magnitude of the HIV pandemic and its extensive genetic variation may earn it a unique place among infectious agents. A high mutation rate and a rampant recombination are driving HIV's evolution. Nine subtypes and a variety of recombinant forms of HIV now exist. The source of recombinant forms is the multiple infection of target cells, which becomes highly significant when individuals become infected with two or more divergent strains. In the current paper, we re-examine the role of dual infection and recombination in the generation of HIV-1 diversity, both in individuals and on a global scale. The current molecular epidemiology of HIV-1 is reviewed, emphasizing the latest reports from regional epidemics.

HIV-1 genetic diversity in antenatal cohort, Canada

We studied HIV genetic diversity in a cohort of 127 pregnant, HIV-infected women who received prenatal care at Sainte-Justine Hospital in Montreal, Canada, between 1999 and 2003. Clade assignments were derived by phylogenetic analysis of amplified pol sequences. Genotyping was successful in 103 of 127 women, 59 (57.3%) of whom were infected with clade B HIV-1, and 44 (42.7%) with nonclade B viruses, including subtypes A, C, D, F, G, and H. Four sequences remained unassigned. Forty-three of 44 women infected with non-clade B viruses were newcomers from sub-Saharan Africa, and subtype identity was consistent with those circulating in their countries of origin. These results highlight the epidemiologic importance of non-B HIV-1 in antenatal populations in a large North American urban center, underscore the influence of population movements on clade intermixing, and identify a group of patients who could be targeted for surveillance and drug therapy followup.

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.

HIV-1 co/super-infection in intravenous drug users

BACKGROUND

The frequency of HIV-1 co/super-infection is unknown despite their implications for public health and vaccine development. This issue was addressed during an epidemic of both CRF11 and B subtype among intravenous drug users (IVDUs).

METHODS

Bulk sequencing of reverse transcriptase, protease and C2V3 regions and subtype-specific nested polymerase chain reaction (PCR) in plasma and proviral DNA were performed using baseline and follow-up samples collected in recently infected IVDUs between 1998-2002 and in IVDUs with chronic infection living in the same area and presenting an unexpected rise of viremia (> 1 log10).

RESULTS

In 58 recently infected patients, three B/CRF-11 co-infections, 25 B, 28 CRF-11 and two other subtypes were detected at baseline. In the three co-infected patients, both CRF-11 and B were detected in plasma and proviral DNA and persisted during follow-up. B- and CFR-11-specific PCR performed on follow-up samples of 40 of 58 recently infected patients (median follow-up, 14.5 months) revealed a transient B super-infection in a patient initially infected by CRF-11. Five of 156 chronic IVDUs (total follow-up: 346 years) had an unexpected rise of viremia. In two of them, aviremic without treatment for years after an initial B infection, a symptomatic CRF-11 super-infection occurred and was associated with high viral load and a fall of CD4 cell count.

CONCLUSIONS

In recently infected IVDUs, co-infection B/CRF-11 is relatively frequent (5%). In chronically infected IVDUs super-infection may be transient and may occur in patients controlling efficiently HIV infection by the initial strain.

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.

Travel and the spread of HIV-1 genetic variants

HIV-1 comprises three groups, the main (M group), O (outlier) and N (non-M, non-O). The M group, divided into 11 subtypes, is responsible for the global HIV-1 pandemic. Recombination between M subtypes has resulted in the generation of multiple circulating recombinant forms (CRFs) consisting of mosaic lineages. Most subtypes and CRFs are represented in Africa, whereas predominance of one or a few subtypes was reported initially elsewhere. This finding reflects the African origin of the epidemic. In western countries, where the B subtype is predominant, there is a steep increase in non B-subtypes and CRFs, while new recombinants emerge worldwide. Travellers contribute to the spread of HIV-1 genetic diversity worldwide, and in the developing world migration of rural populations and civil war are additional contributing factors. The spreading of HIV-1 variants has implications for diagnostic, treatment, and vaccine development.

Molecular epidemiology of HIV-1 genetic forms and its significance for vaccine development and therapy

Since their initial expansion in human beings roughly seven decades ago in central Africa, the HIV-1 pandemic strains have diversified extensively through mutation and recombination. 24 circulating genetic forms of the main HIV-1 group are presently recognised, including 11 subtypes or sub-subtypes and 13 circulating recombinant forms. New genetic forms are being introduced in different areas of the world, changing the molecular epidemiology of the infection. It is generally agreed that the control of the HIV-1 pandemic requires the development of vaccines that efficiently protect against the range of HIV-1 genetic forms. The introduction of effective antiretroviral therapies in areas of high HIV-1 prevalence may also contribute to the control of the pandemic, as has been documented in developed countries. Efficient targeting of the extensive genetic diversity of HIV-1 constitutes one of the major challenges in present efforts against the pandemic, although the significance of HIV-1 genetic forms for vaccine development and therapy remains to be defined.