Molecular epidemiology of human immunodeficiency virus type 1 sub-subtype A3 in Senegal from 1988 to 2001

Faster progression to AIDS and AIDS-related death among seroincident individuals infected with recombinant HIV-1 A3/CRF02_AG compared with sub-subtype A3

BACKGROUND

Human immunodeficiency virus type 1 (HIV-1) is divided into subtypes and circulating recombinant forms (CRFs) but the impact of subtype/CRF on disease progression is not fully understood.

METHODS

We determined the HIV-1 subtype/CRF of 152 seroincident individuals from Guinea-Bissau, based on the C2-V3 region of env. Disease progression was measured as time from estimated seroconversion to AIDS and AIDS-related death. Hazard ratios (HRs) were calculated using a Cox proportional hazard model, adjusting for gender and age at seroconversion.

RESULTS

The major subtypes/CRFs identified were CRF02_AG (53%), A3 (29%), and A3/02 (a recombinant of A3 and CRF02_AG) (13%). Infection with A3/02 was associated with a close to 3-fold increased risk of AIDS and AIDS-related death compared to A3 (HR = 2.6 [P = 0.011] and 2.9 [P = 0.032], respectively). The estimated time from seroconversion to AIDS and AIDS-related death was 5.0 and 8.0 years for A3/02, 6.2 and 9.0 years for CRF02_AG, and 7.2 and 11.3 years for A3.

CONCLUSION

Our results show that there are differences in disease progression between HIV-1 A-like subtypes/CRFs. Individuals infected with A3/02 have among the fastest progression rates to AIDS reported to date. Determining the HIV-1 subtype of infected individuals could be important in the management of HIV-1 infections.

HIV-1 molecular epidemiology in Guinea-Bissau, West Africa: origin, demography and migrations

The HIV-1 epidemic in West Africa has been dominated by subtype A and the recombinant form CRF02_AG. Little is known about the origins and the evolutionary history of HIV-1 in this region. We employed Maximum likelihood and Bayesian methods in combination with temporal and spatial information to reconstruct the HIV-1 subtype distribution, demographic history and migration patterns over time in Guinea-Bissau, West Africa. We found that CRF02_AG and subsubtype A3 were the dominant forms of HIV-1 in Guinea-Bissau and that they were introduced into the country on at least six different occasions between 1976 and 1981. These estimates also corresponded well with the first reported HIV-1 cases in Guinea-Bissau. Migration analyses suggested that (1) the HIV-1 epidemic started in the capital Bissau and then dispersed into more rural areas, and (2) the epidemic in Guinea-Bissau was connected to both Cameroon and Mali. This is the first study that describes the HIV-1 molecular epidemiology in a West African country by combining the results of subtype distribution with analyses of epidemic origin and epidemiological linkage between locations. The multiple introductions of HIV-1 into Guinea-Bissau, during a short time-period of five years, coincided with and were likely influenced by the major immigration wave into the country that followed the end of the independence war (1963-1974).

Impact of HIV type 1 subtype on drug resistance mutations in Nigerian patients failing first-line therapy

A diverse array of non-subtype B HIV-1 viruses circulates in Africa and dominates the global pandemic. It is important to understand how drug resistance mutations in non-B subtypes may develop differently from the patterns described in subtype B. HIV-1 reverse transcriptase and protease sequences from 338 patients with treatment failure to first-line ART regimens were evaluated. Multivariate logistic regression was used to examine the effect of subtype on each mutation controlling for regimen, time on therapy, and total mutations. The distribution of HIV-1 subtypes included CRF02_AG (45.0%), G (37.9%), CRF06_cpx (4.4%), A (3.6%), and other subtypes or recombinant sequences (9.2%). The most common NRTI mutations were M184V (89.1%) and thymidine analog mutations (TAMs). The most common NNRTI mutations were Y181C (49.7%), K103N (36.4%), G190A (26.3%), and A98G (19.5%). Multivariate analysis showed that CRF02_AG was less likely to have the M41L mutation compared to other subtypes [adjusted odds ratio (AOR) = 0.35; p = 0.022]. Subtype A patients showed a 42.5-fold increased risk (AOR = 42.5, p = 0.001) for the L210W mutation. Among NNRTI mutations, subtype G patients had an increased risk for A98G (AOR = 2.40, p = 0.036) and V106I (AOR = 6.15, p = 0.010), whereas subtype CRF02_AG patients had an increased risk for V90I (AOR = 3.16; p = 0.003) and a decreased risk for A98G (AOR = 0.48, p = 0.019). Five RT mutations were found to vary significantly between different non-B West African subtypes. Further study to understand the clinical impact of subtype-specific diversity on drug resistance will be critically important to the continued success of ART scale-up in resource-limited settings.

HIV-1 subtype distribution in the Gambia and the significant presence of CRF49_cpx, a novel circulating recombinant form

Background

Detailed local HIV-1 sequence data are essential for monitoring the HIV epidemic, for maintaining sensitive sequence-based diagnostics, and to aid in designing vaccines.

Results

Reported here are full envelope sequences derived from 38 randomly selected HIV-1 infections identified at a Gambian clinic between 1991 and 2009. Special care was taken to generate sequences from circulating viral RNA as uncloned products, either by limiting dilution or single genome amplification polymerase chain reaction (PCR). Within these 38 isolates, eight were subtyped as A and 18 as CRF02_AG. A small number of subtype B, C, D viruses were identified. Surprising, however, was the identification of six isolates with subtype J-like envelopes, a subtype found normally in Central Africa and the Democratic Republic of the Congo (DRC), with gag p24 regions that clustered with subtype A sequences. Near full-length sequence from three of these isolates confirmed that these represent a novel circulating recombinant form of HIV-1, now named CRF49_cpx.

Conclusions

This study expands the HIV-1 sequence database from the Gambia and will provide important data for HIV diagnostics, patient care, and vaccine development.

HIV type 1 pol gene diversity and genotypic antiretroviral drug resistance mutations in Malabo, Equatorial Guinea

In this study, HIV strains circulating among military personnel were characterized, in Malabo, the capital city of Equatorial Guinea. One sample was found to be HIV-2 group A while a high degree of genetic diversity was recorded in the pol region of 41 HIV-1-positive samples. CRF02_AG accounted for 53.7% of the strains, and 11 different variants were obtained in the remaining 19 samples: subtype G (n = 3), A3 (n = 2), C (n = 2), CRF26_A5U (n = 2), F2 (n = 1), CRF06 (n = 1), CRF09 (n = 1), CRF11 (n = 1), CRF22 (n = 1), and divergent subtype A (n = 1) and F (n = 1). One strain could not be classified and three were unique recombinants. Analysis of antiretroviral drug resistance mutations revealed two patients each harboring one major mutation, M46I in protease and D67N in reverse transcriptase sequences, respectively. The high genetic diversity and emerging ARV resistance mutations call for frequent surveys and appropriate monitoring of ARV considering the increasing access to ARV in the country.

HIV infection among U.S. Army and Air Force military personnel: sociodemographic and genotyping analysis

Since 1985, the U.S. Department of Defense has periodically screened all military personnel for HIV allowing for the monitoring of the infection in this dynamic cohort population. A nested case-control study was performed to study sociodemographics, overseas assignment, and molecular analysis of HIV. Cases were newly identified HIV infections among U.S. Army and Air Force military personnel from 2000 to 2004. Controls were frequency matched to cases by gender and date of case first positive HIV screening test. Genotyping analysis was performed using high-throughput screening assays and partial genome sequencing. HIV was significantly associated with black race [odds ratio (OR) = 6.65], single marital status (OR = 4.45), and age (OR per year = 1.07). Ninety-seven percent were subtype B and 3% were non-B subtypes (A3, CRF01_AE, A/C recombinant, G, CRF02_AG). Among cases, overseas assignment in the period at risk prior to their first HIV-positive test was associated with non-B HIV subtype infection (OR = 8.44). Black and single military personnel remain disproportionately affected by HIV infection. Most non-B HIV subtypes were associated with overseas assignment. Given the increased frequency and length of assignments, and the expanding HIV genetic diversity observed in this population, there is a need for active HIV genotyping surveillance and a need to reinforce primary HIV prevention efforts.

Dual infection with HIV-1 and HIV-2: double trouble or destructive interference?

HIV-1 and HIV-2 are two related retroviruses and, in regions where both infections are endemic, HIV-1/2 dual infection can occur. Several important questions arise about the interplay between these two viruses in a single host, including: what is the potential for HIV-1–HIV-2 recombinants to form, are there synergistic or inhibitory mechanisms that result in distinct viral replication dynamics when compared with HIV-1 or HIV-2 monoinfected individuals and what are the factors to consider when choosing antiretroviral regimes in HIV-1/2 dual-infected individuals? We summarize the relevant evidence to answer these questions, as well as indentify trends in prevalence and how the natural history of HIV-1/2 dual infection differs from that of HIV-1 or HIV-2 monoinfection. The epidemiological and in vitro evidence pertaining to the question of whether HIV-2 infection may protect against HIV-1 superinfection will also be addressed.

Frequent CXCR4 tropism of HIV-1 subtype A and CRF02_AG during late-stage disease--indication of an evolving epidemic in West Africa

BACKGROUND

HIV-1 is one of the fastest evolving pathogens, and is distinguished by geographic and genetic variants that have been classified into different subtypes and circulating recombinant forms (CRFs). Early in infection the primary coreceptor is CCR5, but during disease course CXCR4-using HIV-1 populations may emerge. This has been correlated with accelerated disease progression in HIV-1 subtype B. Basic knowledge of HIV-1 coreceptor tropism is important due to the recent introduction of coreceptor antagonists in antiretroviral therapy, and subtype-specific differences regarding how frequently HIV-1 CXCR4-using populations appear in late-stage disease need to be further investigated. To study how frequently CXCR4-using populations appear in late-stage disease among HIV-1 subtype A and CRF02_AG, we evaluated the accuracy of a recombinant virus phenotypic assay for these subtypes, and used it to determine the HIV-1 coreceptor tropism of plasma samples collected during late-stage disease in Guinea-Bissau. We also performed a genotypic analysis and investigated subtype-specific differences in the appearance of CXCR4 tropism late in disease.

RESULTS

We found that the recombinant virus phenotypic assay accurately predicted HIV-1 coreceptor tropism of subtype A and CRF02_AG. Over the study period (1997-2007), we found an increasing and generally high frequency of CXCR4 tropism (86%) in CRF02_AG. By sequence analysis of the V3 region of our samples we developed a novel genotypic rule for predicting CXCR4 tropism in CRF02_AG, based on the combined criteria of the total number of charged amino acids and net charge. This rule had higher sensitivity than previously described genotypic rules and may be useful for development of future genotypic tools for this CRF. Finally, we conducted a literature analysis, combining data of 498 individuals in late-stage disease, and found high amounts of CXCR4 tropism for all major HIV-1 subtypes (60-77%), except for subtype C (15%).

CONCLUSIONS

The increase in CXCR4 tropism over time suggests an evolving epidemic of CRF02_AG. The results of the literature analysis demonstrate the need for further studies investigating subtype-specific emergence for CXCR4-tropism; this may be particularly important due to the introduction of CCR5-antagonists in HIV treatment regimens.

Analysis of the diversity of the HIV-1 pol gene and drug resistance associated changes among drug-naïve patients in Burkina Faso

A cross-sectional study was undertaken among drug-naïve HIV patients at the University Hospital in Ouagadougou shortly before and after the introduction of large-scale antiretroviral therapy (ART) in Burkina Faso. Baseline clinical and virological data as well as protease (PR) and 5' reverse transcriptase (RT) sequences from 104 HIV infected patients were analyzed. Genotypic classification revealed the following subtypes and recombinant forms: CRF06_cpx, n = 46 (44.2%); CRF02_AG, n = 39 (37.5%); subtype A, n = 4 (3.8%); CRF09_cpx, n = 2 (1.9%); and unclassified, n = 13 (12.5%). Bootstrap analysis of CRF02_AG and CRF06_cpx viruses showed that >80% had a similar structure to their respective prototypes. The prevalence of primary drug resistance mutations was 12.5%, all mutations arising in the RT sequences in accordance with the dominance of this drug class in Burkina Faso. The mutations were distributed as follows: NRTI (10.6%): M41L (n = 2), D67N (n = 2), K70K/E (n = 2), L210W (n = 1), T215S/Y (n = 2), and K219K/Q (n = 2); NNRTI (6.1%): K103K/N (n = 2), Y181C (n = 2), G190G/A (n = 1), and P236P/L (n = 1). Subtype specific secondary polymorphisms such as K20I and M36I in the PR were observed in almost all patients. Drug resistance mutations occurred at similar frequencies (12.8% and 10.8%, respectively) among patients infected with CRF02_AG and CRF06_cpx. Some subtype specific polymorphisms were observed within important HLA epitopes, including B35, B7, and A2 in the RT, and A*6802 in the PR sequences. The observed resistance mutations are most likely to have been transmitted based on the timing of the study but prior undocumented use of ART cannot be excluded.

Identification and characterization of CRF02_AG, CRF06_cpx, and CRF09_cpx recombinant subtypes in Mali, West Africa

Abstract Multiple HIV-1 subtypes and circulating recombinant forms (CRFs) are known to cocirculate in Africa. In West Africa, the high prevalence of CRF02_AG, and cocirculation of subtype A, CRF01_AE, CRF06_cpx, and other complex intersubtype recombinants has been well documented. Mali, situated in the heart of West Africa, is likely to be affected by the spread of recombinant subtypes. However, the dynamics of the spread of HIV-1 recombinant subtypes as well as nonrecombinant HIV-1 group M subtypes in this area have not been systematically assessed. Herein, we undertook genetic analyses on full-length env sequences derived from HIV-1-infected individuals living in the capital city of Mali, Bamako. Of 23 samples we examined, 16 were classified as CRF02_AG and three had a subsubtype A3. Among the remaining HIV-1 strains, CRF06_cpx and CRF09_cpx were each found in two patients. Comparison of phylogenies for six matched pol and full-length env sequences revealed that two strains had discordant subtype/CRF designations between the pol and env regions: one had A3(pol)CRF02_AG(env) and the other had CRF02_AG(pol)A3(env). Taken together, our study demonstrated the high prevalence of CRF02_AG and complexity of circulating HIV-1 strains in Mali. It also provided evidence of ongoing virus evolution of CRF02_AG, as illustrated by the emergence of more complex CRF02_AG/A3 intersubtype recombinants in this area.

Comparison of heterologous neutralizing antibody responses of human immunodeficiency virus type 1 (HIV-1)- and HIV-2-infected Senegalese patients: distinct patterns of breadth and magnitude distinguish HIV-1 and HIV-2 infections

Neutralizing antibody responses against heterologous isolates in human immunodeficiency virus type 1 (HIV-1) and HIV-2 infections were compared, and their relationships with established clinical markers of progression were examined. Neutralizing responses against 7 heterologous primary isolates and 1 laboratory strain were compared between 32 untreated HIV-1-infected subjects and 35 untreated HIV-2-infected subjects using a pseudotyped reporter virus assay. The breadth of the neutralizing response, defined as the proportion of panel viruses positively neutralized by patient plasma, was significantly greater among HIV-2-infected subjects than among HIV-1-infected subjects. Notably, for fully one-third of HIV-2 subjects, all viruses were effectively neutralized in our panel. Magnitudes of responses, defined as reciprocal 50% inhibitory concentration (IC(50)) titers for positive reactions, were significantly greater among HIV-1-infected subjects than among HIV-2-infected subjects. When plasma samples from HIV-1 patients were tested for cross-neutralization of HIV-2 and vice versa, we found that these intertype responses are very rare and their prevalences comparable in both HIV-1 and HIV-2 infection. The significantly higher magnitude of heterologous responses for HIV-1 compared to HIV-2 prompted us to examine associations with viremia, which is known to be significantly higher in HIV-1 infection. Importantly, there was a significant positive correlation between the IC(50) titer and viral load within both the HIV-1 and HIV-2 groups, suggesting heterologous antibodies may be driven by viral replication. We conclude that HIV-2 infection is characterized by a broad, low-magnitude intratype neutralization response, while HIV-1 is characterized by a narrower but higher-magnitude intratype response and that a significant positive association between the IC(50) titer and viremia is common to both HIV-1 and HIV-2 infections.

Identification and molecular characterization of subsubtype A4 in central Africa

Phylogenetic analysis on partial env sequences of HIV-1-positive samples obtained from sentinel population groups in HIV serosurveillance studies in 1997 and 2002 in the Democratic Republic of Congo (DRC) revealed a high genetic diversity in the number of cocirculating subtypes/CRFs as well as intrasubtype diversity. A cluster of three strains that formed a distinct and well-separated group within the subtype A radiation was observed. To determine a more precise structure of these viruses, the full-length genomes were sequenced. Phylogenetic tree and bootscan analysis showed that all three newly characterized viruses formed a new nonrecombinant lineage that was more closely related to subtype A. The SUDI (Subtype Distance) program showed that the distances of the newly derived HIV-1 sequences to subtype A references fell in the range of distances previously characterized for subsubtypes. According to current nomenclature rules, we have thus designated this new lineage as subsubtype A4. Analysis of viral sequences from other African countries suggests that the A4 strains seem restricted to DRC where they already circulated at the onset of the HIV/AIDS epidemic.

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.