Variability among HIV and SIV strains of African origin.

PIP: HIV-1 and HIV-2 both cause AIDS in humans. Simian immunodeficiency viruses (SIV) are non-human primate lentiviruses and the closest known relatives of the HIVs. They closely parallel HIVs in genomic organization and biologic properties. The authors discuss the known HIVs and SIVs of African origin and describe the variability which exists in the different groups. HIV-1 and HIV-2 share approximately 55-60% amino-acid homology in gag and pol, the genes most highly conserved among related retroviruses. HIV-1 is spread widely throughout the world, while HIV-2 infection appears to be concentrated in West Africa. Rare cases of HIV-2 infection have, however, been identified in Europe and America, usually in individuals connected with West Africa. The authors discuss viral genetic variation and variation of biological phenotype, and findings on HIV-1 and HIV-2 from Zaire, Uganda, Cameroon, Tanzania, Ethiopia, Congo, Ghana, the Gambia, Guinea-Bissau, and Cote d'Ivoire.^ieng

Sensitivity of HIV-antibody assays determined by seroconversion panels.

OBJECTIVES: To determine the sensitivity of HIV-antibody assays for detecting low levels of HIV antibody using seroconversion and other panels containing plasma of varying titres. METHODS: Eight HIV-antibody assays, available under the World Health Organization bulk-procurement agreement, were evaluated on sets of sequential plasma samples derived from 11 individuals who had recently become HIV-infected (seroconversion panels). In addition, two non-seroconversion panels, consisting of low performance (titre) and mixed titre samples were used to further define the sensitivity of the assays. The eight assays included two rapid tests, one simple test, and five enzyme-linked immunosorbent assays (ELISA). RESULTS: On average, the eight assays detected antibody 0.5-4.8 days later than the reference test (Abbott HIV-1/HIV-2 3rd generation ELISA); these differences were statistically significant for six of the eight tests. All tests performed well on the low performance and mixed titre panels. All eight assays also had comparable sensitivity to that of the reference test on a large panel of known positive plasma. The additional risk of missing an infectious unit of blood during seroconversion by using the least sensitive rather than the reference test was estimated to be 1 in 7600 and 1 in 76 million at annual HIV incidence rates of 1 and 0.0001%, respectively. The cost of eliminating this additional risk by using the reference test is between US$ 15,150 and 151 million per unit detected at the above incidence rates. CONCLUSIONS: Although there are differences in sensitivity between the assays when used to test blood from individuals during the course of seroconversion, the differences are small, and all eight tests are appropriate for use as screening tests.

HIV-1 subtype H near-full length genome reference strains and analysis of subtype-H-containing inter-subtype recombinants.

OBJECTIVE: To characterize near-full-length genomes of two HIV-1 subtype H strains. To extend sequence data to include full env and gag, and analyse and redefine, previously documented subtype H strains. DESIGN: Near-full-length genomes of HIV-1 env subtype H strains VI991 and VI997 were amplified, cloned, sequenced, phylogenetically analysed and compared with a panel of 23 HIV-1 group M reference isolates. The mosaic nature of previously published subtype H strains VI557 and CA13 was reanalysed. MATERIALS AND METHODS: Peripheral blood mononuclear cells (PBMC) from individuals harbouring strains VI991 and VI997 were co-cultivated with PHA stimulated donor PBMC. Near-full-length genomes of VI991 and VI997, and gag and env genes of CA13 and VI557, were amplified by polymerase chain reaction, cloned and sequenced. Intersubtype recombination analyses were performed by similarity plot, bootscanning and phylogenetic analysis. RESULTS: Near-full-length clones of HIV-1 VI991 and VI997 are representative of subtype H. They form a phylogenetic cluster with the only previously described subtype H representative HIV-1 90CF056.1, regardless of the genome region analysed. VI557 is redefined as a gag and env subtype H mosaic virus containing unclassified fragments. CA13 is a complex intersubtype recombinant between subtypes A, H and unclassified strains CONCLUSION: Near-full-length genome analysis identified HIV-1 VI991 and VI997 as two new subtype H representatives. These reagents will allow defining and classifying non-recombinant as well as recombinant HIV-1, eventually helping to solve the puzzle of HIV-1 subtypes.

Molecular phylogeny of part of the env gene of HIV-1 strains isolated in Côte d'Ivoire.

OBJECTIVES: To examine the genetic variation of HIV-1 isolates in Abidjan, Côte d'Ivoire, and to determine the extent to which phylogenetic trees based on sequence information of part of the env gene containing the principal neutralizing domain are representative for documenting genetic variability. DESIGN: Phylogenetic comparison of 13 HIV-1 strains isolated from patients in Abidjan with previously documented HIV-1 strains of different geographic origin. METHODS: To sequence a 900 base-pair fragment of the env gene containing V3, V4, V5 and the beginning of gp41 of three to four clones per isolate. Phylogenetic tree analysis was performed with the software package TREECON. RESULTS: Eleven HIV-1 isolates of Abidjan were classified as genotype A, while two were classed as genotypes B and D. Intra-genotype A distances at the nucleotide level were a maximum of 14.1%. Inter-genotype distances between genotype A and genotypes B, C, and D varied from 16.0 to 22.6%. Phylogenetic trees, based on sequence data of a 300 base-pair fragment containing the V3 loop, showed significant differences in tree topology and statistical confidence with phylogenetic trees based on sequence data of the 900 base-pair env fragment. CONCLUSIONS: Genotype A Côte d'Ivoire HIV-1 strains, which comprise 11 out of 13 isolates, predominate in Abidjan, which may indicate a local burst of particular variants. Phylogenetic trees should be interpreted with caution when based on a more limited number of nucleotides, such as the V3 region.

Cross-neutralizing antibodies to HIV-1ANT70 and HIV-1IIIB in sera of African and Belgian HIV-1-infected individuals.

OBJECTIVES: To determine the neutralizing antibody patterns to HIV-1ANT70 (ANT70) and HIV-1IIIB (IIIB) in human sera obtained from HIV-1-infected individuals from different African countries and Belgium. Second, to correlate the presence of neutralizing antibodies in sera and their ability to bind to synthetic peptides derived from eight different HIV-1 V3 loop sequences. DESIGN AND METHODS: Forty sera from Belgium and 88 obtained from seven countries in Africa were tested for their ability to neutralize ANT70 (one of the most genetically divergent HIV-1 isolates documented), and IIIB. Sera found to cross-neutralize both viruses were further challenged with four HIV-1 field isolates. All sera were tested on a panel of V3 loop peptides obtained from different HIV-1 genotypes. RESULTS: Four patterns of sera were identified, including 33 (26%) sera not neutralizing any of the isolates, seven (5%) sera neutralizing only ANT70, 45 (35%) sera neutralizing only IIIB, and 43 (34%) sera cross-neutralizing both isolates. Sera capable of cross-neutralizing both ANT70 and IIIB consistently neutralized other field isolates tested, with a remarkable similarity in neutralizing antibody titre. A significantly higher number of sera cross-neutralizing both ANT70 and IIIB compared with sera lacking neutralizing antibodies, reacted simultaneously in enzyme-linked immunosorbent assays (ELISA) with three or more V3 loop peptides belonging to HIV-1 strains of different genotypes. However, none of the sera cross-neutralizing ANT70 and IIIB were reactive in ELISA with the ANT70 V3 loop peptide. CONCLUSION: These results suggest that despite pronounced genomic variation of the HIV-1ANT70 isolate, there are strongly conserved neutralizing epitopes situated outside the V3 loop that are shared by other HIV-1 isolates. These findings suggest that genetic variation might be surmountable in the design of a polyvalent HIV vaccine, if neutralizing antibodies are found to be correlates of protection in HIV infection.

An inhibition enzyme immunoassay using a human monoclonal antibody (K14) reactive with gp41 of HIV-1 for the serology of HIV-1 infections.

An inhibition enzyme immunoassay (IEIA), using a human monoclonal antibody (K14) reactive with gp41 of HIV-1, was evaluated for its applicability to the serology of HIV-1 infections. Using panels of serum samples from seronegative and confirmed HIV-1-seropositive individuals, it was shown that all the HIV-1-positive samples in a panel from The Netherlands and 97% of the HIV-1-positive samples from Tanzania were identified by this IEIA. Six per cent of the IEIA-positive samples from Tanzania could not be confirmed in other assays. Testing of serial dilutions of serum samples from African individuals with confirmed HIV-1, HIV-2 or HIV(ANI70) infections in the K14 IEIA, indicated that a HIV-1-specific assay based on this principle may be developed.

Algorithms for detecting antibodies to HIV-1: results from a rural Ugandan cohort.

OBJECTIVE: To evaluate an algorithm using two enzyme immunoassays (EIA) for anti-HIV-1 antibodies in a rural African population and to assess alternative simplified algorithms. METHODS: Sera obtained from 7895 individuals in a rural population survey were tested using an algorithm based on two different EIA systems: Recombigen HIV-1 EIA and Wellcozyme HIV-1 Recombinant. Alternative algorithms were assessed using negative or confirmed positive sera. RESULTS: None of the 227 sera classified as unequivocably negative by the two assays were positive by Western blot. Of 192 sera unequivocably positive by both assays, four were seronegative by Western blot. The possibility of technical error cannot be ruled out in three of these. One of the alternative algorithms assessed classified all borderline or discordant assay results as negative had a specificity of 100% and a sensitivity of 98.4%. The cost of this algorithm is one-third that of the conventional algorithm. CONCLUSIONS: Our evaluation suggests that high specificity and sensitivity can be obtained without using Western blot and at a considerable reduction in cost.

PIP: Although the Western blot test is widely used to confirm HIV-1 serostatus, concerns over its additional cost have prompted review of the need for supplementary testing and the evaluation of alternative test algorithms. Serostatus tends to be confirmed with this additional test especially when tested individuals will be informed of their serostatus or when results will be used for research purposes. The confirmation procedure has been adopted as a means of securing suitably high levels of specificity and sensitivity. With the goal of exploring potential alternatives to Western blot confirmation, the authors describe the use of parallel testing with a competitive and an indirect enzyme immunoassay with and without supplementary Western blots. Sera were obtained from 7895 people in the rural population survey and tested with an algorithm based on the Recombigen HIV-1 EIA and Wellcozyme HIV-1 Recombinant; alternative algorithms were assessed on negative or confirmed positive sera. None of the 227 sera classified as negative by the 2 assays were positive by Western blot. Of the 192 identified ass positive by both assays, 4 were found to be seronegative with Western blot. The possibility of technical error does, however, exist for 3 of these latter cases. One of the alternative algorithms assessed classified all borderline or discordant assay results as negative with 100% specificity and 98.4% sensitivity. This particular algorithm costs only one-third the price of the conventional algorithm. These results therefore suggest that high specificity and sensitivity may be obtained without using Western blot and at a considerable reduction in cost.

Isolation and characterization of a new chimpanzee lentivirus (simian immunodeficiency virus isolate cpz-ant) from a wild-captured chimpanzee.

OBJECTIVE: To assess the prevalence of infection with simian immunodeficiency virus (SIV) isolate cpz, a lentivirus closely related to HIV-1, in chimpanzees, and to obtain new SIVcpz isolates. METHODS: Forty-four wild-captured chimpanzees in Belgium and Côte d'Ivoire were tested for HIV and SIV antibodies. Virus was isolated from the peripheral blood lymphocytes of positive animals and characterized by electron microscopy, Western blot and radioimmunoprecipitation assay. RESULTS: One animal had antibodies that cross-reacted with HIV-1. A lentivirus was isolated and referred to as SIVcpz-ant. With regard to molecular weight patterns, SIVcpz-ant differs from SIVcpz-gab' an HIV-1-related virus isolated from a wild-captured chimpanzee in Gabon. The major core protein, the transmembrane and outer membrane glycoproteins of the SIVcpz-ant strain consistently had higher molecular weights. Significantly more HIV-1-positive sera reacted with the envelope proteins of the Gabonese SIVcpz-gab strain than with the SIVcpz-ant strain. CONCLUSIONS: This study shows that natural infection of wild-captured chimpanzees with an HIV-related virus may not be uncommon. The diversity of the two chimpanzee isolates, the different geographical origin and the absence of disease suggest that chimpanzees have not recently become SIVcpz-infected.

Acute HIV illness following blood transfusion in three African children.

Three children are described in whom pre-transfusion samples were HIV-seronegative and post-transfusional samples, obtained within 1 week after transfusion, were HIV-seropositive. Two of them developed a transient fever within 1 week of receiving the blood transfusion, and a transient generalized skin eruption which lasted for about 2 weeks. All three developed persistent generalized lymphadenopathy. One child developed a lumbar herpes zoster 7 months after transfusion. IgM Western blots demonstrated the presence of antibodies to protein bands p17, p24 and p55 in all three children. These three case reports suggest that children who receive a seropositive blood transfusion are at high risk for developing acute manifestations of HIV infection.

Phylogenetic analysis of the env gene of HIV-1 isolates taking into account individual nucleotide substitution rates.

OBJECTIVE: To estimate the relative substitution rate of the individual positions in an alignment of HIV-1 env sequences coding for areas V3, V4, V5, and the beginning of gp41, and to study phylogenetic relationships between HIV-1 strains taking into account these substitution rate estimates. DESIGN: Phylogenetic comparison of 145 HIV-1 strains classified in HIV-1 group M, subtypes A-H and isolated from patients of 24 different geographical origins. METHODS: A new method recently developed for measuring the substitution rates of the individual nucleotides in a sequence alignment was applied to an alignment of env gene sequences. From the resulting substitution rate distribution, an equation was derived that describes the relationship between dissimilarity and evolutionary distance better than equations previously available. Phylogenetic trees were then constructed from matrices of distances computed using this new equation. RESULTS: 'Substitution rate calibration' offers detailed information on the relative substitution rate or variability of the nucleotides in the env gene. A large phylogenetic tree of 145 env gene sequences constructed by neighbour-joining and taking into account the substitution rate spectrum for this gene, clearly shows the existence of the eight subtypes A-H, all supported at a bootstrap level of 90% or higher. Intersubtype distances were between 0.25 and 0.38, which is considerably higher than those found in trees not considering differences in substitution rates among different alignment positions. CONCLUSIONS: Evolutionary distances are seriously underestimated when individual substitution rates are not considered in the estimation evolutionary distances. Furthermore, due to the more accurate estimation of evolutionary distances, naturally occurring HIV-1 intersubtype recombinants could be recognized more easily.

Modeling HIV transfer between dendritic cells and T cells: importance of HIV phenotype, dendritic cell-T cell contact and T-cell activation.

OBJECTIVE: To study the requirements for HIV transfer between dendritic cells (DC) and CD4 T cells, using an in vitro model, combined with flow cytometry. METHODS: Immature DC and macrophages (MA) were generated from monocytes. After infection, DC or MA were cultured alone or with purified CD4 T cells. Intracellular HIV was measured, using (1) the monocyte (MO)-tropic AD8 HIV, endowed with enhanced green fluorescent protein (EGFP); and (2) intracellular staining of laboratory HIV strains and clones from primary isolates. RESULTS: (1) Clone AD8-EGFP infected DC and MA with equal efficiency, but the virus was preferentially transferred from DC to autologous T cells. (2) DC were more productively infected with R5/NSI, as compared to X4/SI, HIV, but both HIV phenotypes were easily transmitted to autologous T4 cells. (3) HIV-infected DC transferred the virus to T cells across a semi-permeable membrane, if the T cells were in contact with non-infected DC. (4) Co-culture of T cells with autologous non-infected DC induced T-cell activation. HIV-infected DC selectively increased HLA-DR on T cells and HLA-DR (+) T cells were preferential targets for HIV transfer. (5) Resting Ba-L-infected CD4 T cells were able to transmit the virus 'inversely' to co-cultured DC. CONCLUSION: HIV transfer between monocyte-derived dendritic cells and autologous CD4 T cells was directly demonstrated using flow cytometry. The transfer proceeded in both directions, depended on cellular contact and was associated with partial T-cell activation. This model, representing relevant in vivo targets of HIV, is useful to further investigate interactions between HIV, DC and T cells, without the need for primary ex vivo DC.

Antibodies to V3 loop peptides derived from chimpanzee lentiviruses and the divergent HIV-1ANT-70 isolate in human sera from different geographic regions.

OBJECTIVE: To study the spread of antibodies to V3 loop peptides of two chimpanzee lentiviruses and the divergent HIV-1ANT-70 isolate (group O) in human sera from different geographic regions, and to compare this with reactions to peptides from known North American (subtype B) and Zaïrean (subtype D) strains. METHODS: A total 2495 HIV-1-antibody-positive sera from nine countries were tested by enzyme-linked immunosorbent assay for antibodies to the V3 loop of 10 HIV/SIV isolates (including MN, SF2, HXB2, RF, MAL, ELI, Z6 and ANT-70 for HIV-1, and cpz-gab and cpz-ant for SIV). RESULTS: In each country, the highest prevalences were observed against the MN peptide (58.8-91.7%). Seroreactivity to other peptides from subtype B were generally lower. Prevalences of antibodies to V3 peptides derived from Zaïrean strains belonging to subtype D were generally lower than to subtype B. Relative high prevalences of sera reactive with the SIVcpz-gab V3 peptide were observed. The lowest rates were seen in Brazil (4.2%) and Belgium (25.7%). Among the African countries, the prevalence rates varied between 30.1 and 67.6%. Prevalence to the V3 loop derived from the SIVcpz-ant strains was much lower. Prevalence of sera reactive to the ANT-70 V3 loop peptide was very low, and the highest rates were observed in Cameroon (10.2%), Niger (6%) and Gabon (4.6%). Only the sera reactive to the ANT-70 V3 loop peptide from Cameroon and Gabon were confirmed on a specific HIVANT-70 Western blot (i.e., presence of antibodies to the envelope protein gp 120). CONCLUSIONS: The extent to which different V3 peptide reactivity patterns reflect the circulation of different HIV-1 strains in a particular population is not yet clear. However, V3 peptide serology using the very specific V3 peptide of the HIVANT-70 is a good indicator of the very aberrant group O in a particular population.

Lack of correlation between V3-loop peptide enzyme immunoassay serologic subtyping and genetic sequencing.

OBJECTIVE: To compare the performance of V3-loop peptide enzyme immunoassay (PEIA) methodologies from four different laboratories for subtyping HIV-1, and to determine the causes for the lack of correlation between V3-loop PEIA serotyping and subtyping by sequencing. MATERIALS AND METHODS: Synthetic peptides derived from the amino-acid consensus sequences of the V3-loop of group M strains representing genetic subtypes A-F as well as reference strains were evaluated in PEIA by four different laboratories for their ability to accurately determine the subtype in a panel of 85 sera obtained from persons infected with known HIV-1 subtypes (28 subtype A, 34 subtype B, four subtype C, 10 subtype D, seven subtype F, one each of subtype H and G). Furthermore, the V3 loop of the corresponding virus was compared with the V3 loop of the peptides used in PEIA. RESULTS: The correlation between HIV-1 subtyping by sequencing and V3-loop PEIA from the different laboratories varied considerably for the different HIV-1 subtypes: subtype A (46-68%), B (38-85%), C (75-100%), D (29-50%), and F (17-57%). A 70% agreement between PEIA and sequencing subtypes was observed for samples with the concordant presence of the same octameric sequences in the V3 loop of the virus and the V3 loop of the peptide used in PEIA; however, only 42% of specimens with different V3-loop octameric viral and peptide sequences yielded concordant results in V3-loop serotyping and genetic subtyping. CONCLUSION: Our results indicate that V3-loop PEIA methodologies used in different laboratories correlate poorly with genetic subtyping, and that their accuracy to predict HIV-1 subtypes in sera of Belgian individuals infected with different HIV-1 subtypes (A, B, C, D, F, G and H) vary considerably. The poor correlation between serotyping and genetic subtyping was partly due to the simultaneous occurrence of subtype-specific octameric sequences at the tip of the V3 loop of viruses belonging to different genetic subtypes.

Differences in early virus loads with different phenotypic variants of HIV-1 and SIV(cpz) in chimpanzees.

OBJECTIVE: A comparative study of the replication kinetics of different HIV-1 variants (including SIV(cpz)) was undertaken to determine which viral characteristics were associated with sustained plasma viraemia in chimpanzees. DESIGN: Plasma samples from chimpanzees infected with six different HIV-1 clade B isolates were compared with plasma samples from SIV(cpz-ant)-infected chimpanzees. METHODS: A pan-clade quantitative competitive reverse transcriptase-polymerase chain reaction assay was developed based on conserved primer sequences recognizing M, N and O human lentiviruses as well as different SIV(cpz) isolates. RESULTS: Important differences between early kinetics in the human lentivirus isolates as well as compared with the chimpanzee isolate SIV(cpz-ant) were observed. R5-dependent non-syncytium-inducing (NSI) isolates (5016, Ba-L, SIV(cpz)) were found to have relatively higher viral loads than the syncytium-inducing (SI), X4-dependent primary (SF2), T cell-adapted (IIIB) or X4/R5 (Han2, DH12) SI primary isolates. CONCLUSION: Infection of chimpanzees with NSI R5-utilizing isolates correlated with persistent viraemia (approximately 10(4) RNA equivalents/ml) in contrast to transient viraemia observed after infection with SI X4-utilizing isolates.

Phylogenetic analysis of gag genes from 70 international HIV-1 isolates provides evidence for multiple genotypes.

OBJECTIVE: To determine the extent of genetic variation among internationally collected HIV-1 isolates, to analyse phylogenetic relationships and the geographic distribution of different variants. DESIGN: Phylogenetic comparison of 70 HIV-1 isolates collected in 15 countries on four continents. METHODS: To sequence the complete gag genome of HIV-1 isolates, build multiple sequence alignments and construct phylogenetic trees using distance matrix methods and maximum parsimony algorithms. RESULTS: Phylogenetic tree analysis identified seven distinct genotypes. The seven genotypes were evident by both distance matrix methods and maximum parsimony analysis, and were strongly supported by bootstrap resampling of the data. The intra-genotypic gag distances averaged 7%, whereas the inter-genotypic distances averaged 14%. The geographic distribution of variants was complex. Some genotypes have apparently migrated to several continents and many areas harbor a mixture of genotypes. Related variants may cluster in certain areas, particularly isolates from a single city collected over a short time. CONCLUSIONS: The genetic variation among HIV-1 isolates is more extensive than previously appreciated. At least seven distinct HIV-1 genotypes can be identified. Diversification, migration and establishment of local, temporal 'blooms' of particular variants may all occur concomitantly.

Interpatient genetic variability of HIV-1 group O.

OBJECTIVE: To analyse the genetic and phylogenetic characteristics of HIV-1 group O viruses. MATERIALS AND METHODS: The env gene, encoding the gp160 glycoprotein, and a partial p24-encoding gag gene fragment of a Cameroonian (CA9) and a Gabonese (VI686) HIV-1 group O virus, isolated from cultured peripheral blood mononuclear cells of symptomatic patients, were sequenced, aligned with other representatives of group O for which the same region has been documented, and genetically and phylogenetically analysed. RESULTS: Phylogenetic analysis of the env gene (gp160) revealed that CA9, VI686, ANT70, and four Ha strains formed a separate cluster, which was supported by 100% of all bootstrap trees. In addition, these seven isolates were part of the same clade in the p24 phylogeny. VAU and MVP5180 may represent two other subtypes. CONCLUSION: We have characterized two group O viruses, originating from Cameroon and Gabon, which show a close evolutionary relationship to ANT70 and four Ha strains based on the entire env gene, suggestive of a first group O subgroup, tentatively named the HIV-1 group O env ANT70 clade or subtype.

Haptoglobin polymorphism, iron metabolism and mortality in HIV infection.

BACKGROUND: Three phenotypes of the antioxidant protein haptoglobin are known: Hp 1-1, Hp 2-1 and Hp 2-2. OBJECTIVES: To investigate the outcome of HIV infection according to haptoglobin type. DESIGN AND METHODS: Haptoglobin phenotypes were determined using starch gel electrophoresis in serum obtained from 653 HIV-infected Caucasians in the AIDS reference centers of Gent (n = 184), Antwerp (n = 309), and Luxembourg (n = 160). Survival was compared between haptoglobin types using Kaplan-Meier curves. Plasma HIV-1 RNA was quantified by reverse transcriptase PCR. Serum iron, transferrin saturation, ferritin, and vitamin C were assayed to evaluate iron-driven oxidative stress in 184 HIV-infected patients and 204 controls. RESULTS: The haptoglobin type distribution amongst the patients (17.6% Hp 1-1, 49.9% Hp 2-1, 32.5% Hp 2-2) corresponded to that of the controls. Kaplan-Meier curves showed a higher mortality for the Hp 2-2 group (P = 0.0001; adjusted mortality risk ratio, 1.78; 95% confidence interval, 1.25-2.54). Median survival time was 11.0 years (Hp 1-1 and Hp 2-1) versus 7.33 years (Hp 2-2). Plasma HIV-1 RNA levels prior to antiviral therapy and their increase over 1 year were highest in Hp 2-2 patients (P = 0.03 and 0.003, respectively). The Hp 2-2 type was associated with higher serum iron, transferrin saturation, and ferritin levels and with low vitamin C concentrations. Furthermore, ferritin concentrations were higher in HIV-infected patients than in controls (P < 0.0001). CONCLUSION: HIV-infected patients carrying the Hp 2-2 phenotype show a worse prognosis, which is reflected by a more rapid rate of viral replication (in the absence of antiviral treatment). They also accumulate more iron and oxidize more vitamin C, suggesting that less efficient protection against haemoglobin/iron-driven oxidative stress may be a direct mechanism for stimulating viral replication.

HIV-1 subtypes and the HIV epidemics in four cities in sub-Saharan Africa.

OBJECTIVE: To describe the distribution of HIV-1 subtypes in two cities with high HIV prevalence (Kisumu, Kenya and Ndola, Zambia) and two with relatively low prevalence (Cotonou, Benin and Yaoundé, Cameroon), and to examine whether the differences in prevalence of HIV infection could be due to the predominance within the infected populations of subtypes with differing efficiency of heterosexual transmission. METHODS: For around 100 randomly selected HIV-positive sera from the general population and 60 from sex workers in each city, the HIV-1 subtype was determined in the envfragment. For between 19 and 52 of the sera from the general population and 20-32 sera from sex workers, the subtype was also determined in the gag fragment. RESULTS: Over 70% of infections in Cotonou, Yaoundé and Kisumu were with subtype A (by env). However, around one-half of subtype A infections in Cotonou and Yaoundé were found to be the circulating recombinant form CRF02_AG when the gag fragment was also examined. A large number of different HIV strains were found in Yaoundé, including some belonging to group O. Over 20% of infections in Kisumu and around 10% in Yaoundé were with isolated intersubtype recombinant forms. All but a few infections in Ndola were with subtype C and no recombinants were found. CONCLUSIONS: The pattern of distribution of subtypes that we found does not suggest that differences in circulating subtypes play a major role in explaining the differences in prevalence of HIV-1 infection between the four cities. The emergence and spread of recombinants requires close surveillance to adapt testing strategies if needed, to inform vaccine development and to ascertain their role in the future spread of HIV.

Epidemiological and molecular characteristics of HIV infection in Gabon, 1986-1994.

OBJECTIVE: To describe trends in the prevalence of HIV-1 infection in different populations in Gabon, and the molecular characteristics of circulating HIV strains. METHODS: Data were collected on HIV prevalence through sentinel surveillance surveys in different populations in Libreville (the capital) and in Franceville. In Libreville, a total of 7082 individuals (hospitalized patients, tuberculosis patients, pregnant women, asymptomatic adults, prisoners) were recruited between 1986 and 1994. In Franceville, we tested 771 pregnant women and 886 healthy asymptomatic adults (1986-1988). Sera were screened for HIV antibodies by enzyme-linked immunosorbent assay (ELISA) and confirmed by Western blot or line immunoassay (LIA). Reactive samples in ELISA were tested for the presence of antibodies to HIV-1 group O viruses by ELISA using V3 peptides from HIV-1 ANT-70 and HIV-1 MVP-5180 followed by confirmation by LIA and a specific Western blot. Seventeen HIV-1 strains were isolated (1988-1993) and a 900 base-pair fragment encoding the env region containing V3, V4, V5 and beginning of gp41 was sequenced and a phylogenetic tree was constructed. RESULTS: HIV prevalence was relatively low and remained stable (0.7-1.6% in pregnant women, 2.1-2.2% in the general population). The prevalence was also stable among prisoners (2.1-2.6%). Among hospitalized and tuberculosis patients prevalence was higher and increased (1.8-12.7% and 1.5-16.2%, respectively). Only three sera had antibodies to HIV-1 group O. The 17 HIV-1 strains represent six different genetic subtypes including type O. CONCLUSION: Our data from 1986 to 1994 show a stable and low HIV prevalence in Gabon, and a high genetic diversity of HIV-1 strains. This, also observed in Cameroon, is in contrast to that found elsewhere in Africa. Differences in rate of spread of HIV infection are probably explained by interplay between numerous factors. The role of different HIV subtypes in the dynamics of the HIV epidemic should be examined further.