Why do HIV-1 subtypes segregate among persons with different risk behaviors in South Africa and Thailand?

HIV and Sexual Risk Among Men Who Have Sex With Men and Women in Asia: A Systematic Review and Meta-Analysis

We performed a systematic review to estimate the proportion of men who have sex with men (MSM) in Asia who are bisexual and compare prevalence of HIV and sexual risk between men who have sex with men and women (MSMW) and men who have sex with men only (MSMO). Forty-eight articles based on 55 unique samples were identified from nine countries in Asia. Bisexual behaviour was common among MSM (pooled prevalence 32.8 %). Prevalence of HIV (pooled OR 0.90; 95 % CI 0.77-1.05), recent syphilis infection (pooled OR 0.99; 95 % CI 0.93-1.06) and unprotected anal intercourse (pooled OR 0.80; 95 % CI 0.57-1.11) were similar between MSMW and MSMO, but heterogeneity was high. MSMW had lower odds of reporting a prior HIV test than MSMO (OR 0.82; 95 % CI 0.70-0.95; p = 0.01, I(2) = 0 %). Targeted interventions are needed to increase uptake of HIV testing among MSMW. Increased reporting of disaggregated data in surveillance and research will help improve understanding of risk in MSMW and inform targeted interventions.

Global Comparison of Drug Resistance Mutations After First-Line Antiretroviral Therapy Across Human Immunodeficiency Virus-1 Subtypes

Background.  Human immunodeficiency virus (HIV)-1 drug resistance mutations (DRMs) often accompany treatment failure. Although subtype differences are widely studied, DRM comparisons between subtypes either focus on specific geographic regions or include populations with heterogeneous treatments. Methods.  We characterized DRM patterns following first-line failure and their impact on future treatment in a global, multi-subtype reverse-transcriptase sequence dataset. We developed a hierarchical modeling approach to address the high-dimensional challenge of modeling and comparing frequencies of multiple DRMs in varying first-line regimens, durations, and subtypes. Drug resistance mutation co-occurrence was characterized using a novel application of a statistical network model. Results.  In 1425 sequences, 202 subtype B, 696 C, 44 G, 351 circulating recombinant forms (CRF)01_AE, 58 CRF02_AG, and 74 from other subtypes mutation frequencies were higher in subtypes C and CRF01_AE compared with B overall. Mutation frequency increased by 9%-20% at reverse transcriptase positions 41, 67, 70, 184, 215, and 219 in subtype C and CRF01_AE vs B. Subtype C and CRF01_AE exhibited higher predicted cross-resistance (+12%-18%) to future therapy options compared with subtype B. Topologies of subtype mutation networks were mostly similar. Conclusions.  We find clear differences in DRM outcomes following first-line failure, suggesting subtype-specific ecological or biological factors that determine DRM patterns.

Increasing HIV-1 molecular complexity among men who have sex with men in Bangkok

In Thailand, new HIV-1 infections are largely concentrated in certain risk groups such as men who have sex with men (MSM), where annual incidence may be as high as 12% per year. The paucity of information on the molecular epidemiology of HIV-1 in Thai MSM limits progress in understanding the epidemic and developing new prevention methods. We evaluated HIV-1 subtypes in seroincident and seroprevalent HIV-1-infected men enrolled in the Bangkok MSM Cohort Study (BMCS) between 2006 and 2011. We characterized HIV-1 subtype in 231 seroprevalent and 194 seroincident subjects using the multihybridization assay (MHA). Apparent dual infections, recombinant strains, and isolates found to be nontypeable by MHA were further characterized by targeted genomic sequencing. Most subjects were infected with HIV-1 CRF01_AE (82%), followed by infections with recombinants (11%, primarily CRF01_AE/B recombinants), subtype B (5%), and dual infections (2%). More than 11 distinct chimeric patterns were observed among CRF01B_AE/B recombinants, most involving recombination within integrase. A significant increase in the proportion of nontypeable strains was observed among seroincident MSM between 2006 and 2011. CRF01_AE and subtype B were the most and least common infecting strains, respectively. The predominance of CRF01_AE among HIV-1 infections in Thai MSM participating in the BMCS parallels trends observed in Thai heterosexuals and injecting drug users. The presence of complex recombinants and a significant rise in nontypeable strains suggest ongoing changes in the genetic makeup of the HIV-1 epidemic in Thailand, which may pose challenges for HIV-1 prevention efforts and vaccine development.

HIV-1 epidemic in the Caribbean is dominated by subtype B

BACKGROUND

The molecular epidemiology of HIV-1 in the Caribbean has been described using partial genome sequencing; subtype B is the most common subtype in multiple countries. To expand our knowledge of this, nearly full genome amplification, sequencing and analysis was conducted.

METHODOLOGY/PRINCIPAL FINDINGS

Virion RNA from sera collected in Haiti, Dominican Republic, Jamaica and Trinidad and Tobago were reverse transcribed, PCR amplified, sequenced and phylogenetically analyzed. Nearly full genomes were completed for 15 strains; partial pol was done for 67 strains. All but one of the 67 strains analyzed in pol were subtype B; the exception was a unique recombinant of subtypes B and C collected in the Dominican Republic. Of the nearly full genomes of 14 strains that were subtype B in pol, all were subtype B from one end of the genome to the other and not inter-subtype recombinants. Surprisingly, the Caribbean subtype B strains clustered significantly with each other and separate from subtype B from other parts of the pandemic.

CONCLUSIONS

The more complete analysis of HIV-1 from 4 Caribbean countries confirms previous research using partial genome analysis that the predominant subtype in circulation was subtype B. The Caribbean strains are phylogenetically distinct from other subtype B strains although the biological meaning of this finding is unclear.

Human immunodeficiency virus 1 subtypes detected in Scottish blood donors

The aim of our study was to determine human immunodeficiency virus 1 subtypes in Scottish blood donors. We were able to document virus subtypes present in this population over a period of 19 years and examine associated risk factors where available. Subtype B was found to be the predominant cause of human immunodeficiency virus 1 infection in Scottish blood donors with subtype C increasing in this population after 2002. Non-B subtypes were found mainly in heterosexuals but also in all other risk categories with the exception of men having sex with men (MSM). Within Scotland there is an increase in transmission via heterosexual contact and the consequential introduction of non-B subtypes.

HIV subtypes in Scotland, 2000-2006

The purpose of this study was to document the dynamics of HIV-1 subtypes in Scotland over a 6-year period. Viral RNA from all-new diagnoses was amplified by nested PCR and sequenced in the gag and/or env regions. Subtype was assigned by phylogenetic analysis, and aligned with demographic data including likely route and geographical origin of infection. We present data on 80% of all new diagnoses in Scotland between April 2000 and April 2006. Within the background of an expanding epidemic, subtype B predominates in men who have sex with men and intravenous drug users but there is a small but consistent number of UK-acquired infections in these risk groups caused by non-B subtypes. In heterosexuals, non-B subtypes acquired abroad, especially Africa, are still the largest group but again UK-acquired numbers are rising. The social and clinical significance of the spread of non-B subtypes in different ethnic and risk groups remains to be established.

Ritonavir-Boosted Tipranavir Demonstrates Superior Efficacy to Ritonavir-Boosted Protease Inhibitors in Treatment-Experienced HIV-Infected Patients: 24-Week Results of the RESIST-2 Trial

BACKGROUND

Tipranavir, a novel protease inhibitor, has demonstrated antiviral activity against protease inhibitor-resistant human immunodeficiency virus type 1 (HIV-1) isolates. The Randomized Evaluation of Strategic Intervention in multi-drug reSistant patients with Tipranavir (RESIST-2) trial is an ongoing, open-label, phase III trial comparing ritonavir-boosted tipranavir (TPV/r) plus an optimized background regimen with an individually optimized, ritonavir-boosted protease inhibitor in treatment-experienced, HIV-1-infected patients.

METHODS

Patients at 171 sites in Europe and Latin America who had received > or = 2 previous protease inhibitor regimens, had triple-antiretroviral class experience, had an HIV-1 RNA level > or = 1000 copies/mL, and had genotypically demonstrated primary protease inhibitor resistance were eligible. After genotypic resistance tests were performed, a protease inhibitor and optimized background regimen were selected before randomization. Patients were randomized to receive either TPV/r or comparator protease inhibitor-ritonavir (CPI/r) and were stratified on the basis of preselected protease inhibitor and enfuvirtide use. Treatment response was defined as a confirmed HIV-1 load reduction > or = 1 log10 less than the baseline value without a treatment change at week 24.

RESULTS

A total of 863 patients were randomized and treated. At baseline, the mean HIV-1 load was 4.73 log10 copies/mL, and the mean CD4+ cell count was 218 cells/mm3. The preplanned 24-week efficacy analyses of 539 patients demonstrated treatment response rates of 41% in the TPV/r arm and 14.9% in the CPI/r arm (intent-to-treat analysis; P<.0001). The mean CD4+ cell count increased by 51 cells/mm3 in the TPV/r arm and by 18 cells/mm3 in the CPI/r arm. The most common adverse events were mild-to-moderate diarrhea, nausea, and headache. Grade 3 or greater elevations in serum transaminase, cholesterol, and triglyceride levels were more frequent in the TPV/r arm.

CONCLUSIONS

TPV/r had superior antiviral activity and increased immunologic benefits, compared with CPI/r, at week 24 among treatment-experienced patients infected with multidrug-resistant HIV-1.

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.

Evolution of human immunodeficiency virus type 1 protease genotypes and phenotypes in vivo under selective pressure of the protease inhibitor ritonavir

We examined the population dynamics of human immunodeficiency virus type 1 pro variants during the evolution of resistance to the protease inhibitor ritonavir (RTV) in vivo. pro variants were followed in subjects who had added RTV to their previously failed reverse transcriptase inhibitor therapy using a heteroduplex tracking assay designed to detect common resistance-associated mutations. In most cases the initial variant appeared rapidly within 2 to 3 months followed by one or more subsequent population turnovers. Some of the subsequent transitions between variants were rapid, and some were prolonged with the coexistence of multiple variants. In several cases variants without resistance mutations persisted despite the emergence of new variants with an increasing number of resistance-associated mutations. Based on the rate of turnover of pro variants in the RTV-treated subjects we estimated that the mean fitness of newly emerging variants was increased 1.2-fold (range, 1.02 to 1.8) relative to their predecessors. A subset of pro genes was introduced into infectious molecular clones. The corresponding viruses displayed impaired replication capacity and reduced susceptibility to RTV. A subset of these clones also showed increased susceptibility to two nonnucleoside reverse transcriptase inhibitors and the protease inhibitor saquinavir. Finally, a significant correlation between the reduced replication capacity and reduced processing at the gag NC-p1 processing site was noted. Our results reveal a complexity of patterns in the evolution of resistance to a protease inhibitor. In addition, these results suggest that selection for resistance to one protease inhibitor can have pleiotropic effects that can affect fitness and susceptibility to other drugs.

Effect of a protease inhibitor-induced genetic bottleneck on human immunodeficiency virus type 1 env gene populations

The initiation of drug therapy or the addition of a new drug to preexisting therapy can have a significant impact on human immunodeficiency virus type 1 (HIV-1) populations within a person. Drug therapy directed at reverse transcriptase and protease can result in dramatic decreases in virus load, causing a contraction in the virus population that represents a potential genetic bottleneck as a subset of virus with genomes carrying resistance mutations repopulate the host. While this bottleneck exerts an effect directly on the region that is being targeted by the drugs, it also affects other regions of the viral genome. We have applied heteroduplex tracking assays (HTA) specific to variable regions 1 and 2 (V1/V2) and variable region 3 (V3) of the HIV-1 env gene to analyze the effect of a genetic bottleneck created by the selection of resistance to ritonavir, a protease inhibitor. Subjects were classified into groups on the basis of the extent of the initial drop in virus load and the duration of virus load reduction. Subjects with a strong initial drop in virus load exhibited a loss of heterogeneity in the env region at virus load rebound; in contrast, subjects with a weak initial drop in virus load exhibited little to no loss of heterogeneity at virus load rebound in either region of env examined. The duration of virus load reduction also affected env populations. Subjects that had prolonged reductions exhibited slower population diversification and the appearance of new V1/V2 species after rebound. The longer reduction of virus load in these subjects may have allowed for improved immune system function, which in turn could have selected for new escape mutants. Subjects with rapid rebound quickly reequilibrated the entry env variants back into the resistant population. When the pro gene developed further resistance mutations subsequent to virus load rebound, no changes were observed in V1/V2 or V3 populations, suggesting that the high virus loads allowed the env populations to reequilibrate rapidly. The rapid equilibration of env variants during pro gene sequence transitions at high virus load suggests that recombination is active in defining the HIV-1 sequence population. Conversely, part of the success of suppressive antiviral therapy may be to limit the potential for evolution through recombination, which requires dually infected cells.

Assays for HIV with improved sensitivity and specificity

Increased knowledge of the human immunodeficiency virus (HIV) and the infection it causes in humans has resulted in an enormous expansion in the understanding of viral parameters and host changes. HIV is a virus which mutates readily and rapidly, presenting many challenges to assay developers, and monitors of therapy and drug-resistance. Prolific viral replication at all the stages of the disease means that an accurate assessment of viral burden, viral load and changes to immune system markers is essential for effective clinical management and treatment. In the present review we have summarised current opinion on the kinetics of HIV infection and the pathogenesis of the disease it causes, and have provided a background to the evolution of HIV assays. Sensitivities and specificities of assays used for anti-HIV and HIV detection have improved, and new assays have been developed employing novel molecular techniques, which are being applied to meet continually evolving demands for more sensitive measurement of an increasing number of parameters. The future of HIV testing is also considered in the light of new knowledge concerning virus dynamics in vivo, the likelihood of the emergence of new subtypes and the changing approach to therapy. Assays will be, on the whole, used to quantify virus and to measure the host reactions to infection, often in the presence of antivirals. Thus, extreme sensitivity and specificity will be required.

Short communication: retrospective study to time the introduction of HIV type 1 non-B subtypes in Lyon, France, using env genes obtained from primary infection samples

Using blood samples from primary HIV-1 infection (PHI) patients obtained in Lyon, France, we characterized the newly transmitted HIV-1 variants in this area during the 1992-1996 period. As PHI samples allowed the precise timing of the transmission event, we were able to date the introduction of non-B subtypes or recombinant forms of the virus in Lyon. Genomic DNA from 18 HIV-1-positive patients at primary infection was used to amplify the full-length env gene by nested PCR; after cloning, the gene was sequenced for subsequent phylogenetic analysis. Several non-B subtypes and recombinant forms of HIV-1 were identified among the 18 patients studied (1 subtype F1, 1 CRF01-AE, 2 subtype G and 2 CRF02-AG). We also found a new J/K recombinant form transmitted in 1995 and never described until now. The introduction of CRF02-AG in Lyon, France, occurred prior to 1992 and six transmission events including non-B subtypes were documented in the following 4 years. Heterosexual contacts appeared as the main introduction pathway for non-B subtypes or recombinant forms. Nevertheless, as transmission of these viruses occurred not only during travel to endemic regions, but also in France or Germany, we conclude that non-B strains entered Europe before the studied period. This retrospective study showed that even if subtype B remained prevalent in the spreading HIV-1 infection in Lyon between 1992 and 1996, non-B subtypes and circulating recombinant forms represented a significantly growing part.

HIV prevention in the era of new treatments

Advances in the treatment of HIV disease in recent years have prompted concern that individuals may regard HIV/AIDS as a less serious threat and consequently will be less committed to safer sex practices. This article reviews studies that have been conducted so far to assess the impact of new treatments for HIV on risk perceptions and behaviors among various population groups. Health practitioners need to be alerted to changing attitudes and preventive behaviors in their community stemming from the new treatments. Suggestions are offered to providers of HIV prevention services on how to address the issue of new treatments and the possibility of increasing complacency about safer sex practices.

Viral Load and CD4+ T Lymphocyte Response to Highly Active Antiretroviral Therapy in Human Immunodeficiency Virus Type 1-Infected Children: An Observational Study

An observational study was performed involving 95 children with vertically transmitted human immunodeficiency virus type 1 infection to assess the sustainability of undetectable viral loads (VLs) and increased CD4+ T lymphocyte percentages after 48 months of highly active antiretroviral therapy (HAART). The median time to achieve a 10% increase in the CD4+ T lymphocyte percentage was 11.01 months. The median time to achieve an undetectable VL was 6.4 months. At the end of the study, 64.2% of the children had achieved an undetectable VL. Of the patients with an initial VL of >3.6 log10 copies/mL, 74.7% had a decrease in the VL of 1 log10 copies/mL. By contrast, of the patients who presented with an initial VL of >4.6 log10 copies/mL, 37.9% had a decrease of >2 log10 copies/mL. Higher VL at baseline, antiretroviral therapy regimens received before HAART, and multiple drug switches while receiving antiretroviral therapy were all inversely associated with an undetectable VL. A CD4+ T lymphocyte percentage of >25% was directly associated with undetectable VL during the follow-up period. In conclusion, first-line HAART induces beneficial virological and immunological outcome responses in children.

The sequential introduction of HIV-1 subtype B and CRF01AE in Singapore by sexual transmission: accelerated V3 region evolution in a subpopulation of Asian CRF01 viruses

The rapid spread of the human immunodeficiency virus type 1 (HIV-1) circulating recombinant form (CRF) 01AE throughout Asia demonstrates the dynamic nature of emerging epidemics. To further characterize the dissemination of these strains regionally, we sequenced 58 strains from Singapore and found that subtype B and CRF01 were introduced separately, by homosexual and heterosexual transmission, respectively. Protein similarity scores of the Singapore CRF01, as well as all Asian strains, demonstrated a complex distribution of scores in the V3 loop--some strains had very similar V3 loop sequences, while others were highly divergent. Furthermore, we found a strong correlation between the loss of a V3 glycosylation site and the divergent strains. This suggests that loss of this glycosylation site may make the V3 loop more susceptible to immune surveillance. The identification of a rapidly evolving population of CRF01AE variants should be considered when designing new candidate vaccines and when evaluating breakthrough strains from current vaccine trials.

Viral load differences in early infection with two HIV-1 subtypes

OBJECTIVES

Information on early HIV-1 infection has come primarily from studies of persons infected with subtype B in North America and Europe; much less is known about other subtypes. The purpose of the present study was to compare the virologic and immunologic parameters following seroconversion among recently-infected persons infected with either of two different HIV-1 subtypes.

METHOD

A prospective cohort study was carried out at methadone treatment clinics administered by the Bangkok Metropolitan Administration, Thailand. A total of 130 HIV-1-infected seroconverters (103 with HIV-1 subtype E and 27 with subtype B) were included in the study. The main outcome measures were serial HIV-1 RNA viral load, natural killer cell percentage, CD4 and CD8 lymphocyte counts since seroconversion.

RESULTS

The demographic and behavioral characteristics of persons with either subtype were similar. Median RNA viral levels at the earliest time within 3 months of seroconversion were more than three times higher for persons infected with subtype E than subtype B (63 100 versus 18 050 copies/ml, P = 0.001). However, this difference decreased over time such that viral loads were similar at 12, 18, and 24 months following seroconversion. The CD4 and CD8 lymphocyte counts were similar in infections with either subtype during the entire period up to 24 months post-seroconversion.

CONCLUSIONS

Higher viral loads associated with subtype E may result from inter-subtype biological differences; however, the epidemiological dynamics of transmission in Bangkok may have also contributed to this phenomenon.

National surveillance of HIV-1 subtypes for England and Wales: design, methods, and initial findings

The HIV-1 infections detected in an ongoing national unlinked anonymous HIV surveillance program were subtyped and analyzed according to demographic and risk characteristics. Of the 893 anti--HIV-1--positive specimens allocated to an exposure group, 70% could be subtyped. Almost 25% of infections subtyped were non-B, mostly subtypes A, C, and D. Non-B infections were rare in homosexual and bisexual men and in drug injectors. Forty percent of infections in heterosexual men attending genitourinary medicine clinics were non-B subtypes; of these, 25% were subtype A infections and 59% were subtype C infections. For female clinic attendees, 61% were non-B subtype infections, of which 48% were subtype A infections and 42% were subtype C infections. Of the clinic attendees born in the United Kingdom and Europe, 14% of the men and 35% of the women were infected with non-B subtypes. In contrast, 78% of infections in antenatal patients were non-B subtypes, of which 61% were subtype A and 29% were subtype C. Extrapolation to the estimated 29,700 prevalent adult infections in the United Kingdom indicates that approximately 8,100 (27%) such infections are non-B subtypes and that these are found almost entirely in heterosexuals. The findings suggest spread of infection of non-B subtypes to heterosexuals born in the United Kingdom from individuals infected in regions of high prevalence.

Continued high HIV-1 incidence in a vaccine trial preparatory cohort of injection drug users in Bangkok, Thailand

BACKGROUND

A large epidemic of HIV-1 subtype B began among injection drug users (IDUs) in Bangkok in 1988. Despite ongoing prevention efforts, HIV-1 prevalence among IDUs remained at 30-50% through the 1990s.

OBJECTIVES

To measure the incidence of HIV-1 infection and related risk factors to guide prevention efforts and to evaluate the feasibility of conducting an HIV vaccine efficacy trial.

DESIGN AND METHODS

A prospective cohort study in which IDUs attending methadone treatment programs in Bangkok were screened during 1995-1996 for enrollment into the study. IDUs found to be HIV-seronegative on two occasions were offered enrollment with follow-up visits every 4 months. On each visit participants were evaluated with a questionnaire and serologic testing.

RESULTS

A total of 1209 HIV-negative IDUs were enrolled. Through the end of 1998, the overall HIV-1 incidence rate was 5.8 (95% confidence interval, 4.8-6.8) per 100 person-years of follow-up. HIV-1 subtypes E and B accounted for 79 and 21% of infections, respectively. On multivariate analysis, HIV-1 seroconversion was primarily associated with the frequency of heroin injection, the sharing of injection equipment, and incarceration, especially with drug injection. Sexual behavior was not associated with increased risk for HIV-1. Risk factors for infection with HIV-1 subtypes E and B were similar.

CONCLUSION

HIV-1 transmission risk remains high among Bangkok IDUs despite methadone treatment and other current prevention strategies. There is an urgent need to address this ongoing epidemic, especially in jails and prisons. This study led to the initiation in 1999 of a phase III HIV-1 vaccine efficacy trial in this population.

Identification of diverse HIV type 1 subtypes and dual HIV type 1 infection in pregnant Ugandan women

Vertical (mother-to-child) transmission accounts for the majority of pediatric HIV-1 infections. Many factors are involved in vertical transmission, however it is not clear which factors are most important for determining whether a mother will transmit HIV-1 to her infant. It has been suggested that HIV-1 subtype may influence vertical transmission and that subtype D viruses may be less likely to be transmitted in this setting. We analyzed HIV-1 gp120 V3 region sequences from the plasma of 20 pregnant Ugandan women of known transmission status who did not receive antiretroviral prophylaxis. V3 regions were cloned, sequenced, and subtyped by phylogenetic analysis. Among 11 women who transmitted HIV-1 to their infants, we detected subtypes A, C, D, and G. Two of the transmitters had dual infection with subtypes A and D. In addition, a third was infected with two distinct strains of subtype G viruses. HIV-1 subtype A and D viruses were found in 9 women who did not transmit the virus to their infants. This study reveals that pregnant Ugandan women harbor diverse HIV-1 subtypes, including women who transmit HIV-1 to their infants. Transmission of HIV-1 with subtype D V3 regions was confirmed in 4 of the 11 transmitters, including 2 who had dual infection with subtype A and D HIV-1.

The explosive human immunodeficiency virus type 1 epidemic among injecting drug users of Kathmandu, Nepal, is caused by a subtype C virus of restricted genetic diversity

An explosive epidemic of human immunodeficiency virus type 1 (HIV-1) has been documented among the injecting drug user population of Kathmandu, Nepal, whose seropositivity rate has risen from 0 to 40% between 1995 and 1997. By using Catrimox to preserve whole-blood RNA at ambient temperature for transportation, HIV-1 envelope V3-V4 sequences were obtained from 36 patients in this group. Analysis of the sequences indicated a homogenous epidemic of subtype C virus, with at least two independent introductions of the virus into the population. Viral diversity was restricted within two transmission subclusters, with the majority of variation occurring in V4. Calculation of the synonymous-to-nonsynonymous mutation ratio (Ks:Ka) across this region showed that significant evolutionary pressure had been experienced during the rapid horizontal spread of the virus in this population, most strongly directed to the region between V3 and V4.

Predominance of HIV-1 subtype A and D infections in Uganda

To better characterize the virus isolates associated with the HIV-1 epidemic in Uganda, 100 specimens from HIV-1-infected persons were randomly selected from each of two periods from late 1994 to late 1997. The 200 specimens were classified into HIV-1 subtypes by sequence- based phylogenetic analysis of the envelope (env) gp41 region; 98 (49%) were classified as env subtype A, 96 (48%) as D, 5 (2.5%) as C, and 1 was not classified as a known env subtype. Demographic characteristics of persons infected with the two principal HIV-1 subtypes, A and D, were very similar, and the proportion of either subtype did not differ significantly between early and later periods. Our systematic characterization of the HIV-1 epidemic in Uganda over an almost 3-year period documented that the distribution and degree of genetic diversity of the HIV subtypes A and D are very similar and did not change appreciably over that time.

Viral subtype and heterosexual acquisition of HIV infections diagnosed in Scotland

OBJECTIVE

As at December 1998, 87% of the estimated 33 million people living with HIV throughout the world resided in Africa and South East Asia. In Scotland (and the United Kingdom), a major public health concern has been that non-B subtypes of HIV which predominate in the regions above might enter the country and spread heterosexually among the indigenous population. The authors conducted an investigation to determine if, and to what extent, such transmission had occurred.

METHODS

Stored blood samples from people who were diagnosed as HIV positive in central Scotland during 1995-7 and who were reported to have acquired their infection heterosexually, were identified. Sequence data were sought from each sample and, where obtained, viral subtype was assigned. For each case, viral subtype was linked to corresponding epidemiological details on heterosexual risk.

RESULTS

Viral sequence was obtained from specimens for 53 of 59 cases. For 43 of the 53 cases, information on region of sexual contact was known. All 19 cases who had a sexual risk in Africa or Asia had a non-B subtype (A, C, or E) while 20 of 24 cases who did not report sexual contact in these regions had a B subtype (p < 0.0001). Of the remaining 10 cases, nine had a subtype B and one a subtype C virus.

CONCLUSION

There is no evidence that non-B viral strains from developing countries have yet disseminated appreciably among indigenous heterosexual men and women within Scotland. Continuing to collect both demographic and molecular data from indigenous heterosexuals who are newly diagnosed with HIV would improve the chances of detecting rapidly any appreciable dissemination of non-B subtypes among this population if it were to occur. Such information would be helpful in informing HIV prevention strategies.

HIV trends in African blood donors

OBJECTIVES

To assess trends over the last 12 years in HIV-1/HIV-2 seroprevalence among blood donors in African nations and to correlate trends with national AIDS policies, with the purpose of preventing future cases.

METHODS

Using collated data of African seroepidemiologic studies published by the U.S. Bureau of the Census, we established a best-fit linear trend, determined by regression analysis of HIV-1 and HIV-2 seroprevalence values for African blood donors against time, with adjustments for sample size of reported studies.

RESULTS

Among 38 nations with sufficient data, 11 showed increases in HIV-1 seroprevalence, six showed decreases and 21 showed no significant changes. Decreases were seen primarily in nations with a high HIV-1 seroprevalence before 1989 (P<0.001, Chi-square). HIV-2 seroprevalence decreased in all nations where it was tested except Nigeria. There was a moderate correlation between decreases in HIV-1 and HIV-2 seroprevalence values (correlation coefficient = 0.39). No significant correlations between HIV policies and subsequent HIV-1 seroprevalence trends among blood donors and HIV patients were detected.

CONCLUSIONS

A great disparity exists in trends in HIV-1 seroprevalence among African nations. HIV-2 seroprevalence is consistently decreasing throughout most of West Africa, the exception being Nigeria. The absence of any significant correlation between HIV seroprevalence trends and healthcare policies suggests that other factors are more influential than national policy in determining such trends and, by extrapolation, trends in AIDS prevalence.

Nationwide surveillance of HIV-1 prevalence and subtype in young Thai men

As part of routine surveillance, an HIV-1 serosurvey of 366,074 members of successive cohorts of young Thai men entering service with the Royal Thai Army (RTA) was conducted between November 1989 and November 1995. We analyzed regional and temporal trends in HIV-1 seroprevalence in young men in Thailand and determined the proportion of infections resulting from subtypes E and B in this population in 1992 and 1995. The prevalence in 1992 was compared with that in 1995 by region and demographic group. The HIV-1 subtype was determined in a random sample of HIV-1-positive specimens in 1992 and 1995 using a V3 peptide enzyme immunoassay. From a peak of 3.7% in 1993, overall seroprevalence declined to 3.0% in 1994 and further in 1995 to 2.5%. Between 1992 and 1995, the absolute decrease in seroprevalence was greatest in the upper North (from 12.5% to 5.3%), where the prevalence has been the highest. Overall, 96.9% and 95.9% of typable specimens were determined to be subtype E in 1992 and 1995, respectively. Decline in HIV-1 seroprevalence among young men in Thailand has continued, which suggests that HIV control programs in Thailand may have been successful in decreasing spread of HIV-1. Almost all HIV-1 infections resulted from subtype E.

V3 sequence diversity of HIV-1 subtype E in infected mothers and their infants

To elucidate genetic characteristics of HIV-1 subtype E involved in vertical transmission, V3 regions of HIV-1 subtype E isolated from 17 infected mothers (M1-M17) and their infants (I1-I17) at 1 month after birth were sequenced after cloned into pCRII vectors. At least three clones of each sample were collected. All mothers were asymptomatic and had been infected through a heterosexual route. Nine infants (I9-I17) showed mild symptomatic and immunosuppression within the first year of life. The interpatient nucleotide distance of mothers and infants in this group (0.065+/-0.008) were of greater diversity than those of a nonimmunosuppression group (0.039+/-0.006) by a significant amount (Fischer's exact test, p = .003). The substitution with asparagine (N) at threonine (T) at position 13 and aspartic acid (D) at position 29 of the V3 sequence were significantly associated with nonimmunosuppression in the first year of life (F-test, p = 0.003). Either a single or multiple viral variants could transmit from mothers to their infants.

HIV type 1 in Thailand, 1994-1995: persistence of two subtypes with low genetic diversity

Extensive transmission of human immunodeficiency virus type 1 (HIV-1) in Thailand began in 1988, resulting in an estimated 800,000 cumulative infections by 1994. During 1994 and 1995, we collected blood specimens from 215 asymptomatic HIV-1-infected people with various risk behaviors from nine locations in all four regions of Thailand. HIV-1 subtypes and genetic heterogeneity were determined for 214 strains by a combination of direct DNA sequencing (n = 95), subtype-specific oligonucleotide probe testing (n = 201), and V3-loop peptide enzyme immunoassay (PEIA) (n = 214). All strains were either env subtype E (175; 81.8%) or B (39; 18.2%). Of the subtype B isolates, 37 (94.9%) were B' and 2 (5.1%) were more typical North American-like B strains (most subtype B strains in Thailand are part of a distinct subcluster within the subtype B branch on phylogenetic trees, termed B'; formerly Thai B or BB). Of 149 viruses from people with sexual risk behaviors from all regions, 146 (98.0%) were subtype E. Of 65 viruses from injecting drug users (IDUs), 29 (44.6%) were subtype E and 36 (55.4%) were subtype B, including 35 B' strains. There was regional variation in the proportions of subtypes E and B' among IDUs. The intrasubtype nucleotide divergence within the V3 and flanking regions of the env gene (mid-C2 to the start of the V4 region) was low (5.7% for subtype E and 3.1% for subtype B') compared with other HIV-1 group M subtypes from different countries. These findings of two subtypes with low heterogeneity indicate that Thailand may be a desirable setting for evaluating candidate HIV-1 vaccines. The mix of subtype E and B' strains among IDUs also offers the opportunity to study phenotypic differences between the two subtypes.

HIV type 1 V3 serotyping of Tanzanian samples: probable reasons for mismatching with genetic subtyping

HIV-1 V3 serotyping is used to classify immunodeficiency viruses on the basis of antibody binding to V3 peptides derived from env genetic subtypes. Although it shows a reasonable overlap, it has been reported to be distinct from viral genetic subtypes. The aim of this study is to determine the feasibility of HIV-1 serotyping to predict genetic subtypes in an East African setting, where multiple HIV-1 subtypes have coexisted for many years. HIV-1 genetic subtypes of 86 AIDS patients in Mbeya Town, southwest Tanzania, were determined, using env nucleic acid sequencing as the basis for comparison. Those data were compared with V3 serotyping results obtained by four different methodologies. Four HIV-1 genetic subtypes were identified, including A (25, 29%), C (47, 55%), D (13, 15%), and G (1, 1%). The sensitivity and specificity of those serotyping assays varied considerably: sensitivity for genetic subtype A (40-48%), C (52-96%), and D (9-31%); and specificity for genetic subtype A (77-95%), C (46-63%), and D (97-100%). We further tried to identify reasons for the discrepancies between serotyping results and genetic subtypes. By means of logistic regression analysis three amino acid residues within the V3 loop (positions 12, 13, and 19; V, H, and A for serotype A, I, R, and T for serotype C) were found to be most important for antibody binding; a deviation from the subtype-specific amino acids was highly related to mismatched results. In addition, we have shown that phenetic analysis of V3 amino acid sequence data could be used to predict the majority of V3 serotypes (93-94%). Our data demonstrated that for the majority of specimens HIV-1 V3 serotyping results closely match the subtype of the analyzed sample as revealed by the V3 loop amino acid sequence. However, our data demonstrate that HIV-1 serotyping is not sufficiently accurate to predict genetic subtypes in Tanzania, where subtypes A, C, D, and G are circulating. This was due to highly similar amino acid sequences throughout the prevalent genetic subtypes, which caused the inability of HIV-1 V3 serotyping to differentiate subtype A from C as well as D from C. Instead, the serotyping results reflect the frequency distribution of V3 serotypes. To investigate HIV-1 genetic subtypes in population-based studies in this African setting additional or modified algorithms are needed.

Human immunodeficiency virus type 1 strains of subtypes B and E replicate in cutaneous dendritic cell-T-cell mixtures without displaying subtype-specific tropism

A report that genetic subtype E human immunodeficiency virus type 1 (HIV-1) strains display a preferential tropism for Langerhans cells (epidermal dendritic cells [DCs]) compared to genetic subtype B strains suggested a possible explanation for the rapid heterosexual spread of subtype E strains in Thailand (L. E. Soto-Ramirez et al., Science 271:1291-1293, 1996). In an independent system, we applied subtype E and B isolates to skin leukocytes, since skin is a relevant model for the histologically comparable surfaces of the vagina and ectocervix. Isolates of both HIV-1 subtypes infected DC-T-cell mixtures, and no subtype-specific pattern of infection was observed. Purified DCs did not support the replication of strains of either subtype B or E. Our findings do not support the conclusion that subtype E strains have a preferential tropism for DCs, suggesting that other explanations for the rapid heterosexual spread of subtype E strains in Asia should be considered.

Evaluation of a quantitative double ELISA strategy for confirmation and differentiation of HIV infection

The current HIV pandemic is complicated by the spread of distinct types and subtypes of HIV. The currently used conventional diagnostic tests have shown limitations in the detection of antibodies against all HIV-1 subtypes, as demonstrated by recent identification of HIV-1 subtype O. To evaluate quantitatively the diagnostic potential of a double ELISA strategy for the detection and partial differentiation of HIV-1, HIV-1 subtype O and HIV-2 infections blood samples were examined at five different test centers: Blantyre, Malawi; Abidjan and Daloa, Ivory Coast; Yaoundé, Cameroon; Munich, Germany. All tests results, including ELISA extinction values and Western blot profiles, were forwarded to Munich for final interpretation. An indirect anti-HIV-1/2 ELISA and a competitive anti-HIV-1 ELISA were used in combination for the initial screening of blood specimens. All anti-HIV positive and anti-HIV negative samples were subjected to immunoblot analysis. Independent of the diversity of the extinction profiles, and of the test manufacturer, the quantitative evaluation of the ELISA extinction values could define two extinction areas with a 100% predictive value for HIV-1 seropositivity and HIV seronegativity; extinction values > 2 by the indirect ELISA and < 0.2 by the competitive ELISA for an anti-HIV-1 subtype A to I positive result; extinction values < 0.2 by the indirect ELISA and > 1.0 by the competitive ELISA for an anti-HIV negative result. Additionally, the quantitative evaluation of the extinction profile provides partial information on the HIV-1 subtype as far as the distinction in group M and group O is concerned. In conclusion, the quantitative evaluation of this double ELISA strategy can reduce the number of blood specimens that require additional confirmatory testing in developing countries and can be superior to the immunoblot method during early seroconversion.