Infection with the human immunodeficiency virus type 2

Antiretroviral therapy and drug resistance in human immunodeficiency virus type 2 infection

One to two million people worldwide are infected with the human immunodeficiency virus type 2 (HIV-2), with highest prevalences in West African countries, but also present in Western Europe, Asia and North America. Compared to HIV-1, HIV-2 infection undergoes a longer asymptomatic phase and progresses to AIDS more slowly. In addition, HIV-2 shows lower transmission rates, probably due to its lower viremia in infected individuals. There is limited experience in the treatment of HIV-2 infection and several antiretroviral drugs used to fight HIV-1 are not effective against HIV-2. Effective drugs against HIV-2 include nucleoside analogue reverse transcriptase (RT) inhibitors (e.g. zidovudine, tenofovir, lamivudine, emtricitabine, abacavir, stavudine and didanosine), protease inhibitors (saquinavir, lopinavir and darunavir), and integrase inhibitors (raltegravir, elvitegravir and dolutegravir). Maraviroc, a CCR5 antagonist blocking coreceptor binding during HIV entry, is active in vitro against CCR5-tropic HIV-2 but more studies are needed to validate its use in therapeutic treatments against HIV-2 infection. HIV-2 strains are naturally resistant to a few antiretroviral drugs developed to suppress HIV-1 propagation such as nonnucleoside RT inhibitors, several protease inhibitors and the fusion inhibitor enfuvirtide. Resistance selection in HIV-2 appears to be faster than in HIV-1. In this scenario, the development of novel drugs specific for HIV-2 is an important priority. In this review, we discuss current anti-HIV-2 therapies and mutational pathways leading to drug resistance.

HIV-2 A-subtype gp125c₂-v₃-c₃ mutations and their association with CCR5 and CXCR4 tropism

The early events of the HIV replication cycle involve the interaction between viral envelope glycoproteins and their cellular CD4-chemokine (CCR5/CXCR4) receptor complex. In this study, for the first time, the HIV-2 A-subtype gp125(C2-V3-C3) mutations and their tropism association were characterized by analyzing 149 HIV-2 sequences from the Los Alamos database. The analysis has strengthened the importance of C2-V3-C3 region as a determinant factor for co-receptor selection. Moreover, statistically significant correlations were observed between C2-V3-C3 mutations, and several correlated mutations were associated with CXCR4 and CCR5 co-receptor usage. A dendrogram showed two distinct clusters, with numerous associated mutations grouped, thus dividing CCR5- and CXCR4-tropic viruses. Fourteen X4-tropic virus mutations, all in V3 and C3 domains and forming highly significant subclusters, were found. Finally, R5 associations, two strong subclusters were observed, grouping several C2-V3-C3 mutated positions. These data indicate the possible contribution of C2-V3-C3 mutational patterns in regulating HIV-2 tropism.

Seronegative HIV-1 infection: a review of the literature

HIV-1-specific antibodies can be detected in HIV-1-positive patients within weeks of primary infection. Rare cases have been reported of patients who are persistently seronegative despite evidence of HIV-1 infection. We present a retrospective review of the clinical, virologic and immunologic characteristics of 25 persistently seronegative patients whose cases have been published to date and postulate a biologic mechanism for this phenomenon.

Regulation of HIV-1 transcription in cells of the monocyte-macrophage lineage

Human immunodeficiency virus type 1 (HIV-1) has been shown to replicate productively in cells of the monocyte-macrophage lineage, although replication occurs to a lesser extent than in infected T cells. As cells of the monocyte-macrophage lineage become differentiated and activated and subsequently travel to a variety of end organs, they become a source of infectious virus and secreted viral proteins and cellular products that likely initiate pathological consequences in a number of organ systems. During this process, alterations in a number of signaling pathways, including the level and functional properties of many cellular transcription factors, alter the course of HIV-1 long terminal repeat (LTR)-directed gene expression. This process ultimately results in events that contribute to the pathogenesis of HIV-1 infection. First, increased transcription leads to the upregulation of infectious virus production, and the increased production of viral proteins (gp120, Tat, Nef, and Vpr), which have additional activities as extracellular proteins. Increased viral production and the presence of toxic proteins lead to enhanced deregulation of cellular functions increasing the production of toxic cellular proteins and metabolites and the resulting organ-specific pathologic consequences such as neuroAIDS. This article reviews the structural and functional features of the cis-acting elements upstream and downstream of the transcriptional start site in the retroviral LTR. It also includes a discussion of the regulation of the retroviral LTR in the monocyte-macrophage lineage during virus infection of the bone marrow, the peripheral blood, the lymphoid tissues, and end organs such as the brain. The impact of genetic variation on LTR-directed transcription during the course of retrovirus disease is also reviewed.

Viruses

Viral infections are an important and often unrecognized component of disease in immunocompromised patients. The diagnosis and management of viral infections have expanded largely because of new quantitative molecular diagnostic assays. Well-recognized pathogens such as herpes simplex virus (HSV), cytomegalovirus (CMV), and respiratory viruses have been joined by newly recognized pathogens such as BK virus, human herpesvirus-6 (HHV-6), and human metapneumovirus in this highly susceptible patient population. The role of Epstein-Barr virus (EBV) and Human herpesvirus-8 (HHV-8) in lymphoproliferative diseases also continue to be clarified. As a result, the management of viral infections in patients with hematologic malignancies continues to be a growing challenge for the clinician.

Alternative algorithms for human immunodeficiency virus infection diagnosis using tests that are licensed in the United States

Serodiagnosis of human immunodeficiency virus (HIV) infection in the United States has traditionally relied on a sequential two-test algorithm: an initial screen with an enzyme immunoassay (EIA) and reflex testing of EIA-reactive specimens with a more specific supplemental test such as Western blotting or immunofluorescence. The supplemental tests are tedious, subjective, and expensive. In addition, there have been major improvements in the performance and accuracy of the EIA tests as well as the introduction of rapid serologic tests (RT) and HIV nucleic acid amplification tests (NAAT). Related to these improvements is the possibility that alternative algorithms using combinations of currently approved HIV tests may function as well as if not better than the current algorithm, with more flexibility, improved accuracy, and lower cost. To this end, we evaluated the performance of 12 currently licensed tests and 1 in-house HIV test (6 EIA, 4 RT, and 3 NAAT) on panels of plasma samples from HIV-infected (n = 621 HIV type 1 [HIV-1] and 34 HIV-2) and uninfected (n = 513) people and of sequential specimens from people early in seroconversion (183 specimens from 15 patients). Test combinations were analyzed in two dual-test (sensitivity-optimized and specificity-optimized) algorithms and in a three-test (tie-breaking) algorithm, and performance was compared to the conventional algorithm. The results indicate that alternative algorithm strategies with currently licensed tests compare favorably with the conventional algorithm in detecting and confirming established HIV infection. Furthermore, there was a lower frequency of discordant or indeterminate results that require follow-up testing, and there was improved detection of early infection.

Identification of HIV type 1 group N infections in a husband and wife in Cameroon: viral genome sequences provide evidence for horizontal transmission

HIV-1 is classified into three groups, M (major), N (non-M non-O), and O (outlier); each group arose from a separate transmission of SIVcpz into humans. HIV-1 group N was recently discovered and infections with this virus are rare with only eight documented cases. All group N infections have been found in Cameroon and there is no evidence of direct linkage between the infected patients. We report here the identification of HIV-1 group N infections in a husband and wife. The group N infection in the husband, 1131-03, was identified first based on seroreactivity in peptide EIAs and confirmed by PCR amplification of group N viral sequences. Subsequently the wife, 1015-04, was evaluated and confirmed to also be infected with a group N virus. Near full-length viral genomes were amplified and sequenced from each patient's specimen. The low level of diversity between the two viral sequences provides evidence of horizontal transmission of group N from one spouse to the other. Patient 1131-03 was receiving antiviral therapy consisting of reverse transcriptase inhibitors; the treatment appears effective for suppression of group N viral replication based on apparently low viral load in plasma specimens collected from the patient and the absence of drug resistance mutations in RT sequences amplified from 1131-03. This report brings to 10 the number of group N infections identified and to 5 the number of group N genomes sequenced. Although group N infections continue to be rare, group N is a pathogenic virus and its prevalence needs to be monitored.

Disruption of the upper female reproductive tract epithelium by nonoxynol-9

Spermicides containing nonoxynol-9 (N-9) may increase HIV transmission. In women, intravaginal N-9 is found in the uterus shortly after its insertion. Exposure of the female upper reproductive tract to N-9 may alter epithelial integrity, thereby increasing HIV transmission risk. Our goal was to characterize the histological effects of N-9 on uterine epithelium in an animal model. Female mice were exposed to intravaginal or intrauterine Advantage-S (N-9), Replens, K-Y(R) jelly or water. After various exposure times, mice were sacrificed and stained uterine tissue sections were analyzed by a pathologist blinded to treatment.Intravaginal and intrauterine N-9 administration resulted in disruption of uterine epithelium compared to Replens, K-Y jelly or water. N-9 caused rapid (within 10 min), focal, uterine epithelial sloughing and complete epithelial loss within 24 h. Epithelial regeneration began 48 h after exposure N-9 and was completely restored within 72 h; the new epithelial layer, however, was composed of cuboidal cells instead of normally present columnar cells. In addition, hemorrhage and necrosis were present are all time points examined. Our results demonstrate for the first time that N-9 has a deleterious effect on uterine epithelium. Although these results were observed in a mouse model, similar disruption of the upper reproductive tract epithelium in women by N-9 may facilitate HIV infection and serve as an unrecognized portal of human HIV transmission.

Protein phosphatase 2A activates the HIV-2 promoter through enhancer elements that include the pets site

Human immunodeficiency virus type 2 (HIV-2) gene expression is regulated by upstream promoter elements, including the peri-Ets (pets) site, which mediate enhancer stimulation following treatment with the phorbol ester 12-O-tetradecanoylphorbol-13-acetate (TPA). We previously showed that the oncoprotein DEK binds to the pets site in a site-specific manner. In this report, we show that binding to the HIV-2 pets site is modulated by treatment of U937 monocytic cells with TPA, an activator of protein kinase C. TPA treatment resulted in a reduction in the levels of DEK and the formation of a faster migrating pets complex in gel shift assays. We show further that the actions of TPA on pets binding can be duplicated by phosphatase treatment of nuclear proteins and is blocked with okadaic acid, a protein phospatase-2A (PP2A) inhibitor. Finally, we demonstrate that ectopic expression of the catalytic domain of PP2A can activate the HIV-2 enhancer/promoter alone or in synergy with TPA, an effect mediated in part through the pets site. These results suggest that, through an interaction with the protein kinase C pathway, PP2A is strongly involved in regulating HIV-2 enhancer-mediated transcription. This is a consequence of its effects on DEK expression and binding to the pets site, as well as its effects on other promoter elements. These findings have implications not only for HIV-2 transcription but also for multiple cellular processes involving DEK or PP2A.

HIV-2 infection with cerebral toxoplasmosis and lymphomatoid granulomatosis

A Nigerian man had acute onset of headache and vertigo due to a cerebellar mass. A brain biopsy of the mass revealed toxoplasmosis despite repeated negative HIV-1 serology. The presence of an opportunistic infection and his country of origin raised the suspicion for HIV-2; this was confirmed by positive HIV-2 serology. Despite his preliminary pathological diagnosis, results of physiological magnetic resonance imaging (MRI) (perfusion MRI and proton magnetic resonance spectroscopy) were not typical for toxoplasmosis. The lesion showed a biochemical and perfusion pattern that was intermediate for infectious and neoplastic processes. Further neuropathology confirmed a secondary diagnosis of lymphomatoid granulomatosis.

The economics of HIV vaccines: projecting the impact of HIV vaccination of infants in sub-Saharan Africa

OBJECTIVES

(i) To project vaccine parameters, economic consequences and market size associated with HIV-1 vaccination of infants in sub-Saharan Africa through the Expanded Program on Immunisation (EPI); and (ii) to assess threshold values for price and effectiveness.

STUDY DESIGN AND METHODS

Cost-effectiveness analysis using a decision-analysis model linking epidemiological data with economic information. Epidemiological data on the burden of disease of HIV were obtained from the World Health Organization (WHO) and the Joint United Nations Programme on HIV/AIDS. The decision analysis model was constructed using estimates of lifetime chances of HIV infection. To assess threshold values for price and effectiveness, a maximum value for cost effectiveness in developing countries of $US100 was used in the base case. One-way and multivariate sensitivity analysis was performed on relevant parameters, assessing the impact of these parameters on the results of our analysis. In the base case, health benefits and consequences were discounted at a rate of 3%.

STUDY PERSPECTIVE

Societal.

RESULTS

According to our model, introduction of an HIV-1 vaccine in the EPI would result in the vaccination of 8717112 infants in sub-Saharan Africa per year. This corresponds to the prevention of 1839355 cases of HIV per year, gaining 16461800 disability-adjusted life years (DALYs). The cost-effectiveness ratio of the intervention would be $US3.4 per DALY gained (1998 values) at a vaccine price in the base case of $US5. At the same price the estimated size of the market would be approximately $US44536111 per year.

CONCLUSION

If technological and financial problems associated with the development of an HIV vaccine can be solved, HIV vaccination in Africa could be both cost effective and potentially profitable.

Risk factors for HIV-2 seropositivity among older people in Guinea-Bissau. A search for the early history of HIV-2 infection

Because the seroprevalence of HIV-2 has been shown to be high in older age groups, we conducted a survey of all persons aged 50 years or over in two districts in Bissau, investigating the presence of HIV antibodies and possible risk factors for HIV infection with a particular emphasis on age, the impact of the war of independence (1963-74), traditional marital and extramarital sex patterns, blood contact and contact with monkeys. In 670 participants, the HIV-2 prevalence was 14.3%; 16.1% in women and 12.3% in men. The HIV-1 prevalence was only 0.5% (3/670). The HIV-2 prevalence peaked for men in the 60-69 years age group, and for women in the 50-59 years age group, declining markedly in the following age group for both men and women (OR = 0.09 (0.01-0.51), OR = 0.37 (0.15-0.82), respectively). This pattern could be due to differential mortality for HIV-2 infected individuals or to a cohort effect for a generation who were sexually active at the time of the war of independence in the 1960s and early 1970s in Bissau. Supporting the link with the colonial army, women who had had sex with a white man had a higher seroprevalence (OR = 3.63 (1.12-11.24)). The ethnic group indigenous to Bissau city had a much lower prevalence, but demographic and cultural risk factors such as marital status, religion, education and having lived outside Bissau were not associated with HIV-2. In the multivariate analyses for women, variables related to extramarital sex or prostitution (having sex with a white man, having lived in Senegal, not living with husband, and not marrying first sexual partner) were associated with higher risk. For men, previous spouses who had died or had divorced were associated with higher prevalence. Having married the first sexual partner was protective against HIV-2 infection for both men (OR = 0.29 (0.09-0.76)) and women (OR = 0.19 (0.04-1.00)). Hospitalizations, possibly due to transfusions, tended to be associated with higher risk, but only for women (OR = 1.83 (0.97-3.48)). The focus of the HIV-2 epidemic in Guinea-Bissau is likely to be endogenous, and the war of independence and the colonial army with its associated prostitution may have played an important part in propagating the virus.

Functional differences between the long terminal repeat transcriptional promoters of human immunodeficiency virus type 1 subtypes A through G

The current human immunodeficiency virus type 1 (HIV-1) shows an increasing number of distinct viral subtypes, as well as viruses that are recombinants of at least two subtypes. Although no biological differences have been described so far for viruses that belong to different subtypes, there is considerable sequence variation between the different HIV-1 subtypes. The HIV-1 long terminal repeat (LTR) encodes the transcriptional promoter, and the LTR of subtypes A through G was cloned and analyzed to test if there are subtype-specific differences in gene expression. Sequence analysis demonstrated a unique LTR enhancer-promoter configuration for each subtype. Transcription assays with luciferase reporter constructs showed that all subtype LTRs are functional promoters with a low basal transcriptional activity and a high activity in the presence of the viral Tat transcriptional activator protein. All subtype LTRs responded equally well to the Tat trans activator protein of subtype B. This result suggests that there are no major differences in the mechanism of Tat-mediated trans activation among the subtypes. Nevertheless, subtype-specific differences in the activity of the basal LTR promoter were measured in different cell types. Furthermore, we measured a differential response to tumor necrosis factor alpha treatment, and the induction level correlated with the number of NF-kappaB sites in the respective LTRs, which varies from one (subtype E) to three (subtype C). In general, subtype E was found to encode the most potent LTR, and we therefore inserted the core promoter elements of subtype E in the infectious molecular clone of the LAI isolate (subtype B). This recombinant LAI-E virus exhibited a profound replication advantage compared with the original LAI virus in the SupT1 T-cell line, indicating that subtle differences in LTR promoter activity can have a significant impact on viral replication kinetics. These results suggest that there may be considerable biological differences among the HIV-1 subtypes.

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.

Potent inhibition of human immunodeficiency virus type 1 (HIV-1) gene expression and virus production by an HIV-2 tat activation-response RNA decoy

Tat activation-response region (TAR) decoys have been developed for use in gene therapy for people infected with human immunodeficiency virus type 1 (HIV-1). When a TAR RNA decoy is overexpressed, it will bind Tat, thus leaving less of this crucial protein to bind to and activate the natural transcriptional promoter of HIV-1. Previous TAR decoy constructs have used HIV-1 TAR. However, recent epidemiological and biological data began to suggest that the TAR region from the human immunodeficiency virus type 2 (HIV-2) may suppress HIV-1 transcription and hence replication. We created a vector which overexpresses TAR-2 under the control of the human U6 small nuclear RNA gene promoter and here show that the U6-TAR-2 decoy construct potently inhibits both HIV-2 and HIV-1 gene expression. Further, this decoy construct is able to markedly suppress HIV-1 replication. Thus, we have directly proven that TAR-2 can suppress HIV-1 replication and suggest that the HIV-2 TAR decoy may prove useful for combating HIV-1 infection.

Rapid assay for simultaneous detection and differentiation of immunoglobulin G antibodies to human immunodeficiency virus type 1 (HIV-1) group M, HIV-1 group O, and HIV-2

A rapid immunodiagnostic test that detects and discriminates human immunodeficiency virus (HIV) infections on the basis of viral type, HIV type 1 (HIV-1) group M, HIV-1 group O, or HIV-2, was developed. The rapid assay for the detection of HIV (HIV rapid assay) was designed as an instrument-free chromatographic immunoassay that detects immunoglobulin G (IgG) antibodies to HIV. To assess the performance of the HIV rapid assay, 470 HIV-positive plasma samples were tested by PCR and/or Western blotting to confirm the genotype of the infecting virus. These samples were infected with strains that represented a wide variety of HIV strains including HIV-1 group M (subtypes A through G), HIV-1 group O, and HIV-2 (subtypes A and B). The results showed that the HIV genotype identity established by the rapid assay reliably (469 of 470 samples) correlates with the HIV genotype identity established by PCR or Western blotting. A total of 879 plasma samples were tested for IgG to HIV by a licensed enzyme immunoassay (EIA) (470 HIV-positive samples and 409 HIV-negative samples). When they were tested by the rapid assay, 469 samples were positive and 410 were negative (99.88% agreement). Twelve seroconversion panels were tested by both the rapid assay and a licensed EIA. For nine panels identical results were obtained by the two assays. For the remaining three panels, the rapid assay was positive one bleed later in comparison to the bleed at which the EIA was positive. One hundred three urine samples, including 93 urine samples from HIV-seropositive individuals and 10 urine samples from seronegative individuals, were tested by the rapid assay. Ninety-one of the ninety-three urine samples from HIV-seropositive individuals were found to be positive by the rapid assay. There were no false-positive results (98.05% agreement). Virus in all urine samples tested were typed as HIV-1 group M. These results suggest that a rapid assay based on the detection of IgG specific for selected transmembrane HIV antigens provides a simple and reliable test that is capable of distinguishing HIV infections on the basis of viral type.

Genetically divergent strains of human immunodeficiency virus type 2 use multiple coreceptors for viral entry

Several members of the seven-transmembrane chemokine receptor family have been shown to serve, with CD4, as coreceptors for entry by human immunodeficiency virus type 1 (HIV-1). While coreceptor usage by HIV-1 primary isolates has been studied by several groups, there is only limited information available concerning coreceptor usage by primary HIV-2 isolates. In this study, we have analyzed coreceptor usage of 15 primary HIV-2 isolates, using lymphocytes from a donor with nonfunctional CCR5 (CCR5 -/-; homozygous 32-bp deletion). Based on the infections of PBMCs, seven of these primary isolates had an absolute requirement for CCR5 expression, whereas the remaining eight exhibited a broader coreceptor usage. All CCR5-requiring isolates were non-syncytium inducing, whereas isolates utilizing multiple coreceptors were syncytium inducing. Blocking experiments using known ligands for chemokine receptors provided indirect evidence for additional coreceptor utilization by primary HIV-2 isolates. Analysis of GHOST4 cell lines expressing various chemokine receptors (CCR1, CCR2b, CCR3, CCR4, CCR5, CXCR4, BONZO, and BOB) further defined specific coreceptor usage of primary HIV-2 isolates. The receptors used included CXCR4, CCR1-5, and the recently described receptors BONZO and BOB. However, the efficiency at which the coreceptors were utilized varied greatly among the various isolates. Analysis of V3 envelope sequences revealed no specific motif that correlated with coreceptor usage. Our data demonstrate that primary HIV-2 isolates are capable of using a broad range of coreceptors for productive infection in vitro. Additionally, our data suggest that expanded coreceptor usage by HIV-2 may correlate with disease progression.

Antigenicity of linear and cyclic peptides mimicking the disulfide loops in HIV-2 envelope glycoprotein: synthesis, reoxidation and purification

The external envelope glycoprotein (gp125) of human immunodeficiency virus type 2 (HIV-2) contains 22 cysteine residues. The positions of the 11 disulfide bridges in HIV-2 gp125 were determined by analogy with the experimental position of the disulfide bonds found in the gp120 of HIV-1. Peptides expected to mimic all 11 disulfide-bonded domains containing from 13 to 47 amino acids were synthesized by the solid-phase method according to 9-fluorenylmethoxycarbonyl strategy, except for peptide 5, which was assembled according to t-butoxycarbonyl (Boc) strategy. Analysis of all the crude peptides showed that the expected peptides were obtained with good yields, between 75% and 85%. Peptides were purified further by high-performance liquid chromatography (HPLC) on an Aquapore RPC30 C8 column. Peptide homogeneity was more than 90%. For each peptide, linear peptides (L) were SH-iodoacetamidated, whereas cyclization of peptides (C) was performed by air oxidation. Oxidation kinetics was followed with the Ellman test and HPLC. Cyclic peptides were purified by HPLC and characterized by fast atom bombardment mass spectrometry. This analysis showed that a small quantity (<10%) of dimeric peptides (2 and 8) and cyclic peptides containing oxidized methionine or tryptophan residues (4, 9 and 10) were formed. To assess the relevance of conformation for the antigenicity of disulfide-bonded loops of HIV-2 gp125, the antigenicity of linear and cyclic peptides was tested against a set of 76 HIV-2 positive human sera by enzyme-linked immunosorbent assay. Peptides 2, 4 and 9, mimicking the V1, V2 and V3 regions of the external envelope glycoprotein (gp 125) of HIV-2, were the most highly reactive with HIV-2 positive human sera tested at the dilution of 1:50. Cyclic peptides generally were recognized more than linear peptides, as shown by their greater inhibition (2 to 10 times more) of antigen-antibody complexes. Structure-antigenicity of peptide V3, the most reactive peptide (75% of the HIV-2 positive sera tested), was analyzed further. Cyclic peptide 9C had a higher affinity for anti-gp125 antibodies than linear peptide 9L. In addition, circular dichroism showed that linear and cyclic peptides 9 had a similar structure, but when analyzed in aqueous solution or in trifluoroethanol (TFE), the structural difference shown with antibodies was not confirmed. No significant difference was observed between the antigenicity of linear and cyclic peptides 1, 8 and 11, mimicking the C1, C2 and C4 regions of HIV-1 gp125. These peptides were weakly reactive with HIV-2 positive sera. This result agrees with the low immunogenicity of conserved regions.

An HIV type 2 DNA vaccine induces cross-reactive immune responses against HIV type 2 and SIV

We have previously reported on the generation of specific functional immune responses after inoculation of animals with expression vectors encoding HIV-1 genes. This article provides the details of the first application of this new technology to induce immune responses against HIV-2. This virus is molecularly and serologically distinct from HIV-1 and is in fact more closely related to the simian immunodeficiency virus (SIV). Anti-HIV-2 and SIV antibodies were induced in mice of three different haplotypes following a single intramuscular inoculation with an HIV-2/ROD envelope glycoprotein expression vector (pcEnv-2). Boosting of animals with pcEnv-2 induced both anti-HIV-2 neutralizing antibodies and T cell-proliferative responses against HIV-2 and SIVmac proteins. We compared the humoral and cellular immune responses of mice injected with pcEnv-2 and then boosted with either the homologous DNA construct or a recombinant Env protein. Animals boosted with pcEnv-2 generated B and T cell immune responses as strong as those of mice boosted with recombinant gp140 protein in adjuvant. Finally, cellular immune responses were significantly increased with the coadministration of pcEnv-2 and a plasmid expressing interleukin 12. We therefore conclude that DNA plasmid inoculation induces cross-reactive anti-HIV-2 and anti-SIVmac immune responses in mice. This technology should be further investigated as a potential vaccine component for this human pathogen.

Linear and cyclic peptides mimicking the disulfide loops in HIV-2 envelope glycoprotein induced antibodies with different specificity

The aim of this study was to compare the immunogenicity and antigenicity of cyclic and linear peptides that mimic the disulfide loops in HIV-2ROD gp125. Based on the hypothetical assignment of intrachain disulfide bonds in HIV-2 envelope glycoprotein, peptides expected to mimic all 11 disulfide-bonded domains were synthesized, oxidized or cysteine-alkylated; they were then purified and characterized. Rabbits were immunized with either linear cysteine-alkylated peptides (L1-L11) or cyclic oxidized peptides (C1-C11). All peptides except 7L elicited antibodies with titers between 10(3) and 5 x 10(6). Anti-peptide C (2, 3, 4, 7, 8, 9, 11) and anti-peptide L (2, 3, 8, 9, 11) antibodies recognized the native HIV-2 gp 125. Moreover, we found that cyclization of the peptides significantly increased the level of anti-peptide antibodies reacting with the intact antigen protein. Deglycosylation increased the level of protein reactivity of anti-peptide antibodies and rendered the epitopes in peptides 5, 6, 10 accessible, which were masked in the native protein. Peptide 1 induced antibodies reacting only with the denatured reduced gp125 HIV-2. In addition, while anti-peptide L antibodies reacted better with L peptide (called "linear" structural specificity), anti-peptide C antibodies reacted similarly with L and C peptides (called "broad" structural specificity). Interestingly, the "broad" structural specificity of antibodies correlated with reactivity against native gp125. Although none of these anti-peptide antisera displayed neutralizing activity against HIV-2ROD, these results support the hypothesis that the structural restriction of peptides have a major influence upon the generation of more specific antibodies for recognizing the intact protein.

Usage of the coreceptors CCR-5, CCR-3, and CXCR-4 by primary and cell line-adapted human immunodeficiency virus type 2

The chemokine receptors CCR-5 and CXCR-4, and possibly CCR-3, are the principal human immunodeficiency virus type 1 (HIV-1) coreceptors, apparently interacting with HIV-1 envelope, in association with CD4. Cell lines coexpressing CD4 and these chemokine receptors were infected with a panel of seven primary HIV-2 isolates passaged in peripheral blood mononuclear cells (PBMC) and three laboratory HIV-2 strains passaged in T-cell lines. The CCR-5, CCR-3, and CXCR-4 coreceptors could all be used by HIV-2. The ability to use CXCR-4 represents a major difference between HIV-2 and the closely related simian immunodeficiency viruses. Most HIV-2 strains using CCR-5 could also use CCR-3, sometimes with similar efficiencies. As observed for HIV-1, the usage of CCR-5 or CCR-3 was observed principally for HIV-2 strains derived from asymptomatic individuals, while HIV-2 strains derived from AIDS patients used CXCR-4. However, there were several exceptions, and the patterns of coreceptor usage seemed more complex for HIV-2 than for HIV-1. The two T-tropic HIV-2 strains tested used CXCR-4 and not CCR-5, while T-tropic HIV-1 can generally use both. Moreover, among five primary HIV-2 strains all unable to use CXCR-4, three could replicate in CCR-5-negative PBMC, which has not been reported for HIV-1. These observations suggest that the CCR-5 coreceptor is less important for HIV-2 than for HIV-1 and indicate that HIV-2 can use other cell entry pathways and probably other coreceptors. One HIV-2 isolate replicating in normal or CCR-5-negative PBMC failed to infect CXCR-4+ cells or the U87MG-CD4 and sMAGI cell lines, which are permissive to infection by HIV-2 but not by HIV-1. This suggests the existence of several HIV-2-specific coreceptors, which are differentially expressed in cell lines and PBMC.

The sequence and structure of the 3' arm of the first stem-loop of the human immunodeficiency virus type 2 trans-activation responsive region mediate Tat-2 transactivation

Human immunodeficiency virus type 2 (HIV-2) causes AIDS, but generally after a much longer asymptomatic period than that which follows infection with HIV-1. At the molecular level, HIV-2 is much more closely related to the simian immunodeficiency viruses than to HIV-1 and our previous studies have demonstrated that HIV-2 and HIV-1 enhancer stimulation is mediated by different sets of cellular proteins following T-cell activation. Similar to HIV-1, HIV-2 encodes a transactivating protein, Tat, which appears to be necessary for viral replication and stimulates viral transcriptional initiation and/or elongation. While Tat-1 binds to the RNA of the trans-activation responsive (TAR) region of HIV-1 and HIV-2, cellular factors that bind to the RNA transcript are also necessary for Tat to function in vivo. Since almost all previous investigations of cellular cofactors for Tat had focused on HIV-1, we undertook studies aimed at understanding the interaction between the TAR RNA region of the HIV-2 promoter (TAR-2) and cellular proteins. By using extension inhibition analysis (toeprinting) and RNA electrophoretic mobility shift assays, we demonstrated binding of a nuclear factor(s) in T cells to the base of the promoter-proximal stem-loop structure. Mutational analysis of this region revealed that both the sequence of the 3' arm and the stem structure itself are important for activation of the promoter by Tat-2. In contrast, the structure is necessary for activation of TAR-2 by Tat-1 but the sequence is less important. These results suggest that a cellular factor interacts with the 3' arm of the proximal stem-loop structure of TAR-2 and mediates Tat-2-induced increases in the level of HIV-2 transcripts.

Detection of human immunodeficiency virus type 1 and type 2 in the female genital tract: implications for the understanding of virus transmission

Risk of perinatal or female to male sexual transmission of HIV is likely to be associated with whether, and at what concentration, the virus is present in the cervical and vaginal secretions of the HIV-infected woman. Examining correlates of cervical and vaginal HIV shedding is, therefore, essential for the development of strategies to interrupt HIV transmission. This article presents the rationale for using detection of HIV in the female genital tract as a marker of infectivity, and briefly describes methods for detecting HIV-1 and HIV-2 in cervical or vaginal fluids. Findings from studies incorporating the measurement of HIV in the female genital tract are reviewed, placing particular emphasis on issues relevant to epidemiological studies of HIV transmission.

DEK, an autoantigen involved in a chromosomal translocation in acute myelogenous leukemia, binds to the HIV-2 enhancer

The product of the dek oncogene is the 43-kDa DEK nuclear protein. DEK was first identified in a fusion with the CAN nucleoporin protein in a specific subtype of acute myelogenous leukemia. DEK has also been shown to be an autoantigen in patients with pauciarticular onset juvenile rheumatoid arthritis. Further, the last 65 amino acids of DEK can partially reverse the mutation-prone phenotype of cells from patients with ataxia-telangiectasia. However, in spite of these significant disease associations, the function of DEK has remained unclear. The HIV-2 peri-ets (pets) site is a TG-rich element found between the two Elf-1 binding sites in the HIV-2 enhancer. The pets element mediates transcriptional activation whether the enhancer is stimulated by phorbol 12-myristate 13-acetate (PMA) alone, phytohemagluttinin (PHA) alone, PMA plus PHA, soluble antibodies to the T cell receptor, immobilized antibodies to the T cell receptor, or by antigen. Previously, we purified and characterized the pets factor, demonstrating that it is a 43-kDa nuclear protein. We now describe the identification of DEK as this 43-kDa pets factor. Using a modified Southwestern screening procedure, we find that DEK can recognize the pets element. We demonstrate the ability of recombinant DEK to bind specifically to the pets site using the electrophoretic mobility shift assay (EMSA) and DNase I footprinting. "Supershift" EMSA further confirms that DEK is the dominant protein binding to the pets site in T cell extracts. Our findings show that DEK is a site-specific DNA binding protein that is likely involved in transcriptional regulation and signal transduction. This has implications for multiple pathogenic processes, including hematologic malignancies, arthritis, ataxia-telangiectasia, and AIDS caused by HIV-2.

Purification of the pets factor. A nuclear protein that binds to the inducible TG-rich element of the human immunodeficiency virus type 2 enhancer

The peri-ets (pets) site is a TG-rich element found immediately adjacent to two binding sites for the ets family member Elf-1 in the human immunodeficiency virus type 2 (HIV-2) enhancer. Enhancer activation in response to T cell stimulation by phorbol myristate acetate, phytohemagglutinin, soluble or cross-linked antibodies to the T cell receptor, or antigen is mediated through this site in conjunction with its two adjacent Elf-1 binding sites, PuB1 and PuB2, and a kappaB site. Site-specific mutation of the pets element significantly reduces inducible activation of this enhancer but does not affect its transactivation by HIV-2 tat or other viral transactivators. Similar TG-rich sequences adjacent to ets-binding sites have also been found to be functionally important in the human T-cell leukemia virus type I and murine Moloney leukemia virus enhancers. As the cellular factor binding to the pets site plays a significant role in regulating the HIV-2 enhancer in both T cells and monocytes, we have purified this protein from bovine spleens and demonstrate that it is 43 kDa in size. In addition, using glycerol gradient centrifugation, Southwestern blotting, electrophoretic mobility shift assays employing purified protein eluted from a gel, and a new in solution UV cross-linking competitive assay, we show that the dominant protein binding to the pets site is 43 kDa in size. These results indicate that a nuclear protein of 43 kDa binds specifically to the pets site of the HIV-2 enhancer and may mediate transcriptional activation of this important human pathogen in response to T cell stimulation. As retroviruses generally expropriate important human regulatory proteins for their own use, the 43-kDa pets factor is also likely to play a significant role in signal transduction in T cells and in other cellular processes.

Epidemiology of HIV-2 infection in Spain. The HIV-2 Spanish Study Group

Human immunodeficiency virus type 2 (HIV-2) infection is endemic in West Africa, where it is responsible for many cases of AIDS. HIV-2-infected subjects have been described in other countries, mainly African immigrants, although infection in native individuals has been reported as well. The first cases of HIV-2 infection in Spain were identified in 1988. Through December 1995, 56 HIV-2 infected individuals have been diagnosed, primarily in large urban areas (23 cases in Madrid and 18 in Barcelona). All are African immigrants, except for 12 natives (21.4%), six of whom acquired the infection in endemic areas; the remaining six (2 women with numerous sexual partners and 4 homo/bisexual men) acquired the infection in Spain. Heterosexual transmission was probable in all but seven cases: five homo/bisexual males, a subject who likely acquired infection through parenteral exposure, and a child born to an HIV-2-infected mother. Nine patients (all Spanish born) have developed AIDS (16%), six of whom have died. In conclusion, HIV-2 infection is present in Spain at a low rate, and there is little evidence supporting an emerging ongoing transmission outside the population of African immigrants.

False negative anti-HIV-1/HIV-2 ELISAs in acute HIV-2 infection

Since HIV-2 was isolated in 1986, only 1 case of acute HIV-2 infection has been reported. We have identified another patient with primary HIV-2 infection. Follow-up samples were requested from the patient due to discrepant results. The HIV-2 infection was confirmed with HIV-2-specific proviral DNA amplification by PCR. The HIV-2 seroconversion panel obtained was used to evaluate the sensitivity of both combined and specific ELISAs currently in use in Europe, and to investigate the Western-blot patterns on both HIV-1-and HIV-2-specific Western blots. The window period was determined to be less than 37 days with the most sensitive assays. A remarkable difference in sensitivity to HIV-2 antibodies in acute HIV-2 infection was found in combined HIV-1/HIV-2 ELISAs. Three out of the 4 combined sandwich ELISAs appeared to be less sensitive than the indirect ELISAs in HIV-2 seroconversion, leading to a prolonged window period. One HIV-2-specific ELISA was also negative on the first sample, but positive on the second sample. In the HIV-2 Western blot, early reaction with HIV-2-specific env and gag proteins was seen, whereas the HIV-1 Western blot on the first sample revealed gag (p24, p55) reactivity only.

The envelope glycoprotein of human immunodeficiency virus type 2 enhances viral particle release: a Vpu-like factor?

The Vpu protein is a human immunodeficiency virus type 1 (HIV-1)-specific accessory protein that is required for the efficient release of viral particles from infected cells. Even though HIV-2 does not encode Vpu, we found that this virus is nevertheless capable of efficiently releasing virus particles. In fact, the rate of virus release from HeLa cells transfected with a full-length molecular clone of HIV-2, ROD10, was comparable to that observed for the vpu+ HIV-1 NL4-3 isolate and was not further enhanced by expression of Vpu in trans. However, consistent with previous observations showing that HIV-2 particle release is Vpu responsive in the context of HIV-1/HIV-2 chimeric constructs; exchanging the gag-pol region of NL4-3 with the corresponding region from pROD10 rendered the resulting chimeric virus Vpu responsive. Our finding that the responsiveness of HIV-2 particle release to Vpu is context dependent suggested the presence of a Vpu-like factor(s) encoded by HIV-2. Using chimeric proviruses encoding HIV-2 gag and pol in the context of the HIV-1 provirus that were coexpressed with subgenomic HIV-2 constructs, we found that the HIV-2 envelope glycoprotein had the ability to enhance HIV-2 particle release with an efficiency comparable to that of the HIV-1 Vpu protein. Conversely, inactivation of the HIV-2 env gene in the original ROD10 clone resulted in a decrease in the rate of viral particle release to a level that was comparable to that of Vpu-deficient HIV-1 isolates. Providing the wild-type envelope in trans rescued the particle release defect of the ROD10 envelope mutant. Thus, unlike HIV-1, which encodes two separate proteins to regulate virus release or to mediate viral entry, the HIV-2 Env protein has evolved to perform both functions.

T-helper reactivity to simian immunodeficiency virus gag synthetic peptides in human immunodeficiency virus type 2 infected individuals

West African populations are infected with divergent strains of human immunodeficiency virus type 2 (HIV2), some of which are closely related to simian immunodeficiency virus (SIV) and it has been postulated that the HIV2 epidemic might have arisen by cross-species spread of SIV into the human population in West Africa. To gain some insight into the possible basis for cross protection between these two closely related viruses, the T-helper responses to 15 synthetic peptides from SIV gag synthetic peptides were investigated in seven HIV2-infected subjects and in seven healthy controls. Significant reactivity to at least one of the synthetic peptides tested was found in all patients and a statistically significant correlation between CD4+ lymphocyte absolute numbers and the number of reacting peptides was observed. A marginal lymphocyte reactivity was found in two of the healthy controls studied. In conclusion, this preliminary evidence that HIV2-infected patients exhibit T-cell responses to SIV gag peptides suggests that both viruses share t-helper epitopes in the gag viral region and raises the possibility of cross protection between SIV and HIV2 which may be relevant for HIV2 vaccine research based on closely related retroviruses.

HIV-2 infection with a long asymptomatic period

We give details of a patient infected with HIV-2 which had what we believe to be the longest asymptomatic period so far reported. The infection was probably acquired though a blood transfusion in Africa 27 years ago. At present the patient remains asymptomatic and her cellular defence mechanisms, evaluated by CD+4 lymphocyte counts and hypersensitivity skin tests, are not severely compromised. HIV-2 has come distinct epidemiological, clinical and biological features which are different from the related HIV-1 and deserve investigation in order for its natural history to be better understood.

The peri-kappa B site mediates human immunodeficiency virus type 2 enhancer activation in monocytes but not in T cells

Human immunodeficiency virus type 2 (HIV-2), like HIV-1, causes AIDS and is associated with AIDS cases primarily in West Africa. HIV-1 and HIV-2 display significant differences in nucleic acid sequence and in the natural history of clinical disease. Consistent with these differences, we have previously demonstrated that the enhancer/promoter region of HIV-2 functions quite differently from that of HIV-1. Whereas activation of the HIV-1 enhancer following T-cell stimulation is mediated largely through binding of the transcription factor NF-kappa B to two adjacent kappa B sites in the HIV-1 long terminal repeat, activation of the HIV-2 enhancer in monocytes and T cells is dependent on four cis-acting elements: a single kappa B site, two purine-rich binding sites, PuB1 and PuB2, and a pets site. We have now identified a novel cis-acting element within the HIV-2 enhancer, immediately upstream of the kappa B site, designated peri-kappa B. This site is conserved among isolates of HIV-2 and the closely related simian immunodeficiency virus, and transfection assays show this site to mediate HIV-2 enhancer activation following stimulation of monocytic but not T-cell lines. This is the first description of an HIV-2 enhancer element which displays such monocyte specificity, and no comparable enhancer element has been clearly defined for HIV-1. While a nuclear factor(s) from both peripheral blood monocytes and T cells binds the peri-kappa B site, electrophoretic mobility shift assays suggest that either a different protein binds to this site in monocytes versus T cells or that the protein recognizing this enhancer element undergoes differential modification in monocytes and T cells, thus supporting the transfection data. Further, while specific constitutive binding to the peri-kappa B site is seen in monocytes, stimulation with phorbol esters induces additional, specific binding. Understanding the monocyte-specific function of the peri-kappa B factor may ultimately provide insight into the different role monocytes and T cells play in HIV pathogenesis.

Differentiation of human immunodeficiency virus type 1 (HIV-1) infections with HIV-2-cross-reacting antibody from mixed infections with HIV-1 and HIV-2 by serological absorption test

The interpretation of dual seroreactivity with human immunodeficiency virus type 1 (HIV-1) and HIV-2 in blood samples is a serious problem facing AIDS researchers worldwide. Some samples of sera from HIV-1-infected patients showed a serological cross-reaction with HIV-2, causing confusion regarding the serodiagnosis. Therefore, we tried to differentiate these serum samples from those containing real mixed infections with both types of virus. Sera from patients with HIV-1 infections with HIV-2 cross-reacting antibody in Japan were distinguished from sera from patients with mixed infections with HIV-1 and HIV-2 in West Africa by our serological cross-absorption test, which proved to be highly specific and useful for serodiagnosis.

HIV-specific cytotoxic T-cells in HIV-exposed but uninfected Gambian women

A crucial requirement in the rational design of a prophylactic vaccine against the human immunodeficiency virus (HIV) is to establish whether or not protective immunity can occur following natural infection. The immune response to HIV infection is characterized by very vigorous HIV-specific cytotoxic T-lymphocyte (CTL) activity. We have identified four HIV-1 and HIV-2 cross-reactive peptide epitopes, presented to CTL from HIV-infected Gambians by HLA-B35 (the most common Gambian class I HLA molecule). These peptides were used to elicit HIV-specific CTLs from three out of six repeatedly exposed but HIV-seronegative female prostitutes with HLA-B35. These women remain seronegative with no evidence of HIV infection by polymerase chain reaction or viral culture. Their CTL activity may represent protective immunity against HIV infection.

Genetic diversity of human immunodeficiency virus type 2: evidence for distinct sequence subtypes with differences in virus biology

The virulence properties of human immunodeficiency virus type 2 (HIV-2) are known to vary significantly and to range from relative attenuation in certain individuals to high-level pathogenicity in others. These differences in clinical manifestations may, at least in part, be determined by genetic differences among infecting virus strains. Evaluation of the full spectrum of HIV-2 genetic diversity is thus a necessary first step towards understanding its molecular epidemiology, natural history of infection, and biological diversity. In this study, we have used nested PCR techniques to amplify viral sequences from the DNA of uncultured peripheral blood mononuclear cells from 12 patients with HIV-2 seroreactivity. Sequence analysis of four nonoverlapping genomic regions allowed a comprehensive analysis of HIV-2 phylogeny. The results revealed (i) the existence of five distinct and roughly equidistant evolutionary lineages of HIV-2 which, by analogy with HIV-1, have been termed sequence subtypes A to E; (ii) evidence for a mosaic HIV-2 genome, indicating that coinfection with genetically divergent strains and recombination can occur in HIV-2-infected individuals; and (iii) evidence supporting the conclusion that some of the HIV-2 subtypes may have arisen from independent introductions of genetically diverse sooty mangabey viruses into the human population. Importantly, only a subset of HIV-2 strains replicated in culture: all subtype A viruses grew to high titers, but attempts to isolate representatives of subtypes C, D, and E, as well as the majority of subtype B viruses, remained unsuccessful. Infection with all five viral subtypes was detectable by commercially available serological (Western immunoblot) assays, despite intersubtype sequence differences of up to 25% in the gag, pol, and env regions. These results indicate that the genetic and biological diversity of HIV-2 is far greater than previously appreciated and suggest that there may be subtype-specific differences in virus biology. Systematic natural history studies are needed to determine whether this heterogeneity has clinical relevance and whether the various HIV-2 subtypes differ in their in vivo pathogenicity.

Analysis of lymphocyte cell death and apoptosis in HIV-2-infected patients

Recent evidence suggests that T cell apoptosis could be involved in the pathogenesis of HIV-1 infection. As the progression of HIV-2 associated disease appears to be slower than that of HIV-1, we investigated whether there were differences in the degree of T cell death and apoptosis in peripheral blood mononuclear cell (PBMC) cultures from patients with HIV-1 or HIV-2 infection. PBMC from healthy controls (n = 28) and patients infected with HIV-1 (n = 26: asymptomatic (ASY)/persistent generalized lymphadenopathy (PGL), n = 16; and AIDS-related complex (ARC)/AIDS n = 10) or HIV-2 (n = 30: ASY/PGL, n = 16; ARC/AIDS, n = 14) were cultured in the absence or presence of mitogens (PHA, PWM) or superantigen (SEB). After 48 h, cell death (CD) was assessed by trypan blue exclusion and in some patients programmed cell death (PCD) was quantified in flow cytometry by measuring the percentage of hypodiploid nuclei corresponding to fragmented DNA, after treating the cells with a propidium iodide hypotonic solution. HIV-1 and HIV-2 ARC/AIDS patients and ASY/PGL HIV-1+ patients had significant increases in cell death percentages compared with controls, both in unstimulated and stimulated lymphocyte cultures. However, HIV-2+ ASY/PGL patients did not exhibit significant increases of cell death in unstimulated cultures. In addition, the comparison between HIV-1 and HIV-2 infected subjects in similar stages of disease, showed no significant differences in CD in the ARC/AIDS patients, although ASY/PGL HIV-2 infected subjects had lower levels of CD than the HIV-1+ ASY/PGL (3.4% +/- 0.6 s.e.m. versus 6.8% +/- 1.1 s.e.m., P < 0.01). PCD was significantly increased both in ASY/PGL (14.3% +/- 2.2 s.e.m., n = 8, P < 0.005) and in ARC/AIDS (25.3% +/- 4.5 s.e.m., n = 9, P < 0.001) HIV-1+ patients compared with healthy controls (5.8% +/- 1.7 s.e.m., n = 11). This contrasts with HIV-2 infected subjects where the ASY/PGL patients (10.0% +/- 2.8 s.e.m., n = 6) did not differ significantly from healthy controls, although ARC/AIDS patients (27.2% +/- 4.2 s.e.m., n = 9, P < 0.001) had significantly increased levels of PCD. In conclusion, this is the first report describing the occurrence of spontaneous and activation-induced lymphocyte death by apoptosis in HIV-1 infected subjects.(ABSTRACT TRUNCATED AT 400 WORDS)

Population migration and the spread of types 1 and 2 human immunodeficiency viruses

Over 14 million people are estimated to be infected with the human immunodeficiency viruses (HIV), with nearly three-fourths of the infected persons residing in developing countries. One factor responsible for dissemination of both HIV-1 and HIV-2 worldwide was the intense migration of individuals, from rural to urban centers with subsequent return migration and internationally due to civil wars, tourism, business purposes, and the drug trade. In sub-Saharan Africa, between 1960 and 1980, urban centers with more than 500,000 inhabitants increased from 3 to 28, and more than 75 military coups occurred in 30 countries. The result was a massive migration of rural inhabitants to urban centers concomitant with the spread of HIV-1 to large population centers. With the associated demographic, economic, and social changes, an epidemic of sexually transmitted diseases and HIV-1 was ignited. Migratory patterns were also responsible for the spread of endemic HIV-2 to neighboring West African countries and eventually to Europe, the Americans, and India. Although Southeast Asia was the last region in which HIV-1 was introduced, it has the greatest potential for rapid spread due to population density and inherent risk behaviors. Thus, the migration of poor, rural, and young sexually active individuals to urban centers coupled with large international movements of HIV-infected individuals played a prominent role in the dissemination of HIV globally. The economic recession has aggravated the transmission of HIV by directly increasing the population at risk through increased urban migration, disruption of rural families and cultural values, poverty, and prostitution and indirectly through a decrease in health care provision. Consequently, social and economic reform as well as sexual behavior education need to be intensified if HIV transmission is to be controlled.

Quo vadis: perinatal AIDS issues--2004

The HIV problem will inexorably increase over the next decade, with an increasing proportionate impact upon women and children over the next decade. HIV will become endemic, essentially worldwide. Some regions in the developed world may be relatively spared if current trends continue. This may reduce the willingness to expend necessary resources, particularly if trends toward increasing isolationism continue. There are already signs of a world becoming "bored" with AIDS and the chronicity of a difficult problem. This engenders an atmosphere ripe for increasing discrimination, with the development of loopholes in protective legislation. Already in the United States, some lawsuits concerning health care access among employees have been decided in the employer's favor, permitting them to restrict access to health insurance, despite other regulations which might have protected such workers. Similarly, some HIV-infected health care workers have been dismissed or lost their privileges in the 1990s, despite passage of the Americans with Disabilities Act as well as preceding legislation. It remains to be seen how society will cope with these complicated issues. The view of AIDS in 2004 presented above is pessimistic. There are some important rays of hope. Recent innovative vaccine work and new theoretical models may put us on the road to success, both with preventive and therapeutic vaccines. In particular, the first success in eliciting protection against vaginal HIV exposure, albeit partial, was reported in mid 1993. In a simian immunodeficiency virus (SIV) in vivo experimental model, cellular immunity to SIV was induced in macaques without their developing any signs of SIV infection. These macaques after rechallenge with low-dose SIV remained free of detectable SIV, so there may be an element of protection associated with specific cellular immune responses to immunodeficiency viruses. However, very high-dose SIV rechallenge experiments in similar macaques still led to acquisition of active SIV infection, suggesting that any such protection was only partial. It is also possible that cellular immune protection may be of varying efficacy against different types of exposure, particularly parenteral versus mucosal (such as sexual) exposures. There is also reason for specific optimism concerning interventions that might directly reduce the risk of perinatal transmission. Data from studies of twins suggest that a substantial proportion of perinatal transmission does not occur until after labor has commenced. Thus, caesarian sections may potentially reduce the risk of transmission to the fetus in some cases.(ABSTRACT TRUNCATED AT 400 WORDS)