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Summary Passive administration of HIV neutralizing antibodies (nAbs) can protect macaques from hard-to-neutralize (tier 2) chimeric simian-human immunodeficiency virus (SHIV) challenge. However, conditions for nAb-mediated protection after vaccination have not been established. Here, we selected groups of 6 rhesus macaques with either high or low serum nAb titers from a total of 78 animals immunized with recombinant native-like (SOSIP) Env trimers. Repeat intrarectal challenge with homologous tier 2 SHIVBG505 led to rapid infection in unimmunized and low-titer animals. High-titer animals, however, demonstrated protection that was gradually lost as nAb titers waned over time. An autologous serum ID50 nAb titer of ∼1:500 afforded more than 90% protection from medium-dose SHIV infection. In contrast, antibody-dependent cellular cytotoxicity and T cell activity did not correlate with protection. Therefore, Env protein-based vaccination strategies can protect against hard-to-neutralize SHIV challenge in rhesus macaques by inducing tier 2 nAbs, provided appropriate neutralizing titers can be reached and maintained., Graphical Abstract, Highlights • HIV Env trimer immunization protects from autologous tier 2 challenge in macaques • Neutralizing antibody (nAb) titers correlate with protection and peak viremia • T cell and ADCC functions do not correlate with protection • nAb titers of ∼1:500 (pseudovirus)/∼1:30 (live virus) required for ∼90% protection, Vaccine-induced immunity to HIV is a major research focus, but relevant correlates of protection remain controversial. Here, Pauthner et al. study protection from hard-to-neutralize SHIVBG505 challenge after immunization with native-like BG505 Envelope trimers in nonhuman primates and identify neutralizing antibodies, but not T cell or ADCC activity, as correlates of protection.

We have investigated the immunogenicity in rabbits of native-like, soluble, recombinant SOSIP.664 trimers based on the env genes of four isolates of human immunodeficiency virus type 1 (HIV-1); specifically BG505 (clade A), B41 (clade B), CZA97 (clade C) and DU422 (clade C). The various trimers were delivered either simultaneously (as a mixture of clade A + B trimers) or sequentially over a 73-week period. Autologous, Tier-2 neutralizing antibody (NAb) responses were generated to the clade A and clade B trimers in the bivalent mixture. When delivered as boosting immunogens to rabbits immunized with the clade A and/or clade B trimers, the clade C trimers also generated autologous Tier-2 NAb responses, the CZA97 trimers doing so more strongly and consistently than the DU422 trimers. The clade C trimers also cross-boosted the pre-existing NAb responses to clade A and B trimers. We observed heterologous Tier-2 NAb responses albeit inconsistently, and with limited overall breath. However, cross-neutralization of the clade A BG505.T332N virus was consistently observed in rabbits immunized only with clade B trimers and then boosted with clade C trimers. The autologous NAbs induced by the BG505, B41 and CZA97 trimers predominantly recognized specific holes in the glycan shields of the cognate virus. The shared location of some of these holes may account for the observed cross-boosting effects and the heterologous neutralization of the BG505.T332N virus. These findings will guide the design of further experiments to determine whether and how multiple Env trimers can together induce more broadly neutralizing antibody responses., Author Summary Native-like SOSIP trimers are a platform for development of immunogens aimed at inducing broadly neutralizing antibodies and, hence, a possible vaccine against HIV-1 infection. No previous study has reported on immune responses to more than one such trimer. Here, we assess how rabbits respond to immunization with two or three different trimers, based on virus sequences from HIV-1 clades A, B and C, to gain insights into whether each is immunogenic under various regimens. We find that autologous Tier-2 neutralizing antibody responses can be raised against each trimer immunogen, whether they are delivered simultaneously or sequentially. We also observed some boosting of the neutralization response to the first trimer when a second trimer was administered later. Cross-reactive neutralizing antibodies were seen but only sporadically. We also found that the key immunogenic epitopes on the Env trimers involved holes in the glycan shield, which normally protects the virus from antibody binding. These various findings will guide the design of future experiments in animals and eventually in humans.

BACKGROUND: GB virus C (GBV-C) is an apathogenic virus that inhibits human immunodeficiency virus (HIV) replication in vitro. Mother-to-child transmission (MTCT) of GBV-C has been observed in multiple small studies. Our study examined the rate and correlates of MTCT of GBV-C in a large cohort of GBV-C-HIV-coinfected pregnant women in Thailand. METHODS: Maternal delivery plasma specimens from 245 GBV-C-HIV-infected women and specimens from their infants at 4 or 6 months of age were tested for GBV-C RNA. Associations with MTCT of GBV-C were examined using logistic regression. RESULTS: One hundred one (41%) of 245 infants acquired GBV-C infection. MTCT of GBV-C was independently associated with maternal antiretroviral therapy (adjusted odds ratio [AOR] 5.21 [95% confidence interval {CI} 2.12-12.81]) infant HIV infection (AOR 0.05 [95% CI 0.01-0.26]) maternal GBV-C load (8.0 log(10) copies/mL: AOR 86.77 [95% CI 15.27-481.70]; 7.0-7.9 log(10) copies/mL: AOR 45.62 [95% CI 8.41-247.51]; 5.0-6.9 log(10) copies/mL: AOR 9.07 [95% CI 1.85-44.33]: reference

Little is known about the neutralization properties of HIV-1 in India to optimally design and test vaccines. For this reason, a functional Env clone was obtained from each of ten newly acquired, heterosexually transmitted HIV-1 infections in Pune, Maharashtra. These clones formed a phylogenetically distinct genetic lineage within subtype C. As Env-pseudotyped viruses the clones were mostly resistant to IgG1b12, 2G12 and 2F5 but all were sensitive to 4E10. When compared to a large multi-subtype panel of Env-pseudotyped viruses (subtypes B, C and CRF02_AG) in neutralization assays with a multi-subtype panel of HIV-1-positive plasma samples, the Indian Envs were remarkably complex antigenically. With the exception of the Indian Envs, results of a hierarchical clustering analysis showed a strong subtype association with the patterns of neutralization susceptibility. From these patterns we were able to identify 19 neutralization cluster-associated amino acid signatures in gp120 and 14 signatures in the ectodomain and cytoplasmic tail of gp41. We conclude that newly transmitted Indian Envs are antigenically complex in spite of close genetic similarity. Delineation of neutralization-associated amino acid signatures provides a deeper understanding of the antigenic structure of HIV-1 Env.

Prolonged coinfection with GB virus C (GBV-C) has been associated with improved survival in human immunodeficiency virus (HIV)-infected adults. We investigated whether maternal or infant GBV-C infection was associated with mother-to-child transmission (MTCT) of HIV-1 infection.The study population included 1364 HIV-infected pregnant women enrolled in 3 studies of MTCT of HIV in Bangkok, Thailand (the studies were conducted from 1992-1994, 1996-1997, and 1999-2004, respectively). We tested plasma collected from pregnant women at delivery for GBV-C RNA, GBV-C antibody, and GBV-C viral genotype. If GBV-C RNA was detected in the maternal samples, the 4- or 6-month infant sample was tested for GBV-C RNA. The rates of MTCT of HIV among GBV-C-infected women and infants were compared with the rates among women and infants without GBV-C infection.The prevalence of GBV-C RNA in maternal samples was 19%. Of 245 women who were GBV-C RNA positive, 101 (41%) transmitted GBV-C to their infants. Of 101 infants who were GBV-C RNA positive, 2 (2%) were infected with HIV, compared with 162 (13%) of 1232 infants who were GBV-C RNA negative (odds ratio [OR] adjusted for study, 0.13 [95% confidence interval {CI}, 0.03-0.54]). This association remained after adjustment for maternal HIV viral load, receipt of antiretroviral prophylaxis, CD4(+) count, and other covariates. MTCT of HIV was not associated with the presence of GBV-C RNA (adjusted OR [aOR], 0.94 [95% CI, 0.62-1.42]) or GBV-C antibody (aOR, 0.90 [95% CI, 0.54-1.50]) in maternal samples.Reduced MTCT of HIV was significantly associated with infant acquisition of GBV-C but not with maternal GBV-C infection. The mechanism for this association remains unknown.

Background. Transmission of human immunodeficiency virus (HIV) to the infant through breast-feeding is a major problem worldwide; however, the biological circumstances of such transmission remain unclear. Little characterization of breast milk CD4 + T lymphocytes has been done so far. Methods. We performed a detailed immunophenotypic analysis of T lymphocytes in the breast milk, compared with the blood, of HIV-uninfected (n = 9) and HIV-infected (n = 10) women receiving highly active antiretroviral therapy, by use of multiparameter flow cytometry. Descriptive statistics and nonparametric comparisons were performed using SAS software (version 9.1; SAS Institute). Results. In uninfected women, 44%-78% of breast milk CD4 + T cells expressed the C chemokine receptor 5 (CCR5), whereas 26%-73% of cells coexpressed CCR5 and CXC chemokine receptor 4 (CXCR4). In contrast, only 7%-20% of peripheral blood CD4 + T cells expressed CCR5 and 1%-20% coexpressed CCR5 and CXCR4. The level of CCR5 expression in CD4 + T cells in breast milk was higher than in blood. In HIV-infected women, the high frequency of CD4 + CCR5 + T cells in breast milk was preserved. Conclusions. A majority of CD4 + T cells in breast milk express high levels of CCR5 and CXCR4. Unlike other mucosal immune sites, in which CD4 + CCR5 + T cells are rapidly eliminated by HIV, these cells are preserved in breast milk during HIV infection.

Recently, a vaccine consisting of DNA priming followed by boosting with modified vaccinia Ankara (MVA) has provided long-term protection of rhesus macaques against a virulent challenge with a chimera of simian and human immunodeficiency viruses. Here, we report studies on the development of the DNA component for a DNA/MVA HIV vaccine for humans. Specifically, we assess the ability of a codon-optimized Gag-expressing DNA and two noncodon-optimized Gag-Pol-Env-expressing DNAs to prime the MVA booster dose. The codon-optimized DNA expressed virus-like particles (VLPs), whereas one of the noncodon-optimized DNAs expressed VLPs and the other expressed aggregates of HIV proteins. The MVA boost expressed Gag-Pol and Env and produced VLPs. Immunogenicity studies in macaques used one intramuscular prime with 600 microg of DNA and two intramuscular boosts with 1 x 10(8) pfu of MVA at weeks 8 and 30. The codon-optimized and noncodon-optimized DNAs proved similar in their ability to prime anti-Gag T cell responses. The aggregate and VLP-expressing Gag-Pol-Env DNAs also showed no significant differences in their ability to prime anti-Env Ab responses. The second MVA booster dose did not increase the peak CD4 and CD8 T cell responses, but increased anti-Env Ab titers by 40- to 90-fold. MVA-only immunizations elicited 10-100 times lower frequencies of T cells and 2-4 lower titers of anti-Env Ab than the Gag-Pol-Env DNA/MVA immunizations. Based on the breadth of the T cell response and a trend toward higher titers of anti-Env Ab, we are moving forward with human trials of the noncodon-optimized VLP-expressing DNA.

Recently, a simian/human immunodeficiency virus (SHIV) vaccine consisting of priming with a Gag-Pol-Env-expressing DNA and boosting with a Gag-Pol-Env-expressing recombinant modified vaccinia Ankara (rMVA) has successfully controlled a virulent SHIV challenge in a macaque model. In this, and the accompanying paper, we report on the construction and testing of a Gag-Pol-Env DNA/MVA vaccine for HIV-1/AIDS. The DNA vaccine, pGA2/JS2, expresses aggregates of Gag proteins and includes safety mutations that render it integration, reverse transcription, and packaging defective. The rMVA vaccine, MVA/HIV 48, is integration and reverse transcription defective and has a truncated Env to enhance expression on the plasma membrane. In a study in rhesus macaques, priming with pGA2/JS2 and boosting with MVA/HIV 48 raised high frequencies of T cells for Gag and Env and lower frequencies of T cells for PR, RT, and Tat. Stimulations with five peptide pools for Gag and seven peptide pools for Env revealed epitopes for cellular immune responses throughout Gag and Env. On average, CD4 T cells from the vaccinated animals recognized 7.1 peptide pools and CD8 T cells, 3.2 peptide pools. Both the height and the breadth of the elicited cellular response provide hope that this multiprotein DNA/MVA vaccine will successfully control clade B isolates of HIV-1, as well as contribute to the control of other clades and recombinant forms of HIV-1/AIDS.

We considered several key issues regarding the development of a DNA-based human immunodeficiency virus type 1 (HIV-1) vaccine: (1) should the candidate vaccine construct be derived from incident or prevalent HIV-1 strains; and (2) should circulating plasma virus, archived HIV-1 provirus recovered from peripheral blood mononuclear cells, or both be included? To address these questions, we collected circulating HIV-1 strains from infected individuals residing in Abidjan, Côte d'Ivoire. From a panel of 23 strains, 22 were HIV-1 subtype A in gag, 19 of which phylogenetically clustered with the recombinant HIV-1, CRF02-AG strains from West Africa. The mosaic genome of CRF02-AG was confirmed by sequencing the protease gene. A consensus gag p24 protein sequence was generated and 147 of 148 codons were identical to CRF02-AG (IbNG). Regardless of the sequence origin (RNA, provirus, incident, or prevalent), the gag p24 consensus sequences were highly representative of these distinct virologic compartments. These data suggest that the consensus sequence generated from incident and prevalent infections may provide an appropriate sequence for a DNA vaccine and is largely representative of the major circulating viral strain.

To investigate mechanisms of natural resistance to human immunodeficiency virus type 1 (HIV-1), we obtained blood samples from eight women who remained HIV-1 negative after3 years of high-risk sex work in Chiang Rai, Thailand. CD4+ T lymphocytes from these highly exposed, persistently seronegative (HEPS) women were readily infectable in vitro with HIV-1 subtypes B and E. Autologous CD8+ cell suppression of both HIV-1 subtypes was evident in HEPS infection cultures, but to an extent also observed in cultures from non-HIV-exposed individuals. Furthermore, production of beta-chemokines was not enhanced in HEPS cultures. However, HEPS cultures displayed significantly enhanced production of a soluble activity that suppressed postintegrated HIV-1 replication. This activity was the unique product of CD4+ T cell and monocyte cocultures. Therefore, although HEPS individuals are apparently susceptible to infection, the production of a postintegrated HIV-1 suppressive activity during monocyte-T cell interactions might protect against the establishment of infection by limiting viral dissemination.

GB virus C (GBV-C) is an apathogenic virus that has been shown to inhibit HIV replication. This study examined the prevalence and correlates of GBV-C infection and clearance in three cohorts of pregnant women in Thailand. The study population consisted of 1,719 (1,387 HIV-infected and 332 HIV-uninfected) women from three Bangkok perinatal HIV transmission studies. Stored blood was tested for GBV-C RNA, GBV-C antibody, and if RNA-positive, genotype. Risk factors associated with the prevalence of GBV-C infection (defined as presence of GBV-C RNA and/or antibody) and viral clearance (defined as presence of GBV-C antibody in the absence of RNA) among women with GBV-C infection were examined using multiple logistic regression. The prevalence of GBV-C infection was 33% among HIV-infected women and 15% among HIV-uninfected women. GBV-C infection was independently associated (AOR, 95% CI) with an increasing number of lifetime sexual partners (referent-1 partner, 2 partners [1.60, 1.22-2.08], 3-10 partners [1.92, 1.39-2.67], >10 partners [2.19, 1.33-3.62]); injection drug use (5.50, 2.12-14.2); and HIV infection (3.79, 2.58-5.59). Clearance of GBV-C RNA among women with evidence of GBV-C infection was independently associated with increasing age in years (referent

The macaque model of repeated SHIV exposures is increasingly used as a preclinical tool to evaluate biomedical HIV intervention strategies. It is unclear whether multiple virus exposures induce immune responses in macaques, as documented in uninfected individuals repeatedly exposed to HIV. We here address whether repeated, rectal SHIV(SF162P3) exposures lead to systemic T cell activation in 12 rhesus macaques, and whether this is associated with increased infection resistance. Eight macaques became systemically infected after 2-7 exposures, three macaques were less susceptible (infection after 10-12 exposures), and one macaque remained uninfected after 14 exposures. PBMCs were retrospectively monitored for increases in T cell activation by analyzing the proportion of CD8(+) T cells, recently activated or proliferated T cells (markers CD38, Ki67), a marker for cytotoxicity (granzyme B), or T cell-produced plasma cytokines (IFN-gamma, RANTES, IL-2). Repeated virus exposures did not induce sustained, potent, or diverse T cell responses prior to systemic infection. Some changes occurred in the analyzed parameters during repeated virus exposures, but similar T cell activities were also observed in five SHIV-unexposed control macaques. Thus, we found no evidence that delayed infection or resistance to infection was associated with systemic, long-lasting, protective T cell responses to repeated rectal virus exposures. Our results provide further insights into the repeat exposure macaque model. We find that this model can be used for testing biomedical prevention strategies without concern of eliciting a systemic vaccination effect.

We have developed a unique physiologic model of chronic human immunodeficiency virus type 1 (HIV-1) infection, OM-10.1, clonally derived from infected HL-60 promyelocytes and harboring a single integrated provirus. Unlike other models of chronic infection, OM-10.1 cultures remain CD4+ under normal culture conditions, during which less than 10% of the cells constitutively express HIV-1 proteins. However, when treated with tumor necrosis factor alpha (TNF-alpha), OM-10.1 cultures dramatically increased (greater than 35-fold) HIV-1 expression and rapidly down-modulated surface CD4, as greater than 95% of the cells became HIV-1+. The complete loss of surface CD4 following viral activation was neither associated with apparent cytopathicity nor due to a decline of available CD4 mRNA. There was, however, a temporal association between CD4 down-modulation and the accumulation of intracellular HIV-1 gp 160/120; in addition, intracellular CD4-gp 160 complexes were identifiable in OM-10.1 cell lysates at time points following TNF-alpha induction after surface CD4 was no longer detectable. Surface CD4 expression by OM-10.1 cells returned once viral activation ceased and could be repeatedly oscillated upon HIV-1 reactivation. Furthermore, inhibition of protein kinase activity following maximal TNF-alpha stimulation of OM-10.1 cells quickly returned activated HIV-1 to a state of latency, as evidenced by an accelerated return of surface CD4. These results with the new OM-10.1 cell line demonstrate that CD4 surface expression can be maintained during chronic infection and is critically dependent on the state of viral activation, that CD4-gp 160 intracellular complexing is involved in CD4 down-modulation, and that protein kinase pathways not only function in the primary induction of latent HIV-1 but also are required for maintaining the state of viral activation.

We examined the efficacy of tenofovir disoproxil fumarate (TDF) in blocking simian human immunodeficiency virus (SHIV) infection in Chinese rhesus macaques. Once weekly for 14 weeks or until a macaque became infected, 12 male macaques were inoculated intrarectally with amounts of SHIV(SF162P3) (10 median tissue culture infective doses; 3.8 x 10(5) virus particles) that were approximately 5-fold higher than the human immunodeficiency virus type 1 RNA levels noted in human semen during an acute infection. Of the 12 macaques, 4 received oral TDF daily, 4 received oral TDF once weekly, and 4 (control animals) received no TDF. The control animals became infected after receiving a median of 1.5 virus inoculations; macaques receiving TDF daily (1 macaque remained uninfected after 14 inoculations) and those receiving TDF weekly became infected after a median duration of 6.0 and 7.0 weeks, respectively. Although infection was delayed in treated macaques, compared with control macaques, the differences were not statistically significant (P=.315); however, the study was limited by the small numbers of animals evaluated and the variability in blood levels of TDF that resulted from oral dosing. These data demonstrate that treatment with oral TDF provided partial protection against SHIV infection but ultimately did not protect all TDF treated animals against multiple virus challenges.

Historically, HIV vaccines specifically designed to raise cellular immunity resulted in protection from disease progression but not infection when tested in monkeys challenged with a single high virus exposure. An alternative approach, more analogous to human sexual exposures, is to repetitively challenge immunized monkeys with a much lower dose of virus until systemic infection is documented. Using these conditions to mimic human sexual transmission, we found that a multi-protein DNA/MVA HIV-1 vaccine is indeed capable of protecting rhesus monkeys against systemic infection when repeatedly challenged with a highly heterologous immunodeficiency virus (SHIV). Furthermore, this repetitive challenge approach allowed us to calculate per-exposure probability of infection, an observed vaccine efficacy of 64%, and undertake a systematic analysis for correlates of protection based on exposures needed to achieve infection. Therefore, improved non-human primate models for vaccine efficacy can provide novel insight and perhaps renew expectations for positive outcomes of human HIV clinical trials.

Transmission of HIV-1 to the infant through breastfeeding is a major cause of new paediatric HIV-1 infections worldwide. Although extended breastfeeding accounts for approximately 40% of infant HIV infections worldwide, most breastfed infants remain uninfected, despite prolonged and repeated exposure to HIV-1. Mechanisms associated with transmission of HIV-1 through breastfeeding and factors related to protection from such transmission remain poorly understood. Here we focus on the cellular origin of HIV in breast milk and on immune factors within the milk that may offer protection from transmission of HIV infection. The presence of innate immunity and induction of adaptive immunity against HIV is explored: in particular, specific antibodies, cellular responses, and their significance. The role of mucosal immune activation and epithelial integrity in HIV transmission is also addressed. We are of the opinion that advances in laboratory methods that study specific aspects of immunity will help open new areas of understanding of HIV transmission through breastfeeding and mechanisms of protection, and contribute to the development of novel prevention strategies.

Resistance to HIV-1 infection despite repeated exposures has been associated with one or more HIV-specific responses, enhanced nonspecific immune modifications, and/or host genetic polymorphisms in certain individuals (highly exposed, persistently seronegative, HEPS). In the present investigation, we focused on the CCR5 gene polymorphisms and the association of such mutations to resistance to HIV-1 infection among 12 HEPS women in Chiang Rai, northern Thailand, and compared our findings with data from 10 HIV-1-infected and 9 HIV-1-uninfected unexposed women from the same geographic area. Although we have previously shown that none of the Thai women carried the Delta32 mutation, further analysis of the CCR5 coding gene region revealed that none of the women had other mutations that affect coreceptor activity (C101X or FS299) or chemokine responses (C20S, A29S, L55Q, C178R). Analysis of the CCR5 promoter region revealed that the CCR5 haplogroup C (HHC; 60%) was the predominant haplogroup among these women. Comparative analysis of the frequencies of different haplogroups among the three groups did not reveal any statistically significant differences (p0.05). However, we did find that two individuals from the HEPS group were homozygous for HHF*2 (the CCR2b- 64I bearing haplogroup) compared to none from the HIV-1-infected and -uninfected groups. There was no detectable difference in specific CCR5 haplogroups and their ability to mediate env fusion or to mediate HIV-1 infection in vitro. These data suggest that homozygosity of the HHF*2 haplogroup may be one of the factors that mediate resistance to HIV-1 infection in this cohort of HEPS women.

The medical, social, and economic impact of the human immunodeficiency virus (HIV) epidemic has underscored the need to quickly develop effective control strategies. Vigorous efforts to develop a vaccine and therapeutic agents have not yet succeeded in containing the spread of the virus. Studies of persons who remain uninfected despite extensive exposure to HIV continue to provide valuable information on mechanisms of natural protection, which can then be applied to vaccine design. Natural resistance to infection has been studied in multiple high-risk cohorts, with resistance attributed to a combination of innate, genetic, and acquired immune system-mediated mechanisms. The relative contributions of these factors to natural resistance to HIV-1 infection and possible ways in which they can be applied to vaccine design are discussed.

Objectives: To determine the impact of Plasmodium falciparum malaria coinfection and its treatment on cellular reservoirs of viral replication in HIV-1-infected persons and to relate this to changes in systemic immune activation. Methods: Plasma samples were obtained from HIV-1-infected individuals (n=10) at diagnosis of acute malaria 4 weeks after parasite clearance and from HIV-infected aparasitemic controls (n=10). Immunomagnetic HIV-1 capture analysis was used to determine the cellular origin of cell-free virus particles present in all 30 plasma samples and indices of immune activation were measured usingenzyme-linked immunosorbent assays. Results: Compared with controls the detectable proportion of HIV-1 particles derived from CD14 macrophages and CD26 lymphocytes was increased in persons with acute malaria coinfection and correlated with markedly increased plasma concentrations of both proinflammatory cytokines and soluble markers of macrophage and lymphocyte activation. Parasite clearance following treatment with antimalarial drugs resulted in decreased detection of HIV-1 particles derived from the CD14 macrophage cell subset and correlated with a marked diminution in systemic immune activation. Conclusions: Acute P. falciparum malaria coinfection impacts virus–host dynamics in HIV-1-infected persons at the cellular level notably showing a reversible induction of HIV-1 replication in CD14 macrophages that is associated with changes in immune activation. (author’s)

The granuloma plays a critical role in the host immune response to Mycobacterium tuberculosis, containing the organism and confining it in a latent state in most infected individuals. Indeed, approximately one-third of the world's population has latent M. tuberculosis infection. However, over the past decade, the human immunodeficiency virus type 1 (HIV-1) pandemic has profoundly affected the incidence and clinicopathological features of tuberculosis. This review examines the immunological mechanisms whereby HIV-1 impairs the establishment, maintenance and function of the tuberculous granuloma.

HIV-1 coreceptors CCR5 and CXCR4 play an important role in viral entry and pathogenesis. To better understand the role of viral tropism in HIV-1 transmission, we examined the coreceptor utilization of viral isolates obtained from men enrolled in a study of heterosexual transmission in northern Thailand. Viral isolates were obtained from HIV-1-positive males who had either HIV-1-infected spouses (RM; n = 5) or HIV-1-uninfected spouses (HM; n = 10). Viral isolates from 1 of the 5 RM males and 2 of the 10 HM males were CCR5 tropic, whereas isolates from 3 RM males and 6 of the HM male isolates were CXCR4 tropic. Of the nine X4-tropic isolates, seven also used at least one of the following coreceptors: CCR8, CCR1, CCR2b, or CX3CR1, and none employed CCR5 as an additional coreceptor. More importantly, three isolates, RM-15, HM-13, and HM-16 (one from a transmitter and two from nontransmitter), did not infect GHOST4.cl.34 cells expressing any of the known coreceptors. Further analysis using MAGI-plaque assays, which allow visualization of infected cells, revealed that RM-15 had low numbers of infected cells in MAGI-R5 and MAGI-X4 cultures, whereas HM-13 and HM-16 had high levels of plaques in MAGI-X4 cultures. Replication kinetics using activated lymphocytes revealed that these three isolates replicated in CCR5(+/+) as well as CCR5(-/-) peripheral blood mononuclear cells, suggesting that these isolates did not have an absolute requirement of CCR5 for viral entry. All three isolates were sensitive to the X4-antagonistic compounds T-22 and AMD3100. Analysis of the C2V3 region did not reveal any significant structural differences between any of the Thai subtype E isolates. Thus, there was no association between the pattern of coreceptor usage and transmissibility among these subtype E HIV-1 isolates.

SUMMARYThe life cycle of human immunodeficiency virus type 1 (HIV-1) is intricately related to the activation state of the host cells supporting viral replication. Although cellular activation is essential to mount an effective host immune response to invading pathogens, paradoxically the marked systemic immune activation that accompanies HIV-1 infection in vivo may play an important role in sustaining phenomenal rates of HIV-1 replication in infected persons. Moreover, by inducing CD4+cell loss by apoptosis, immune activation may further be central to the increased rate of CD4+cell turnover and eventual development of CD4+lymphocytopenia. In addition to HIV-1-induced immune activation, exogenous immune stimuli such as opportunistic infections may further impact the rate of HIV-1 replication systemically or at localized anatomical sites. Such stimuli may also lead to genotypic and phenotypic changes in the virus pool. Together, these various immunological effects on the biology of HIV-1 may potentially enhance disease progression in HIV-infected persons and may ultimately outweigh the beneficial aspects of antiviral immune responses. This may be particularly important for those living in developing countries, where there is little or no access to antiretroviral drugs and where frequent exposure to pathogenic organisms sustains a chronically heightened state of immune activation. Moreover, immune activation associated with sexually transmitted diseases, chorioamnionitis, and mastitis may have important local effects on HIV-1 replication that may increase the risk of sexual or mother-to-child transmission of HIV-1. The aim of this paper is to provide a broad review of the interrelationship between immune activation and the immunopathogenesis, transmission, progression, and treatment of HIV-1 infection in vivo.

Factors affecting HIV-1 latency present formidable obstacles for therapeutic intervention. As these obstacles have become a clinical reality, even with the use of potent anti-retroviral regimens, the need for novel therapeutic strategies specifically targeting HIV-1 latency is evident. However, therapeutic targeting of HIV-1 latency requires an understanding of the mechanisms regulating viral quiescence and activation. These mechanisms have been partially delineated using chronically infected cell models and, clearly, HIV-1 activation from latency involves several key viral and cellular components. Among these distinctive therapeutic targets, cellular factors involved in HIV-1 transcription especially warrant further consideration for rational drug design. Exploring the scientific possibilities of new therapies targeting HIV-1 latency may hold new promise of eventual HIV-1 eradication.

Human immunodeficiency virus type 1 (HIV-1) bearing HLA-DR in its envelope was detected in plasma from all patients with chronic HIV-1 infection (n= 16) and was present at higher levels in patients with active tuberculosis coinfection (n= 6). Intriguingly, however, HLA-DR was not detectable in HIV-1 from patients during primary viremia (n= 6), suggesting the possibility of virus replication in less-activated cells.

Despite numerous attempts over many years to develop an HIV vaccine based on classical strategies, none has convincingly succeeded to date. A number of approaches are being pursued in the field, including building upon possible efficacy indicated by the recent RV144 clinical trial, which combined two HIV vaccines. Here, we argue for an approach based, in part, on understanding the HIV envelope spike and its interaction with broadly neutralizing antibodies (bnAbs) at the molecular level and using this understanding to design immunogens as possible vaccines. BnAbs can protect against virus challenge in animal models, and many such antibodies have been isolated recently. We further propose that studies focused on how best to provide T cell help to B cells that produce bnAbs are crucial for optimal immunization strategies. The synthesis of rational immunogen design and immunization strategies, together with iterative improvements, offers great promise for advancing toward an HIV vaccine.

Using the OM-10.1 promyelocytic model of inducible human immunodeficiency virus type 1 (HIV-1) infection, we tested a panel of known protein kinase inhibitors for an ability to block tumour necrosis factor-α-induced HIV-1 expression. Among the compounds tested, the broad-spectrum protein kinase inhibitor H-7 uniquely blocked HIV-1 expression at the level of viral transcription, but did not inhibit nuclear factor κB activation or function. In structure—activity analysis this inhibitory activity of H-7 on HIV-1 expression corresponded with the known structural requirements for the interaction of H-7 with the ATP-binding region of protein kinase C, suggesting that it was indeed related to the kinase inhibitory properties of H-7. The mechanism of H-7 transcriptional inhibition did not involve chromatin remodelling at the HIV-1 long terminal repeat promoter, as shown by nuc-1 disruption, and appeared to involve HIV-1 RNA elongation but not initiation. Therefore, H-7 and related isoquinoline-sulphonamide analogues are most likely inhibiting a kinase target essential for HIV-1 transcriptional elongation whose identity may provide new therapeutic targets for intervention.