Detection of HIV-1 Transmission Clusters from Dried Blood Spots within a Universal Test-and-Treat Trial in East Africa

The Sustainable East Africa Research in Community Health (SEARCH) trial was a universal test-and-treat (UTT) trial in rural Uganda and Kenya, aiming to lower regional HIV-1 incidence. Here, we quantify breakthrough HIV-1 transmissions occurring during the trial from population-based, dried blood spot samples. Between 2013 and 2017, we obtained 549 gag and 488 pol HIV-1 consensus sequences from 745 participants: 469 participants infected prior to trial commencement and 276 SEARCH-incident infections. Putative transmission clusters, with a 1.5% pairwise genetic distance threshold, were inferred from maximum likelihood phylogenies; clusters arising after the start of SEARCH were identified with Bayesian time-calibrated phylogenies. Our phylodynamic approach identified nine clusters arising after the SEARCH start date: eight pairs and one triplet, representing mostly opposite-gender linked (6/9), within-community transmissions (7/9). Two clusters contained individuals with non-nucleoside reverse transcriptase inhibitor (NNRTI) resistance, both linked to intervention communities. The identification of SEARCH-incident, within-community transmissions reveals the role of unsuppressed individuals in sustaining the epidemic in both arms of a UTT trial setting. The presence of transmitted NNRTI resistance, implying treatment failure to the efavirenz-based antiretroviral therapy (ART) used during SEARCH, highlights the need to improve delivery and adherence to up-to-date ART recommendations, to halt HIV-1 transmission.

Infection with HIV-1 subtype D among acutely infected Ugandans is associated with higher median concentration of cytokines compared to subtype A

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HIV-1 subtype D exhibited significantly higher median concentrations of cytokines

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IL-12/23p40 and IL-1α were associated with faster CD4⁺T cell count decline

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bFGF was associated with maintenance of CD4+ counts above 350 cells/microliter

Objective

The observation that HIV-1 subtype D progresses faster to disease than subtype A prompted us to examine cytokine levels early after infection within the predominant viral subtypes that circulate in Uganda and address the following research questions: (1) Do cytokine levels vary between subtypes A1 and D? (2) Do cytokine profiles correlate with disease outcomes?

Methods

To address these questions, HIV-1 subtypes were determined by population sequencing of the HIV-1 pol gene and 37 plasma cytokine concentrations were evaluated using V-Plex kits on Meso Scale Discovery platform in 65 recent sero-converters.

Results

HIV-1 subtype D (pol) infections exhibited significantly higher median plasma concentrations of IL-5, IL-16, IL-1α, IL-7, IL-17A, CCL11 (Eotaxin-1), CXCL10 (IP-10), CCL13 (MCP-4) and VEGF-D compared to subtype A1 (pol) infections. We also found that IL-12/23p40 and IL-1α were associated with faster CD4⁺T cell count decline, while bFGF was associated with maintenance of CD4+ counts above 350 cells/microliter.

Conclusion

Our results suggest that increased production of cytokines in early HIV infection may trigger a disruption of the immune environment and contribute to pathogenic mechanisms underlying the accelerated disease progression seen in individuals infected with HIV-1 subtype D in Uganda.

Characterization of Near Full-Length Transmitted/Founder HIV-1 Subtype D and A/D Recombinant Genomes in a Heterosexual Ugandan Population (2006–2011)

Detailed characterization of transmitted HIV-1 variants in Uganda is fundamentally important to inform vaccine design, yet studies on the transmitted full-length strains of subtype D viruses are limited. Here, we amplified single genomes and characterized viruses, some of which were previously classified as subtype D by sub-genomic pol sequencing that were transmitted in Uganda between December 2006 to June 2011. Analysis of 5′ and 3′ half genome sequences showed 73% (19/26) of infections involved single virus transmissions, whereas 27% (7/26) of infections involved multiple variant transmissions based on predictions of a model of random virus evolution. Subtype analysis of inferred transmitted/founder viruses showed a high transmission rate of inter-subtype recombinants (69%, 20/29) involving mainly A1/D, while pure subtype D variants accounted for one-third of infections (31%, 9/29). Recombination patterns included a predominance of subtype D in the gag/pol region and a highly recombinogenic envelope gene. The signal peptide-C1 region and gp41 transmembrane domain (Tat2/Rev2 flanking region) were hotspots for A1/D recombination events. Analysis of a panel of 14 transmitted/founder molecular clones showed no difference in replication capacity between subtype D viruses (n = 3) and inter-subtype mosaic recombinants (n = 11). However, individuals infected with high replication capacity viruses had a faster CD4 T cell loss. The high transmission rate of unique inter-subtype recombinants is striking and emphasizes the extraordinary challenge for vaccine design and, in particular, for the highly variable and recombinogenic envelope gene, which is targeted by rational designs aimed to elicit broadly neutralizing antibodies.

Prevalence of viral load suppression, predictors of virological failure and patterns of HIV drug resistance after 12 and 48 months on first-line antiretroviral therapy: a national cross-sectional survey in Uganda

Objectives

We implemented the WHO cross-sectional survey protocol to determine rates of HIV viral load (VL) suppression (VLS), and weighted prevalence, predictors and patterns of acquired drug resistance (ADR) in individuals with virological failure (VF) defined as VL ≥1000 copies/mL.

Methods

We enrolled 547 and 1064 adult participants on first-line ART for 12 (±3) months (ADR12) and ≥48 months (ADR48), respectively. Dried blood spots and plasma specimens were collected for VL testing and genotyping among the VFs.

Results

VLS was 95.0% (95% CI 93.4%–96.5%) in the ADR12 group and 87.9% (95% CI 85.0%–90.9%) in the ADR48 group. The weighted prevalence of ADR was 96.1% (95% CI 72.9%–99.6%) in the ADR12 and 90.4% (95% CI 73.6–96.8%) in the ADR48 group, out of the 30 and 95 successful genotypes in the respective groups. Initiation on a zidovudine-based regimen compared with a tenofovir-based regimen was significantly associated with VF in the ADR48 group; adjusted OR (AOR) 1.96 (95% CI 1.13–3.39). Independent predictors of ADR in the ADR48 group were initiation on a zidovudine-based regimen compared with tenofovir-based regimens, AOR 3.16 (95% CI 1.34–7.46) and ART duration of ≥82 months compared with <82 months, AOR 1.92 (95% CI 1.03–3.59).

Conclusions

While good VLS was observed, the high prevalence of ADR among the VFs before they underwent the recommended three intensive adherence counselling (IAC) sessions followed by repeat VL testing implies that IAC prior to treatment switching may be of limited benefit in improving VLS.

HIV-1 Gag-Pol Sequences from Ugandan Early Infections Reveal Sequence Variants Associated with Elevated Replication Capacity

The ability to efficiently establish a new infection is a critical property for human immunodeficiency virus type 1 (HIV-1). Although the envelope protein of the virus plays an essential role in receptor binding and internalization of the infecting virus, the structural proteins, the polymerase and the assembly of new virions may also play a role in establishing and spreading viral infection in a new host. We examined Ugandan viruses from newly infected patients and focused on the contribution of the Gag-Pol genes to replication capacity. A panel of Gag-Pol sequences generated using single genome amplification from incident HIV-1 infections were cloned into a common HIV-1 NL4.3 pol/env backbone and the influence of Gag-Pol changes on replication capacity was monitored. Using a novel protein domain approach, we then documented diversity in the functional protein domains across the Gag-Pol region and identified differences in the Gag-p6 domain that were frequently associated with higher in vitro replication.

Tracking HIV-1 recombination to resolve its contribution to HIV-1 evolution in natural infection

Recombination in HIV-1 is well documented, but its importance in the low-diversity setting of within-host diversification is less understood. Here we develop a novel computational tool (RAPR (Recombination Analysis PRogram)) to enable a detailed view of in vivo viral recombination during early infection, and we apply it to near-full-length HIV-1 genome sequences from longitudinal samples. Recombinant genomes rapidly replace transmitted/founder (T/F) lineages, with a median half-time of 27 days, increasing the genetic complexity of the viral population. We identify recombination hot and cold spots that differ from those observed in inter-subtype recombinants. Furthermore, RAPR analysis of longitudinal samples from an individual with well-characterized neutralizing antibody responses shows that recombination helps carry forward resistance-conferring mutations in the diversifying quasispecies. These findings provide insight into molecular mechanisms by which viral recombination contributes to HIV-1 persistence and immunopathogenesis and have implications for studies of HIV transmission and evolution in vivo.

Recombination contributes to HIV evolution in patients, but its identification can be difficult. Here, the authors develop a computational tool called RAPR to track recombination in patients, identify recombination hot spots, and show contribution of recombination to antibody escape.

Use of Dried Blood Spots to Elucidate Full-Length Transmitted/Founder HIV-1 Genomes

Background:

Identification of HIV-1 genomes responsible for establishing clinical infection in newly infected individuals is fundamental to prevention and pathogenesis research. Processing, storage, and transportation of the clinical samples required to perform these virologic assays in resource-limited settings requires challenging venipuncture and cold chain logistics. Here, we validate the use of dried-blood spots (DBS) as a simple and convenient alternative to collecting and storing frozen plasma.

Methods:

We performed parallel nucleic acid extraction, single genome amplification (SGA), next generation sequencing (NGS), and phylogenetic analyses on plasma and DBS.

Results:

We demonstrated the capacity to extract viral RNA from DBS and perform SGA to infer the complete nucleotide sequence of the transmitted/founder (TF) HIV-1 envelope gene and full-length genome in two acutely infected individuals. Using both SGA and NGS methodologies, we showed that sequences generated from DBS and plasma display comparable phylogenetic patterns in both acute and chronic infection. SGA was successful on samples with a range of plasma viremia, including samples as low as 1,700 copies/ml and an estimated ~50 viral copies per blood spot. Further, we demonstrated reproducible efficiency in gp160 env sequencing in DBS stored at ambient temperature for up to three weeks or at -20°C for up to five months.

Conclusions:

These findings support the use of DBS as a practical and cost-effective alternative to frozen plasma for clinical trials and translational research conducted in resource-limited settings.

HIV-1-Specific CD8 T Cells Exhibit Limited Cross-Reactivity during Acute Infection

Prior work has demonstrated that HIV-1-specific CD8 T cells can cross-recognize variant epitopes. However, most of these studies were performed in the context of chronic infection, where the presence of viral quasispecies makes it difficult to ascertain the true nature of the original antigenic stimulus. To overcome this limitation, we evaluated the extent of CD8 T cell cross-reactivity in patients with acute HIV-1 clade B infection. In each case, we determined the transmitted founder virus sequence to identify the autologous epitopes restricted by individual HLA class I molecules. Our data show that cross-reactive CD8 T cells are infrequent during the acute phase of HIV-1 infection. Moreover, in the uncommon instances where cross-reactive responses were detected, the variant epitopes were poorly recognized in cytotoxicity assays. Molecular analysis revealed that similar antigenic structures could be cross-recognized by identical CD8 T cell clonotypes mobilized in vivo, yet even subtle differences in a single TCR-accessible peptide residue were sufficient to disrupt variant-specific reactivity. These findings demonstrate that CD8 T cells are highly specific for autologous epitopes during acute HIV-1 infection. Polyvalent vaccines may therefore be required to provide optimal immune cover against this genetically labile pathogen.

Abstract C61: Genetic alterations in the TP53 genomic region of African American and Caucasian colorectal cancers

Purpose: In the US, colorectal cancer (CRC) is the second leading cause of cancer-related deaths and the third most common cancer in both men and women. CRC affects African Americans (AAs) disproportionately, relative to non-Hispanic Caucasians (CAs). Data from our prior studies indicate that the p53 codon 72 polymorphism is disproportionately higher in AAs compared to CAs [Clin Cancer Res; 15(14); 2406–-2416. 2009]. It is also evident that genetic human diversity is due not only to single nucleotide polymorphisms (SNPs), but also to structural variants or retrotransposons. Retrotransposons induce mutations, near or within genes by several mechanisms: insertions, deletions, duplications, copy number variants, inversions, or translocations, all of which expand human diversity and possibly alter cancer susceptibility. Thus, our objectives are to establish genomic profiles of the p53 tumor suppressor (TP53) region of CRCs of AA and CA patients to identify race/ethnic-specific alterations that are associated with ancestry, and to develop a DNA sequencing protocol to delineate AA and CA patient profiles using this complex genomic region (∼19 Kb).

Methods: Genomic DNA was extracted from 4 frozen tissue samples (2 CRCs and their corresponding normal pairs) and 4 (2 CRCs/normal pairs) formalin-fixed, paraffin-embedded (FFPE) tissues. For the DNA of two CRC patients (one tumor/normal pair each of AA and CA patients), the complete TP53 gene (∼19 Kb, including exons and introns) was amplified by PCR in two halves, followed by Illumina next-generation sequencing and comparison to the human genome 19 reference sequence. For each patient, paired normal (benign/control) and tumor tissue DNAs were compared.

Results: TheTP53 gene was amplified from DNA extracted from all 4 frozen CRC tissues, but not from the 4 FFPE tissues. Sequence comparisons of normal versus tumor DNA revealed 80 single nucleotide polymorphisms (SNPs). Most (96%, n=77) located within introns. Of these, 34 were shared by AA and CA patients. In contrast, 8 SNPs were detected only in a CA patient, and 13 others were present only in an AA patient. Two SNPs found in our AA patient were absent in our CA patient and in the publicly available HapMap database of CAs, suggesting that these SNPs reflect African ancestry. Also, 22 SNPs were exclusively present in the CA tumor, whereas only 3 SNPs were unique to the AA tumor. These findings deserve further investigation.

Conclusions: We developed PCR protocols that should allow us to conduct a comprehensive mutational profiling of coding and non-coding regions of the TP53 genomic region in DNA isolated from frozen tissues. Comparison of genetic alteration profiles of TP53 in AAs and CAs will aid in determining the race/ethnicity of CRC patients. These studies were supported by a Charles Barkley Foundation grant though the UAB MHRC and a pre-pilot project of the UAB/TU/MSM Partnership grant, U54-CA 118948.

Citation Format: Jesus F. Salazar-Gonzalez, Maria G. Salazar, Balananda Dhurjati Kumar Putcha, Edward E. Partridge, Mona N. Fouad, Manne Upender. Genetic alterations in the TP53 genomic region of African American and Caucasian colorectal cancers. [abstract]. In: Proceedings of the Sixth AACR Conference: The Science of Cancer Health Disparities; Dec 6–9, 2013; Atlanta, GA. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2014;23(11 Suppl):Abstract nr C61. doi:10.1158/1538-7755.DISP13-C61

Clonal amplification and maternal-infant transmission of nevirapine-resistant HIV-1 variants in breast milk following single-dose nevirapine prophylaxis

BACKGROUND

Intrapartum administration of single-dose nevirapine (sdNVP) reduces perinatal HIV-1 transmission in resource-limiting settings by half. Yet this strategy has limited effect on subsequent breast milk transmission, making the case for new treatment approaches to extend maternal/infant antiretroviral prophylaxis through the period of lactation. Maternal and transmitted infant HIV-1 variants frequently develop NVP resistance mutations following sdNVP, complicating subsequent treatment/prophylaxis regimens. However, it is not clear whether NVP-resistant viruses are transmitted via breastfeeding or arise de novo in the infant.

FINDINGS

We performed a detailed HIV genetic analysis using single genome sequencing to identify the origin of drug-resistant variants in an sdNVP-treated postnatally-transmitting mother-infant pair. Phylogenetic analysis of HIV sequences from the child revealed low-diversity variants indicating infection by a subtype C single transmitted/founder virus that shared full-length sequence identity with a clonally-amplified maternal breast milk virus variant harboring the K103N NVP resistance mutation.

CONCLUSION

In this mother/child pair, clonal amplification of maternal NVP-resistant HIV variants present in systemic and mammary gland compartments following intrapartum sdNVP represents one source of transmitted NVP-resistant variants that is responsible for the acquisition of drug resistant virus by the breastfeeding infant. This finding emphasizes the need for combination antiretroviral prophylaxis to prevent mother-to-child HIV transmission.

Comparison of viral Env proteins from acute and chronic infections with subtype C human immunodeficiency virus type 1 identifies differences in glycosylation and CCR5 utilization and suggests a new strategy for immunogen design

Understanding human immunodeficiency virus type 1 (HIV-1) transmission is central to developing effective prevention strategies, including a vaccine. We compared phenotypic and genetic variation in HIV-1 env genes from subjects in acute/early infection and subjects with chronic infections in the context of subtype C heterosexual transmission. We found that the transmitted viruses all used CCR5 and required high levels of CD4 to infect target cells, suggesting selection for replication in T cells and not macrophages after transmission. In addition, the transmitted viruses were more likely to use a maraviroc-sensitive conformation of CCR5, perhaps identifying a feature of the target T cell. We confirmed an earlier observation that the transmitted viruses were, on average, modestly underglycosylated relative to the viruses from chronically infected subjects. This difference was most pronounced in comparing the viruses in acutely infected men to those in chronically infected women. These features of the transmitted virus point to selective pressures during the transmission event. We did not observe a consistent difference either in heterologous neutralization sensitivity or in sensitivity to soluble CD4 between the two groups, suggesting similar conformations between viruses from acute and chronic infection. However, the presence or absence of glycosylation sites had differential effects on neutralization sensitivity for different antibodies. We suggest that the occasional absence of glycosylation sites encoded in the conserved regions of env, further reduced in transmitted viruses, could expose specific surface structures on the protein as antibody targets.

Postnatally-transmitted HIV-1 Envelope variants have similar neutralization-sensitivity and function to that of nontransmitted breast milk variants

Background

Breastfeeding is a leading cause of infant HIV-1 infection in the developing world, yet only a minority of infants exposed to HIV-1 via breastfeeding become infected. As a genetic bottleneck severely restricts the number of postnatally-transmitted variants, genetic or phenotypic properties of the virus Envelope (Env) could be important for the establishment of infant infection. We examined the efficiency of virologic functions required for initiation of infection in the gastrointestinal tract and the neutralization sensitivity of HIV-1 Env variants isolated from milk of three postnatally-transmitting mothers (n=13 viruses), five clinically-matched nontransmitting mothers (n=16 viruses), and seven postnatally-infected infants (n = 7 postnatally-transmitted/founder (T/F) viruses).

Results

There was no difference in the efficiency of epithelial cell interactions between Env virus variants from the breast milk of transmitting and nontransmitting mothers. Moreover, there was similar efficiency of DC-mediated trans-infection, CCR5-usage, target cell fusion, and infectivity between HIV-1 Env-pseudoviruses from nontransmitting mothers and postnatal T/F viruses. Milk Env-pseudoviruses were generally sensitive to neutralization by autologous maternal plasma and resistant to breast milk neutralization. Infant T/F Env-pseudoviruses were equally sensitive to neutralization by broadly-neutralizing monoclonal and polyclonal antibodies as compared to nontransmitted breast milk Env variants.

Conclusion

Postnatally-T/F Env variants do not appear to possess a superior ability to interact with and cross a mucosal barrier or an exceptional resistance to neutralization that define their capability to initiate infection across the infant gastrointestinal tract in the setting of preexisting maternal antibodies.

Transmitted/founder and chronic subtype C HIV-1 use CD4 and CCR5 receptors with equal efficiency and are not inhibited by blocking the integrin α4β7

Sexual transmission of human immunodeficiency virus type 1 (HIV-1) most often results from productive infection by a single transmitted/founder (T/F) virus, indicating a stringent mucosal bottleneck. Understanding the viral traits that overcome this bottleneck could have important implications for HIV-1 vaccine design and other prevention strategies. Most T/F viruses use CCR5 to infect target cells and some encode envelope glycoproteins (Envs) that contain fewer potential N-linked glycosylation sites and shorter V1/V2 variable loops than Envs from chronic viruses. Moreover, it has been reported that the gp120 subunits of certain transmitted Envs bind to the gut-homing integrin α4β7, possibly enhancing virus entry and cell-to-cell spread. Here we sought to determine whether subtype C T/F viruses, which are responsible for the majority of new HIV-1 infections worldwide, share biological properties that increase their transmission fitness, including preferential α4β7 engagement. Using single genome amplification, we generated panels of both T/F (n = 20) and chronic (n = 20) Env constructs as well as full-length T/F (n = 6) and chronic (n = 4) infectious molecular clones (IMCs). We found that T/F and chronic control Envs were indistinguishable in the efficiency with which they used CD4 and CCR5. Both groups of Envs also exhibited the same CD4+ T cell subset tropism and showed similar sensitivity to neutralization by CD4 binding site (CD4bs) antibodies. Finally, saturating concentrations of anti-α4β7 antibodies failed to inhibit infection and replication of T/F as well as chronic control viruses, although the growth of the tissue culture-adapted strain SF162 was modestly impaired. These results indicate that the population bottleneck associated with mucosal HIV-1 acquisition is not due to the selection of T/F viruses that use α4β7, CD4 or CCR5 more efficiently.

Most new HIV-1 infections worldwide are caused by the sexual transmission of subtype C viruses, which are prevalent in Asia and southern Africa. While chronically infected individuals harbor a genetically diverse set of viruses, most new infections are established by single variants, termed transmitted/founder (T/F) viruses. This raises the question whether certain viral variants have particular properties allowing them to more efficiently overcome the transmission bottleneck. Preferential binding of the viral envelope (Env) to the integrin α4β7 has been hypothesized as one important feature of transmitted viruses. Here, we compared Envs from subtype C viruses that were transmitted to those that were prevalent in chronic infections for efficiency in utilizing α4β7, CD4 and CCR5 for cell entry and replication. We found that transmitted and chronic Envs engaged CD4 and CCR5 with equal efficiency, and that blocking the interaction between Env and α4β7 failed to inhibit replication of T/F as well as control viruses. While the search for determinants of transmission fitness remains an important goal, preferential CD4, CCR5 or α4β7 interactions do not appear to represent distinguishing features of T/F viruses.

Recurrent signature patterns in HIV-1 B clade envelope glycoproteins associated with either early or chronic infections

Here we have identified HIV-1 B clade Envelope (Env) amino acid signatures from early in infection that may be favored at transmission, as well as patterns of recurrent mutation in chronic infection that may reflect common pathways of immune evasion. To accomplish this, we compared thousands of sequences derived by single genome amplification from several hundred individuals that were sampled either early in infection or were chronically infected. Samples were divided at the outset into hypothesis-forming and validation sets, and we used phylogenetically corrected statistical strategies to identify signatures, systematically scanning all of Env. Signatures included single amino acids, glycosylation motifs, and multi-site patterns based on functional or structural groupings of amino acids. We identified signatures near the CCR5 co-receptor-binding region, near the CD4 binding site, and in the signal peptide and cytoplasmic domain, which may influence Env expression and processing. Two signatures patterns associated with transmission were particularly interesting. The first was the most statistically robust signature, located in position 12 in the signal peptide. The second was the loss of an N-linked glycosylation site at positions 413-415; the presence of this site has been recently found to be associated with escape from potent and broad neutralizing antibodies, consistent with enabling a common pathway for immune escape during chronic infection. Its recurrent loss in early infection suggests it may impact fitness at the time of transmission or during early viral expansion. The signature patterns we identified implicate Env expression levels in selection at viral transmission or in early expansion, and suggest that immune evasion patterns that recur in many individuals during chronic infection when antibodies are present can be selected against when the infection is being established prior to the adaptive immune response.

Cross-sectional detection of acute HIV infection: timing of transmission, inflammation and antiretroviral therapy

BACKGROUND

Acute HIV infection (AHI) is a critical phase of infection when irreparable damage to the immune system occurs and subjects are very infectious. We studied subjects with AHI prospectively to develop better treatment and public health interventions.

METHODS

Cross-sectional screening was employed to detect HIV RNA positive, antibody negative subjects. Date of HIV acquisition was estimated from clinical history and correlated with sequence diversity assessed by single genome amplification (SGA). Twenty-two cytokines/chemokines were measured from enrollment through week 24.

RESULTS

Thirty-seven AHI subjects were studied. In 7 participants with limited exposure windows, the median exposure to HIV occurred 14 days before symptom onset. Lack of viral sequence diversification confirmed the short duration of infection. Transmission dates estimated by SGA/sequencing using molecular clock models correlated with transmission dates estimated by symptom onset in individuals infected with single HIV variants (mean of 28 versus 33 days). Only 10 of 22 cytokines/chemokines were significantly elevated among AHI participants at enrollment compared to uninfected controls, and only 4 participants remained seronegative at enrollment.

DISCUSSION

The results emphasize the difficulty in recruiting subjects early in AHI. Viral sequence diversity proved accurate in estimating time of infection. Regardless of aggressive screening, peak viremia and inflammation occurred before enrollment and potential intervention. Given the personal and public health importance, improved AHI detection is urgently needed.

Relationship between functional profile of HIV-1 specific CD8 T cells and epitope variability with the selection of escape mutants in acute HIV-1 infection

In the present study, we analyzed the functional profile of CD8⁺ T-cell responses directed against autologous transmitted/founder HIV-1 isolates during acute and early infection, and examined whether multifunctionality is required for selection of virus escape mutations. Seven anti-retroviral therapy-naïve subjects were studied in detail between 1 and 87 weeks following onset of symptoms of acute HIV-1 infection. Synthetic peptides representing the autologous transmitted/founder HIV-1 sequences were used in multiparameter flow cytometry assays to determine the functionality of HIV-1-specific CD8⁺ T memory cells. In all seven patients, the earliest T cell responses were predominantly oligofunctional, although the relative contribution of multifunctional cell responses increased significantly with time from infection. Interestingly, only the magnitude of the total and not of the poly-functional T-cell responses was significantly associated with the selection of escape mutants. However, the high contribution of MIP-1β-producing CD8⁺ T-cells to the total response suggests that mechanisms not limited to cytotoxicity could be exerting immune pressure during acute infection. Lastly, we show that epitope entropy, reflecting the capacity of the epitope to tolerate mutational change and defined as the diversity of epitope sequences at the population level, was also correlated with rate of emergence of escape mutants.

An important role for the polyfunctional T-cell fraction of anti-HIV CD8 responses during chronic HIV infection has previously been suggested. This study characterized the role of polyfunctional T-cells directed against the transmitted/founder virus in the selection of viral escape mutants during acute HIV-1 infection within a unique cohort of individuals recruited within 3 weeks from the onset of symptoms at the time when the virus load was still declining. For the first time, the sequences of the transmitted/founder virus isolated from each patient were used. Interestingly, polyfunctionality was not found to be a pre-requisite for selection of escape mutations. A novel significant correlation is found between the order of appearance of escape mutations in different epitope sequences and both the magnitude of the CD8⁺ T-cell responses and the degree of entropy of the individual epitopes. A high proportion of the T-cells participating in the total response produced MIP-1β, suggesting that mechanisms not limited to the killing of infected cells might play a relevant role in early infection. This highlights the importance of measuring the quality of the CD8⁺ lymphocyte response and the sequence of the transmitted virus isolates to better understand the mechanisms of control of HIV replication during acute infection.

HIV gene expression from intact proviruses positioned in bacterial artificial chromosomes at integration sites previously identified in latently infected T cells

HIV integration predominantly occurs in introns of transcriptionally active genes. To study the impact of the integration site on HIV gene expression, a complete HIV-1 provirus (with GFP as a fusion with Nef) was inserted into bacterial artificial chromosomes (BACs) at three sites previously identified in latent T cells of patients: topoisomerase II (Top2A), DNA methyltransferase 1 (DNMT1), or basic leucine transcription factor 2 (BACH2). Transfection of BAC-HIV into 293T cells resulted in a fourfold difference in production of infectious HIV-1. Cell lines were established that contained BAC-Top2A, BAC-DNMT1, or BAC-BACH2, but only BAC-DNMT1 spontaneously produced virus, albeit at a low level. Stimulation with TNF-α resulted in virus production from four of five BAC-Top2A and all BAC-DNMT1 cell lines, but not from the BAC-BACH2 lines. The results of these studies highlight differences between integration sites identified in latent T cells to support virus production and reactivation from latency.

High Multiplicity Infection by HIV-1 in Men Who Have Sex with Men

Elucidating virus-host interactions responsible for HIV-1 transmission is important for advancing HIV-1 prevention strategies. To this end, single genome amplification (SGA) and sequencing of HIV-1 within the context of a model of random virus evolution has made possible for the first time an unambiguous identification of transmitted/founder viruses and a precise estimation of their numbers. Here, we applied this approach to HIV-1 env analyses in a cohort of acutely infected men who have sex with men (MSM) and found that a high proportion (10 of 28; 36%) had been productively infected by more than one virus. In subjects with multivariant transmission, the minimum number of transmitted viruses ranged from 2 to 10 with viral recombination leading to rapid and extensive genetic shuffling among virus lineages. A combined analysis of these results, together with recently published findings based on identical SGA methods in largely heterosexual (HSX) cohorts, revealed a significantly higher frequency of multivariant transmission in MSM than in HSX [19 of 50 subjects (38%) versus 34 of 175 subjects (19%); Fisher's exact p = 0.008]. To further evaluate the SGA strategy for identifying transmitted/founder viruses, we analyzed 239 overlapping 5′ and 3′ half genome or env-only sequences from plasma viral RNA (vRNA) and blood mononuclear cell DNA in an MSM subject who had a particularly well-documented virus exposure history 3–6 days before symptom onset and 14–17 days before peak plasma viremia (47,600,000 vRNA molecules/ml). All 239 sequences coalesced to a single transmitted/founder virus genome in a time frame consistent with the clinical history, and a molecular clone of this genome encoded replication competent virus in accord with model predictions. Higher multiplicity of HIV-1 infection in MSM compared with HSX is consistent with the demonstrably higher epidemiological risk of virus acquisition in MSM and could indicate a greater challenge for HIV-1 vaccines than previously recognized.

Understanding the biology of sexual transmission of HIV-1 could contribute importantly to the development of effective prevention measures. However, different routes of virus transmission (vaginal, rectal, penile or oral) and inaccessibility of tissues at or near the time of virus transmission make this goal elusive. Here, we apply single genome amplification and sequencing of plasma HIV-1 and a model of random virus evolution to a cohort of acutely infected men who have sex with men (MSM) and find that MSM are twice as likely as heterosexuals to become infected by multiple viruses as opposed to a single virus. Some MSM subjects were infected by as many as 7 to 10 or more genetically distinct viruses as a consequence of a single exposure event. We go on to molecularly clone the first full-length transmitted/founder subtype B HIV-1 virus and show that it is highly replicative in human CD4+ T-cells but not macrophages. Our study provides the first comparative, quantitative analysis of the multiplicity of HIV-1 infection in the two primary risk groups—MSM and heterosexuals—driving the global pandemic, and we discuss the implications of the findings to HIV-1 vaccine development and prevention research.

A rev1-vpu polymorphism unique to HIV-1 subtype A and C strains impairs envelope glycoprotein expression from rev-vpu-env cassettes and reduces virion infectivity in pseudotyping assays

Functional studies of HIV-1 envelope glycoproteins (Envs) commonly include the generation of pseudoviruses, which are produced by co-transfection of rev-vpu-env cassettes with an env-deficient provirus. Here, we describe six Env constructs from transmitted/founder HIV-1 that were defective in the pseudotyping assay, although two produced infectious virions when expressed from their cognate proviruses. All of these constructs exhibited an unusual gene arrangement in which the first exon of rev (rev1) and vpu were in the same reading frame without an intervening stop codon. Disruption of the rev1-vpu fusion gene by frameshift mutation, stop codon, or abrogation of the rev initiation codon restored pseudovirion infectivity. Introduction of the fusion gene into wildtype Env cassettes severely compromised their function. The defect was not due to altered env and rev transcription or a dominant negative effect of the expressed fusion protein, but seemed to be caused by inefficient translation at the env initiation codon. Although the rev1-vpu polymorphism affects Env expression only in vitro, it can cause problems in studies requiring Env complementation, such as analyses of co-receptor usage and neutralization properties, since 3% of subtype A, 20% of subtype C and 5% of CRF01_A/E viruses encode the fusion gene. A solution is to eliminate the rev initiation codon when amplifying rev-vpu-env cassettes since this increases Env expression irrespective of the presence of the polymorphism.

Modeling sequence evolution in acute HIV-1 infection

We describe a mathematical model and Monte Carlo (MC) simulation of viral evolution during acute infection. We consider both synchronous and asynchronous processes of viral infection of new target cells. The model enables an assessment of the expected sequence diversity in new HIV-1 infections originating from a single transmitted viral strain, estimation of the most recent common ancestor (MRCA) of the transmitted viral lineage, and estimation of the time to coalesce back to the MRCA. We also calculate the probability of the MRCA being the transmitted virus or an evolved variant. Excluding insertions and deletions, we assume HIV-1 evolves by base substitution without selection pressure during the earliest phase of HIV-1 infection prior to the immune response. Unlike phylogenetic methods that follow a lineage backwards to coalescence, we compare the observed data to a model of the diversification of a viral population forward in time. To illustrate the application of these methods, we provide detailed comparisons of the model and simulations results to 306 envelope sequences obtained from eight newly infected subjects at a single time point. The data from 68 patients were in good agreement with model predictions, and hence compatible with a single-strain infection evolving under no selection pressure. The diversity of the samples from the other two patients was too great to be explained by the model, suggesting multiple HIV-1-strains were transmitted. The model can also be applied to longitudinal patient data to estimate within-host viral evolutionary parameters.

Genetic identity, biological phenotype, and evolutionary pathways of transmitted/founder viruses in acute and early HIV-1 infection

Identification of full-length transmitted HIV-1 genomes could be instrumental in HIV-1 pathogenesis, microbicide, and vaccine research by enabling the direct analysis of those viruses actually responsible for productive clinical infection. We show in 12 acutely infected subjects (9 clade B and 3 clade C) that complete HIV-1 genomes of transmitted/founder viruses can be inferred by single genome amplification and sequencing of plasma virion RNA. This allowed for the molecular cloning and biological analysis of transmitted/founder viruses and a comprehensive genome-wide assessment of the genetic imprint left on the evolving virus quasispecies by a composite of host selection pressures. Transmitted viruses encoded intact canonical genes (gag-pol-vif-vpr-tat-rev-vpu-env-nef) and replicated efficiently in primary human CD4⁺ T lymphocytes but much less so in monocyte-derived macrophages. Transmitted viruses were CD4 and CCR5 tropic and demonstrated concealment of coreceptor binding surfaces of the envelope bridging sheet and variable loop 3. 2 mo after infection, transmitted/founder viruses in three subjects were nearly completely replaced by viruses differing at two to five highly selected genomic loci; by 12–20 mo, viruses exhibited concentrated mutations at 17–34 discrete locations. These findings reveal viral properties associated with mucosal HIV-1 transmission and a limited set of rapidly evolving adaptive mutations driven primarily, but not exclusively, by early cytotoxic T cell responses.

The first T cell response to transmitted/founder virus contributes to the control of acute viremia in HIV-1 infection

Identification of the transmitted/founder virus makes possible, for the first time, a genome-wide analysis of host immune responses against the infecting HIV-1 proteome. A complete dissection was made of the primary HIV-1–specific T cell response induced in three acutely infected patients. Cellular assays, together with new algorithms which identify sites of positive selection in the virus genome, showed that primary HIV-1–specific T cells rapidly select escape mutations concurrent with falling virus load in acute infection. Kinetic analysis and mathematical modeling of virus immune escape showed that the contribution of CD8 T cell–mediated killing of productively infected cells was earlier and much greater than previously recognized and that it contributed to the initial decline of plasma virus in acute infection. After virus escape, these first T cell responses often rapidly waned, leaving or being succeeded by T cell responses to epitopes which escaped more slowly or were invariant. These latter responses are likely to be important in maintaining the already established virus set point. In addition to mutations selected by T cells, there were other selected regions that accrued mutations more gradually but were not associated with a T cell response. These included clusters of mutations in envelope that were targeted by NAbs, a few isolated sites that reverted to the consensus sequence, and bystander mutations in linkage with T cell–driven escape.

Genetic and neutralization properties of subtype C human immunodeficiency virus type 1 molecular env clones from acute and early heterosexually acquired infections in Southern Africa

A standard panel of subtype C human immunodeficiency virus type 1 (HIV-1) Env-pseudotyped viruses was created by cloning, sequencing, and characterizing functional gp160 genes from 18 acute and early heterosexually acquired infections in South Africa and Zambia. In general, the gp120 region of these clones was shorter (most evident in V1 and V4) and less glycosylated compared to newly transmitted subtype B viruses, and it was underglycosylated but no different in length compared to chronic subtype C viruses. The gp120s also exhibited low amino acid sequence variability (12%) in V3 and high variability (39%) immediately downstream of V3, a feature shared with newly transmitted subtype B viruses and chronic viruses of both subtypes. When tested as Env-pseudotyped viruses in a luciferase reporter gene assay, all clones possessed an R5 phenotype and resembled primary isolates in their sensitivity to neutralization by HIV-1-positive plasmas. Results obtained with a multisubtype plasma panel suggested partial subtype preference in the neutralizing antibody response to infection. The clones were typical of subtype C in that all were resistant to 2G12 (associated with loss of N-glycosylation at position 295) and most were resistant to 2F5, but all were sensitive to 4E10 and many were sensitive to immunoglobulin G1b12. Finally, conserved neutralization epitopes in the CD4-induced coreceptor binding domain of gp120 were poorly accessible and were difficult to induce and stabilize with soluble CD4 on Env-pseudotyped viruses. These results illustrate key genetic and antigenic properties of subtype C HIV-1 that might impact the design and testing of candidate vaccines. A subset of these gp160 clones are suitable for use as reference reagents to facilitate standardized assessments of vaccine-elicited neutralizing antibody responses.

Antigenicity and immunogenicity of HIV-1 consensus subtype B envelope glycoproteins

"Centralized" (ancestral and consensus) HIV-1 envelope immunogens induce broadly cross-reactive T cell responses in laboratory animals; however, their potential to elicit cross-reactive neutralizing antibodies has not been fully explored. Here, we report the construction of a panel of consensus subtype B (ConB) envelopes and compare their biologic, antigenic, and immunogenic properties to those of two wild-type Env controls from individuals with early and acute HIV-1 infection. Glycoprotein expressed from full-length (gp160), uncleaved (gp160-UNC), truncated (gp145), and N-linked glycosylation site deleted (gp160-201N/S) versions of the ConB env gene were packaged into virions and, except for the fusion defective gp160-UNC, mediated infection via the CCR5 co-receptor. Pseudovirions containing ConB Envs were sensitive to neutralization by patient plasma and monoclonal antibodies, indicating the preservation of neutralizing epitopes found in contemporary subtype B viruses. When used as DNA vaccines in guinea pigs, ConB and wild-type env immunogens induced appreciable binding, but overall only low level neutralizing antibodies. However, all four ConB immunogens were significantly more potent than one wild-type vaccine at eliciting neutralizing antibodies against a panel of tier 1 and tier 2 viruses, and ConB gp145 and gp160 were significantly more potent than both wild-type vaccines at inducing neutralizing antibodies against tier 1 viruses. Thus, consensus subtype B env immunogens appear to be at least as good as, and in some instances better than, wild-type B env immunogens at inducing a neutralizing antibody response, and are amenable to further improvement by specific gene modifications.

Human immunodeficiency virus type 1 env clones from acute and early subtype B infections for standardized assessments of vaccine-elicited neutralizing antibodies

Induction of broadly cross-reactive neutralizing antibodies is a high priority for AIDS vaccine development but one that has proven difficult to be achieved. While most immunogens generate antibodies that neutralize a subset of T-cell-line-adapted strains of human immunodeficiency virus type 1 (HIV-1), none so far have generated a potent, broadly cross-reactive response against primary isolates of the virus. Even small increments in immunogen improvement leading to increases in neutralizing antibody titers and cross-neutralizing activity would accelerate vaccine development; however, a lack of uniformity in target strains used by different investigators to assess cross-neutralization has made the comparison of vaccine-induced antibody responses difficult. Thus, there is an urgent need to establish standard panels of HIV-1 reference strains for wide distribution. To facilitate this, full-length gp160 genes were cloned from acute and early subtype B infections and characterized for use as reference reagents to assess neutralizing antibodies against clade B HIV-1. Individual gp160 clones were screened for infectivity as Env-pseudotyped viruses in a luciferase reporter gene assay in JC53-BL (TZM-bl) cells. Functional env clones were sequenced and their neutralization phenotypes characterized by using soluble CD4, monoclonal antibodies, and serum samples from infected individuals and noninfected recipients of a recombinant gp120 vaccine. Env clones from 12 R5 primary HIV-1 isolates were selected that were not unusually sensitive or resistant to neutralization and comprised a wide spectrum of genetic, antigenic, and geographic diversity. These reference reagents will facilitate proficiency testing and other validation efforts aimed at improving assay performance across laboratories and can be used for standardized assessments of vaccine-elicited neutralizing antibodies.

Employment of microarray analysis to characterize biologic differences associated with tropism-modified adenoviral vectors: utilization of non-native cellular entry pathways

In this study, we have applied high-density oligonucleotide microarray technology to characterize biologic changes associated with adenoviral vector-mediated target cell infection. We infected a human melanoma cell line, M21, with the tropism-modified vectors, Ad5lucRGD and Ad5/3luc1. In addition, we infected the M21 cell line with the Ad5luc1, a vector which primarily exploits the coxsackie and adenovirus receptor, as its primary native receptor. We found significant changes in gene expression of 5492 genes induced by Ad5luc1 infection, 2439 genes induced by Ad5/3luc1 infection, and 1251 genes induced by Ad5lucRGD infection, compared to uninfected cells. Among these changes in gene expression, 783 changes were common to Ad5/3luc1 and Ad5luc1 infections, 266 were common to Ad5lucRGD and Ad5luc1 infections, and 185 changes in gene expression were common to Ad5/3luc1 and Ad5lucRGD infections. Interestingly, 89 changes in gene expression were common to all the three groups, suggesting a commonly affected pathway. This analysis represents a unique application of microarray to study vector-related issues. Furthermore, these studies demonstrate the utility of microarray for characterizing the biologic sequelae of host-vector interaction.

Macrophage HIV-1 infection and the gastrointestinal tract reservoir

Excluding parenteral transmissions, virtually all vertical and homosexual transmission of human immunodeficiency virus type 1 (HIV-1) occurs via the gastrointestinal tract. Cellular routes implicated in the translocation of virus across the epithelium include M cells, dendritic cells, and epithelial cells. Intestinal epithelial cells express CCR5 and can selectively transfer CCR5-tropic HIV-1, the phenotype of the majority of transmitted viruses. In the lamina propria, virus encounters the largest reservoir of mononuclear cells in the body. Surprisingly, lamina propria lymphocytes, not macrophages, express CCR5 and CXCR4 and support HIV-1 replication, implicating intestinal lymphocytes as the initial target cell in the intestinal mucosa. From the mucosa, virus is disseminated to systemic sites, followed by profound depletion of CD4+ T cells, first in the intestinal lamina propria and subsequently in the blood. As mucosal and circulating CD4+ T cells are depleted, monocytes and macrophages assume an increasingly important role as target and reservoir cells for HIV-1. Blood monocytes, including HIV-1-infected cells, are recruited to the mucosa, where they differentiate into lamina propria macrophages in the presence of stroma-derived factors. Although the prevalence of HIV-1-infected macrophages in the mucosa is low (0.06% of lamina propria mononuclear cells), the extraordinary size of the gastrointestinal mucosa imparts to intestinal macrophages a prominent role as a HIV-1 reservoir. Elucidating the immunobiology of mucosal HIV-1 infection is critical for understanding disease pathogenesis and ultimately for devising an effective mucosal HIV-1 vaccine.

Antibody neutralization and escape by HIV-1

Neutralizing antibodies (Nab) are a principal component of an effective human immune response to many pathogens, yet their role in HIV-1 infection is unclear. To gain a better understanding of this role, we examined plasma from patients with acute HIV infection. Here we report the detection of autologous Nab as early as 52 days after detection of HIV-specific antibodies. The viral inhibitory activity of Nab resulted in complete replacement of neutralization-sensitive virus by successive populations of resistant virus. Escape virus contained mutations in the env gene that were unexpectedly sparse, did not map generally to known neutralization epitopes, and involved primarily changes in N-linked glycosylation. This pattern of escape, and the exceptional density of HIV-1 envelope glycosylation generally, led us to postulate an evolving 'glycan shield' mechanism of neutralization escape whereby selected changes in glycan packing prevent Nab binding but not receptor binding. Direct support for this model was obtained by mutational substitution showing that Nab-selected alterations in glycosylation conferred escape from both autologous antibody and epitope-specific monoclonal antibodies. The evolving glycan shield thus represents a new mechanism contributing to HIV-1 persistence in the face of an evolving antibody repertoire.

Quercetin inhibits human vascular smooth muscle cell proliferation and migration

BACKGROUND

The French paradox has been associated with regular intake of red wine, which is enriched with flavonoids. Quercetin, a flavonoid present in the human diet, exerts cardiovascular protection through its antioxidant properties. We hypothesized that the beneficial effect of quercetin also could be related to the inhibition of vascular smooth muscle cell proliferation and migration.

METHODS

Human aortic smooth muscle cells (AoSMC) were grown in culture in the presence of serum. Quercetin inhibited the serum-induced proliferation of AoSMC. This inhibition was dose-dependent and not attributed to toxicity. Cell cycle analysis revealed that quercetin arrested AoSMC in the G(0)/G(1) phase. The effect of quercetin on AoSMC migration was examined using explant migration and Transwell migration assays. Quercetin significantly decreased migration in both assays in a consistent manner. Finally, Western blot analysis of AoSMC exposed to quercetin demonstrated a significant reduction in the activation of mitogen-activated protein kinase, a signaling pathway associated with the migration of vascular smooth muscle cells.

CONCLUSIONS

Quercetin inhibits the proliferation and migration of AoSMC, concomitant with inhibition of mitogen-activated protein kinase phosphorylation. These findings provide new insights and a rationale for the potential use of quercetin in the prophylaxis of cardiovascular diseases.

Increased immune activation precedes the inflection point of CD4 T cells and the increased serum virus load in human immunodeficiency virus infection

The temporal relationship of serum levels of human immunodeficiency virus (HIV) RNA and of immune activation products in 10 HIV-seropositive persons who showed an accelerated decline (inflection point) in CD4 T cell counts and went on to develop AIDS and in 10 matched controls without inflection point were examined. Cases and controls did not differ statistically at the baseline time point for this study. CD4 cell inflection points occurred 18-30 months before AIDS development. Serum levels of soluble tumor necrosis factor receptor II, soluble interleukin-2 receptor, beta2-microglobulin, and neopterin increased significantly > or = 6 months before the CD4 cell inflection point. In contrast, increases in mean HIV RNA levels occurred at the time of the CD4 cell inflection point. These data are consistent with the view that in vivo immune activation precedes the increases in virus load and is followed by an accelerated and rapid loss of CD4 lymphocytes.

Quantification of cytokine mRNA in peripheral blood mononuclear cells using branched DNA (bDNA) technology

Changes in the patterns of cytokine expression are thought to be of central importance in human infectious and inflammatory diseases. As such, there is a need for precise, reproducible assays for quantification of cytokine mRNA that are amenable to routine use in a clinical setting. In this report, we describe the design and performance of a branched DNA (bDNA) assay for the direct quantification of multiple cytokine mRNA levels in peripheral blood mononuclear cells (PBMCs). Oligonucleotide target probe sets were designed for several human cytokines, including TNFalpha, IL-2, IL-4, IL-6, IL-10, and IFNgamma. The bDNA assay yielded highly reproducible quantification of cytokine mRNAs, exhibited a broad linear dynamic range of over 3-log10, and showed a sensitivity sufficient to measure at least 3000 molecules. The potential clinical utility of the bDNA assay was explored by measuring cytokine mRNA levels in PBMCs from healthy and immunocompromised individuals. Cytokine expression levels in PBMCs from healthy blood donors were found to remain relatively stable over a one-month period of time. Elevated levels of IFNgamma mRNA were detected in PBMCs from HIV-1 seropositive individuals, but no differences in mean levels of TNFalpha or IL-6 mRNA were detected between seropositive and seronegative individuals. By providing a reproducible method for quantification of low abundance transcripts in clinical specimens, the bDNA assay may be useful for studies addressing the role of cytokine expression in disease.

Relationship of plasma HIV-RNA levels and levels of TNF-alpha and immune activation products in HIV infection

The goal of this study was to determine the relationship between plasma human immunodeficiency virus (HIV) load and cytokine expression. HIV-RNA plasma levels were determined in 34 HIV-seropositive (HIV+) asymptomatic subjects [range: 0.5 to 211 kiloequivalents (kEq)/ml HIV-RNAJ, by a modified branched-DNA (bDNA) assay. Plasma HIV-RNA levels were positively correlated with increased plasma levels of TNF-alpha, soluble TNF receptor type II, soluble IL-2 receptor, beta 2-microglobulin, and neopterin, but not with plasma IL-6 levels. In contrast, increased viral load and diminished CD4 counts correlated weakly. TNF-alpha mRNA levels, as determined by bDNA technology, were not significantly increased in peripheral blood mononuclear cells (PBMC) isolated from HIV-infected subjects, compared to HIV-seronegative (HIV-) subjects, and were not correlated with plasma levels of HIV-RNA, cytokines, or activation markers. These results are consistent with the hypothesis that a self-reinforcing mechanism exists between TNF-alpha production and generalized immune activation on one hand with HIV replication on the other.

Circulating CD8 T cells show increased interferon-gamma mRNA expression in HIV infection

IFN-gamma mRNA levels were measured in unstimulated PBMC and purified cell subpopulations, utilizing branched DNA assays, to characterize the cell type(s) that contribute to the in vivo increase in IFN-gamma gene expression seen in HIV infection. PBMC and CD8 T cells from HIV-seropositive subjects (HIV+) showed 2.5-fold increases in mean IFN-gamma mRNA levels compared to HIV-uninfected subjects (HIV-). Within individuals, CD8 T cells showed the highest IFN-gamma expression regardless of HIV status, which suggests that HIV infection enhances the IFN-gamma gene expression in CD8 T cells rather than inducing a shift to and/or increasing expression of IFN-gamma mRNA in other cell types. HIV+ subjects with increased PBMC IFN-gamma mRNA had elevated plasma levels of HIV RNA, neopterin, and beta 2-microglobulin. No differences in IFN-gamma mRNA levels were seen among HIV+ stratified by CD4 T cell number. Increased IFN-gamma may result from or be a contributing factor to increased viral load.

Histamine blocks interleukin 2 (IL-2) gene expression and regulates IL-2 receptor expression

Histamine inhibited the proliferative response of human peripheral blood mononuclear cells (PBMC) to the T cell mitogen Phytohemagglutinin-P (PHA-P) in a dose-dependent fashion. This inhibition was mediated via the H2 receptor since cimetidine, a known H2 antagonist, removed the inhibition, whereas the addition of the H1 antagonist Diphenhydramine did not. Inhibition occurred during the inductive phase of the cell cycle, since histamine added 24 hours after PHA-P stimulation had no effect on subsequent T cell proliferation, and was attributable to inhibition of interleukin-2 (IL-2) gene expression. Both secreted IL-2 and messenger RNA coding for IL-2 were inhibited by histamine. In contrast, histamine exerted no inhibitory effect on the expression of cell surface receptors for IL-2 as determined by flow cytometry. Furthermore, histamine-treated cells retained full responsiveness to exogenously administered IL-2, which completely reversed the anti-proliferative effect of histamine. In some donors, histamine enhanced the percentage of IL-2 receptor positive cells. Stimulated PBMC from AIDS KS patients as a group, displayed a lower percentage of IL-2 receptor bearing cells, which was significantly increased by the addition of histamine even at concentrations as low as 10(-6) M and peaking at 10(-3) M. These findings indicate that histamine exerts its anti-proliferative effects on T cells by inhibiting IL-2 production, via blockade of IL-2 gene expression. In addition, histamine seems to exert immunomodulating effects on IL-2 receptor expression, particularly in those individuals with AIDS-KS.

Induction of IL-6 (B cell stimulatory factor-2/IFN-beta 2) production by HIV

Polyclonal B cell activation is commonly observed in AIDS and in infection with HIV. The effect of HIV on the induction of B cell stimulatory factor 2 (BSF-2) production was examined, since BSF-2 plays an essential role in the differentiation of activated B cells to Ig-secreting cells. Increased BSF-2 mRNA levels and increased BSF-2 secretion were observed soon after exposure of mononuclear cells isolated from healthy donors to both "live" and inactivated HIV. HIV-induced BSF-2 production was seen in monocyte/macrophages, but not in T cells. These results suggest that the HIV-induced overproduction of BSF-2 might contribute to the polyclonal B cell activation seen in AIDS and in infection with HIV.

Induction of IL-6 (B cell stimulatory factor-2/IFN-beta 2) production by HIV

Polyclonal B cell activation is commonly observed in AIDS and in infection with HIV. The effect of HIV on the induction of B cell stimulatory factor 2 (BSF-2) production was examined, since BSF-2 plays an essential role in the differentiation of activated B cells to Ig-secreting cells. Increased BSF-2 mRNA levels and increased BSF-2 secretion were observed soon after exposure of mononuclear cells isolated from healthy donors to both "live" and inactivated HIV. HIV-induced BSF-2 production was seen in monocyte/macrophages, but not in T cells. These results suggest that the HIV-induced overproduction of BSF-2 might contribute to the polyclonal B cell activation seen in AIDS and in infection with HIV.

Reduced ecto-5'-nucleotidase activity and enhanced OKT10 and HLA-DR expression on CD8 (T suppressor/cytotoxic) lymphocytes in the acquired immune deficiency syndrome: evidence of CD8 cell immaturity

Markedly reduced ecto-5'-nucleotidase activity was found in peripheral blood lymphocytes from 27 out of 30 homosexual men with the acquired immune deficiency syndrome (AIDS) in association with Kaposi's sarcoma (AIDS-KS; 2.67 +/- 1.70 U/10(6) cells; n = 13), opportunistic infections (AIDS-OI; 9.29 +/- 7.32; n = 7), or the AIDS-related complex (ARC; 9.82 +/- 6.12; n = 10). These values were significantly different from healthy controls (22.70 +/- 4.58; p less than 0.001). In AIDS-KS patients, both T cells and non-T cells exhibited significantly reduced ecto-5'-NT activity (p less than 0.001). AIDS-KS CD8 cells contained 20% of the mean ecto-5'-NT activity (7.04 +/- 3.53) displayed by control CD8 cells (34.07 +/- 4.86; p less than 0.001). No significant difference in enzyme level was observed between control and AIDS-KS CD4 cells (11.93 +/- 4.98 vs 7.98 +/- 3.28, respectively). In AIDS patients, lymphocyte ecto-5'-NT activity was inversely related (r = -0.518; p less than 0.01) to the absolute number of OKT10+ cells, but no correlation was found with the number of HLA-DR+ cells (r =-0.224). Two-color analysis of lymphocytes from AIDS-KS patients revealed that 75 +/- 12% of circulating CD8 cells expressed the OKT10 antigen, whereas only 10 +/- 6% of control CD8 cells did. HLA-DR antigens, which are not normally found on circulating resting T cells, were expressed in AIDS-KS CD8 cells, although to a lesser extent than OKT10. These data demonstrate that most AIDS CD8 cells differ from control CD8 cells. Although it has been suggested that these cells are activated cytotoxic or suppressor cells, the data presented here support the hypothesis they are immature. Reduced T cell ecto-5'-NT activity and enhanced expression of OKT10 and HLA-DR antigens on circulating CD8 cells, in conjunction with lack of transferrin receptor-(OKT9) and IL 2 receptor-(Tac) bearing lymphocytes, sustain this latter hypothesis. The correlation of the numerical reduction of CD4 cells with the reduced levels of ecto-5'-NT (r = 0.606; p less than 0.01) suggests that the abnormal maturation of CD8 cells seen in AIDS might be a consequence of the CD4 deficiency characteristic of this syndrome.

Reduced ecto-5'-nucleotidase activity and enhanced OKT10 and HLA-DR expression on CD8 (T suppressor/cytotoxic) lymphocytes in the acquired immune deficiency syndrome: evidence of CD8 cell immaturity

Markedly reduced ecto-5'-nucleotidase activity was found in peripheral blood lymphocytes from 27 out of 30 homosexual men with the acquired immune deficiency syndrome (AIDS) in association with Kaposi's sarcoma (AIDS-KS; 2.67 +/- 1.70 U/10(6) cells; n = 13), opportunistic infections (AIDS-OI; 9.29 +/- 7.32; n = 7), or the AIDS-related complex (ARC; 9.82 +/- 6.12; n = 10). These values were significantly different from healthy controls (22.70 +/- 4.58; p less than 0.001). In AIDS-KS patients, both T cells and non-T cells exhibited significantly reduced ecto-5'-NT activity (p less than 0.001). AIDS-KS CD8 cells contained 20% of the mean ecto-5'-NT activity (7.04 +/- 3.53) displayed by control CD8 cells (34.07 +/- 4.86; p less than 0.001). No significant difference in enzyme level was observed between control and AIDS-KS CD4 cells (11.93 +/- 4.98 vs 7.98 +/- 3.28, respectively). In AIDS patients, lymphocyte ecto-5'-NT activity was inversely related (r = -0.518; p less than 0.01) to the absolute number of OKT10+ cells, but no correlation was found with the number of HLA-DR+ cells (r =-0.224). Two-color analysis of lymphocytes from AIDS-KS patients revealed that 75 +/- 12% of circulating CD8 cells expressed the OKT10 antigen, whereas only 10 +/- 6% of control CD8 cells did. HLA-DR antigens, which are not normally found on circulating resting T cells, were expressed in AIDS-KS CD8 cells, although to a lesser extent than OKT10. These data demonstrate that most AIDS CD8 cells differ from control CD8 cells. Although it has been suggested that these cells are activated cytotoxic or suppressor cells, the data presented here support the hypothesis they are immature. Reduced T cell ecto-5'-NT activity and enhanced expression of OKT10 and HLA-DR antigens on circulating CD8 cells, in conjunction with lack of transferrin receptor-(OKT9) and IL 2 receptor-(Tac) bearing lymphocytes, sustain this latter hypothesis. The correlation of the numerical reduction of CD4 cells with the reduced levels of ecto-5'-NT (r = 0.606; p less than 0.01) suggests that the abnormal maturation of CD8 cells seen in AIDS might be a consequence of the CD4 deficiency characteristic of this syndrome.