Expression of IFN-gamma induced CXCR3 agonist chemokines and compartmentalization of CXCR3+ cells in the periphery and lymph nodes of rhesus macaques during simian immunodeficiency virus infection and acquired immunodeficiency syndrome

Effect of HIV suppression on the cytokine network in blood and seminal plasma

OBJECTIVE

HIV infection disrupts the cytokine network and this disruption is not completely reversed by antiretroviral therapy (ART). Characterization of cytokine changes in blood and genital secretions is important for understanding HIV pathogenesis and the mechanisms of HIV sexual transmission. Here, we characterized the cytokine network in individuals longitudinally sampled before they began ART and after achieving suppression of HIV RNA.

METHODS

We measured concentrations of 34 cytokine/chemokines using multiplex bead-based assay in blood and seminal plasma of 19 men with HIV-1 prior to and after viral suppression. We used Partial Least Squares Discriminant Analysis (PLS-DA) to visualize the difference in cytokine pattern between the time points. Any cytokines with VIP scores exceeding 1 were deemed important in predicting suppression status and were subsequently tested using Wilcoxon Signed Rank Tests.

RESULTS

PLS-DA projections in blood were fairly similar before and after viral suppression. In contrast, the difference in PLS-DA projection observed in semen emphasizes that the immunological landscape and immunological needs are very different before and after ART in the male genital compartment. When tested individually, four cytokines were significantly different across time points in semen (MIG, IL-15, IL-7, I-TAC), and two in blood (MIG and IP-10).

CONCLUSION

Viral suppression with ART impacts the inflammatory milieu in seminal plasma. In contrast, the overall effect on the network of cytokines in blood was modest but consistent with prior analyses. These results identify specific changes in the cytokine networks in semen and blood as the immune system acclimates to chronic, suppressed HIV infection.

OAS Gene Family Expression Is Associated with HIV-Related Neurocognitive Disorders

HIV-associated neurocognitive disorders are common in HIV-infected individuals, even in the combination antiretroviral therapy (c-ART) era. Several mechanisms are involved in neuronal damage, including chronic inflammation immune activation. Mammalian 2'-5'-oligoadenylate synthetase (OAS) genes are produced in response to interferon (IFN), mainly by monocytes, and exert their antiviral functions by activation of RNase L that degrades viral and cellular RNAs. In this study, we aimed at exploring OAS gene family RNA expression in simian immunodeficiency virus encephalitis (SIVE), in HIV-associated neurocognitive disorders (HAND), and in HIV-associate dementia (HAD). We analyzed three microarray datasets obtained from the NCBI in order to assess the expression levels of OAS gene family network in brain biopsies of macaques with SIVE vs uninfected animals, as well as post-mortem brain of individuals with HAND (on or off ART) vs uninfected controls and three brain regions of HIV-infected individuals with both neurocognitive impairment (HAD) and encephalitis (HIVE). All OAS genes were upregulated both in SIVE and in HAND. OAS expression was significantly higher in high-viremic individuals; increased expression levels persisted in cART subjects when compared to healthy controls. OAS gene network analysis showed that several genes belonging to the type I IFN pathway, especially CXCL10 and IFIT3, were similarly upregulated in SIVE/HAND. Furthermore, we identified a significant upregulation of OAS gene family RNA expression in basal ganglia, white matter, and frontal cortex of HIV-1, HAD, and HAD/HIVE patients compared to healthy subjects. OAS gene family expression is increased in brain sections from individuals with HAND, HAD, and HIVE as well as macaques with SIVE. OAS family expression is likely to be induced by IFN as a consequence of viral replication in the CNS. Its long-term upregulation may contribute to the chronic inflammatory status and neurocognitive impairment we still observe in virologically suppressed individuals on c-ART.

Immune activation in HIV infection: what can the natural hosts of simian immunodeficiency virus teach us?

PURPOSE OF REVIEW

The review summarizes studies in natural hosts, with a particular focus on the control of immune activation and new insights into viral reservoirs. We discuss why these findings are relevant for HIV research today.

RECENT FINDINGS

AIDS resistance in natural hosts is characterized by a rapid control of inflammatory processes in response to simian immunodeficiency virus infection despite persistent viremia. Although CD4 T cells are dramatically depleted in the intestine in primary infection, interleukin 17-producing T helper cells (Th17) are preserved and natural hosts lack microbial translocation. Thus, viral replication in the gut is not sufficient to explain mucosal damage, but additional factors are necessary. Natural hosts also display a lower infection rate of stem-cell memory, central memory and follicular helper T cells. The follicles are characterized by a lack of viral trapping and the viral replication in secondary lymphoid organs is rapidly controlled. Hence, the healthy status of natural hosts is associated with preserved lymphoid environments.

SUMMARY

Understanding the underlying mechanisms of preservation of Th17 and of the low contribution of stem-cell memory, central memory and follicular helper T cells to viral reservoirs could benefit the search for preventive and curative approaches of HIV. Altogether, the complementarity of the model helps to identify strategies aiming at restoring full capacity of the immune system and decreasing the size of the viral reservoirs.

Chemokine-mediated immune responses in the female genital tract mucosa

The genital tract mucosa is the site where sexually transmitted infections gain entry to the host. The immune response at this site is thus critical to provide innate protection against pathogens that are seen for the very first time as well as provide long-term pathogen-specific immunity, which would be required for an effective vaccine against sexually transmitted infection. A finely regulated immune response is therefore required to provide an effective barrier against pathogens without compromising the capacity of the genital tract to allow for successful conception and fetal development. We review recent developments in our understanding of the immune response in the female genital tract to infectious pathogens, using herpes simplex virus-2, human immunodeficiency virus-1 and Chlamydia trachomatis as examples, with a particular focus on the role of chemokines in orchestrating immune cell migration necessary to achieve effective innate and adaptive immune responses in the female genital tract.

Acute plasma biomarkers of T cell activation set-point levels and of disease progression in HIV-1 infection

T cell activation levels, viral load and CD4(+) T cell counts at early stages of HIV-1 infection are predictive of the rate of progression towards AIDS. We evaluated whether the inflammatory profile during primary HIV-1 infection is predictive of the virological and immunological set-points and of disease progression. We quantified 28 plasma proteins during acute and post-acute HIV-1 infection in individuals with known disease progression profiles. Forty-six untreated patients, enrolled during primary HIV-1 infection, were categorized into rapid progressors, progressors and slow progressors according to their spontaneous progression profile over 42 months of follow-up. Already during primary infection, rapid progressors showed a higher number of increased plasma proteins than progressors or slow progressors. The plasma levels of TGF-β1 and IL-18 in primary HIV-1 infection were both positively associated with T cell activation level at set-point (6 months after acute infection) and together able to predict 74% of the T cell activation variation at set-point. Plasma IP-10 was positively and negatively associated with, respectively, T cell activation and CD4(+) T cell counts at set-point and capable to predict 30% of the CD4(+) T cell count variation at set-point. Moreover, plasma IP-10 levels during primary infection were predictive of rapid progression. In primary infection, IP-10 was an even better predictor of rapid disease progression than viremia or CD4(+) T cell levels at this time point. The superior predictive capacity of IP-10 was confirmed in an independent group of 88 HIV-1 infected individuals. Altogether, this study shows that the inflammatory profile in primary HIV-1 infection is associated with T cell activation levels and CD4(+) T cell counts at set-point. Plasma IP-10 levels were of strong predictive value for rapid disease progression. The data suggest IP-10 being an earlier marker of disease progression than CD4(+) T cell counts or viremia levels.

MIGRAs: are they the new IGRAs? Development of monokine-amplified IFN-γ release assays

IFN-γ release by antigen-specific T cells can be used to track immune responses to infections and vaccines. In recent years, there have been substantial advances in the techniques available to measure IFN-γ release and a generation of such assays are now available for clinical use, as well as in a research setting. Interferon release leads to subsequent release of interferon-responsive chemokines such as MIG and IP-10, thus amplifying the original signal. A number of investigators have assessed whether measurement of these chemokines might provide a sensitive platform for detection of infection and antigen-specific T-cell responses. In this article, we assess the potential of these new approaches. We have termed the new antigen-specific T-cell assays monokine-amplified IFN-γ release assays (MIGRAs). Overall, it seems likely that improvements in the detection threshold could be made by analysis of antigen-triggered chemokines and potentially of other molecules in the future, although whether MIGRAs will provide additional clinical utility still remains to be determined.

A plasma biomarker signature of immune activation in HIV patients on antiretroviral therapy

BACKGROUND

Immune activation is a strong predictor of disease progression in HIV infection. Combinatorial plasma biomarker signatures that represent surrogate markers of immune activation in both viremic and aviremic HIV patients on combination antiretroviral therapy (cART) have not been defined. Here, we identify a plasma inflammatory biomarker signature that distinguishes between both viremic and aviremic HIV patients on cART and healthy controls and examine relationships of this signature to markers of disease progression.

METHODS

Multiplex profiling and ELISA were used to detect 15 cytokines/chemokines, soluble IL-2R (sIL-2R), and soluble CD14 (sCD14) in plasma from 57 HIV patients with CD4 nadir <300 cells/µl and 29 healthy controls. Supervised and unsupervised analyses were used to identify biomarkers explaining variance between groups defined by HIV status or drug abuse. Relationships between biomarkers and disease markers were examined by Spearman correlation.

RESULTS

The majority (91%) of HIV subjects were on cART, with 38% having undetectable viral loads (VL). Hierarchical clustering identified a biomarker cluster in plasma consisting of two interferon-stimulated gene products (CXCL9 and CXCL10), T cell activation marker (sIL-2R), and monocyte activation marker (sCD14) that distinguished both viremic and aviremic HIV patients on cART from controls (p<0.0001) and were top-ranked in variables important in projection plots. IL-12 and CCL4 were also elevated in viremic and aviremic patients compared to controls (p<0.05). IL-12 correlated with IFNα, IFNγ, CXCL9, and sIL-2R (p<0.05). CXCL10 correlated positively with plasma VL and percentage of CD16+ monocytes, and inversely with CD4 count (p = 0.001, <0.0001, and 0.04, respectively).

CONCLUSION

A plasma inflammatory biomarker signature consisting of CXCL9, CXCL10, sIL-2R, and sCD14 may be useful as a surrogate marker to monitor immune activation in both viremic and aviremic HIV patients on cART during disease progression and therapeutic responses.

In acute pathogenic SIV infection plasmacytoid dendritic cells are depleted from blood and lymph nodes despite mobilization

Background  Plasmacytoid dendritic cells (pDC) are depleted from blood of individuals with HIV infection associated with progression to disease. It has been postulated but not proven that pDC accumulate in lymph nodes and induce sustained immune activation characteristic of disease.

Methods  The dynamics of the pDC response to acute pathogenic SIV infection of rhesus macaques were studied using methods to track recently divided cells.

Results  pDC were lost from blood and lymph nodes in acute SIV infection despite rapid mobilization and recruitment. pDC had a low frequency of infection, were uniformly activated and had increased levels of apoptosis, while maintaining normal function.

Conclusions  pDC mobilization into blood and lymph nodes in acute SIV infection does not keep pace with excessive pDC loss through activation and apoptosis. The depletion of pDC from lymphoid tissues in acutely infected rhesus macaques does not support a pathogenic role for pDC in disease.

Elevated levels of innate immune modulators in lymph nodes and blood are associated with more-rapid disease progression in simian immunodeficiency virus-infected monkeys

Cytokines and chemokines are critical for establishing tissue-specific immune responses and play key roles in modulating disease progression in simian immunodeficiency virus (SIV)-infected macaques and human immunodeficiency virus (HIV)-infected humans. The goal here was to characterize the innate immune response at different tissue sites and to correlate these responses to clinical outcome, initially focusing on rhesus macaques orally inoculated with SIV and monitored until onset of simian AIDS. Cytokine and chemokine mRNA transcripts were assessed at lymph nodes (LN) and peripheral blood cells utilizing quantitative real-time PCR at different time points postinfection. The mRNA expression of four immune modulators-alpha interferon (IFN-alpha), oligoadenylate synthetase (OAS), CXCL9, and CXCL10-was positively associated with disease progression within LN tissue. Elevated cytokine/chemokine expression in LN did not result in any observed beneficial outcome since the numbers of CXCR3(+) cells were not increased, nor were the SIV RNA levels decreased. In peripheral blood, increased OAS and CXCL10 expression were elevated in SIV(+) monkeys that progress the fastest to simian AIDS. Our results indicate that higher IFN-alpha, OAS, CXCL9, and CXCL10 mRNA expression in LN was associated with rapid disease progression and a LN environment that may favor SIV replication. Furthermore, higher expression of CXCL10 and OAS in peripheral blood could potentially serve as a diagnostic marker for hosts that are likely to progress to AIDS. Understanding the expression patterns of key innate immune modulators will be useful in assessing the disease state and potential rates of disease progression in HIV(+) patients, which could lead to novel therapy and vaccine approaches.

Rapid influx and death of plasmacytoid dendritic cells in lymph nodes mediate depletion in acute simian immunodeficiency virus infection

Plasmacytoid dendritic cells (pDC) are essential innate immune system cells that are lost from the circulation in human immunodeficiency virus (HIV)-infected individuals associated with CD4(+) T cell decline and disease progression. pDC depletion is thought to be caused by migration to tissues or cell death, although few studies have addressed this directly. We used precise methods of enumeration and in vivo labeling with 5-bromo-2'-deoxyuridine to track recently divided pDC in blood and tissue compartments of monkeys with acute pathogenic simian immunodeficiency virus (SIV) infection. We show that pDC are lost from blood and peripheral lymph nodes within 14 days of infection, despite a normal frequency of pDC in bone marrow. Paradoxically, pDC loss masked a highly dynamic response characterized by rapid pDC mobilization into blood and a 10- to 20-fold increase in recruitment to lymph nodes relative to uninfected animals. Within lymph nodes, pDC had increased levels of apoptosis and necrosis, were uniformly activated, and were infected at frequencies similar to CD4(+) T cells. Nevertheless, remaining pDC had essentially normal functional responses to stimulation through Toll-like receptor 7, with half of lymph node pDC producing both TNF-alpha and IFN-alpha. These findings reveal that cell migration and death both contribute to pDC depletion in acute SIV infection. We propose that the rapid recruitment of pDC to inflamed lymph nodes in lentivirus infection has a pathologic consequence, bringing cells into close contact with virus, virus-infected cells, and pro-apoptotic factors leading to pDC death.

Transcriptional profiling in pathogenic and non-pathogenic SIV infections reveals significant distinctions in kinetics and tissue compartmentalization

Simian immunodeficiency virus (SIV) infection leads to AIDS in experimentally infected macaques, whereas natural reservoir hosts exhibit limited disease and pathology. It is, however, unclear how natural hosts can sustain high viral loads, comparable to those observed in the pathogenic model, without developing severe disease. We performed transcriptional profiling on lymph node, blood, and colon samples from African green monkeys (natural host model) and Asian pigtailed macaques (pathogenic model) to directly compare gene expression patterns during acute pathogenic versus non-pathogenic SIV infection. The majority of gene expression changes that were unique to either model were detected in the lymph nodes at the time of peak viral load. Results suggest a shift toward cellular stress pathways and Th1 profiles during pathogenic infection, with strong and sustained type I and II interferon responses. In contrast, a strong type I interferon response was initially induced during non-pathogenic infection but resolved after peak viral load. The natural host also exhibited controlled Th1 profiles and better preservation of overall cell homeostasis. This study identified gene expression patterns that are specific to disease susceptibility, tissue compartmentalization, and infection duration. These patterns provide a unique view of how host responses differ depending upon lentiviral infection outcome.

Simian immunodeficiency virus (SIV) does not cause disease in African green monkeys (a natural host for the virus), whereas experimentally infected Asian macaques (a non-natural host) develop a progressive disease that is similar to that which occurs in HIV-infected humans. Insight into how HIV causes disease and leads to development of AIDS may therefore be gained by comparing the response of natural and non-natural hosts to SIV infection. To this end, we examined changes that occurred in gene expression levels over time and in multiple tissues derived from African green monkeys and Asian macaques experimentally infected with SIV. Infection leads to host-specific gene expression patterns in lymph nodes, blood, and colon. The natural and non-natural hosts differed with respect to the timing, intensity, and duration of infection-induced gene expression changes associated with inflammation and response to stress.

Multiple roles for chemokines in the pathogenesis of SIV infection

Chemokines are small chemoattractant cytokines involved in homeostatic and inflammatory immune cell migration. These small proteins have multiple functional properties that extend beyond their most recognized role in controlling cellular migration. The complex immunobiology of chemokines, coupled with the use of subsets of chemokine receptors as HIV-1 and SIV entry co-receptors, suggests that these immunomodulators could play important roles in the pathogenesis associated with infection by HIV-1 or SIV. This review provides an overview of the effects of pathogenic infection on chemokine expression in the SIV/macaque model system, and outlines potential mechanisms by which changes in these expression profiles could contribute to development of disease. Key challenges faced in studying chemokine function in vivo and new opportunities for further study and development of therapeutic interventions are discussed. Continued growth in our understanding of the effects of pathogenic SIV infection on chemokine expression and function and the continuing development of chemokine receptor targeted therapeutics will provide the tools and the systems necessary for future studies of the roles of chemokines in HIV-1 pathogenesis.

Personality and serotonin transporter genotype interact with social context to affect immunity and viral set-point in simian immunodeficiency virus disease

From the beginning of the AIDS epidemic, stress has been a suspected contributor to the wide variation seen in disease progression, and some evidence supports this idea. Not all individuals respond to a stressor in the same way, however, and little is known about the biological mechanisms by which variations in individuals' responses to their environment affect disease-relevant immunologic processes. Using the simian immunodeficiency virus/rhesus macaque model of AIDS, we explored how personality (Sociability) and genotype (serotonin transporter promoter) independently interact with social context (Stable or Unstable social conditions) to influence behavioral expression, plasma cortisol concentrations, SIV-specific IgG, and expression of genes associated with Type I interferon early in infection. SIV viral RNA set-point was strongly and negatively correlated with survival as expected. Set-point was also associated with expression of interferon-stimulated genes, with CXCR3 expression, and with SIV-specific IgG titers. Poorer immune responses, in turn, were associated with display of sustained aggression and submission. Personality and genotype acted independently as well as in interaction with social condition to affect behavioral responses. Together, the data support an "interactionist" perspective [Eysenck, H.J., 1991. Personality, stress and disease: an interactionist perspective. Psychol. Inquiry 2, 221-232] on disease. Given that an important goal of HIV treatment is to maintain viral set-point as low as possible, our data suggest that supplementing anti-retroviral therapy with behavioral or pharmacologic modulation of other aspects of an organism's functioning might prolong survival, particularly among individuals living under conditions of threat or uncertainty.

Decreased CXCR3+ CD8 T cells in advanced human immunodeficiency virus infection suggest that a homing defect contributes to cytotoxic T-lymphocyte dysfunction

To exert their cytotoxic function, cytotoxic T-lymphocytes (CTL) must be recruited into infected lymphoid tissue where the majority of human immunodeficiency virus (HIV) replication occurs. Normally, effector T cells exit lymph nodes (LNs) and home to peripheral sites of infection. How HIV-specific CTL migrate into lymphoid tissue from which they are normally excluded is unknown. We investigated which chemokines and receptors mediate this reverse homing and whether impairment of this homing could contribute to CTL dysfunction as HIV infection progresses. Analysis of CTL chemokine receptor expression in the blood and LNs of untreated HIV-infected individuals with stable, chronic infection or advanced disease demonstrated that LNs were enriched for CXCR3(+) CD8 T cells in all subjects, suggesting a key role for this receptor in CTL homing to infected lymphoid tissue. Compared to subjects with chronic infection, however, subjects with advanced disease had fewer CXCR3(+) CD8 T cells in blood and LNs. CXCR3 expression on bulk and HIV-specific CD8 T cells correlated positively with CD4 count and negatively with viral load. In advanced infection, there was an accumulation of HIV-specific CD8 T cells at the effector memory stage; however, decreased numbers of CXCR3(+) CD8 T cells were seen across all maturation subsets. Plasma CXCL9 and CXCL10 were elevated in both infected groups in comparison to the levels in uninfected controls, whereas lower mRNA levels of CXCR3 ligands and CD8 in LNs were seen in advanced infection. These data suggest that both CXCR3(+) CD8 T cells and LN CXCR3 ligands decrease as HIV infection progresses, resulting in reduced homing of CTL into LNs and contributing to immune dysfunction.

Mucosal innate immune response associated with a timely humoral immune response and slower disease progression after oral transmission of simian immunodeficiency virus to rhesus macaques

Mucosal transmission is the predominant mode of human immunodeficiency virus (HIV) infection worldwide, and the mucosal innate interferon response represents an important component of the earliest host response to the infection. Our goal here was to assess the changes in mRNA expression of innate mucosal genes after oral simian immunodeficiency virus (SIV) inoculation of rhesus macaques (Macaca mulatta) that were followed throughout their course of disease progression. The SIV plasma viral load was highest in the macaque that progressed rapidly to simian AIDS (99 days) and lowest in the macaque that progressed more slowly (>700 days). The mRNA levels of six innate/effector genes in the oral mucosa indicated that slower disease progression was associated with increased expression of these genes. This distinction was most evident when comparing the slowest-progressing macaque to the intermediate and rapid progressors. Expression levels of alpha and gamma interferons, the antiviral interferon-stimulated gene product 2'-5' oligoadenylate synthetase (OAS), and the chemokines CXCL9 and CXCL10 in the slow progressor were elevated at each of the three oral mucosal biopsy time points examined (day 2 to 4, 14 to 21, and day 70 postinfection). In contrast, the more rapidly progressing macaques demonstrated elevated levels of these cytokine/chemokine mRNA at lymph nodes, coincident with decreased levels at the mucosal sites, and a decreased ability to elicit an effective anti-SIV antibody response. These data provide evidence that a robust mucosal innate/effector immune response is beneficial following lentiviral exposure; however, it is likely that the anatomical location and timing of the response need to be coordinated to permit an effective immune response able to delay progression to simian AIDS.

Proteomic analysis of serum cytokine levels in response to highly active antiretroviral therapy (HAART)

A 30-cytokine protein microarray was used to screen for cytokine profile changes in HIV-infected patients in response to highly active antiretroviral therapy (HAART). Serum cytokines showing significant changes were confirmed by enzyme immunoassay. Monokine induced by gamma-interferon (MIG) and interferon-inducible protein-10 (IP-10) levels significantly decreased after 24 weeks of HAART. Protein microarrays are useful for initial screening of novel cytokine expression. Further studies are needed to elucidate the role of MIG and IP-10 in response to HAART.

A tumor necrosis factor receptor family protein serves as a cellular receptor for the macrophage-tropic equine lentivirus

Characterization of cellular receptors for human, simian, and feline immunodeficiency viruses that are tropic for lymphocytes and macrophages have revealed a common theme of a sequential binding of viral envelope proteins with two coreceptors to mediate virus infection of target cells. In contrast to these dual tropic immunodeficiency viruses, the ungulate lentiviruses, including equine infectious anemia virus (EIAV), exclusively infect cells of the monocyte-macrophage lineage to cause progressive degenerative diseases without clinical immunodeficiency. EIAV causes a uniquely dynamic disease that is characterized by recurrent disease episodes including fever, diarrhea, lethargy, anemia, and thrombocytopenia. Although EIAV provides an important animal model for lentivirus disease resulting from macrophage infection, to date there has been no definition of the specific cellular receptor(s) used by the equine lentivirus to infect target cells. In the current study, we have identified and cloned a functional receptor for EIAV, designated equine lentivirus receptor-1 (ELR1), related to the family of TNF receptor (TNFR) proteins. ELR1 was shown to be expressed in various equine cells permissive for EIAV replication in vitro, including monocytes and macrophages. In contrast, EIAV-resistant human, murine, and simian cells were negative for ELR1 expression but became susceptible to virus infection when transduced with a recombinant murine retrovirus expressing the ELR1. Thus, these results identify a specific functional receptor for a macrophagetropic lentivirus and indicate that infection by EIAV may be mediated by a single receptor, in contrast to coreceptors used by the lymphotropic immunodeficiency lentiviruses.