Increased expression of the inflammatory chemokine CXC chemokine ligand 9/monokine induced by interferon-gamma in lymphoid tissues of rhesus macaques during simian immunodeficiency virus infection and acquired immunodeficiency syndrome

Cytolytic CD8+ T cells infiltrate germinal centers to limit ongoing HIV replication in spontaneous controller lymph nodes

Follicular CD8⁺ T cells (fCD8) mediate surveillance in lymph node (LN) germinal centers against lymphotropic infections and cancers, but the precise mechanisms by which these cells mediate immune control remain incompletely resolved. To address this, we investigated functionality, clonotypic compartmentalization, spatial localization, phenotypic characteristics, and transcriptional profiles of LN-resident virus-specific CD8⁺ T cells in persons who control HIV without medications. Antigen-induced proliferative and cytolytic potential consistently distinguished spontaneous controllers from noncontrollers. T cell receptor analysis revealed complete clonotypic overlap between peripheral and LN-resident HIV-specific CD8⁺ T cells. Transcriptional analysis of LN CD8⁺ T cells revealed gene signatures of inflammatory chemotaxis and antigen-induced effector function. In HIV controllers, the cytotoxic effectors perforin and granzyme B were elevated among virus-specific CXCR5⁺ fCD8s proximate to foci of HIV RNA within germinal centers. These results provide evidence consistent with cytolytic control of lymphotropic infection supported by inflammatory recruitment, antigen-specific proliferation, and cytotoxicity of fCD8s.

Jigsaw falling into place: A review and perspective of lymphoid tissue CD8+ T cells and control of HIV

CD8+ T cells are crucial for immunity against viral infections, including HIV. Several characteristics of CD8+ T cells, such as polyfunctionality and cytotoxicity, have been correlated with effective control of HIV. However, most of these correlates have been established in the peripheral blood. Meanwhile, HIV primarily replicates in lymphoid tissues. Therefore, it is unclear which aspects of CD8+ T cell biology are shared and which are different between blood and lymphoid tissues in the context of HIV infection. In this review, we will recapitulate the latest advancements of our knowledge on lymphoid tissue CD8+ T cells during HIV infection and discuss the insights these advancements might provide for the development of a HIV cure.

Resistance of HIV-infected macrophages to CD8+ T lymphocyte-mediated killing drives activation of the immune system

CD4⁺ T lymphocytes are the principal target of human immunodeficiency virus (HIV), but infected macrophages also contribute to viral pathogenesis. The killing of infected cells by CD8⁺ cytotoxic T lymphocytes (CTLs) leads to control of viral replication. Here we found that the killing of macrophages by CTLs was impaired relative to the killing of CD4⁺ T cells by CTLs, and this resulted in inefficient suppression of HIV. The killing of macrophages depended on caspase-3 and granzyme B, whereas the rapid killing of CD4⁺ T cells was caspase independent and did not require granzyme B. Moreover, the impaired killing of macrophages was associated with prolonged effector cell-target cell contact time and higher expression of interferon-γ by CTLs, which induced macrophage production of pro-inflammatory chemokines that recruited monocytes and T cells. Similar results were obtained when macrophages presented other viral antigens, suggestive of a general mechanism for macrophage persistence as antigen-presenting cells that enhance inflammation and adaptive immunity. Inefficient killing of macrophages by CTLs might contribute to chronic inflammation, a hallmark of chronic disease caused by HIV.

Mechanisms regulating expansion of CD8+ T cells during HIV-1 infection

Abnormal immune activation and expansion of CD8+ T cells, especially of memory and effector phenotypes, take place during HIV-1 infection, and these abnormal features persist during administration of antiretroviral therapy (ART) to infected patients. The molecular mechanisms for CD8+ T-cell expansion remain poorly characterized. In this article, we review the literature addressing features of CD8+ T-cell immune pathology and present an integrated view on the mechanisms leading to abnormal CD8+ T-cell expansion during HIV-1 infection. The expression of molecules important for directing the homing of CD8+ T cells between the circulation and lymphoid tissues, in particular CCR5 and CXCR3, is increased in CD8+ T cells in circulation and in inflamed tissues during HIV-1 infection; these disturbances in the homing capacity of CD8+ T cells have been linked to increased CD8+ T-cell proliferation. The production of IL-15, a cytokine responsible for physiological proliferation of CD8+ T cells, is increased in lymphoid tissues during HIV-1 infection as result of microbial translocation and severe inflammation. IL-15, and additional inflammatory cytokines, may lead to deregulated proliferation of CD8+ T cells and explain the accumulation of CD8+ T cells in circulation. The decreased capacity of CD8+ T cells to localize to gut-associated lymphoid tissue also contributes to the accumulation of these cells in blood. Control of inflammation, through ART administration during primary HIV-1 infection or therapies aimed at controlling inflammation during HIV-1 infection, is pivotal to prevent abnormal expansion of CD8+ T cells during HIV-1 infection.

Distribution of 5-HT1F Receptors in Monkey Vestibular and Trigeminal Ganglion Cells

Background

Evidence of serotonergic involvement in vestibular pathway contributions to migraine and balance disorders is compelling. Serotonergic 5-HT_1B and 5-HT_1D receptors are expressed extensively in inner ear ganglia of monkeys and rats. The serotonergic 5-HT_1F receptor is also a target of triptans. This study describes its distribution in vestibular and trigeminal ganglia of monkeys.

Methods

Using primary polyclonal antibodies raised against oligopeptides specific for the human 5-HT_1F receptor, neuronal somatic area and intensity of immunoreactive vestibular and trigeminal ganglia were quantified.

Results and Discussion

Virtually all vestibular and considerable trigeminal ganglia showed positive 5-HT_1F receptor immunoreactivity. Inferior and superior vestibular ganglia staining appeared confined to distinct cell regions, varying considerably among cells of different sizes: more intense in small, punctate in some medium and regionally polarized in some large cells. Analyses of average somatic vestibular neuronal immunoreactive intensity identified mainly medium sized cells with high standard deviation of intensity corresponding to punctately stained cells. Less variability occurred in somatic intensity staining and cellular distribution among 5-HT_1F receptor immunopositive trigeminal ganglia. Most exhibited similar punctate staining patterns, higher mean somatic immunoreactive intensity and larger neuronal somatic size proportions per size distribution subpopulation compared to vestibular ganglia size distribution populations. Centrally directed vestibular ganglion neuronal processes, cochlear inner hair cells, vestibular hair cells and blood vessels in vestibular maculae and cristae were immunoreactive. The 5-HT_1F receptor expression in vestibular ganglia shows complex variable staining intensity patterns associated with cell size of immunopositive neurons, not seen in immunopositive trigeminal ganglia and not previously evident with 5-HT_1B and 5-HT_1D receptor subtype immunoreactivity in vestibular ganglia. These data motivate exploration of 5-HT₁ receptor oligomerization and ligand functional selectivity in differential serotonergic involvement in co-morbidity of migraine and balance disorders. Similar findings in cochlear inner hair cell afferents are applicable to migraine-related tinnitus or hypercusis (phonophobia).

Elevated Basal Pre-infection CXCL10 in Plasma and in the Small Intestine after Infection Are Associated with More Rapid HIV/SIV Disease Onset

Elevated blood CXCL10/IP-10 levels during primary HIV-1 infection (PHI) were described as an independent marker of rapid disease onset, more robust than peak viremia or CD4 cell nadir. IP-10 enhances the recruitment of CXCR3+ cells, which include major HIV-target cells, raising the question if it promotes the establishment of viral reservoirs. We analyzed data from four cohorts of HIV+ patients, allowing us to study IP-10 levels before infection (Amsterdam cohort), as well as during controlled and uncontrolled viremia (ANRS cohorts). We also addressed IP-10 expression levels with regards to lymphoid tissues (LT) and blood viral reservoirs in patients and non-human primates. Pre-existing elevated IP-10 levels but not sCD63 associated with rapid CD4 T-cell loss upon HIV-1 infection. During PHI, IP-10 levels and to a lesser level IL-18 correlated with cell-associated HIV DNA, while 26 other inflammatory soluble markers did not. IP-10 levels tended to differ between HIV controllers with detectable and undetectable viremia. IP-10 was increased in SIV-exposed aviremic macaques with detectable SIV DNA in tissues. IP-10 mRNA was produced at higher levels in the small intestine than in colon or rectum. Jejunal IP-10+ cells corresponded to numerous small and round CD68neg cells as well as to macrophages. Blood IP-10 response negatively correlated with RORC (Th17 marker) gene expression in the small intestine. CXCR3 expression was higher on memory CD4+ T cells than any other immune cells. CD4 T cells from chronically infected animals expressed extremely high levels of intra-cellular CXCR3 suggesting internalization after ligand recognition. Elevated systemic IP-10 levels before infection associated with rapid disease progression. Systemic IP-10 during PHI correlated with HIV DNA. IP-10 production was regionalized in the intestine during early SIV infection and CD68+ and CD68neg haematopoietic cells in the small intestine appeared to be the major source of IP-10.

Chronic immune activation is a hallmark of HIV infection and contributes in multiple ways to HIV persistence. Here, we gained insights on the association between a pro-inflammatory chemokine, CXCL10/IP-10 and HIV infection in four cohorts of HIV+ individuals, studied at distinct stages of infection (before, primary and chronic stage with spontaneous- and treatment-controlled infection). We further analyzed pathogenic and non-pathogenic SIV infections to address IP-10 levels and the presence of infected cells in tissues (lymph nodes, small and large intestine). We found that elevated systemic IP-10 levels before HIV-1 infection associate with a more rapid disease progression. During primary infection, IP-10 in blood strongly correlated with the amount of infected cells in blood. The animal model showed that IP-10 expression was regionalized in the intestine and highest in the small intestine. Studies of aviremic animals suggest that high IP-10 is indicative of viral replication in lymphoid tissues. Haematopoietic cells rather than epithelial/endothelial cells mainly contributed to the IP-10 production in small intestine (jejunum). The receptor of IP-10 was highly expressed on memory CD4+ T cells, i.e. major target cells for the virus. This study contributes to our understanding of the establishment of HIV reservoirs and why IP-10 associates with HIV/AIDS.

Chemokine, cytokine and type I interferon production induced by Toll-like receptor activation in common variable immune deficiency

Common variable immunodeficiency (CVID) is the most common symptomatic primary antibody deficiency and is associated with recurrent infections and chronic inflammatory diseases. We evaluated the ability of Toll-like receptor (TLR) ligands to induce secretion of chemokines, cytokines and type I interferons by peripheral blood mononuclear cells (PBMCs) from CVID patients. High levels of CXCL10, CCL2, CXCL9, CCL5, CXCL8, and IL-6 were detected in sera of CVID patients compared with healthy controls. Increased chemokine levels were observed in unstimulated PBMCs, but after stimulation with TLR2 and TLR4 agonists, equivalent chemokine and pro-inflammatory cytokine secretion, as in healthy controls, was observed, whereas TLR4 agonist induced a decreased secretion of CCL2 and CXCL8 and increased secretion of TNF. Decreased IFN-α secretion induced by TLR7/TLR8 activation was observed in CVID, which was recovered with TLR9 signaling. Our findings revealed that TLR9 activation has an adjuvant effect on the altered type I response in CVID.

Compartment-specific and sequential role of MyD88 and CARD9 in chemokine induction and innate defense during respiratory fungal infection

Aspergillus fumigatus forms ubiquitous airborne conidia that humans inhale on a daily basis. Although respiratory fungal infection activates the adaptor proteins CARD9 and MyD88 via C-type lectin, Toll-like, and interleukin-1 family receptor signals, defining the temporal and spatial pattern of MyD88- and CARD9-coupled signals in immune activation and fungal clearance has been difficult to achieve. Herein, we demonstrate that MyD88 and CARD9 act in two discrete phases and in two cellular compartments to direct chemokine- and neutrophil-dependent host defense. The first phase depends on MyD88 signaling because genetic deletion of MyD88 leads to delayed induction of the neutrophil chemokines CXCL1 and CXCL5, delayed neutrophil lung trafficking, and fatal pulmonary damage at the onset of respiratory fungal infection. MyD88 expression in lung epithelial cells restores rapid chemokine induction and neutrophil recruitment via interleukin-1 receptor signaling. Exogenous CXCL1 administration reverses murine mortality in MyD88-deficient mice. The second phase depends predominately on CARD9 signaling because genetic deletion of CARD9 in radiosensitive hematopoietic cells interrupts CXCL1 and CXCL2 production and lung neutrophil recruitment beyond the initial MyD88-dependent phase. Using a CXCL2 reporter mouse, we show that lung-infiltrating neutrophils represent the major cellular source of CXCL2 during CARD9-dependent recruitment. Although neutrophil-intrinsic MyD88 and CARD9 function are dispensable for neutrophil conidial uptake and killing in the lung, global deletion of both adaptor proteins triggers rapidly progressive invasive disease when mice are challenged with an inoculum that is sub-lethal for single adapter protein knockout mice. Our findings demonstrate that distinct signal transduction pathways in the respiratory epithelium and hematopoietic compartment partially overlap to ensure optimal chemokine induction, neutrophil recruitment, and fungal clearance within the respiratory tract.

Our understanding of how epithelial and hematopoietic cells in the lung coordinate immunity against inhaled fungal conidia (spores) remains limited. The mold Aspergillus fumigatus is a major cause of infectious mortality in immune compromised patients. Host defense against A. fumigatus involves the activation of two host signal transducers, MyD88 and CARD9, leading to neutrophil recruitment to the infection site. In this study, we define how MyD88- and CARD9-coupled signals operate in epithelial and hematopoietic compartments to regulate neutrophil-mediated defense against A. fumigatus. Our studies support a two-stage model in which MyD88 activation in epithelial cells, via the interleukin-1 receptor, supports the rapid induction of neutrophil-recruiting chemokines. This process is essential for the first phase of neutrophil recruitment. Mortality observed in MyD88-deficient mice can be significantly reversed by administration of a chemokine termed CXCL1 to infected airways. The second phase of neutrophil recruitment is initiated by CARD9 signaling in hematopoietic cells. Loss of both phases of chemokine induction and neutrophil recruitment dramatically increases murine susceptibility to tissue-invasive disease. In sum, our study defines a temporal sequence of events, initiated by interleukin-1 receptor/MyD88 signaling in the pulmonary epithelium and propagated by CARD9 signaling in hematopoietic cells, that induces protective immunity against inhaled fungal conidia.

Infection with host-range mutant adenovirus 5 suppresses innate immunity and induces systemic CD4+ T cell activation in rhesus macaques

Ad5 is a common cause of respiratory disease and an occasional cause of gastroenteritis and conjunctivitis, and seroconversion before adolescence is common in humans. To gain some insight into how Ad5 infection affects the immune system of rhesus macaques (RM) 18 RM were infected with a host-range mutant Ad5 (Ad5hr) by 3 mucosal inoculations. There was a delay of 2 to 6 weeks after the first inoculation before plasmacytoid dendritic cell (pDC) frequency and function increased in peripheral blood. Primary Ad5hr infection suppressed IFN-γ mRNA expression, but the second Ad5hr exposure induced a rapid increase in IFN-gamma mRNA in peripheral blood mononuclear cells (PBMC). Primary Ad5hr infection suppressed CCL20, TNF and IL-1 mRNA expression in PBMC, and subsequent virus exposures further dampened expression of these pro-inflammatory cytokines. Primary, but not secondary, Ad5hr inoculation increased the frequency of CXCR3+ CD4+ T cells in blood, while secondary, but not primary, Ad5hr infection transiently increased the frequencies of Ki67+, HLADR+ and CD95+/CCR5+ CD4+ T cells in blood. Ad5hr infection induced polyfunctional CD4 and CD8+ T cells specific for the Ad5 hexon protein in all of the animals. Thus, infection with Ad5hr induced a complex pattern of innate and adaptive immunity in RM that included transient systemic CD4+ T cell activation and suppressed innate immunity on re-exposure to the virus. The complex effects of adenovirus infection on the immune system may help to explain the unexpected results of testing Ad5 vector expressing HIV antigens in Ad5 seropositive people.

Cytokine/Chemokine responses in activated CD4+ and CD8+ T cells isolated from peripheral blood, bone marrow, and axillary lymph nodes during acute simian immunodeficiency virus infection

Understanding the cytokine/chemokine networks in CD4(+) and CD8(+) T cells during the acute phase of infection is crucial to design therapies for the control of early human immunodeficiency virus (HIV)/simian immunodeficiency virus (SIV) replication. Here, we measured early changes in CD4(+) and CD8(+) T cells in the peripheral blood (PB), bone marrow (BM), and axillary lymph node (ALN) tissue of rhesus macaques infected with SIVMAC251. At 21 days after infection, all tissues showed a statistically significant loss of CD4(+) T cells along with immune activation of CD8(+) T cells in PB and ALN tissue. Twenty-eight different cytokines/chemokines were quantified in either anti-CD3/28 antibody- or staphylococcal enterotoxin B-stimulated single-positive CD4(+) and CD8(+) T cells. PB CD4(+) T cells produced predominantly interleukin-2 (IL-2), whereas CD4(+) and CD8(+) T-cell subsets in tissues produced β-chemokines both before and 21 days after SIV infection. Tissues generally exhibited massive upregulation of many cytokines/chemokines following infection, possibly in an attempt to mitigate the loss of CD4(+) T cells. There was no evidence of a T-helper 1 (TH1)-to-TH2 shift in CD4(+) T cells or a T-cytotoxic 1 (TC1)-to-TC2 cytokine shift in CD8(+) T cells in PB, BM, and ALN T-cell subsets during the acute phase of SIV infection. Despite the upregulation of several important effector cytokines/chemokines (IL-2, IL-12, IL-17, gamma interferon, granulocyte-macrophage colony-stimulating factor) by CD4(+) and CD8(+) T cells, upregulation of β-chemokines (CCL2 and CCL22), basic fibroblast growth factor (FGF-basic), hepatocyte growth factor (HGF), and migration inhibition factor (MIF) may provide a poor prognosis either by inducing increased virus replication or by other unknown mechanisms. Therefore, drugs targeting β-chemokines (CCL2 and CCL22), FGF-basic, HGF, or MIF might be important for developing effective vaccines and therapeutics against HIV.

IMPORTANCE

Human immunodeficiency virus (HIV)/simian immunodeficiency virus (SIV) infection results in early depletion of CD4(+) T cells and dysregulation of protective immune responses. Therefore, understanding the cytokine/chemokine networks in CD4(+) and CD8(+) T cells in different tissues during the acute phase of infection is crucial to the design of therapies for the control of early viral replication. Here, we measured early changes in CD4(+) and CD8(+) T cells in peripheral blood (PB), bone marrow (BM), and axillary lymph node (ALN) tissue of rhesus macaques infected with SIVMAC251. There was no evidence of a T-helper 1 (TH1)-to-TH2 shift in CD4(+) T cells or a T-cytotoxic 1 (TC1)-to-TC2 cytokine shift in CD8(+) T cells in PB, BM, and ALN T-cell subsets during the acute phase of SIV infection. Despite the upregulation of several important effector cytokines/chemokines by CD4(+) and CD8(+) T cells, upregulation of β-chemokines, fibroblast growth factor-basic, hepatocyte growth factor, and migration inhibition factor may provide a poor prognosis.

Massive mobilization of dendritic cells during influenza A virus subtype H5N1 infection of nonhuman primates

Highly pathogenic avian influenza virus infection is characterized by a marked inflammatory response, but the impact of infection on dendritic cells (DCs) is unknown. We show that influenza A virus subtype H5N1 infection rapidly and profoundly impacts DCs in cynomolgus macaques, increasing the number of blood myeloid and plasmacytoid DCs by 16- and 60-fold, respectively. Infection was associated with recruitment, activation, and apoptosis of DCs in lung-draining lymph nodes; granulocyte and macrophage infiltration in lungs was also detected, together with expression of CXCL10. This degree of DC mobilization is unprecedented in viral infection and suggests a potential role for DCs in the pathogenesis of highly pathogenic avian influenza virus.

Simian immunodeficiency virus infection potently modulates chemokine networks and immune environments in hilar lymph nodes of cynomolgus macaques

BACKGROUND

Chemokines provide critical immune cell homing and activation signals that if altered could affect the inflammatory milieu and cellular composition of lymphoid tissues. During HIV-1 and simian immunodeficiency virus (SIV)-infection, the virus triggers an increase in inflammation or activation, leading to immunodeficiency and development of opportunistic infections, such as in the lungs-a massive interface between the host and the environment.

METHODS

Chemokine, cytokine, and chemokine receptor expression profiles were determined using real-time reverse transcriptase-polymerase chain reaction and in situ hybridization in hilar lymph nodes (HiLNs) from cynomolgus macaques at different stages after infection with SIV/DeltaB670. Immunostaining of tissue sections and flow cytometric analysis of cryopreserved cells were used to examine cellular compositions of lymph nodes.

RESULTS

Interferon-gamma, type 1 chemokine, and cognate chemokine receptor mRNAs were upregulated, whereas type 2 and homeostatic chemokine and chemokine receptor mRNAs were down-regulated in HiLNs after SIV infection. Local SIV and interferon-gamma levels were positively correlated with type 1 chemokine levels but negatively correlated with type 2 and homeostatic chemokine levels. Using in situ hybridization, Pneumocystis carinii rRNA was detected in lung-draining lymph nodes from animals with P. carinii pneumonia. Changes in the cellular composition of HiLNs included decreased proportions of CD4 cells and dendritic cells and increased proportions of CD8, CXCR3, and CCR5 cells.

CONCLUSIONS

SIV infection of cynomolgus macaques dramatically alters the cellular homing signals of lung-draining lymph nodes, which correlated with changes in the immune cellular composition. These changes could contribute to the loss of immune function that defines AIDS.

Macaque paneth cells express lymphoid chemokine CXCL13 and other antimicrobial peptides not previously described as expressed in intestinal crypts

CXCL13 is a constitutively expressed chemokine that controls migration of immune cells to lymphoid follicles. Previously, we found CXCL13 mRNA levels increased in rhesus macaque spleen tissues during AIDS. This led us to examine the levels and locations of CXCL13 by detailed in situ methods in cynomolgus macaque lymphoid and intestinal tissues. Our results revealed that there were distinct localization patterns of CXCL13 mRNA compared to protein in germinal centers. These patterns shifted during the course of simian immunodeficiency virus (SIV) infection, with increased mRNA expression within and around follicles during AIDS compared to uninfected or acutely infected animals. Unexpectedly, CXCL13 expression was also found in abundance in Paneth cells in crypts throughout the small intestine. Therefore, we expanded our analyses to include chemokines and antimicrobial peptides (AMPs) not previously demonstrated to be expressed by Paneth cells in intestinal tissues. We examined the expression patterns of multiple chemokines, including CCL25, as well as α-defensin 6 (DEFA6), β-defensin 2 (BDEF2), rhesus θ-defensin 1 (RTD-1), and Reg3γ in situ in intestinal tissues. Of the 10 chemokines examined, CXCL13 was unique in its expression by Paneth cells. BDEF2, RTD-1, and Reg3γ were also expressed by Paneth cells. BDEF2 and RTD-1 previously have not been shown to be expressed by Paneth cells. These findings expand our understanding of mucosal immunology, innate antimicrobial defenses, homeostatic chemokine function, and host protective mechanisms against microbial translocation.

Innate Stat3-mediated induction of the antimicrobial protein Reg3γ is required for host defense against MRSA pneumonia

STAT3-mediated induction of Reg3γ enhances bacteriostatic and bactericidal activity to pulmonary Staphylococcus aureus.

Pulmonary Staphylococcus aureus (SA) infections are a public health concern and a major complication of hyper-IgE syndrome, caused by mutations in STAT3. In contrast to previous findings of skin infection, we observed that clearance of SA from the lung did not require T, B, or NK cells but did require Stat3 activation. Immunohistochemistry showed robust Stat3 phosphorylation in the lung epithelium. We identified that a critical Stat3 target gene in lung epithelium is Reg3g (regenerating islet-derived 3 γ), a gene which is highly expressed in gastrointestinal epithelium but whose role in pulmonary host defense is uncharacterized. Stat3 regulated Reg3g transcription through direct binding at the Reg3g promoter region. Recombinant Reg3γ bound to SA and had both bacteriostatic and bactericidal activity in a dose-dependent fashion. Stat3 inhibition in vivo reduced Reg3g transcripts in the lung, and more importantly, recombinant Reg3γ rescued mice from defective SA clearance. These findings reveal an antibacterial function for lung epithelium through Stat3-mediated induction of Reg3γ.

Effect of early anti-retroviral therapy on the pathogenic changes in mucosal tissues of SIV infected rhesus macaques

BACKGROUND

The gastrointestinal tissue plays an important role in the pathogenesis of HIV/SIV infection and serves as a viral reservoir in infected individuals under antiretroviral therapy (ART). However, the effect of ART administration in the very early stage of infection on HIV/SIV replication and pathogenesis in gastrointestinal tissue has not been fully studied. In this current study, rhesus monkeys infected with SIV were treated with ART starting at day 7 post-infection. The effect of early ART on SIV replication and infection-related pathogenic changes in mucosal tissues of the infected monkeys was examined.

METHODS

Nuclear acids were extracted from snap frozen ileum and colon tissues and mesentery lymph nodes from SIV infected monkeys with or without ART. SIV RNA and DNA loads as well as levels of CD3, CD4 and cytokine mRNA were measured by PCR and RT PCR from the isolated nuclear acids. Tissue sections were stained by immuno-fluorescence labeled antibodies for CD3 and CD4.

RESULTS

Without ART treatment, these monkeys underwent a mild SIV infection with low viral loads and slightly decreased CD4+ T cell counts in peripheral blood. In ART treated monkeys, SIV RNA loads were undetectable in blood with normal CD4+ T cell counts, however, SIV RNA and DNA were detected in the intestinal tissues and mesentery lymph nodes although the levels were lower than those in untreated monkeys. The levels of CD3 and CD4 positive cells in the tissues were similar between the infected untreated monkeys and infected ART treated monkeys based on RT-PCR and immune-fluorescence staining of the tissue sections. Furthermore, compatible levels of IL-6, TNF-a, IL-1b and MyD88 mRNAs were detected in most of intestinal tissues and mesentery lymph nodes of infected ART treated and infected untreated monkeys.

CONCLUSIONS

These results suggest that early ART administration could not effectively inhibit SIV replication in intestinal tissues and mesentery lymph nodes and could not reduce the immune activation induced by SIV infection in the intestinal tissues.

Age-related changes in expression and function of Toll-like receptors in human skin

Toll-like receptors (TLRs) initiate innate immune responses and direct subsequent adaptive immunity. They play a major role in cutaneous host defense against micro-organisms and in the pathophysiology of several inflammatory skin diseases. To understand the role of TLRs in the acquisition of immunological competence, we conducted a comprehensive study to evaluate TLR expression and function in the developing human skin before and after birth and compared it with adults. We found that prenatal skin already expresses the same spectrum of TLRs as adult skin. Strikingly, many TLRs were significantly higher expressed in prenatal (TLRs 1-5) and infant and child (TLRs 1 and 3) skin than in adult skin. Surprisingly, neither dendritic cell precursors in prenatal skin nor epidermal Langerhans cells and dermal dendritic cells in adult skin expressed TLRs 3 and 6, whereas the staining pattern and intensity of both TLRs in fetal basal keratinocytes was almost comparable to those of adults. Stimulation of primary human keratinocytes from fetal, neonatal and adult donors with selected TLR agonists revealed that the synthetic TLR3 ligand poly (I:C) specifically, mimicking viral double-stranded RNA, induced a significantly enhanced secretion of CXCL8/IL8, CXCL10/IP-10 and TNFα in fetal and neonatal keratinocytes compared with adult keratinocytes. This study demonstrates quantitative age-specific modifications in TLR expression and innate skin immune reactivity in response to TLR activation. Thus, antiviral innate immunity already in prenatal skin may contribute to protect the developing human body from viral infections in utero in a scenario where the adaptive immune system is not yet fully functional.

NF-κB hyperactivation in tumor tissues allows tumor-selective reprogramming of the chemokine microenvironment to enhance the recruitment of cytolytic T effector cells

Tumor infiltration with effector CD8(+) T cells (T(eff)) predicts longer recurrence-free survival in many types of human cancer, illustrating the broad significance of T(eff) for effective immunosurveillance. Colorectal tumors with reduced accumulation of T(eff) express low levels of T(eff)-attracting chemokines such as CXCL10/IP10 and CCL5/RANTES. In this study, we investigated the feasibility of enhancing tumor production of T(eff)-attracting chemokines as a cancer therapeutic strategy using a tissue explant culture system to analyze chemokine induction in intact tumor tissues. In different tumor explants, we observed highly heterogeneous responses to IFNα or poly-I:C (a TLR3 ligand) when they were applied individually. In contrast, a combination of IFNα and poly-I:C uniformly enhanced the production of CXCL10 and CCL5 in all tumor lesions. Moreover, these effects could be optimized by the further addition of COX inhibitors. Applying this triple combination also uniformly suppressed the production of CCL22/MDC, a chemokine associated with infiltration of T regulatory cells (T(reg)). The T(eff)-enhancing effects of this treatment occurred selectively in tumor tissues, as compared with tissues derived from tumor margins. These effects relied on the increased propensity of tumor-associated cells (mostly fibroblasts and infiltrating inflammatory cells) to hyperactivate NF-κB and produce T(eff)-attracting chemokines in response to treatment, resulting in an enhanced ability of the treated tumors to attract T(eff) cells and reduced ability to attract T(reg) cells. Together, our findings suggest the feasibility of exploiting NF-κB hyperactivation in the tumor microenvironment to selectively enhance T(eff) entry into colon tumors.

Epigallocatechin-3-gallate reduces airway inflammation in mice through binding to proinflammatory chemokines and inhibiting inflammatory cell recruitment

One major activity of chemokines is the recruitment of immune cells to sites of infection and inflammation. CD4(+) Th1 cells play critical roles in host defense against pathogens and in the pathogenesis of many immune-mediated diseases. It was reported that epigallocatechin-3-gallate (EGCG) exhibits anti-inflammatory properties, but the mechanisms have not been completely defined. In this study, we found that EGCG markedly decreased recruitment of murine OVA-specific Th1 cells and other inflammatory cells into the airways in a Th1 adoptive-transfer mouse model. In vitro analysis revealed that EGCG inhibited CXCR3 ligand-driven chemotaxis of murine and human cells. Surface plasmon resonance studies revealed that EGCG bound directly to chemokines CXCL9, CXCL10, and CXCL11. These results indicated that one anti-inflammatory mechanism of EGCG is binding of proinflammatory chemokines and limiting their biological activities. These findings support further development of EGCG as a potent therapeutic for inflammatory diseases.

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.

HIV-1 matrix protein p17: a candidate antigen for therapeutic vaccines against AIDS

The success in the development of anti-retroviral therapies (HAART) that contain human immunodeficiency virus type 1 (HIV-1) infection is challenged by the cost of this lifelong therapy and by its toxicity. Immune-based therapeutic strategies that boost the immune response against HIV-1 proteins or protein subunits have been recently proposed to control virus replication in order to provide protection from disease development, reduce virus transmission, and help limit the use of anti-retroviral treatments. HIV-1 matrix protein p17 is a structural protein that is critically involved in most stages of the life cycle of the retrovirus. Besides its well established role in the virus life cycle, increasing evidence suggests that p17 may also be active extracellularly in deregulating biological activities of many different immune cells that are directly or indirectly involved in AIDS pathogenesis. Thus, p17 might represent a promising target for developing a therapeutic vaccine as a contribution to combating AIDS. In this article we review the biological characteristics of HIV-1 matrix protein p17 and we describe why a synthetic peptide representative of the p17 functional epitope may work as a vaccine molecule capable of inducing anti-p17 neutralizing response against p17 derived from divergent HIV-1 strains.

LAIR2 localizes specifically to sites of extravillous trophoblast invasion

PURPOSE

A global gene expression microarray analysis of surplus chorionic villus sampling (CVS) tissues identified leukocyte-associated immunoglobulin-like receptor 2 (LAIR2) as down-regulated in the first trimester of pregnancies destined for preeclampsia. Neither the localization nor the function of LAIR2 has been examined in the placenta. Localization studies were conducted in placental tissues to determine the precise sites of LAIR2 mRNA production and protein binding.

RESULTS

Quantitative real time polymerase chain reaction (qRT-PCR) indicated LAIR2 expression in CVS, but none in breast, lymph node, kidney, skin, uterus, or third trimester placentas. In situ hybridization (ISH) revealed a highly restricted LAIR2 localization. LAIR2 mRNA was found only in the more distal portions of trophoblast anchoring cell columns, adjacent to the invading extravillous trophoblast (EVT). Immunohistochemistry (IHC) detected intracellular LAIR2 staining in these same cells. Extracellular staining of this soluble receptor was found in the acellular material between invasive EVT cells distal to the anchoring cell columns.

CONCLUSIONS

ISH and IHC staining for LAIR2 detected specific, highly localized expression at the leading edge of EVT anchoring cell columns in first trimester placentas. This staining likely identifies the site of production for this soluble receptor. Following secretion, the receptor appears to bind extracellular material among the invasive EVT. The precise restriction of this protein only to the sites of EVT invasion strongly suggests that it functions to regulate this invasion. The decreased LAIR2 expression noted in first trimester placentas that ultimately developed preeclampsia further suggests that alterations in LAIR2 may play an etiologic role in preeclampsia.

Simian immunodeficiency virus infection alters chemokine networks in lung tissues of cynomolgus macaques: association with Pneumocystis carinii infection

Infection by HIV-1 frequently leads to pulmonary complications, including alterations to local immune environments. To better understand these alterations, we have examined in detail the patterns and levels of expression of chemokine, cytokine, and chemokine receptor mRNAs in lung tissues from 16 uninfected or simian immunodeficiency virus (SIV)/DeltaB670 infected cynomolgus macaques at different stages of infection. Among the most up-regulated immune genes were interferon (IFN)-gamma, IFN-gamma-inducible CXCR3 ligands, and CCR5 ligands, as well as the cognate chemokine receptors. These changes were greatest in animals with clear Pneumocystis carinii coinfection. Immunohistochemistry and in situ hybridization revealed monocytes/macrophages to be the predominant type of cell infiltrating into lung tissues and serving as the major cellular source of chemokines. To explore the causes of chemokine alterations, we treated macaque lung cells with IFN-gamma, lipopolysaccharide, Poly(I:C), and P. carinii in vitro, and results revealed that these stimuli can induce the expression of CXCR3 ligand and/or CCR5 ligand mRNAs. Taken together, these studies provide a comprehensive definition of the chemokine networks available to modulate cellular recruitment to lung tissues during SIV infection and implicate both cytokines (IFN-gamma) and pathogens (SIV and P. carinii) as contributors to increased expression of pro-inflammatory chemokines.

Genome-wide mRNA expression correlates of viral control in CD4+ T-cells from HIV-1-infected individuals

There is great interindividual variability in HIV-1 viral setpoint after seroconversion, some of which is known to be due to genetic differences among infected individuals. Here, our focus is on determining, genome-wide, the contribution of variable gene expression to viral control, and to relate it to genomic DNA polymorphism. RNA was extracted from purified CD4+ T-cells from 137 HIV-1 seroconverters, 16 elite controllers, and 3 healthy blood donors. Expression levels of more than 48,000 mRNA transcripts were assessed by the Human-6 v3 Expression BeadChips (Illumina). Genome-wide SNP data was generated from genomic DNA using the HumanHap550 Genotyping BeadChip (Illumina). We observed two distinct profiles with 260 genes differentially expressed depending on HIV-1 viral load. There was significant upregulation of expression of interferon stimulated genes with increasing viral load, including genes of the intrinsic antiretroviral defense. Upon successful antiretroviral treatment, the transcriptome profile of previously viremic individuals reverted to a pattern comparable to that of elite controllers and of uninfected individuals. Genome-wide evaluation of cis-acting SNPs identified genetic variants modulating expression of 190 genes. Those were compared to the genes whose expression was found associated with viral load: expression of one interferon stimulated gene, OAS1, was found to be regulated by a SNP (rs3177979, p = 4.9E-12); however, we could not detect an independent association of the SNP with viral setpoint. Thus, this study represents an attempt to integrate genome-wide SNP signals with genome-wide expression profiles in the search for biological correlates of HIV-1 control. It underscores the paradox of the association between increasing levels of viral load and greater expression of antiviral defense pathways. It also shows that elite controllers do not have a fully distinctive mRNA expression pattern in CD4+ T cells. Overall, changes in global RNA expression reflect responses to viral replication rather than a mechanism that might explain viral control.

Nonpathogenesis of simian immunodeficiency virus infection is associated with reduced inflammation and recruitment of plasmacytoid dendritic cells to lymph nodes, not to lack of an interferon type I response, during the acute phase

Divergent Toll-like receptor 7 (TLR7) and TLR9 signaling has been proposed to distinguish pathogenic from nonpathogenic simian immunodeficiency virus infection in primate models. We demonstrate here that increased expression of type I interferon in pathogenic rhesus macaques compared to nonpathogenic African green monkeys was associated with the recruitment of plasmacytoid dendritic cells in the lymph nodes and the presence of an inflammatory environment early after infection, instead of a difference in the TLR7/9 response.

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.

Association between decreased CXCL12 and CCL25 expression and increased apoptosis in lymphoid tissues of cynomolgus macaques during SIV infection

BACKGROUND

Chemokines likely play multiple roles in HIV-1 and SIV pathogenesis. To examine potential associations between chemokine expression levels and apoptosis of cells in lymphoid tissues during SIV infection, we measured chemokine and cytokine mRNA levels in multiple lymphoid tissues compartments from uninfected and SIV-infected cynomolgus macaques (Macaca fascicularis).

METHODS

Real-time RT-PCR was used to measure host mRNA levels in macaque lymphoid tissues. Proliferating or apoptotic cells were identified in lymphoid tissues by immunohistochemistry.

RESULTS

We found that CXCL12 and CCL25 mRNAs in SIV-infected lymphoid tissues were decreased and their levels were negatively correlated with the numbers of proliferating and apoptotic cells. In vitro analyses revealed that CXCL12 and CCL25 were capable of reducing apoptosis induced by SIV infection.

CONCLUSIONS

These findings suggest that increased apoptosis in lymphoid tissues due to reduced levels of anti-apoptotic chemokines might be a mechanism that contributes to loss of immune function following pathogenic SIV infection.

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.

The dual role of dendritic cells in the immune response to human immunodeficiency virus type 1 infection

Many aspects of the complex interaction between human immunodeficiency virus type 1 (HIV-1) and the human immune system remain elusive. Our objective was to study these interactions, focusing on the specific roles of dendritic cells (DCs). DCs enhance HIV-1 infection processes as well as promote an antiviral immune response. We explored the implications of these dual roles. A mathematical model describing the dynamics of HIV-1, CD4+ and CD8+ T-cells, and DCs interacting in a human lymph node was analysed and is presented here. We have validated the behaviour of our model against non-human primate simian immunodeficiency virus experimental data and published human HIV-1 data. Our model qualitatively and quantitatively recapitulates clinical HIV-1 infection dynamics. We have performed sensitivity analyses on the model to determine which mechanisms strongly affect infection dynamics. Sensitivity analysis identifies system interactions that contribute to infection progression, including DC-related mechanisms. We have compared DC-dependent and -independent routes of CD4+ T-cell infection. The model predicted that simultaneous priming and infection of T cells by DCs drives early infection dynamics when activated T-helper cell numbers are low. Further, our model predicted that, while direct failure of DC function and an indirect failure due to loss of CD4+ T-helper cells are both significant contributors to infection dynamics, the former has a more significant impact on HIV-1 immunopathogenesis.

Lymph node architecture collapse and consequent modulation of FOXO3a pathway on memory T- and B-cells during HIV infection

Lymph nodes (LNs) represent the principal site where antigen-specific memory T- and B-cell responses are primed and differentiated into memory and effector cells. During chronic viral infections such as HIV, these lymphoid tissues undergo substantial structural changes. These changes are mostly caused by an imbalanced cytokine milieu, hyper-immune activation and collagen deposition leading to fibrotic LNs. The structural integrity of the LNs is essential to prime and maintain memory responses. Because cellular signalling events both up- and down-stream of FOXO3a are critical to the generation and the maintenance of lymphocyte memory, this review will focus on the interplay between the deregulation of the immune system caused by the virus and its impact on FOXO3a.

Minimal conjunctival limbal autograft for total limbal stem cell deficiency

PURPOSE

To report the results of one 60 degrees conjunctival limbal autograft (CLAU) combined with amniotic membrane (AM) transplantation for an eye with total limbal stem cell deficiency (LSCD).

METHODS

One eye of a patient with chronic total LSCD and symblepharon caused by chemical burn was subjected to symblepharon lysis, removal of pannus from corneal surface, AM transplantation to cover the conjunctival and corneal surfaces as a permanent graft, one 60 degrees CLAU to the superior limbal area, and insertion of ProKera as a temporary AM patch to cover the CLAU.

RESULTS

After surgery, corneal epithelialization over the AM was evident adjacent to the CLAU on day 6, progressed to pass the horizontal midline by day 11, and was completed by day 18. During a follow-up of 1 year, the corneal surface remained stable and smooth, and the stroma considerably regained clarity with regression of midstromal vascularization. The best-corrected visual acuity improved from 20/400 to 20/50. The conjunctival inflammation completely resolved, and the fornices were deep.

CONCLUSIONS

One 60 degrees CLAU combined with AM transplantation as both a permanent graft and a temporary patch can restore the entire corneal surface in an eye with total LSCD caused by chemical burn.

YKL-40, a marker of simian immunodeficiency virus encephalitis, modulates the biological activity of basic fibroblast growth factor

Human immunodeficiency virus encephalitis causes dementia in acquired immune deficiency syndrome patients. Using proteomic analysis of postmortem cerebrospinal fluid (CSF) and brain tissue from the simian immunodeficiency virus primate model, we demonstrate here a specific increase in YKL-40 that was tightly associated with lentiviral encephalitis. Longitudinal analysis of CSF from simian immunodeficiency virus-infected pigtailed macaques showed an increase in YKL-40 concentration 2 to 8 weeks before death from encephalitis. This increase in YKL-40 correlated with an increase in CSF viral load; it may therefore represent a biomarker for the development of encephalitis. Analysis of banked human CSF from human immunodeficiency virus-infected patients also demonstrated a correlation between YKL-40 concentration and CSF viral load. In vitro studies demonstrated increased YKL-40 expression and secretion by macrophages and microglia but not by neurons or astrocytes. We found that YKL40 displaced extracellular matrix-bound basic fibroblast growth factor (bFGF) as well as inhibited the mitogenic activity of both fibroblast growth factor receptor 1-expressing BaF3 cells and bFGF-induced axonal branching in hippocampal cultures. Taken together, these findings demonstrate that during lentiviral encephalitis, YKL-40 may interfere with the biological activity of bFGF and potentially of other heparin-binding growth factors and chemokines that can affect neuronal function or survival.

Chemokine and cytokine mediated loss of regulatory T cells in lymph nodes during pathogenic simian immunodeficiency virus infection

Regulatory T cells (T(reg)) play key roles in immune regulation through multiple modes of suppression. The effects of HIV-1 infection on T(reg) levels in lymphoid tissues remain incompletely understood. To explore this issue, we have measured the levels of forkhead box protein 3 (FOXP3)-positive cells and associated immunomodulatory genes in a pathogenic simian immunodeficiency virus/macaque model and found that a loss of T(reg) in lymph nodes occurred following simian immunodeficiency virus infection. Changes in expression of the ligands for CXCR3, CCR4, and CCR7 and the cytokines TGF-beta and IL-2 were all linked to this loss of T(reg), which in turn was linked with increased levels of cellular activation. Our findings identify three mechanisms that likely contribute to SIV-driven loss of T(reg), including reduced levels of cytokines associated with T(reg) differentiation and altered expression of agonist and antagonist chemokines. The loss of T(reg) and the associated cellular activation in lymphoid tissues is consistent with the events in HIV-1-infected individuals and suggest that components of the T(reg) differentiation and trafficking network could be targets for therapeutic intervention.

Afferent and efferent interfaces of lymph nodes are distinguished by expression of lymphatic endothelial markers and chemokines

BACKGROUND

Lymph nodes (LNs) are important sites of connection between the sampled peripheral tissues, the many cells of the immune system, and the blood. The organization of the interface between the afferent and efferent lymphatic vasculature and LN parenchyma is incompletely understood, and obtaining a better understanding of these tissue microenvironments will contribute to an improved understanding of overall lymphatic function.

METHODS AND RESULTS

We used histologic approaches to define the distributions of cells expressing lymphatic endothelial cell (LEC) markers in LNs from healthy, simian immunodeficiency virus (SIV) infected, or Mycobacterium tuberculosis infected cynomolgus macaques. Cells at the afferent and efferent interfaces of LNs from all animals showed differential expression of LEC markers, with podoplanin, Prox-1, and VEGFR3 expressed in both microenvironments, but with LYVE-1 expressed only at the efferent interface. The chemokine CCL20 was uniquely expressed at the afferent interface by cells co-expressing podoplanin, and this expression was increased during SIV or M. tuberculosis infection. In contrast, only a small proportion of cells expressing the CCR7 ligand CCL21 co-expressed podoplanin. Treatment of model LECs with the TLR3 ligand poly(I:C) or gamma-irradiated M. tuberculosis increased production of CCL20 without altering CCL21 or LEC marker expression.

CONCLUSIONS

This study provides a comprehensive mapping of the organization of the lymphatic endothelial network entering and exiting LNs in health and in chronic infectious diseases in a nonhuman primate model. The differences we have defined between the afferent and efferent interfaces of LNs could inform the future design of vaccines and immunotherapies.

Neuroinvasion of fluorescein-positive monocytes in acute simian immunodeficiency virus infection

Monocytes and macrophages play a central role in the pathogenesis of human immunodeficiency virus (HIV)-associated dementia. They represent prominent targets for HIV infection and are thought to facilitate viral neuroinvasion and neuroinflammatory processes. However, many aspects regarding monocyte brain recruitment in HIV infection remain undefined. The nonhuman primate model of AIDS is uniquely suited for examination of the role of monocytes in the pathogenesis of AIDS-associated encephalitis. Nevertheless, an approach to monitor cell migration from peripheral blood into the central nervous system (CNS) in primates had been lacking. Here, upon autologous transfer of fluorescein dye-labeled leukocytes, we demonstrate the trafficking of dye-positive monocytes into the choroid plexus stromata and perivascular spaces in the cerebra of rhesus macaques acutely infected with simian immunodeficiency virus between days 12 and 14 postinfection (p.i.). Dye-positive cells that had migrated expressed the monocyte activation marker CD16 and the macrophage marker CD68. Monocyte neuroinvasion coincided with the presence of the virus in brain tissue and cerebrospinal fluid and with the induction of the proinflammatory mediators CXCL9/MIG and CCL2/MCP-1 in the CNS. Prior to neuroinfiltration, plasma viral load levels peaked on day 11 p.i. Furthermore, the numbers of peripheral blood monocytes rapidly increased between days 4 and 8 p.i., and circulating monocytes exhibited increased functional capacity to produce CCL2/MCP-1. Our findings demonstrate acute monocyte brain infiltration in an animal model of AIDS. Such studies facilitate future examinations of the migratory profile of CNS-homing monocytes, the role of monocytes in virus import into the brain, and the disruption of blood-cerebrospinal fluid and blood-brain barrier functions in primates.

Pathogenesis of simian immunodeficiency virus-induced alterations in macaque trigeminal ganglia

Peripheral neuropathy is the most frequent neurologic complication associated with human immunodeficiency virus (HIV) infection, yet its pathogenesis remains poorly understood. To study the mechanisms causing HIV-induced peripheral nervous system disease, we examined trigeminal ganglia obtained from simian immunodeficiency virus (SIV)-inoculated macaques. SIV-infected macaques developed multifocal trigeminal ganglionitis of varying severity characterized by multifocal mononuclear infiltrates, neuronophagia, and neuronal loss resembling reports of HIV-associated changes present in dorsal root ganglia. Neuronal density, measured by calculating the fractional area of trigeminal ganglia occupied by neurons, was significantly lower in SIV-infected macaques versus uninfected macaques (p = 0.001). To characterize the inflammatory cell population and measure productive viral infection in ganglia, trigeminal ganglia from SIV-infected macaques were immunostained for macrophage or cytotoxic lymphocyte markers and for SIV gp41. The extent of macrophage infiltration in trigeminal ganglia was inversely correlated with neuronal loss (p = 0.001), whereas cytotoxic lymphocyte infiltration was not associated with neuronal loss. These studies demonstrate that alterations in the somatosensory ganglia of SIV-infected macaques closely parallel those observed in HIV-infected individuals and show that study of SIV-infected macaques may help elucidate the pathophysiology of HIV-induced peripheral neuropathy.

Gene expression profiling of gut mucosa and mesenteric lymph nodes in simian immunodeficiency virus-infected macaques with divergent disease course

BACKGROUND

Although the majority of drug-naïve HIV-infected patients develop acquired immunodeficiency syndrome (AIDS), a small percentage remains asymptomatic without therapeutic intervention.

METHODS

We have utilized the simian immunodeficiency virus (SIV)-infected rhesus macaque model to gain insights into the molecular mechanisms of long-term protection against simian AIDS.

RESULTS

Chronically SIV-infected macaques with disease progression had high viral loads and CD4(+) T-cell depletion in mucosal tissue and peripheral blood. These animals displayed pathologic changes in gut-associated lymphoid tissue (GALT) and mesenteric lymph node that coincided with increased expression of genes associated with interferon induction, inflammation and immune activation. In contrast, the animal with long-term asymptomatic infection suppressed viral replication and maintained CD4(+) T cells in both GALT and peripheral blood while decreasing expression of genes involved in inflammation and immune activation.

CONCLUSIONS

Our findings suggest that reduced immune activation and effective repair and regeneration of mucosal tissues correlate with long-term survival in SIV-infected macaques.

Early events in Mycobacterium tuberculosis infection in cynomolgus macaques

Little is known regarding the early events of infection of humans with Mycobacterium tuberculosis. The cynomolgus macaque is a useful model of tuberculosis, with strong similarities to human tuberculosis. In this study, eight cynomolgus macaques were infected bronchoscopically with low-dose M. tuberculosis; clinical, immunologic, microbiologic, and pathologic events were assessed 3 to 6 weeks postinfection. Gross pathological abnormalities were observed as early as 3 weeks, including Ghon complex formation by 5 weeks postinfection. Caseous granulomas were observed in the lung as early as 4 weeks postinfection. Only caseous granulomas were observed in the lungs at these early time points, reflecting a rigorous initial response. T-cell activation (CD29 and CD69) and chemokine receptor (CXCR3 and CCR5) expression appeared localized to different anatomic sites. Activation markers were increased on cells from airways and only at modest levels on cells in peripheral blood. The priming of mycobacterium-specific T cells, characterized by the production of gamma interferon occurred slowly, with responses seen only after 4 weeks of infection. These responses were observed from T lymphocytes in blood, airways, and hilar lymph node, with responses predominantly localized to the site of infection. From these studies, we conclude that immune responses to M. tuberculosis are relatively slow in the local and peripheral compartments and that necrosis occurs surprisingly quickly during granuloma formation.

Rapid virus dissemination in infant macaques after oral simian immunodeficiency virus exposure in the presence of local innate immune responses

A vaccine to protect human immunodeficiency virus (HIV)-exposed infants is an important goal in the global fight against the HIV pandemic. Two major challenges in pediatric HIV vaccine design are the competence of the neonatal/infant immune system in comparison to the adult immune system and the frequent exposure to HIV via breast-feeding. Based on the hypothesis that an effective vaccine needs to elicit antiviral immune responses directly at the site of virus entry, the pattern of virus dissemination in relation to host immune responses was determined in mucosal and lymphoid tissues of infant macaques at 1 week after multiple oral exposures to simian immunodeficiency virus (SIV). The results show that SIV disseminates systemically by 1 week. Infant macaques can respond rapidly to virus challenge and mount strong innate immune responses. However, despite systemic infection, these responses are most pronounced in tissues close to the viral entry site, with the tonsil being the primary site of virus replication and induction of immune responses. Thus, distinct anatomic compartments are characterized by unique cytokine gene expression patterns. Importantly, the early response at mucosal entry sites is dominated by the induction of proinflammatory cytokines, while cytokines with direct antiviral activity, alpha/beta interferons, are only minimally induced. In contrast, both antiviral and proinflammatory cytokines are induced in lymphoid tissues. Thus, although infant macaques can respond quickly to oral viral challenge, the locally elicited immune responses at mucosal entry sites are likely to favor immune activation and thereby virus replication and are insufficient to limit virus replication and dissemination.

TLR activation of Langerhans cell-like dendritic cells triggers an antiviral immune response

Langerhans cells (LC) are a unique subset of dendritic cells (DC), present in the epidermis and serving as the first line of defense against pathogens invading the skin. To investigate the role of human LCs in innate immune responses, we examined TLR expression and function of LC-like DCs derived from CD34+ progenitor cells and compared them to DCs derived from peripheral blood monocytes (monocyte-derived DC; Mo-DC). LC-like DCs and Mo-DCs expressed TLR1-10 mRNAs at comparable levels. Although many of the TLR-induced cytokine patterns were similar between the two cell types, stimulation with the TLR3 agonist poly(I:C) triggered significantly higher amounts of the IFN-inducible chemokines CXCL9 (monokine induced by IFN-gamma) and CXCL11 (IFN-gamma-inducible T cell alpha chemoattractant) in LC-like DCs as compared with Mo-DCs. Supernatants from TLR3-activated LC-like DCs reduced intracellular replication of vesicular stomatitis virus in a type I IFN-dependent manner. Finally, CXCL9 colocalized with LCs in skin biopsy specimens from viral infections. Together, our data suggest that LCs exhibit a direct antiviral activity that is dependent on type I IFN as part of the innate immune system.

Increased expression of interferon-inducible genes in macaque lung tissues during simian immunodeficiency virus infection

Pulmonary infections and dysfunction are frequent outcomes during the development of immunodeficiency associated with human immunodeficiency virus type 1 (HIV-1) infection, and obtaining a better understanding of the immunologic changes that occur in lungs following HIV-1 infection will provide a foundation for the development of further intervention strategies. We sought here to identify changes in the pulmonary immune environment that arise during simian immunodeficiency virus (SIV) infection of rhesus macaques, which serves as an excellent model system for HIV-1 infection and disease. To examine the gene expression profiles of macaque lung tissues following infection with the pathogenic SIV/DeltaB670 isolate, we performed cDNA microarray hybridizations with lung total RNAs using two commercially available cDNA arrays and a custom-fabricated, immunologically focused macaque cDNA microarray. In situ hybridization and real-time RT-PCR were performed to provide additional analyses of gene expression. Among the genes exhibiting the highest level of induction in lung tissues were the IFN-gamma-inducible chemokines, CXCL10/IP-10 and CXCL9/Mig. In situ hybridization and real-time RT-PCR strongly supported these findings. Correlation analyses revealed that the levels of expression of IFN-gamma, CXCL9/Mig, and CXCL10/IP-10 mRNAs were all strongly positively correlated, and that CXCL10/IP-10 mRNA and Pneumocystis carinii rRNA were positively correlated. Taken together, these findings demonstrate that inflammatory chemokines are among the most differentially expressed mRNAs in macaque lung tissues during systemic SIV infection of rhesus macaques, and provide insight into the complicated events occurring in the lung tissues during HIV-1 infection in humans.

HIV-1 Matrix Protein p17 Modulatesin VivoPreactivated Murine T-Cell Response and Enhances the Induction of Systemic and Mucosal Immunity Against Intranasally Co-administered Antigens

HIV-1 p17 is a viral cytokine that acts on preactivated, but not on resting, human T cells promoting proliferation, proinflammatory cytokines release and HIV-1 replication, after binding to a cellular receptor (p17R). Here, we demonstrate that p17Rs are expressed on activated murine T cells, which respond to p17 stimulation similarly to their human counterpart. We developed a mouse model of abortive HSV-1 infection to induce T cell activation in vivo. Preactivated cells expressed p17Rs and were highly susceptible to p17 stimulation, which triggered proinflammatory cytokines release and promoted CD4+ T cell survival and expansion. Coculture of in vivo activated splenocytes with macrophages in the presence of p17 further increased their ability to produce IFN-gamma. The presence of macrophages and activated T cells at mucosal sites prompted us to investigate the immunomodulatory activities of p17 in vivo. Intranasal coadministration of p17 with beta-galactosidase (beta-gal) resulted in improved beta-gal specific cellular and humoral immune responses at systemic and mucosal levels. It is well established that HIV-1 replication is driven in an autocrine/paracrine manner by endogenously produced proinflammatory cytokines. Our results highlight the role of p17 in sustaining cellular activation and inflammation, thereby promoting a permissive microenvironment for HIV-1 replication. In addition, p17 is a promising candidate antigen, exhibiting immunomodulatory/adjuvant properties, that need to be exploited in the development of HIV/AIDS vaccines.

Increased expression of TLR3 in lymph nodes during simian immunodeficiency virus infection: implications for inflammation and immunodeficiency

As pattern recognition receptors, TLRs signal and induce expression of multiple host defense genes including proinflammatory cytokines and chemokines. To investigate the mechanisms of up-regulation of proinflammatory cytokines and chemokines during SIV infection in rhesus macaques, we measured the relative levels of expression of TLRs 1-10 in lymphoid tissues during different stages of SIV infection. By real-time RT-PCR, TLR3 was determined to be up-regulated in macaque lymph nodes (LN) throughout the course of infection, whereas TLR9 was down-regulated during early stages of infection. CXCL9/Mig, CXCL10/IP-10, IFN-gamma, and IFN-alpha mRNAs were also increased during acute SIV infection and AIDS. Treatment of macaque spleen and LN cells with TLR3 and TLR9 ligands led to the induction of these same genes. TLR3 stimulation had disparate effects on viral transcription and viral replication, because poly(I:C), a model TLR3 ligand, stimulated the viral promoter but potently inhibited SIV replication in primary cultures of macaque spleen and LN cells. These findings identify roles for TLR3 inflammation in lymphoid tissues and in the immunopathogenesis of HIV-1/SIV, and suggest that TLR3 ligands could potentially be used to flush out latently infected cells that persist during antiretroviral therapies.

The chemokines CXCL9, CXCL10, and CXCL11 differentially stimulate G alpha i-independent signaling and actin responses in human intestinal myofibroblasts

Intestinal myofibroblasts have been implicated in the pathogenesis of chronic inflammatory conditions such as Crohn's disease via interactions with an elaborate network of cytokines, growth factors, and other inflammatory mediators. CXCR3 is a Galpha(i) protein-coupled receptor that binds the proinflammatory chemokines CXCL9, CXCL10, and CXCL11, which are released from the intestinal epithelium. The three CXCR3 ligands shared the ability to activate biochemical (e.g., PI3K and MAPK activation) and functional events (actin reorganization) in intestinal myofibroblasts. However, CXCL11 is unique in its ability to elevate intracellular calcium. Surprisingly, although CXCR3 mRNA is detectable in these myofibroblasts, there is no detectable surface expression of CXCR3. Furthermore, the biochemical responses and actin reorganization stimulated by the CXCR3 ligands in intestinal myofibroblasts are insensitive to the Galpha(i) inhibitor, pertussis toxin. This suggests either the existence of differential receptor coupling mechanisms in myofibroblasts for CXCR3 that are distinct from those observed in PBLs and/or that these cells express a modified or variant CXCR3 compared with the CXCR3 expressed on PBLs.

Distinct chemokine triggers and in vivo migratory paths of fluorescein dye-labeled T Lymphocytes in acutely simian immunodeficiency virus SIVmac251-infected and uninfected macaques

To define the possible impact of T-lymphocyte trafficking parameters on simian immunodeficiency virus (SIV) pathogenesis, we examined migratory profiles of carboxyfluorescein diacetate succinimidyl ester (CFSE)-labeled T lymphocytes in acutely SIVmac251-infected and uninfected macaques within 48 h after autologous transfer. Despite significant upregulation of homeostatic chemokine CCL19/macrophage inflammatory protein 3beta and proinflammatory chemokine CXCL9/monokine induced by gamma interferon in secondary lymphoid tissue in SIV infection, no differences in CFSE+ T-lymphocyte frequencies or cell compartmentalization in lymph nodes were identified between animal groups. By contrast, a higher frequency of CFSE+ T lymphocytes in the small intestine was detected in acute SIV infection. This result correlated with increased numbers of gut CD4 T lymphocytes expressing chemokine receptors CCR9, CCR7, and CXCR3 and high levels of their respective chemokine ligands in the small intestine. The changes in trafficking parameters in SIV-infected macaques occurred concomitantly with acute gut CD4 T-lymphocyte depletion. Here, we present the first in vivo T-lymphocyte trafficking study in SIV infection and a novel approach to delineate T-lymphocyte recruitment into tissues in the nonhuman primate animal model for AIDS. Such studies are likely to provide unique insights into T-lymphocyte sequestration in distinct tissue compartments and possible mechanisms of CD4 T-lymphocyte depletion and immune dysfunction in simian AIDS.

Immune mechanisms associated with protection from vaginal SIV challenge in rhesus monkeys infected with virulence-attenuated SHIV 89.6

Although live-attenuated human immunodeficiency virus-1 (HIV) vaccines may never be used clinically, these vaccines have provided the most durable protection from intravenous (IV) challenge in the simian immunodeficiency virus (SIV)/rhesus macaque model. Systemic infection with virulence attenuated-simian-human immunodeficiency virus (SHIV) 89.6 provides protection against vaginal SIV challenge. This paper reviews the findings related to the innate and adaptive immune responses and the role of inflammation associated with protection in the SHIV 89.6/SIVmac239 model. By an as yet undefined mechanism, most monkeys vaccinated with live-attenuated SHIV 89.6 mounted effective anti-viral CD8+ T cell responses while avoiding the self-destructive inflammatory cycle found in the lymphoid tissues of unprotected and unvaccinated monkeys.

Roles for CXC chemokine ligands 10 and 11 in recruiting CD4+ T cells to HIV-1-infected monocyte-derived macrophages, dendritic cells, and lymph nodes

We investigated roles for chemoattractants in dissemination of HIV-1 by examining the induction of T cell-active chemokines in HIV-1-infected human monocyte-derived macrophages and dendritic cells. Of the 12 chemokines analyzed, mRNAs for two, CXCL10 and CXCL11, ligands for the chemokine receptor CXCR3, were up-regulated in both cell types upon infection by HIV-1. Induction of these chemokine genes in infected cultures was dependent on both viral entry and reverse transcriptase activity, but not on the HIV-1 envelope glycoprotein. Conditioned medium from infected cells was chemotactic for freshly isolated human CD4+ T cells, and chemotaxis was abolished by pretreatment with an Ab against CXCR3. A lymph node from an HIV-1-infected individual expressed CXCL10 and CXCL11 mRNAs in the paracortex, including venules, as detected by in situ hybridization, whereas neither mRNA was detected after highly active antiretroviral therapy. Because CCR5 on CD4+ T cells is found predominantly on cells that also express CXCR3, these data implicate CXCL10 and CXCL11 in the recruitment of susceptible T cells to HIV-1-infected lymph nodes, macrophages, and dendritic cells. This recruitment might enhance the sequestration of T cells in infected lymphoid organs and the spread of infection between cells, contributing to the immunopathology of AIDS.

Early antiretroviral therapy for simian immunodeficiency virus infection leads to mucosal CD4+ T-cell restoration and enhanced gene expression regulating mucosal repair and regeneration

Simian immunodeficiency virus (SIV) and human immunodeficiency virus (HIV) infections lead to rapid depletion of CD4(+) T cells from gut-associated lymphoid tissue (GALT). Although the administration of antiretroviral therapy (ART) has been shown to increase CD4(+) T-cell levels in the peripheral blood in both SIV and HIV infections, its efficacy in restoring intestinal mucosal CD4(+) T cells has not been well investigated. To gain insights into the molecular mechanisms of virally induced disruptions in the mucosal immune system, we have evaluated longitudinal changes in viral burden, T-cell subsets, and mucosal gene expression profiles in SIV-infected rhesus macaques in the absence or presence of ART. Our results demonstrate a dramatic suppression of mucosal viral loads and rapid reconstitution of CD4(+) T cells in GALT in animals receiving ART that were not observed in untreated SIV-infected animals. DNA microarray-based gene expression profiling indicated that CD4(+) T-cell restoration in GALT was associated with up regulation of growth factors and genes involved in repair and regeneration of the mucosal epithelium. In contrast, untreated SIV-infected animals increased expression of lymphocyte activation and inflammatory response-associated genes and did not up regulate mucosal growth and repair associated transcription. In conclusion, these data indicate that initiating ART in primary SIV infection may lead to the restoration of the mucosal immune system through reduction of inflammation and promotion of epithelial repair in the intestinal mucosa.

Simian human immunodeficiency virus-associated pneumonia correlates with increased expression of MCP-1, CXCL10, and viral RNA in the lungs of rhesus macaques

Pulmonary disorders are the most frequent cause of death in HIV-1-infected individuals with AIDS and remain important even in the current era of potent antiretroviral therapy. Macaques infected with Simian/Human Immunodeficiency Virus (SHIV) develop pulmonary disease and concurrent opportunistic infections similar to those observed in HIV-infected individuals, thereby providing an excellent working model to elucidate the pathogenesis of the human lung disease. Since chemokines play a crucial role in the recruitment of inflammatory cells to tissues, we investigated the relationship between respiratory disease and the levels of chemokines, monocyte chemotactic protein-1 (MCP-1) and CXCL10, in the lungs of SHIV-infected rhesus macaques. We found that lung pathology in infected macaques was closely associated with overexpression of MCP-1 and CXCL10. In addition, these chemokines could, in part, be responsible for the recruitment of inflammatory cells infiltrating into the diseased lungs as demonstrated by chemotactic assays. Lung pathology and increased levels of MCP-1 and CXCL10 correlated with high viral loads in the lung parenchyma. Using confocal microscopy, we identified SHIV-infected macrophages as the major producers of MCP-1 and CXCL10 in the diseased lungs. These data suggest that chemokine overexpression plays an important role in the pathogenesis of SHIV-associated pulmonary disease in macaques.