Gamma interferon-mediated inflammation is associated with lack of protection from intravaginal simian immunodeficiency virus SIVmac239 challenge in simian-human immunodeficiency virus 89.6-immunized rhesus macaques

Stage-specific IFN-induced and IFN gene expression reveal convergence of type I and type II IFN and highlight their role in both acute and chronic stage of pathogenic SIV infection

Interferons (IFNs) play a major role in controlling viral infections including HIV/SIV infections. Persistent up-regulation of interferon stimulated genes (ISGs) is associated with chronic immune activation and progression in SIV/HIV infections, but the respective contribution of different IFNs is unclear. We analyzed the expression of IFN genes and ISGs in tissues of SIV infected macaques to understand the respective roles of type I and type II IFNs. Both IFN types were induced in lymph nodes during early stage of primary infection and to some extent in rectal biopsies but not in PBMCs. Induction of Type II IFN expression persisted during the chronic phase, in contrast to undetectable induction of type I IFN expression. Global gene expression analysis with a major focus on ISGs revealed that at both acute and chronic infection phases most differentially expressed ISGs were inducible by both type I and type II IFNs and displayed the highest increases, indicating strong convergence and synergy between type I and type II IFNs. The analysis of functional signatures of ISG expression revealed temporal changes in IFN expression patterns identifying phase-specific ISGs. These results suggest that IFN-γ strongly contribute to shape ISG upregulation in addition to type I IFN.

Social instability and immunity in rhesus monkeys: the role of the sympathetic nervous system

Social instability can adversely affect endocrine, immune and health outcomes, and recent evidence suggests that the sympathetic nervous system (SNS) might mediate these effects. We conducted two studies with adult male rhesus monkeys (Macaca mulatta) to understand how social conditions affect measures of SNS activity and immune function. In Experiment 1, animals were socialized in stable social conditions, then were switched to unstable (stressful) social conditions, then were returned to stable conditions. Analysis revealed quadratic effects for measures of behaviour, urinary metabolites of epinephrine and norepinephrine, and expression of immune response genes: as expected, social instability adversely impacted most measures, and the effects remediated upon re-imposition of stable conditions. Cortisol levels were unaffected. In Experiment 2, we used the sympathomimetic drug methamphetamine to challenge the SNS; animals also underwent socialization in stable or unstable groups. Surprisingly, while methamphetamine elevated plasma catecholamines, responses in lymph nodes tracked the social, and not the drug, condition: social instability upregulated the density of SNS fibres in lymph nodes and downregulated Type I interferon gene expression. Together, these results indicate that the SNS is extremely sensitive to social conditions; full understanding of the adverse effects of social instability on health should therefore incorporate measures of this health-relevant system.

Multiple low-dose challenges in a rhesus macaque AIDS vaccine trial result in an evolving host response that affects protective outcome

Using whole-blood transcriptional profiling, we investigated differences in the host response to vaccination and challenge in a rhesus macaque AIDS vaccine trial. Samples were collected from animals prior to and after vaccination with live, irradiated vaccine cells secreting the modified endoplasmic reticulum chaperone gp96-Ig loaded with simian immunodeficiency virus (SIV) peptides, either alone or in combination with a SIV-gp120 protein boost. Additional samples were collected following multiple low-dose rectal challenges with SIVmac251. Animals in the boosted group had a 73% reduced risk of infection. Surprisingly, few changes in gene expression were observed during the vaccination phase. Focusing on postchallenge comparisons, in particular for protected animals, we identified a host response signature of protection comprised of strong interferon signaling after the first challenge, which then largely abated after further challenges. We also identified a host response signature, comprised of early macrophage-mediated inflammatory responses, in animals with undetectable viral loads 5 days after the first challenge but with unusually high viral titers after subsequent challenges. Statistical analysis showed that prime-boost vaccination significantly lowered the probability of infection in a time-consistent manner throughout several challenges. Given that humoral responses in the prime-boost group were highly significant prechallenge correlates of protection, the strong innate signaling after the first challenge suggests that interferon signaling may enhance vaccine-induced antibody responses and is an important contributor to protection from infection during repeated low-dose exposure to SIV.

Accumulation of functionally immature myeloid dendritic cells in lymph nodes of rhesus macaques with acute pathogenic simian immunodeficiency virus infection

Myeloid dendritic cells (mDC) are key mediators of innate and adaptive immunity to virus infection, but the impact of HIV infection on the mDC response, particularly early in acute infection, is ill-defined. We studied acute pathogenic simian immunodeficiency virus (SIV) infection of rhesus macaques to address this question. The mDC in blood and bone marrow were depleted within 12 days of intravenous infection with SIVmac251, associated with a marked proliferative response. In lymph nodes, mDC were apoptotic, activated and proliferating, despite normal mDC numbers, reflecting a regenerative response that compensated for mDC loss. Blood mDC had increased expression of MHC class II, CCR7 and CD40, whereas in lymph nodes these markers were significantly decreased, indicating that acute infection induced maturation of mDC in blood but resulted in accumulation of immature mDC in lymph nodes. Following SIV infection, lymph node mDC had an increased capacity to secrete tumour necrosis factor-α upon engagement with a Toll-like receptor 7/8 ligand that mimics exposure to viral RNA, and this was inversely correlated with MHC class II and CCR7 expression. Lymph node mDC had an increased ability to capture and cleave soluble antigen, confirming their functionally immature state. These data indicate that acute SIV infection results in increased mDC turnover, leading to accumulation in lymph nodes of immature mDC with an increased responsiveness to virus stimulation.

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.

Interferon-γ and its pathway-associated gene expression in the vaginal tissue of premenopausal females with pelvic organ prolapse

Interferon (IFN)-γ is a potent proinflammatory molecule. However, few studies have investigated the expression levels of IFN-γ during pelvic organ prolapse (POP). In the present study, the expression levels and tissue localization of IFN-γ and its pathway-associated genes were detected in the vaginal walls of premenopausal females with POP and asymptomatic controls using quantitative polymerase chain reaction and immunohistochemistry. When compared with the matched controls, an 8.6-fold increase in IFN-γ, 3.8-fold increase in IFN-γ receptor (IFNGR)1, 2.6-fold increase in IFNGR2, 3.4-fold increase in signal transducer and activator of transcription-1, 2.2-fold increase in janus kinase-1 and 5.1-fold increase in nuclear factor (NF)-κB mRNA expression levels were observed in the females with premenopausal POP. In all the females with POP, higher mRNA expression levels of IFN-γ and its receptors were observed when compared with the controls. Expression levels of all the proteins were detected by immunohistochemistry, and the results demonstrated higher staining for IFN-γ, IFNGRs and pathway-associated genes in females with POP. Therefore, the results indicated that IFN-γ may be used as an inflammatory marker for POP development, and is associated with NF-κB.

Protective Efficacy of Nonpathogenic Nef-Deleted SHIV Vaccination Combined with Recombinant IFN-γ Administration against a Pathogenic SHIV Challenge in Rhesus Monkeys

We previously reported that a nef-deleted SHIV (SHIV-NI) is nonpathogenic and gave macaques protection from challenge infection with pathogenic SHIV-C2/1. To investigate whether IFN-gamma augments the immune response induced by this vaccination, we examined the antiviral and adjuvant effect of recombinant human IFN-gamma (rIFN-gamma) in vaccinated and unvaccinated monkeys. Nine monkeys were vaccinated with nef-deleted nonpathogenic SHIV-NI. Four of them were administered with rIFN-gamma and the other five monkeys were administered with placebo. After the challenge with pathogenic SHIV-C2/1, CD4(+) T-cell counts were maintained similarly in monkeys of both groups, while those of the unvaccinated monkeys decreased dramatically at 2 weeks after challenge. However, the peaks of plasma viral load were reduced to 100-fold in SHIV-NI vaccinated monkeys combined with rIFN-gamma compared with those in SHIV-NI vaccinated monkeys without rIFN-gamma. The peaks of plasma viral load were inversely correlated with the number of SIV Gag-specific IFN-gamma-producing cells. In SHIV-NI-vaccinated monkeys with rIFN-gamma, the number of SIV Gag-specific IFN-gamma-producing cells of PBMCs increased 2-fold compared with those in SHIV-NI-vaccinated monkeys without rIFN-gamma, and the NK activity and MIP-1alpha production of PBMCs were also enhanced. Thus, vaccination of SHIV-NI in combination with rIFN-gamma was more effective in modulating the antiviral immune system into a Th1 type response than SHIV-NI vaccination alone. These results suggest that IFN-gamma augmented the anti-viral effect by enhancing innate immunity and shifting the immune response to Th1.

The role of prostaglandin E2 in human vascular inflammation

Prostaglandins (PG) are the product of a cascade of enzymes such as cyclooxygenases and PG synthases. Among PG, PGE2 is produced by 3 isoforms of PGE synthase (PGES) and through activation of its cognate receptors (EP1-4), this PG is involved in the pathophysiology of vascular diseases. Some anti-inflammatory drugs (e.g. glucocorticoids, nonsteroidal anti-inflammatory drugs) interfere with its metabolism or effects. Vascular cells can initiate many of the responses associated with inflammation. In human vascular tissue, PGE2 is involved in many physiological processes, such as increasing vascular permeability, cell proliferation, cell migration and control of vascular smooth muscle tone. PGE2 has been shown to contribute to the pathogenesis of atherosclerosis, abdominal aortic aneurysm but also in physiologic/adaptive processes such as angiogenesis. Understanding the roles of PGE2 and its cognate receptors in vascular diseases could help to identify diagnostic and prognostic biomarkers. In addition, from these recent studies new promising therapeutic approaches like mPGES-1 inhibition and/or EP4-antagonism should be investigated.

Resolution of PMA-induced skin inflammation involves interaction of IFN-γ and ALOX15

BACKGROUND

Acute inflammation and its timely resolution play important roles in the body's responses to the environmental stimulation. Although IFN-γ is well known for the induction of inflammation, its role in the inflammation resolution is still poorly understood.

METHODOLOGY AND PRINCIPAL FINDINGS

In this study, we investigated the function of interferon gamma (IFN-γ) during the resolution of PMA-induced skin inflammation in vivo. The results revealed that the expression levels of IL-6, TNF-α, and monocyte chemoattractant protein 1 (MCP-1) in skin decreased during the resolution stage of PMA-induced inflammation, while IFN-γ is still maintained at a relatively high level. Neutralization of endogenous IFN-γ led to accelerated reduction of epidermal thickness and decreased epithelial cell proliferation. Similarly, decreased infiltration of inflammatory cells (Gr1(+) or CD11b(+) cells) and a significant reduction of proinflammatory cytokines were also observed upon the blockade of IFN-γ. Furthermore, neutralization of IFN-γ boosted ALOX15 expression of the skin during inflammation resolution. In accordance, application of lipoxin A4 (LXA4, a product of ALOX15) obtained a proresolution effect similar to neutralization of IFN-γ. These results demonstrated that through upregulating ALOX15-LXA4 pathway, blockage of IFN-γ can promote the resolution of PMA-induced skin inflammation.

In captive rhesus macaques, cervicovaginal inflammation is common but not associated with the stable polymicrobial microbiome

Vaginal inoculation of rhesus macaques (RM) with simian immunodeficiency virus (SIV) has been used to study the biology of HIV transmission. Although the results of vaginal SIV transmission experiments could be affected by vaginal inflammation, studies to date have been conducted without regard to levels of pre-existing genital inflammation present in RM. We collected cevicovaginal secretions (CVS) from 33–36 RM during the mid menstrual cycle (day 10–20) at 2 time points approximately 8 months apart and characterized the mRNA and protein levels of inflammatory cytokines, chemokines and interferon-stimulated genes. There was extreme variability in the levels of inflammatory mediators (IFN-α, IFN-γ, IL-6, TNF, IL-1b, IP-10, MIG, IL-12 and IL-17). In most animals, the mRNA levels of the inflammatory mediators were similar in the 2 CVS samples collected 8 months apart, suggesting that genital inflammation is stable in a subset of captive female RM. At both time points the cervicovaginal microbiota had low levels of Lactobacillus and was relatively diverse with an average of 13 genera in the samples from the first time point (median 13, range 7–21) and an average of 11.5 genera in the samples from the second time point (median 11, range 5–20). Many of the macaques had similar microbiota in the samples collected 8 months apart. However, we found no correlation between specific bacterial genera and the mRNA or protein levels of the inflammatory mediators in the genital tract of RM in this study. It seems likely that results of published vaginal SIV transmission experiments in RM have been influenced by pre-existing inflammation in the animals used for the experiments.

HSV-2 infection of dendritic cells amplifies a highly susceptible HIV-1 cell target

Herpes simplex virus type 2 (HSV-2) increases the risk of HIV-1 infection and, although several reports describe the interaction between these two viruses, the exact mechanism for this increased susceptibility remains unclear. Dendritic cells (DCs) at the site of entry of HSV-2 and HIV-1 contribute to viral spread in the mucosa. Specialized DCs present in the gut-associated lymphoid tissues produce retinoic acid (RA), an important immunomodulator, able to influence HIV-1 replication and a key mediator of integrin α₄β₇ on lymphocytes. α₄β₇ can be engaged by HIV-1 on the cell-surface and CD4⁺ T cells expressing high levels of this integrin (α₄β₇ (high)) are particularly susceptible to HIV-1 infection. Herein we provide in-vivo data in macaques showing an increased percentage of α₄β₇ (high) CD4⁺ T cells in rectal mucosa, iliac lymph nodes and blood within 6 days of rectal exposure to live (n = 11), but not UV-treated (n = 8), HSV-2. We found that CD11c⁺ DCs are a major target of HSV-2 infection in in-vitro exposed PBMCs. We determined that immature monocyte-derived DCs (moDCs) express aldehyde dehydrogenase ALDH1A1, an enzyme essential for RA production, which increases upon HSV-2 infection. Moreover, HSV-2-infected moDCs significantly increase α₄β₇ expression on CD4⁺ T lymphocytes and HIV-1 infection in DC-T cell mixtures in a RA-dependent manner. Thus, we propose that HSV-2 modulates its microenviroment, influencing DC function, increasing RA production capability and amplifying a α₄β₇ (high)CD4⁺ T cells. These factors may play a role in increasing the susceptibility to HIV-1.

Early myeloid dendritic cell dysregulation is predictive of disease progression in simian immunodeficiency virus infection

Myeloid dendritic cells (mDC) are lost from blood in individuals with human immunodeficiency virus (HIV) infection but the mechanism for this loss and its relationship to disease progression are not known. We studied the mDC response in blood and lymph nodes of simian immunodeficiency virus (SIV)-infected rhesus macaques with different disease outcomes. Early changes in blood mDC number were inversely correlated with virus load and reflective of eventual disease outcome, as animals with stable infection that remained disease-free for more than one year had average increases in blood mDC of 200% over preinfection levels at virus set-point, whereas animals that progressed rapidly to AIDS had significant loss of mDC at this time. Short term antiretroviral therapy (ART) transiently reversed mDC loss in progressor animals, whereas discontinuation of ART resulted in a 3.5-fold increase in mDC over preinfection levels only in stable animals, approaching 10-fold in some cases. Progressive SIV infection was associated with increased CCR7 expression on blood mDC and an 8-fold increase in expression of CCL19 mRNA in lymph nodes, consistent with increased mDC recruitment. Paradoxically, lymph node mDC did not accumulate in progressive infection but rather died from caspase-8-dependent apoptosis that was reduced by ART, indicating that increased recruitment is offset by increased death. Lymph node mDC from both stable and progressor animals remained responsive to exogenous stimulation with a TLR7/8 agonist. These data suggest that mDC are mobilized in SIV infection but that an increase in the CCR7-CCL19 chemokine axis associated with high virus burden in progressive infection promotes exodus of activated mDC from blood into lymph nodes where they die from apoptosis. We suggest that inflamed lymph nodes serve as a sink for mDC through recruitment, activation and death that contributes to AIDS pathogenesis.

Myeloid dendritic cells (mDC) are essential innate immune system cells that are lost from blood in human immunodeficiency virus infection through an ill-defined mechanism. We studied the kinetics of the mDC response in blood and lymph nodes of rhesus macaques infected with the closely related simian immunodeficiency virus. We found that differences in the number of blood mDC correlated with eventual disease outcome, as at virus set-point mDC were increased in blood in animals remaining disease free but lost from blood in animals that progressed rapidly to AIDS. mDC loss was linked to an increase in the chemokine axis responsible for mDC recruitment to lymph nodes; however, mDC did not accumulate in tissues but rather died from apoptosis. Lymph node mDC remained responsive to stimulation with a TLR7/8 agonist during infection. Importantly, mDC dysregulation was partially reversed by antiretroviral therapy. These data indicate that chronic mDC recruitment, activation and death within lymph nodes precede development of disease in SIV infected monkeys and may play a role in AIDS pathogenesis.

A recombinant measles virus unable to antagonize STAT1 function cannot control inflammation and is attenuated in rhesus monkeys

Measles remains a leading cause of death worldwide among children because it suppresses immune function. The measles virus (MV) P gene encodes three proteins (P, V, and C) that interfere with innate immunity, controlling STAT1, STAT2, mda5, and perhaps other key regulators of immune function. We identified here three residues in the shared domain of the P and V proteins-tyrosine 110, valine 112, and histidine 115-that function to retain STAT1 in the cytoplasm and inhibit interferon transcription. This information was used to generate a recombinant measles virus unable to antagonize STAT1 function (STAT1-blind MV) differing only in these three residues from a wild-type strain of well-defined virulence. This virus was used to assess the relevance of P and V interactions with STAT1 for virulence in primates. When a group of six rhesus monkeys (Macaca mulatta) was inoculated intranasally with STAT1-blind MV, viremia was short-lived, and the skin rash and other clinical signs observed with wild-type MV were absent. The STAT1-blind virus less efficiently controlled the inflammatory response, as measured by enhanced transcription of interleukin-6 and tumor necrosis factor alpha in peripheral blood mononuclear cells from infected hosts. Importantly, neutralizing antibody titers and MV-specific T-cell responses were equivalent in hosts infected with either virus. These findings indicate that efficient MV interactions with STAT1 are required to sustain virulence in a natural host by controlling the inflammatory response against the virus. They also suggest that selectively STAT1-blind MV may have utility as vectors for targeted oncolysis and vaccination.

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.

Immunogenicity of viral vector, prime-boost SIV vaccine regimens in infant rhesus macaques: attenuated vesicular stomatitis virus (VSV) and modified vaccinia Ankara (MVA) recombinant SIV vaccines compared to live-attenuated SIV

In a previously developed infant macaque model mimicking HIV infection by breast-feeding, we demonstrated that intramuscular immunization with recombinant poxvirus vaccines expressing simian immunodeficiency virus (SIV) structural proteins provided partial protection against infection following oral inoculation with virulent SIV. In an attempt to further increase systemic but also local antiviral immune responses at the site of viral entry, we tested the immunogenicity of different orally administered, replicating vaccines. One group of newborn macaques received an oral prime immunization with a recombinant vesicular stomatitis virus expressing SIVmac239 gag, pol and env (VSV-SIVgpe), followed 2 weeks later by an intramuscular boost immunization with MVA-SIV. Another group received two immunizations with live-attenuated SIVmac1A11, administered each time both orally and intravenously. Control animals received mock immunizations or non-SIV VSV and MVA control vectors. Analysis of SIV-specific immune responses in blood and lymphoid tissues at 4 weeks of age demonstrated that both vaccine regimens induced systemic antibody responses and both systemic and local cell-mediated immune responses. The safety and immunogenicity of the VSV-SIVgpe+MVA-SIV immunization regimen described in this report provide the scientific incentive to explore the efficacy of this vaccine regimen against virulent SIV exposure in the infant macaque model.

Limited dissemination of pathogenic SIV after vaginal challenge of rhesus monkeys immunized with a live, attenuated lentivirus

In non-human primate models of AIDS, attenuated lentiviruses provide the most reliable protection from challenge with pathogenic virus but the extent to which the vaccine virus replicates after challenge is unclear. At 7 and 14 days after vaginal challenge with pathogenic SIVmac239, plasma SIVenv RNA levels were significantly lower in female macaques immunized 6 months earlier with live, attenuated SHIV89.6 compared to unimmunized control animals. In 2 SHIV-immunized, unprotected macaques SIV replication produced moderate-level plasma viremia with dissemination of challenge virus to all tissues on day 14 after challenge. In protected, SHIV-immunized monkeys, SIV replication was controlled in all tissues, from the day of challenge through 14 days post-challenge. Further, in CD8(+) T cell-depleted SHIV-immunized animals, SIV replication and dissemination were more rapid than in control animals. These findings suggest that replication of a pathogenic AIDS virus can be controlled at the site of mucosal inoculation by live-attenuated lentivirus immunization.

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.

Ozone and allergen exposure during postnatal development alters the frequency and airway distribution of CD25+ cells in infant rhesus monkeys

The epidemiologic link between air pollutant exposure and asthma has been supported by experimental findings, but the mechanisms are not understood. In this study, we evaluated the impact of combined ozone and house dust mite (HDM) exposure on the immunophenotype of peripheral blood and airway lymphocytes from rhesus macaque monkeys during the postnatal period of development. Starting at 30 days of age, monkeys were exposed to 11 cycles of filtered air, ozone, HDM aerosol, or ozone+HDM aerosol. Each cycle consisted of ozone delivered at 0.5 ppm for 5 days (8 h/day), followed by 9 days of filtered air; animals received HDM aerosol during the last 3 days of each ozone exposure period. Between 2-3 months of age, animals co-exposed to ozone+HDM exhibited a decline in total circulating leukocyte numbers and increased total circulating lymphocyte frequency. At 3 months of age, blood CD4+/CD25+ lymphocytes were increased with ozone+HDM. At 6 months of age, CD4+/CD25+ and CD8+/CD25+ lymphocyte populations increased in both blood and lavage of ozone+HDM animals. Overall volume of CD25+ cells within airway mucosa increased with HDM exposure. Ozone did not have an additive effect on volume of mucosal CD25+ cells in HDM-exposed animals, but did alter the anatomical distribution of this cell type throughout the proximal and distal airways. We conclude that a window of postnatal development is sensitive to air pollutant and allergen exposure, resulting in immunomodulation of peripheral blood and airway lymphocyte frequency and trafficking.

Enhanced antibody responses elicited by a CpG adjuvant do not improve the protective effect of an aldrithiol-2-inactivated simian immunodeficiency virus therapeutic AIDS vaccine

The potential benefit of using unmethylated CpG oligoribodeoxynucleotides (ODN) as an adjuvant in a therapeutic simian immunodeficiency virus (SIV) vaccine consisting of AT2-inactivated SIVmac239 was evaluated in SIV-infected rhesus macaques receiving antiretroviral therapy (ART). We hypothesized that using CpG ODN as an adjuvant in therapeutic vaccination would enhance SIV-specific immune responses and suppress SIV replication after ART was stopped. To test our hypothesis, we immunized chronically SIV-infected rhesus macaques receiving ART with one of the following therapeutic vaccines: (i) AT2-inactivated SIVmac239, (ii) CpG10103 plus AT2-inactivated SIVmac239, (iii) CpG10103, and (iv) saline. While immunization with CpG plus AT2-SIVmac239 significantly increased SIV-specific immunoglobulin G (IgG) antibody titers, the mean plasma viral RNA (vRNA) level in these animals after ART did not differ from those of saline-treated animals. The AT2-inactivated SIVmac239-immunized animal group had a significantly higher mean SIV-specific gamma interferon T-cell response after three immunizations and lower plasma vRNA levels for 6 weeks after ART was withdrawn compared to the saline-treated animal group. Compared to the saline control group, the animal group treated with CpG alone had a significantly higher mean SIV-specific lymphocyte proliferation index and a higher rate of plasma vRNA rebound after ART. These results demonstrate that while the use of CpG as an adjuvant enhances SIV-specific antibody responses, this does not improve the control of SIV replication after ART is stopped. The lack of benefit may be related to the high levels of SIV-specific lymphocyte proliferation in the CpG adjuvant group.

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.

Attenuation of V- or C-defective measles viruses: infection control by the inflammatory and interferon responses of rhesus monkeys

Patients recruited in virus-based cancer clinical trials and immunocompromised individuals in need of vaccination would profit from viral strains with defined attenuation mechanisms. We generated measles virus (MV) strains defective for the expression of either the V protein, a modulator of the innate immune response, or the C protein, which has multiple functions. The virulence of these strains was compared with that of the parental wild-type MV in a natural host, Macaca mulatta. Skin rash, viremia, and the strength of the innate and adaptive immune responses were characterized in groups of six animals. Replication of V- or C-protein-defective viruses was short-lived and reached lower levels in peripheral blood mononuclear cells and lymphatic organs compared to the wild-type virus; none of the mutants reverted to the wild type. The neutralizing antibody titers and MV-specific T-cell responses were equivalent in monkeys infected with the viral strains tested, documenting strong adaptive immune responses. In contrast, the inflammatory response was better controlled by wild-type MV, as revealed by inhibition of interleukin-6 and tumor necrosis factor alpha transcription. The interferon response was also better controlled by the wild-type virus than by the defective viruses. Since V- and C-defective MVs induce strong adaptive immune responses while spreading less efficiently, they may be developed as vaccines for immunocompromised individuals. Moreover, MV unable to interact with single innate immunity proteins may be developed for preferential replication in tumors with specific contexts of vulnerability.

Rise in gamma interferon expression during resolution of duck hepatitis B virus infection

Gamma interferon (IFN-γ) expression plays a crucial role in the control of mammalian hepatitis B virus (HBV) infection. However, the role of duck INF-γ (DuIFN-γ) in the outcome of duck HBV (DHBV) infection, a reference model for hepadnavirus replication studies, has not yet been investigated. This work explored the dynamics of DuIFN-γ expression in liver and peripheral blood mononuclear cells (PBMCs) during resolution of DHBV infection in adolescent ducks in relation to serum and liver markers of virus replication, histological changes and humoral response induction. DHBV infection of 3-week-old ducks resulted in transient expression of intrahepatic preS protein (days 3–14) and mild histological changes. Low-level viraemia was detected only during the first 10 days of infection and was accompanied by early anti-preS antibody response induction. Importantly, a strong increase in intrahepatic DuIFN-γ RNA was detected by real-time RT-PCR at days 6–14, which coincided with a sharp decrease in both viral DNA and preS protein in the liver. Interestingly, liver DuIFN-γ expression remained augmented to the end of the follow-up period (day 66) and correlated with portal lymphocyte infiltration and persistence of trace quantities of intrahepatic DHBV DNA in animals that had apparently completely resolved the infection. Moreover, in infected ducks, a moderate increase was detected in the levels of DuIFN-γ in PBMCs (days 12–14), which coincided with the peak in liver DuIFN-γ RNA levels. These data reveal that increased DuIFN-γ expression in liver and PBMCs is concomitant with viral clearance, characterizing the resolution of infection, and provide new insights into the host–virus interactions that control DHBV infection.

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.

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.

Perforin expression in the gastrointestinal mucosa is limited to acute simian immunodeficiency virus infection

Perforin-mediated cytotoxicity is a major effector function of virus-specific CD8 T cells. We have investigated the expression of perforin in the gut, an important site of simian immunodeficiency virus (SIV) pathogenesis, during experimental SIV infection of rhesus macaques. We observed significant increases in perforin protein and mRNA expression levels in the colons of SIV-infected macaques as early as 21 days after infection. However, during chronic infection, despite ongoing viral replication, perforin expression returned to levels similar to those detected in SIV-naïve animals. These findings demonstrate the presence of a robust perforin-positive response in gastrointestinal CD8 T cells during acute, but not chronic, SIV infection.

The Toll-like receptor 7 (TLR7) agonist, imiquimod, and the TLR9 agonist, CpG ODN, induce antiviral cytokines and chemokines but do not prevent vaginal transmission of simian immunodeficiency virus when applied intravaginally to rhesus macaques

The initial host response to viral infection occurs after Toll-like receptors (TLRs) on dendritic cells (DC) are stimulated by viral nucleic acids (double-stranded RNA, single-stranded RNA) and alpha interferon (IFN-alpha) and IFN-beta are produced. We hypothesized that pharmacologic induction of innate antiviral responses in the cervicovaginal mucosa by topical application of TLR agonists prior to viral exposure could prevent or blunt vaginal transmission of simian immunodeficiency virus (SIV). To test this hypothesis, we treated rhesus monkeys intravaginally with either the TLR9 agonist, CpG oligodeoxynucleotides (ODN), or the TLR7 agonist, imiquimod. Both immune modifiers rapidly induced IFN-alpha and other antiviral effector molecules in the cervicovaginal mucosa of treated animals. However, both CpG ODN and imiquimod also induced proinflammatory cytokine expression in the cervicovaginal mucosa. In the vaginal mucosa of imiquimod-treated monkeys, we documented a massive mononuclear cell infiltrate consisting of activated CD4(+) T cells, DC, and beta-chemokine-secreting cells. After vaginal SIV inoculation, all TLR agonist-treated animals became infected and had plasma vRNA levels that were higher than those of control monkeys. We conclude that induction of mucosal innate immunity including an IFN-alpha response is not sufficient to prevent sexual transmission of human immunodeficiency virus.

Perils at mucosal front lines for HIV and SIV and their hosts

HIV-1 and simian immunodeficiency virus (SIV), as well as their hosts, face perils at mucosal front lines in early infection. At these sites, 'resting' CD4+ memory T cells fuel infection (because they are hosts for virus), depleting CD4+ memory T cells throughout the lymphoid tissues, particularly in the gut, and eliciting an immunosuppressive regulatory T-cell response that impairs host defence. But HIV-1 and SIV also risk elimination at the earliest stage of infection, at the mucosal point of entry, if founder populations of infected cells do not expand sufficiently to establish a self-propagating infection. Microbicides and vaccines could increase these viral vulnerabilities at mucosal front lines.

Deoxycytidyl-deoxyguanosine oligonucleotide classes A, B, and C induce distinct cytokine gene expression patterns in rhesus monkey peripheral blood mononuclear cells and distinct alpha interferon responses in TLR9-expressing rhesus monkey plasmacytoid dendritic cells

To determine if deoxycytidyl-deoxyguanosine oligonucleotides (CpG ODN) can be used effectively as nonspecific inducers of innate immune defenses for preventative or therapeutic interventions in infectious disease models for nonhuman primates, the present study evaluated the response of rhesus monkey peripheral blood mononuclear cells to three different synthetic CpG ODN classes by defining the cytokine gene expression patterns and by characterizing IFN-alpha/beta responses. Depending on the type and dose of CpG ODN used for stimulation, distinct gene expression patterns were induced. CpG ODN class A (CpG-A ODN) and CpG-C ODN, but not CpG-B ODN, were potent inducers of alpha interferon (IFN-alpha), and this response was due to IFN-alpha production by TLR9-positive plasmacytoid dendritic cells. Importantly, there was a dose-dependent increase in IFN-alpha responses to CpG-A ODN but a dose-dependent decrease in IFN-alpha responses by CpG-B ODN. The most sustained IFN-alpha response was induced by CpG-A ODN and was associated with a stronger induction of interferon regulatory factor 7 and the induction of several interferon-stimulated genes. In contrast, and independent of the dose, CpG-B ODN were the weakest inducers of IFN-alpha but the most potent inducers of proinflammatory cytokines. CpG-C ODN induced cytokine gene expression patterns that were intermediate between those of CpG-A and CpG-B ODN. Thus, the different types of CpG ODN induce different post-TLR9 signaling pathways that result in distinct cytokine gene expression patterns. Based on these findings, A and C class CpG ODN, but not B class CpG ODN, may be particularly suited for use as therapeutic or prophylactic antiviral interventions.

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.

Temporal and anatomic relationship between virus replication and cytokine gene expression after vaginal simian immunodeficiency virus infection

The current knowledge about early innate immune responses at mucosal sites of human immunodeficiency virus (HIV) entry is limited but likely to be important in the design of effective HIV vaccines against heterosexual transmission. This study examined the temporal and anatomic relationship between virus replication, lymphocyte depletion, and cytokine gene expression levels in mucosal and lymphoid tissues in a vaginal-transmission model of HIV in rhesus macaques. The results of the study show that the kinetics of cytokine gene expression levels in the acute phase of infection are positively correlated with virus replication in a tissue. Thus, cytokine responses after vaginal simian immunodeficiency virus (SIV) inoculation are earliest and strongest in mucosal tissues of the genital tract and lowest in systemic lymphoid tissues. Importantly, the early cytokine response was dominated by the induction of proinflammatory cytokines, while the induction of cytokines with antiviral activity, alpha/beta interferon, occurred too late to prevent virus replication and dissemination. Thus, the early cytokine response favors immune activation, resulting in the recruitment of potential target cells for SIV. Further, unique cytokine gene expression patterns were observed in distinct anatomic locations with a rapid and persistent inflammatory response in the gut that is consistent with the gut being the major site of early CD4 T-cell depletion in SIV infection.

Efficacy of a SHIV 89.6 proviral DNA vaccine against mucosal SIVmac239 challenge

Sixty percent of rhesus macaques infected with virulence attenuated virus SHIV 89.6 are protected from subsequent intravaginal challenge with pathogenic SIVmac239 [Abel K, Compton L, Rourke T, Montefiori D, Lu D, Rothaeusler K, et al. Simian-human immunodeficiency virus SHIV89.6-induced protection against intravaginal challenge with pathogenic SIVmac239 is independent of the route of immunization and is associated with a combination of cytotoxic T-lymphocyte and alpha interferon responses. J Virol 2003;77(5):3099-118; Miller CJ, McChesney MB, Lu X, Dailey PJ, Chutkowski C, Lu D, et al. Rhesus macaques previously infected with simian/human immunodeficiency virus (HIV) are protected from vaginal challenge with pathogenic SIVmac239. J Virol 1997;71(3):1911-21]. Previously, we have shown that inoculation with a proviral plasmid encoding SHIV 89.6 (pMA SHIV-89.6) results in systemic infection that is delayed compared to SHIV 89.6 virus inoculation [Busch M, Lu D, Fritts L, Lifson JD, Miller CJ. Comparison of virology and immunology in SHIV 89.6 proviral DNA and virus-inoculated rhesus macaques. J Med Primatol 2003;32(4-5):240-6]. We now report that, although monkeys inoculated with pMA SHIV-89.6 or SHIV 89.6 virus had similar plasma anti-SIV binding antibody titers and number of anti-SIV IFN-gamma secreting cells on the day of mucosal SIVmac239 challenge, a smaller proportion of monkeys immunized with pMA SHIV-89.6 were protected from vaginal SIVmac239 challenge compared to monkeys immunized using SHIV 89.6 virus. Protected DNA immunized monkeys had stronger anti-SIV IFN-gamma ELISPOT responses in the acute stage post-challenge than unprotected monkeys. Plasma anti-SIV binding antibody titers and PBMC cytokine responses in the acute stages post-challenge were similar in DNA vaccinated-protected and DNA vaccinated-unprotected monkeys. These results suggest that the delay in systemic infection resulting from delivery of SHIV 89.6 as a plasmid decreased the effectiveness of this live attenuated vaccine.

Puma lentivirus is controlled in domestic cats after mucosal exposure in the absence of conventional indicators of immunity

A high percentage of free-ranging pumas (Felis concolor) are infected with feline lentiviruses (puma lentivirus, feline immunodeficiency virus Pco [FIV-Pco], referred to here as PLV) without evidence of disease. PLV establishes productive infection in domestic cats following parenteral exposure but, in contrast to domestic cat FIV, it does not cause T-cell dysregulation. Here we report that cats exposed to PLV oro-nasally became infected yet rapidly cleared peripheral blood mononuclear cell (PBMC) proviral load in the absence of a correlative specific immune response. Two groups of four specific-pathogen-free cats were exposed to PLV via the mucosal (oro-nasal) or parenteral (i.v.) route. All animals were PBMC culture positive and PCR positive within 3 weeks postinfection and seroconverted without exhibiting clinical disease; however, three or four oro-nasally infected animals cleared circulating proviral DNA within 3 months. Antibody titers reached higher levels in animals that remained persistently infected. PLV antigen-induced proliferation was slightly greater in mucosally inoculated animals, but no differences were noted in cytotoxic T-lymphocyte responses or cytokine profiles between groups. The distribution of virus was predominantly gastrointestinal as opposed to lymphoid in all animals in which virus was detected at necropsy. Possible mechanisms for viral clearance include differences in viral fitness required for crossing mucosal surfaces, a threshold dose requirement for persistence, or an undetected sterilizing host immune response. This is the first report of control of a productive feline or primate lentivirus infection in postnatally exposed, seropositive animals. Mechanisms underlying this observation will provide clues to containment of immunodeficiency disease and could prompt reexamination of vaccine-induced immunity against human immunodeficiency virus and other lentiviruses.

Antiinflammatory profiles during primary SIV infection in African green monkeys are associated with protection against AIDS

T cell activation levels in HIV infection are predictive of AIDS progression. We searched for the immunological correlates of protection against disease progression by studying the early stages of nonpathogenic SIV infection in African green monkeys (SIVagm). The African green monkeys (AGMs) displayed high peak viremias and a transient decline in levels of blood CD4(+) and CD8(+) T cells between days 5 and 17 after infection. A concomitant increase in levels of CD4(+)DR(+), CD8(+)DR(+), and CD8(+)CD28(-) cells was detected. After the third week, T cell activation returned to baseline levels, which suggested a protective downregulation of T cell activation. A very early (24 hours after infection) and strong induction of TGF-beta1 and FoxP3 expression was detected and correlated with increases in levels of CD4(+)CD25(+) and CD8(+)CD25(+) T cells. This was followed by a significant increase in levels of IL-10, whereas IFN-gamma gene upregulation was more transient, and levels of TNF-alpha and MIP-1alpha/beta transcripts did not increase in either blood or tissues. The profiles were significantly different during primary SIV infection in macaques (SIVmac); that is, there was a delayed increase in IL-10 levels accompanied by moderate and persistent increases in TGF-beta levels. Together, our data show that SIVagm infection is associated with an immediate antiinflammatory environment and suggest that TGF-beta may participate in the generation of Tregs, which may prevent an aberrant chronic T cell hyperactivation.

Attenuated poxvirus-based simian immunodeficiency virus (SIV) vaccines given in infancy partially protect infant and juvenile macaques against repeated oral challenge with virulent SIV

An infant macaque model was developed to test pediatric vaccine candidates aimed at reducing HIV transmission through breast-feeding. Infant macaques were given multiple immunizations during the first 3 weeks of life with recombinant poxvirus vaccines expressing simian immunodeficiency virus (SIV) structural proteins Gag, Pol, and Env (ALVAC-SIV or modified vaccinia virus Ankara [MVA]-SIV). After repeated daily oral inoculations with virulent SIVmac251 at 4 weeks of age, significantly fewer ALVAC-SIV-immunized infants were infected compared with unimmunized infants. Monkeys not infected after oral challenge in infancy were rechallenged at 16 months of age or older by repeated weekly oral SIV exposure; unimmunized animals were infected after fewer SIV exposures than were animals vaccinated with ALVAC-SIV or MVA-SIV. When infected, ALVAC-SIV- and MVA-SIV-vaccinated animals also had reduced viremia compared with unimmunized animals. The results of these investigations suggest that immunization of human infants with poxvirus-based HIV vaccine candidates may offer protection against early and late HIV infection through breastfeeding.

Abrogation of attenuated lentivirus-induced protection in rhesus macaques by administration of depo-provera before intravaginal challenge with simian immunodeficiency virus mac239

In nonhuman primate models of acquired immunodeficiency syndrome, live attenuated lentiviruses provide the most reliable protection from systemic and mucosal challenge with pathogenic simian immunodeficiency virus (SIV). Although live attenuated lentiviruses may never be used in humans because of safety concerns, understanding the nature of the protective immune mechanisms induced by live attenuated vaccines in primate models will be useful for developing other vaccine approaches. Approximately 60% of rhesus macaques immunized with nonpathogenic simian-human immunodeficiency virus (SHIV) strain 89.6 are protected from infection or clinical disease after intravaginal (IVAG) challenge with pathogenic SIVmac239. The goal of the present study was to determine whether administration of Depo-Provera before IVAG challenge with SIV decreases the protective efficacy of infection with SHIV89.6. The rate of protection after IVAG challenge with SIVmac239 was significantly lower (P<.05), and the acute postchallenge plasma viral RNA levels were significantly higher (P<.006), in Depo-Provera-treated, SHIV89.6-immunized macaques than in Depo-Provera-naive, SHIV89.6-immunized macaques. In the primate model of sexual transmission of human immunodeficiency virus, treatment with progesterone before IVAG challenge with a pathogenic virus can decrease the efficacy of a model "vaccine."

The functional profile of primary human antiviral CD8+ T cell effector activity is dictated by cognate peptide concentration

Antiviral CD8(+) T cells can elaborate at least two effector functions, cytokine production and cytotoxicity. Which effector function is elaborated can determine whether the CD8(+) T cell response is primarily inflammatory (cytokine producing) or antiviral (cytotoxic). In this study we demonstrate that cytotoxicity can be triggered at peptide concentrations 10- to 100-fold less than those required for cytokine production in primary HIV- and CMV-specific human CD8(+) T cells. Cytolytic granule exocytosis occurs at peptide concentrations insufficient to cause substantial TCR down-regulation, providing a mechanism by which a CD8(+) T cell could engage and lyse multiple target cells. TCR sequence analysis of virus-specific cells shows that individual T cell clones can degranulate or degranulate and produce cytokine depending on the Ag concentration, indicating that response heterogeneity exists within individual CD8(+) T cell clonotypes. Thus, antiviral CD8(+) T cell effector function is determined primarily by Ag concentration and is not an inherent characteristic of a virus-specific CD8(+) T cell clonotype or the virus to which the response is generated. The inherent ability of viruses to induce high or low Ag states may be the primary determinant of the cytokine vs cytolytic nature of the virus-specific CD8(+) T cell response.

High beta-chemokine expression levels in lymphoid tissues of simian/human immunodeficiency virus 89.6-vaccinated rhesus macaques are associated with uncontrolled replication of simian immunodeficiency virus challenge inoculum

Viral suppression by noncytolytic CD8+ T cells, in addition to that by classic antiviral CD8+ cytotoxic T lymphocytes, has been described for human immunodeficiency virus and simian immunodeficiency virus (SIV) infections. However, the role of soluble effector molecules, especially beta-chemokines, in antiviral immunity is still controversial. In an attenuated vaccine model, approximately 60% of animals immunized with simian/human immunodeficiency virus (SHIV) 89.6 and then challenged intravaginally with SIVmac239 controlled viral replication (viral RNA level in plasma, <10(4) copies/ml) and were considered protected (K. Abel, L. Compton, T. Rourke, D. Montefiori, D. Lu, K. Rothaeusler, L. Fritts, K. Bost, and C. J. Miller, J. Virol. 77:3099-3118, 2003). To determine the in vivo importance of beta-chemokine secretion and CD8+-T-cell proliferation in the control of viral replication in this vaccine model, we examined the relationship between viral RNA levels in the axillary and genital lymph nodes of vaccinated, protected (n = 20) and vaccinated, unprotected (n = 11) monkeys by measuring beta-chemokine mRNA levels and protein expression, the frequency of CD8+ T cells expressing beta-chemokines, and the extent of CD8+-T-cell proliferation. Tissues from uninfected (n = 3) and unvaccinated, SIVmac239-infected (n = 9) monkeys served as controls. Axillary and genital lymph nodes from unvaccinated and vaccinated, unprotected monkeys had significantly higher beta-chemokine mRNA expression levels and increased numbers of beta-chemokine-positive cells than did vaccinated, protected animals. Furthermore, the lymph nodes of vaccinated, unprotected monkeys had significantly higher numbers of beta-chemokine(+) CD8+ T cells than did vaccinated, protected monkeys. Lymph nodes from vaccinated, unprotected animals also had significantly more CD8+-T-cell proliferation and marked lymph node hyperplasia than the lymph nodes of vaccinated, protected monkeys. Thus, higher levels of virus replication were associated with increased beta-chemokine secretion and there is no evidence that beta-chemokines contributed to the SHIV89.6-mediated control of viral replication after intravaginal challenge with SIVmac239.