Lack of evidence for the dichotomy of TH1 and TH2 predominance in HIV-infected individuals

Cytokine regulation of HIV replication induced by dendritic cell-CD4-positive T cell interactions

It has been established that human immunodeficiency virus (HIV) replication occurs throughout the course of disease in the lymphoid tissue. We have developed a model system to study the effect of cytokines and other agents on HIV replication using cocultures of DCs and T cells that reflect the cell-to-cell interactions that occur in the microenvironment of lymphoid tissue. Dendritic cells from peripheral blood, when pulsed with small amounts of HIV, induce infection in autologous, unstimulated CD4-positive T cells. Using this system, cytokines, anti-cytokine antibodies, and inhibitors of cellular activation were added to cultures and the effects on cellular proliferation and activation and HIV production were measured. Cytokines that increased T cell proliferation, such as IL-2 and IL-4, enhanced HIV replication, while the effect of IL-12 was more complex. HIV production was inhibited by blocking endogenously produced IL-2, as well as by adding IL-10, which blocks IL-2 secretion, antigen-presenting cell function, and T cell activation. Proinflammatory cytokines induced modest enhancement of viral replication in cocultures of HIV-pulsed DCs and CD4-positive T cells. Thus, using a model of HIV replication that more closely mimics the in vivo microenvironment of lymphoid tissue may allow a better analysis of the effect of cytokines and cytokine networks, as well as agents that modify immune activation on HIV replication.

Role for CD30 in HIV expression

CD30 is a member of the tumor necrosis factor (TNF)-receptor superfamily, whose ligand (CD30L) has been identified on B cells, activated macrophages and a subset of activated T cells. We show here that infection in vitro with human immunodeficiency virus (HIV) of CD4+ T-cell clones generated from HIV-seronegative individuals can enhance the expression of CD30, which often preceeds and is associated with the death of clonal T cells. Furthermore, cross-linking CD30 with an agonistic CD30-specific monoclonal antibody potentiated HIV replication induced by an insolubilized anti-CD3 antibody in T-cell lines generated from HIV-infected individuals. More importantly, paraformaldehyde-fixed CD8+ T-cell clones expressing CD30L enhanced HIV replication in anti-CD3-stimulated allogeneic or autologous HIV-infected CD4+ T-cell lines and such a potentiating effect was inhibited by an anti-CD30L antibody. The anti-CD30L antibody also exerted a suppressive effect on the spontaneous HIV replication occurring in lymph node cells, freshly derived from an HIV-seropositive patient showing CD30 expression in B cells and in a proportion of CD8+ T lymphocytes. Thus, CD30 triggering may play an important role in both HIV replication and the death of HIV-infected CD4+ T cells.

Analysis of apoptosis and a Th1/Th2 phenotype in HIV-infected patients

Lymphocytes from HIV patients, unlike those from normal HIV-negative subjects, underwent apoptosis upon in vitro culture. We found that the percentage of lymphocytes undergoing apoptosis was significantly higher (P = 0.005) in patients with low CD4 cell counts (< 200 CD4 cells/microliter) (60%) than in patients at earlier stage (> 500 CD4 cells/microliter) (35%). Serum IgE levels increased in two of six patients at last stage and in two of five patients at earlier stage. Spontaneous production of both IL-2 and IL-10, by peripheral blood mononuclear cells (PBMC) after 48 h in culture, was greater in HIV-infected subjects and increased with disease progression. IFN-gamma production was greater in HIV-infected subjects but there was no evident change with disease progression. IL-4 production was barely detectable or not detected in both HIV-infected and HIV-negative individuals. These results indicate that spontaneous apoptosis is associated with advanced disease. However, there was no evidence of in vivo switch from the Th1 to Th2 phenotype in HIV-infected patients.

Kinetics of cytokine expression during primary human immunodeficiency virus type 1 infection

In the present study, we have determined the kinetics of constitutive expression of a panel of cytokines [interleukin (IL) 2, IL-4, IL-6, IL-10, interferon gamma (IFN-gamma), and tumor necrosis factor alpha (TNF-alpha)] in sequential peripheral blood mononuclear cell samples from nine individuals with primary human immunodeficiency virus infection. Expression of IL-2 and IL-4 was barely detected in peripheral blood mononuclear cells. However, substantial levels of IL-2 expression were found in mononuclear cells isolated from lymph node. Expression of IL-6 was detected in only three of nine patients, and IL-6 expression was observed when transition from the acute to the chronic phase had already occurred. Expression of IL-10 and TNF-alpha was consistently observed in all patients tested, and levels of both cytokines were either stable or progressively increased over time. Similar to IL-10 and TNF-alpha, IFN-gamma expression was detected in all patients; however, in five of nine patients, IFN-gamma expression peaked very early during primary infection. The early peak in IFN-gamma expression coincided with oligoclonal expansions of CD8+ T cells in five of six patients, and CD8+ T cells mostly accounted for the expression of this cytokine. These results indicate that high levels of expression of proinflammatory cytokines are associated with primary infection and that the cytokine response during this phase of infection is strongly influenced by oligoclonal expansions of CD8+ T cells.

Comparative interleukin (IL-2)/interferon IFN-gamma and IL-4/IL-10 responses during acute infection of macaques inoculated with attenuated nef-truncated or pathogenic SICmac251 virus

Comparison of immune responses to infection by a pathogenic or a nonpathogenic immunodeficiency virus in macaques may provide insights into pathogenetic events leading to simian AIDS. This work is aimed at exploring cytokine expression during infection by simian immunodeficiency virus (SIV). We used semiquantitative reverse transcription-PCR to monitor interleukin (IL)-2/interferon (IFN)-gamma (Th1-like), and IL-4/IL-10 (Th2-like) expression in unmanipulated peripheral blood mononuclear cells (PBMCs), during the acute phase of infection of eight cynomolgus macaques (Macaca fascicularis) with a pathogenic primary isolate of SIVmac251 (full-length nef), and of four other cynomolgus macaques by an attenuated molecular clone of SIVmac251 (nef-truncated). All the monkeys became infected, as clearly shown by the presence of infected PBMCs and by seroconversion. Nevertheless, PBMC-associated virus loads and p27 antigenemia in monkeys infected by the attenuated virus clone remained lower than those observed in animals infected with the pathogenic SIVmac251 isolate. A rise of IL-10 mRNA expression occurred in both groups of monkeys coincident with the peak of viral replication. In monkeys infected with the pathogenic SIVmac251, IL-2, IL-4, and IFN-gamma mRNAs were either weakly detectable or undetectable. On the contrary, animals infected by the attenuated virus exhibited an overexpression of these cytokine mRNAs during the first weeks after inoculation. The lack of expression of these cytokines in monkeys infected with the pathogenic primary isolate may reflect early immunodeficiency.

Modulation of T cell responses to recall antigens presented by Langerhans cells in HIV-discordant identical twins by anti-interleukin (IL)-10 antibodies and IL-12

Decreased antigen (Ag)-specific T cell (TC) proliferation and IL-2 production are detected in all stages of HIV disease. To determine whether dendritic cell dysfunction and/or abnormal cytokine production contribute to HIV-induced immune dysregulation, we studies TC responses to recall Ags (influenza virus and tetanus toxoid) presented by Langerhans cells (LC) in six pairs of HIV-discordant identical twins, and the modulation of these responses by anti-IL-10 (alphaIL-10) mAbs and IL-12. LC from HIV+ twins induced IL-2 comparable to normal LC in cultures containing TC from uninfected twins. In contrast, IL-2 production was markedly decreased in cultures containing TC from HIV+ twins. IL-12 enhanced Ag-specific IL-2 production by TC from two patients with CD4+ counts > 600. In contrast, alphaIL-10 mAbs enhanced IL-2 production in influenza virus-stimulated cultures containing TC from two patients with CD4+ counts < 20. Thus, these findings suggest that immunologic dysfunction of dendritic cells does not contribute to impaired secondary immune responses in HIV+ individuals. Although few patients were studied, partial immune reconstitution in vitro, as demonstrated here, may help to predict those individuals who might benefit from cytokines or antibodies against cytokines as immunotherapy for HIV disease.

Mycobacteria-reactive gamma delta T cells in HIV-infected individuals: lack of V gamma 9 cell responsiveness is due to deficiency of antigen-specific CD4 T helper type 1 cells

Human gamma delta T lymphocytes expressing the variable T cell receptor elements V gamma 9 paired with V delta 2 are activated by antigen derived from Mycobacterium tuberculosis (M. tb.) and presented by antigen-presenting cells (APC). The subsequent proliferation is strictly dependent on the presence of CD4+ TCR alpha beta+ T helper type 1 (Th1) cells producing interleukin-2 (IL-2). In this study, we report that the reactivity of V gamma 9 cells to M. tb. stimulation in vitro was drastically decreased or absent in the majority of the analyzed HIV-1-infected individuals (CDC stages III and IV). We show that the failure of V gamma 9 cells from HIV+ individuals to proliferate following M. tb. stimulation was not due to an intrinsic qualitative or quantitative defect of gamma delta T cells but rather to a deficiency of M. tb.-reactive CD4 Th1 cells. Thus, V gamma 9 responsiveness could be restored if cultures of M. tb.-stimulated T cells from HIV+ donors were reconstituted with one of the following: (i) exogenous IL-2 (ii) purified CD4 T cells from allogeneic donors; or (iii) T cell-depleted APC from allogeneic donors. In the majority of HIV+ patients, the defective Th1 activity of M. tb.-stimulated CD4 T cells could be decreased neither by cytokines known to favor Th1 development (IL-12, interferon-gamma) nor by neutralization of the Th1-suppressing Th2 cytokine IL-10. We suggest that measurement of V gamma 9 cell expansion within M. tb.-stimulated peripheral blood mononuclear cells provides a sensitive assay for the functional capacity of antigen (M. tb.)-specific CD4 Th1 cells in HIV-infected individuals.

Interleukin-2 and human immunodeficiency virus infection: pathogenic mechanisms and potential for immunologic enhancement

A hallmark of human immunodeficiency virus (HIV) infection is the progressive loss of CD4+ T lymphocytes; however, qualitative defects in immune responses occur prior to the precipitous drop CD4+ T cell numbers. One of the first immunologic defects to be described in HIV-infected individuals is a deficiency in interleukin (IL)-2 production. The addition of IL-2 in vitro to cultures of mononuclear cells from HIV-infected individuals partially or completely restored certain defective cellular immune responses. However, production of or addition of IL-2 has also been associated with increased viral replication in infected T cells. These observations underscore the pernicious correlation between immune activation and HIV replication. However, recent in vitro and in vivo studies have provided promising preliminary results suggesting that, at least at certain stages of disease, the benefits of IL-2 mediated immune enhancement may outweigh or override the inductive effects of this cytokine on HIV production.

Candidate HIV type 1 multideterminant cluster peptide-P18MN vaccine constructs elicit type 1 helper T cells, cytotoxic T cells, and neutralizing antibody, all using the same adjuvant immunization

Cytotoxic T lymphocytes and Th1 cells have been suggested to play a critical role in the control of HIV infection. It is therefore considered that a vaccine that induces a strong Th1 response and CTL response would be more efficacious than one that does not in providing protection against infection and progression toward AIDS. In this study we show that immunization with vaccine constructs consisting of multideterminant cluster peptides containing Th epitopes from the HIV-1IIIB envelope colinearly synthesized to peptide 18MN, is capable of inducing a Th1 response in mice and, dependent on this help, both cytotoxic T cell responses and neutralizing antibody toward the homologous strain of HIV. Moreover, the cytotoxic T cell response elicited by immunization with a mixture of cluster peptide-P18MN vaccine constructs was at least as cross-reactive against known viral variant P18 target sequences as a CTL line produced by immunization with a vaccinia construct expressing recombinant gp160 MN. Four adjuvants were compared to optimize both CTL and antibody responses. A single adjuvant formulation of peptide in ISA 51 could elicit all three: Th1 cells, CTLs, and neutralizing antibody. Thus, immunization directed toward the development of a cytotoxic T cell response does not preclude the development of neutralizing antibody and vice versa, i.e., the responses are not mutually exclusive. The immunization protocol described here should be directly applicable for study in clinical trials aimed at HIV-1 immunotherapy or prophylaxis.

Interleukin 1 beta, interleukin 6, tumor necrosis factor alpha, and interleukin 10 responses in peripheral blood mononuclear cells of cynomolgus macaques during acute infection with SIVmac251

HIV infection ultimately leads to AIDS, despite the immune responses elicited soon after infection. In addition to the observed changes in lymphoid cell subsets, alteration of the cytokine network most likely accompanies and/or contributes to the lack of protective immune responses. In an attempt to delineate the early events in the immune response to lentivirus infection, we have sequentially monitored levels of proinflammatory (IL-1 beta, IL-6, and TNF-alpha) and antiinflammatory (IL-10) cytokine mRNAs in PBMCs of cynomolgus macaques during primary SIVmac infection. Eight monkeys were infected i.v. with 4 AID50 of cell-free SIVmac251. All monkeys seroconverted between days 16 and 21 postinfection (p.i.), and had detectable peripheral viremia. The viral load peaked between days 12 and 16 p.i., and fell sharply thereafter. A marked increase in the expression of IL-6 mRNA was observed in all macaques during the first weeks following infection. An increase in the levels of expression of IL-1 beta, TNF-alpha, and IL-10 mRNA was also determined in six, six, and five of the eight monkeys, respectively. While IL-6, TNF-alpha, and IL-10 increased transiently, increased levels of IL-1 beta mRNA expression were sustained over 44 days in most monkeys.

Effect of HIV infection on the frequency of cytokine-secreting cells in human peripheral blood

A selective decrease in type 1 cytokine secretion by in vitro stimulated peripheral blood cells is reportedly associated with disease progression in HIV-infected individuals. To examine whether a similar change in cytokine secretion occurs under physiologic conditions in vivo, sensitive and specific ELIspot assays were used to compare the phenotype and frequency of PBMC spontaneously producing interleukin (IL)-2, IL-4, IL-10, and interferon-gamma (IFN-gamma) in 83 HIV-infected subjects and 60 normal controls. Phenotypic analysis of freshly isolated cytokine-secreting cells showed that T cells were the primary source of IL-2, IL-4, and IFN-gamma while CD14+ macrophages/monocytes were the dominant source of IL-10 in vivo. The number of peripheral blood mononuclear cells (PBMC) spontaneously secreting both type 1 and type 2 cytokines was significantly reduced in HIV-infected patients versus controls. The magnitude of this decrease did not correlate with disease severity. Changes in IL-2-secreting cell number correlated with CD4 count, while changes in the frequency of IFN-gamma-secreting cells correlated with disease duration. These findings do not support the contention that a selective reduction in type 1 cytokine production correlates with disease progression.

Characterization of T cell subsets involved in the production of IFN-gamma in asymptomatic HIV-infected patients

Cells capable of interferon (IFN)-gamma synthesis following mitogenic stimulation can be detected and quantified by a recently developed immunofluorescence assay and flow cytometric analysis. The production of IFN-gamma was investigated in a cohort of 20 asymptomatic human immunodeficiency virus (HIV)-seropositive patients with normal numbers of CD4+ lymphocytes, and in 10 healthy subjects. About 60% of asymptomatic stage A1 patients had increased percentages of blood lymphocytes capable of IFN-gamma synthesis, as compared to healthy subjects. The difference reflected the relatively higher numbers of CD8+ cells, in particular the CD8+ T cell subset lacking CD28 antigen expression. The strong correlation between the CD4+/CD8+ ratio and the CD8+CD28+/CD8+CD28- ratio suggests either a role for CD4+ cells in controlling the CD28+ phenotype or a role for CD8+CD28- cells in the decline of CD4+ lymphocytes. The peculiar ability of CD8+CD28- cells to produce high amounts of IFN-gamma, as compared to CD8+CD28+ cells, supports the hypothesis that the CD8+CD28- lymphocytes constitute a population that is functionally distinct from their double-positive counterparts.

Toward an understanding of the correlates of protective immunity to HIV infection

Considerable progress has been made recently in understanding the genetic, immunologic and virologic factors in human immunodeficiency virus (HIV)-infected individuals who either rapidly progress or do not progress to acquired immunodeficiency syndrome (AIDS). In addition, detection of HIV-specific immune responses in HIV-negative individuals who have been exposed to the virus multiple times suggests that natural immune responses to HIV may be protective in rare individuals. Understanding the correlates of protective immunity to HIV infection is critical to efforts to develop preventive HIV vaccines as well as to determine the feasibility of treating HIV infection by boosting immunity to HIV.

Immunological and virological markers of HIV-disease progression

This review, based upon scientific literature, evaluates a number of immunological and virological markers for their usefulness as prognostic indicators for progression of HIV disease. The most widely studied marker, the CD4 positive T lymphocyte count, is perhaps the best single indicator of stage of illness. Serum factors such as neopterin and beta-2 microglobulin, alone and in combination with CD4 cell counts, have been shown to have good predictive value. Measurement of viral burden by quantification of viral RNA levels in plasma and immune cells also holds promise for following disease progression. It is recommended that a combination of these factors be monitored in evaluating stage of illness and responses to therapy in HIV-infected persons.

T helper type 1/T helper type 2 cytokines and T cell death: preventive effect of interleukin 12 on activation-induced and CD95 (FAS/APO-1)-mediated apoptosis of CD4+ T cells from human immunodeficiency virus-infected persons

Human immunodeficiency virus (HIV) infection leads to a progressive loss of CD4+ T helper (Th) type 1 cell-mediated immunity that is associated with defective in vitro CD4+ T cell proliferation and abnormal T cell death by apoptosis in response to T cell receptor (TCR) stimulation. Quantification of interleukin (IL)-2, interferon gamma, IL-4, IL-5, and IL-10 secretion by immunoassays, and of interferon gamma, IL-4 and IL-10 messenger RNA expression by competitive reverse transcriptase polymerase chain reaction after in vitro stimulation of the TCR revealed a similar Th1 cytokine profile in T cells from HIV-infected persons and from controls. These data indicated that the loss of CD4+ Th1 cell function in HIV-infected persons is not related to a Th1 to Th2 cytokine switch as previously proposed, but to a process of activation-induced death of CD4+ Th1 cells. Despite the absence of elevated levels of Th2 cytokines, apoptosis of CD4+ T cells, but not of CD8+ T cells, was prevented in vitro by antibodies to IL-10 or IL-4, two Th2 cytokines that downregulate Th1 cell responses, or by the addition of recombinant IL-12, a cytokine that upregulates Th1 functions. TCR-induced apoptosis of T cell hybridomas and preactivated T cells has been shown to involve the CD95 (Fas/Apo-1) molecule. CD4+ and CD8+ T cells from HIV-infected persons expressed high levels of the CD95 molecule, and, in contrast to T cells from controls, were highly sensitive to antibody-mediated CD95 ligation, which induced apoptosis in a percentage of T cells similar to that induced by TCR stimulation. As TCR-induced apoptosis, CD95-mediated apoptosis of CD4+ T cells, but not of CD8+ T cells, was prevented by the addition of recombinant IL-12. Together, these findings suggest that apoptosis of CD4+ T cells from HIV-infected persons involves an abnormal sensitivity to CD95 ligation, and to TCR stimulation in the presence of normal levels of Th2 cytokines. The preventive effect of IL-12 on both mechanisms has potential implications for the design of immunotherapy strategies aimed at the upregulation of CD4+ Th1 cell functions in AIDS.

Immunosuppressive retroviral peptides: cAMP and cytokine patterns

The mechanism(s) by which retroviral proteins exert immunosuppressive influences has remained enigmatic. Here, Soichi Haraguchi, Robert Good and Noorbibi Day propose that induction of intracellular cAMP by a synthetic, immunosuppressive, retroviral envelope peptide causes a shift in the cytokine balance, leading to suppression of cell-mediated immunity by upregulation of interleukin 10 (IL-10) and downregulation of IL-2, IL-12 and tumor necrosis factor alpha production. This may be a crucial step towards generation of immune dysfunction.

Dysregulated production of interleukin-10 (IL-10) and IL-12 by peripheral blood lymphocytes from human immunodeficiency virus-infected individuals is associated with altered proliferative responses to recall antigens

The loss of immune function following infection with human immunodeficiency virus (HIV) may result from altered production of immunoregulatory cytokines such as interleukin-10 (IL-10) and IL-12. In this study, we analyzed IL-10 and IL-12 production by mitogen-stimulated peripheral blood mononuclear cells (PBMC) from HIV+ individuals and correlated their levels with proliferative responses to the recall antigens HIV p25 and influenza virus. We report two distinct groups of HIV+ patients. One group produced small amounts of IL-10, had PBMC that proliferated in response to recall antigens, and demonstrated enhanced recall antigen-induced proliferation upon addition of anti-IL-10 antibodies and/or IL-12. Conversely, the second group produced high levels of IL-10, had PBMC that failed to proliferate to recall antigens, and did not demonstrate enhanced proliferation upon addition of anti-IL-10 antibodies and/or IL-12. Mitogen-stimulated PBMC from both groups produced significantly lower levels of IL-12 than did those from HIV- controls. Analysis of the source of the IL-10-producing cell subset in PBMC demonstrated that in HIV+ individuals, IL-10 is produced by monocytes, while in HIV- controls, it is produced by both T cells and monocytes. Taken together, our results suggest that monocytes from HIV+ individuals secrete decreased amounts of IL-12, a Th1-type cytokine, which may lead to the development of Th2-type responses characterized by high IL-10 secretion and immune dysfunction.

Ligation of either CD2 or CD28 rescues CD4+ T cells from HIV-gp120-induced apoptosis

Temporal or quantitative imbalance in signals delivered to T cells via T cell antigen receptor (TCR), the CD4 co-receptor, and accessory molecules can lead to anergy, apoptosis, or both. This has been observed following ligation of CD4 by HIV gp120 prior to TCR occupancy. The ability of molecules such as CD2 and CD28, interacting with their ligands LFA-3 and B7, to provide signals that protect T cells from the induction of anergy, has been reported. Here, we demonstrate that ligation of CD2 and CD28 in conjunction with TCR occupancy rescue T cells that have been programmed for apoptotic death by prior CD4 ligation to gp120. This appears to be the result of augmented interleukin-2 and interleukin-4 release by the T cells following these molecular interactions. In conclusion, our results suggest that an impairment of antigen-presenting accessory cell functions could favor gp120-mediated apoptosis in HIV-uninfected cells.

Cytokine interactions in human immunodeficiency virus-infected individuals: roles of interleukin (IL)-2, IL-12, and IL-15

Cytokines have been shown to be powerful regulators of the immune response. In this study, we analyze the effect that the newly recognized cytokine interleukin (IL)-15 has on proliferation and cytokine induction using peripheral blood mononuclear cells (PBMCs) and purified CD4+ T cells from patients infected with human immunodeficiency virus (HIV) who are at various stages in their disease. We observed that IL-15 enhances the proliferative response in a dose-dependent manner from PBMCs of HIV-infected individuals when stimulated by polyclonal mitogen, tetanus toxoid, or HIV-specific antigen. The effects of exogenous IL-15 are substantially diminished by adding a neutralizing antibody to the beta chain of the IL-2 receptor. Moreover, the ability of IL-15 to increase proliferation is enhanced by the presence of endogenous IL-2 produced in the cultures. The effect that exogenous IL-15 had on IL-2, IL-4, and interferon (IFN)-gamma induction from PBMC's or CD4+ T cells in response to mitogen or tetanus toxoid was also examined. This was compared to the effect that exogenous IL-2 and IL-12 had under the same conditions. Addition of IL-2 or IL-15 to short-term in vitro cultures of either PBMCs or CD4+ T cells had little effect on IL-2, IL-4, or IFN-gamma production. By contrast, IL-12 caused substantial enhancement of both IL-2 and IFN-gamma production from these cultures. The role that endogenous cytokines have on IFN-gamma induction was also studied. Addition of a neutralizing antibody to the alpha chain of the IL-2 receptor or IL-12 to antigen stimulated cultures caused a striking decrease in IFN-gamma production. Neutralization of endogenous IL-15 also resulted in diminished IFN-gamma production from cultures stimulated with mitogen. IL-4 and IFN-gamma protein production by PBMCs and CD4+ T cells stimulated with mitogen was assessed to see if we could detect a specific bias of cytokine production. Small amounts of IL-4 were detected from CD4+ T cells but not PBMCs from most individuals tested. IFN-gamma and IL-2, however, were also produced from these same cultures. These results further elucidate the mechanism of cytokine regulation in HIV-infected individuals, and they provide evidence that IL-15 may be a useful immune modulator.

Expression of IL-10, IL-4 and interferon-gamma in unstimulated and mitogen-stimulated peripheral blood lymphocytes from HIV-seropositive patients

Infection of immune cells with HIV induces dysregulation of cytokines which may play a vital role in HIV pathogenesis. We analysed the expression of T helper type 1 (Th1) (interferon-gamma (IFN-gamma)) and Th2 (IL-4, IL-10) type cytokines in peripheral blood lymphocytes (PBL) from HIV+ patients. The semiquantitative reverse transcriptase polymerase chain reaction (RT-PCR) analysis revealed that IFN-gamma mRNA in unstimulated PBL was significantly decreased and IL-10 mRNA was significantly upregulated in patients with < 400 CD4+ T cells/mm3 (n = 30) as compared to patients with > 400 CD4+ T cells/mm3 (n = 6) and normal controls (n = 16). In addition, IL-10 mRNA levels were inversely associated with IFN-gamma expression. Similar results were obtained by measuring IL-10 production in the supernatants of PBL cultured in vitro without stimulation by employing an enzyme immunosorbent assay (ELISA). However, the levels of IL-4 and IFN-gamma produced by unstimulated PBL were undetectable by ELISA. Mitogen stimulation of PBL revealed two groups of HIV+ individuals based on IL-10 production. PBL from one set of individuals produced low levels of IL-10 (low IL-10 producers) whereas the other group produced IL-10 comparable to that of normal controls (IL-10 producers). Production of IL-4 was significantly reduced in HIV+ individuals with < 400 CD4+ T cells/mm3 as compared to the normal controls. However, ability to produce IFN-gamma by mitogen-stimulated total PBL and CD4+ purified cells was not impaired in HIV+ individuals. These results suggest that unstimulated and mitogen-stimulated PBL of HIV+ individuals exhibit dysregulation of Th2 type cytokines which may play a role in HIV immunopathogenesis.

Therapeutic potentiation of the immune system by costimulatory Schiff-base-forming drugs

Immune responses are orchestrated by CD4 T lymphocytes, which receive a cognitive signal when clonally distributed receptors are occupied by major histocompatibility complex (MHC) class II-bound peptides on antigen-presenting cells (APCs). The APCs provide costimulatory signals, through macromolecules such as CD80, that regulate outcomes in terms of T-cell activation or anergy. We have studied essential complementary chemical events in the form of Schiff base formation between carbonyls and amines that are constitutively expressed on presenting cell and T-cell surfaces and provide a new target for manipulation of immune responses. Here we show that small Schiff base-forming molecules can substitute for the physiological donor of carbonyl groups and provide a costimulatory signal to CD4 Th-cells through a mechanism that activates clofilium-sensitive K+ and Na+ transport. One such molecule, tucaresol, enhances CD4 Th-cell responses, selectively favouring a Th1-type profile of cytokine production. In vivo tucaresol potently enhances CD4 Th-cell priming and CD8 cytotoxic T-cell priming to viral antigens, and has substantial therapeutic activity in murine models of disease.

Cytokines in the acquired immunodeficiency syndrome and other infectious diseases

The pathogenesis of several infectious diseases is frequently related not only to their etiological agents of viral, bacterial, or parasitic nature, but also to the host immune response. Both inflammatory responses and specific immune responses to the invading microorganisms are controlled by complex networks of intercellular signalling molecules, namely cytokines. This rapidly growing family of mediators includes lymphokines, interleukins, and molecules such as tumor necrosis factors and interferons. Patterns of cytokine production from antigen- or allergen-specific T lymphocytic cell clones have been identified, firstly in animal models and subsequently in man, and are commonly referred to as TH0, TH1, and TH2 profiles. The predominance of one of these profiles strongly influences the type of immune response (humoral versus cellular) and, at least in some experimental models, whether the immune response is protective or harmful. This is most convincingly demonstrated in models of parasitic diseases, but has also been hypothesized to be involved in the pathogenesis of human immunodeficiency virus infection and the acquired immunodeficiency syndrome. Earlier studies on human immunodeficiency virus infection revealed that the replicative capacity of this retrovirus, like the herpes viruses, is strongly influenced by the cytokine milieu of infected cells. Transcriptional and post-transcriptional regulation of human immunodeficiency virus expression by human cytokines are examples of the complex interdigitation of viruses with the host immune system.

Th1/Th2-like immunity and resistance to herpes simplex labialis

To investigate potential immunologic mechanisms of resistance to recurrent herpes simplex labialis, we assayed serum antibody titers and cultured peripheral blood mononuclear cell (PBMC) cytokine production among patients with a history of frequent episodes (H+S+), herpes simplex virus (HSV)-seropositive individuals without a history of herpes labialis (H-S+) and HSV-seronegative persons (H-S-). In addition, H+S+ patients were exposed to experimental ultraviolet radiation (UVR) on the lips and the immunologic assay results compared among those who developed experimental lesions and those who did not. H+S+ patients were found to have higher median serum titers of HSV antibody and trends to lower levels of HSV-specific PBMC IFN-gamma and IL-2 than H-S+ control patients (123 vs 66, P = 0.04; 424 vs 548 pg/ml, P = 0.08; 14 vs 26 pg/ml, P = 0.14, respectively). Correlation of the results with the occurrence of experimental lesions showed the inverse: the subgroup of H+S+ patients with UVR-induced lesions had lower titers of antibody and trends to higher levels of IFN-gamma and IL-2 than H+S+ patients who could not be induced (93 vs 149, P = 0.02; 501 vs 347 pg/ml, P = NS; 26 vs 11 pg/ml, P = NS, respectively). The size and duration of UVR-induced lesions showed positive correlations with IFN-gamma and IL-2 levels (r = 0.60-0.67, P = 0.02-0.04). Although the small number of patients limited the power of this study, the overall pattern of the findings suggests that a Th1-like cytokine response (IFN-gamma and IL-2 production) may be associated with resistance to naturally occurring episodes of herpes labialis. The development and severity of experimental UVR-induced herpes labialis appears to be regulated differently and may involve an immunopathologic mechanism.

Priming for high interferon-gamma production induced by interleukin-12 in both CD4+ and CD8+ T cell clones from HIV-infected patients

HIV-infected patients are defective in their ability to produce interleukin (IL)-12 in vitro in response to pathogenic bacteria and parasites. IL-12 enhances the patient's depressed natural killer cell cytotoxic activity, peripheral blood lymphocyte production of interferon-gamma (IFN-gamma), and proliferative T cell response in vitro to recall antigens, HIV antigens, alloantigens, and mitogens. However, these effects represent short-lived responses and imply the need for chronic IL-12 therapeutic administration in the clinical setting. To identify any long-term effects of IL-12 on T cell differentiation toward Th1 cells, peripheral blood T cells from 10 HIV-infected patients at different stages of disease were cloned by limiting dilution in the presence or absence of IL-12 and tested for cytokine production in response to stimulation with anti-CD3 antibodies and phorbol diesters IL-12 present during the first 2 wk of clonal expansion determined a stable severalfold enhancement on the ability of both CD4+ and CD8+ clones to produce IFN-gamma. Because priming for high IFN-gamma production is probably the most important mechanism by which IL-12 induces generation of efficient T helper type 1 (Th1) cells, these results suggest the possibility that IL-12 treatment in vivo of HIV-infected patients may stimulate a protective Th1 response against opportunistic pathogens and possibly HIV itself.

Role of apoptosis in HIV disease pathogenesis

After approximately one and a half decades of intensive studies, the exact mechanisms to explain HIV-mediated cytopathicity are still enigmatic and need closer scrutiny. There has been a dichotomy between virological and immunological viewpoints in understanding HIV-mediated cytopathicity, the former emphasizing a killing of infected cells by HIV-1 and the latter emphasizing indirect mechanisms wherein HIV or its soluble component(s) alter CD4 T-cell function and induce susceptibility to apoptosis. Accumulating evidence points to the notion that apoptosis might be a major contributor to the depletion of CD4 T-cells in HIV infection. This review summarizes current information about the regulatory mechanisms of T-cell apoptosis and the role of apoptosis in HIV pathogenesis with the goal of providing an integrated view of HIV cytopathicity.

Sicca syndrome in patients infected with the human immunodeficiency virus

PURPOSE

To investigate an association of the severity of the human immunodeficiency virus (HIV) disease with decreased tear production in a controlled setting.

PATIENTS AND METHODS

Seventy-two patients (144 eyes) and 30 age- and sex-matched control subjects (60 eyes) were studied prospectively. Tear production was measured using the Schirmer I test (measured in millimeters after 5 minutes). Patients were classified into three clinical groups: asymptomatic HIV infection, lymphadenopathy syndrome (LAS) or acquired immune deficiency syndrome (AIDS)-related complex (ARC), and AIDS. Additionally, patients were classified according to the CD4+ lymphocyte count.

RESULTS

Tear production (mean +/- standard deviation) did not differ (P = 0.32) among eyes of patients with asymptomatic HIV infection (17.1 +/- 10.8; n = 14), LAS or ARC (18.3 +/- 10.3; n = 70), and AIDS (20.7 +/- 10.3; n = 60). In addition, mean tear production was not decreased significantly when comparing each clinical group with the control subjects (17.8 +/- 4.4). However, the relative frequency of eyes with significantly decreased tear production (< 9 mm) was 23.6% in all 144 eyes. In addition, the relative frequency of significantly decreased tear production did not differ (P = 0.52) between eyes of patients with asymptomatic HIV infection (35.7%), LAS or ARC (21.4%), and AIDS (24.1%). In addition, the relative frequency of significantly decreased tear production did not differ (P = 0.30) between eyes of patients with a CD4+ count of more than 400 cells/microliters (23.1%; n = 26), 400 to 200 cells/microliters (31.3%; n = 48), 200 to 50 cells/microliters (14.3%; n = 42), and less than 50 cells/microliters (21.4%; n = 28).

CONCLUSION

The authors data show that decreased tear production occurs in approximately 20% to 25% of patients with HIV infection. This increased frequency of decreased tear production is not associated with the CD4+ count, or related to the severity of HIV disease, respectively. The possibility of an autoimmune-like pathogenesis of abnormalities of tear production in patients with HIV infection should be studied intensively.

Down-modulation of CD4+ T helper type 2 and type 0 cells by T helper type 1 cells via Fas/Fas-ligand interaction

Fas was recently demonstrated to be the major target molecule engaged by CD4+ cytolytic T lymphocytes (CTL). We examined Fas expression on various cloned T cell subpopulations and their susceptibility to lysis by CD4+ or CD8+ CTL. A reciprocal relationship in Fas and Fas-ligand expression was observed in CD4+ T helper (Th)1- and Th2-type clones, and Fas mRNA was predominantly detected in Th2 clones, whereas Fas-ligand mRNA was principally found in Th1 clones. The two Th0 clones tested expressed both Fas and Fas-ligand, but only one exhibited cytolytic activity, whereas both were sensitive to CD4-mediated lysis. A functional consequence of the inverse Fas-Fas-ligand expression pattern was that Th2 and Th0 cells were sensitive to lysis by both Th1 CD4+ CTL and a CD8+ CTL clone in a Fas-dependent manner. These results suggest that cytolytic CD4+ Th1 cells may play an immunomodulatory role, regulating a Th2/Th0 response by Fas-mediated lysis.

Activation of HIV expression by CD30 triggering in CD4+ T cells from HIV-infected individuals

CD30 is a member of the tumor necrosis factor receptor superfamily, preferentially expressed by T cells producing type 2 helper (Th2) cytokines, whose ligand (CD30L) has been identified on B cells, activated macrophages, and a subset of activated T cells. We show here that cross-linking CD30 with an agonistic CD30-specific monoclonal antibody, as well as with CD30L+ CD8+ T cell clones or CD30L+ B cells, enhanced HIV replication in CD4+ T cells from HIV-infected individuals, and such a potentiating effect was inhibited by anti-CD30L antibody. The anti-CD30L antibody also exerted a suppressive effect on spontaneous HIV replication occurring in lymph node cells from an HIV-sero-positive patient, showing CD30L expression by both B and CD8+ T lymphocytes. Thus, CD30 triggering by CD30L-expressing cells may plan an important role in the activation of HIV expression from latently infected CD4+ T cells.

Cytokine immunotrapping: an assay to study the kinetics of production and consumption or degradation of human interferon-gamma

With the aim of determining the rate of cytokine production, we have investigated immunoassay conditions which prevent consumption/degradation. These assays, termed cytokine immunotrapping assays (CITA), are based on early capturing of cytokines secreted during cell culture by immobilised or soluble mAbs and a recently described chemiluminescent immunoassay. Here we describe assay conditions using IFN-gamma as a prototype cytokine. For production of IFN-gamma, PBMC, purified CD4+ or CD8+ T cells, or diluted whole blood were cultured with different T cell stimulating agents. Polystyrene macrobeads precoated with an anti-IFN-gamma mAb were put in culture and after a defined incubation period, a dimethyl acridinium ester (DMAE)-labelled second anti-IFN-gamma mAb and sodium azide were added into the culture for additional 24 h. The beads were washed and chemiluminescence signals determined in a luminometer. Trapping experiments were also performed with the beads or the soluble mAbs alone. Irrespective of the configuration, IFN-gamma concentrations measured in trapping conditions were always higher (3-20-fold) than in conventional cultures. By using the best trapping combination, i.e. both bead-mAb1 and DMAE-mAb2 added at the start of culture (single step), it was possible to detect IFN-gamma production as early as 2 h. Also, IFN-gamma secreted by less than 500 PBMC or whole blood cells could be detected within 24 h. When purified CD4+ or CD8+ cells were used instead of PBMC, a reduction of the trapping effect was observed. Conversely, addition of monocytes to purified T cells increased the trapping factor suggesting that a substantial amount of IFN-gamma was consumed or degraded both by CD14+ cells as well as T cells in culture. Preliminary results show that this assay is also suitable for the early detection of IL-1 and IL-4 which are known to be more tightly regulated. Thus, the new principle described here is expected to be useful in clinical settings where both the time and amounts of material are limited to investigate the role of cytokines in particular disease.

T helper cell dichotomy to Candida albicans: implications for pathology, therapy, and vaccine design

Acquired immunity to Candida albicans is believed to prevent mucosal colonization of adult immunocompetent individuals from progressing to symptomatic infection. Resistance to disease appears to correlate with the detection of delayed-type hypersensitivity responses in vivo and a T helper type 1 (Th1) cytokine secretion profile in vitro. Cellular immunodeficiency, particularly HIV infection, greatly increases the risk of mucosal infection, confirming that CD(4+)-cell-directed immunity is effective locally in controlling infectivity of the yeast. While Th1-type CD4+ cell activation resulting in phagocyte-dependent immunity clearly represents an important mechanism of anticandidal resistance, clinical observations suggest that Th2-type CD4+ cell reactivity may be triggered by Candida antigens in several disease states, including symptomatic infections and immunopathology. This may imply that a Th1-type pattern of reactivity characterizes the saprophytic yeast carriage and resistance to disease by healthy humans, whereas Th2-type responses would be mostly associated with pathology. Moreover, Candida-specific T helper responses, namely humoral and cell-mediated immunity, appear to be reciprocally regulated, as typically occurs in experimental models of parasitic and retroviral infection, where the Th1/Th2 paradigm of acquired immunity has been best characterized. Recent studies, besides providing direct evidence for the occurrence of cross-regulatory Th1 and Th2 responses in mice with candidiasis, emphasize the potential of cytokine/anticytokine therapy for recruiting Candida-specific responses toward protective, Th1-type CD4+ cell reactivity. At the same time, these studies call attention to the possible consequences of C. albicans infection for immunopathology, allergy, and coinfection.

Morphological changes in lymph nodes and expression of VCAM1 and cytokines at the late stages of SIV-induced disease in rhesus monkeys

Four patterns of structural alterations were found in lymph nodes (LNs) from rhesus monkeys 17 to 34 months after infection with simian immunodeficiency virus (SIV-mac251). SIV p27gag antigen and viral particles were localized either between the processes of follicular dendritic cells (FDCs) or in the cytoplasm of macrophages. In hyperplastic follicles, enlarged germinal centres contained numerous Ki67+ proliferating centroblasts which were rather rare in light zones occupied by the CD23+ FDC network. Involuted follicles contained a small number of Ki67+ centroblasts and the CD23 labelling was limited to a very small apical zone. A correlation was found between the morphological characteristics of the follicles (hyperplasia-involution) and the level of expression of the vascular cell adhesion molecule 1 (VCAM1) on FDCs. A gradient in VCAM1 intensity with no expression in the subcapsular-intermediary sinuses, low membrane labelling in the mantle and strong expression in the FDC network was observed. IL1 alpha+ and IL6+ (interleukin) cells (lymphocytes and macrophages) were detected in the mantle, the interfollicular area and the medulla of LNs. Expression of the tumour necrosis factor alpha and ultrastructural markers of interferon alpha production were found in a few FDC and macrophages. Our findings indicate a close relationship between the morphofunctional properties of FDC and the LN structure in SIV infection.

Immune activation is a dominant factor in the pathogenesis of African AIDS

The AIDS epidemic in Africa is very different from the epidemic in the West. As suggested here by Zvi Bentwich, Alexander Kalinkovich and Ziva Weisman, this appears to be primarily a consequence of the over-activation of the immune system in the African population, owing to the extremely high prevalence of infections, particularly helminthic, in Africa. Such activation shifts the cytokine balance towards a T helper 0/2 (Th0/2)-type response, which makes the host more susceptible to infection with human immunodeficiency virus (HIV) and less able to cope with it.

Selective decrease in human immunodeficiency virus type 1 (HIV-1)-induced alpha interferon production by peripheral blood mononuclear cells during HIV-1 infection

We previously reported that human immunodeficiency virus type 1 (HIV-1), herpes simplex virus (HSV), and Sendai virus induce higher levels of alpha interferon (IFN-alpha) in blood dendritic cells than in monocytes of healthy donors. In the present study, the levels of IFN-alpha induced by T-cell tropic (IIIb and RF) and monocytotropic (BaL) strains of HIV-1 and by HSV were significantly decreased in peripheral blood mononuclear cells (PBMCs) derived from subjects with asymptomatic and symptomatic HIV-1 infection. In contrast, Sendai virus, a paramyxovirus that induces proportionally more IFN-alpha in monocytes and B cells than do either HIV-1 or HSV, stimulated normal levels of IFN-alpha in PBMCs from the HIV-1-infected men. The IFN-alpha produced by PBMCs from the HIV-1-seropositive subjects was partially acid labile, whereas the IFN-alpha produced by PBMCs from the HIV-1-seronegative donors was acid stable. We hypothesize that there is a selective defect in IFN-alpha production by peripheral blood dendritic cells, whereas the host retains the IFN-alpha-producing capacity of monocytes and B lymphocytes. The loss of IFN-alpha production in response to HIV-1, herpesviruses, and possibly other pathogens could contribute to the progression of HIV-1 infection and to the development of AIDS.

Role of interferons and other cytokines in the regulation of the immune response

Cytokines represent the major factors involved in the communication between T cells, macrophages and other immune cells in the course of an immune response to antigens and infectious agents. A number of studies on mouse and human T helper (Th) clones have recently provided extensive evidence for the existence of different activities exhibited by Th cells (called Th1 and Th2), which was apparently inferred from the profile of cytokine secretion. The Th1-type immune response is generally associated with IgG2a production and the development of cellular immunity, the Th2-type response with IgE production, eosinophils and mast cell production. This review focuses on the role of different cytokines produced by macrophages (especially interferons (IFNs), TNF-alpha, IL-10 and IL-12) or T cells (IFNs, IL-2, IL-4, IL-10, IL-13 and TGF-beta) in macrophage-T cell interactions and the cytokine relevance in the differentiation of Th cells towards the Th1 or Th2 type of immune response. Th1-derived cytokines (IFN-gamma, IL-2, TNF-alpha) favor macrophage activation, whereas the Th2 cytokines (IL-4, IL-10, IL-13) exhibit suppressive activities on macrophage functions. A key role in the differentiation towards the Th1-type response is now attributed to IL-12, a recently described cytokine produced mainly by macrophages. Its production can be upregulated by IFN-gamma and is inhibited by IL-10 and IL-4. All this emphasizes the importance of macrophage-cytokine interactions in determining the type of immune response. This article also aims to review recent data concerning the roles of IFNs alpha/beta (type I) and IFN-gamma (type II) in the regulation of the immune response. While there is much information on the regulatory effects of IFN-gamma (also called "immune IFN") on the immune response, little is so far known of the role of type I IFNs. These cytokines, originally described as simple antiviral substances, are now taken to be important regulators of the immune response. Recent data indicate that these molecules (especially IFNs-alpha) specifically promote the differentiation towards the Th1-type response. The stimulatory effects of IFN-alpha on the generation of the Th1-type response may be involved in its therapeutic effects in some human diseases, including early AIDS, hypereosinophilia and certain tumors.(ABSTRACT TRUNCATED AT 400 WORDS)

Induction of interleukin-10 by human immunodeficiency virus type 1 and its gp120 protein in human monocytes/macrophages

In this study, we evaluated the effects of human immunodeficiency virus type 1 (HIV-1) and its gp120 protein on interleukin-10 (IL-10) expression in cultured human monocytes/macrophages. Infection of either 1-day monocytes or 7-day monocyte-derived macrophages with HIV-1 strain Ba-L resulted in clear-cut accumulation of IL-10 mRNA at 4 and 24 h. Likewise, treatment of these cells with recombinant gp120 induced IL-10 mRNA expression and caused a marked increase in IL-10 secretion. Monoclonal antibodies to gp120 strongly inhibited recombinant gp120-induced IL-10 secretion by monocytes/macrophages. Moreover, the addition of IL-10 to monocytes/macrophages resulted in a significant inhibition of HIV-1 replication 7 and 14 days after infection. On the whole, these results indicate that HIV-1 (possibly through its gp120 protein) up-regulates IL-10 expression in monocytes/macrophages. We suggest that in vivo production of IL-10 by HIV-primed monocytes/macrophages can play an important role in the early response to HIV-1 infection.

CD30, Th2 cytokines and HIV infection: a complex and fascinating link

CD30 is a member of the tumor necrosis factor (TNF)/nerve growth factor (NGF) receptor superfamily, and was originally described as a marker of Hodgkin's and Reed-Sternberg cells in Hodgkin's lymphoma. CD30 is preferentially expressed on CD4+ and CD8+ T-cell clones that produce T helper 2 (Th2)-type cytokines, and is also released in a soluble form by these cells. Elevated serum levels of soluble (s)CD30 have been found in some conditions in which a pathogenic role for Th2 cells has been suggested, such as atopy, Omenn's syndrome, systemic lupus erythematosus, as well as following infection with measles virus or human immuno-deficiency virus (HIV). Here, Gianfranco Del Prete and colleagues suggest a complex and fascinating link between the expression and release of CD30, and the immunopathogenesis of HIV infection.

From AIDS to parasite infection: pathogen-mediated subversion of programmed cell death as a mechanism for immune dysregulation

Premature cell death can result either from cell injury or degeneration, leading to necrosis, or from the activation of a physiological cell-suicide process, termed programmed cell death or apoptosis, that is regulated by intercellular signalling. This process plays an essential role in the selection of developing lymphocytes, and is also involved in the function of the mature adaptative immune system. A growing number of experimental findings during the last 4 years has provided support to our hypothesis that inappropriate HIV-mediated dysregulation of programmed T-cell death is relevant to AIDS pathogenesis. A series of recent experimental results also supports the general concept that the persistence and pathogenesis of several infectious pathogens, ranging from retroviruses to parasites, may be related to their capacity to dysregulate programmed cell death in various cell populations including lymphocytes. Subversion by pathogens of the physiological control of programmed cell death provides a paradigm for the pathogenesis of a wide range of infectious diseases that involve immune dysregulation and suggests therapeutic potential for the in vivo modulation of cell signalling.