Long-term follow-up of HIV positive asymptomatic patients having received cyclosporin A

HIV-Related Immune Activation and Inflammation: Current Understanding and Strategies

Although antiretroviral therapy effectively controls human immunodeficiency virus (HIV) replication, a residual chronic immune activation/inflammation persists throughout the disease. This aberrant immune activation and inflammation are considered an accelerator of non-AIDS-related events and one of the driving forces of CD4⁺ T cell depletion. Unfortunately, HIV-associated immune activation is driven by various factors, while the mechanism of excessive inflammation has not been formally clarified. To date, several clinical interventions or treatment candidates undergoing clinical trials have been proposed to combat this systemic immune activation/inflammation. However, these strategies revealed limited results, or their nonspecific anti-inflammatory properties are similar to previous interventions. Here, we reviewed recent learnings of immune activation and persisting inflammation associated with HIV infection, as well as the current directions to overcome it. Of note, a more profound understanding of the specific mechanisms for aberrant inflammation is still imperative for identifying an effective clinical intervention strategy.

Oral disease-modifying antirheumatic drugs and immunosuppressants with antiviral potential, including SARS-CoV-2 infection: a review

There have been several episodes of viral infection evolving into epidemics in recent decades, and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the latest example. Its high infectivity and moderate mortality have resulted in an urgent need to find an effective treatment modality. Although the category of immunosuppressive drugs usually poses a risk of infection due to interference of the immune system, some of them have been found to exert antiviral properties and are already used in daily practice. Recently, hydroxychloroquine and baricitinib have been proposed as potential drugs for SARS-CoV-2. In fact, there are other immunosuppressants known with antiviral activities, including cyclosporine A, hydroxyurea, minocycline, mycophenolic acid, mycophenolate mofetil, leflunomide, tofacitinib, and thalidomide. The inherent antiviral activity could be a treatment choice for patients with coexisting rheumatological disorders and infections. Clinical evidence, their possible mode of actions and spectrum of antiviral activities are included in this review article.

LAY SUMMARY

Immunosuppressants often raise the concern of infection risks, especially for patients with underlying immune disorders. However, some disease-modifying antirheumatic drugs (DMARDs) with inherent antiviral activity would be a reasonable choice in the situation of concomitant viral infections and flare up of autoimmune diseases. This review covers DMARDs of treatment potential for SARS-CoV-2 in part I, and antiviral mechanisms plus trial evidence for viruses other than SARS-CoV-2 in part II.

A 30-year journey of trial and error towards a tolerogenic AIDS vaccine

Since 1985, we have tested several immunological approaches to suppressing HIV replication in HIV-infected patients and to prevent HIV acquisition in uninfected people. Here, after briefly reviewing our studies on immunosuppressive treatments and therapeutic dendritic cell-based therapies, we examine in more detail our work on the tolerogenic vaccines we developed against AIDS in Chinese macaques. The vaccine consisted of inactivated SIVmac239 particles adjuvanted with the Bacillus of Calmette and Guerin (BCG), Lactobacillus plantarum (LP), or Lactobacillus rhamnosus (LR). Without adjuvant, the vaccine administered by the intragastric route induced the usual simian immunodeficiency virus (SIV)-specific humoral immune responses but no post-challenge protection. In contrast, out of 24 macaques that were immunized with the adjuvanted vaccine and challenged intrarectally with SIVmac239 or SIVB670, 23 were sterilely protected for up to 5 years, while all control macaques were infected. On the other hand, all macaques of Indian origin that were immunized with the same adjuvanted vaccine were not protected. We then discovered that vaccinated Chinese macaques developed a previously unrecognized class of non-cytolytic MHC-Ib/E-restricted CD8⁺ T cells (or CD8⁺ T-Regs) that suppressed the activation of SIV RNA-infected CD4⁺ T cells and thereby inhibited the (activation-dependent) reverse transcription of the virus and prevented the establishment of SIV infection. Finally, we found a similar population of HLA-E-restricted CD8⁺ T-Regs in human elite controllers (a small group of HIV-infected patients whose viral replication is naturally inhibited). Ex vivo, their CD8⁺ T-Regs suppressed viral replication in the same manner as those of vaccinated Chinese macaques. It is noteworthy that all of these elite controllers had a homo- or heterozygous HLA-Bw4-80I genotype. Taking into account the longevity and the high percentage of vaccine-protected Chinese macaques together with the concomitant identification of a robust ex vivo correlate of protection and the discovery of similar CD8⁺ T-Regs in human elite controllers, preventive and therapeutic HIV vaccines should be envisaged in humans.

Rheumatoid arthritis in patients with HIV: management challenges

Over the past few decades, HIV has been transformed from a once-uniformly fatal disease to now a manageable but complex multisystem illness. Before highly active antiretroviral therapy (HAART), reports suggested that HIV-infected patients with rheumatoid arthritis (RA) would experience remission of their disease. It has now become clear that RA can develop in HIV-infected patients at any time, independent of HAART. Choosing the right medication to treat symptoms related to RA while avoiding excess weakening of the immune system remains a clinical challenge. Agents such as hydroxychloroquine and sulfasalazine might best balance safety with efficacy, making them reasonable first choices for therapy in HIV-infected patients with RA. More immune suppressing agents such as methotrexate may balance safety with efficacy, but data are limited. Corticosteroids such as prednisone may also be reasonable but could increase the risk of osteonecrosis. Among biologic response modifiers, tumor necrosis factor α inhibitors may balance safety with efficacy, but perhaps when HIV replication is controlled with HAART. Monitoring RA disease activity remains challenging as only one retrospective study has been published in this area. Those with HIV infection and RA can experience comorbidities such as accelerated heart disease and osteoporosis, a consequence of the chronic inflammatory state that each illness generates. Although HIV-infected patients are at risk for developing the immune reconstitution inflammatory syndrome when starting HAART, it appears that immune reconstitution inflammatory syndrome has a minimal effect on triggering the onset or the worsening of RA.

Mucosal SIV Vaccines Comprising Inactivated Virus Particles and Bacterial Adjuvants Induce CD8(+) T-Regulatory Cells that Suppress SIV-Positive CD4(+) T-Cell Activation and Prevent SIV Infection in the Macaque Model

A new paradigm of mucosal vaccination against human immunodeficiency virus (HIV) infection has been investigated in the macaque model. A vaccine consisting of inactivated simian immunodeficiency virus (SIV)mac239 particles together with a living bacterial adjuvant (either the Calmette and Guerin bacillus, Lactobacillus plantarum or Lactobacillus rhamnosus) was administered to macaques via the vaginal or oral/intragastric route. In contrast to all established human and veterinary vaccines, these three vaccine regimens did not elicit SIV-specific antibodies nor cytotoxic T-lymphocytes but induced a previously unrecognized population of non-cytolytic MHCIb/E-restricted CD8(+) T-regulatory cells that suppressed the activation of SIV-positive CD4(+) T-lymphocytes. SIV reverse transcription was thereby blocked in inactivated CD4(+) T-cells; the initial burst of virus replication was prevented and the vaccinated macaques were protected from a challenge infection. For 3-14 months after intragastric immunization, 24 macaques were challenged intrarectally with a high dose of SIVmac239 or with the heterologous strain SIV B670 (both strains grown on macaques PBMC). Twenty-three of these animals were found to be protected for up to 48 months while all 24 control macaques became infected. This protective effect against SIV challenge together with the concomitant identification of a robust ex vivo correlate of protection suggests a new approach for developing an HIV vaccine in humans. The induction of this new class of CD8(+) T-regulatory cells could also possibly be used therapeutically for suppressing HIV replication in infected patients and this novel tolerogenic vaccine paradigm may have potential applications for treating a wide range of immune disorders and is likely to may have profound implications across immunology generally.

HIV-associated chronic immune activation

Systemic chronic immune activation is considered today as the driving force of CD4(+) T-cell depletion and acquired immunodeficiency syndrome (AIDS). A residual chronic immune activation persists even in HIV-infected patients in which viral replication is successfully inhibited by anti-retroviral therapy, with the extent of this residual immune activation being associated with CD4(+) T-cell loss. Unfortunately, the causal link between chronic immune activation and CD4(+) T-cell loss has not been formally established. This article provides first a brief historical overview on how the perception of the causative role of immune activation has changed over the years and lists the different kinds of immune activation characteristic of human immunodeficiency virus (HIV) infection. The mechanisms proposed to explain the chronic immune activation are multiple and are enumerated here, as well as the mechanisms proposed on how chronic immune activation could lead to AIDS. In addition, we summarize the lessons learned from natural hosts that know how to 'show AIDS the door', and discuss how these studies informed the design of novel immune modulatory interventions that are currently being tested. Finally, we review the current approaches aimed at targeting chronic immune activation and evoke future perspectives.

Probable deceleration of progression of Simian AIDS affected by opiate dependency: studies with a rhesus macaque/SIVsmm9 model

OBJECTIVES

To determine effects of opiate dependency on development of simian AIDS.

DESIGN

Assessments of viral, immune, and clinicopathological status were conducted on rhesus macaques before and after establishment of opiate dependency and Simian Immunodeficiency Virus, sooty mangabey, strain-9 (SIVsmm9) infection. Controls received saline.

METHODS

Blood was collected at baseline, before opiate dependencies, and viral infections were established and then after SIVsmm9 infection, longitudinally, through 216 weeks. Plasma viral titers were assessed using the branched chain DNA assay and CD4 and CD8 counts via cytofluorometry. Clinicopathological assessments of AIDS were founded on Centers for Disease Control and Prevention and other selected criteria.

RESULTS

AIDS progression rates seemed to be decelerated and survival times increased by opiate dependency. Mean viral titers were unaffected by opiate exposure. Opiate-dependent monkeys that evidenced high initial viral titers survived significantly longer than controls. Several opiate-dependent monkeys maintained high viral titers for atypically extended durations. Several (5/19) opiate-dependent monkeys died or were removed early from the study due to "non-AIDS" causes.

CONCLUSIONS

Long-term opiate dependency seemed to decelerate the rate of progression to AIDS in the SIVsmm9 monkey model. This effect was most evident in monkeys with high initial viral titers/set points. "Non-AIDS" morbidities and mortalities were noted as potential confounds of epidemiological assessments of the role of opiates in HIV/AIDS.

Treatment of rheumatic diseases in patients with HCV and HIV infection

A wide variety of rheumatic diseases has been documented in the presence of hepatitis C virus (HCV) infection and in human immunodeficiency virus (HIV) infection. In this conditions, physicians are refrained from using corticosteroids and/or immunosuppressants agents because of the risk of favouring viral replication and the progression of the underlying viral disease. In the present review we have focused our attention on the possible role of cyclosporine A (CsA), anti-Tumour Necrosis Factor (TNF) alpha agents in the treatment of HIV or HCV infected autoimmune patients. The results drown from the literature and from our personal experience confirm the safety of CsA and anti-TNF alpha agents, in terms of viral load and liver toxicity. A limited experience also suggest that both therapies can be given in combination in rheumatoid arthritis patients without increasing the risk of adverse events.

Role of cyclophilin A in HIV replication

More than a decade has passed since the discovery that the peptidyl prolyl isomerase cyclophilin A (CypA) specifically binds to a proline-rich sequence in HIV-1 capsid (CA) and is thereby incorporated into viral particles. Since then, a variety of possible functions of CypA in the HIV-1 replication cycle have been intensively investigated, but the biological function of this interaction remains to be determined. The binding of CypA to CA increases HIV-1 infectivity in human cells, but promotes an anti-HIV-1 restriction activity in cells from nonhuman primates. Numerous studies have been undertaken to understand the paradoxical effects of CypA and, along with the parallel discovery of the restriction factor tripartite motif 5α, our understanding of how CypA modulates HIV-1 infectivity has now been changed completely. However, 13 years after its discovery, the biological function of the specific interaction between HIV-1 CA and CypA is still not fully understood. Even though much insight has been provided to date, many questions remain unanswered.

Antiretroviral and immunosuppressive drug-drug interactions: an update

With the introduction of highly active antiretroviral therapy (HAART), human immunodeficiency virus (HIV) infection has become a chronic disease with more frequent end-stage organ failures. As a result, the question of transplantation in HIV patients is raised more often. However, some of the HAART regimen medications require elimination or metabolism via the P-glycoprotein (P-gp) and multidrug-resistant protein (MRP) transporters or via the cytochrome P450 enzyme system. Since these transporters and enzymes are also responsible for the clearance of immunosuppressive drugs, drug-drug interactions are likely to occur. Indeed, profound drug-drug interactions between protease inhibitors and immunosuppressive drugs have been observed and they required reductions in drug dosage. In contrast, HAART using nucleoside or nonnucleoside reverse transcriptase inhibitors without the use of protease inhibitors has been shown to produce less significant drug-drug interactions. It is thus crucial to take into account those potential pharmacokinetic and/or pharmacodynamic drug-drug interactions in order to avoid drug toxicity or a lack of efficacy. The aim of this work was to review and synthesize the international literature on this field in order to give practical recommendations on how to manage immunosuppressive drugs in HIV patients who get transplanted and on how to handle HAART therapy in transplant-recipient patients who get infected with HIV.

Liver transplantation in patients with HIV infection

1. Liver transplantation for human immunodeficiency virus (HIV)-positive patients with end-stage liver disease in the era of highly active retroviral therapy has proven to be an effective treatment. The concerns of HIV progression have not been borne out by the growing worldwide experience. 2. CD4 counts are stable and HIV viral load is controllable with medication following liver transplantation. 3. Hepatitis C virus (HCV) coinfection in HIV-positive recipients is universal, but the severity of recurrence does not appear to be different from that in HIV-negative patients with HCV liver disease. 4. Complex pharmacokinetic interactions between the calcineurin inhibitors used for immunosuppression along with protease inhibitors are present, but management directed at recognizing the need for monitoring levels does not appear to increase the risk of toxicity. 5. The degree of immunosuppression from iatrogenic drug therapy and HIV does not lead to increased risk of infectious complications.

Long-term clinical, immunologic and virologic impact of glucocorticoids on the chronic phase of HIV infection

BACKGROUND

To test the hypothesis of down-regulating the increased immune system activation/destruction process associated with chronic HIV infection, we focused our interest on prednisolone (PDN), because we had showed that, in vitro, PDN had a strong anti-apoptotic activity on activated T cells of HIV-infected patients and no effect on viral replication. We thus designed in 1992 a pilot study to evaluate the clinical, immunologic and virologic effects of PDN. The drug was given to a group of 44 patients with CD4 T cells over 200/microl. After one year, no patient had developed clinical AIDS and the mean CD4 T cell count of the group had increased from 441 +/- 21 cells/microl to 553 +/- 43 cells/microl. Moreover, markers of immune activation had dropped back to normal levels while the mean viral load of the group had remained unchanged. Here we explore the long-term clinical, immunologic, and virologic impact of prednisolone on the chronic phase of HIV infection.

METHODS

Retrospective study over 10 years starting between July 1992 and February 1993. A total of 44 patients with CD4 cells/microl ranging from 207 to 775 were treated with prednisolone, 0.5 mg/kg/d, over 6 months and 0.3 mg/kg/d thereafter.

RESULTS

No clinical AIDS developed under prednisolone; side effects of the drug were mild. CD4 cells which increased from 421 cells/microl at entry to 625 cells/microl at day 15, slowly decreased to reach 426 cells/microl after two years; T cell apoptosis and activation markers dropped within 15 days to normal levels and reincreased slowly thereafter. Serum viral loads remained stable. The percentage of patients maintaining CD4 cells over entry was 43.2% at two years, 11.4% at five years and 4.6% at 10 years. Initial viral load was highly predictive of the rate of CD4 decrease under prednisolone.

CONCLUSIONS

Prednisolone postponed CD4 cell decrease in a viral load dependent manner for a median of two years and for up to 10 years in a fraction of the patients with a low viral load. These findings might stimulate clinical trials as well as biological research on the role of antiapoptotic drugs in HIV infection.

Orthotopic liver transplantation in patients with human immunodeficiency virus and end-stage liver disease

Patients with human immunodeficiency virus (HIV) most often have hepatitis C virus (HCV) or hepatitis B (HBV) virus coinfection, or both, as a cause of their liver disease. Recent survival statistics show that patients infected with HIV treated with highly active antiretroviral therapy (HAART) can expect a significant prolongation of life by interfering with the natural progression of HIV to acquired immune deficiency syndrome (AIDS). Therefore, HIV-positive patients experiencing complications of liver failure are at greater immediate risk of dying from their end-stage liver disease (ESLD) rather than their HIV. Many transplant centers still consider HIV infection as a contraindication for orthotopic liver transplantation (OLT). At our two institutions, we believe that patients with HIV suffering from ESLD should be considered for OLT. This study evaluates the survival of patients undergoing OLT with HIV under HAART therapy. OLT was performed in 16 patients with HIV suffering from ESLD as a result of chronic HCV, chronic HBV, or fulminant hepatic failure (FHF). Collected data include patient demographics, patient and graft survival, pre-OLT assessments, and postoperative complications (including opportunistic infections). Ten patients at Pittsburgh and 6 patients at Miami received OLT. Of the 16 patients who received OLT, 14 remain alive to date. Thirteen of 16 patients are more than 12 months post-OLT, whereas the last patient is currently 6 months post-OLT. Five patients at Miami and 9 of 10 patients at Pittsburgh received HAART therapy before OLT, although 2 of the Pittsburgh patients had their HAART therapy discontinued before OLT because of significant liver dysfunction. The pre-OLT viral loads were undetectable in 13 of 16 patients. The cluster determinant (CD)4 count was less than 200 in 6 patients and greater than 100 in 2 patients before OLT. In all patients, CD4 counts increased above 200 in the post-OLT period. Tacrolimus toxicity associated with the pharmacologic inhibition of cytochrome p450 metabolism caused by protease inhibitors occurred in 6 patients after OLT. Six patients (38%) experienced acute cellular rejection immediately after OLT. Our experience suggests that OLT is effective in selected HIV-positive patients suffering from ESLD. Patient and graft survival was similar to non-HIV-positive patients suffering from the same indications for OLT. Acute cellular rejection was no less frequent that seen in non-HIV-positive patients. Given the complex pharmacologic interactions between the protease inhibitors and tacrolimus, careful monitoring, and attention is required to prevent toxicity or underdosing.

HIV-1, NFAT, and cyclosporin: immunosuppression for the immunosuppressed?

The human immunodeficiency virus-1 (HIV-1), the cause of AIDS, remains a significant cause of morbidity and mortality throughout the planet. Although reverse transcriptase and protease inhibitors have substantially slowed the virus, viral resistance complicates therapy. Because HIV-1 relies on its host's transcriptional machinery for its own replication, strategies for targeting activation-dependent transcription factors in CD4 T cells are being considered for adjunctive therapy in HIV-1-infected individuals. The nuclear factor of activated T cells (NFAT) family of transcription factors is one such target. On T-cell stimulation, NFAT proteins translocate to the nucleus, where they activate a large number of early response genes, including cytokines such as interleukin-2. Activation and nuclear translocation of NFAT proteins are abrogated by the powerful immunosuppressants cyclosporin A (CsA) and FK506. Over the last several years, various investigators have demonstrated that NFAT proteins bind to the HIV-1 LTR promoter and increase viral transcription. In this report, further evidence supporting a role for NFAT proteins in augmenting HIV-1 transcription is presented. In addition, other mechanisms of HIV-1 inhibition by CsA are reviewed, and the rationale for the use of CsA to treat AIDS is discussed.

Contribution of immune activation to the pathogenesis and transmission of human immunodeficiency virus type 1 infection

The life cycle of human immunodeficiency virus type 1 (HIV-1) is intricately related to the activation state of the host cells supporting viral replication. Although cellular activation is essential to mount an effective host immune response to invading pathogens, paradoxically the marked systemic immune activation that accompanies HIV-1 infection in vivo may play an important role in sustaining phenomenal rates of HIV-1 replication in infected persons. Moreover, by inducing CD4+ cell loss by apoptosis, immune activation may further be central to the increased rate of CD4+ cell turnover and eventual development of CD4+ lymphocytopenia. In addition to HIV-1-induced immune activation, exogenous immune stimuli such as opportunistic infections may further impact the rate of HIV-1 replication systemically or at localized anatomical sites. Such stimuli may also lead to genotypic and phenotypic changes in the virus pool. Together, these various immunological effects on the biology of HIV-1 may potentially enhance disease progression in HIV-infected persons and may ultimately outweigh the beneficial aspects of antiviral immune responses. This may be particularly important for those living in developing countries, where there is little or no access to antiretroviral drugs and where frequent exposure to pathogenic organisms sustains a chronically heightened state of immune activation. Moreover, immune activation associated with sexually transmitted diseases, chorioamnionitis, and mastitis may have important local effects on HIV-1 replication that may increase the risk of sexual or mother-to-child transmission of HIV-1. The aim of this paper is to provide a broad review of the interrelationship between immune activation and the immunopathogenesis, transmission, progression, and treatment of HIV-1 infection in vivo.

Immunopathogenesis of human immunodeficiency virus: implications for immune-based therapies

Human immunodeficiency virus (HIV) infection leads to a state of CD4 lymphopenia and generalized immune activation with subsequent development of opportunistic infections and neoplasms. The use of highly active antiretroviral treatment has dramatically improved the clinical outcome for HIV-infected patients, but the associated cost and toxicity and the eventual development of drug resistance have underscored the need for additional therapeutic strategies. Immune-based therapies, such as treatment with cytokines or immunosuppressants, adoptive immunotherapy, and therapeutic immunizations, are being intensely investigated as potential supplements to antiretroviral therapy. Although much data have been generated as a result of these efforts, to date there has been little evidence of the clinical efficacy of these strategies. Randomized clinical studies remain critical in evaluating the clinical significance and the role of immune-based therapies in the therapeutic armamentarium against HIV.

Selective transmission of R5-tropic HIV type 1 from dendritic cells to resting CD4+ T cells

In an in vitro coculture model of monocyte-derived, cultured human dendritic cells (DC) with autologous CD4(+) resting T cells, CCR5 (R5)-tropic strains of HIV-1, but not CXCR4 (X4)-tropic strains, were transmitted to resting CD4+ T cells, leading to prolific viral output, although DC were susceptible to infection with either strain. Macrophages, which were also infectable with either R5- or X4-tropic strains, did not transmit infection to CD4+ cells. Highly productive HIV infection in this model appeared to be a consequence of heterokaryotic syncytium formation between infected DC and T cells since syncytia formation developed only in R5-infected DC/CD4+ cocultures. These results suggested that the unique microenvironment derived from the fusion between the infected DC and CD4+ cell was highly permissive and selective for replication of R5-tropic viruses. The apparent selectivity for R5-tropic strains in such syncytia was attributable neither to differential DC-mediated activation nor to selective modulation of induction of alpha- or beta-chemokines in the infected DC. This model of HIV replication may provide useful insights into in vitro correlates of HIV pathogenicity.

Heat shock proteins: novel therapeutic tools for HIV-infection?

Heat shock proteins (Hsps), cyclophilins (Cyps) and FK binding proteins (FKBPs) form a family of intracellular chaperone molecules that facilitate protein folding and assembly. These stress proteins are selectively expressed in cells in response to a range of stimuli, including heat, lymphokine and microbial/viral infections. This review discusses the role of stress proteins in the HIV-1 viral life cycle, with regard to the development of specific Hsp-based therapeutic strategies against HIV-1 infection. Cumulative findings are cited implicating CypA, Hsp27, Hsp70 and FKBPs in host cell and viral activation, viral entry, assembly or formation of infectious virions. Biological response modifiers that show specific high-affinity interactions with Cyp, FKBPs and Hsps, including cyclosporins, FK-506 and cyclopentenone prostaglandins respectively, may block HIV-1 replication and infection, providing novel HIV-1 therapeutic strategies. Moreover, Hsp binding to viral complexes can enhance antiviral immunity, including natural killer (NK), antibody-dependent (ADCC), gamma delta T-cell and cytotoxic T-lymphocyte (CTL) activities against HIV-1 infected cells. The ability of Hsps to interact with HIV-1 viral proteins, combined with their inherent adjuvant and immunogenic properties indicates that Hsps may also serve as vehicles for antigen delivery and the design of AIDS vaccines.

Immune-Based Therapies for the Management of HIV Infection: Highly Active Antiretroviral Therapy and Beyond

The widespread use of highly active antiretroviral therapy (HAART) has had a significant impact on reducing the incidence of opportunistic infections in patients with the Acquired Immunodeficiency Syndrome (AIDS) and reducing the overall morbidity and mortality associated with this disease. However, the use of HAART is often associated with adverse effects, significant drug interactions, high cost and the emergence of viral resistance in a significant percentage of treatment recipients. In addition, the clinical efficacy of HAART in terms of viral eradication appears to be limited due to the presence of reservoirs of latent virus within HAART-experienced patients. Because of these and other limitations associated with antiretroviral therapies, new therapeutic strategies are being developed to restore the normal function of the immune system and improve patient outcomes. The purpose of this article is to review some of the more promising investigational immune-based therapies and their potential role in the management of Human Immunodeficiency Virus infection.

HIV gp120 plus specific peptides are recognized in a similar manner to specific HLA plus peptide by HLA-restricted antigen-specific T-cell lines

HIV induces disease only following chronic activation of the immune system. Other retroviruses such as the mouse mammary tumour virus (MMTV) activate a large percentage of T cells by encoding a superantigen (SAg). To date there is no evidence that HIV encodes a SAg. An alternative way to induce pan-activation of the immune system is by allogeneic stimulation, which occurs following transplantation. Here we extend previous work which demonstrated that HIVpg120 could bind peptides in a similar manner to HLA, by demonstrating that human antigen presenting cells (APCs) expressing gp120 (but not DR1) can present a DR1-restricted peptide to induce proliferation of a DR1-restricted peptide-specific T-cell line in a similar manner to the same peptide presented by a DR1 expressing APC. Our data provide strong support for the hypothesis that the HLA-like regions of gp120 encode functional properties shared with HLA, and could explain the extraordinary clinical and immunological similarities between AIDS and chronic graft versus host disease.

NFAT1 enhances HIV-1 gene expression in primary human CD4 T cells

Cyclosporin A (CsA) is a potent inhibitor of the NFAT family of transcription factors that enhance T cell activation. The observation that human immunodeficiency virus type 1 (HIV-1)-positive transplant recipients have a reduced HIV-1 viral burden during treatment with CsA suggested that NFAT may play a direct role in enhancing transcription of the HIV-1 viral genome. Two sets of NFAT binding sites were identified in the HIV-1 long terminal repeat (LTR) promoter by in vitro footprinting with full-length recombinant NFAT protein, and gel shift analysis of nuclear protein from polyclonally activated primary CD4 T cells revealed specific binding of NFAT1 to the NFkappaB binding sites of the HIV-1 LTR. Activation of primary CD4 T cells transiently transfected with a HIV-1 LTR luciferase reporter plasmid, lacking the NFAT binding sites in the upstream putative negative regulatory element but maintaining the NFkappaB/NFAT sites, demonstrated increased HIV-1 gene expression when cotransfected with a NFAT1 expression vector. Moreover, CsA, FK506, and a dominant-negative NFAT1 protein independently inhibited HIV-1 LTR promoter activity in CD4 T cells stimulated with phorbol ester and calcium ionophore. In primary human CD4 T cells, CsA also inhibited promoter activity directed by multimers of binding sites for NFAT, while having no effect on NFkappaB multimer-driven promoter activity. Increasing NFAT1 levels in CD4 T cells transiently transfected with a HIV-1 provirus also increased p24 protein expression. Thus, NFAT may be a target for prevention of HIV-1 LTR-directed gene expression in human CD4 T cells.

New uses for old drugs in HIV infection: the role of hydroxyurea, cyclosporin and thalidomide

The tenacious effort to develop new, specific agents to treat HIV infection is currently accompanied by a reconsideration of existing drugs on the basis of their known or putative effects on the retroviral life cycle and/or the tuning of immune mechanisms. Three specific 'older' compounds that interfere with HIV infection by both a direct antiviral activity, and a modulation of T-cell activation and proliferation have received the most attention. Hydroxurea, a classical chemotherapeutic agent, inhibits retroviral reverse transcription by targeting a cellular enzyme responsible for the synthesis of deoxynucleoside triphosphates. It may also have a role in reducing viral load while maintaining low numbers of potential target T cells. Beneficial effects of hydroxyurea in combination with didanosine and/or stavudine on viral load have been shown in a number of clinical trials. Cyclosporin, a known immunosuppressant, blocks the activation of T cells, hence reducing the permissivity to HIV, and also prevents proper HIV virion maturation. However, clinical studies have produced conflicting results in HIV-infected patients with regard to immunological and disease effects and toxicity. Thalidomide may have antiretroviral effects as a result of its primarily inhibitory effects on the production of tumour necrosis factor alpha (TNFalpha). TNFalpha induces expression of HIV from chronically infected cell lines by stimulating a cellular transcription factor, and blocking of TNFalpha-stimulated HIV replication by thalidomide has been shown in vitro and ex vivo. However, the effects on TNFalpha production in vivo have been inconsistent. Thalidomide has shown potential in treating some AIDS-related conditions [cachexia (weight loss and muscle wasting), and aphtous oral, oesophageal or genital ulcers]. However, because of its numerous and major adverse effects, thalidomide should always be used cautiously. In summary, some older drugs have potential as anti-HIV agents and offer the advantage of extensive clinical experience in other therapeutic areas. They should be considered as potential partners for the products emerging from more recent research and development.