Immune restoration and CD4+ T-cell function with antiretroviral therapies

Immune reconstitution disease associated with mycobacterial infections in HIV-infected individuals receiving antiretrovirals

Immune reconstitution disease (IRD) in HIV-infected patients is an adverse consequence of the restoration of pathogen-specific immune responses during the initial months of highly active antiretroviral treatment (HAART). Previously subclinical infections are "unmasked" or pre-existing opportunistic infections clinically deteriorate as host immunopathological inflammatory responses are "switched on". IRD is most frequently associated with mycobacterial infections. Our literature search identified 166 published cases of IRD associated with mycobacterial infections. We review the underlying immunological mechanisms, difficulties surrounding case definition and diagnosis, the wide diversity of clinical manifestations, and treatment. The importance of screening patients for mycobacterial disease before starting HAART and the critical impact of the timing of commencement of HAART in patients receiving treatment for tuberculosis are highlighted. We also discuss the problem of IRD associated with mycobacterial diseases in developing countries where tuberculosis prevalence is high and access to HAART is currently expanding.

Tumid lupus erythematosus occurring following highly active antiretroviral therapy for HIV infection: A manifestation of immune restoration

Tumid lupus erythematosus (LE) is a relatively rare and only recently recognized subset of chronic cutaneous lupus. We report a case occurring in a male with HIV infection whereby his rash was only unmasked by immune restoration following highly active antiretroviral therapy (HAART). The phenomenon of latent inflammatory or autoimmune disease appearing following HAART is now recognized as the "immune restoration syndrome" and tumid LE has not been reported in this setting previously. Fortunately this variant of lupus does not result in scarring and is responsive to anti-malarials, allowing continuation of HAART in this patient.

De novo generation of CD4 T cells against viruses present in the host during immune reconstitution

T cells recognizing self-peptides are typically deleted in the thymus by negative selection. It is not known whether T cells against persistent viruses (eg, herpesviruses) are generated by the thymus (de novo) after the onset of the infection. Peptides from such viruses might be considered by the thymus as self-peptides, and T cells specific for these peptides might be deleted (negatively selected). Here we demonstrate in baboons infected with baboon cytomegalovirus and baboon lymphocryptovirus (Epstein-Barr virus-like virus) that after autologous transplantation of yellow fluorescent protein (YFP)-marked hematopoietic cells, YFP+ CD4 T cells against these viruses were generated de novo. Thus the thymus generates CD4 T cells against not only pathogens absent from the host but also pathogens present in the host. This finding provides a strong rationale to improve thymopoiesis in recipients of hematopoietic cell transplants and, perhaps, in other persons lacking de novo-generated CD4 T cells, such as AIDS patients and elderly persons.

Epigenetic reprogramming of UDP-N-acetylglucosamine 2-epimerase/N-acetylmannosamine kinase (GNE) in HIV-1-infected CEM T cells

Sialylated glycoconjugates mediate several key lymphocyte functions. We previously reported that hyposialylation occurred in latently HIV-1-infected CEM T cells, despite the fully preserved catalytic activity of several sialyltransferases. We show now that these cells are affected by a down-regulation of UDP-N-acetylglucosamine 2-epimerase/N-acetylmannosamine kinase (GNE), which leads to a dramatic decrease in the synthesis of CMP-sialic acid, the donor substrate of all sialyltransferases. The GNE gene promoter was found to be located in a CpG island with several regulatory motifs CREB, SP1, and AP-2. De novo hypermethylation of this promoter was observed in HIV-1-infected CEM cells. This phenomenon might explain some immunological disorders that persist in infected individuals despite long-term therapeutically controlled viral replication. Indeed, an overall decrease in sialic acid engraftment can affect glycoproteins, notably those in which the sialylation status is crucial to ensure homing, recirculation, and survival of lymphocytes.

Paclitaxel for anthracycline-resistant AIDS-related Kaposi's sarcoma: clinical and angiogenic correlations

BACKGROUND

Murine data indicate that angiogenesis is central to the aetiopathogenesis of Kaposi's sarcoma (KS). Therefore, we measured angiogenic cytokines and growth factors in patients with AIDS-related KS during treatment with both antiretrovirals and second-line paclitaxel chemotherapy. Cytokines measured included tumour necrosis factor-alpha (TNF-alpha), basic fibroblast growth factor (bFGF), vascular endothelial growth factor (VEGF) and the interleukins IL-2, -6 and -12.

PATIENTS AND METHODS

Enzyme-linked immunosorbent assays (ELISAs) were carried out to measure plasma cytokine levels in 17 patients with AIDS-related KS who had progressed within 6 months of receiving liposomal anthracyclines and were treated with paclitaxel 100 mg/m(2) every 2 weeks. Measurements were carried out before progression, at commencement and at the completion of paclitaxel.

RESULTS

The objective response rate to paclitaxel was 71% (95% confidence interval 60% to 81%). In 17 patients with AIDS-related KS, we observed eight partial responses and four complete responses. Patients with AIDS Clinical Trial Group stage T1 disease had higher plasma VEGF (P = 0.05) and lower plasma TNF-alpha levels (P = 0.05) than patients with earlier stage T0 KS. There were no correlations between plasma cytokines (bFGF, VEGF, TNF-alpha, and IL-2,-6 and -12) and the CD4 and CD8 cell counts or HIV-1 RNA viral load. Response to paclitaxel was associated with a fall in plasma IL-6 levels (P = 0.04) but no change in other cytokines. There were no significant changes in CD4, CD8, CD16/56, CD19 cell counts and HIV-1 viral loads during chemotherapy.

CONCLUSIONS

Angiogenic cytokines may correlate with KS disease extent but not with cellular immune function or HIV viraemia. Response to paclitaxel therapy correlates with a fall in plasma IL-6 levels and recent data indicate this may be a surrogate marker of KS-associated herpesvirus viral load. Overall, clinical response in KS correlates poorly with known angiogenic cytokines.

Immune Restoration in Patients with HIV Infection: HAART and Beyond

Since the introduction of highly active antiretroviral therapy (HAART), there has been a dramatic decrease in HIV-related morbidity and mortality. Suppressing HIV replication by HAART can result in a restoration of the CD4+ T-cell count and, consequently, a diminished risk of opportunistic infections. However, the degree of immune restoration that can be achieved with HAART varies from patient to patient. It is often incomplete and can be poorest in those patients who, because of their very low CD4+ counts, need it the most. Additional approaches are needed to increase immune restoration still further. Structured treatment interruptions, therapeutic immunization, and recombinant interleukin-2 are three such options that are currently being investigated.

Nadir CD4+ T-cell count and numbers of CD28+ CD4+ T-cells predict functional responses to immunizations in chronic HIV-1 infection

OBJECTIVE

To ascertain whether delaying the initiation of highly active antiretroviral therapy (HAART) compromises functional immune reconstitution in HIV-1 infection in persons who regain 'normal' CD4 T-cell counts after suppressive antiretroviral therapies.

DESIGN

Prospective open-label study carried out at two University-affiliated HIV-outpatient clinics in the USA.

SUBJECTS AND METHODS

Response to immunization was used as a model for in vivo functional immune competence in 29 HIV-1 infected patients with CD4 T-cell counts > 450 x 106 cells/l and HIV-RNA < 400 copies/ml for > 12 months after HAART and nine HIV-1 seronegative controls. After immunization with tetanus toxoid, diphtheria-toxoid, and keyhole limpet hemocyanin, immune response scores (IRS) were calculated using postimmunization antibody concentrations, lymphocyte proliferation, and delayed-type hypersensitivity responses to vaccine antigens.

RESULTS

Despite normal numbers of circulating CD4 T-cells, the CD4 T-cell nadir before HAART initiation predicted the immune response to immunization (rho = 0.5; P < 0.005) while current CD4 T-cell count did not. Likewise, CD4 T-lymphocyte expression of the co-stimulatory molecule CD28 was also an independent predictor of response to immunization (rho = 0.5; P < 0.005).

CONCLUSIONS

Even among persons who controlled HIV replication and normalized CD4 T-cell counts with HAART, pretreatment CD4 T-cell count and numbers of circulating CD4+CD28+ T-cells at immunization, but not current CD4 T-cell count, predict the ability to respond to vaccination. Delaying the initiation of HAART in chronic HIV-1 infection results in impaired functional immune restoration despite normalization of circulating CD4 T-cell numbers.

Antiretroviral treatment of human immunodeficiency virus infection: Swedish recommendations

The Swedish guidelines (SwG) for treatment of human immunodeficiency virus (HIV) infection have several important roles. A major task involves the promotion of a uniformly high standard of care in all HIV treatment clinics in Sweden and the identification of strengths, weaknesses and relevance of recent research findings. CD4+ T-cell counts < 200 cells/microl are clear indications for the initiation of treatment, whereas high viral loads serve as an indication for increased vigilance rather than a criterion for therapy. It is recommended that the first regimen consists of 2 nucleoside reverse transcriptase inhibitors in combination with 1 protease inhibitor or 1 non-nucleoside reverse transcriptase inhibitor. The definition of treatment failure is rigorous. Treatment change should be considered if the viral load has not fallen by at least 1.5 log in 4 weeks or is undetectable within 3-4 months. Resistance testing is endorsed at primary infection, in the event of treatment failure and in pregnant women. Interaction with experts in HIV resistance testing is emphasized. Therapeutic drug monitoring is advocated. Patients with treatment failure should be handled individually and the decision on therapeutic strategy should be based on treatment history, resistance testing and other clinical facts. The SwG do not give recommendations for some important issues such as prolonged drug holidays and preferences in initial treatment regimens. More scientific data are likely to be available soon and the SwG will be refined accordingly. The present guidelines are translated from Swedish; they are published on the Medical Products Agency (MPA) and Swedish Reference Group for Antiviral Therapy (RAV) websites (www.mpa.se and www.rav.nu.se), including 7 separate papers based on a thorough literature search. A complete reference list is available on request from the MPA.

Systemic mycoses in the immunocompromised host: an update in antifungal therapy

Despite significant advances in the management of immunosuppressed patients, invasive fungal infections remain an important life-threatening complication. In the last decade several new antifungal agents, including compounds in pre-existing classes (new generation of triazoles, polyenes in lipid formulations) and novel classes of antifungals with a unique mechanism of action (echinocandins), have been introduced in clinical practice. Ongoing and future studies will determine their exact role in the management of different mycoses. The acceleration of antifungal drug discovery offers promise for the management of these difficult to treat opportunistic infections.

The clinical spectrum of hepatitis C virus in HIV coinfection

The biochemical, virologic, and histologic spectrum of hepatitis C virus (HCV) in 66 consecutive patients with HIV-HCV coinfection and 119 HCV controls was compared: 86% of coinfected patients had CD4 counts >200 cells/mm3, 51% had a normal alanine aminotransferase (ALT) value, the mean HCV RNA titer was 5.7 log IU/mL, 92% of coinfected patients were of genotype 1, and the mean histologic activity index was 6.86 with advanced fibrosis in 32% of patients. The biochemical, virologic, and histologic findings of HCV in coinfected patients were similar to those observed in HCV controls. For both groups of patients, no clinical, biochemical, or virologic factors could reliably identify patients with advanced fibrosis or cirrhosis, underscoring the importance of liver biopsy in the evaluation of these patients. The spectrum of liver disease in coinfection includes a significant proportion of patients with normal ALT values, and excluding these patients from previous studies has led to an overestimation of HCV disease severity.

Immune reconstitution

Immune reconstitution in HIV-infected patients remains a potential mechanism to explain delayed disease progression and increased survival following suppressive therapy. Many discrepancies remain to be studied. Is an immune response to HIV protective? Why are anti-HIV CD4 responses lost so quickly in progressors and how can they be restored? What is the damage to the immune system that occurs early in disease and why can it not be overcome by simply controlling viral replication? Will management of immune reconstitution be used in future adjunct treatment strategies (vaccine or STI)? Because HAART is not the answer to long-term management of HIV throughout the world, the recovery of immune function and it's potential to control viral replication remains a key goal in the long-term management of HIV-infected persons.