Lung infections in the HIV-infected adult.

PURPOSE OF REVIEW: This review describes current epidemiology, diagnosis, treatment and prevention of adult HIV-related lung infections using evidence published within the past 2 years. RECENT FINDINGS: Recent evidence has helped better determine the importance of early initiation of antiretroviral therapy in co-infected individuals with advanced immune suppression. Although this has led to a greatly reduced incidence of opportunistic infections in people with HIV, Pneumocystis pneumonia remains common. Pneumonia due to bacterial pathogens, such as Streptococcus pneumoniae, also causes considerable disease burden, but emerging evidence of the clinical efficacy of pneumococcal vaccination, especially conjugated vaccines, offers considerable promise. As HIV-infected populations become older, more emphasis should be given to the potential benefit of influenza prevention, particularly with vaccination, and encouraging smoking cessation. Co-infection with tuberculosis is still a huge problem worldwide, but the recent development and use of simple clinical algorithms based on symptoms and point-of-care testing for recognizing active disease offers great potential. SUMMARY: The lung remains an important site of disease in HIV-infected individuals. Increasing emphasis should be placed upon prevention of infection and modification of risk factors.

The role of flow cytometry in the interferon-gamma-based diagnosis of active tuberculosis and its coinfection with HIV-1--A technically oriented review.

TB remains uncontrolled. In resource-rich countries, only approximately 60% of diagnoses are confirmed by culture. The number is lower in resource-poor environments. Huge scope therefore exists for alternative diagnostic strategies. Counting antigen-specific lymphocytes by virtue of cytokine production following 8-16 h stimulation with tuberculosis antigens is currently the strategy of choice. Several methods exist, including ELISA, ELISpots, and flow cytometry. Although it is clear that blood samples stimulated by ESAT-6 and CFP-10 antigens discriminate between TB infection and BCG vaccination, it is flow-cytometry that seems to be able to distinguish active TB disease from mere TB exposure. Of the various flow-protocols including four-color tests (CD45-CD3-CD4-IFNgamma), three-color tests (CD3-CD4-IFNgamma) and two-color tests (CD4-IFNgamma), even the simplest is performing well, provided that the results are expressed as percentage of IFN-gamma+ cells per CD4+ lymphocytes (%IFNgamma/CD4+). Studies using broncho-alveloar lavage (BAL) and Induced-Sputum (ISp) show that TB-specific CD4+IFN-gamma+ T cells accumulate in the lung in pulmonary and extra-pulmonary TB at frequencies >5-20-fold more frequent than in blood. This pulmonary homing is absent following BCG immunization. The use of PPD to stimulate CD4+IFN-gamma+ cells in the lung in active TB leads to >3-12-fold greater responses than seen with CFP-10 or ESAT-6, and any interference from BCG vaccination is absent. This method is unaffected by HIV coinfection, which has always been the problem for other immune-based diagnostics. Further, lung-based samples provide material for rapid tests of both the IFN-gamma assay and bacteriology, and importantly, these tests are amenable for future simplification with automated fluorescence-image cytometers.Another development of the multiparameter analytical power of flow-cytometry is to use markers for "lung-seeking" populations of CD4+ T cells in blood, obviating lung sampling. In active TB, but not in BCG vaccinees, TB-specific memory CD4+ T cells can be found in blood that are dominantly CD27-negative and probably lung seeking and can be diagnostically useful.

Rapid diagnosis of smear-negative tuberculosis using immunology and microbiology with induced sputum in HIV-infected and uninfected individuals.

RATIONALE AND OBJECTIVES: Blood-based studies have demonstrated the potential of immunological assays to detect tuberculosis. However lung fluid sampling may prove superior as it enables simultaneous microbiological detection of mycobacteria to be performed. Until now this has only been possible using the expensive and invasive technique of broncho-alveolar lavage. We sought to evaluate an immunoassay using non-invasive induced-sputum to diagnose active tuberculosis. METHODS AND RESULTS: Prospective cohort study of forty-two spontaneous sputum smear-negative or sputum non-producing adults under investigation for tuberculosis. CD4 lymphocytes specific to purified-protein-derivative of Mycobacterium tuberculosis actively synthesising interferon-gamma were measured by flow cytometry and final diagnosis compared to immunoassay using a cut-off of 0.5%. Sixteen subjects (38%) were HIV-infected (median CD4 count [range] = 332 cells/microl [103-748]). Thirty-eight (90%) were BCG-vaccinated. In 27 subjects diagnosed with active tuberculosis, the median [range] percentage of interferon-gamma synthetic CD4+ lymphocytes was 2.77% [0-23.93%] versus 0% [0-2.10%] in 15 negative for active infection (p<0.0001). Sensitivity and specificity of the immunoassay versus final diagnosis of active tuberculosis were 89% (24 of 27) and 80% (12 of 15) respectively. The 3 positive assays in the latter group occurred in subjects diagnosed with quiescent/latent tuberculosis. Assay performance was unaffected by HIV-status, BCG-vaccination or disease site. Combining this approach with traditional microbiological methods increased the diagnostic yield to 93% (25 of 27) alongside acid-fast bacilli smear and 96% (26 of 27) alongside tuberculosis culture. CONCLUSIONS: These data demonstrate for the first time that a rapid immunological assay to diagnose active tuberculosis can be performed successfully in combination with microbiological methods on a single induced-sputum sample.

Tuberculosis and HIV co-infection: a practical therapeutic approach.

HIV and tuberculosis (TB) are leading global causes of mortality and morbidity, and yet effective treatment exists for both conditions. Rifamycin-based antituberculosis therapy can cure HIV-related TB and, where available, the introduction of highly active antiretroviral therapy (HAART) has markedly reduced the incidence of AIDS and death. Optimal treatment regimens for HIV/TB co-infection are not yet clearly defined. Combinations are limited by alterations in the activity of the hepatic cytochrome P450 (CYP) enzyme system, which in particular may produce subtherapeutic plasma concentrations of antiretroviral drugs. For example, protease inhibitors often must be avoided if the potent CYP inducer rifampicin is co-administered. However, an alternative rifamycin, rifabutin, which has similar efficacy to rifampicin, can be used with appropriate dose reduction. Available clinical data suggest that, for the majority of individuals, rifampicin-based regimens can be successfully combined with the non-nucleoside reverse transcriptase inhibitors nevirapine and efavirenz. Most available HAART regimens in areas that have a high burden of TB contain one or the other of these drugs as a backbone. However, significant questions remain as to the optimal dose of either agent required to ensure therapeutic plasma concentrations, especially in relation to particular ethnic groups. The timing of HAART initiation after starting antituberculosis therapy continues to be controversial. Debate centres upon whether early initiation of HAART increases the risk of paradoxical reactions (immune reconstitution-related events) and other adverse events, or whether delay greatly elevates the risk of disease progression. Further prospective clinical data are needed to help inform practice in this area.

Detection of mycobacterial antigen responses in lung but not blood in HIV-tuberculosis co-infected subjects.

Forty-seven HIV-infected adults had broncho-alveolar lavage stimulated with purified protein derivate of Mycobacterium tuberculosis. Eighteen of 19 (95%) with tuberculosis co-infection had interferon-gamma synthetic CD4 lymphocyte responses > 1% versus three of 28 (11%) without (P < 0.0001). Lung response was unrelated to blood CD4 cell count. BAL HIV tuberculosis responses were similar in 25 HIV-uninfected tuberculosis patients. Responses in matched blood samples were often undetectable. Therefore, immunological tuberculosis assays seem less affected by HIV co-infection when lung-based.

Virological response to highly active antiretroviral therapy is unaffected by antituberculosis therapy.

We compared 156 human immunodeficiency virus (HIV)-infected patients who had tuberculosis with control populations of similar size. Of 111 patients with HIV infection and tuberculosis who received highly active antiretroviral therapy (HAART) and therapy for tuberculosis concurrently, 92 (83%) achieved or maintained virus loads of <50 copies/mL, and 99 (89%) achieved or maintained a >or=2 log10 reduction in virus load after 6 months. Virological response and changes in CD4 cell count were equivalent to those in 111 matched HIV-infected subjects without tuberculosis starting HAART. Tuberculosis recurrence rates were similar to those found in an HIV-uninfected population of 156 subjects (3% and 1%, respectively). Treatment for HIV and tuberculosis does not compromise outcomes for either disease.

Expression of a novel cytokine, IL-4delta2, in HIV and HIV-tuberculosis co-infection.

BACKGROUND: Correcting the Th2 shift in HIV/AIDS represents a potential intervention strategy. However data on interleukin (IL)-4 expression in HIV or AIDS are un-interpretable because of failure to distinguish between IL-4 and its splice variant and natural antagonist, IL-4delta2. OBJECTIVE: To determine Th1 [interferon (IFN)-gamma], IL-4delta2 and Th2 (IL-4) expression in whole blood and lung lavage from healthy volunteers and in HIV or HIV-tuberculosis (TB) co-infection. DESIGN: Cross-sectional with prospective cohort. METHODS: Expression of IL-4delta2, IL-4 and IFN-gamma were determined by quantitative real-time PCR, using unstimulated cells from whole blood and lung lavage, in 20 HIV-TB (pulmonary) co-infected patients, 20 matched HIV-positive controls and 20 HIV-negative healthy volunteers. Results were correlated with plasma viral load, CD4 cell counts, radiological scores and response to anti-TB treatment. RESULTS: Compared to HIV negative donors, stable HIV-positive donors did not have increased levels of mRNA encoding IL-4, IL-4delta2 or IFN-gamma in blood or lavage. By contrast, the HIV-TB co-infected donors had increased IL-4 and IFN-gamma in both compartments. However the antagonist, IL-4delta2 was increased only in lavage. Consequently the dominant form was IL-4delta2 in lavage, but IL-4 itself in blood. The lung IL-4/IFN-gamma ratio correlated with radiological disease extent. With anti-TB treatment, IL-4 levels did not change whilst IL-4delta2 levels increased significantly. CONCLUSIONS: IL-4 and its natural antagonist, IL-4delta2 and are not upregulated in the absence of opportunistic infection. However in HIV-TB co-infection both cytokines increase in lung, but only IL-4 in the periphery. Further studies are required to determine if IL-4 facilitates systemic HIV progression.

Does immune reconstitution syndrome promote active tuberculosis in patients receiving highly active antiretroviral therapy?

OBJECTIVES: To assess whether highly active anti-retroviral therapy (HAART) contributes to the presentation of active tuberculosis (TB). DESIGN: Retrospective single-centre cohort study. METHODS: A total of 111 HIV-infected individuals with active TB were identified at an urban teaching hospital between February 1997 and April 2004. Those receiving HAART at the time of TB diagnosis were assessed. RESULTS: Nineteen of 111 (17%) were receiving HAART when TB developed. Within this group there appeared to be two distinct populations. Thirteen of 19, 12 from ethnic or social groups with high background rates of TB, developed disease a median of 41 days (range, 7-109) after starting HAART ('early TB' group). In six of 19 ('late TB' group), TB occurred a median of 358 days after HAART initiation (range, 258-598). The 'early TB' group had lower CD4 cell counts when starting HAART in comparison with the 'late TB' group (median; 87 versus 218 x 10 cells/l; P = 0.04); however no difference was observed in the rate of change of CD4 cell count (P = 0.5) or HIV load. Paradoxical reaction rate in the 'early TB' group was significantly greater than in the 'late-TB' group (62 versus 0%, P = 0.02) and greater than in a similar control population who started HAART while taking anti-TB therapy (62 versus 30%, P = 0.05). CONCLUSIONS: These data suggest anti-HIV treatment may amplify the presentation of active TB. This has implications for antiretroviral programmes in countries with high TB rates and warrants prospective investigation of a larger cohort.

In vivo and in vitro studies of a novel cytokine, interleukin 4delta2, in pulmonary tuberculosis.

RATIONALE: Tuberculosis progresses despite potent Th1 responses. A putative explanation is the simultaneous presence of a subversive Th2 response. However, interpretation is confounded by interleukin 4delta2 (IL-4delta2), a splice variant and inhibitor of IL-4. OBJECTIVE: To study levels of mRNA encoding IL-4 and IL-4delta2, and their relationship to treatment and clinical parameters, in cells from lung lavage and blood from patients with pulmonary tuberculosis. METHODS: IL-4delta2, IFN-gamma, IL-4, and soluble CD30 (sCD30) levels were measured by polymerase chain reaction and relevant immunoassays in 29 patients and matched control subjects lacking responses to tuberculosis-specific antigens. RESULTS: mRNA levels for IL-4 and IL-4delta2 were elevated in unstimulated cells from blood and lung lavage of patients versus control subjects (p < 0.005). In control subjects, there were low basal levels of IL-4 and IL-4delta2 mRNA expressed mainly by non-T cells (p < 0.05). However, in patients, there were greater levels of mRNA for both cytokines in both T- and non-T-cell populations (p < 0.05 compared with control subjects). Radiologic disease correlated with the IL-4/IFN-gamma ratio and sCD30 (p < 0.005). After chemotherapy, IL-4 mRNA levels remained unchanged, whereas IL-4delta2 increased in parallel with IFN-gamma (p < 0.05). Sonicates of Mycobacterium tuberculosis upregulated expression of IL-4 relative to IL-4delta2 in mononuclear cell cultures from patients (p < 0.05). CONCLUSIONS: A Th2-like response, prominent in T cells and driven by tuberculosis antigen, is present in tuberculosis and modulated by treatment, suggesting a role for IL-4 and IL-4delta2 in the pathogenesis of tuberculosis and their ratio as a possible marker of disease activity. The specific antigens inducing the IL-4 response require identification to facilitate future vaccine development strategies.