The species Mycobacterium africanum in the light of new molecular markers.

The findings of recent studies addressing the molecular characteristics of Mycobacterium tuberculosis complex isolates have initiated a discussion on the classification of M. africanum, especially of those isolates originating from East Africa (cluster F, subtype II) and displaying phenotypic and biochemical characteristics more similar to those of M. tuberculosis. To further address this question, we analyzed a representative collection of 63 M. tuberculosis complex strains comprising 30 M. africanum subtype I strains, 20 M. africanum subtype II strains, 10 randomly chosen M. tuberculosis isolates, and type strains of M. tuberculosis, M. bovis, and M. africanum for the following biochemical and molecular characteristics: single-nucleotide polymorphisms (SNPs) in gyrB and narGHJI and the presence or absence of RD1, RD9, and RD12. For all molecular markers analyzed, subtype II strains were identical to the M. tuberculosis strains tested. In contrast, the subtype I strains as well as the M. africanum type strain showed unique combinations of SNPs in gyrB and genomic deletions (the absence of RD9 and the presence of RD12), which proves their independence from M. tuberculosis and M. bovis. Accordingly, all subtype I strains displayed main biochemical characteristics included in the original species description of M. africanum. We conclude that the isolates from West Africa were proved to be M. africanum with respect to the phenotypic and genetic markers analyzed, while the isolates from East Africa must be regarded as phenotypic variants of M. tuberculosis (genotype Uganda). We propose the addition of the molecular characteristics defined here to the species description of M. africanum, which will allow clearer species differentiation in the future.

Mycobacterium africanum subtype II is associated with two distinct genotypes and is a major cause of human tuberculosis in Kampala, Uganda.

The population structure of 234 Mycobacterium tuberculosis complex strains obtained during 1995 and 1997 from tuberculosis patients living in Kampala, Uganda (East Africa), was analyzed by routine laboratory procedures, spoligotyping, and IS6110 restriction fragment length polymorphism (RFLP) typing. According to biochemical test results, 157 isolates (67%) were classified as M. africanum subtype II (resistant to thiophen-2-carboxylic acid hydrazide), 76 isolates (32%) were classified as M. tuberculosis, and 1 isolate was classified as classical M. bovis. Spoligotyping did not lead to clear differentiation of M. tuberculosis and M. africanum, but all M. africanum subtype II isolates lacked spacers 33 to 36, differentiating them from M. africanum subtype I. Moreover, spoligotyping was not sufficient for differentiation of isolates on the strain level, since 193 (82%) were grouped into clusters. In contrast, in the IS6110-based dendrogram, M. africanum strains were clustered into two closely related strain families (Uganda I and II) and clearly separated from the M. tuberculosis isolates. A further characteristic of both M. africanum subtype II families was the absence of spoligotype spacer 40. All strains of family I also lacked spacer 43. The clustering rate obtained by the combination of spoligotyping and RFLP IS6110 analysis was similar for M. africanum and M. tuberculosis, as 46% and 49% of the respective isolates were grouped into clusters. The results presented demonstrate that M. africanum subtype II isolates from Kampala, Uganda, belong to two closely related genotypes, which may represent unique phylogenetic branches within the M. tuberculosis complex. We conclude that M. africanum subtype II is the main cause of human tuberculosis in Kampala, Uganda.

Pulmonary mononuclear cell responses to antigens of Mycobacterium tuberculosis in healthy household contacts of patients with active tuberculosis and healthy controls from the community.

Protective immunity against Mycobacterium tuberculosis requires CD4+ lymphocyte-mediated immune responses and IFN-gamma activity. As the primary portal of entry of M. tuberculosis is the lung, pulmonary immune responses against multiple M. tuberculosis Ags were compared between both M. tuberculosis-exposed tuberculin skin test-positive healthy household contacts (HHC) of patients with active sputum smear and culture-positive tuberculosis and tuberculin skin test-positive healthy control individuals from the community (CC). Frequencies of M. tuberculosis Ag-specific IFN-gamma-producing cells, IFN-gamma concentrations in culture supernatants, and DNA synthesis in bronchoalveolar cells (BAC) and PBMC were studied in HHC (n = 10) and CC (n = 15). Using enzyme-linked immunospot assay we found higher frequencies of IFN-gamma-producing cells with specificity to M. tuberculosis-secreted Ag 85 (Ag 85) in BAC from HHC than in BAC from CC (p < 0.022) and relative to autologous PBMC, indicating compartmentalization of Ag 85-specific cells to the lungs. Further, IFN-gamma-producing cells with specificity to components A and B of Ag 85 were specifically compartmentalized to the lungs in HHC (p < 0. 05). IFN-gamma concentrations in culture supernatants of BAC and Ag-specific DNA synthesis were low and comparable in the two subject groups. Increased immune responses to Ag 85 at the site of repeated exposure to M. tuberculosis (the lung) may represent an important component of protective immunity against M. tuberculosis. Correlates of protective immunity against M. tuberculosis are required for assessment of the efficiency of anti-tuberculous vaccines.

Depressed T-cell interferon-gamma responses in pulmonary tuberculosis: analysis of underlying mechanisms and modulation with therapy.

Immunological and clinical profiles were evaluated in 2 groups: human immunodeficiency virus (HIV)-uninfected and HIV-infected patients, with newly diagnosed pulmonary tuberculosis (TB), and tuberculin-skin-test-reactive healthy control subjects. HIV-uninfected patients with TB were also followed up longitudinally during and after chemotherapy. At the time of diagnosis, purified protein derivative (PPD)-stimulated production of interferon (IFN)-gamma by peripheral blood mononuclear cells from TB patients was depressed, compared with that of healthy control subjects, whereas levels of transforming growth factor (TGF)-beta and interleukin (IL)-10 were increased. In longitudinal studies, PPD stimulated production of IL-10 and TGF-beta returned to baseline by 3 months, whereas IFN-gamma production remained depressed for at least 12 months. These data indicate that the immunosuppression of TB is not only immediate and apparently dependent (at least in part) on immunosuppressive cytokines early during the course of Mycobacterium TB infection but is also long lasting, presumably relating to a primary abnormality in T-cell function.

Enhanced responses to Mycobacterium tuberculosis antigens by human alveolar lymphocytes during active pulmonary tuberculosis.

Responses to mycobacterial and nonmycobacterial antigens were examined in bronchoalveolar cells (BAC) and peripheral blood mononuclear cells (PBMC) from patients with active pulmonary tuberculosis (n=16) and healthy subjects (n=23). DNA synthesis in BAC (but not PBMC) from tuberculosis patients was significantly increased in response to the mycobacterial antigens purified protein derivative (PPD), antigen 85, and mannose-capped lipoarabinomannan but not to nonmycobacterial antigens. The response to PPD was also increased in enriched alveolar lymphocytes from tuberculosis patients (P<.05). The frequency of interferon-gamma but not interleukin-4- or -10-producing cells by ELISAspot was increased in PPD-stimulated BAC from patients with tuberculosis (P<.05). Accessory function of alveolar macrophages for T lymphocyte responses was similar and suppressive activity was variably decreased in tuberculosis patients. Thus, there is compartmentalization of mycobacterial antigen-specific lymphocytes to the lungs during active tuberculosis that on challenge produce a Th1-type cytokine host response.

Chemokines induced by infection of mononuclear phagocytes with mycobacteria and present in lung alveoli during active pulmonary tuberculosis.

The capacity of Mycobacterium tuberculosis (MTB) to induce production of chemokines with known chemotactic activity for monocytes and lymphocytes, the cellular building blocks of granulomas, was investigated. These chemokines included regulated upon activation, normal T cell expressed and secreted (RANTES), monocyte chemotactic protein-1 (MCP-1), and macrophage inflammatory protein-1alpha (MIP-1alpha). MTB stimulated production of MCP-1 and MIP-1alpha by blood monocytes (MN) and alveolar macrophages (AM). MTB infection of MN and AM stimulated release but not production of RANTES. AM produced or released significantly higher levels than MN of RANTES (by 2.1-fold), MCP-1 (by 6.9-fold), and MIP-1alpha (by 5. 5-fold) (P < 0.05 for each). This study also confirmed that MTB-infected AM produce the chemokine interleukin (IL)-8. MTB infection of AM resulted in increased steady-state expression of messenger RNA (mRNA) for MCP-1 and MIP-1alpha and minimal increased expression of RANTES mRNA. Both an avirulent (H37Ra) and a virulent (H37Rv) strain of MTB and purified protein derivative of H37Rv but not latex beads induced production of chemokines. Supernatants of MTB-infected cells demonstrated chemotactic activity for both monocytes and lymphocytes partially inhibitable by neutralizing antibodies against the chemokines studied. Bronchoalveolar lavage fluid from patients with active pulmonary tuberculosis as compared with healthy control subjects contained increased levels of RANTES (by 8-fold), MCP-1 (by 2.7-fold), and IL-8 (by 8.9-fold) (P < 0.05), but not MIP-1alpha, as compared with healthy control subjects. Thus, multiple chemokines may be involved in recruitment of cells for granuloma formation in tuberculosis.

Human alveolar T lymphocyte responses to Mycobacterium tuberculosis antigens: role for CD4+ and CD8+ cytotoxic T cells and relative resistance of alveolar macrophages to lysis.

T cell-mediated cytotoxicity against Mycobacterium tuberculosis (MTB)-infected macrophages may be a major mechanism of specific host defense, but little is known about such activities in the lung. Thus, the capacity of alveolar lymphocyte MTB-specific cell lines (AL) and alveolar macrophages (AM) from tuberculin skin test-positive healthy subjects to serve as CTL and target cells, respectively, in response to MTB (H37Ra) or purified protein derivative (PPD) was investigated. Mycobacterial Ag-pulsed AM were targets of blood CTL activity at E:T ratios of > or = 30:1 (51Cr release assay), but were significantly more resistant to cytotoxicity than autologous blood monocytes. PPD- plus IL-2-expanded AL and blood lymphocytes were cytotoxic for autologous mycobacterium-stimulated monocytes at E:T ratios of > or = 10:1. The CTL activity of lymphocytes expanded with PPD was predominantly class II MHC restricted, whereas the CTL activity of lymphocytes expanded with PPD plus IL-2 was both class I and class II MHC restricted. Both CD4+ and CD8+ T cells were enriched in BL and AL expanded with PPD and IL-2, and both subsets had mycobacterium-specific CTL activity. Such novel cytotoxic responses by CD4+ and CD8+ T cells may be a major mechanism of defense against MTB at the site of disease activity.

Diversity of the vif gene of human immunodeficiency virus type 1 in Uganda.

Little sequence information is available for human immunodeficiency virus type 1 (HIV-1) vif genes of African origin. Here we describe 37 new complete vif genes of 18 AIDS patients from Uganda and show that vif has a high in vivo genetic variability. vif proviral DNA sequences of peripheral blood cells were determined by direct sequencing of PCR products. Only 52% of the deduced Vif amino acids were absolutely conserved; when Vif sequences previously analysed were considered, only 32% of the Vif consensus sequence comprised conserved and as such possibly functionally important motifs. The high inter-individual vif variability was in contrast to a very low intra-individual variability. One patient carried a vif gene with a stable C-terminal deletion, but N-terminal truncations were not found in patients' predominant vif sequences. The vif genes analysed comprised subtypes A, D and an A/D mosaic. Phylogenetic analyses additionally showed that HIV- 1 in Uganda has spread across the boundaries of ethnic groups.

Examining a paradox in the pathogenesis of human pulmonary tuberculosis: immune activation and suppression/anergy.

Protective immunity against Mycobacterium tuberculosis (MTB) in animal models is based on cell-mediated immunity (CMI), involving bi-directional interactions between T cells and cells of the monocyte/macrophage (MO/MA) lineage. Key factors include MO-derived interleukin (IL)-12 and tumor necrosis factor (TNF)-alpha as well as T cell derived IL-2 and interferon (IFN)-gamma. These cytokines appear particularly crucial in the induction of MA-mediated elimination of mycobacteria. Several lines of evidence indicate that similar mechanisms are operating in humans. During active pulmonary tuberculosis (PTB), signs of both immune depression and immune activation are concomitantly present. Decreased tuberculin skin test reactivity in vivo and deficient IFN-gamma production by MTB-stimulated mononuclear cells in vitro are observed. On the other hand, the serum levels of several cytokines, including TNF, and other inflammatory mediators are increased and circulating MO and T cell show phenotypic and functional evidence of in vivo activation. In this review, we will discuss the evidence for three models, which could explain this apparent paradox: 1. Stimulation of the T cell-suppressive function from MO/MA; 2. Intrinsic T cell refractoriness, possibly associated with tendency to apoptosis (programmed cell death), and 3. Compartmentalization and redistribution of immune responses to the site of disease. The opportunistic behavior of MTB during human immunodeficiency virus (HIV) infection can be explained by suppression of type-1 responses at the level of antigen-presenting cells, CD4 T cells and effector macrophages. The ominous prognostic significance of intercurrent PTB during HIV infection seems primarily due to prolonged activation of HIV replication in macrophages. Supportive immune therapy during PTB could aim at correcting the type-1 deficiency either by IFN-gamma inducers (e.g. IL-12, IL-18) or by neutralizing the suppressive cytokines transforming growth factor beta (TGF-beta) and IL-10. Alternatively, inflammatory over-activity could be reduced by neutralizing TNF. Finally, anti-apoptotic therapies (e.g. IL-15) might be considered.

Clinical course of human immunodeficiency virus type 1 associated pulmonary tuberculosis during short-course antituberculosis therapy.

To describe the clinical response to antituberculosis therapy in HIV-1 disease, 49 HIV-1 positive Ugandan adults (mean age 29.4 years; 68% men) with active pulmonary tuberculosis (PTB) were studied in a trial of rifampicin containing short-course antituberculosisis regimens. At presentation, 18 patients were PPD non-reactors (PPD skin test induration < 2mm), ten patients (20%) had non-cavitary lung disease. The mean CD4 lymphocyte count at presentation was 339/microliters (+/- SD 275). Among patients with abnormal baseline clinical values, the median time to resolution of fever, weight gain of 10%, increase of haemoglobin to 10g/dl and of Karnofsky performance score (KPS) to 80 occurred before sputum smear and culture conversion. Short-term survival was associated with: baseline lymphocytes < 1200/microliters, (Odds ratio (OR) 17.5), CD4+ lymphocytes < 200/microliters (OR 9.8), cavitary lung disease, (OR 0.6), atypical chest radiograph, (OR 6.7), and PPD non-reactivity, (OR 13.5), PPD non-reactivity and non-cavitary disease were associated with significantly lower CD4 lymphocyte counts. Affordable serial measurements parallel the response to therapy and predict survival in HIV-associated PTB.

PIP: Tuberculosis (TB) is the most often seen and serious opportunistic infection in HIV-1-infected individuals in developing countries. Infection with HIV-1 predisposes individuals to TB, both progressive primary and reactivation disease. To describe the clinical response to anti-TB therapy in HIV-1 disease, 49 HIV-1-positive Ugandan adults of mean age 29.4 years with active pulmonary TB (PTB) were studied in a trial of rifampicin containing short-course anti-TB regimens. At presentation, 18 patients were PPD skin test nonreactive, and 39 had cavitary lung disease. The mean CD4 lymphocyte count at presentation was 339/mcl. Among patients with abnormal baseline clinical values, the median time to resolution of fever, weight gain of 10%, increase of hemoglobin to 10 g/dl, and Karnofsky performance score (KPS) to 80 occurred before sputum smear and culture conversion. Short-term survival was associated with baseline lymphocytes of less than 1200/mcl, cavitary lung disease, atypical chest radiograph, and PPD nonreactivity. PPD nonreactivity and noncavitary disease were associated with significantly lower CD4 lymphocyte counts. Study findings demonstrate that the careful monitoring of clinical symptoms and simple, inexpensive, and widely available laboratory markers permit the satisfactory evaluation of early clinical response to anti-TB therapy in HIV-1-infected patients with pulmonary TB.

Tuberculosis among European patients with the acquired immune deficiency syndrome. The AIDS in Europe Study Group.

OBJECTIVES: To describe the characteristics of acquired immune deficiency syndrome (AIDS) patients with tuberculosis in Europe; to assess the incidence and risk factors of tuberculosis after AIDS; to compare survival of AIDS patients with and without extra-pulmonary tuberculosis (EPTB) at the time of AIDS diagnosis. DESIGN: Multicentric retrospective cohort study of 6544 AIDS patients diagnosed in 52 clinical centres and 17 European countries. METHODS: Description of patient characteristics and comparisons of tuberculosis incidence and mortality after AIDS with multivariate Cox proportional hazard models. RESULTS: 14.6% of AIDS patients had tuberculosis and 78% of those with tuberculosis had EPTB. EPTB was the AIDS-defining condition in 8.7% of the patients. Tuberculosis incidence after AIDS was 3.1 per 100 person-years. Age, gender and HIV-transmission category were not significantly associated with an increased risk of tuberculosis and the strongest risk factor for both EPTB and pulmonary tuberculosis (PTB) was the region of origin. The adjusted hazard ratio of EPTB and PTB in Southern Europe compared to Northern Europe were 5.5 (95% confidence interval [CI]: 5.0-6.1) and 2.0 (CI: 1.4-2.7) respectively. The apparent survival advantage of AIDS patients with EPTB compared to patients diagnosed with other conditions (median survival time: 22 vs 16 months) was statistically not significant when confounding variables were adjusted for (Hazard ratio: 0.85; CI: 0.62-1.07). CONCLUSIONS: In Europe, there are large differences in the incidence of tuberculosis among AIDS patients in different countries. They do not seem to be due to differences in age or in the prevalence of injecting drug use and likely reflect differences in the prevalence of tuberculosis infection. The role of recent transmission should also be considered, and national tuberculosis control efforts and Europe-wide surveillance need to be reinforced accordingly.

T lymphocytic and immature macrophage alveolitis in active pulmonary tuberculosis.

The phenotype of bronchoalveolar cells from 11 healthy subjects and from affected and unaffected lungs of 15 patients with pulmonary tuberculosis (PTB) was determined. An immature macrophage alveolitis was found in the affected lung and the unaffected lung versus controls as determined by morphology and peroxidase activity. T lymphocytic alveolitis also was found in the affected but not the unaffected tuberculous lung compared with healthy controls. The majority of alveolar lymphocytes in unaffected and affected PTB lungs were T cells expressing the alpha beta T cell receptor. Alveolar T cells from both unaffected and affected lungs were activated, as determined by increased expression of CD69 and HLA-DR. Interleukin-2 receptor (IL-2R alpha) expression was, however, unchanged on alveolar lymphocytes from affected lung and was decreased in the unaffected lung. Thus, activated T lymphocytes and immature macrophages in the tuberculous lung are basic to the local immunopathogenesis of PTB.

Epidemiology of AIDS dementia complex in Europe. AIDS in Europe Study Group.

The aim of the study was to describe the epidemiology of AIDS dementia complex (ADC) in Europe and to assess the possible role of zidovudine therapy in preventing or delaying its occurrence. We used an inception cohort, with data collected retrospectively from patients' clinical records from 52 clinical centers in 17 countries across Europe. The subjects were 6,548 adult people with AIDS consecutively diagnosed from 1979 to 1989. The main outcome measures were codiagnosis of ADC at the time of AIDS diagnosis and ADC-free time after AIDS diagnosis. ADC was reported in 295 patients (4.5%) at the time of AIDS diagnosis and during follow-up in a further 402 of the 5,160 patients (7.8%) who were diagnosed with AIDS based on diseases other than ADC. Whether at the time of AIDS diagnosis or later, the occurrence of ADC was significantly associated with age, transmission category, and CD4+ cell counts. The risk was greater in older patients (14 and 19% greater, at AIDS diagnosis and after, respectively, for a 5-year difference in age), in i.v. drug users than in homosexual and bisexual men (89 and 60% greater, at AIDS diagnosis and after, respectively), and for people with lower CD4+ cell counts (14 and 30% greater for a reduction of 1 on the natural log scale). Risk was almost double for women than for men. A significant reduction, of approximately 40%, was found in the risk of developing ADC after AIDS diagnosis for patients receiving zidovudine therapy, but this effect was present only during the first 18 months of treatment, irrespective of whether treatment began before or after AIDS diagnosis. In conclusion, an increase in the risk of developing ADC either at the time of AIDS diagnosis or thereafter is associated with increasing age, i.v. drug use, and decreased CD4+ cell count. Women tend to have a higher risk of ADC at the time of AIDS diagnosis. Zidovudine therapy appears to have a definite, but time-limited, effect of protecting patients against ADC development after AIDS diagnosis.

Alveolar macrophages as accessory cells for human gamma delta T cells activated by Mycobacterium tuberculosis.

Alveolar macrophages form the first line of defense against inhaled droplets containing Mycobacterium tuberculosis by controlling mycobacterial growth and regulating T cell responses. CD4+ and gamma delta T cells, two major T cell subsets activated by M. tuberculosis, require accessory cells for activation. However, the ability of alveolar macrophages to function as accessory cells for T cell activation remains controversial. We sought to determine the ability of alveolar macrophages to serve as accessory cells for resting (HLA-DR-, IL-2R-) and activated (HLA-DR+, IL-2R+) gamma delta T cells in response to M. tuberculosis and its Ag, and to compare accessory cell function for gamma delta T cells of alveolar macrophages and blood monocytes obtained from the same donor. Alveolar macrophages were found to serve as accessory cells for both resting and activated gamma delta T cells in response to M. tuberculosis Ag. At high alveolar macrophage to T cell ratios (> 3:1), however, expansion of resting gamma delta T cells was inhibited by alveolar macrophages. The inhibition of resting gamma delta T cells by alveolar macrophages was dose-dependent, required their presence during the first 24 h, and was partially overcome by IL-2. Alveolar macrophages did not inhibit activated gamma delta T cells even at high accessory cell to T cell ratios, and alveolar macrophages functioned as well as monocytes as accessory cells. Monocytes were not inhibitory for either resting or activated gamma delta T cells. These findings support the following model. In the normal alveolus the alveolar macrophage to T cell ratio is > or = 9:1, and therefore the threshold for resting gamma delta T cell activation is likely to be high. Once a nonspecific inflammatory response occurs, such as after invasion by M. tuberculosis, this ratio is altered, favoring gamma delta T cell activation by alveolar macrophages.

A pilot study of antituberculosis combinations comparing rifabutin with rifampicin in the treatment of HIV-1 associated tuberculosis. A single-blind randomized evaluation in Ugandan patients with HIV-1 infection and pulmonary tuberculosis.

SETTING: This pilot study was conducted at the Joint Clinical Research Centre (JCRC) in Kampala, Uganda, where tuberculosis (TB) is an epidemic health problem aggravated by the HIV-1 pandemic. OBJECTIVE: To evaluate the feasibility of a larger phase III trial utilizing rifabutin as a substitute for rifampicin in short-course therapy for pulmonary TB. DESIGN: Single-blind randomized trial in 50 patients with new onset smear- and culture-positive pulmonary tuberculosis and HIV-1 infection. Comparison of daily, intermittently supervised 6-month treatment regimens of rifabutin versus rifampicin, together with isoniazid, ethambutol and pyrazinamide. RESULTS: Rifabutin- and rifampicin-containing regimens had comparable efficiency. However, rifabutin-treated patients had significantly more rapid clearance of acid-fast bacilli from sputum at 2 months (P < 0.05, Fisher exact test) and over the entire study period (P < 0.05, logrank test) than rifampicin-treated patients. The presence of cavitary disease was associated with a longer sputum conversion time for patients treated with either regimen. No major adverse events requiring dosage reduction or withdrawal of any study medication were seen in either treatment group. Mean absolute peripheral blood CD4 T lymphocyte counts increased by 28% from week 0 to week 12 in all subjects (334-427/microliters, respectively). An unexpected finding was the isolation of Mycobacterium africanum from 49% of the sputum cultures. This is the first report indicating a high prevalence of M. africanum in human TB in Uganda. CONCLUSION: Short-course antituberculosis regimens containing rifabutin or rifampicin are both safe and efficacious in the treatment of HIV-1 associated tuberculosis. Rifabutin-containing regimens were associated with earlier sputum smear and culture conversion.

Phase I/II vaccination study of recombinant peptide F46 corresponding to the HIV-1 transmembrane protein coupled with 2.4 dinitrophenyl (DNP) Ficoll.

In order to evaluate tolerance, toxicity, and in vivo antigenicity, 29 HIV-1-infected patients (eight with ARC and 21 with AIDS) were vaccinated with a synthetic peptide derived from the gp41 transmembrane protein of the HIV-1. This peptide had been coupled with 2.4 dinitrophenyl-Ficoll (F46), a T-cell independent adjuvant. The patients received a single intradeltoid injection of either 0.1 or 0.3 mg of F46. Five of the individuals with AIDS were boostered, four of them twice. Anti-F46 antibody titers were measured before vaccination, and on days 7, 14, 21, 28, 90, 180 and 270 after vaccination. Anti-F46 titers rose at least twofold over prestudy values in 10/21 individuals with AIDS and in 1/8 individuals with ARC at least once during the observation period. The overall response, however, consisted of only weak antibody production that was independent of the dose or patient characteristics. No signs of toxicity or of clinical progression related to the vaccination were observed in this phase I/II trial of a T-cell independent therapeutic vaccine.

Prevalence of antibodies to recombinant virion infectivity factor in the sera of prospectively studied patients with HIV-1 infection.

Two hundred twenty-four sera were collected from 34 HIV-1 infected patients during an observation period of up to 4.5 years (109 patient years of observation). The sera were tested for the presence of antibodies against the HIV-1 virion infectivity factor (vif) protein. Thirty sera from 6 HIV-1 seronegative individuals served as negative controls. The sera were immunoblotted against a recombinant, prokaryotically expressed vif protein. The prevalence of anti-vif antibodies increased significantly with progression of the disease from 18% to 81% (P less than 0.0001) which suggests a possible role of vif in HIV-1 replication and pathogenicity.

Enhancement of monocyte antimycobacterial activity by diethyldithiocarbamate (DTC).

Diethyldithiocarbamate (DTC) has been recently reported to significantly reduce the incidence of opportunistic infections in HIV-infected patients. The present study addresses the question whether DTC is capable of stimulating antimycobacterial activity of mononuclear phagocytes. We found that peripheral blood mononuclear cells (PBMC) of healthy subjects preincubated in vitro with 100-1000 ng/ml of DTC and thereafter infected with Mycobacterium tuberculosis H37Rv or Mycobacterium avium-intracellulare complex exhibited an enhanced antimycobacterial activity compared with control-incubated cells as assessed by the determination of mycobacterial colony-forming units. In subsequent experiments monocytes from healthy volunteers injected with 5 mg/kg body weight of DTC were tested ex vivo for antimycobacterial activity at various periods of time after injection. Injection of DTC resulted in a significant enhancement of antimycobacterial activity which was most evident 24 h after DTC injection. We conclude that DTC stimulates the antimicrobial function of mononuclear phagocytes both in vitro and in vivo. These results may explain the favourable clinical course observed in HIV-infected patients treated with DTC and may serve as a basis for treatment with DTC in patients with drug-resistant atypical mycobacteriosis.