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Robert S Wallis

Publications and source records attributed to Robert S Wallis.

18 recordsLinked to original sources
PubMed2006

Tumor-necrosis-factor blockers: differential effects on mycobacterial immunity.

BACKGROUND: Tumor necrosis factor (TNF) plays a pathogenic role in rheumatoid arthritis but is essential for antimycobacterial host defenses. The risk of reactivation of latent Mycobacterium tuberculosis infection is greater with the TNF monoclonal antibody infliximab than with the soluble TNF receptor etanercept. The basis of this difference is not known. METHODS: The effects that the monoclonal antibodies infliximab and adalimumab and the receptor etanercept have on antimycobacterial immune functions were studied by use of therapeutic drug concentrations in whole-blood culture. RESULTS: Infliximab and adalimumab reduced the proportion of tuberculosis-responsive (CD69(+)) CD4 cells by 70% and 49%, respectively (P<.05), and suppressed antigen-induced interferon (IFN)- gamma production by 70% and 64% (P<.05), respectively; in contrast, etanercept produced no significant effect. Interleukin-10 production was equally suppressed by all 3 drugs. Adalimumab and etanercept had divergent, concentration-dependent effects on control of intracellular growth of M. tuberculosis. None of the drugs induced significant levels of apoptosis or necrosis, in either monocytes or T cells. CONCLUSIONS: The tuberculosis risk posed by infliximab may reflect its combined effects on TNF and IFN- gamma .

Adalimumab↗
PubMed2005

Reactivation of latent granulomatous infections by infliximab.

Although infliximab and etanercept share tumor necrosis factor (TNF) as a common therapeutic target, accumulating data indicate that infliximab (an anti-TNF monoclonal antibody) poses a greater risk of reactivation of latent granulomatous infections than does etanercept (a soluble TNF receptor). Similarly, infliximab is effective for the treatment of chronic granulomatous inflammatory conditions (e.g., Crohn disease) for which etanercept is ineffective. The ability of infliximab to disrupt established granulomas may be distinct from its ability to neutralize soluble TNF. Further research to elucidate the mechanism of the antigranuloma activity of infliximab is warranted.

Antibodies, Monoclonal↗
PubMed2005

Reconsidering adjuvant immunotherapy for tuberculosis.

BACKGROUND: Shortened regimens for treatment of pulmonary tuberculosis (TB) are urgently needed to facilitate its global eradication. Prolonged treatment is presently required to prevent relapse, which is thought to arise from persisting foci of semidormant infection contained within granulomas. METHODS: The medical literature was reviewed to identify clinical trials of adjuvant TB immunotherapy, as well as other studies of the relationship between immune status and TB relapse or reactivation. RESULTS: Four studies of therapeutic interferon indicated its inability to effectively augment the mycobactericidal capacity of lung macrophages. One randomized, placebo-controlled trial of therapeutic interleukin-2 found that it delayed the microbiologic response to treatment, whereas 2 controlled trials of anti-tumor necrosis factor (TNF) therapies (high-dose prednisolone and etanercept [a soluble TNF receptor]) found that these interventions significantly accelerated the response to treatment. Four retrospective studies were identified in which the response to TB therapy was accelerated and/or the relapse risk was reduced in persons with human immunodeficiency virus coinfection; one study reported that immune reconstitution syndrome due to use of antiretroviral therapy was associated with increased risk of relapse. Several studies indicated that granulomas may be efficiently targeted and disrupted by the anti-TNF antibody infliximab, apparently because of its ability to bind to cell-surface TNF and to induce apoptosis in TNF-expressing cells. CONCLUSIONS: These findings support the hypothesis that the granulomatous host response to TB may paradoxically protect sequestered mycobacteria from administered anti-TB therapy and that treatment may be improved by therapeutic disruption of granulomas. Clinical trials to test this hypothesis are warranted.

Antitubercular Agents↗
PubMed2005

Immunoadjuvant prednisolone therapy for HIV-associated tuberculosis: a phase 2 clinical trial in Uganda.

Background. Human immunodeficiency virus (HIV)-infected patients with tuberculosis (TB) respond to effective antituberculous therapy, but their prognosis remains poor. Mounting evidence from clinical studies supports the concept of copathogenesis in which immune activation that is triggered by TB and mediated by cytokines stimulates viral replication and worsens HIV infection, especially when immune function is preserved.Methods. We performed a phase 2, randomized, double-blind, placebo-controlled clinical trial in Kampala, Uganda, to determine whether immunoadjuvant prednisolone therapy in HIV-infected patients with TB who have CD4(+) T cell counts >/=200 cells/ mu L is safe and effective at increasing CD4(+) T cell counts.Results. Short-term prednisolone therapy reduced levels of immune activation and tended to produce higher CD4(+) T cell counts. Although prednisolone therapy was associated with a more rapid clearance of Mycobacterium tuberculosis from the sputum, it was also associated with a transient increase in HIV RNA levels, which receded when prednisolone therapy was discontinued. The intervention worsened underlying hypertension and caused fluid retention and hyperglycemia.Conclusion. The benefits of prednisolone therapy on immune activation and CD4(+) T cell counts do not outweigh the risks of adverse events in HIV-infected patients with TB and preserved immune function.

AIDS-Related Opportunistic Infections↗
PubMed2005

Tumor necrosis factor and granuloma biology: explaining the differential infection risk of etanercept and infliximab.

Several studies show that the risk of granulomatous infections following therapy with the anti-tumor necrosis factor (TNF) antibody infliximab is higher than after treatment with the soluble TNFRp75 immunoglobulin fusion construct etanercept. Therefore, despite sharing a common target, it is possible that the actual mode of action of the 2 biologicals differs in vivo. TNF is known to participate in the induction and maintenance of protective granulomas at multiple steps, and evidence supporting a differential inhibition of TNF bioactivity and signaling by the 2 drugs is discussed.

Animals↗
PubMed2005

Clinical, microbiological, and immunological characteristics in HIV-infected subjects at risk for disseminated Mycobacterium avium complex disease: an AACTG study.

The clinical, microbiologic, and immunologic parameters in HIV-infected subjects first presenting with disseminated Mycobacterium avium complex (DMAC) were determined. Four HIV-positive groups not yet on DMAC treatment were enrolled: 19 subjects with CD4 lymphocyte counts < or =50/microl thought to have DMAC on clinical grounds; 18 subjects newly found to have a positive blood culture for MAC; 25 asymptomatic controls (CD4 cell counts < or =50); and 25 asymptomatic controls (CD4 counts 100-250/microl). Outcome measures include comparisons between groups for clinical characteristics; results of cultures from blood, marrow, and gastrointestinal and respiratory tracts; immunological markers from staining of marrow and flow cytometry of circulating lymphocytes; and cytokine production of PBMCs. Only 21% of the 19 patients entered on suspicion of having DMAC grew MAC from blood or marrow. Neither clinical presentation nor laboratory tests differentiated those culture-positive from those culture-negative patients. However, prior PCP or multiple other opportunistic infections were more common in the DMAC group. MAC was isolated from 82% of marrow and 50% of blood specimens from the DMAC group. Respiratory or gastrointestinal colonization was present in 36% of DMAC subjects, but only 5% of non-DMAC subjects with CD4 counts <50 cells/microl. CD8+ cells were more frequent in bone marrow, and CD4 cells recognizing MAC antigen were more frequent in blood from DMAC subjects vs. controls. Results suggest an early stage of tissue dissemination preceding persistent bacteremia, and mucosal entry without persistence of colonization. MAC-specific T cell responses apparently develop and persist during DMAC, but are dysfunctional or too infrequent to prevent persistence.

Adult↗
PubMed2005

Survival and replication of clinical Mycobacterium tuberculosis isolates in the context of human innate immunity.

The initial host response to Mycobacterium tuberculosis is driven by innate immunity. For this study, we examined the ability of 18 recent clinical isolates and 5 reference strains to survive and replicate in the context of host innate immunity by using whole blood culture. Six healthy tuberculin-negative volunteers served as subjects. H(37)Ra showed the least capacity to replicate of any of the strains tested, decreasing in viability 1.3 log CFU during 72 h of whole blood culture, whereas H(37)Rv increased 0.32 log. Clinical isolates varied greatly in their ability to replicate in blood cells, ranging from -0.4 to +0.8 log (P < 0.001). Four showed significantly more growth than H(37)Rv, and one showed significantly reduced growth. Host mechanisms for restricting intracellular mycobacterial growth were more effective during the first 24 h of whole blood culture than during the 24- to 72-h period. Certain mycobacterial isolates appeared preferentially able to withstand host defenses during each of these intervals. Although there was relatively more homogeneity among subjects than among strains, one of the six subjects showed a reduced capacity to restrict intracellular mycobacterial growth due to a defect expressed during the first 24 h of culture. Our findings indicate substantial variability in the capacity of clinical tuberculosis isolates to replicate in host cells in the face of innate host immunity.

Blood↗
PubMed2005

Sutton's law.

Explore the source record for details and available documents.

Eponyms↗
PubMed2004

A study of the safety, immunology, virology, and microbiology of adjunctive etanercept in HIV-1-associated tuberculosis.

OBJECTIVE: Tumor necrosis factor (TNF), an important inflammatory mediator in tuberculosis, has been implicated in causing accelerated HIV disease progression in HIV-associated tuberculosis. However, TNF blockade, particularly by monoclonal antibody, has been associated with the reactivation of latent Mycobacterium tuberculosis infection by the impairment of mycobacterial immunity. This phase 1 study examined the safety, microbiology, immunology, and virology of TNF blockade using etanercept (soluble TNF receptor, Enbrel) during the initial treatment of HIV-associated tuberculosis. DESIGN: A single-arm trial, with key endpoints compared with historical controls, conducted in Mulago Hospital, Kampala, Uganda. SUBJECTS: : Sixteen HIV-1-infected patients and 42 CD4-frequency-matched controls with sputum smear-positive tuberculosis and CD4 cell counts > 200 cells/microl. INTERVENTION: Etanercept 25 mg, eight doses administered subcutaneously twice weekly beginning on day 4 of tuberculosis therapy. MAIN OUTCOME MEASURES: Serial examination, radiography, sputum culture, CD4 T-cell counts, plasma log10 HIV-RNA copy numbers. RESULTS: Trends towards superior responses to tuberculosis treatment were evident in etanercept-treated subjects in body mass, performance score, number of involved lung zones, cavitary closure, and time to sputum culture conversion. Etanercept treatment resulted in a 25% increase in CD4 cells by week 4 (P = 0.1 compared with controls). The change in CD4 cell count was inversely related to the change in serum neopterin, a marker of macrophage activation. There was no effect on plasma HIV RNA. CONCLUSION: Etanercept can be safely administered during the initial treatment of pulmonary tuberculosis. Further studies are warranted to examine the effects of etanercept on T-cell numbers, activation and apoptosis in AIDS and tuberculosis.

AIDS-Related Opportunistic Infections↗
PubMed2004

Lack of activity of orally administered clofazimine against intracellular Mycobacterium tuberculosis in whole-blood culture.

The activity of oral clofazimine against intracellular Mycobacterium tuberculosis was compared to that of ofloxacin in healthy volunteers by the use of whole-blood cultures. Clofazimine was inactive whether it was tested alone or combined with other drugs that are used to treat multidrug-resistant tuberculosis, despite a total dose of 2 g. Kanamycin was the most active drug tested.

Anti-Infective Agents↗
PubMed2003

A study of the immunology, virology, and safety of prednisone in HIV-1-infected subjects with CD4 cell counts of 200 to 700 mm(-3).

Adult Clinical Trials Group Study 349 examined the immunology, virology, and safety of 40 mg/d prednisone as an adjunct to antiretroviral therapy in 24 HIV-infected subjects with >200 CD4+ T cells/mm in a randomized placebo-controlled trial. After 8 weeks, median lymphocyte and CD4+ cell numbers increased >40% above baseline values (p =.08). No effect was observed on markers of cell activation or apoptosis, although the proportion of CD28+ CD8+ T cells increased (p =.006). Prednisone inhibited monocyte TNFalpha production without affecting T-cell responses to antigens or mitogens. Two subjects assigned to prednisone were subsequently found to have asymptomatic osteonecrosis of the hip. Many questions remain regarding the role of activation-induced sequestration and apoptosis as causes of progressive CD4+ T-cell loss in AIDS. The potential role of corticosteroids as tools to examine this question will be limited by concerns regarding their toxicity; however, further studies of other agents to limit cellular activation in AIDS are warranted.

Adult↗
PubMed2003

Whole blood bactericidal activity during treatment of pulmonary tuberculosis.

The timely evaluation of new drugs that can be used to shorten tuberculosis (TB) treatment will require surrogate markers for relapse. This study examined bactericidal activity against intracellular Mycobacterium tuberculosis in whole blood culture (whole blood bactericidal activity; WBA) during TB treatment. In the absence of chemotherapy, immune mechanisms in patient blood resulted in bacteriostasis, whereas administration of oral chemotherapy resulted in bacillary killing. Total WBA per dose was greater during the intensive phase of treatment than during the continuation phase (mean, -2.32 vs. -1.67 log(10) cfu-days, respectively; P<.001). Cumulative WBA throughout treatment was greater in subjects whose sputum cultures converted to negative by the eighth week of treatment than in those for whom conversion was delayed (mean, -365 vs. -250 log(10) cfu-days; P=.04) and correlated with the rate of decrease of sputum colony-forming unit counts during the first 4 weeks of treatment (P=.018), both of which are indicative of prognosis. These findings indicate that measurement of WBA may have a role in assessing the sterilizing activity of new anti-TB drugs.

Adolescent↗
PubMed2002

Bactericidal activity in whole blood as a potential surrogate marker of immunity after vaccination against tuberculosis.

The development of new tuberculosis (TB) vaccines will require the identification of correlates of human protection. This study examined the balance between immunity and virulence in a whole blood infection model in which intracellular mycobacterial survival was measured using BACTEC. In the blood of tuberculin-negative donors, counts of Mycobacterium tuberculosis H(37)Ra organisms fell by 0.14 log(10) CFU during 96 h of whole blood culture, whereas counts of Mycobacterium bovis BCG, M. tuberculosis H(37)Rv, and a clinical TB isolate's organisms increased by 0.13, 0.43, and 1.04 log(10) CFU, respectively (P < 0.001), consistent with their relative virulence. Inhibition of tumor necrosis factor alpha by the addition of methylprednisolone or pentoxifylline or removal of CD4(+) or CD8(+) T cells by magnetic beads had deleterious effects on immune control of intracellular growth only in the blood of tuberculin-positive donors. Repeated vaccination of eight tuberculin-negative volunteers with M. bovis BCG resulted in a 0.3 log (50%) reduction in BCG CFU counts in the model compared to baseline values (P < 0.05). Three of the volunteers responded only after the second vaccination. These experiments indicate that whole blood culture may be used to measure immunity to M. tuberculosis and that further studies of repeated BCG vaccination are warranted.

Adult↗