[Focal mycobacterial lymphadenitis after starting highly active antiretroviral therapy]

Efficacy of Rifabutin-Loaded Microspheres for Treatment ofMycobacterium Avium-Infected Macrophages and Mice

Two poly(DL-lactide-co-glycolide) microsphere formulations (A, 10% wt/wt, and B, 23% wt/wt, 1-10 microns) were evaluated for intracellular delivery of rifabutin using the J774 murine and Mono Mac 6 (MM6) human monocytic cell lines. Within 7 days, formulation A released 100% in both cell lines and B released 53 and 67% in the J774 and MM6, respectively. Intracellular release of rifabutin with both formulations caused significant reduction of intracellularly replicating Mycobacterium avium (MAC). In MAC-infected beige mice, formulation B (50 mg, intraperitoneal days 0 and 7) completely eliminated infection by 21 days (p < 0.001), similar to a rifabutin daily oral regimen.

Evidence base for using corticosteroids to treat HIV-associated immune reconstitution syndrome

Most of the evidence supporting the use of corticosteroids (steroids) for immune reconstitution syndrome (IRS) comes from case reports or retrospective series and is of low quality. However, when steroids are used, they have usually been associated with clinical improvement or resolution of IRS. Except in the case of hepatitis B- or C-associated IRS, there have been no reports of worsening of the IRS or adverse outcome due to steroid use. After ruling out other conditions which can mimic IRS, clinicians should strongly consider steroids when managing IRS associated with mycobacterial or fungal pathogens when there is severe disease, or when other measures have failed.

Immune restoration disease after antiretroviral therapy

Suppression of HIV replication by highly active antiretroviral therapy (HAART) often restores protective pathogen-specific immune responses, but in some patients the restored immune response is immunopathological and causes disease [immune restoration disease (IRD)]. Infections by mycobacteria, cryptococci, herpesviruses, hepatitis B and C virus, and JC virus are the most common pathogens associated with infectious IRD. Sarcoid IRD and autoimmune IRD occur less commonly. Infectious IRD presenting during the first 3 months of therapy appears to reflect an immune response against an active (often quiescent) infection by opportunistic pathogens whereas late IRD may result from an immune response against the antigens of non-viable pathogens. Data on the immunopathogenesis of IRD is limited but it suggests that immunopathogenic mechanisms are determined by the pathogen. For example, mycobacterial IRD is associated with delayed-type hypersensitivity responses to mycobacterial antigens whereas there is evidence of a CD8 T-cell response in herpesvirus IRD. Furthermore, the association of different cytokine gene polymorphisms with mycobacterial or herpesvirus IRD provides evidence of different pathogenic mechanisms as well as indicating a genetic susceptibility to IRD. Differentiation of IRD from an opportunistic infection is important because IRD indicates a successful, albeit undesirable, effect of HAART. It is also important to differentiate IRD from drug toxicity to avoid unnecessary cessation of HAART. The management of IRD often requires the use of anti-microbial and/or anti-inflammatory therapy. Investigation of strategies to prevent IRD is a priority, particularly in developing countries, and requires the development of risk assessment methods and diagnostic criteria.

Immune reconstitution in HIV-infected patients

The prognosis of patients infected with human immunodeficiency virus (HIV) type 1 has dramatically improved since the advent of potent antiretroviral therapies (ARTs), which have enabled sustained suppression of HIV replication and recovery of CD4 T cell counts. Knowledge of the function of CD4 T cells in immune reconstitution was derived from large clinical studies demonstrating that primary and secondary prophylaxis against infectious agents, such as Pneumocystis jirovecii (Pneumocystis carinii), Mycobacterium avium complex, cytomegalovirus, and other pathogens, can be discontinued safely once CD4 T cell counts have increased beyond pathogen-specific threshold levels (usually >200 CD4 T cells/mm3) for 3-6 months. The downside of immune reconstitution is an inflammatory syndrome occurring days to months after the start of ART, with outcomes ranging from minimal morbidity to fatal progression. This syndrome can be elicited by infectious and noninfectious antigens. Microbiologically, the possible pathogenic pathways involve recognition of antigens associated with ongoing infection or recognition of persisting antigens associated with past (nonreplicating) infection. Specific antimicrobial therapy, nonsteroidal anti-inflammatory drugs, and/or steroids for managing immune reconstitution syndrome should be considered.

Treatment of Mycobacterium avium complex immune reconstitution disease in HIV-1-infected individuals

Immune reconstitution disease caused by Mycobacterium avium complex (MAC) infection presenting shortly after the introduction of highly active antiretroviral therapy (HAART) has been reported with increasing frequency in persons with HIV-1 infection during the past several years. Several therapeutic modalities have been utilized for this entity, but the optimal means of treating MAC immune reconstitution disease remains unclear. We now describe a patient who underwent some of these therapies. We then review the therapeutic outcomes from the numerous case reports of this disorder. Finally, we propose recommendations and a clinical algorithm regarding the optimal means of treatment of MAC immune reconstitution disease during HIV-1 infection.

Mycobacterium avium complex promotes recruitment of monocyte hosts for HIV-1 and bacteria

In lymphoid tissues coinfected with Mycobacterium avium complex (MAC) and HIV-1, increased viral replication has been observed. This study investigates the role of MAC in perpetuating both infections through the recruitment of monocytes as potential new hosts for bacteria and HIV-1. Increased numbers of macrophages were present in the lymph nodes of patients with dual infection as compared with lymph nodes from HIV(+) patients with no known opportunistic pathogens. In a coculture system, monocyte-derived macrophages were treated with HIV-1 or M. avium and its constituents to further define the mechanism whereby MAC infection of macrophages initiates monocyte migration. Monocyte-derived macrophages treated with bacteria or bacterial products, but not HIV-1, induced a rapid 2- to 3-fold increase in recruitment of monocytes. Pretreatment of the monocytes with pertussis toxin inhibited the migration of these cells, indicating a G protein-linked pathway is necessary for induction of chemotaxis and thus suggesting the involvement of chemokines. Analysis of chemokine mRNA and protein levels from M. avium-treated cultures revealed MAC-induced increases in the expression of IL-8, macrophage-inflammatory protein (MIP)-1alpha, and MIP-1beta with donor-dependent changes in monocyte chemotactic protein-1. Pyrrolidine dithiocarbamate, an antioxidant, inhibited the activation of NF-kappaB and significantly diminished the MAC-induced chemotaxis, concurrently lowering the levels of monocyte chemotactic protein-1 and MIP-1beta. These data demonstrate that MAC induces macrophage production of multiple chemotactic factors via NF-kappaB to promote monocyte migration to sites of MAC infection. In vivo, opportunistic infection may act as a recruitment mechanism in which newly arrived monocytes serve as naive hosts for both MAC and HIV-1, thus perpetuating both infections.