Mycobacterium avium-M. intracellulare is an intracellular pathogen responsible for the highest incidence of disseminated bacterial infection in patients with AIDS. Treatment of the infection is difficult and has been of limited efficacy. Attachment of the organism to macrophages is a critical early step in the establishment of the disease. In the present study, we isolated and identified a receptor that mediates attachment of M. avium-M. intracelulare to human peripheral blood monocytes and monocyte-derived macrophages. On Western blotting, (immunoblotting), the receptor was found to cross-react with antibodies against a human vitronectin receptor (aEv33). The receptor could be purified from monocyte extracts by using monoclonal antibodies (MAbs) against the av subunit of vitronectin receptor coupled to CNBr-Sepharose 4B, as well as with the adhesive tripeptide sequence arginine-glycine-aspartic acid (RGD) coupled to CNBr-Sepharose 4B. Surface-bound MAbs directed against aV143 were found to inhibit the attachment of M. avium-M. intraceflulare to monocyte-derived macrophages in an in vitro inhibition assay, while MAbs directed against CD14, CD18, a21 and platelet glycoprotein gpIIb/IHIa receptors did not inhibit this attachment. These observations suggest that (VO3 on the surface of human monocytes and monocyte-derived macrophages may function as a receptor for M. avium-M. intraceldulare. Identification of a receptor for M. avium-M. intracellulare on macrophages may offer new approaches to the prevention and control of M. avium-M. intracelulare infection at the cellular level. receptors involved have been identified (5). However, monocytes, macrophages, and stimulated polymorphonuclear cells (but not lymphocytes or unstimulated polymorphonuclear cells) have also been shown to bind M. avium-M. intracellulare in the absence of complement, serum, or serum proteins. This binding was shown to be mediated by a proteinaceous receptor on macrophages (8). Here we report that the integrin receptor CLV,3 on monocytes and monocytederived macrophages (MDM) which is also known as vitronectin receptor (20,28,31), binds to M. avium-M. intracellulare in the absence of complement. MATERIALS AND METHODSGrowth and labeling of M. avium-M. intracelulare. M. avium-M. intracellulare obtained from the American Type Culture Collection (ATCC 25291, Rockville, Md.) was cultured in Middlebrook 7H11 broth (Difco Laboratories, Detroit, Mich.) at 37°C in 5% CO2 for 7 to 14 days with vigorous agitation once a day. Bacteria were harvested by centrifuging the medium at 800 x g for 15 min. In order to label the bacteria, the pellet was resuspended in a 1-mg/ml solution of fluorescein isothiocyanate (FITC) (Sigma Chemical Co., St. Louis, Mo.) in 50 mM Na2CO3-100 mM NaCl (pH 9.2) and incubated in the dark for 30 min at room temperature. The suspension was then washed two times with phosphatebuffered saline (PBS) containing 1 mM CaCl2 and 1 mM MgCl2 (Dulbecco's PBS or DPBS) and resuspended in the same buffer. The final suspension was sonicated for 4 s,...

We examined nonopsonic binding of Mycobacterium avium-Mycobacterium intracellulare (MAI) by human leukocytes. Macrophages (M phi) avidly bound fluorescently labeled MAI in the absence of serum proteins. Binding appeared to be mediated by a lineage-specific, proteinaceous receptor on M phi, since (i) binding of labeled bacteria could be competitively inhibited by unlabeled MAI, (ii) treatment of M phi with trypsin ablated the ability of M phi to bind MAI, and (iii) the capacity to bind MAI was observed on monocytes, M phi, and stimulated polymorphonuclear cells but not on lymphocytes or unstimulated polymorphonuclear cells. The receptor for MAI appeared mobile in the plane of the membrane, since spreading of M phi on a carpet of immobilized, unlabeled MAI down modulated binding of labeled MAI added in suspension. The receptor required neither calcium nor magnesium for activity and appeared different from other known receptors for intracellular pathogens.

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Although routinely done, there has been no evaluation of the utility of performing routine cerebrospinal fluid (CSF) examination in patients with active coccidioidomycosis and high complement fixation (IgG) antibody titers or other risk factors for disseminated infection. In our review 100% of patients diagnosed with coccidioidal meningitis had at least one sign or symptom consistent with infection of the central nervous system, headache was present in 100% of those with meningitis, while no patients without signs/symptoms of CNS infection were found to have coccidioidal meningitis, irrespective of antibody titers or other risk factors. Thus routine lumbar puncture may be unnecessary for patients with coccidioidomycosis who lack suggestive clinical symptoms.