J. Med. Microbiol. - Vol. 40 (1994), 129-133 0 1994 The Pathological Society of Great Britain and Ireland Induction of IL-ID, IL-6, TNF-a, GM-CSF and G-CSF in human macrophages by smooth transparent and smooth opaque colonial variants of Mycobacterium aviurn L. FATTORINI, Y. XIAO, B. LI, C. SANTORO, F. IPPOLITI" and G. OREFlClf Laboratory of Bacteriology and Medical Mycology, Jstituto Superiore di Sanita, Wale Regina Elena 299, 00161 Rome and * Laboratory of Immunology, Department of Experimental Medicine, University of Rome "La Sapienza ", Rome, Italy Summary. Both smooth transparent (SmT) and smooth domed-opaque (SmD) colonial variants were obtained from a strain of Mycobacterium avium isolated from a patient with AIDS. The two variants showed similar biochemical characteristics but SmT bacteria proliferated better than SmD bacteria inside human macrophages and were much less capable than the SmD variant of inducing the release of IL-lp, IL-6, TNF-a, GM-CSF and G-CSF, after incubation for either 3 or 6 days. As cytokines are important extracellular signals for immune cells, the lack of induction observed in SmT-infected macrophages may be one of the pathogenic mechanisms of M. aviurn. Introduction Mycobacterium avium-intracellulare complex (MAC) is a large group of acid-fast bacilli of en- vironmental origin that yield three colonial variants when grown in agar: smooth transparent (SmT), smooth domed-opaque (SmD) and rough (Rg) variants.'v2 The SmT variant was found to be more resistant to drugs and c h e m i ~ a l s ~ ~ ~ and more patho- genic for chickens and mice than the SmD ~ a r i a n t , ~ ' ~ suggesting some relationship between colonial mor- phology with virulence. After transfer of the bacteria from host tissues to in-vitro culture conditions, tran- sition from the SmT to the SmD colony type was observed.' MAC strains with all three types of colonial variants could be isolated from human immuno- deficiency virus (H1V)-negative patients with chronic lung infections, with the SmD and SmT forms pre- dominating.6In contrast, blood isolates of MAC from patients with AIDS gave only SmT colonies on primary cultures ;7 in these patients, MAC dissemin- ated throughout the body within macrophages with an adverse effect on survival.8-'o The mechanisms of MAC pathogenicity are poorly understood despite the abnormalities known to be induced in macrophage functions or T cell- macrophage intera~ti0ns.ll-l~ It has been shown15-17 that MAC infection of human monocytes or macro- phages was able to induce the release of IL- lp, IL- 1 a, IL-6, GM-CSF and TNF-a. However, these studies were done by infecting cells ~~~ Received 27 May 1993; revised version accepted 23 July 1993. t Correspondence should be sent to Dr G. Orefici. with bacteria harvested from Lowenstein-Jensen agar slants or Middlebrook 7H9 broth, which are known to give a selective advantage to the SmD ~ a r i a n t . ~ Michelini-Norris et a1.18 reported that SmT and SmD variants induced a differential release of IL- 1 a, IL- lp and IL-6 from nornial human monocytes and sug- gested that disturbances of cytokine production could contribute to MAC survival within cells, and then establish the infection. The aim of this study was to examine the production of cytokines from SmD- or SmT-infected monocyte- derived human macrophages, for a more complete evaluation of the release of these immunoregulatory proteins following MAC stimulation. Materials and methods Bacteria Mycobacterium aviurn strain 485 (serovar 21), was isolated from the blood of a patient with AIDS. It was identified by the Gen Probe Rapid Diagnostic System (Gen Probe, San Diego, CA, USA) and serotyped by Dr A. Tsang at the National Jewish Center for Immunology and Respiratory Medicine of Denver, CO, USA.lg Isolation of colonial variants The bacteria were grown on Middlebrook 7H10 Agar (Difco) for 1-2 weeks at 37°C in a humidified atmosphere of air with CO, 5 %. In the first cultures, the plates contained essentially SmT colonies with 129