Fj. Sangari et al., Mycobacterium avium infection of epithelial cells results in inhibition ordelay in the release of interleukin-8 and RANTES, INFEC IMMUN, 67(10), 1999, pp. 5069-5075
Mycobacterium avium is an opportunistic pathogen in AIDS patients, who acqu
ire the infection mainly through the gastrointestinal tract. Previous studi
es in vitro have shown that M, avium invades epithelial cells of both intes
tinal and laryngeal origin. In addition, M, avium enters the intestinal muc
osa of healthy mice. Because M. avium invasion of the intestinal mucosa in
vivo initially is not accompanied by significant influx of inflammatory cel
ls, we sought to determine whether M. avium would trigger chemokine release
upon entry into epithelial cells by using HT-29 intestinal and HEp-2 laryn
geal epithelial cell lines, Chemokine synthesis was measured both by the pr
esence of specific mRNA and protein secretion in the cell culture supernata
nt as determined by enzyme-linked immunosorbent assay. Infection of HT-29 i
ntestinal cells with M. avium did not induce the release of interleukin-8 (
IL-8) or RANTES for up to 7 days postinfection. However, infection of HEp-2
cells resulted in the release of IL-8 and RANTES at 72 h, Similar findings
were observed,vith other AIDS M. avium isolates belonging to different ser
ovars, Secretion of IL-8 by HEp-2 cells was dependent upon bacterial uptake
. In addition, prior infection with M. avium suppressed IL-8 production by
HT-29 cells infected with Salmonella typhimurium, Our results suggest that
M. avium infection of epithelial cells is associated with a delay in IL-8 a
nd RANTES production which, in the case of HT-29, is prolonged up to 1 week
, These findings may explain the weak inflammatory response after intestina
l mucosa invasion in mice and are probably related with the ability of the
bacterium to evade the host's immune response.