MYCOBACTERIUM-AVIUM COMPLEX INFECTION IN MICE - LACK OF EXACERBATION AFTER LP-BM5 MURINE LEUKEMIA-VIRUS INFECTION

The murine leukemia virus LP-BM5 has been used to reproduce the model of murine AIDS in order to evaluate the course of infection with the M O-1 strain of Mycobacterium avium complex (MAC). LP-BM5 was inoculated in C57BL/6 mice by intravenous (i.v.) injection either 8 weeks before an i,v, challenge with 10(3) or 10(6) CFU of MAC (coinfection 1) or 1 0 days after an i.v. challenge with 10(3) CFU of MAC (coinfection 2). During coinfection 2 experiments, the phenotypic alterations in blood lymphocyte subsets were analyzed. During coinfection 1, LP-BM5 infecti on tended to decrease the mycobacterial growth, with the difference re aching statistical significance for the lower inoculum (10(3) CFU of M AC) (P < 0.001). During coinfection 2, LP-BM5 did not exacerbate MAC i nfection, except in the spleen, at day 90 after LP-BM5 challenge (P < 0.001), LP-BM5 infection and the LP-BM5-MAC coinfection increased the numbers of activated CD4(+) lymphocytes (CD4(+) Ly6AE(+)) (P < 0.001), activated CD8(+) lymphocytes (CD8(+) Ly6AE(+)) (P < 0.001), and activ ated B lymphocytes (Ly5(+) Ly6AE(+)) (P < 0.001). This activation of T lymphocytes could explain the lack of exacerbation of MAC infection a nd even the trend to a lower level of MAC infection. Thus, this model of retroviral infection of mice does not seem to be a reliable model o f immunodepression for the study of MAC infection and its treatments.