Levels of tumor necrosis factor alpha, gamma interferon, and interleukins 4, 6, and 10 as determined in mice infected with virulent or attenuated strains of Trypanosoma cruzi

Inoculation of BALB/c mice with the virulent Tulahuen (TUL) strain of T. cr uzi was shown to lead to progressive and eventually lethal infections, wher eas infection with an attenuated strain (TCC) resulted in a hardly noticeab le experimental disease producing no tissue damage. To determine whether di fferences in such infection outcome are associated with a particular patter n of cytokine response, a study was undertaken to investigate the serum lev els of TNF-alpha, IFN-gamma, IL-4, IL-6, and IL-10 by using an enzime-linke d immunosorbent assay. Mice from both infected groups were bled at 5, 9, 15 , 22, 30 and 48 days post-infection (pi), with the same interval being appl ied for obtention of serum samples in age-matched uninfected mice, a group that yielded negative results in all cases. Infection with the TUL strain o f T. cruzi was accompanied by a significant increase of TNF-alpha serum con centrations at day 5 pi, and detectable amounts of IFN-gamma by day 15 pi, which were exclusively recorded in this group. Serum IL-4 was mostly presen t in TCC mice with values at day 15 pi being statistically significant in r elation to TUL-infected mice. IL-10 was firstly detected at 3 weeks after i nfection, and showed higher levels in the TCC group, although comparisons w ith TUL-infected group were not significant. At our limit of detection, no samples were found to contain IL-6 serum concentrations. Infection with Vir ulent parasites seems to be associated with presence of Th1-type cytokines, whereas challenge with the attenuated TCC strain appears as being related to a Th2-type profile.