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

Abstract

Inoculation of BALB/c mice with the virulent Tulahuen (TUL) strain of T. cruzi was shown to lead to progressive and eventually lethal infections, whereas infection with an attenuated strain (TCC) resulted in a hardly noticeable experimental disease producing no tissue damage. To determine whether differences in such infection outcome are associated with a particular pattern of cytokine response, a study was undertaken to investigate the serum levels of TNF-α, IFN-γ, IL-4, IL-6, and IL-10 by using an enzime-linked 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 applied for obtention of serum samples in age-matched uninfected mice, a group that yielded negative results in all cases. Infection with the TUL strain of T. cruzi was accompanied by a significant increase of TNF-α serum concentrations at day 5 pi, and detectable amounts of IFN-γ by day 15 pi, which were exclusively recorded in this group. Serum IL-4 was mostly present in TCC mice with values at day 15 pi being statistically significant in relation to TUL-infected mice. IL-10 was firstly detected at 3 weeks after infection, and showed higher levels in the TCC group, although comparisons with TUL-infected group were not significant. At our limit of detection, no samples were found to contain IL-6 serum concentrations. Infection with virulent 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.