Immunomodulatory effects in Litomosoides sigmodontis -infected Mastomys coucha

Abstract

The levels of parasite-specific IgG1 and IgG2 antibodies and mitogen-induced and parasite-specific proliferative T-cell responses were determined in Litomosoides sigmodontis-infected Mastomys coucha throughout an observation period of 400 days post infection (p.i.). These were compared with the respective reactions in animals that had been immunized with intrauterine stages/microfilariae of the parasite and in animals that had been challenged after immunization as determined at up to 60 days after challenge. IgG1 antibodies to adult antigen developed early and reached a plateau at 120 days p.i., whereas IgG2 antibodies were not found before day 60 p.i., increased with rising parasitemia, reached a plateau at 200 days p.i., and, in some animals, even became the predominant IgG subclass. Proliferative responses of spleen lymphocytes to concanavalin A (Con A) and lipopolysaccharides (LPS), but not Con-A-induced interleukin 2 (IL-2) production, were found to be suppressed in infected animals during patency as compared with uninfected controls. Spleen cells of infected animals showed a weak proliferative reaction to male antigen but were unresponsive to female and microfilarial antigen during prepatency and early patency. Subsequently, when microfilaremia decreased (200 days p.i.), continuously increasing responses to all antigens were observed. Immunized M. coucha developed specific IgG1 and IgG2 antibodies, and their spleen cells showed strong proliferative responses to the three L. sigmodontis antigens. Challenge infections down-regulated the proliferative responses of spleen cells to filarial antigens as early as during the prepatent phase of the challenge infection but supported existing IgG1 and IgG2 responses.

Cellular immune responses of filaria (Litomosoides sigmodontis) infected BALB/c mice detected on the level of cytokine transcription

“…However, the up-to-date results are controversial and disagree with several observations made in human infections. In particular, and in contrast to other L. sigmodontis host systems (19,20) and filarial infections in general (10±13), parasitaemic BALB/c mice show a clear antigen specific T cell proliferation (21,22) instead of T cell hyporesponsiveness. The disappearence of microfilariae from the blood [parasitaemia is generally low and short-termed in BALB/c mice (18,23)] is associated with a ceasing T cell reactivity (22).…”