Abstracts (complete list) - Wissenschaft Online

Stefan Wiehr, Thomas Herrmann
Milk-derived immune cells may serve as Trojan Horses in
Toxoplasma gondii transmission
Beside vertical transmission of T. gondii from acutely infected mothers in utero,
transmission of T. gondii via the maternal milk has also been reported. To further
analyze the lactogenic route of infection our study focused on parameters of humoral
and cellular immune responses in congenitally versus milk infected rats. F344 rats were
inoculated i.p. with 1x10e6 NTE or Prugneaud beta-gal tachyzoites at day 14 of
gestation and blood and milk were taken every second day after delivery. Cells were
isolated from the milk by density gradient centrifugation and analyzed by FACS and
confocal microscopy. By using a human foreskin fibroblasts bioassay T. gondii positive
milk samples could be detected until day 22 p.i.
T. gondii tachyzoites could be observed inside cells whereas the non-cellular milk
fraction was predominantly T. gondii negative, suggesting that T. gondii infected cells
might serve as a vehicle for oral transmission to neonates. Strikingly, a strong antibody
response was found in milk of infected rats. Moreover, the cellular fraction of the milk of
infected rats showed a highly elevated number of CD45 positive cells consisting of all
major alpha-beta and gamma-delta T cell and of granulocytes. To investigate whether
the presence of tachyzoites in the milk correlated with transmission of T. gondii to
uninfected offspring, we performed criss-cross experiments. Two months after birth,
one out of 24 offspring fed with T. gondii positive milk showed a sustained increase of
T. gondii antigen specific IgG2b as well as antigen specific proliferation with secretion of
IFN-gamma by mesenteric lymph node cells and splenocytes. Six out of 44 offspring by
which the parasite was transmitted in utero and 6 of 41 born from infected mothers
exhibited the same type of immune response.
These results indicate that T. gondii infected cells found in maternal milk may serve as a
vehicle for parasite transmission and that both diaplacental and lactogenic infection
induces a TH1 dominated immune response in the offspring of infected mothers.
herrmann-t@vim.uni-wuerzburg.de