The development of immune responses in Balb/c mice following inoculation with attenuated or virulent Neospora caninum tachyzoites.
Balb/c mice were inoculated intraperitoneally (i.p.) with either 5 x 10(6) live virulent (group 1) or 5 x 10(6) live attenuated (group 2) tachyzoites, or Vero cells (group 3). Animals were killed at 0, 14, 28 and 42 days post-inoculation (p.i.), with the remaining mice receiving a lethal challenge on day 48 p.i. Serum, spleen and brain samples were collected post-mortem to examine humoral and cell-mediated immune responses as well as pathological lesions and to quantify parasite loads. On day 14 p.i. group 2 (attenuated) demonstrated statistically significant (P < 0.001) lower levels of mean morbidity and weight loss, while also showing significantly (P = 0.01) higher levels of splenocyte proliferation and IFN-gamma production (P = 0.003), compared to group 1 (virulent). Histology of brain samples showed milder lesions and a lower incidence of positive immunohistochemistry, demonstrating tachyzoites and tissue cysts, and statistically significant (P = 0.03) lower mean burdens of parasite DNA in group 2 (attenuated) compared to group 1 (virulent). All mice in group 2 were protected following challenge on day 48 p.i. whereas naïve control mice succumbed to the challenge. No mice from group 1 (virulent) survived beyond day 24 p.i. so they were not included in the challenge.
Bartley
P M
PM
Moredun Research Institute, Pentlands Science Park, Bush Loan, Penicuik, UK. paul.bartley@moredun.ac.uk
Wright
S E
SE
Maley
S W
SW
Buxton
D
D
Nath
M
M
Innes
E A
EA
D000818:Animals; D000913:Antibodies, Protozoan / Q000097:blood; D001835:Body Weight; D001921:Brain / Q000276:immunology / Q000469:parasitology / Q000473:pathology; D003048:Coccidiosis / Q000276:immunology* / Q000469:parasitology / Q000517:prevention & control*; D005260:Female; D007371:Interferon-gamma / Q000378:metabolism; D007963:Leukocytes, Mononuclear / Q000276:immunology; D051379:Mice; D008807:Mice, Inbred BALB C; D018688:Neospora / Q000276:immunology*; D044967:Serum / Q000276:immunology / Q000469:parasitology; D012720:Severity of Illness Index; D013154:Spleen / Q000276:immunology / Q000469:parasitology; D016019:Survival Analysis
D000913:Antibodies, Protozoan; D007371:Interferon-gamma