Toxoplasma antigen isolated by affinity chromatography with monoclonal antibody protects mice against lethal infection with Toxoplasma gondii
Sharma, S.D.; Araujo, F.G.; Remington, J.S.
Journal of Immunology 133(6): 2818-2820
1984
ISSN/ISBN: 0022-1767 PMID: 6491277 Document Number: 221258
Groups of 10 mice were injected intraperitoneally with 0.25 ml of partially purified monoclonal antibody F3G3 24 h before and 3, 7 and 10 days after infection with different inocula of tachyzoites of the C56 strain of T. gondii. Control mice were given crude Ig preparations from NS-1 cell culture supernatant. 50% of controls infected with 1 x 105 or 1 x 104 tachyzoites had died by day 22. 90% of mice given monoclonal antibody and infected with 1 x 10superscript 3 or 1x 104 tachyzoites survived. In a 2nd experiment mice were immunized with 3 weekly injections of 50 micro g of affinity-purified F3G3 antigen alone or mixed with Freunds' incomplete adjuvant (FIA). The mice were challenged one week after the last injection, with 5 x 105 tachyzoites intraperitoneally. By day 90, 60% of controls were dead. 29% of mice immunized with antigen alone died by day 15. None of the mice given antigen with FIA died over the 3 month peroid. Antigen given with FIA completely protected against challenge with 5 x 106 tachyzoites. Sera of mice immunized with FsG3 antigen (with FIA) contained both agglutinating and complement-fixing antibodies. The lymphocyte transformation response was greater in immunized mice than in controls. "Our results demonstrate that the monoclonal antibody F3G3 (IgG2 subclass), which reacts in an immunofluorescence test with formalin-fixed but not with live tachyzoites, does not fix complement, and reacts with cytoplasmic but not cell surface components of the organism, protects mice against a lethal challenge with Toxoplasma gondii. Mice injected with the antigen recognized by the monoclonal antibody F3G3 were also protected against death due to challenge with live Toxoplasma.".