ABSTRACT
Junin virus-induced encephalitis in suckling mouse is a delayed-type hypersensitivity reaction, whose immunopathologic nature has been proven by suppressing the thymus-dependent response. Cyclophosphamide (CY) given at day +6 post-infection (p.i.) has been shown to modulate infection, presumably by TDTH lymphocyte inactivation. To determine critical timing and i.p. drug dose, brain histology and survival were studied in 3-day-old Balb/c mice, inoculated i.c. with Junin virus. Optimal protection was achieved with a non-toxic, 50 mg/kg CY dose at day 6 p.i. (+6): no brain tissue damage was detected in animals killed at day +12, when the necropsied controls exhibited widespread lesions. Other timings (day +3, +4, +5) proved less effective. As regards alternative dosage at day +6, 30 mg was useless, and severe leptomeningitis was evident, whereas 40 mg significantly lowered mortality, and lesions were much milder and less constant. It seems that the 50 mg/kg CY dose must be administered at a critical time p.i. to inactivate sensitized TDTH lymphocytes and to reduce mortality and CNS pathology significantly.
Subject(s)
Cyclophosphamide/therapeutic use , Encephalitis/drug therapy , Hemorrhagic Fever, American/drug therapy , Animals , Animals, Newborn , Arenaviruses, New World/drug effects , Cyclophosphamide/administration & dosage , Disease Models, Animal , Drug Administration Schedule , Encephalitis/immunology , Encephalitis/pathology , Hemorrhagic Fever, American/immunology , Hemorrhagic Fever, American/pathology , Hypersensitivity, Delayed , Mice , Mice, Inbred BALB CABSTRACT
The immune response of the Buffalo/Sim rat to heterologous sheep red blood cells (SRBC) was studied here. The earliest time of response to 10(9) SRBC, the most suitable inoculation route and the behavior to challenge were determined. The intraperitoneal (ip) proved more effective than the subcutaneous (sc) route, since serum agglutinins became detectable in low titers in animals inoculated at 6-7 days of life by the former route and at 12 days by the latter. No splenic plaque-forming cells (PFC) were found in rats immunized ip at 2 days of age, and strong inhibition developed on challenge at day 14 post-inoculation (pi) (agglutinin titers at day 7 pi: 0.71 +/- 0.47 vs 4.6 +/- 0.51 in unprimed controls; PFC/10(7) cells at day 5: 122.21 +/- 36.17 vs 3,977.38 +/- 777.5 in unprimed controls). Serum agglutinin formation was also decreased, though to a lesser degree, when: a) animals were challenged at 30 or 60 days of age; b) both priming and challenge took place by sc route; or c) antigen dose was lowered to 10(7) or 10(5) SRBC. Mechanisms interpreting observed behavior are discussed.
Subject(s)
Antibody Formation , Erythrocyte Transfusion , Hemagglutination , Rats, Inbred BUF/immunology , Rats, Inbred Strains/immunology , Aging , Animals , Animals, Newborn , Hemagglutination Inhibition Tests , Kinetics , Rats , SheepABSTRACT
Otherwise resistant adult mice were rendered susceptible to intracerebral Junin virus (JV) infection only when a staggered cyclophosphamide (CY) schedule was used. Forty-five-day old Balb/c mice, intracerebrally JV-infected and immunosuppressed with four 50 mg/kg body weight CY doses at days -1, +1, +4, +6 (day 0: viral infection) developed a lethal disease (86.6 per cent mortality) with high CNS viral titers and brain lesions. Neutralizing antibodies were absent throughout, while immunofluorescent antibody levels were considerably diminished. The transfer of hyperimmune serum conferred partial though significant protection on CY-treated animals but no correlation was found between CNS viral titers and mortality since in both infected CY-treated and untreated mice similar brain viral content was found. This was also confirmed by immune spleen cell transfer at day 0 where the clearance achieved was unable to modify the time course of the disease. Feasible mechanisms explaining recovery from JV infection by means of the protective effect of antibodies and the cell-mediated clearance are discussed.
Subject(s)
Cyclophosphamide/pharmacology , Hemorrhagic Fever, American/immunology , Immunosuppression Therapy , Animals , Antibodies, Viral/analysis , Arenaviruses, New World/growth & development , Arenaviruses, New World/immunology , Brain/microbiology , Brain/pathology , Hemorrhagic Fever, American/microbiology , Hemorrhagic Fever, American/pathology , Immunity, Cellular , Immunization, Passive , Mice , Mice, Inbred BALB C , Neutralization TestsABSTRACT
The object of this paper was to determine the influence of cyclophosphamide immunosuppression on the mortality of 40-45 day old Balb/c mice infected intracerebrally with a pathogenic strain of Junin virus, using different administration schedules. Up to 200 mg/kg of cyclophosphamide were not toxic. Results show that, unlike in other experimental models, three or four 50 mg/kg cyclophosphamide doses given both before and after viral infection were required to break-down resistance to Junin virus (90-96.5% mortality vs. 8% in controls). Taking into account the effect of cyclophosphamide on the cell populations involved in the immune response, causes likely to lead to the greater susceptibility of the suppressed adult mouse to Junin virus are discussed.
Subject(s)
Cyclophosphamide/administration & dosage , Hemorrhagic Fever, American/immunology , Immunosuppressive Agents/administration & dosage , Animals , Arenaviruses, New World , Cyclophosphamide/toxicity , Drug Administration Schedule , Hemorrhagic Fever, American/mortality , Immunity, Innate/drug effects , Immunosuppressive Agents/toxicity , Mice , Mice, Inbred BALB CABSTRACT
Delayed-type-hypersensitivity (DTH) response "in vivo" is commonly evaluated by the footpad swelling test (FPST). High doses of Sheep Red Blood Cells (SRBC) are known to produce negligible DTH, while low doses lead to optimal sensitization. As expected FPST values obtained in Balb/c mice using 10(6) or 10(8) SRBC as sensitizing doses, showed that in 9 out of 10 batches from individual rams, the former dose resulted in higher values than the latter. However, only 3 out of the above 9 exhibited statistically significant differences between immunizing doses (Table 1). Therefore, in our hands, the accuracy of FPST is highly dependent on the SRBC source. We suggest the need of testing individual SRBC batches at both dilutions before use.
Subject(s)
Erythrocytes/immunology , Hypersensitivity, Delayed/immunology , Immunity, Cellular , Animals , Female , Hypersensitivity, Delayed/etiology , Immunization , Male , Mice , Mice, Inbred BALB C/immunology , Sheep/bloodABSTRACT
The object of this paper was to determine the influence of cyclophosphamide immunosuppression on the mortality of 40-45 day old Balb/c mice infected intracerebrally with a pathogenic strain of Junin virus, using different administration schedules. Up to 200 mg/kg of cyclophosphamide were not toxic. Results show that, unlike in other experimental models, three or four 50 mg/kg cyclophosphamide doses given both before and after viral infection were required to break-down resistance to Junin virus (90-96.5
in controls). Taking into account the effect of cyclophosphamide on the cell populations involved in the immune response, causes likely to lead to the greater susceptibility of the suppressed adult mouse to Junin virus are discussed.
ABSTRACT
Delayed-type-hypersensitivity (DTH) response [quot ]in vivo[quot ] is commonly evaluated by the footpad swelling test (FPST). High doses of Sheep Red Blood Cells (SRBC) are known to produce negligible DTH, while low doses lead to optimal sensitization. As expected FPST values obtained in Balb/c mice using 10(6) or 10(8) SRBC as sensitizing doses, showed that in 9 out of 10 batches from individual rams, the former dose resulted in higher values than the latter. However, only 3 out of the above 9 exhibited statistically significant differences between immunizing doses (Table 1). Therefore, in our hands, the accuracy of FPST is highly dependent on the SRBC source. We suggest the need of testing individual SRBC batches at both dilutions before use.
ABSTRACT
The object of this paper was to determine the influence of cyclophosphamide immunosuppression on the mortality of 40-45 day old Balb/c mice infected intracerebrally with a pathogenic strain of Junin virus, using different administration schedules. Up to 200 mg/kg of cyclophosphamide were not toxic. Results show that, unlike in other experimental models, three or four 50 mg/kg cyclophosphamide doses given both before and after viral infection were required to break-down resistance to Junin virus (90-96.5
mortality vs. 8
in controls). Taking into account the effect of cyclophosphamide on the cell populations involved in the immune response, causes likely to lead to the greater susceptibility of the suppressed adult mouse to Junin virus are discussed.
ABSTRACT
The CY-enhancing effect on DTH response of mice against SRBC was studied by administering to sensitized animals graded amounts of drug at various times during the immune response. The use of a staggered schedule for CY administration made it clear that this enhancing effect could be augmented even further by lowering the standard 200 mg/kg CY dose. Animals immunized on day 0 with 1 X 10(8) SRBC receiving 50 mg/kg doses on days -1, +1, and +4 showed higher DTH responses on day +7 than those similarly sensitized 1 day after the administration of 200 mg/kg body weight. In addition, we wanted to demonstrate that the TDTH effector cell is sensitive to CY in vivo, because a single 50 mg/kg dose inoculated on day +6 can lower by 50% an already established DTH response. This effect was not due to an effect of CY treatment on bone marrow-derived cells recruited to DTH responses; inhibition of DTH responses were transferred with spleen cells of CY-treated recipients. The action of CY is not dose-dependent; the administration on day +6 of a single dose of 200 mg/kg results in no further depression of the DTH reaction. We conclude that CY affects not only T supp cells, but also cell type(s) involved in the cell-mediated response of mice against SRBC, and that the DTH-enhancing effect of the drug is a blend of its action upon all these cells.
