Immune responses of bovine leukemia virus-infected guinea pigs to betulinic acid amide administration

Introduction. Betulinic acid is a naturally occurring compound with significant potential for the development of anti-leukemia therapeutics. It demonstrates antiviral activity alongside a marked immunomodulatory effect, properties that can be potentiated through the introduction of a novel pharmacophore group into its molecular framework.

Objective. The study was aimed at evaluating the therapeutic antiviral activity of betulinic acid amide, as well as the immune response of bovine leukemia virus (BLV)-infected guinea pigs to its administration.

Materials and methods. Fifteen Agouti guinea pigs, 4–5 months of age, were used for the study. Ten animals received a single intraperitoneal inoculation of lymphocyte suspension from leukemic cows; the remaining five animals served as intact controls. On day 21 after infection, five of the infected animals were subcutaneously injected with betulinic acid amide at a dose of 40 μg/kg (group 1), whereas the other five infected animals were left untreated (group 2). Blood samples were collected prior to the treatment, and then at 14 and 28 days after treatment to assess cellular and humoral immune responses and for molecular biological studies.

Results. The study showed that the immune response of the guinea pigs to inoculation with the virus-containing suspension was characterized by a significant increase in lymphoid cell counts by day 49 of the experiment. This increase was caused by a 1.85-fold boost in B-lymphocyte and a 2.7-fold boost in cytotoxic T-lymphocyte proliferation. Administration of betulinic acid amide on day 21 post-infection resulted in suppression of B-cell and cytotoxic T-lymphocyte proliferation, 2.1-fold increase in myeloperoxidase and cationic protein activity in neutrophils, and stimulation of antibody production. However, the experimental drug failed to confer protection against the infection: specific fluorescence was detected with direct immunofluorescence assay and proviral DNA was detected in blood samples from 100% and 60% of the animals, respectively.

Conclusion. Administration of the betulinic acid derivative prevents immune dysregulation in BLV-infected guinea pigs as evidenced by normalized lymphoid cell counts and enhanced neutrophil functional and metabolic activity. These findings indicate that betulinic acid amide is a promising veterinary candidate for preventing the development of clinical and hematological leukosis in infected animals.

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