Immunomodulation of Intradermal Mammary Carcinoma Using Staphage Lysate in a Rat Model

Abstract

Staphage lysate (SPL), a preparation of Staphylococcus aureus obtained by bacteriophage lysis, is an interferon-inducer and stimulator of T and B lymphocytes. Does SPL, as an immunopotentiator, have an effect on the growth and metastases of an intradermal mammary carcinoma? To answer this question, a study using SPL in female Fischer rats injected with 7 × 10⁶ viable 13762 mammary tumor cells on the midback were used. Four groups were created with 10 animals in each group. Group I was the control group. They received no treatment. Group II received 0.3 ml of medium in which SPL was carried on alternate days. Group III received 0.3 ml SPL on alternate days. Group IV were sensitized with dead staphylococcal organisms prior to SPL treatment as in Group III. Tumor diameters were recorded on days 10, 13, 17, and 21, and autopsies were performed to determine the extent of metastases. Histologic examination and serum antibody measurements were performed

The mean tumor diameters on day 21 were: Group 1:4.1 ± 0.2 cm; Group II: 3.80 ± 0.19 cm; Group III: 3.04 ± 0.13 cm; and Group IV: 2.97 ± 0.14 cm. Rats receiving SPL treatment in Groups III and IV had significantly smaller tumors (P >. 001). The incidence of axillary lymph node involvement was: Group I:100%; Group II: 87.5%; Group III: 62.5%; and Group IV: 40%. Lung metastases were seen in all groups. Groups I and II had 100% incidence of grossly visible nodules, whereas Groups III and IV had 75% and 70% involvement. Gross findings were confirmed by microscopic examination. Antibodies to SPL were positive in 62.5% and 85% in Groups III and IV, respectively, whereas only 40% of the animals had positive antibodies in the controls

In conclusion, SPL has a significant inhibitory effect on the growth and axillary metastases of intradermal mammary carcinoma in our rat model