Intramammary immunization with live-attenuated Staphylococcus aureus: microbiological and immunological studies in a mouse mastitis model

Abstract

Mammary infection was induced in lactating mice by intramammary injection of Staphylococcus aureus. Histopathological analysis revealed infiltration and lesions of varying magnitude that were still apparent 21 days after the challenge. Concomitantly, viable S. aureus was recovered from infected mammary glands. Mice were immunized by the intramammary route with 5 x 10(6) colony forming units of a temperature-sensitive mutant of S. aureus and subsequently received a boosting injection seven days later. On day 14 mice were challenged by the intramammary route with the wild-type strain. Intramammary immunization induced a significant increase in milk IgA (P < 0.05), serum IgG (P < 0.05) and serum IgA (P < 0.05) on the day of the challenge, when compared with non-immunized mice. Immunization decreased significantly (P < 0.01) the number of S. aureus colony forming units recovered 96 h after intramammary challenge. In conclusion, the feasibility of immunizing locally with temperature-sensitive S. aureus to induce immunity in the mouse mammary gland was demonstrated. The mouse model of mastitis is proposed as a useful system for screening temperature-sensitive S. aureus strains to be utilized in the development of a vaccine.

Induction of Cell-Mediated Immunity toStaphylococcus aureusin the Mouse Mammary Gland by Local Immunization with a Live Attenuated Mutant

“…Production of IFN-␥, a key indicator of the cell-mediated immune response induced by immunization, was not strain dependent, since it was found after stimulation with not only strain 8325-4 but also a S. aureus strain obtained from a cow with mastitis. Activated B lymphocytes were also detected in mammary lymph nodes from immunized mice, a finding which agreed with our previous results (6,9). The number of mononuclear cells in mammary lymph nodes from both immunized and control mice significantly increased after Ima challenge with wt-S. aureus, but only lymphocytes from immunized mice were able to produce IFN-␥ in response to S. aureus infection.…”

“…Mice received a second inoculation 7 days later (at the day of parturition). In the in vivo experiments, mice were challenged by the Ima route with 5 ϫ 10 5 CFU of wt-S. aureus as described previously (6,9). In experiments designed to test ␥␦ T-cell expansion, positive control cells were obtained from mice inoculated by the Ima route with 5 ϫ 10 5 CFU of viable BCG (13).…”

“…Using a mouse model of infection, we have previously demonstrated the feasibility of inducing mammary gland specific humoral immunity against S. aureus by local but not systemic immunization with a live attenuated (la) strain (6,9). The present study was aimed at evaluating whether Ima immunization with la-S. aureus can also induce cell-mediated immune responses to the pathogen within the mammary gland.…”

Attenuation and Persistence of and Ability To Induce Protective Immunity to a Staphylococcus aureus aroA Mutant in Mice

“…Both the S. aureus parental strain and the FB306 aroA mutant were investigated for their abilities to colonize the lungs, spleens, and mammary glands of mice. Previous results from our laboratory were considered to choose the different times postchallenge (21,23). Groups of mice were infected i.p.…”

“…route, the lungs were removed at different times (3 and 5 h) and homogenized. For ima inoculation, six female Swiss mice received 0.05 ml of the bacterial suspension in PSS (2 ϫ 10 5 CFU/gland) into the left fourth (L4) and right fourth (R4) mammary glands as described previously (10,21). After 24 h and 96 h, the L4 and R4 glands were removed and homogenized.…”