Balb/Cj male mice do not feminize after infection with larval Taenia crassiceps.

Balb/cJ mice fail to mount an immune response capable of clearing infection with larval Taenia crassiceps. Additionally, male Balb/cJ mice display a lag in larval growth of approximately 3 wk as compared to growth in female mice. It has been reported that male Balb/ cAnN mice generate a protective immune response early in infection, and become permissive to larval growth after they feminize (200-fold increase in serum estradiol and 90% decrease in serum testosterone). To determine if a different strain of Balb/c mice (Balb/cJ) also feminize, serum was collected from infected male mice for 16 wk and levels of 17-beta-estradiol and testosterone were measured via ELISA. In addition, the mounting responses of 12- and 16-wk infected male mice, as well as uninfected control mice, were determined after isolation with a female mouse. The results of these experiments show that male Balb/cJ mice do not feminize during infection with larval T. crassiceps. There was no significant change in serum levels of either 17-beta-estradiol or testosterone during the course of infection (> 16 wk). Moreover, there was no significant decrease in the number of times infected male mice mounted the female mouse as compared to uninfected controls. These results suggest that there may be variances between the substrains of Balb/c mice that lead to the phenotypic differences reported for male Balb/cJ and Balb/cAnN mice.

Uptake and secretion of host proteins by Taenia crassiceps metacestodes.

Although the presence of intact host proteins in the cyst fluid of cyclophyllidean metacestodes has been well documented, the underlying reason for protein uptake is poorly understood. To investigate this discrepancy, both the cyst fluid (CF) and excreted/secreted (E/S) proteins were collected in vitro from Taenia crassiceps metacestodes 16 wk postinfection in Balb/cJ female mice. The CF and E/S were subsequently immunoblotted using rabbit anti-mouse whole serum antibodies as a probe. The results show that whole host proteins were not only internalized by metacestodes but also secreted as well. The predominant secreted host protein was 66 kDa and was confirmed to be mouse serum albumin. The amount of secreted albumin decreased daily, whereas the concentration of albumin in the cyst fluid remained consistent. This suggests that the secretion of albumin is a coordinated function rather than a random event. It is probable that albumin cycling may be an evolved mechanism providing multiple benefits for the larvae, including osmoregulation and protection from innate immune responses.