The production of three cytokines, interferon gamma (IFN-y), interleukin 10 (1L-10) and interleukin 12 (IL-12), was measured after intraperitoneal infection of immunocompetent Balb/c mice and immunodeficient SCID mice with the microsporidian, Encephalitozoon cuniculi Levaditi, Nicolau ct Schoen, 1923. High levels of IFN-y were detected in ex vivo cultures of peritoneal exudate cells (PEC) of Balb/c mice, a lower, but earlier IFN-y response was observed in PEC from SCID mice. The early 1L-10 response was detected in ex vivo cultures of splenocytes from Balb/c but not from SCID mice, explaining a delay in the IFN-y response in Balb/c mice. IL-12 was detected in PEC cultures from SCID mice, indicating an alternative pathway of IFN-y production by NK. cells stimulated by IL-12 derived from macrophages.
Saliva-activated transmission (SAT) of Borrelia burgdorferi sensu stricto was demonstrated using real-time PCR and salivary gland extract (SGE) from partially fed Ixodes ricinus ticks. C3H/HeN mice were injected intradermally with 1.5 × 103 spirochetes mixed with 40 µg of SGE per mouse. The control group was inoculated with the same dose of spirochetes without SGE. The accelerating effect of SGE on spirochete proliferation was demonstrated on day 1 post infection, when a 4.2-fold increase in spirochetes was found in the skin and a 10-fold increase in the blood, compared with control mice. The data represent the first direct evidence of a SAT effect of I. ricinus SGE on infection with the Lyme disease agent B. burgdorferi.
Previous studies have demonstrated that both tick saliva and Borrelia burgdorferi sensu lato antigens modulate the cytokine response of the host. In this paper, the effect of salivary gland extract (SGE) from Ixodes ricinus (L., 1758) ticks on cytokine production by primary cultures of mouse epidermal cells stimulated with Borrelia afzelii Canica, Nato, du Merle, Mazie, Baranton et Postic, 1993 spirochetes was analysed. Epidermal cells were derived from C3H/HeN mice, susceptible to Lyme disease, and BALB/c mice, which are resistant. In cultures from C3H/HeN mice, SGE down regulated production of tumour necrosis factor alpha (TNF-α) and up regulated Th2 cytokine, interleukin 4 (IL-4). Cultures from BALB/c mice produced higher basal levels of monitored cytokines, but their production was affected by SGE a different way. While Th2 cytokines IL-6 and IL-10 were down regulated, the effect on TNF-α and IL-4 was ambiguous. These results indicate that the effect of tick saliva on the epidermal cells of Lyme disease-susceptible C3H/HeN mice mirrors its effect on other cells of the immune system.
Experimental activation of peritoneal macrophages by interferon gamma (IFN-γ) resulted in the inhibition of Encephalitozoon cuniculi replication. However, E. cuniculi could replicate either in a non-activated cell line of murine macrophages PMJ2-R or in IFN-γ-activated PMJ2-R cells. Moreover, activation with IFN-γ led to faster replication of E. cuniculi in these cells. Opsonisation of E. cuniculi spores with anti-E. cuniculi polyclonal antibody did not affect E. cuniculi replication in both, non-activated and activated murine macrophages. In contrast, opsonisation of E. cuniculi spores caused the most effective replication of E. cuniculi in activated PMJ2-R cells. However, production of nitric oxide by these cells was significantly more intensive than that in non-activated, infected cells, where the parasite replicated to a much lesser extent. Our results support the hypothesis that E. cuniculi uses phagocytosis for the infection of host cells. They also indicate that the mechanism by which spores of E. cuniculi are killed by macrophages is not dependent on nitric oxide and they reveal that PMJ2-R cells cannot substitute peritoneal murine macrophages in immunological studies on E. cuniculi.
An experimental infection with the microsporidian Encephalitozoon cuniculi Levaditi, Nicolau et Schoen, 1923 was studied using a model of immunocompetent BALB/c mice and immunodeficient SCID mice. The course of infection after intraperitoneal inoculation of E. cuniculi spores was evaluated using the presence of spores in peritoneal macrophages as a criterion. First significant decrease in the proportion of infected cells was recorded on day 9 post infection (p.i.) in BALB/c mice. From day 14 p.i. no spores were observed in macrophages from BALB/c mice, while the number of infected macrophages from SCID mice increased until the death of the mice. The natural killer (NK) cell activity of mouse splenocytes was compared with the production of interferon gamma (IFN-γ) by these cells. While in BALB/c mice NK activity peaked on days 9 and 14 p.i., in SCID mice the marked increase of NK activity was recorded close before death of mice, on day 21 p.i. in correlation with the production of IFN-γ. Production of specific antibodies was demonstrated from day 9 p.i. in sera from BALB/c mice. It is concluded that intraperitoneal infection of SCID mice with spores of E. cuniculi results in the marked increase in the number of peritoneal exudate cells and in the percentage of infected cells close before death of mice. Neither high activity of NK cells nor increased production of IFN-γ are sufficient for the recovery of SCID mice from an E. cuniculi infection.
An interference between a thermosensitive (ts) mutant and the wild-type (wt) of tick-borne encephalitis (TBE) virus in Ixodes ricinus L, and Rhipicephalus appendicuiatus (Neumann) ticks is reported. /. ricinus females were dually infected by a parenteral inoculation of ts and wt strains at 10-day interval. Interference was demonstrated by the lowered ability of wt virus to replicate in ticks previously infected by ts virus. The wt virus was demonstrated in only 30% of the ticks; the average virus titre was lowered by 2.1 log|0 compared with the control group, which was infected with the wt virus only. The oral infection of R. appendicuiatus ticks with the same viruses also revealed an interference with the growth of the superinfecting wt virus. While in the control group all the ticks became infected, in the dually infected group the wt virus was found in only 50% of the ticks. However, when the ticks were infected orally with is virus and superinfected parenterally with the wt virus, no interference was observed. In a R. appendicuiatus-derived cell line persistently infected with the ts virus (100% of the cells), a partial inhibition of the growth of the superinfecting wt virus was observed. The ts virus retained its thermosensitive phenotype throughout the persistent infection of both the ticks and the tick cell line.