Plasmodium-host interactions directly influence the threshold of memory CD8 T cells required for protective immunity.

Plasmodium infections are responsible for millions of cases of malaria and ∼1 million deaths annually. Recently, we showed that sterile protection (95%) in BALB/c mice required Plasmodium berghei circumsporozoite protein (CS(252-260))-specific memory CD8 T cells exceeding a threshold of 1% of all PBLs. Importantly, it is not known if Plasmodium species affect the threshold of CS-specific memory CD8 T cells required for protection. Furthermore, C57BL/6 mice immunized with radiation-attenuated parasites are more difficult to protect against Plasmodium sporozoite challenge than similarly immunized BALB/c mice; however, it is not known whether this is the result of different CD8 T cell specificity, functional attributes of CD8 T cells, or mouse strain-specific factors expressed in nonhematopoietic cells. In this article, we show that more CS-specific memory CD8 T cells are required for protection against P. yoelii sporozoite challenge than for protection against P. berghei sporozoite challenge. Furthermore, P. berghei CS(252)-specific CD8 T cells exhibit reduced protection against P. berghei sporozoite challenge in the context of C57BL/6 and C57BL/10 non-MHC-linked genes in CB6F1 and B10.D2 mice, respectively. Generation and immunization of reciprocal chimeric mice between BALB/c and B10.D2 strains revealed that B10 background factors expressed by nonhematopoietic cells increased the threshold required for protection through a CD8 T cell-extrinsic mechanism. Finally, reduced CS-specific memory CD8 T cell protection in P. yoelii-infected BALB/c or P. berghei-infected B10.D2 mice correlated with increased rates of Plasmodium amplification in the liver. Thus, both Plasmodium species and strain-specific background genes in nonhematopoietic cells determine the threshold of memory CD8 T cells required for protection.

Helminth parasites of conventionally maintained laboratory mice - II. Inbred strains with an adaptation of the anal swab technique

Worm burdens recovered from inbred mice strains, namely C57B1/6, C57B1/10, CBA, BALB/c, DBA/2 and C3H/He, conventionnally maintained in two institutional animal houses in the State of Rio de Janeiro, RJ, Brazil, were analysed and compared, regarding their prevalences and mean intensities. Three parasite species were observed: the nematodes Aspiculuris tetraptera, Syphacia obvelata and the cestode Vampirolepis nana. A modification of the anal swab technique is also proposed for the first time as an auxiliary tool for the detection of oxyurid eggs in mice.

Helminth parasites of conventionally mantained laboratory mice

The spectrum of intestinal parasites present in the SwissWebster, C57B1/6 and DBA/2 mice strains from different animal houses was identified and prevalences compared. Three parasites were observed during the course ofthis study, namely the cestode. Vampirolepis nana (Siebold, 1852) Spasskii, 1954(=Hymenolepis nana) and the nematodes Aspiculuris tetraptera (Nitzsch, 1821) Schulz, 1924 and Syphacia obvelata (Rudolphi, 1802) Seurat, 1916. The scope of thisinvestigation has been widened to also include morphometric data on the parasites, to further simplify their identification, since the presence of helminths in laboratory animals is regarded as a restricting factor for the proper attainmentof experimental protocols

Helminth parasites of conventionally maintained laboratory mice.

The spectrum of intestinal parasites present in the Swiss Webster, C57B1/6 and DBA/2 mice strains from different animal houses was identified and prevalences compared. Three parasites were observed during the course of this study, namely the cestode Vampirolepis nana (Siebold, 1852) Spasskii, 1954 (= Hymenolepis nana) and the nematodes Aspiculuris tetraptera (Nitzsch, 1821) Schultz, 1924 and Syphacia obvelata (Rudolphi, 1802) Seurat, 1916. The scope of this investigation has been widened to also include morphometric data on the parasites, to further simplify their identification, since the presence of helminths in laboratory animals is regarded as a restricting factor for the proper attainment of experimental protocols.

Host specificity of Giardia muris isolates from mouse and golden hamster.

One isolate of Giardia muris from a naturally infected laboratory mouse (Mus musculus) and one from a naturally infected golden hamster (Mesocricetus auratus) were passaged three times by the inoculation of ten cysts (the minimal infectious dose) into barrier-maintained homologous hosts. Both of the resultant isolates were tested for infectivity by intragastric inoculation of 3-5 x 10(5) cysts into 40 mice (2 inbred strains), 40 rats (2 inbred strains), and 19 golden hamsters (1 outbred strain). Rats were not susceptible to infection with either isolate. Mice and golden hamsters did develop infections following their inoculation with the heterologous isolates. The mean intensity of heterologous infections with the hamster isolates was significantly lower than that of homologous infections. The mouse isolate induced a higher mean intensity of infection in hamsters as compared with homologous recipients. The mean intensity of infections induced by both isolates was greater in male hamsters than in females.

Host specificity of cloned Spironucleus muris in laboratory rodents.

With three clones of Spironucleus muris (S. muris)--established from a mouse, hamster, and rat--homologous and heterologous host species were experimentally infected. Each host was susceptible to the clone originating from the homologous donor. In addition, both mice and hamsters were susceptible to the reciprocal heterologous clones. In contrast, infections of the rat with both heterologous clones were very poor, i.e. quantitatively low and ephemeral. It was not possible to infect hamsters and mice, not even athymic, with S. muris from the rat. This suggests a strain heterogeneity within the genus S. muris. In general, the genetic background of the host influenced the infection, the sex of the host did not.

Strain-dependent differences in susceptibility of mice to experimental Angiostrongylus costaricensis infection.

Experimental Angiostrongylus costaricensis infection was carried out in inbred strains of mice (C57BL/6 BALB/c, DBA/2 and C3H/He). All strains became infected with this parasite. Marked differences in mortality and in worm burden were found among inbred strains of mice tested. A significant reduction was shown in worm length from mice compared to that from cotton rats.

Sex differences and cross-immunity in DBA/2 mice infected with L. mexicana and L. major.

Female DBA/2 mice were found to be highly resistant to Leishmania mexicana and rarely developed lesions even when inoculated subcutaneously with high numbers (5 x 10(6] of amastigotes. Male DBA/2 mice, on the other hand, were much more susceptible to this parasite and often developed non-healing lesions even when inoculated subcutaneously with comparatively few (5 X 10(4] amastigotes. Conversely, although both male and female DBA/2 mice developed ulcerating lesions when inoculated subcutaneously with L. major amastigotes, lesions invariably healed in males but did not heal in females. Male DBA/2 mice recovered from L. major infection subsequently were found to be resistant to subcutaneous challenge with L. mexicana. Conversely female DBA/2 mice that had failed to develop lesions when infected with L. mexicana developed lesions which healed following subcutaneous challenge with L. major. Thus there is bilateral cross-immunity between L. mexicana and L. major in DBA/2 mice which overrides differences in sex-determined susceptibility to both organisms.

The use of host strain variation to assess the significance of mucosal mast cells in the spontaneous cure response of mice to the nematode Trichuris muris.

A proportion of DBA/2 mice do not reject the large intestinal nematode parasite Trichuris muris. In this strain and the early rejecting NIH and the late rejecting CBA/Ca strains the kinetics of the mast cell accumulation in a primary infection were similar with peak mast cell numbers being recorded on day 20 post-infection. Comparisons between rejector and non-rejector DBA/2 mice showed no differences in the mast cell accumulation. There was no rise in mast cell numbers in response to a secondary infection, in either the NIH or CBA/Ca strains, for at least 3 days after the infection had been expelled. It is suggested that mucosal mast cell accumulation is not induced by a simple response to parasite factors, that the cells are not directly involved in the expulsion of T. muris and that any role they play in the spontaneous cure response is subject to more complex control.

[Sensitivity of inbred mice to toxoplasma of virulent and nonvirulent strains according to parasitological study data]. / Chuvstvitel'nost' lineinykh myshei k toksoplazmam virulentnogo i malovirulentnogo shtammov po dannym parazitologicheskogo issledovaniia

Genetic peculiarities of mice were studied in regards to their susceptibility to toxoplasms. Differences in susceptibility to little virulent toxoplasms in mice of 9 different lines are shown, which manifest at all stages of the infection process or only at acute or chronic stages. The susceptibility of 6 lines of mice to virulent toxoplasms was found to be equally high.