Viral contamination of a subline of Toxoplasma gondii RH

From bench to cageside: Risk assessment for rodent pathogen contamination of cells and biologics

Many newly developed animal models involve the transfer of cells, serum, or other tissue-derived products into live rodents. These biologics can serve as repositories for adventitious rodent pathogens that, when used in animal studies, can alter research outcomes and result in endemic outbreaks. This review includes a description of some of the biologics that have inadvertently introduced infectious agents into in vivo studies and/or resulted in endemic outbreaks. I also discuss the points of potential exposure of specific biologics to adventitious rodent pathogens as well as the importance of acquiring a complete developmental and testing history of each biologic introduced into a barrier facility. There are descriptions of specific cases of mycoplasma and lactate dehydrogenase–elevating virus (LDHV), two of the most common organisms that contaminate cells and cell byproducts. The information in this article should help investigators and animal resource program personnel to perform an appropriate risk assessment of biologics before their use in in vivo studies that involve rodents.

Neurological and behavioral abnormalities, ventricular dilatation, altered cellular functions, inflammation, and neuronal injury in brains of mice due to common, persistent, parasitic infection

BACKGROUND

Worldwide, approximately two billion people are chronically infected with Toxoplasma gondii with largely unknown consequences.

METHODS

To better understand long-term effects and pathogenesis of this common, persistent brain infection, mice were infected at a time in human years equivalent to early to mid adulthood and studied 5-12 months later. Appearance, behavior, neurologic function and brain MRIs were studied. Additional analyses of pathogenesis included: correlation of brain weight and neurologic findings; histopathology focusing on brain regions; full genome microarrays; immunohistochemistry characterizing inflammatory cells; determination of presence of tachyzoites and bradyzoites; electron microscopy; and study of markers of inflammation in serum. Histopathology in genetically resistant mice and cytokine and NRAMP knockout mice, effects of inoculation of isolated parasites, and treatment with sulfadiazine or alphaPD1 ligand were studied.

RESULTS

Twelve months after infection, a time equivalent to middle to early elderly ages, mice had behavioral and neurological deficits, and brain MRIs showed mild to moderate ventricular dilatation. Lower brain weight correlated with greater magnitude of neurologic abnormalities and inflammation. Full genome microarrays of brains reflected inflammation causing neuronal damage (Gfap), effects on host cell protein processing (ubiquitin ligase), synapse remodeling (Complement 1q), and also increased expression of PD-1L (a ligand that allows persistent LCMV brain infection) and CD 36 (a fatty acid translocase and oxidized LDL receptor that mediates innate immune response to beta amyloid which is associated with pro-inflammation in Alzheimer's disease). Immunostaining detected no inflammation around intra-neuronal cysts, practically no free tachyzoites, and only rare bradyzoites. Nonetheless, there were perivascular, leptomeningeal inflammatory cells, particularly contiguous to the aqueduct of Sylvius and hippocampus, CD4+ and CD8+ T cells, and activated microglia in perivascular areas and brain parenchyma. Genetically resistant, chronically infected mice had substantially less inflammation.

CONCLUSION

In outbred mice, chronic, adult acquired T. gondii infection causes neurologic and behavioral abnormalities secondary to inflammation and loss of brain parenchyma. Perivascular inflammation is prominent particularly contiguous to the aqueduct of Sylvius and hippocampus. Even resistant mice have perivascular inflammation. This mouse model of chronic T. gondii infection raises questions of whether persistence of this parasite in brain can cause inflammation or neurodegeneration in genetically susceptible hosts.

Reproductive failure in mice chronically infected with Toxoplasma gondii

Nya: NYLAR female mice infected with Toxoplasma gondii for 1 and 2 months were cohabited with normal males for 1 week, then sequestered individually to monitor their reproductive performance. Mice bred 1 month postinfection (p.i.) exhibited reproductive failure, with 1 of 16 females delivering 2 sickly pups; in others, interruption of pregnancy and fetal wastage occurred. Mice infected for 2 months were uniformly infertile. Vaginal lavage showed cessation of estrus cycling and constant diestrus cytology at as early as 1 month p.i. Histologic examination of the ovaries revealed impaired folliculogenesis and few corpora lutea, if any. Uterine atrophy was marked. Coronal sections of the cerebrum disclosed widespread vasculitis, focal disruptions of the ependymal cell layer lining the lateral and third ventricles, and periventricular edema. We suggest that the reproductive failure of the infected mice is due to an acquired hypogonadotropic hypogonadism secondary to hypothalamic dysfunction.

Chronic murine toxoplasmosis: clinicopathologic characterization of a progressive wasting syndrome

Nya:NYLAR albino mice infected with Toxoplasma gondii gradually developed a chronic and progressive wasting syndrome characterized by facial and body alopecia, corneal opacities, necrotic lesions of ears and tail, signs of neurologic disease and death within six to eight months after infection. Haematologic changes included a transient normochromic, normocytic anaemia, and persistent lymphopenia and neutrophilia. Changes in serum proteins were manifested by hypoalbuminaemia and pronounced hypergammaglobulinaemia. Serum thyroxine concentrations fell sharply during the first month of infection, then gradually returned to control concentrations. Gross changes included loss of body weight, hepatosplenomegaly, ovarian and uterine atrophy, and a marked involution of the thymus. The predominant histopathologic change in the brain was a mononuclear cell vasculitis, particularly affecting the hippocampus and the choroid plexus, ependyma, and periventricular areas of the lateral and third ventricles. These preliminary observations indicate that mice can serve as a practical animal model of great potential for study of the pathogenesis of chronic toxoplasmosis.

Activation of murine macrophages and a bovine monocyte cell line by bovine lymphokines to kill the intracellular pathogens Eimeria bovis and Toxoplasma gondii

Macrophage (M phi)-activating lymphokines present in concanavalin A-stimulated bovine T-lymphocyte cultures (ConAS) were studied by assessing their effects on Eimeria bovis and Toxoplasma gondii growth in cultured bovine monocytes (BM) and mouse M phi. The in vitro development of both parasites was assessed by incorporation of [3H]uracil and by microscopic examination of parallel cultures. Incorporation of [3H]uracil into infected cultures was an accurate indicator of growth of both E. bovis and T. gondii in BM and mouse M phi. Sporozoites of E. bovis underwent merogony in untreated BM but not in mouse M phi, whereas T. gondii developed in both cell types. Inhibition of T. gondii growth was greatest in ConAS-treated BM, whereas preincubation of mouse M phi with ConAS resulted in about 80% growth inhibition. There was no significant difference between the inhibition of either T. gondii sporozoite- or tachyzoite-induced growth in ConAS-treated cells, showing that activation pathways are equally effective against both stages. Treatment of ConAS with glycine-hydrochloride buffer (pH 2) resulted in a total loss of antiviral activity mediated by gamma interferon (IFN-gamma). When pH 2 dialyzed ConAS was used to activate BM, inhibition of T. gondii growth was only partially affected. Because bovine IFN-gamma does not activate mouse M phi and due to the partial effects of pH 2 on ConAS-induced growth inhibition, the major component(s) of ConAS responsible for T. gondii growth inhibition is distinct from IFN-gamma. Furthermore, IFN-gamma may act synergistically rather than being part of a priming sequence for M phi responsiveness to other lymphokines. Murine recombinant granulocyte-macrophage colony-stimulating factor (rGM-CSF) was tested for any microbistatic activity against T. gondii sporozoites and tachyzoites. There was no significant difference in either colony formation or [3H]uracil incorporation between rGM-CSF-treated and control cultures, regardless of host cell type. Thus, rGM-CSF does not induce adequate M phi activation to kill T. gondii and is not a major microbistatic component of ConAS. rGM-CSF also had no effect on T. gondii infection in vivo.