Impaired resistance to bacterial infection after tumor implant is traced to lactic dehydrogenase virus

Making Mouse Models That Reflect Human Immune Responses

Humans are infected with a variety of acute and chronic pathogens over the course of their lives, and pathogen-driven selection has shaped the immune system of humans. The same is likely true for mice. However, laboratory mice we use for most biomedical studies are bred in ultra-hygienic environments, and are kept free of specific pathogens. We review recent studies that indicate that pathogen infections are important for the basal level of activation and the function of the immune system. Consideration of these environmental exposures of both humans and mice can potentially improve mouse models of human disease.

Implications of infectious agents on results of animal experiments

Report of the Working Group on Hygiene of the Gesellschaft für Versuchstierkunde–Society for Laboratory Animal Science (GV-SOLAS)

GV-SOLAS Working Group on Hygiene: Werner Nicklas (Chairman), Felix R. Homberger, Brunhilde Illgen-Wilcke, Karin Jacobi, Volker Kraft, Ivo Kunstyr, Michael Mähler, Herbert Meyer & Gabi Pohlmeyer-Esch

The Impact of General Laboratory Animal Health on Experimental Models in Antimicrobial Chemotherapy

This chapter describes how the poor health of a laboratory animal can adversely the experimental models used in antimicrobial research. Concerns for the health of laboratory animals have mostly focused on spontaneous infections, although disease in laboratory animals may also be caused by genetic or environmental determinants. The presence of various pathogenic microorganisms may cause changes in the organs, resulting in difficulties in the interpretation of the pathological diagnosis included in the evaluation of many microbiological models. The immune system may be modulated by spontaneous infections in the absence of clinical disease. This effect may be either suppressive or activating or both at the same time, but on different parts of the immune system. Some microorganisms have a specific effect on enzymatic, haematological, and other parameters, which are monitored in the animal during an experiment. Organic function disturbances may change the outcome of the experiment without the knowledge of the scientist. Spontaneous infections in an experimental infection model may also compete with the experimental infection, which in the worst cases may fail. Microorganisms present in the animal may contaminate samples and tissue specimens, such as cells and sera. This may complicate the in vitro maintenance of cell lines, and may interfere with experiments performed on cell cultures or isolated organs. To avoid disease, microbial interference, and zoonoses, laboratory animals are produced according to a three-step principle, which include rederivation, barrier protection, and health monitoring. Rederivation means the production of animals to initiate breeding colonies by either caesarian section or embryo transfer.

Macrophage function in the acute phase of lactic dehydrogenase virus-infection of mice: suppression of superoxide anion production in normal mouse peritoneal macrophages by interferon-alpha in vitro

The effect of interferon (IFN)-alpha on the release of superoxide anions (O2-) by normal mouse macrophages (PEM) was examined. Sera from LDV-infected mice at 1 day, but not at 7 days post-infection, suppressed the O2- release by PEM. When PEM were exposed in vitro for 24 h to IFN-alpha, their capacity to release O2- was significantly suppressed. Progressive suppression of O2- release with increasing IFN-alpha concentration was observed. These results suggest that IFN-alpha in the circulation may be one of several suppressive factors on macrophage function in the early phase of infection and IFN-alpha may play a modulatory role in inflammation and immunity.

Effect of a factor released by K562 malignant cells in culture on human neutrophil bactericidal activity

We have previously demonstrated that k562 malignant cells in culture contain and release a low-molecular-mass (8-kDa) factor that inhibits adherence-related functions of neutrophils but does not alter fMet-Leu-Phe- or phorbol ester-induced oxidative burst (M. Amar, N. Amit, T. Pham Huu, S. Chollet-Martin, M.T. Labro, M.A. Gougerot-Pocidalo, and J. Hakim, J. Immunol. 144:4749-4756, 1990). In this study, we investigated the effects of this factor, referred to as inhibitory factor 1 (IF1), on the bactericidal activity of human polymorphonuclear cells (PMNs) on Staphylococcus aureus opsonized in various ways. S. aureus was used either nonopsonized or opsonized with heat-inactivated serum or normal serum containing complement factors. The bactericidal activity of PMNs preincubated with IF1-treated or control medium was examined by counting the surviving bacteria. The ability of IF1-treated PMNs to kill bacteria was diminished when they were opsonized with normal serum. When S. aureus was not opsonized or was opsonized with heat-inactivated serum, the bactericidal activity of IF1-treated PMNs was similar to that of controls. Likewise, the phagocytosis of IF1-treated PMNs was diminished when S. aureus was opsonized with normal serum but was not altered when S. aureus was not opsonized or was opsonized with heat-inactivated serum. These results suggest that the decrease in killing might be due to defective ingestion. The chemiluminescence response of IF1-treated PMNs was inhibited when S. aureus was not opsonized or was opsonized with normal serum. No effect on chemiluminescence was observed when S. aureus was opsonized with heat-inactivated serum. These results suggest that IF1 interferes not only with S. aureus stimulation of PMNs via complement receptors but also with oxygen-dependent bactericidal activity.

Tumour enhancement associated with induction of abscesses in mice bearing a transplantable solid tumour

A model of intraabdominal sepsis in the tumour-bearing host was established in order to study the interactions between host, tumour and infecting organisms. BALB/c mice bearing a transplanted tumour were given an intraperitoneal inoculum containing Bacteroides fragilis, Escherichia coli and bran as an abscess-potentiating agent. Tumour-bearing mice formed abscesses which were not significantly smaller than in controls except late in tumour growth. The bacterial contents of the abscesses were not significantly different to controls. In contrast, mice given an abscess-inducing mixture at or near the time of tumour cell inoculation had tumours which were significantly larger than in controls. The mechanism of tumour enhancement is not known.

Inhibition of normal rat macrophage functions by soluble tumor products. Effect of systemic treatment with bacterial immunomodulators

The phagocytic and chemotactic activities of normal rat peritoneal macrophages were inhibited by sera from tumor-bearing rats (TBR) and 3 M KCl extracts of tumor mass. However, sera from Corynebacterium parvum- or Listeria monocytogenes-treated TBR did not inhibit phagocytosis. On the other hand, sera from C. parvum-treated, but not from L. monocytogenes-treated TBR still inhibited the chemotactic response of the normal macrophages. Furthermore, 3 M KCl extracts of tumors from C. parvum-treated TBR did not inhibit phagocytosis and chemotactic response of the same cells. Similar results were obtained with extracts of tumor masses from L. monocytogenes-treated rats. It is suggested that treatment with bacterial immunomodulators can influence the release from neoplastic cells of soluble products influencing normal macrophage functions.

A tumor-associated lactic dehydrogenase virus suppresses the host resistance to infection with Listeria monocytogenes

Infection of mice with lactic dehydrogenase virus (LDV) causes a lifelong chronic infection which is followed by alterations in immune responses during the acute phase of the infection. LDV was found to impair many functions of the reticuloendothelial system and to suppress macrophage-dependent immune responses. We tested the effect of acute infection with LDV in mice on the macrophage-mediated resistance to infection with a virulent bacterium. We found that LDV reduces the host's capacity to resist infection with Listeria monocytogenes. Many tumor lines which are transferred in mice are infected with LDV, and their growth rate is affected by the presence of the virus. It is therefore important to distinguish between immune alterations in tumor-bearing mice which are caused by the progressive growth of the tumor and those which are secondary to the viral infection. We tested whether LDV and a circulatory factor from tumor-bearing mice with similar suppressive effects on anti-Listeria immunity are two different entities or whether they are similar. We found that the factor is associated with LDV-infected tumor cells and is absent in LDV-free tumor cells. Other biological and physical characteristics supported the assumption that the tumor-associated factor is the LDV.

Antibody classes and subclasses in circulating immune complexes isolated from mice infected with lactic dehydrogenase virus

A chronological study of circulating immune complexes (CIC) in lactic dehydrogenase virus (LDV)-infected mice has been performed. The results demonstrate that CIC containing immunoglobulin of the IgM class were isolated between days 3 and 9 post-LDV infection and corresponded to an increase in serum IgM. IgG1-containing CIC were also transient in the serum of LDV-infected mice in that they were isolated only between days 5 and 13. The occurrence of IgG1 CIC did correlate with an increase in total IgG1 in the serum, however, it did correlate with a small (1:10) increase in IgG1 anti-LDV activity. In contrast, CIC containing immunoglobulin of the serum IgG2 subclass were not isolated from LDV-infected serum until 15 days post infection. This chronological appearance of IgG2 CIC did not correlate with the observed increase in total IgG2 concentration in LDV-infected mice on day 7, however, was analogous to the rapid increase in free serum LDV-specific antibody. We propose that the non-specific suppression of the immune response and tumour enhancement during the acute phase of LDV infection could be due to the immunoregulatory properties of IgG1 CIC.