Intratumoral injection of Clostridium novyi-NT spores induces antitumor responses

Species of Clostridium bacteria are notable for their ability to lyse tumor cells growing in hypoxic environments. We show that an attenuated strain of Clostridium novyi (C. novyi-NT) induces a microscopically precise, tumor-localized response in a rat orthotopic brain tumor model after intratumoral injection. It is well known, however, that experimental models often do not reliably predict the responses of human patients to therapeutic agents. We therefore used naturally occurring canine tumors as a translational bridge to human trials. Canine tumors are more like those of humans because they occur in animals with heterogeneous genetic backgrounds, are of host origin, and are due to spontaneous rather than engineered mutations. We found that intratumoral injection of C. novyi-NT spores was well tolerated in companion dogs bearing spontaneous solid tumors, with the most common toxicities being the expected symptoms associated with bacterial infections. Objective responses were observed in 6 of 16 dogs (37.5%), with three complete and three partial responses. On the basis of these encouraging results, we treated a human patient who had an advanced leiomyosarcoma with an intratumoral injection of C. novyi-NT spores. This treatment reduced the tumor within and surrounding the bone. Together, these results show that C. novyi-NT can precisely eradicate neoplastic tissues and suggest that further clinical trials of this agent in selected patients are warranted.

Lactobacilli-expressed single-chain variable fragment (scFv) specific for intercellular adhesion molecule 1 (ICAM-1) blocks cell-associated HIV-1 transmission across a cervical epithelial monolayer

The vaginal and cervical epithelia provide an initial barrier to sexually acquired HIV-1 infection in women. To study the interactions between HIV-1-infected cells or cell-free HIV-1 and the reproductive epithelium, the transmission of HIV-1 by infected cells or cell-free virus across human cervical epithelial cells was examined using a Transwell culture system. Cell-associated HIV-1 was transmitted more efficiently than cell-free virus, and monocyte-associated virus was transmitted most efficiently. Abs to ICAM-1 added to the apical side of the epithelium blocked cell-mediated transepithelial HIV-1 transmission in vitro. When used in a previously described model of vaginal HIV-1 transmission in human PBL-SCID mice, anti-murine ICAM-1 Abs (0.4 microg/10 microl) also blocked vaginal transmission of cell-associated HIV-1 in vivo. To evaluate a candidate delivery system for the use of this Ab as an anti-HIV-1 microbicide, anti-ICAM single-chain variable fragment Abs secreted by transformed lactobacilli were evaluated for their protective efficacy in the Transwell model. Like the intact Ab and Fab derived from it, the single-chain variable fragment at a concentration of 6.7 microg/100 microl was able to reduce HIV-1 transmission by 70 +/- 5%. These data support the potential efficacy of an anti-ICAM Ab delivered by lactobacilli for use as an anti-HIV-1 microbicide.

Low pH immobilizes and kills human leukocytes and prevents transmission of cell-associated HIV in a mouse model

Background

Both cell-associated and cell-free HIV virions are present in semen and cervical secretions of HIV-infected individuals. Thus, topical microbicides may need to inactivate both cell-associated and cell-free HIV to prevent sexual transmission of HIV/AIDS. To determine if the mild acidity of the healthy vagina and acid buffering microbicides would prevent transmission by HIV-infected leukocytes, we measured the effect of pH on leukocyte motility, viability and intracellular pH and tested the ability of an acidic buffering microbicide (BufferGel^®) to prevent the transmission of cell-associated HIV in a HuPBL-SCID mouse model.

Methods

Human lymphocyte, monocyte, and macrophage motilities were measured as a function of time and pH using various acidifying agents. Lymphocyte and macrophage motilities were measured using video microscopy. Monocyte motility was measured using video microscopy and chemotactic chambers. Peripheral blood mononuclear cell (PBMC) viability and intracellular pH were determined as a function of time and pH using fluorescent dyes. HuPBL-SCID mice were pretreated with BufferGel, saline, or a control gel and challenged with HIV-1-infected human PBMCs.

Results

Progressive motility was completely abolished in all cell types between pH 5.5 and 6.0. Concomitantly, at and below pH 5.5, the intracellular pH of PBMCs dropped precipitously to match the extracellular medium and did not recover. After acidification with hydrochloric acid to pH 4.5 for 60 min, although completely immotile, 58% of PBMCs excluded ethidium homodimer-1 (dead-cell dye). In contrast, when acidified to this pH with BufferGel, a microbicide designed to maintain vaginal acidity in the presence of semen, only 4% excluded dye at 10 min and none excluded dye after 30 min. BufferGel significantly reduced transmission of HIV-1 in HuPBL-SCID mice (1 of 12 infected) compared to saline (12 of 12 infected) and a control gel (5 of 7 infected).

Conclusion

These results suggest that physiologic or microbicide-induced acid immobilization and killing of infected white blood cells may be effective in preventing sexual transmission of cell-associated HIV.

Vaginal transmission of cell-associated HIV-1 in the mouse is blocked by a topical, membrane-modifying agent

Because both HIV-1 virions and HIV-infected cells are present in the semen and cervical mucus of infected individuals, HIV-1 prevention strategies must consider both cell-free and cell-associated virus. Antibodies that target HIV-1 virions have been shown to prevent vaginal transmission of cell-free virus in macaques, but since cell-associated transmission has not been reliably demonstrated in this model system, no strategies to prevent such transmission have been tested. We have employed a mouse model in which SCID mice carry human peripheral blood leukocytes (HuPBLs). In these mice, vaginal transmission of cell-associated, but not cell-free, HIV-1 transmission occurs, mediated by transepithelial migration of HIV-infected cells. Topical application of beta-cyclodextrin (beta-CD), a cholesterol-sequestering agent that interferes with cell migration and budding of virus from lipid rafts, blocks transmission of cell-associated HIV-1. The HuPBL-SCID model of vaginal HIV-1 transmission should prove useful for investigating cell-associated HIV-1 transmucosal HIV-1 transmission, as well as for screening reagents for their potential efficacy in preventing sexual HIV-1 transmission.

Summary of the first round analyses of the Third International Workshop on Swine Leukocyte Differentiation Antigens

The reactivity of 155 monoclonal antibodies submitted to the Third International Workshop on Swine Leukocyte Differentiation Antigens, together with 41 internal standards, was analysed by flow cytometry on 29 different pig cell targets as well as two human cell targets as a means of establishing suitable panels of monoclonal antibodies for more detailed clustering analyses by the various subsections of the workshop. Results were collected either without further gating, with gating based on FS/SS characteristics or with gating based on the co-expression of a reference antibody in two-colour flow cytometry. The CD or SWC reactivity of the internal standards had been established in previous workshops. Data sets were subsequently analysed by statistical clustering using the Leucocyte Typing Database IV software. The resulting 18 cluster groups were allocated to the appropriate second round sections of the workshop, after reviewing the overall cellular reactivity of each cluster as well as the specificity of known standards which clustered in a group.

Overview of the Third International Workshop on Swine Leukocyte Differentiation Antigens

The aim of the Third International Workshop on Swine Leukocyte Differentiation Antigens (CD workshop), supported by the Veterinary Immunology Committee (VIC) of the International Union of Immunological Societies (IUIS), was to standardize the assignment of monoclonal antibodies (mAb) reactive with porcine leukocyte differentiation antigens and to define new antibody clusters, using nomenclature in accordance with human and ruminant CD nomenclature, as agreed at the summary meeting of the Second International Swine CD Workshop in Davis, 1995: only mAb with proven reactivity for the orthologous porcine gene product or cross-reactivity for the human gene products, were given the full CD nomenclature, all other allocations were prefixed with "w". As in previous workshops, the overall organization was entrusted to the chair and first author, with support by the chair of the previous workshop and second author. In addition to the existing 26 pig leukocyte CD/SWC determinants established in previous workshops, this workshop established/confirmed another 11 CDs for pig leukocytes, identified by a total of 21 mAb: CD11R1 (2 mAb), CD11R2 (1 mAb), CD11R3 (4 mAb), wCD40 (1 mAb), wCD46 (4 mAb), wCD47 (3 mAb), wCD49d (1 mAb), CD61 (1 mAb), wCD92 (1 mAb), wCD93 (1 mAb) and CD163 (2 mAb).

Differences among HIV-1 variants in their ability to elicit secretion of TNF-alpha

HIV-1 infection of human PBMC has been shown to elicit secretion of several different cytokines. TNF-alpha secretion induced by this virus has been of particular interest because it has been associated with the development of HIV-1 dementia and because TNF-alpha increases viral replication by enhancing NF-kappaB interaction with the viral promoter, the HIV-1 long terminal repeat. Thus, an autocrine pathway is potentially created in which HIV-1 stimulates its own replication. Conflicting reports exist, however, on the ability of HIV-1 to induce TNF-alpha secretion in vitro or in vivo. Using experimental protocols that controlled for potential bacterial endotoxin-induced TNF-alpha secretion, the current study demonstrates significant differences in TNF-alpha-eliciting properties among primary and laboratory obtained HIV-1. The relative TNF-alpha-inducing ability of different variants is conserved when tested using PBMC from different individuals. Elicitation of TNF-alpha secretion was not blocked by exposure of cells to zidovudine, indicating that viral integration was not required to induce secretion. Rather, the interaction between the virus and cell surface is critical for TNF-alpha induction, as Abs against CD4 or CCR5 blocked the induction of TNF-alpha synthesis by PBMC when added before virus exposure. Furthermore, the ability to induce TNF-alpha secretion mapped to a region of the HIV-1 env gene that includes the third hypervariable domain. Differences in the ability of different HIV-1 variants to elicit TNF-alpha may account for individual differences in HIV-1 disease course.

A perspective on cellular immunity in the elderly

The increased incidence of infection and malignancy in elderly individuals has prompted many studies that demonstrate that the aging immune system is impaired. Most of these studies have focused on the impairment of acquired immunity provided by lymphocytes. While defects in acquired humoral and T-cell-mediated immunity may exist, increased susceptibility to infection may result from defects in the constitutive functioning of macrophages and granulocytes. Recognition of the potential importance of defects in constitutive immunity in the elderly may provide new opportunities for therapeutic and prophylactic intervention in this population.

Opiates and infection

This review on the effects of opiate use on infectious diseases discusses the complete spectrum of infections in the opiate user, including those of the lung, the GI tract, the skin, the skeletal system, and the CNS. There is both increased prevalence and increased severity of bacterial and viral infections in injection drug users with the outcome of increased morbidity and mortality. The experimental administration of opiates has lead to a greater understanding of the effects on susceptibility to and progression of infectious diseases. Animal models of opiate dependence and infection are reviewed with specific attention to cases in which the opiate-mediated effects are harmful and in which cases they are beneficial.

Infection of swine with Mycobacterium bovis as a model of human tuberculosis

Swine were infected with Mycobacterium bovis to develop a model for pulmonary and disseminated tuberculosis in humans. Pigs were inoculated with various doses of M. bovis by intravenous (i.v.), intratracheal (int), or tonsillar routes. Animals were euthanized between 17 and 60 days after inoculation, and tissues were collected for culture and histopathologic examination. Lesions of disseminated tuberculosis were found in pigs given 10(4) or 10(8) cfu of M. bovis i.v. or int; localized pulmonary disease was found in pigs given 10(2) or 10(3) cfu of M. bovis int. Lesions ranged from well-organized tubercles with coagulative necrosis, epithelioid macrophages, and fibrosis to large expansive tubercles with liquefactive necrosis and extracellular growth of M. bovis. Tuberculous meningitis was observed in animals given M. bovis i.v. Swine infected with M. bovis are a useful animal model for elucidating the mechanisms of pathogenesis and host defense to tuberculosis in humans.

Differential infection of porcine alveolar macrophage subpopulations by nonopsonized Mycobacterium bovis involves CD14 receptors

The resurgence in mycobacterial infection worldwide has led to renewed attention to the pathogenesis of Mycobacterium species. The purpose of this study was to characterize the infection of alveolar macrophages (AMs) by nonopsonized Mycobacterium bovis, and to elucidate the mechanism by which a differential infection of subpopulations of AM may occur. A difference in susceptibility to Mycobacterium bovis infection of subpopulations of AMs was observed, such that the least dense cells were the least susceptible (21.4 +/- 10.7%) and the most dense cells were the most readily infected (61.8 +/- 5.6%). The percentage of AMs staining for CD14 receptors showed a similar differential distribution, with fewer of the least dense cells expressing CD14 and a greater percentage of the most dense cells staining for CD14 receptor expression. To investigate the role of CD14 receptors in the infection of AMs, anti-CD14 antibody was added to the cell cultures. Infection of AM by Mycobacterium bovis was blocked by up to 60.2% by anti-CD14 antibody but not by isotype control antibody. The results of this study suggest that Mycobacterium bovis selectively infects AM subpopulations, specifically those with the greatest expression of CD14, a putative receptor mechanism for Mycobacterium bovis infection of porcine AM.

Cytokine and free radical production by porcine microglia

Swine have been used increasingly as an animal model for a variety of immunologic purposes. Because the functional activities of porcine microglia, the resident macrophages of the brain, have not been elucidated, highly enriched porcine microglial cell cultures were developed in the present study to assess cytokine and free radical production by these cells compared to microglia of human and murine origin. Porcine microglial cells were found to behave similarly to both human and murine cells in releasing tumor necrosis factor-alpha and interleukin-1 and in generating superoxide anion. In contrast to murine cells, porcine microglial cells, like human cells, failed to generate NO in response to cytokine stimulation. These findings suggest that swine will serve as an excellent model for investigations of central nervous system diseases in which microglia are involved in host defense or neuronal injury.