Activity of rabbit monocytes, macrophages, and neutrophils in antibody-dependent cellular cytotoxicity of herpes simplex virus-infected corneal cells

Neutrophils protect the retina of the injected eye from infection after anterior chamber inoculation of HSV-1 in BALB/c mice

PURPOSE

To determine whether infiltrating polymorphonuclear leukocytes PMNs play a role in preventing early direct anterior-to-posterior spread of herpes simplex virus (HSV)-1 and/or in preventing the spread of HSV-1 from the brain back to the retina of the injected eye after anterior chamber (AC) inoculation.

METHODS

BALB/c mice were treated with monoclonal antibody RB6-8C5 (Gr-1) against PMNs or control IgG and inoculated with HSV-1.

RESULTS

In Gr-1-treated mice, PMNs were depleted in the peripheral blood and in the HSV-1-infected eye. More virus (2-3 logs) was recovered from the inoculated eye of Gr-1 antibody-treated mice than from control mice. Immunohistochemistry revealed disseminated virus-infected cells in the junction between the anterior and the posterior segment and also in the posterior segment of the HSV-1-inoculated eye in Gr-1-treated mice. In control IgG-treated mice, virus-infected cells were observed only within the AC. More virus (3 logs) was recovered from the contralateral suprachiasmatic nucleus (SCN), and increased virus staining was observed in the ipsilateral optic nerve of Gr-1-treated mice compared with control mice. In Gr-1-treated mice, the central retina was virus-infected in a patchy fashion beginning on day 7 post infection (pi), and the infection progressed to involve the entire retina.

CONCLUSIONS

Since both direct anterior-to-posterior spread of virus and spread via the optic nerve occurred in PMN-depleted mice, these results suggest that PMNs play an important role both in limiting intraocular spread of virus in the injected eye and in controlling spread of the virus from the brain into the optic nerve and retina of the injected eye.

Cytotoxic interactions between bovine parainfluenza type 3 virus and bovine alveolar macrophages

This paper describes an investigation of the cytotoxic activity of bovine alveolar macrophages for parainfluenza type 3 (PI-3) virus-infected target cells, using 51Cr release assays. Alveolar macrophages from uninfected calves were shown to be capable of killing PI-3 virus infected cells without the presence of antibody or complement (antibody-independent cell-mediated cytotoxicity). The level of killing was shown to vary from animal to animal with specific lysis values ranging from <5% to 70%. Presence of PI-3 virus antiserum was shown to inhibit, rather than enhance macrophage cytotoxicity in a dose-dependent manner, suggesting that bovine alveolar macrophages do not always exhibit antibody-dependent lysis in all cases. Following intranasal and intratracheal inoculation of calves with PI-3 virus, the level of cytotoxicity by macrophages lavaged from the lungs of the calves increased substantially, and by Day 5 post inoculation, levels of 95% to 98% specific lysis were recorded. After Day 5, the killing ability decreased rapidly to low levels. Cell-free lavage fluids, collected from PI-3 virus infected and control calves at various times throughout the experiment, were incubated with aliquots of an alveolar macrophage population from an uninfected donor calf, which initially showed a low level of killing, and were subsequently added to PI-3 virus infected target cells. The recorded levels of cytotoxicity, mirrored those which were seen with the initial macrophage effector cells from the infected and control animals, suggesting that macrophage cytotoxicity was largely controlled by extracellular factors.

Acute inflammatory response to cowpox virus infection of the chorioallantoic membrane of the chick embryo

The chick embryo chorioallantoic membrane was used to study the acute inflammatory response in the absence of contributions from the immune system. In preliminary experiments, lesions of wild-type cowpox virus strain Brighton (CPV-BR) and a 38K gene deletion mutant of CPV-BR (CPV-BR.D1) were compared with vaccinia virus (strains WR and Copenhagen), fowlpox virus, laryngotracheitis virus, and infectious tenosynovitis virus, and were ranked for degree of induced inflammation. The maximal and minimal inflammatory responses were observed with CPV-BR.D1 and CPV-BR viruses, respectively. CPV-BR.D1 lacks a 38K gene which encodes an anti-inflammatory 38-kDa protein that has homology to SERPINs. The kinetics and character of the inflammatory response were examined further in the wild-type CPV-BR and mutant CPV-BR.D1 infections using cell counts, electron microscopy, and assays for inflammatory cell activation. CPV-BR virus infection rapidly spread through the ectoderm, uniformly infecting all cells with the production of large amounts of virions and viral-induced cytopathic effect, but evoking little or no inflammatory response until 144 hr p.i. The CPV-BR.D1 infection, on the other hand, was rapidly contained by a dexamethasone-sensitive inflammatory response mainly of activated heterophils which was advanced by 36 hr p.i. Both infections resulted in disseminated disease with similar numbers of liver lesions and only a slight difference in the LD50, with the CPV-BR.D1 values being higher than that for CPV-BR virus. In this model, the acute inflammatory response alone is unable to prevent disseminated disease and associated mortality.

Cytotoxicity of bovine leucocytes for parainfluenza type-3 virus-infected cells

The cytotoxic effect of bovine neutrophils, alveolar macrophages, monocytes and lymphocytes for parainfluenza type-3 (PI-3) virus-infected cells in 51chromium-release assays is described. Specific lysis of virus-infected target cells with PI-3 virus antibody and complement was first observed 8 h after infection coincident with the appearance of haemadsorption-positive cells. Specific lysis increased rapidly reaching a peak 18-24 h after infection. This increase was paralleled by the increase in the percentage of cells with surface haemagglutinin. Target cells were subsequently used in 51chromium-release assays between 18 and 20 h after virus infection. Antibody-independent killing of PI-3 virus-infected cells was observed with neutrophils, alveolar macrophages and lymphocytes. Levels of specific lysis up to 30% for neutrophils and 68% for alveolar macrophages were observed, although there was considerable variation in activity from animal to animal. Lymphocyte preparations showed levels of cytotoxicity up to 20% in some cases while monocytes had low killing ability. Addition of PI-3 virus-specific antibodies enhanced killing by neutrophils, monocytes and lymphocytes but inhibited killing by alveolar macrophages. Complement, particularly guinea pig complement, was cytotoxic for virus-infected but not for uninfected cells, and also considerably enhanced the cytotoxic effect of neutrophils and lymphocytes.

Natural cell-mediated immunity in the rabbit

Susceptibility and resistance to tumors represent the interplay of many factors. One factor felt to govern the development of tumors is natural killer and natural cytotoxic cellular activity. The constitutional resistance of rabbits to spontaneous tumor development raises questions regarding the activity of natural cell-mediated immunity in this species. We therefore examined the ability of rabbit spleen, lymph node, and peripheral blood lymphocytes to mediate natural killer cell (NK) and natural cytotoxic cell (NC) activity in vitro. Using classical approaches to the study of NK and NC activity, we found no evidence of these activities in leporine spleen, lymph node, and peripheral blood lymphocytes. Preincubation of these cells with IL-2 did not induce such activity. Antibody-dependent cell-mediated cytotoxic reactivity (ADCC), which is believed to be mediated by NK cells, was also undetectable in rabbit lymphocytes. As controls, lymphocytes from other species were capable of mediating NK, NC, and ADCC functions normally in these experiments. Finally, we were unable to identify a population of large granular lymphocytes, the cells believed to mediate NK activity in other animals. Therefore, we could not demonstrate in the rabbit either natural cell-mediated immunity or the population of cells usually associated with natural cell-mediated immunity. If such activity exists in rabbits, it is different from that seen in other animals. More likely, the basis for the natural resistance of rabbits to tumor development must be sought elsewhere.

Cell density dependency of vitreous fibrosis induced by monocytes and lymphocytes

The possible roles of monocytes and lymphocytes in vitreous fibrosis were examined by injecting various numbers of the peripheral cell types into the rabbit vitreous. Our results indicated that the degree of vitreous fibrosis and the presence of traction retinal detachment corresponded to the number of cells injected. It was suggested that these findings are probably similar to vitreous membrane formation and retinal detachment in various clinical ocular diseases or inflammations in humans.

Antibody-dependent cellular cytotoxicity mediated by polymorphonuclear leukocytes and mononuclear cells against HSV-1 infected primary cultures of rabbit corneal epithelium

The roles of rabbit polymorphonuclear leukocytes (PMNL) and mononuclear cells (MC) for the regulation of ocular herpes simplex virus-1 (HSV-1) infection were studied. The antibody-dependent cellular cytotoxicity (ADCC) mediated by PMNL and MC from normal rabbit peripheral blood was assessed kinetically employing a specific 51Cr release assay. The HSV-1 infected primary cultures of rabbit corneal epithelium (PRCE) were used as the target cells to obtain a homologous assay system. The PRCE was prepared by an epithelium outgrowth technique and identified by electron microscopy. The expression of the surface HSV-1 antigens on PRCE was examined by indirect immunofluorescent staining; the cell population stained by fluorescein increased from 40% at 3 hr postinfection (PI) to 100% at 8 hr PI. To determine how early the cytotoxicity occurs, PRCE were infected with HSV-1 for 2 hrs. After 2 hrs, the ADCC was checked every 10 min for the first 40 min and then at 1, 2 and 4 hr of incubation. The cytotoxicity was apparent at 10 min postincubation and reached 46% by PMNL and 40% by MC at 4 hr postincubation (6 hr PI). Significant cytotoxic effect (26% by PMNL and 16% by MC) occurred as early as 3 hr PI. When the one-step growth cycle of HSV-1 was studied in the PRCE, HSV-1 had an eclipse period of 4 hr and a rise period of 8 hr. This suggests that rabbit PMNL and MC have the potential to eliminate the HSV-1 infected rabbit corneal epithelium before HSV matures in the cells.

Alteration of rabbit alveolar and peritoneal macrophage function by herpes simplex virus

Exposure of rabbit alveolar and peritoneal macrophages to infectious herpes simplex virus resulted in inhibition of antibody-dependent cellular cytotoxicity and either enhancement or inhibition of phagocytosis. At all times after exposure, virus was inhibitory to peritoneal macrophage phagocytosis. Alveolar macrophages showed enhanced phagocytic activity in the early stages of virus exposure and inhibition at later time points.