Respiratory syncytial virus infection of alveolar macrophages in adult transplant patients

Pulmonary epithelial cells are thought to be the primary cellular targets for infection by respiratory syncytial virus (RSV) in vivo. To determine whether other pulmonary cells are infected by RSV, bronchoalveolar lavage cells from six adult transplant patients, four of whom had acute RSV infection, were examined by in situ immunohistochemistry to identify infected lung cells. Both alveolar macrophages and epithelial cells were infected with RSV in vivo. At the single-cell level, three-color immunofluorescent studies revealed that both RSV-infected epithelial cells and alveolar macrophages expressed Class II molecules of the major histocompatibility complex, but only the alveolar macrophage coexpressed interleukin-1 beta. Paraformaldehyde-fixed bronchoalveolar lavage cells from RSV-infected but not uninfected patients induced a marked proliferative response by cloned T cells indicating that in vivo infected cells expressed bioactive interleukin-1. Together, these studies indicate that the alveolar macrophage may have a critical role in the lung immune response to RSV.

Respiratory syncytial virus infection of human primary nasal and bronchial epithelial cell cultures and bronchoalveolar macrophages

In adults, clinical symptoms caused by respiratory syncytial virus (RSV) are usually confined to the upper respiratory tract, whereas RSV infection in infants frequently causes bronchiolitis and pneumonia. The preferential localization of RSV infection to the upper airways may partially be due to protective immunity, but may also depend on a difference in susceptibility of epithelial cells from upper and lower airways, or on antiviral activities of bronchoalveolar macrophages (AM). In this study, we have compared the susceptibility of primary adult human nasal epithelium, primary adult human bronchial epithelium, a human bronchial epithelial cell line (BEAS-2B), and adult human AM to infection with RSV. The cell cultures were infected with multiplicities of infection (moi) of 1 and 0.1. Virus release into the supernatants was assayed at days 1, 2, 4, and 7, and the percentage of virus-positive cells determined by immunofluorescence at the same time points. Similar proportions of nasal epithelial cells (NE) and bronchial epithelial cells (BE) were infected with RSV. Approximately 50 to 75% (with moi 1) and 2 to 10% (with moi 0.1) of the cells were infected by 24 h; almost all the cells were RSV positive by day 4. However, BE released less infectious RSV than do NE. With moi 0.1, 10-fold less virus was released over 4 days of culture. By days 4 to 7, cytopathic effects (CPE) were maximal in all epithelial cell cultures, but CPE developed latest in BE infected with moi 0.1. AM were also productively infected with RSV, with peak virus production at day 2.(ABSTRACT TRUNCATED AT 250 WORDS)

Isolation of a cytopathic virus from weak pigs on farms with a history of swine infertility and respiratory syndrome

Severe clinical signs of swine infertility and respiratory syndrome (SIRS) of unknown cause were observed in several Minnesota swine farms between November 1990 and March 1991. Forty-five lung samples of weak pigs were collected from 13 swine farms, and virus isolation was attempted using swine alveolar macrophage (SAM) cultures. A cytopathic virus was isolated from 19 lung samples collected from 6 different farms. Four pregnant sows were infected intranasally with a tissue suspension from which virus was isolated, and 4 6-week-old pigs and 2 contact pigs were infected intranasally with 1 of the isolates. The 4 sows farrowed 12 stillborn and 32 normal pigs. Virus was recovered from 10 of 19 pigs examined. Infected 6-week-old pigs were clinically normal except for slightly elevated rectal temperatures and mild respiratory signs. No or mild interstitial pneumonic lesions were observed in inoculated pigs, but the lesion was obvious in the 2 contact pigs. Seroconversion was observed in sows and pigs as measured by indirect fluorescent antibody (IFA). Serologic identification of the isolates was carried out by IFA using reference serum prepared from an experimentally infected sow. A cytoplasmic fluorescence was observed on the SAM monolayers infected with each of the 19 different isolates. Fluorescence was also observed when the monolayers were tested with SIRS virus ATCC VR-2332-infected sow sera. Replication of the isolates was not affected in the medium containing 5-iodo-2'-deoxyuridine but was inhibited by treatment with ether. The isolates were relatively stable at 56 C and did not agglutinate with various erythrocytes tested.(ABSTRACT TRUNCATED AT 250 WORDS)

The timing of exposure of mononuclear phagocytes to recombinant interferon gamma and recombinant tumor necrosis factor alpha alters interactions with Nocardia asteroides

Nocardia asteroides modulates phagocyte function and grows within macrophages. Because interferon gamma (IFN-gamma) and tumor necrosis factor alpha (TNF-alpha) have been shown to activate macrophages to kill a variety of microorganisms, the effects of IFN-gamma and TNF-alpha on the activation of murine macrophages and human monocytes to kill nocardiae were studied. It was found that macrophages or monocytes treated with either IFN-gamma, TNF-alpha, or lipopolysaccharide as a secondary signal did not demonstrate increased microbicidal activity against N. asteroides even though these phagocytes were effective at killing the fungus Coccidioides immitis and the protozoan Toxoplasma gondii. Preincubation of phagocytes for 24 h with these compounds resulted in an enhancement of nocardial growth. In contrast, coincubation of these factors with the nocardiae and mononuclear cells during phagocytosis resulted in inhibition of nocardial growth even though this bacterium was not killed. Therefore, the specific timing of the exposure of the phagocyte in vitro to IFN-gamma or TNF-alpha has a significant effect on its ability to alter nocardial growth.

The effects of cyclosporine and dexamethasone on an alveolar macrophage cell line (NR8383)

Lung infections are a major source of morbidity and mortality in recipients of lung transplants. Prominent among the pathogens that cause pneumonias in these subjects are gram-negative bacilli, particularly Pseudomonas strains. One important reason that bacteria infect the lungs of these patients is that pulmonary defenses are impaired by the drugs used to prevent transplant rejection. Using a rat alveolar macrophage cell line (NR8383), we measured the effects of exposure (24 hr) to cyclosporine and dexamethasone (DEX) on the ability of these cells to (1) kill Pseudomonas aeruginosa (Pa); (2) produce H2O2; and (3) release tumor necrosis factor. We found that the bactericidal activity against unopsonized or opsonized Pa of NR8383 cells was unaltered by CsA (0.1, 0.5, or 1 micrograms/ml), DEX (10(-6) M), or CsA + DEX (0.5 micrograms/ml + 10(-6) M, respectively). Likewise, LPS-induced TNF release, and zymosan A and Pa-induced H2O2 production were unaltered by CsA (0.1 or 1 microgram/ml). In contrast, H2O2 production and TNF release were decreased by about 50% and 90%, respectively, by DEX exposure (10(-6) M). Thus, while DEX but not CsA decreased TNF release and H2O2 production in NR8383 cells, bactericidal activity against Pa was unaffected. One explanation for these results is that decreases in TNF or H2O2 of the magnitude we observed do not impair bactericidal activity against Pa; however, an alternative explanation is that Pa are killed by NR8383 cells through other mechanisms. Interpretation of these results must take into consideration the fact that macrophages from different species and tissues may respond differently to various stimuli.

Increased susceptibility of differentiated mononuclear phagocytes to productive infection with human immunodeficiency virus-1 (HIV-1)

Differences in susceptibility to infection of most mononuclear phagocytes with HIV-1 are not known. We investigated the relative susceptibility of autologous freshly isolated blood monocytes (MN), MN cultured in vitro to allow differentiation (CM), and alveolar macrophages (AM) from healthy subjects to productive infection with HIV-1. Cells were infected with the macrophage tropic strain HIV-1JR-FL and p24 gag antigen levels measured in supernatants by ELISA. Freshly isolated MN had negligible levels of p24 in supernatants. In contrast AM had peak p24 levels of 4145 +/- 1456 pg/ml, mean +/- SE, and CM 9216 +/- 3118. As a measure of entry and extent of reverse transcription, levels of viral DNA in infected mononuclear phagocytes were analyzed by quantitative polymerase chain reaction (PCR). The data using primers that amplify all transcripts including incompletely formed reverse transcripts indicated that differences in entry of the virus may contribute to differences in virus production observed with MN, AM, and CM. Other primer pairs that detect intermediate and full-length double-stranded DNA showed that the ability to complete reverse transcription was similar among these mononuclear phagocytes. Since the lung is a major site of opportunistic infection and noninfectious complications in HIV-1-infected individuals, this increase in productive infection with HIV-1 in AM compared with MN could contribute to the immunopathogenesis of the lung disorders seen in the acquired immunodeficiency syndrome.

Detection of simian immunodeficiency virus DNA in macrophages from infected rhesus macaques

We have examined the frequency of infection of monocyte-derived and alveolar macrophages isolated from rhesus macaques inoculated with simian immunodeficiency virus (SIVmac) utilizing a semiquantitative PCR methodology. Animals were inoculated with either pathogenic (SIVmac239) or nonpathogenic (SIVmac1A11) molecularly cloned viruses of SIVmac, or with uncloned pathogenic SIVmacBIOL. The frequency of SIV DNA in macrophages was highest early after infection and at terminal stages of disease, whereas during the asymptomatic period, SIV DNA was present at very low levels in macrophages.

Effect of macrophages and in vitro infection with parainfluenza type 3 and respiratory syncytial viruses on the mitogenic response of bovine lymphocytes

Bovine blood lymphocytes, depleted of macrophages by absorption on plasma-gelatin coated plastic flasks, followed by passage through Sephadex G-10 columns, failed to respond to pokeweed mitogen stimulation. Adherent monocytes or alveolar macrophages added to purified lymphocyte preparations at 10% or less were able to restore the transformation response. Exposure of alveolar macrophages or purified lymphocytes to 2 bovine respiratory syncytial virus strains for 24 hours substantially reduced the transformation response when mixed with uninfected lymphocytes or macrophages. Exposure of alveolar macrophages or purified lymphocytes to 2 bovine parainfluenza type 3 virus strains produced a similar reduction in activity after 48 hours. Heat inactivation of the viruses removed their inhibitory ability. Immunofluorescence studies revealed that both alveolar macrophages and lymphocytes were permissive for parainfluenza type 3 virus, whereas only a small number of alveolar macrophages and lymphocytes were infected with respiratory syncytial virus. The results suggest that both viruses are capable of adversely affecting the interaction between macrophages and lymphocytes, although the mechanisms by which this is achieved may be different.

Release of tumor necrosis factor-alpha from bovine alveolar macrophages stimulated with bovine respiratory viruses and bacterial endotoxins

The release of tumor necrosis factor-alpha (TNF-alpha) from cultured bovine alveolar macrophages (BAM) was evaluated following stimulation of BAM with bovine herpesvirus-1 (BHV-1), parainfluenza-3 (PI-3) virus, bovine respiratory syncytial virus (BRSV), Escherichia coli 0111:B4 endotoxin, Pasteurella haemolytica type 1 endotoxin, Pasteurella multocida endotoxin, and virus/endotoxin combinations. A cytotoxic assay system using Georgia bovine kidney cells as targets was used to measure TNF-alpha activity. The cytotoxic activity was neutralized by an anti-human TNF-alpha monoclonal antibody. Stimulation of BAM with 1 median tissue culture infectious dose (TCID50) of live or ultraviolet (UV)-inactivated PI-3 virus/cell resulted in release of TNF-alpha in significantly (P less than 0.05) higher amounts than sham-induced BAM. The quantities of TNF-alpha released after live or UV-inactivated BHV-1 or BRSV induction were not significantly higher than sham-induced BAM. E. coli 0111:B4, P. haemolytica type 1 and P. multocida endotoxins stimulated TNF-alpha release in a dose-dependent manner. Sequential exposure of BAM to 1 TCID50 per cell of either live BHV-1, PI-3 virus or BRSV and then 5 micrograms ml-1 of either E. coli 0111:B4, P. haemolytica type 1 or P. multocida endotoxin caused a significant (P less than 0.05) reduction in detectable TNF-alpha in seven of nine virus/endotoxin combinations tested, when compared with 5 micrograms ml-1 of endotoxin alone. Parainfluenza-3 virus/endotoxin combinations stimulated higher TNF-alpha release when compared with other virus/endotoxin combinations. Five out of six test animals had serum-neutralizing antibodies to PI-3 virus, one out of six had serum-neutralizing antibodies to BHV-1, and two out of six had serum-neutralizing antibodies to BRSV, suggesting a possible relationship between serum neutralizing antibodies and TNF-alpha release from in vitro cultivated BAM.

[Intracellular killing mechanisms of alveolar macrophages against Mycobacterium avium complex]

To clarify the intracellular killing mechanisms of alveolar macrophages against Mycobacterium avium complex, effects of cytokines on O2- and NO2- production from normal and BCG-induced alveolar macrophages were studied. Intracellular growth of M. avium complex was inhibited in the alveolar macrophages stimulated by TNF, but not IFN. Enhancement of O2- production by normal alveolar macrophages stimulated by cytokines, was associated with the inhibition of intracellular growth of M. avium complex. However, when NO2- production by the alveolar macrophages was enhanced by the stimulating of IFN or IFN+TNF, in the presence L-arginine in the culture medium, their defense activity against M. avium complex decreased.

Study of the potential involvement of pseudorabies virus in swine respiratory disease

In order to investigate the potential involvement of pseudorabies virus (PRV) in swine respiratory disease, nine week old pigs were intranasally inoculated with the PRV strain 4892. Two doses of infection were used: 10(4.5) median tissue culture infectious doses (TCID50)/pig and 10(3.5) TCID50/pig, with ten pigs per group. In the group of pigs inoculated with 10(4.5) TCID50, seven out of ten pigs died within six days after inoculation. The mortality rate in the group of pigs inoculated with the lower dose was only two out of ten and, there were several pigs in this group that showed signs of respiratory distress besides some mild nervous signs. Pseudorabies virus was isolated from various tissues collected postmortem, including alveolar macrophages. Virus localization in tissues was also detected by in situ hybridization. The histopathological examination of the respiratory tract tissues revealed a pathological process that was progressing from mild pneumonia to severe suppurative bronchopneumonia. The isolation of virus from alveolar macrophages provides support to the hypothesis that replication of PRV during the course of infection produces an impairment of the defense mechanisms in the respiratory tract.

Pneumocystis carinii induces an oxidative burst in alveolar macrophages

There is evidence that alveolar macrophages (AM) play a role in the clearing of Pneumocystis carinii from the lungs. To investigate the mechanisms involved in this process, we studied in vitro the induction of an oxidative burst by P. carinii in a cell line of macrophages (NR8383) and AM from normal rats. P. carinii was added to macrophage monolayers (10(6) cells), and the H2O2 produced after 4 h of incubation was measured. Both NR8383 macrophages and normal rat AM produced H2O2 in response to P. carinii cysts and trophozoites isolated from dexamethasone-treated rats, although the amount of H2O2 induced in AM from normal rats was larger. NR8383 macrophages bound and phagocytized both P. carinii cysts and trophozoites and produced increasing amounts of H2O2 as a dose-related response to cysts and trophozoites. Opsonization of P. carinii with normal rat serum increased H2O2 production by both types of macrophages; this enhancement was decreased, but not abolished, when the serum was first depleted of complement by heat treatment. These findings demonstrate that NR8383 macrophages and normal rat AM produce an oxidative burst in response to P. carinii and that this response is enhanced by complement.

Detection of Bordetella pertussis associated with the alveolar macrophages of children with human immunodeficiency virus infection

In humans, infection with Bordetella pertussis is considered to be localized to an epithelial surface. However, an intracellular state in cultured cells and in the macrophages of infected animals has been shown. By using indirect immunofluorescence with a monoclonal antibody, it was found that 3 of 20 bronchoalveolar lavage specimens from children with human immunodeficiency virus infection had B. pertussis associated with pulmonary alveolar macrophages. None of the cultures from the patients grew B. pertussis. The B. pertussis appeared to be intracellular.

New rapid method for the study of Pneumocystis carinii interaction with alveolar macrophages

Understanding the pathophysiology of Pneumocystis carinii infection has been limited by the availability of methods for precisely measuring the interaction of P. carinii with host cells. Here we describe a new method which allows for the rapid assessment of P. carinii binding to, and internalization by, adherent alveolar macrophages. The method is based on the detection of fluorescein-labelled P. carinii by an automated fluorescence measurement system.

Effects of antimicrobial agents on survival of Mycobacterium avium complex inside alveolar macrophages obtained from patients with human immunodeficiency virus infection

Measurements of the activities of antimicrobial agents against the Mycobacterium avium complex (MAC) usually do not take into consideration the intracellular location of the organism. A recent study using mouse macrophage continuous cell line J774 (D. M. Yajko, P.S. Nassos, C. A. Sanders, and W. K. Hadley, Am. Rev. Respir. Dis. 140: 1198-1203, 1989) showed that certain combinations of antimicrobial agents are able to kill MAC inside macrophages and suggested that the J774 cell line could be used as a model for screening of drugs for intracellular activity against MAC. As a test of the validity of this model, alveolar macrophages were isolated from the bronchoalveolar lavages of 36 patients who had AIDS or an AIDS-related condition or were considered to be at risk for AIDS. The macrophages were infected with MAC and then treated with a drug or drug combination for 48 to 72 h. Survival of MAC was measured over time in drug-treated macrophages and untreated control macrophages. No single drug or two-drug combination that was tested was able to cause a decrease in the survival of every one of the MAC strains used in the study. However, several three-drug combinations that had been shown to cause a decrease in survival of all MAC strains inside J774 cells also caused a decrease in survival of all MAC strains inside alveolar macrophages from patients. The good agreement between these results and those obtained previously with J774 cells gives further evidence of the usefulness of the simpler J774 model for screening of drugs for intracellular activity against MAC.

A study on the mechanism of antibody-dependent enhancement of feline infectious peritonitis virus infection in feline macrophages by monoclonal antibodies

Enhancement of feline infectious peritonitis virus (FIPV) infection of feline macrophages was studied using monoclonal antibodies (MAbs) to the FIPV strain 79-1146. Adherent cells recovered from the feline lung and peritoneal cavity phagocytosed fixed red blood cells, and formed Fc-mediated rosettes. Enhancement of virus infection by MAb was investigated by inoculating alveolar macrophages with a mixtures of viral suspension and MAb, and examining the cells for intracellular viral antigen by the immunofluorescence assay and the amount of infectious virus in the supernatant fluid after incubation. The replication of FIPV in macrophages was enhanced by non-neutralizing MAbs recognizing peplomer protein (S) and transmembrane protein (M) of the virus. Even among the MAbs having the ability to neutralize FIPV strain 79-1146, some reversely enhanced virus infection when they were diluted. The enhancement was suppressed by pretreatment of the MAb with protein A. The enhancement was reduced by the use of F(ab')2 fragment of MAb. These results demonstrated antibody-dependent enhancement (ADE) of FIPV infection in macrophage. The replication of FIPV 79-1146 strain in macrophages from FIPV antibody-positive cats was more enhanced than in those from antibody-negative cats.