The effect of decomplementation on the infectious course of Sendai virus in mice

The course of intranasal infection of Sendai virus in CBA and DBA mice was investigated in animals decomplemented with purified cobra venom factor. The mice were decomplemented either immediately before inoculation or at 4 days postinfection. Depletion of complement after the infection had been established had no apparent effect on the course of the viral infection in the two strains of mice. In contrast, both strains of mice were protected completely from the lethal effects of an infectious dose of 1 LD50 of virus when the serum C3 levels were depressed by more than 80% during the early stages of infection. The symptoms of morbidity were less pronounced in these animals and there was a delay in the production of hemagglutination-inhibiting antibody. There was no apparent effect on the growth of the virus in lung tissue. The results suggest that the complement system plays a significant pathogenic role during the course of Sendai virus infections in CBA and DBA mice.     

Characterization of genetic changes occurring in attenuated poliovirus 2 during persistent infection in mouse central nervous systems.

Genomic changes occurring in the attenuated W-2 strain of poliovirus 2 during persistent infection of the central nervous system of immunosuppressed mice were analyzed. The RNase T1 oligonucleotide fingerprints of 34 different viruses, isolated from the brains and spinal cords of paralyzed and nonparalyzed mice during a 105-day period, were used to quantitate and compare the mutations occurring in each isolate. Although mice were inoculated with plaque-purified virus, genetically distinct viruses were recovered from the central nervous system. The number of oligonucleotide changes occurring in isolates from paralyzed mice generally was greater than that observed in isolates from nonparalyzed mice. However, differences in the extent of mutation in isolates from the two groups of mice did not appear to be related to the level of virus replication. In paralyzed mice, the number of oligonucleotide changes on average was greater in viruses isolated during the first 60 days of the infection than in the last 45 days. The number of oligonucleotide changes was essentially constant throughout the infection, however, in viruses isolated from the brains of nonparalyzed mice. In addition, several specific oligonucleotide changes were found only in viruses isolated from paralyzed animals.     

Running wheel size influences circadian rhythm period and its phase shift in mice

Running wheels are widely used in studies on biological rhythms. In mice wheel diameters have ranged from 11 cm to 23 cm. We provided mice with running wheels of two different sizes: 15 cm diameter and 11 cm diameter. The amount of running in the 12-h light:12-h dark condition and the endogenous period of wheel running in constant darkness was determined over 40 days. On the 1st day in constant darkness all animals were exposed to a 15-min light pulse at circadian time 13. The animals in the small wheel ran significantly less both in 12 h light: 12 h dark and constant darkness, and showed a longer endogenous period in constant darkness compared to animals in the large wheel. Moreover, after the light pulse at circadian time 13, mice in the small wheel showed a significantly smaller phase delay in running wheel activity than mice in the larger wheels. The data suggest that the magnitude of a photic phase shift depends on the amount and timing of activity the animals display in relation to this stimulus. It can be concluded that technical features of the running wheel can influence the circadian period of wheel running.     

Lipopolysaccharide-induced injury is more pronounced in fetal transgenic ErbB4-deleted lungs

Pulmonary ErbB4 deletion leads to a delay in fetal lung development, alveolar simplification, and lung function disturbances in adult mice. We generated a model of intrauterine infection in ErbB4 transgenic mice to study the additive effects of antenatal LPS administration and ErbB4 deletion during fetal lung development. Pregnant mice were treated intra-amniotically with an LPS dose of 4 μg at E17 of gestation. Lungs were analyzed 24 h later. A significant influx of inflammatory cells was seen in all LPS-treated lungs. In heterozygote control lungs, LPS treatment resulted in a delay of lung morphogenesis characterized by a significant increase in the fraction of mesenchyme, a decrease in gas exchange area, and disorganization of elastic fibers. Surfactant protein (Sftp)b and Sftpc were upregulated, but mRNA of Sftpb and Sftpc was downregulated compared with non-LPS-treated controls. The mRNA of Sftpa1 and Sftpd was upregulated. In ErbB4-deleted lungs, the LPS effects were more pronounced, resulting in a further delay in morphological development, a more pronounced inflammation in the parenchyma, and a significant higher increase in all Sftp. The effect on Sftpb and Sftpc mRNA was somewhat different, resulting in a significant increase. These results imply a major role of ErbB4 in LPS-induced signaling in structural and functional lung development.     

Rabies Virus Infection Induces Type I Interferon Production in an IPS-1 Dependent Manner While Dendritic Cell Activation Relies on IFNAR Signaling

As with many viruses, rabies virus (RABV) infection induces type I interferon (IFN) production within the infected host cells. However, RABV has evolved mechanisms by which to inhibit IFN production in order to sustain infection. Here we show that RABV infection of dendritic cells (DC) induces potent type I IFN production and DC activation. Although DCs are infected by RABV, the viral replication is highly suppressed in DCs, rendering the infection non-productive. We exploited this finding in bone marrow derived DCs (BMDC) in order to differentiate which pattern recognition receptor(s) (PRR) is responsible for inducing type I IFN following infection with RABV. Our results indicate that BMDC activation and type I IFN production following a RABV infection is independent of TLR signaling. However, IPS-1 is essential for both BMDC activation and IFN production. Interestingly, we see that the BMDC activation is primarily due to signaling through the IFNAR and only marginally induced by the initial infection. To further identify the receptor recognizing RABV infection, we next analyzed BMDC from Mda-5−/− and RIG-I−/− mice. In the absence of either receptor, there is a significant decrease in BMDC activation at 12h post infection. However, only RIG-I−/− cells exhibit a delay in type I IFN production. In order to determine the role that IPS-1 plays in vivo, we infected mice with pathogenic RABV. We see that IPS-1−/− mice are more susceptible to infection than IPS-1+/+ mice and have a significantly increased incident of limb paralysis.     

The Role of Galectin-1 and Galectin-3 in the Mucosal Immune Response to Citrobacter rodentium Infection

Despite their abundance at gastrointestinal sites, little is known about the role of galectins in gut immune responses. We have therefore investigated the Citrobacter rodentium model of colonic infection and inflammation in Galectin-1 or Galectin-3 null mice. Gal-3 null mice showed a slight delay in colonisation after inoculation with C. rodentium and a slight delay in resolution of infection, associated with delayed T cell, macrophage and dendritic cell infiltration into the gut mucosa. However, Gal-1 null mice also demonstrated reduced T cell and macrophage responses to infection. Despite the reduced T cell and macrophage response in Gal-1 null mice, there was no effect on C. rodentium infection kinetics and pathology. Overall, Gal-1 and Gal-3 play only a minor role in immunity to a gut bacterial pathogen.     

Passive transfer of antibodies protects immunocompetent and imunodeficient mice against lethal Ebola virus infection without complete inhibition of viral replication

Ebola hemorrhagic fever is a severe, usually fatal illness caused by Ebola virus, a member of the filovirus family. The use of nonhomologous immune serum in animal studies and blood from survivors in two anecdotal reports of Ebola hemorrhagic fever in humans has shown promise, but the efficacy of these treatments has not been demonstrated definitively. We have evaluated the protective efficacy of polyclonal immune serum in a mouse model of Ebola virus infection. Our results demonstrate that mice infected subcutaneously with live Ebola virus survive infection and generate high levels of anti-Ebola virus immunoglobulin G (IgG). Passive transfer of immune serum from these mice before challenge protected upto 100% of naive mice against lethal Ebola virus infection. Protection correlated with the level of anti-Ebola virus IgG titers, and passive treatment with high-titer antiserum was associated with a delay in the peak of viral replication. Transfer of immune serum to SCID mice resulted in 100% survival after lethal challenge with Ebola virus, indicating that antibodies alone can protect from lethal disease. Thus antibodies suppress or delay viral growth, provide protection against lethal Ebola virus infection, and may not require participation of other immune components for protection.     

Cellular elements in the resistance to candida infection in mice. I. Contribution of T lymphocytes and phagocytes at various stages of infection.

Live organisms (cfu) of Candida albicans per organ were counted 1 hr and 1 to 20 days after an intravenous inoculation into various groups of mice which had distinct levels of immunologic or non-immunologic defense mechanisms. a) The number of cfu in the liver decreased progressively in normal mice, but those in the kidney maintained a constant level during the observation period. b) The number of cfu in the liver decreased progressively also in nude mice. In their kidneys, however, cfu increased progressively at a late stage of infection. c) In lethally irradiated AKR of nude mice in which phagocyte functions were severely depressed, the number of cfu increased progressively in both liver and kidney from the initial stage of infection. d) In immunized AKR mice, growth of C. albicans was suppressed at late stages of infection. Such protective immunity could be transferred partly with immune lymphoid cells but not with hyperimmune serum in the experimental system employed. In protection against candida infection, non-immune phagocytosis and T cell-mediated immunity appear to be required at the early and late stages of infection, respectively.     

Characterization of Cells Infiltrating the Lungs of X-Irradiated and Nude Mice after Influenza Virus Infection

After X-irradiated and nonirradiated mice (C3H/He) as well as athymic nude mice and haired littermates (BALB/c) were infected with influenza A virus (Kumamoto strain, H2N2), they were examined for survival period, the development of consolidation in the lungs and the characteristics of the cells infiltrating the lung tissues. In two different T-cell deficient groups, there was a definite delay in the development of consolidation compared with their respective controls and this was reflected in prolonged survival periods: 5 days longer for irradiated mice and 6 days longer for nude mice. In both T-cell deficient and normal groups, about 70% of the cells obtained from consolidated lung tissues after virus infection were found to be small lymphoid cells and there were no morphological differences between the T-cell deficient and normal groups. None of these small lymphoid cells from the peripheral blood or the spleens of T-cell deficient mice responded to concanavalin A. In the lungs of both X-irradiated mice and nude mice, however, a definite increase in cells having natural killer activity was found at the late stages of the influenza infection, suggesting their participation in the development of consolidation.     

Th cell-deficient mice control influenza virus infection more effectively than Th- and B cell-deficient mice: evidence for a Th-independent contribution by B cells to virus clearance

The notion that MHC class I- restricted CD8+ T (Tc) cells are capable of resolving autonomously infections with influenza virus is based largely on studies testing virus strains of low pathogenicity in CD4+ T (Th) cell-deficient/depleted mice. To test whether this holds also for pathogenic strains and to exclude possible contributions by B cells, we analyzed PR8 infection in Th cell-depleted B cell-deficient (muMT) mice. These mice, termed muMT (-CD4), showed 80% mortality after infection with a small dose of PR8, which resulted in insignificant mortality in intact or Th cell-depleted BALB/c mice. Infection of muMT(-CD4) mice with a virus of low pathogenicity was resolved without mortality, but, compared with intact BALB/c mice, with delay of approximately 5 and approximately 20 days from lung and nose, respectively. The low mortality of Th cell-depleted BALB/c mice suggested that B cells contributed to recovery in a Th-independent manner. This was verified by showing that transfer of 8-10 million T cell-depleted naive spleen cells into muMT(-CD4) mice 1 day before infection reduced mortality to 0%. The mechanism by which B cells improved recovery was investigated. We found no evidence that they operated by improving the lung-associated Tc response. Treatment of infected muMT(-CD4) mice with normal mouse serum spiked with hemagglutinin-specific IgM did not reduce mortality. Taken together, the data show that 1) the Tc response is capable of resolving autonomously (in conjunction with innate defenses) influenza virus infections, although with substantial delay compared with intact mice, and 2) B cells can contribute to recovery by a Th-independent mechanism.     

Kinetic characterization of baculovirus-induced cell death in insect cell cultures

The death process of baculovirus-infected insect cells was divided into two phases: a constant viability (or delay) phase characterized by a delay time (t(d)) and a first-order death phase characterized by a half-life (t(1/2)). These two parameters were used in conjunction with the n-target theory to classify the kinetics of cell death under various conditions, including different multiplicity of infection (MOI), host cell lines, virus types, incubation volumes, cell density and extracellular L(+)-lactate and ammonium concentrations. Two groups of kinetic effects were found: one characterized by a constant number of hypothetical targets and the other by decreased numbers of hypothetical targets. The first group includes effects such as MOI, virus types, and host cell lines. The second includes the effects of environmental perturbations, such as incubation volume, cell density, and extracellular concentrations of L(+)-lactate and ammonium. Although the underlying mechanisms of these effects are as yet unknown, the death kinetics of infected cells significantly affects the recombinant protein production. In general, foreign protein production does not correlate with the cell life after infection (c) 1993 John Wiley & Sons, Inc.     

Gamma interferon is not essential for recovery from acute infection with murine gammaherpesvirus 68.

Murine gammaherpesvirus 68 (MHV-68) when administered intranasally induces high levels of gamma interferon (IFN-gamma) in the lymphoid tissues of infected mice. In order to investigate the role of this cytokine in the immune response to MHV-68, mice which were congenitally deficient in the IFN-gamma gene (IFN-gamma knockout mice) were infected with the virus. Comparison of the courses of the disease in wild-type control and IFN-gamma knockout mice revealed surprisingly little difference. Both groups of mice had cleared infectious virus from the lungs 15 days after infection, although there did appear to be a slight delay in viral clearance in the IFN-gamma knockout mice. In addition, after the initial phase of viral clearance, the lungs of both groups remained clear of replicating virus throughout the course of the experiment, which concluded 34 days after infection. Consistent with these observations, cytotoxic T-cell activities were similar in the two groups of mice. Levels of latent virus were comparable in wild-type and knockout mice over the time course studied. Furthermore, analysis of the numbers, types, and activation status of cells in the lungs, lymph nodes, and spleens of control and knockout mice revealed no striking difference. This suggests that IFN-gamma is not essential for regulating the cell recruitment or proliferation that normally occurs during this viral infection. Apart from the expected lack of IFN-gamma, cytokine profiles were not dramatically altered in IFN-gamma knockout mice, demonstrating that IFN-gamma did not suppress the proliferation or differentiation of Th2 cells during MHV-68 infection. These observations indicate that IFN-gamma plays a nonessential or redundant role in the control of acute infection with MHV-68.     

Mathematical characterization of insect cell (Sf-9) death in suspended culture

The effect of baculovirus infection on cell death in suspended cultures was characterized based on work by Wu et al. (1993) Biotech. Bioeng. 41: 104–110 and Wu et al. (1994) Biotechnol. Prog. 10: 55–59. The post infection time can be separated into a constant viability phase characterized by a time delay, td, and a rapid death phase, which is characterized by a specific death rate constant, k. Results indicated that the characteristic time delay decreased with increased multiplicity on infection (MOI). Further, there was only a weak correlation between specific death rate and MOI, for the range of MOI tested. Cell infection and death rates were consistent with a more evenly distributed infection process likely found in suspension cultures.     

Exercise Improves Host Response to Influenza Viral Infection in Obese and Non-Obese Mice through Different Mechanisms

Obesity has been associated with greater severity of influenza virus infection and impaired host defense. Exercise may confer health benefits even when weight loss is not achieved, but it has not been determined if regular exercise improves immune defense against influenza A virus (IAV) in the obese condition. In this study, diet-induced obese mice and lean control mice exercised for eight weeks followed by influenza viral infection. Exercise reduced disease severity in both obese and non-obese mice, but the mechanisms differed. Exercise reversed the obesity-associated delay in bronchoalveolar-lavage (BAL) cell infiltration, restored BAL cytokine and chemokine production, and increased ciliary beat frequency and IFNα-related gene expression. In non-obese mice, exercise treatment reduced lung viral load, increased Type-I-IFN-related gene expression early during infection, but reduced BAL inflammatory cytokines and chemokines. In both obese and non-obese mice, exercise increased serum anti-influenza virus specific IgG2c antibody, increased CD8+ T cell percentage in BAL, and reduced TNFα by influenza viral NP-peptide-responding CD8+ T cells. Overall, the results suggest that exercise “restores” the immune response of obese mice to a phenotype similar to non-obese mice by improving the delay in immune activation. In contrast, in non-obese mice exercise treatment results in an early reduction in lung viral load and limited inflammatory response.     

Salmonellosis in mice infected with Mycobacterium tuberculosis BCG. I. Role of endotoxin in infection

In agreement with previous observations, mice dying of salmonellosis were found to have a relatively constant number of Salmonella cells in their carcasses (ca. 5 x 10(9)). This number was not the result of bacterial overgrowth in moribund animals and therefore appears to be related to lethality. Similar numbers of salmonellae were recovered from the carcasses of infected mice which had previously been rendered hyperreactive to endotoxin either by infection with M. tuberculosis BCG or by adrenalectomy. In BCG mice, desensitization to endotoxin did not occur during the infection and, therefore, at death these mice contained a number of bacteria which would be equivalent to 1,000 ld(50) of endotoxin. Although the number of bacteria recovered from normal mice is roughly equivalent to a lethal quantity of endotoxin, this is obviously not the case in hyperreactive mice. Therefore, the relationship between lethality and 5 x 10(9) salmonellae cannot be explained by their endotoxin content. Nevertheless, when hyperreactive BCG mice are challenged parenterally with Salmonella, the endotoxin content of the inoculum may markedly influence the course of the infection.     

Study of Dengue Virus Infection in SCID Mice Engrafted with Human K562 Cells

Here we report that severe combined immunodeficient (SCID) mice engrafted with human K562 cells (K562-SCID mice) can be used as an animal model to study dengue virus (DEN) infection. After intratumor injection into K562 cell masses of PL046, a Taiwanese DEN-2 human isolate, the K562-SCID mice showed neurological signs of paralysis and died at approximately 2 weeks postinfection. In addition to being detected in the tumor masses, high virus titers were detected in the peripheral blood and the brain tissues, indicating that DEN had replicated in the infected K562-SCID mice. In contrast, the SCID mice were resistant to DEN infection and the mock-infected K562-SCID mice survived for over 3 months. These data illustrate that DEN infection contributed directly to the deaths of the infected K562-SCID mice. Other serotypes of DEN were also used to infect the K562-SCID mice, and the mortality rates of the infected mice varied with different challenge strains, suggesting the existence of diverse degrees of virulence among DENs. To determine whether a neutralizing antibody against DEN in vitro was also protective in vivo, the K562-SCID mice were challenged with DEN-2 and received antibody administration at the same time or 1 day earlier. Our results revealed that the antibody-treated mice exhibited a reduction in mortality and a delay of paralysis onset after DEN infection. In contrast to K562-SCID, the persistently DEN-infected K562 cells generated in vitro invariably failed to be implanted in the mice. It seems that in the early stage of implantation, a gamma interferon activated, nitric oxide-mediated anti-DEN effect might play a role in the innate immunity against DEN-infected cells. The system described herein offers an opportunity to explore DEN replication in vivo and to test various antiviral protocols in infected hosts.     

The benefits of using selenium in the treatment of Chagas disease: prevention of right ventricle chamber dilatation and reversion of Trypanosoma cruzi-induced acute and chronic cardiomyopathy in mice

Cardiac damage is a frequent manifestation of Chagas disease, which is caused by the parasite Trypanosoma cruzi. Selenium (Se) is an essential micronutrient, the deficiency of which has been implicated in the development of cardiomyopathy. Our group has previously demonstrated that Se supplementation prevents myocardial damage during acute T. cruzi infection in mice. In this study, we analyzed the effect of Se treatment in cases of T. cruzi infection using prevention and reversion schemes. In the Se prevention scheme, mice were given Se supplements (2 ppm) starting two weeks prior to inoculation with T. cruzi(Brazil strain) and continuing until 120 days post-infection (dpi). In the Se reversion scheme, mice were treated with Se (4 ppm) for 100 days, starting at 160 dpi. Dilatation of the right ventricle was observed in the infected control group at both phases of T. cruzi infection, but it was not observed in the infected group that received Se treatment. Surviving infected mice that were submitted to the Se reversion scheme presented normal P wave values and reduced inflammation of the pericardium. These data indicate that Se treatment prevents right ventricular chamber increase and thus can be proposed as an adjuvant therapy for cardiac alterations already established by T. cruzi infection.     

Dynamics of an HBV model with diffusion and delay

In this paper we model and analyze the hepatitis B virus (HBV) infection in a diffusion model confined to a finite domain, induced by intracellular time delay between infection of a cell and production of new virus particles. The equilibrium solutions are obtained and the stability is analyzed if the space is assumed as homogeneous. When the space is inhomogeneous, the effects of diffusion and intracellular time delay are obtained by computer simulations.     

Igh-C allotype-linked control of anti-DNA production and clonotype expression in mice infected with Plasmodium yoelii

The infection of nonlethal strain of Plasmodium yoelii induces the formation of IgG anti-DNA antibodies as a result of polyclonal B cell activation. By using various nonautoimmune strains of mice including H-2 or Igh congenic or recombinant mice, the levels and clonotypes of anti-DNA antibodies elicited by the malaria infection were analyzed in relation to the expression of the MHC or Igh gene. Our results showed there were little, if any, differences in serum anti-DNA levels and their clonotypes among B10 and B6 H-2 congenic mice. In contrast, malaria-induced IgG anti-DNA responses markedly differed quantitatively and clonotypically between murine strains bearing the Ighb allotype and those bearing the Igha, Ighj, Ighd, or Ighn allotype. The latter group of mice produced approximately 5 to 10 times more IgG anti-DNA antibodies than the former group of mice. Clonotypically, mice bearing the Ighb allotype developed high alkaline anti-DNA antibodies of pH 8.0 to 8.5, whereas non-Ighb mice failed to express such alkaline anti-DNA spectrotypes, and exhibited more neutral spectrotypes (pH 7.0 to 8.0). Studies on the Igh recombinant mice indicated that the observed quantitative and clonotypical differences in IgG anti-DNA production was not associated with the variable region, but with the constant region of the Igh gene complex. Our results have suggested that IgG anti-DNA responses occurring as a result of polyclonal B cell activation during the course of malaria infection markedly differs quantitatively and clonotypically among murine strains and appear to be controlled at least in part by the Igh-C gene or gene(s) closely linked to it.