Experimental Andes Virus Infection in Deer Mice: Characteristics of Infection and Clearance in a Heterologous Rodent Host

New World hantaviruses can cause hantavirus cardiopulmonary syndrome with high mortality in humans. Distinct virus species are hosted by specific rodent reservoirs, which also serve as the vectors. Although regional spillover has been documented, it is unknown whether rodent reservoirs are competent for infection by hantaviruses that are geographically separated, and known to have related, but distinct rodent reservoir hosts. We show that Andes virus (ANDV) of South America, carried by the long tailed pygmy rice rat (Oligoryzomys longicaudatus), infects and replicates in vitro and in vivo in the deer mouse (Peromyscus maniculatus), the reservoir host of Sin Nombre virus (SNV), found in North America. In experimentally infected deer mice, viral RNA was detected in the blood, lung, heart and spleen, but virus was cleared by 56 days post inoculation (dpi). All of the inoculated deer mice mounted a humoral immune response by 14 dpi, and produced measurable amounts of neutralizing antibodies by 21 dpi. An up-regulation of Ccl3, Ccl4, Ccl5, and Tgfb, a strong CD4⁺ T-cell response, and down-regulation of Il17, Il21 and Il23 occurred during infection. Infection was transient with an absence of clinical signs or histopathological changes. This is the first evidence that ANDV asymptomatically infects, and is immunogenic in deer mice, a non-natural host species of ANDV. Comparing the immune response in this model to that of the immune response in the natural hosts upon infection with their co-adapted hantaviruses may help clarify the mechanisms governing persistent infection in the natural hosts of hantaviruses.     

Experimental Myocarditis Induced in Mice by Infection with Influenza A2 Virus

A mouse model was established for the study of acute myocarditis that occurs during influenza infection. Challenge with more than 10 LD₅₀ of mouse-adapted influenza A₂ virus (H₂N₂) induced myocarditis macroscopically discernible as white, irregularly shaped lesions which were shown by histological examination to consist of necrotic myofibers surrounded by infiltrating mononuclear inflammatory cells. After challenge with 10 LD₅₀ of the virus, macroscopic myocarditis was found to advance in a progressive manner up to the 7th day, while the virus titer in the heart reached its peak on the 2nd day and began to decrease on the 5th day of infection. However, development of myocarditis was significantly suppressed in mice which were irradiated with 400 R of X-rays before infection. In addition, myocarditis did not develop in congenitally athymic nude mice. These data indicate that myocarditis was not brought about by viral action directly, but that it was mediated by some function of the host against viral in-vasion, which was abolished by X-irradiation. The data also suggest that T cells played a key role in the development of myocarditis.     

The Impact of Hepatitis A Virus Infection on Hepatitis C Virus Infection: A Competitive Exclusion Hypothesis

We address the observation that, in some cases, patients infected with the hepatitis C virus (HCV) are cleared of HCV when super-infected with the hepatitis A virus (HAV). We hypothesise that this phenomenon can be explained by the competitive exclusion principle, including the action of the immune system, and show that the inclusion of the immune system explains both the elimination of one virus and the co-existence of both infections for a certain range of parameters. We discuss the potential clinical implications of our findings.     

Immune-Mediated Competition in Rodent Malaria Is Most Likely Caused by Induced Changes in Innate Immune Clearance of Merozoites

Malarial infections are often genetically diverse, leading to competitive interactions between parasites. A quantitative understanding of the competition between strains is essential to understand a wide range of issues, including the evolution of virulence and drug resistance. In this study, we use dynamical-model based Bayesian inference to investigate the cause of competitive suppression of an avirulent clone of Plasmodium chabaudi (AS) by a virulent clone (AJ) in immuno-deficient and competent mice. We test whether competitive suppression is caused by clone-specific differences in one or more of the following processes: adaptive immune clearance of merozoites and parasitised red blood cells (RBCs), background loss of merozoites and parasitised RBCs, RBC age preference, RBC infection rate, burst size, and within-RBC interference. These processes were parameterised in dynamical mathematical models and fitted to experimental data. We found that just one parameter , the ratio of background loss rate of merozoites to invasion rate of mature RBCs, needed to be clone-specific to predict the data. Interestingly, was found to be the same for both clones in single-clone infections, but different between the clones in mixed infections. The size of this difference was largest in immuno-competent mice and smallest in immuno-deficient mice. This explains why competitive suppression was alleviated in immuno-deficient mice. We found that competitive suppression acts early in infection, even before the day of peak parasitaemia. These results lead us to argue that the innate immune response clearing merozoites is the most likely, but not necessarily the only, mediator of competitive interactions between virulent and avirulent clones. Moreover, in mixed infections we predict there to be an interaction between the clones and the innate immune response which induces changes in the strength of its clearance of merozoites. What this interaction is unknown, but future refinement of the model, challenged with other datasets, may lead to its discovery.     

Acute SIV Infection in Sooty Mangabey Monkeys Is Characterized by Rapid Virus Clearance from Lymph Nodes and Absence of Productive Infection in Germinal Centers

Lymphoid tissue immunopathology is a characteristic feature of chronic HIV/SIV infection in AIDS-susceptible species, but is absent in SIV-infected natural hosts. To investigate factors contributing to this difference, we compared germinal center development and SIV RNA distribution in peripheral lymph nodes during primary SIV infection of the natural host sooty mangabey and the non-natural host pig-tailed macaque. Although SIV-infected cells were detected in the lymph node of both species at two weeks post infection, they were confined to the lymph node paracortex in immune-competent mangabeys but were seen in both the paracortex and the germinal center of SIV-infected macaques. By six weeks post infection, SIV-infected cells were no longer detected in the lymph node of sooty mangabeys. The difference in localization and rate of disappearance of SIV-infected cells between the two species was associated with trapping of cell-free virus on follicular dendritic cells and higher numbers of germinal center CD4⁺ T lymphocytes in macaques post SIV infection. Our data suggests that fundamental differences in the germinal center microenvironment prevent productive SIV infection within the lymph node germinal centers of natural hosts contributing to sustained immune competency.     

Effects of Reticuloendotheliosis Virus Infection on Cytokine Production in SPF Chickens

Infection with reticuloendotheliosis virus (REV), a gammaretrovirus in the Retroviridae family, can result in immunosuppression and subsequent increased susceptibility to secondary infections. The effects of REV infection on expression of mRNA for cytokine genes in chickens have not been completely elucidated. In this study, using multiplex branched DNA (bDNA) technology, we identified molecular mediators that participated in the regulation of the immune response during REV infection in chickens. Cytokine and chemokine mRNA expression levels were evaluated in the peripheral blood mononuclear cells (PBMCs). Expression levels of interleukin (IL)-4, IL-10, IL-13 and tumor necrosis factor (TNF)-α were significantly up-regulated while interferon (IFN)-α, IFN-β, IFN-γ, IL-1β，IL-2, IL-3, IL-15, IL-17F, IL-18 and colony-stimulating factor (CSF)-1 were markedly decreased in PBMCs at all stages of infection. Compared with controls, REV infected chickens showed greater expression levels of IL-8 in PBMCs 21 and 28 days post infection. In addition, REV regulates host immunity as a suppressor of T cell proliferative responses. The results in this study will help us to understand the host immune response to virus pathogens.     

Role that each NKG2A immunoreceptor tyrosine-based inhibitory motif plays in mediating the human CD94/NKG2A inhibitory signal

The human NKG2A chain of the CD94/NKG2A receptor contains two immunoreceptor Tyr-based inhibitory motifs (ITIMs) in its cytoplasmic tail. To determine the relative importance of membrane-distal (residues 6-11) and membrane-proximal (residues 38-43) ITIMs in mediating the inhibitory signal, we made site-directed mutants of NKG2A at the Y (Y8F, Y40F, Y8F/Y40F) and the residues two positions N-terminal (Y-2) of Y (V6A, I38A, V6A/I38A) in each motif. Wild-type (wt) and mutated NKG2A were then cotransfected with CD94 into rat basophilic leukemia 2H3 cells. Immunochemical analyses after pervanadate treatment showed that each of the mutant molecules could be phosphorylated to expected levels relative to wt NKG2A and that all the mutations significantly reduced the avidity of SH2 domain-bearing tyrosine phosphatase-1 for NKG2A. Confocal microscopy was used to determine whether SH2 domain-bearing tyrosine phosphatase-1 and CD94/NKG2A colocalized intracellularly after receptor ligation. Only the Y8F/Y40F and Y8F mutant NKG2A molecules failed to show a dramatic colocalization. In agreement with this result, the Y8F/Y40F mutant was unable to inhibit FcepsilonRI-mediated serotonin release and the Y8F mutant was relatively ineffective compared with wt NKG2A. In contrast, the Y40F mutant was 70% as effective as wt in mediating inhibition, and the Y-2 mutations did not remarkably affect inhibitory function. These results show that, like KIR, both NKG2A ITIMs are required for mediating the maximal inhibitory signal, but opposite to KIR, the membrane-distal ITIM is of primary importance rather than the membrane-proximal ITIM. This probably reflects the opposite orientation of the ITIMs in type II vs type I proteins.     

肥胖可能与病毒感染有关

随着生活水平的提高,肥胖已呈现为全球性问题.当今已将肥胖与艾滋病、癌症并称为21世纪威胁人类健康的三大疾病.而其中肥胖症则是人类健康的最大威胁.当前人们普遍认为肥胖是由于遗传、过食、运动不足、代谢异常、内分泌异常、脑疾患等因素引起.但是这些均不能完满地解释肥胖的成因.为此,美国科学家Dhurandhar等提出了一种新的解释.他们认为,肥胖可能与病毒感染有关[1].并已研究发现了第1株可引起动物肥胖的人腺病毒血清36型(adenouirus Ad-36),这是迄今所发现的第1株与肥胖有关的人腺病毒[2].证据表明,该病毒感染在动物肥胖发病中起着重要作用[2~5].是否能导致人类肥胖尚不得而知.但是,有关肥胖的病毒发现使肥胖成因的研究有了新的思考,为人类进一步了解肥胖问题的根源,以及肥胖的防治开辟了新的领域,展现出新的希望.至于病毒导致动物肥胖的具体机理以及人类肥胖是否与病毒感染有关至今尚不明确,有待深入研究.     

Local Blockade of Epithelial PDL-1 in the Airways Enhances T Cell Function and Viral Clearance during Influenza Virus Infection

In order to maintain the gas exchange function of the lung following influenza virus infection, a delicate orchestration of positive and negative regulatory pathways must be maintained to attain viral eradication while minimizing local inflammation. The programmed death receptor 1 ligand/programmed death receptor 1 (PDL-1/PD-1) pathway plays an important immunoregulatory role, particularly in the context of T cell function. Here, we have shown that influenza virus infection of primary airway epithelial cells strongly enhances PDL-1 expression and does so in an alpha interferon receptor (IFNAR) signaling-dependent manner. PD-1 is expressed primarily on effector T cells in the lung, compared to effector memory and central memory cells, and shortly after influenza virus infection, an increased number of PD-1⁺ T cells are recruited to the airways. Using in vitro cocultures of airway epithelial cells and T cells and in vivo models of influenza virus infection, we have demonstrated that blockade of airway epithelial PDL-1 improves CD8 T cell function, defined by increased production of gamma interferon (IFN-γ) and granzyme B and expression of CD107ab. Furthermore, PDL-1 blockade in the airways served to accelerate influenza virus clearance and enhance infection recovery. Our findings suggest that local manipulation of the PDL-1/PD-1 axis in the airways may represent a therapeutic alternative during acute influenza virus infection.     

Preexisting Infection with Human T-Cell Lymphotropic Virus Type 2 neither Exacerbates nor Attenuates Simian Immunodeficiency Virus SIVmac251 Infection in Macaques

Coinfection with human T-cell lymphotropic virus type 2 (HTLV-2) and human immunodeficiency virus type 1 (HIV-1) has been reported to have either a slowed disease course or to have no effect on progression to AIDS. In this study, we generated a coinfection animal model and investigated whether HTLV-2 could persistently infect macaques, induce a T-cell response, and impact simian immunodeficiency virus SIV_mac251-induced disease. We found that inoculation of irradiated HTLV-2-infected T cells into Indian rhesus macaques elicited humoral and T-cell responses to HTLV-2 antigens at both systemic and mucosal sites. Low levels of HTLV-2 provirus DNA were detected in the blood, lymphoid tissues, and gastrointestinal tracts of infected animals. Exposure of HTLV-2-infected or naïve macaques to SIV_mac251 demonstrated comparable levels of SIV_mac251 viral replication, similar rates of mucosal and peripheral CD4⁺ T-cell loss, and increased T-cell proliferation. Additionally, neither the magnitude nor the functional capacity of the SIV-specific T-cell-mediated immune response was different in HTLV-2/SIV_mac251 coinfected animals versus SIV_mac251 singly infected controls. Thus, HTLV-2 targets mucosal sites, persists, and importantly does not exacerbate SIV_mac251 infection. These data provide the impetus for the development of an attenuated HTLV-2-based vectored vaccine for HIV-1; this approach could elicit persistent mucosal immunity that may prevent HIV-1/SIV_mac251 infection.Human T-cell lymphotropic virus type 2 (HTLV-2) was discovered in 1982 and recognized as the second human retrovirus found (29). HTLV-2 is closely related to the first human retrovirus discovered, HTLV-1 (49, 50)_, a pathogenic virus that causes adult T-cell leukemia/lymphoma (ATLL) and an inflammatory neurologic disorder called HTLV-1-associated myelopathy or tropical spastic paraparesis (HAM/TSP) (22, 45).HTLV-2 is prevalent in Amerindian populations of North and South America and in Africa (57). The prevalence of HTLV-2 is generally low; however, in the past 20 years, an epidemic of HTLV-2 infection has occurred among intravenous drug users (8, 24, 54, 57). HTLV-2 establishes a lifelong infection and replicates at low levels in most infected individuals. While anecdotal cases of TSP/HAM-like neurological manifestations (1, 44) and hematopoietic diseases, such as large granular lymphoma (LGL), in HTLV-2-infected individuals have been reported (3, 37-39, 46), the extent to which HTLV-2 can induce disease in humans remains unclear. Indeed, even in the condition of immune deficiency, such as infection with human immunodeficiency virus type 1 (HIV-1), HTLV-2 coinfection has not been reported to be associated with cancer or neurological diseases. However, more studies are necessary to fully understand the role of HTLV-2 in human disease. While HTLV-1 infection has been connected with an accelerated course of disease in HIV-1 coinfected patients (2, 34), HTLV-2 has been reported to either have no effect (26) or suggested to exert a potential protective role during HIV-1 infection (12, 23). This protective role is thought to be due to a maintenance of CD4⁺ T cells, lowering immune activation, and delayed progression to AIDS (4, 5). In addition, modulation of cytokine and chemokine networks by HTLV-2 has been suggested to contribute to the control of HIV-1 infection (12, 36, 47). Since studies on the immunological interactions between HIV-1 and HTLV-2 have been performed in patients coinfected with HIV-1 and HTLV-2 in the chronic phase of HIV-1 disease, little is known about the effects of HTLV-2 infection during acute HIV-1 replication, mucosal CD4⁺ T-cell depletion, or HIV-1-specific immune responses. Furthermore, the potential protective effect of an HTLV-2 vector that would target both CD4⁺ and CD8⁺ T cells and induce a low-grade persistent infection makes HTLV-2 an interesting potential vaccine platform for an HIV-1 vaccine.Current HIV-1 vaccine strategies have focused on viral vectors delivering HIV-1 antigens. These vectors stimulate strong, systemic antigen-specific responses but are unable to protect from infection, since they generate only limited mucosal responses and do not persist. The only vaccine approach that has conferred protection in the simian immunodeficiency virus SIV_mac251 macaque model is a live attenuated virus (17), suggesting that persistent expression of viral antigens in mucosal and lymphoid tissues may be necessary. An HTLV-2 vector expressing HIV-1 antigens at mucosal sites that stimulates and maintains T-cell responses in the gut may confer protection from infection by quickly eliminating cells infected by the founder virus at the portal of entry. This study establishes that the Indian rhesus macaque model for HTLV-2 infection is a suitable model to test this hypothesis, as it demonstrates that HTLV-2 targets systemic, lymphoid, as well as mucosal tissues of rhesus macaques. HTLV-2 infection induces humoral as well as cell-mediated immune responses, and importantly, T-cell responses can be found at both systemic and mucosal sites. In this study, we demonstrate that the viral and T-cell dynamics of macaques dually infected with HTLV-2 and SIV_mac251 are similar to those of macaques singly infected with SIV_mac251.     

Effects of Artichoke Latent Virus Infection on the Production of Artichoke Heads

Virus-free and artichoke latent virus (ALV) infected plants of ‘Brindisino’ artichoke obtained by in vitro propagation, were studied over a period of three years to evaluate the effect of ALV infection on artichoke field performance and to determine the infection rate of healthy plants. ALV infection caused qualitative and quantitative changes ‘Brindisino’ artichoke such as leaf and bract discoloration, opening of head apex, delay of first harvest, shortening of head stalk, reduction of head width and a dramatic decrease of yield. Due to the high infection rate of healthy plants during the trial period, the differences in the production of heads between the two groups of plants decreased in the last year of experiment.     

Antibodies Targeting Novel Neutralizing Epitopes of Hepatitis C Virus Glycoprotein Preclude Genotype 2 Virus Infection

Currently, there is no effective vaccine to prevent hepatitis C virus (HCV) infection, partly due to our insufficient understanding of the virus glycoprotein immunology. Most neutralizing antibodies (nAbs) were identified using glycoprotein immunogens, such as recombinant E1E2, HCV pseudoparticles or cell culture derived HCV. However, the fact that in the HCV acute infection phase, only a small proportion of patients are self-resolved accompanied with the emergence of nAbs, indicates the limited immunogenicity of glycoprotein itself to induce effective antibodies against a highly evolved virus. Secondly, in previous reports, the immunogen sequence was mostly the genotype of the 1a H77 strain. Rarely, other genotypes/subtypes have been studied, although theoretically one genotype/subtype immunogen is able to induce cross-genotype neutralizing antibodies. To overcome these drawbacks and find potential novel neutralizing epitopes, 57 overlapping peptides encompassing the full-length glycoprotein E1E2 of subtype 1b were synthesized to immunize BALB/c mice, and the neutralizing reactive of the induced antisera against HCVpp genotypes 1–6 was determined. We defined a domain comprising amino acids (aa) 192–221, 232–251, 262–281 and 292–331 of E1, and 421–543, 564–583, 594–618 and 634–673 of E2, as the neutralizing regions of HCV glycoprotein. Peptides PUHI26 (aa 444–463) and PUHI45 (aa 604–618)-induced antisera displayed the most potent broad neutralizing reactive. Two monoclonal antibodies recognizing the PUHI26 and PUHI45 epitopes efficiently precluded genotype 2 viral (HCVcc JFH and J6 strains) infection, but they did not neutralize other genotypes. Our study mapped a neutralizing epitope region of HCV glycoprotein using a novel immunization strategy, and identified two monoclonal antibodies effective in preventing genotype 2 virus infection.     

Influenza C Virus Infection in Rats

Four-week-old rats (WKA/Hkm strain) were infected intranasally with the Ann Arbor/1/50 strain of influenza C virus and examined for clinical symptoms, virus replication, and serum antibody response. Although the animals showed no definite signs of illness, the virus replicated in the nose, and the hemagglutination-inhibiting (HI) and neutralizing antibodies were produced in their sera. When the inoculum sizes of 10^6.2 and 10^3.2 PFU were used, virus was recovered from nasal homogenates between days 1 and 10, and serum HI antibody became detectable by 10 days after infection. The rats infected with 10^1.2 PFU of the virus continued to shed virus until as late as day 20 without producing serum HI antibody. The amount of virus recovered from the nose was not affected significantly by either sex. age, or strain of the rat except that a slower virus growth was seen in the LE strain. It was also observed that the rats, previously inoculated with 10^3.2 PFU of the virus, showed no virus shedding when reinfected 7 weeks later but produced virus though in low titers when reinfected 50 to 55 weeks later. Virus was also recovered from rats once inoculated with 10^1.2 PFU of the virus when challenged 7 weeks later. Thus repeated infections characteristic of human influenza C can be produced in rats under the restricted conditions.