Molecular analysis of a neurovirulent murine leukemia virus, {\it ts\/}1

ts1 is a neurovirulent spontaneous temperature-sensitive mutant of Moloney murine leukemia virus TB (MoMuLV-TB). MoMuLV-TB causes T-cell lymphoma or lymphoid leukemia in mice after a long latency period whereas ts1 causes a progressive hindlimb paralytic disease after a much shorter latency period. In previous studies, it had been shown that the temperature-sensitive defect resided in the $env$ gene. At the restrictive temperature, the envelope precursor polyprotein, gPr80$\sp{env}$, is inefficiently processed intracellularly into a heterodimer consisting of two cleavage products, gp70 and Prp15E. This inefficient processing is correlated with neurovirulence. In this study, the nucleotide sequences of the env genes for both ts1 and MoMuLV-TB were determined, and the encoded amino acid sequences were deduced from the DNA sequences. There were four unique amino acid substitutions in the gPr80$\sp{env}$ of ts1. In order to determine which unique amino acid was responsible for the phenotypic characteristics of ts1, a set of hybrid genomes was constructed by exchanging restriction fragments between ts1 and MoMuLV-TB. NIH 3T3 cells were transfected with the hybrid genomes to obtain infectious hybrid viruses. Assays of the hybrid viruses showed that a Val-25$\to$Ile substitution in gPr80$\sp{env}$ was responsible for the temperature sensitivity, inefficient processing, and neurovirulence of ts1. In further studies, the Ile-25 in gPr80$\sp{env}$ was substituted with Thr, Ala, Leu, Gly, and Glu by site-directed mutagenesis to generate a new set of mutant viruses, i.e., ts1-T, -A, -L, -G, and -E, respectively. The rank order of the mutants for temperature sensitivity was: ts1-E $>$ ts1-G $>$ ts1-L $>$ ts1-A $>$ ts1 $>$ ts1-T. The degree of temperature sensitivity of each of the mutants also correlated with the degree of inefficient processing of gPr80$\sp{env}$. The mutant viruses were assayed for neurovirulence. ts1-T caused whole body tremor, ts1-A caused hindlimb paralysis, ts1-L caused paraparesis, but ts1-G and -E were not neurovirulent. These results show that inefficient processing of gPr80$\sp{env}$ is correlated with neurovirulence, but if processing of gPr80$\sp{env}$ is too inefficient there is no neurovirulence. Furthermore, the disease profile of each of the neurovirulent viruses depends on the degree of inefficient processing of gPr80$\sp{env}$. ^

Fulminant hepatic and multiple organ failure following acute viral tonsillitis: a case report.

BACKGROUND Pyogenic tonsillitis may often be observed in the general Western population. In severe cases, it may require antibiotic treatment or even hospitalization and often a prompt clinical response will be noted. Here we present an unusual case of progressive multiple organ failure including fulminant liver failure following acute tonsillitis initially mistaken for "classic" pyogenic (that is bacterial) tonsillitis. CASE PRESENTATION A 68-year-old previously healthy white man was referred with suspicion of pyogenic angina. After tonsillectomy, he developed acute liver failure and consecutive multiple organ failure including acute hemodynamic, pulmonary and dialysis-dependent renal failure. Immunohistopathological analysis of his tonsils and liver as well as serum polymerase chain reaction analyses revealed herpes simplex virus-2 to be the causative pathogen. Treatment included high-dose acyclovir and multiorgan supportive intensive care therapy. His final outcome was favorable. CONCLUSIONS Fulminant herpes simplex virus-2-induced multiple organ failure is rarely observed in the Western hemisphere and should be considered a potential diagnosis in patients with tonsillitis and multiple organ failure including acute liver failure. From a clinical perspective, it seems important to note that fulminant herpes simplex virus-2 infection may masquerade as "routine" bacterial severe sepsis/septic shock. This persevering condition should be diagnosed early and treated goal-oriented in order to gain control of this life-threatening condition.

Interaction of measles virus glycoproteins with the surface of uninfected peripheral blood lymphocytes induces immunosuppression in vitro

A marked suppression of immune function has long been recognized as a major cause of the high morbidity and mortality rate associated with acute measles. As a hallmark of measles virus (MV)-induced immunosuppression, peripheral blood lymphocytes (PBLs) isolated from patients exhibit a significantly reduced capacity to proliferate in response to mitogens, allogens, or recall antigens. In an in vitro system we show that proliferation of naive PBLs [responder cells (RCs)] in response to a variety of stimuli was significantly impaired after cocultivation with MV-infected, UV-irradiated autologous PBLs [presenter cells (PCs)]. We further observed that a 50% reduction in proliferation of RCs could still be observed when the ratio of PC to RC was 1:100. The effect was completely abolished after physical separation of the two populations, which suggests that soluble factors were not involved. Proliferative inhibition of the RCs was observed after short cocultivation with MV-infected cells, which indicates that surface contact between one or more viral proteins and the RC population was required. We identified that the complex of both MV glycoproteins, F and H, is critically involved in triggering MV-induced suppression of mitogen-dependent proliferation, since the effect was not observed (i) using a recombinant MV in which F and H were replaced with vesicular stomatitis virus G or (ii) when either of these proteins was expressed alone. Coexpression of F and H, however, lead to a significant proliferative inhibition in the RC population. Our data indicate that a small number of MV-infected PBLs can induce a general nonresponsiveness in uninfected PBLs by surface contact, which may, in turn, account for the general suppression of immune responses observed in patients with acute measles.

Early physiological abnormalities after simian immunodeficiency virus infection

Central nervous system (CNS) damage and dysfunction are devastating consequences of HIV infection. Although the CNS is one of the initial targets for HIV infection, little is known about early viral-induced abnormalities that can affect CNS function. Here we report the detection of early physiological abnormalities in simian immunodeficiency virus-infected monkeys. The acute infection caused a disruption of the circadian rhythm manifested by rises in body temperature, observed in all five individuals between 1 and 2 weeks postinoculation (p.i.), accompanied by a reduction in daily motor activity to 50% of control levels. Animals remained hyperthermic at 1 and 2 months p.i. and returned to preinoculation temperatures at 3 months after viral inoculation. Although motor activity recovered to baseline values at 1 month p.i., activity levels then decreased to approximately 50% of preinoculation values over the next 2 months. Analysis of sensory-evoked responses 1 month p.i. revealed distinct infection-induced changes in auditory-evoked potential peak latencies that persisted at 3 months after viral inoculation. These early physiological abnormalities may precede the development of observable cognitive or motor deficiencies and can provide an assay to evaluate agents to prevent or alleviate neuronal dysfunction.

Induction of maturation of human blood dendritic cell precursors by measles virus is associated with immunosuppression

As well as inducing a protective immune response against reinfection, acute measles is associated with a marked suppression of immune functions against superinfecting agents and recall antigens, and this association is the major cause of the current high morbidity and mortality rate associated with measles virus (MV) infections. Dendritic cells (DCs) are antigen-presenting cells crucially involved in the initiation of primary and secondary immune responses, so we set out to define the interaction of MV with these cells. We found that both mature and precursor human DCs generated from peripheral blood monocytic cells express the major MV protein receptor CD46 and are highly susceptible to infection with both MV vaccine (ED) and wild-type (WTF) strains, albeit with different kinetics. Except for the down-regulation of CD46, the expression pattern of functionally important surface antigens on mature DCs was not markedly altered after MV infection. However, precursor DCs up-regulated HLA-DR, CD83, and CD86 within 24 h of WTF infection and 72 h after ED infection, indicating their functional maturation. In addition, interleukin 12 synthesis was markedly enhanced after both ED and WTF infection in DCs. On the other hand, MV-infected DCs strongly interfered with mitogen-dependent proliferation of freshly isolated peripheral blood lymphocytes in vitro. These data indicate that the differentiation of effector functions of DCs is not impaired but rather is stimulated by MV infection. Yet, mature, activated DCs expressing MV surface antigens do give a negative signal to inhibit lymphocyte proliferation and thus contribute to MV-induced immunosuppression.

Prevention of hepatitis C virus infection in chimpanzees by hyperimmune serum against the hypervariable region 1 of the envelope 2 protein

The identification of the neutralization domains of hepatitis C virus (HCV) is essential for the development of an effective vaccine. Here, we show that the hypervariable region 1 (HVR1) of the envelope 2 (E2) protein is a critical neutralization domain of HCV. Neutralization of HCV in vitro was attempted with a rabbit hyperimmune serum raised against a homologous synthetic peptide derived from the HVR1 of the E2 protein, and the residual infectivity was evaluated by inoculation of HCV-seronegative chimpanzees. The source of HCV was plasma obtained from a patient (H) during the acute phase of posttransfusion non-A, non-B hepatitis, which had been titered for infectivity in chimpanzees. The anti-HVR1 antiserum induced protection against homologous HCV infection in chimpanzees, but not against the emergence of neutralization escape mutants that were found to be already present in the complex viral quasispecies of the inoculum. The finding that HVR1 can elicit protective immunity opens new perspectives for the development of effective preventive strategies. However, the identification of the most variable region of HCV as a critical neutralization domain poses a major challenge for the development of a broadly reactive vaccine against HCV.

In vivo analysis of the 3′ untranslated region of the hepatitis C virus after in vitro mutagenesis of an infectious cDNA clone

Large sections of the 3′ untranslated region (UTR) of hepatitis C virus (HCV) were deleted from an infectious cDNA clone, and the RNA transcripts from seven deletion mutants were tested sequentially for infectivity in a chimpanzee. Mutants lacking all or part of the 3′ terminal conserved region or the poly(U–UC) region were unable to infect the chimpanzee, indicating that both regions are critical for infectivity in vivo. However, the third region, the variable region, was able to tolerate a deletion that destroyed the two putative stem–loop structures within this region. Mutant VR-24 containing a deletion of the proximal 24 nt of the variable region of the 3′ UTR was viable in the chimpanzee and seemed to replicate as well as the undeleted parent virus. The chimpanzee became viremic 1 week after inoculation with mutant VR-24, and the HCV genome titer increased over time during the early acute infection. Therefore, the poly(U–UC) region and the conserved region, but not the variable region, of the 3′ UTR seem to be critical for in vivo infectivity of HCV.

Multiple modes of cellular activation and virus transmission in HIV infection: A role for chronically and latently infected cells in sustaining viral replication

CD4+ T cell activation, required for virus replication in these cells, occurs in local microenvironmental domains in transient bursts. Thus, although most HIV originates from short-lived virus-producing cells, it is unlikely that chronic infection is generally sustained in rapid continuous cycles of productive infection as has been proposed. Such continuity of productive infection cycles would depend on efficient long-range transmission of HIV from one set of domains to another, in turn requiring the maintenance of sufficiently high concentrations of cell-free virus across lymphoid tissues at all times. By contrast, long-lived cellular sources of HIV maintain the capacity to infect newly activated cells at close range despite the temporal and spatial discontinuities of activation events. Such proximal activation and transmission (PAT) involving chronically and latently infected cells may be responsible for sustained infection, particularly when viral loads are low. Once CD4 cells are productively infected through PAT, they can infect other activated cells in their immediate vicinity. Such events propagate locally but generally do not spread systemically, unlike in the acute phase of the infection, because of the early establishment of protective anergy. Importantly, antiretroviral drug treatment is likely to differentially impact long-range transmission and PAT.

Virus-specific CD8+ T cell numbers are maintained during γ-herpesvirus reactivation in CD4-deficient mice

The murine γ-herpesvirus 68 replicates in epithelial sites after intranasal challenge, then persists in various cell types, including B lymphocytes. Mice that lack CD4+ T cells (I-Ab−/−) control the acute infection, but suffer an ultimately lethal recrudescence of lytic viral replication in the respiratory tract. The consequences of CD4+ T cell deficiency for the generation and maintenance of murine γ-herpesvirus 68-specific CD8+ set now have been analyzed by direct staining with viral peptides bound to major histocompatibility complex class I tetramers and by a spectrum of functional assays. Both acutely and during viral reactivation, the CD8+ T cell responses in the I-Ab−/− group were no less substantial than in the I-Ab+/+ controls. Indeed, virus-specific CD8+ T cell numbers were increased in the lymphoid tissue of clinically compromised I-Ab−/− mice, although relatively few of the potential cytotoxic T lymphocyte effectors were recruited back to the site of pathology in the lung. Thus the viral reactivation that occurs in the absence of CD4+ T cells was not associated with any exhaustion of the virus-specific cytotoxic T lymphocyte response. It seems that CD8+ T cells alone are insufficient to maintain long-term control of this persistent γ-herpesvirus.

Whole body positron emission tomography imaging of simian immunodeficiency virus-infected rhesus macaques.

Pathogenesis of simian immunodeficiency virus (SIV) infection in rhesus macaques begins with acute viremia and then progresses to a distributed infection in the solid lymphoid tissues, which is followed by a process of cellular destruction leading to terminal disease and death. Blood and tissue specimens show the progress of infection at the cellular level but do not reveal the pattern of infection and host responses occurring throughout the body. The purpose of this investigation was to determine whether positron emission tomography (PET) imaging with intravenous 2-18F-2-deoxyglucose (FDG) could identify activated lymphoid tissues in a living animal and whether this pattern would reflect the extent of SIV infection. PET images from SIV-infected animals were distinguishable from uninfected controls and revealed a pattern consistent with widespread lymphoid tissue activation. Significant FDG accumulation in colon along with mesenteric and ileocaecal lymph nodes was found in SIV infection, especially during terminal disease stages. Areas of elevated FDG uptake in the PET images were correlated with productive SIV infection using in situ hybridization as a test for virus replication. PET-FDG images of SIV-infected animals correlated sites of virus replication with high FDG accumulation. These data show that the method can be used to evaluate the distribution and activity of infected tissues in a living animal without biopsy. Fewer tissues had high FDG uptake in terminal animals than midstage animals, and both were clearly distinguishable from uninfected animal scans.

Expression of Norwalk virus capsid protein in transgenic tobacco and potato and its oral immunogenicity in mice.

Alternatives to cell culture systems for production of recombinant proteins could make very safe vaccines at a lower cost. We have used genetically engineered plants for expression of candidate vaccine antigens with the goal of using the edible plant organs for economical delivery of oral vaccines. Transgenic tobacco and potato plants were created that express the capsid protein of Norwalk virus, a calicivirus that causes epidemic acute gastroenteritis in humans. The capsid protein could be extracted from tobacco leaves in the form of 38-nm Norwalk virus-like particles. Recombinant Norwalk virus-like particle (rNV) was previously recovered when the same gene was expressed in recombinant baculovirus-infected insect cells. The capsid protein expressed in tobacco leaves and potato tubers cosedimented in sucrose gradients with insect cell-derived rNV and appeared identical to insect cell-derived rNV on immunoblots of SDS/polyacrylamide gels. The plant-expressed rNV was orally immunogenic in mice. Extracts of tobacco leaf expressing rNV were given to CD1 mice by gavage, and the treated mice developed both serum IgG and secretory IgA specific for rNV. Furthermore, when potato tubers expressing rNV were fed directly to mice, they developed serum IgG specific for rNV. These results indicate the potential usefulness of plants for production and delivery of edible vaccines. This is an appropriate technology for developing countries where vaccines are urgently needed.

Kinetics of cytokine expression during primary human immunodeficiency virus type 1 infection.

In the present study, we have determined the kinetics of constitutive expression of a panel of cytokines [interleukin (IL) 2, IL-4, IL-6, IL-10, interferon gamma (IFN-gamma), and tumor necrosis factor alpha (TNF-alpha)] in sequential peripheral blood mononuclear cell samples from nine individuals with primary human immunodeficiency virus infection. Expression of IL-2 and IL-4 was barely detected in peripheral blood mononuclear cells. However, substantial levels of IL-2 expression were found in mononuclear cells isolated from lymph node. Expression of IL-6 was detected in only three of nine patients, and IL-6 expression was observed when transition from the acute to the chronic phase had already occurred. Expression of IL-10 and TNF-alpha was consistently observed in all patients tested, and levels of both cytokines were either stable or progressively increased over time. Similar to IL-10 and TNF-alpha, IFN-gamma expression was detected in all patients; however, in five of nine patients, IFN-gamma expression peaked very early during primary infection. The early peak in IFN-gamma expression coincided with oligoclonal expansions of CD8+ T cells in five of six patients, and CD8+ T cells mostly accounted for the expression of this cytokine. These results indicate that high levels of expression of proinflammatory cytokines are associated with primary infection and that the cytokine response during this phase of infection is strongly influenced by oligoclonal expansions of CD8+ T cells.

Neoplastic Transformation of T Lymphocytes through Transgenic Expression of a Virus Host Modification Protein

Virus host evasion genes are ready-made tools for gene manipulation and therapy. In this work we have assessed the impact in vivo of the evasion gene A238L of the African Swine Fever Virus, a gene which inhibits transcription mediated by both NF-κB and NFAT. The A238L gene has been selectively expressed in mouse T lymphocytes using tissue specific promoter, enhancer and locus control region sequences for CD2. The resulting two independently derived transgenic mice expressed the transgene and developed a metastasic, angiogenic and transplantable CD4(+)CD8(+)CD69(-) lymphoma. The CD4(+)CD8(+)CD69(-) cells also grew vigorously in vitro. The absence of CD69 from the tumour cells suggests that they were derived from T cells at a stage prior to positive selection. In contrast, transgenic mice similarly expressing a mutant A238L, solely inhibiting transcription mediated by NF-κB, were indistinguishable from wild type mice. Expression of Rag1, Rag2, TCRβ-V8.2, CD25, FoxP3, Bcl3, Bcl2 l14, Myc, IL-2, NFAT1 and Itk, by purified CD4(+)CD8(+)CD69(-) thymocytes from A238L transgenic mice was consistent with the phenotype. Similarly evaluated expression profiles of CD4(+)CD8(+) CD69(-) thymocytes from the mutant A238L transgenic mice were comparable to those of wild type mice. These features, together with the demonstration of (mono-)oligoclonality, suggest a transgene-NFAT-dependent transformation yielding a lymphoma with a phenotype reminiscent of some acute lymphoblastic lymphomas.

The 2014 chikungunya virus outbreak in the U.S. Virgin Islands: epidemiology, long-term health outcomes, and economic burden

Thesis (Ph.D.)--University of Washington, 2016-06

Contemporaneous fluctuations in T cell responses to persistent herpes virus infections

The classical paradigm for T cell dynamics suggests that the resolution of a primary acute virus infection is followed by the generation of a long-lived pool of memory T cells that is thought to be highly stable. Very limited alteration in this repertoire is expected until the immune system is re-challenged by reactivation of latent viruses or by cross-reactive pathogens. Contradicting this view, we show here that the T cell repertoire specific for two different latent herpes viruses in the peripheral blood displayed significant contemporaneous co-fluctuations of virus-specific CD8(+) T cells. The coordinated responses to two different viruses suggest that the fluctuations within the T cell repertoire may be driven by sub-clinical viral reactivation or a more generalized 'bystander' effect. The later contention was supported by the observation that, while absolute number of CD3(+) T cells and their subsets and also the cell surface phenotype of antigen-specific T cells remained relatively constant, a loss of CD62L expression in the total CD8(+) T cell population was coincident with the expansion of tetramer-positive virus-specific T cells. This study demonstrates that the dynamic process of T cell expansion and contractions in persistent viral infections is not limited to the acute phase of infection, but also continues during the latent phase of infection.