A Non Mouse-Adapted Dengue Virus Strain as a New Model of Severe Dengue Infection in AG129 Mice

The spread of dengue (DEN) worldwide combined with an increased severity of the DEN-associated clinical outcomes have made this mosquito-borne virus of great global public health importance. Progress in understanding DEN pathogenesis and in developing effective treatments has been hampered by the lack of a suitable small animal model. Most of the DEN clinical isolates and cell culture-passaged DEN virus strains reported so far require either host adaptation, inoculation with a high dose and/or intravenous administration to elicit a virulent phenotype in mice which results, at best, in a productive infection with no, few, or irrelevant disease manifestations, and with mice dying within few days at the peak of viremia. Here we describe a non-mouse-adapted DEN2 virus strain (D2Y98P) that is highly infectious in AG129 mice (lacking interferon-α/β and -γ receptors) upon intraperitoneal administration. Infection with a high dose of D2Y98P induced cytokine storm, massive organ damage, and severe vascular leakage, leading to haemorrhage and rapid death of the animals at the peak of viremia. In contrast, very interestingly and uniquely, infection with a low dose of D2Y98P led to asymptomatic viral dissemination and replication in relevant organs, followed by non-paralytic death of the animals few days after virus clearance, similar to the disease kinetic in humans. Spleen damage, liver dysfunction and increased vascular permeability, but no haemorrhage, were observed in moribund animals, suggesting intact vascular integrity, a cardinal feature in DEN shock syndrome. Infection with D2Y98P thus offers the opportunity to further decipher some of the aspects of dengue pathogenesis and provides a new platform for drug and vaccine testing.     

Recombinant Modified Vaccinia Virus Ankara Expressing Glycoprotein E2 of Chikungunya Virus Protects AG129 Mice against Lethal Challenge

Chikungunya virus (CHIKV) infection is characterized by rash, acute high fever, chills, headache, nausea, photophobia, vomiting, and severe polyarthralgia. There is evidence that arthralgia can persist for years and result in long-term discomfort. Neurologic disease with fatal outcome has been documented, although at low incidences. The CHIKV RNA genome encodes five structural proteins (C, E1, E2, E3 and 6K). The E1 spike protein drives the fusion process within the cytoplasm, while the E2 protein is believed to interact with cellular receptors and therefore most probably constitutes the target of neutralizing antibodies. We have constructed recombinant Modified Vaccinia Ankara (MVA) expressing E3E2, 6KE1, or the entire CHIKV envelope polyprotein cassette E3E26KE1. MVA is an appropriate platform because of its demonstrated clinical safety and its suitability for expression of various heterologous proteins. After completing the immunization scheme, animals were challenged with CHIV-S27. Immunization of AG129 mice with MVAs expressing E2 or E3E26KE1 elicited neutralizing antibodies in all animals and provided 100% protection against lethal disease. In contrast, 75% of the animals immunized with 6KE1 were protected against lethal infection. In conclusion, MVA expressing the glycoprotein E2 of CHIKV represents as an immunogenic and effective candidate vaccine against CHIKV infections.     

Protective Role of Fas-FasL Signaling in Lethal Infection with Herpes Simplex Virus Type 2 in Mice

Herpes simplex virus type 2 (HSV-2) induces acute local infection followed by latent infection in the nervous system and often leads to the development of lethal encephalitis in immunocompromised hosts. The mechanisms of immune protection against lethal HSV-2 infection, however, have not been clarified. In this study, we examined the roles of Fas-Fas ligand (FasL) signaling in lethal infection with HSV-2 by using mice with mutated Fas (lpr) or FasL (gld) in C57BL/6 background. Both lpr and gld mice exhibited higher mortality than wild-type (WT) C57BL/6 mice after infection with virulent HSV-2 strain 186 and showed significantly increased viral titers in the spinal cord compared with WT mice 9 days after infection, just before the mice started to die. There were no differences in the numbers of CD4⁺ and CD8⁺ T cells infiltrated in the spinal cord or in the levels of HSV-2-specific gamma interferon produced by those cells in a comparison of lpr and WT mice 9 days after infection. Adoptive transfer studies demonstrated that CD4⁺ T cells from WT mice protected gld mice from lethal infection by HSV-2. Furthermore, CD4⁺ T cells infiltrated in the spinal cord of HSV-2-infected WT mice expressed functional FasL that induced apoptosis of Fas-expressing target cells in vitro. These results suggest that FasL-mediated cytotoxic activity of CD4⁺ T cells plays an important role in host defense against lethal infection with HSV-2.Fas-Fas ligand (FasL) signaling-induced apoptotic cell death has pleiotropic roles in T-cell-mediated host defense mechanisms. First, Fas and FasL are expressed on activated T cells and thereby limit their number by inducing suicide or fratricide. It is generally accepted that Fas-mediated activation-induced cell death plays a predominant role during chronic infection, whereas starvation-induced cell death mediated by the proapoptotic BH3-only subgroup of the Bcl-2 protein family is the main mechanism for T-cell death during termination of immune responses in acute infection (30). Fas-FasL signaling might also play a role in T-cell development, as suggested by an accumulation of T-cell receptor αβ-positive (TCR αβ⁺) CD4⁻ CD8⁻ T cells expressing B220 in lymphoid organs of mice with mutated Fas (lpr) or FasL (gld) although the origin and functions of such double-negative T cells are still a matter of debate (21). Lastly, Fas-FasL interaction can be directly involved in host defense by inducing apoptosis of infected cells to facilitate pathogen clearance (23). Therefore, the roles of Fas-FasL signaling in immune responses for host defense might vary depending on the pathogen.Herpes simplex virus type 2 (HSV-2) is an alphaherpesvirus that causes genital herpes, the most common viral sexually transmitted disease (29). After initial infection in the vaginal epithelium, HSV-2 invades local nerve termini, travels via retrograde axonal transport to neuronal cell bodies in sensory ganglia, and establishes latent infection (13). However, especially in neonates and immunocompromised hosts, HSV-2 can cause lethal central nervous system (CNS) infection, which indicates the importance of immune systems in limiting the pathogenicity of HSV-2. Immune responses against HSV-2 have been studied in various murine models using different strains of virus and routes of inoculation, with or without vaccination with an attenuated strain of HSV-2. In such vaccination models, CD4⁺ T cells producing gamma interferon (IFN-γ) predominantly conferred protection against challenge with a virulent strain of HSV-2 (11, 19), whereas various subsets of lymphocytes, including NK cells, NK T cells, and TCR γδ T cells as well as CD4⁺ T cells were reported to be involved in host defense against primary infection with virulent HSV-2 (3, 15, 24), in which IFN-γ also played an important role (9). Fas-FasL signaling was shown to be dispensable for the clearance of an attenuated strain of HSV-2, which lacks thymidine kinase and causes only transient mild vaginal pathologies but not neurologic diseases (6, 16). Similarly Fas-mediated apoptosis was not involved in the vaccination effect of the attenuated HSV-2 (11). However, the roles of Fas-FasL signaling in host defense against a virulent strain of HSV-2 have not been clarified.In this study, we examined the roles of Fas-FasL signaling in a murine model of HSV-2 infection by using a highly virulent HSV-2 strain 186 with lpr and gld mice. We found that FasL-Fas signaling plays an important role in host defense against lethal HSV-2 infection.     

A Novel Highly Reproducible and Lethal Nonhuman Primate Model for Orthopox Virus Infection

The intentional re-introduction of Variola virus (VARV), the agent of smallpox, into the human population is of great concern due its bio-terroristic potential. Moreover, zoonotic infections with Cowpox (CPXV) and Monkeypox virus (MPXV) cause severe diseases in humans. Smallpox vaccines presently available can have severe adverse effects that are no longer acceptable. The efficacy and safety of new vaccines and antiviral drugs for use in humans can only be demonstrated in animal models. The existing nonhuman primate models, using VARV and MPXV, need very high viral doses that have to be applied intravenously or intratracheally to induce a lethal infection in macaques. To overcome these drawbacks, the infectivity and pathogenicity of a particular CPXV was evaluated in the common marmoset (Callithrix jacchus).A CPXV named calpox virus was isolated from a lethal orthopox virus (OPV) outbreak in New World monkeys. We demonstrated that marmosets infected with calpox virus, not only via the intravenous but also the intranasal route, reproducibly develop symptoms resembling smallpox in humans. Infected animals died within 1–3 days after onset of symptoms, even when very low infectious viral doses of 5×10² pfu were applied intranasally. Infectious virus was demonstrated in blood, saliva and all organs analyzed.We present the first characterization of a new OPV infection model inducing a disease in common marmosets comparable to smallpox in humans. Intranasal virus inoculation mimicking the natural route of smallpox infection led to reproducible infection. In vivo titration resulted in an MID₅₀ (minimal monkey infectious dose 50%) of 8.3×10² pfu of calpox virus which is approximately 10,000-fold lower than MPXV and VARV doses applied in the macaque models. Therefore, the calpox virus/marmoset model is a suitable nonhuman primate model for the validation of vaccines and antiviral drugs. Furthermore, this model can help study mechanisms of OPV pathogenesis.     

Construction and Characterization of a Single-Cycle Chimeric Flavivirus Vaccine Candidate That Protects Mice against Lethal Challenge with Dengue Virus Type 2

We have previously described a novel flavivirus vaccine technology based on a single-cycle, capsid (C) gene-deleted flavivirus called RepliVAX. RepliVAX can be propagated in cells that express high levels of C but undergoes only a single cycle of infection in vaccinated hosts. Here we report that we have adapted our RepliVAX technology to produce a dengue vaccine by replacing the prM/E genes of RepliVAX WN (a West Nile virus [WNV] RepliVAX) with the same genes of dengue virus type 2 (DENV2). Our first RepliVAX construct for dengue virus (RepliVAX D2) replicated poorly in WNV C-expressing cells. However, addition of mutations in prM and E that were selected during blind passage of a RepliVAX D2 derivative was used to produce a second-generation RepliVAX D2 (designated D2.2) that displayed acceptable growth in WNV C-expressing cells. RepliVAX D2.2 grew better in DENV2 C-expressing cells than WNV C-expressing cells, but after several passages in DENV2 C-expressing cells it acquired further mutations that permitted efficient growth in WNV C-expressing cells. We tested the potency and efficacy of RepliVAX D2.2 in a well-described immunodeficient mouse model for dengue (strain AG129; lacking the receptors for both type I and type II interferons). These mice produced dose-dependent DENV2-neutralizing antibody responses when vaccinated with RepliVAX D2.2. When challenged with 240 50% lethal doses of DENV2, mice given a single inoculation of RepliVAX D2.2 survived significantly longer than sham-vaccinated animals, although some of these severely immunocompromised mice eventually died from the challenge. Taken together these studies indicate that the RepliVAX technology shows promise for use in the development of vaccines that can be used to prevent dengue.     

Ⅲ型登革病毒在THP-1细胞上的ADE模型建立

登革热(dengue fever,DF)是由Ⅰ、Ⅱ、Ⅲ和Ⅳ型登革病毒(dengue virus,DENV)引起的急性传染病,抗体依赖增强感染(antibody-dependent enhancement,ADE)是自限性的登革热以及危及生命的登革出血热(dengue hemorrhagic fever,DHF)或登革休克综合症(dengue shock syndrome,DSS)等重症的主要原因。采用不同稀释度的Ⅱ型登革病毒prM前膜抗体与分离自云南西双版纳重症病人的Ⅲ型登革病毒复合感染THP-1细胞,通过实时荧光定量PCR发现亚中和浓度prM前膜抗体诱发THP-1细胞液中更高浓度的病毒载量。在THP-1细胞系上的研究可为后续研究登革病毒ADE打下坚实的基础。     

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.     

Dengue and Zika Virus Cross-Reactive Human Monoclonal Antibodies Protect against Spondweni Virus Infection and Pathogenesis in Mice

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A Mouse Model of Lethal Infection for Evaluating Prophylactics and Therapeutics against Monkeypox Virus

Monkeypox virus (MPXV) is an orthopoxvirus closely related to variola, the etiological agent of smallpox. In humans, MPXV causes a disease similar to smallpox and is considered to be an emerging infectious disease. Moreover, the use of MPXV for bioterroristic/biowarfare activities is of significant concern. Available small animal models of human monkeypox have been restricted to mammals with poorly defined biologies that also have limited reagent availability. We have established a murine MPXV model utilizing the STAT1-deficient C57BL/6 mouse. Here we report that a relatively low-dose intranasal (IN) infection induces 100% mortality in the stat1^−/− model by day 10 postinfection with high infectious titers in the livers, spleens, and lungs of moribund animals. Vaccination with modified vaccinia virus Ankara (MVA) followed by a booster vaccination is sufficient to protect against an intranasal MPXV challenge and induces an immune response more robust than that of a single vaccination. Furthermore, antiviral treatment with CMX001 (HDP-cidofovir) and ST-246 protects when administered as a regimen initiated on the day of infection. Thus, the stat1^−/− model provides a lethal murine platform for evaluating therapeutics and for investigating the immunological and pathological responses to MPXV infection.During the early smallpox-free epoch, the orthopoxviruses were of minor bioterroristic concern due to the largely vaccinated population; however, this has changed with the increased risk of bioterrorism, and variola virus (VARV) and monkeypox virus (MPXV) are considered to have significant potential to become bioterror agents (36, 37). VARV, the etiological agent of smallpox, is officially stored at two WHO secure laboratories in the United States and Russia; however, there is concern that covert stocks exist. Furthermore, we are currently faced with the possibility of intentional release of wild-type or genetically modified VARV. Of most concern would be viruses encoding human interleukin-4 (IL-4), which could significantly increase virulence, as demonstrated with the mousepox/ectromelia virus (ECTV) model (18). As a result of the cessation of routine vaccination and the high number of individuals that are contraindicated for vaccination, the human population lacks solid “herd immunity” to naturally circulating orthopoxviruses. One such virus that is of particular concern is MPXV, due to its ability to infect humans, its mortality rate of approximately 10% (depending on the strain), its propensity to infect a large number of species, its apparently increasing transmissibility in the human population, and its reportedly expanding host range (36). One such example of increasing host range was observed during 2003 in the United States, where imported African rodents transmitted MPXV to native prairie dogs, which acted as an “amplification reservoir” that allowed for the transmission of MPXV to humans (14).To date, MPXV animal models for efficacy testing of prophylactics and therapeutics have been restricted to nonhuman primates and nonmurine small animal models, such as the 13-lined ground squirrel (Spermophilus tridecemlineatus) (49, 55), the black-tailed prairie dog (Cynomys ludovicianus) (14, 17, 22, 60), and the African dormouse (Graphiurus kelleni) (50). Because the ground squirrel and the prairie dog are difficult to propagate, have low fecundity rates, and have complex husbandry requirements, they must be obtained from their natural habitat and therefore have unknown health statuses (16, 58). Conversely, the African dormouse has many characteristics similar to those of laboratory mice and can be easily propagated in a research vivarium. The disadvantage to this model is that there are few commercially available reagents for characterizing the animals'' response to infection, and their biology is poorly understood (50).Suckling white mice have been shown to be highly susceptible to MPXV inoculations by various routes. Eight-day-old white mice developed disease and died following intraperitoneal or intranasal (IN) inoculations with 1.2 × 10⁶ PFU. Injection into the footpad also induced severe disease and death following 6 × 10² PFU inoculations. Disease symptoms included flabbiness; loss of appetite; and following footpad infections, edema of the foot. Similar symptoms were observed following inoculation by the oral route, which induced 40% lethality. Intradermal inoculations with MPXV resulted in 50% death. The intranasal route of infection was determined to induce the highest level of lethality, causing 100% death in mice as old as 15 days, compared to only 14% and 60% lethality in 12-day-old mice infected orally or via the footpad, respectively (24, 51). Recently, Osorio et al. showed that 4-week-old SCID-BALB/c mice are susceptible to 10⁵ PFU intraperitoneal (IP) MPXV inoculations, resulting in a mean day of death of 9 days postinfection (p.i.) (33). Unfortunately the IP route of infection does not model the natural transmission route of MPXV.Several factors make young (<15 days old) white mice a poor choice for studying MPXV. First, mice do not become fully immunocompetent until approximately 4 or 5 weeks old; therefore, the opportunity to study the immune response to infection is hampered. Moreover, immunoimmature animals cannot be used as models to study MPXV infections in immunocompetent humans. Second, a functioning immune system works in synergy with antiviral therapies to provide protection against viral challenge; thus, antiviral efficacy cannot be properly evaluated. Third, the relatively short susceptible time window of birth to 15 days old makes large-scale experiments impractical. Fourthly, young immunoimmature mice cannot be used to study vaccination efficacy. To this end, we sought to identify adult mice that are susceptible to lethal MPXV challenges and can be used for antiviral and vaccination efficacy studies.In the present study we found that most common strains of adult immunocompetent laboratory mice are resistant to MPXV. We also found that type 1 and type 2 interferon (IFN) receptor-null mice were resistant. Because strains lacking STAT1, a key protein involved in type 1 and 2 IFN signaling networks, have been shown to be sensitive to a wide number of viral and bacterial infections (13, 15, 30, 46, 52-54), we evaluated their sensitivities to MPXV challenges. We found that C57BL/6 mice lacking stat1 (C57BL/6 stat1^−/−) were highly sensitive to MPXV and that 129 mice lacking stat1 were sensitive but to a lesser degree than the C57BL/6 stat1^−/− animals. In this report, we show that the disease course in MPXV-infected C57BL/6 stat1^−/− mice, that is, weight loss and death by day 10 postinfection, is similar to that observed in wild-type mice infected with ECTV, the etiological agent of mousepox (11). Further, we reveal that antiviral therapy with CMX001 or ST-246 protects mice to a degree similar to that of vaccination with Dryvax or modified vaccinia virus Ankara (MVA), supporting the use of the C57BL/6 stat1^−/− as a model to evaluate orthopoxvirus prophylactics and therapeutics.     

裸鼠呼吸道合胞病毒感染的动物模型

呼吸道合胞病毒(RSV)是全世界婴幼儿下呼吸道感染的首位病毒病原体,免疫缺陷个体容易发生严重感染,目前尚无理想RSV感染动物模型用于研究.我们用细胞免疫缺陷裸鼠感染RSV,旨在建立理想的动物模型,为RSV感染的防治研究奠定基础.裸鼠滴鼻感染RSV后肺组织分离到病毒,直接免疫荧光检测到支气管肺泡灌洗液RSV抗原阳性,空斑形成实验检测肺组织病毒滴度在感染后第3天达高峰,并持续到第9天仍能检测到病毒.免疫组化检测RSV抗原主要分布在细支气管、毛细支气管和肺泡上皮细胞胞浆内.肺组织病理学显示RSV感染导致裸鼠淋巴细胞浸润为主的肺间质性炎症,电镜分析超微结构可见到细胞内病毒颗粒和气血屏障的破坏.支气管肺泡灌洗液白细胞计数显示裸鼠RSV感染炎症高峰在感染后第9天.裸鼠RSV感染的病毒复制和病理改变特点与人相似,病毒持续高水平复制,是客观而实用的评价抗RSV制剂效果的小鼠模型.     

裸鼠呼吸道合胞病毒感染的动物模型

呼吸道合胞病毒(RSV)是全世界婴幼儿下呼吸道感染的首位病毒病原体,免疫缺陷个体容易发生严重感染,目前尚无理想RSV感染动物模型用于研究。我们用细胞免疫缺陷裸鼠感染RSV,旨在建立理想的动物模型,为RSV感染的防治研究奠定基础。裸鼠滴鼻感染RSV后肺组织分离到病毒,直接免疫荧光检测到支气管肺泡灌洗液RSV抗原阳性,空斑形成实验检测肺组织病毒滴度在感染后第3天达高峰,并持续到第9天仍能检测到病毒。免疫组化检测RSV抗原主要分布在细支气管、毛细支气管和肺泡上皮细胞胞浆内。肺组织病理学显示RSV感染导致裸鼠淋巴细胞浸润为主的肺间质性炎症,电镜分析超微结构可见到细胞内病毒颗粒和气血屏障的破坏。支气管肺泡灌洗液白细胞计数显示裸鼠RSV感染炎症高峰在感染后第9天。裸鼠RSV感染的病毒复制和病理改变特点与人相似,病毒持续高水平复制,是客观而实用的评价抗RSV制剂效果的小鼠模型。     

Depressed Hypoxic and Hypercapnic Ventilatory Responses at Early Stage of Lethal Avian Influenza A Virus Infection in Mice

H5N1 virus infection results in ~60% mortality in patients primarily due to respiratory failure, but the underlying causes of mortality are unclear. The goal of this study is to reveal respiratory disorders occurring at the early stage of infection that may be responsible for subsequent respiratory failure and death. BALB/c mice were intranasally infected with one of two H5N1 virus strains: HK483 (lethal) or HK486 (non-lethal) virus. Pulmonary ventilation and the responses to hypoxia (HVR; 7% O₂ for 3 min) and hypercapnia (HCVR; 7% CO₂ for 5 min) were measured daily at 2 days prior and 1, 2, and 3 days postinfection (dpi) and compared to mortality typically by 8 dpi. At 1, 2, and 3 dpi, immunoreactivities (IR) of substance P (SP-IR) in the nodose ganglion or tyrosine hydroxylase (TH-IR) in the carotid body coupled with the nucleoprotein of influenza A (NP-IR) was examined in some mice, while arterial blood was collected in others. Our results showed that at 2 and 3 dpi: 1) both viral infections failed to alter body temperature and weight, V˙CO2, or induce viremia while producing similarly high lung viral titers; 2) HK483, but not HK486, virus induced tachypnea and depressed HVR and HCVR without changes in arterial blood pH and gases; and 3) only HK483 virus led to NP-IR in vagal SP-IR neurons, but not in the carotid body, and increased density of vagal SP-IR neurons. In addition, all HK483, rather than HK486, mice died at 6 to 8 dpi and the earlier death was correlated with more severe depression of HVR and HCVR. Our data suggest that tachypnea and depressed HVR/HCVR occur at the early stage of lethal H5N1 viral infection associated with viral replication and increased SP-IR density in vagal neurons, which may contribute to the respiratory failure and death.     

Immunodiagnosis of Dengue Virus Infection Using Saliva

Keeping in view the complications and the case fatality associated with dengue virus, several serologic tests have been developed. However, the major drawback of these serologic tests is the need for a venous blood sample obtained by invasive venipuncture. As a noninvasive alternative, saliva provides a body fluid that contains antibodies of diagnostic importance. Hence, the detection of DEN-specific IgM and IgG antibodies in serum and saliva from 80 patients was compared. Salivary IgM antibodies were detected in 100% of the serum IgM-positive samples and in 30% of the serum samples that were negative for IgM antibodies. Salivary IgG antibodies were detected in 93.3% of the serum samples that were positive for anti-dengue IgG antibodies and in none of the serum IgG-negative cases. None of the specimens from the healthy controls showed the presence of IgM or IgG antibodies. The detection of both IgG and IgM antibodies in saliva correlated well with the serum IgG and IgM detection by the ELISA test (r = 0.6322 and r = 0.4227). Detection of salivary IgM antibodies by ELISA showed 100% sensitivity, 70% specificity, 90.9% positive predictive value, and 100% negative predictive value. The detection of IgG in saliva proved to be a promising tool as the sensitivity, specificity, positive predictive value, and negative predictive value were found out to be 93.3%, 100%, 100%, and 83.3%, respectively. Thus, from this study we conclude that the detection of DEN-specific salivary IgG and IgM antibodies are useful markers for dengue infection.     

Mice Lacking Functional STAT1 Are Highly Susceptible to Lethal Infection with Lassa Virus

Lassa fever (LF) is a potentially lethal human disease that is caused by the arenavirus Lassa virus (LASV). Annually, around 300,000 infections with up to 10,000 deaths occur in regions of Lassa fever endemicity in West Africa. Here we demonstrate that mice lacking a functional STAT1 pathway are highly susceptible to infection with LASV and develop lethal disease with pathology similar to that reported in humans.