Pan-viral protection against arboviruses by activating skin macrophages at the inoculation site.

Arthropod-borne viruses (arboviruses) are important human pathogens for which there are no specific antiviral medicines. The abundance of genetically distinct arbovirus species, coupled with the unpredictable nature of their outbreaks, has made the development of virus-specific treatments challenging. Instead, we have defined and targeted a key aspect of the host innate immune response to virus at the arthropod bite that is common to all arbovirus infections, potentially circumventing the need for virus-specific therapies. Using mouse models and human skin explants, we identify innate immune responses by dermal macrophages in the skin as a key determinant of disease severity. Post-exposure treatment of the inoculation site by a topical TLR7 agonist suppressed both the local and subsequent systemic course of infection with a variety of arboviruses from the Alphavirus, Flavivirus, and Orthobunyavirus genera. Clinical outcome was improved in mice after infection with a model alphavirus. In the absence of treatment, antiviral interferon expression to virus in the skin was restricted to dermal dendritic cells. In contrast, stimulating the more populous skin-resident macrophages with a TLR7 agonist elicited protective responses in key cellular targets of virus that otherwise proficiently replicated virus. By defining and targeting a key aspect of the innate immune response to virus at the mosquito bite site, we have identified a putative new strategy for limiting disease after infection with a variety of genetically distinct arboviruses.

Cats are not small dogs: is there an immunological explanation for why cats are less affected by arthropod-borne disease than dogs?

It is widely recognized that cats appear to be less frequently affected by arthropod-borne infectious diseases than dogs and share fewer zoonotic pathogens with man. This impression is supported by the relative lack of scientific publications related to feline vector-borne infections. This review explores the possible reasons for the difference between the two most common small companion animal species, including the hypothesis that cats might have a genetically-determined immunological resistance to arthropod vectors or the microparasites they transmit. A number of simple possibilities might account for the lower prevalence of these diseases in cats, including factors related to the lifestyle and behaviour of the cat, lesser spend on preventative healthcare for cats and reduced opportunities for research funding for these animals. The dog and cat have substantially similar immune system components, but differences in immune function might in part account for the markedly distinct prevalence and clinicopathological appearance of autoimmune, allergic, idiopathic inflammatory, immunodeficiency, neoplastic and infectious diseases in the two species. Cats have greater genetic diversity than dogs with much lower linkage disequilibrium in feline compared with canine breed groups. Immune function is intrinsically related to the nature of the intestinal microbiome and subtle differences between the canine and feline microbial populations might also impact on immune function and disease resistance. The reasons for the apparent lesser susceptibility of cats to arthropod-borne infectious diseases are likely to be complex, but warrant further investigation.

Use of Testing for West Nile Virus and Other Arboviruses.

In the United States, the most commonly diagnosed arboviral disease is West Nile virus (WNV) infection. Diagnosis is made by detecting WNV IgG or viral genomic sequences in serum or cerebrospinal fluid. To determine frequency of this testing in WNV-endemic areas, we examined the proportion of tests ordered for patients with meningitis and encephalitis at 9 hospitals in Houston, Texas, USA. We identified 751 patients (567 adults, 184 children), among whom 390 (52%) experienced illness onset during WNV season (June-October). WNV testing was ordered for 281 (37%) of the 751; results indicated acute infection for 32 (11%). Characteristics associated with WNV testing were acute focal neurologic deficits; older age; magnetic resonance imaging; empirically prescribed antiviral therapy; worse clinical outcomes: and concomitant testing for mycobacterial, fungal, or other viral infections. Testing for WNV is underutilized, and testing of patients with more severe disease raises the possibility of diagnostic bias in epidemiologic studies.

Divergent cerebrospinal fluid cytokine network induced by non-viral and different viral infections on the central nervous system.

BACKGROUND: Meningoencephalitis is one of the most common disorders of the central nervous system (CNS) worldwide. Viral meningoencephalitis differs from bacterial meningitis in several aspects. In some developing countries, bacterial meningitis has appropriate clinical management and chemotherapy is available. Virus-associated and virus not detected meningoencephalitis are treatable, however, they may cause death in a few cases. The knowledge of how mediators of inflammation can induce disease would contribute for the design of affordable therapeutic strategies, as well as to the diagnosis of virus not detected and viral meningoencephalitis. Cytokine-induced inflammation to CNS requires several factors that are not fully understood yet. METHODS: Considering this, several cytokines were measured in the cerebrospinal fluid (CSF) of patients with undiagnosed and viral meningoencephalitis, and these were correlated with cellularity in the CSF. RESULTS: The results demonstrate that an altered biochemical profile alongside increased cellularity in the cerebrospinal fluid is a feature of patients with meningoencephalitis that are not associated with the detection of virus in the CNS (P < 0.05). Moreover, HIV-positive patients (n = 10) that evolve with meningoencephalitis display a distinct biochemical/cytological profile (P < 0.05) in the cerebrospinal fluid. Meningoencephalitis brings about a prominent intrathecal cytokine storm regardless of the detection of virus as presumable etiological agent. In the case of Enterovirus infection (n = 13), meningoencephalitis elicits robust intrathecal pro-inflammatory cytokine pattern and elevated cellularity when compared to herpesvirus (n = 15) and Arbovirus (n = 5) viral infections (P < 0.05). CONCLUSION: Differences in the cytokine profile of the CSF may be unique if distinct, viral or presumably non-viral pathways initially trigger the inflammatory response in the CNS.

[Virus infections and interferon inducers in the complex therapy].

Interferon inductors of various chemical groups, belonging to antivirals, and induction of several types of endogenous interferon in blood serum are described. Cycloferon was shown efficient in the complex treatment of chronic hepatitis C, tuberculosis in HIV-infected subjects, arbovirus diseases, influenza and acute respiratory virus infections.

The Acre Project: the epidemiology of malaria and arthropod-borne virus infections in a rural Amazonian population

The authors describe the baseline malaria prevalence and arbovirus seroprevalence among 467 subjects in an ongoing cohort study in rural Amazonia. Most subjects (72.2 percent) reported one or more previous episodes of malaria, and 15.6 percent had been hospitalized for malaria, but only 3.6 percent of individuals five years or older had malaria parasites detected by microscopy (10 with Plasmodium vivax and 4 with P. falciparum). Antibodies to Alphavirus, Orthobunyavirus, and/or Flavivirus were detected by hemagglutination inhibition (HI) in 42.6 percent of subjects aged five years or older, with a higher seropositivity rate among males (49.2 percent) than females (36.2 percent). Since 98.9 percent of subjects had been immunized for yellow fever, the presence of cross-reactive antibodies to dengue and other Flaviviruses cannot be ruled out, but at least 12 subjects (3.3 percent) with IgM antibodies to dengue virus detected by ELISA had a putative recent exposure to this virus.

[Anti-arbovirus antibodies positive serum screening in population of Saratov]. / Rezul'taty ussledovaniia syvorotok krovi naseleniia Saratova na antitela k arbovirusam.

Seroepidemiological studies revealed the existence of a population stratum immune to West Nile and Sindbis viruses in the Saratov region. Screening of 218 sera showed that the stratum immune to arboviruses increased from 1998 to 2000. The incidence of antibodies to Batai and Sindbis viruses was the highest. Activation of natural foci of these arboviruses can lead to exacerbation of the epidemic situation in the region.

Establishment and characterization of a new continuous cell line from Lutzomyia longipalpis (Diptera: Psychodidae) and its susceptibility to infections with arboviruses and Leishmania chagasi

Embryonic tissue explants of the sand fly Lutzomyia longipalpis (Lutz & Neiva 1912) the main vector of Leishmania chagasi (Cunha and Chagas), were used to obtain a continuous cell line (Lulo). The tissues were seeded in MM/VP12 medium and these were incubated at 28ºC. The first subculture was obtained 45 days after explanting and 96 passages have been made to date. Lulo is composed of epithelioid cells, showed a 0.04 generations/hour exponential growth rate and population doubling time at 24.7 h. The cell line isoenzymatic profiles were determined by using PGI, PGM, MPI and 6-PGDH systems, coinciding with patterns obtained from the same species and colony's pupae and adults. The species karyotype characteristics were recognized (2n = 8), in which pair 1 is subtelocentric and pairs 2, 3 and 4 are metacentric. Lulo was free from bacterial, fungal, mycoplasmic and viral infection. Susceptibility to five arbovirus was determined, the same as Lulo interaction with Leishmania promastigotes.

Historical, Epidemiological and Ecological Aspects of Arboviruses in Argentina: Flaviviridae, Bunyaviridae and Rhabdoviridae

This is a review of the arboviruses in Argentina belonging to families Flaviviridae, Bunyaviridae and Rhabdoviridae. Of the many viruses beloging to these families, the flavivirus St. Louis encephalitis (SLE), has been most intensively studies. SLE virus strains have been recovered from three sources: 2 strains from humans with an undifferentiated, febrile disease; 6 from mosquitoes; and 2 from rodents. The viruses recovered from rodents are attenuated and those from mosquitoes are virulent based on a neuroinvasiveness test in mice; the degree of virulence of the mosquito strains remain to be analyzed. Serological surveys indicate a wide distribution and endemicity of SLE virus in the temperate and subtropical areas (central and northern Argentina), but no data are available from the Andean region or from the South. The virulent SLE virus strains appear to be transmitted between Culex (Cx.) spp., from which they were isolated, and wild birds, based on antibody prevalence. A urban cycle may involve Cx. quinquefasciatus (source of a viral isolate and a competent experimental vector) and abundant birds (house sparrows, doves, and/or chickens), chickens are experimentally competent host species. Despite similarities in the ecology of SLE between Argentina and North America, urban outbreaks of SLE have not recognized. Possible explanations for this discrepancy include virus strain differences in virulence, ecologic factors determining the rate os virus transmission, and the lack of disease recognition and specific laboratory diagnosisof human meningoencephalitis. The transmission cycle of attenuated SLE virus strains isolated from rodents has not been studied. Ilheus virus has been isolated only once from a human being. The available serological data are difficult to interpret due to cross-reactivity with other flaviviruses, and the ecology and medical importance of this agent remain uncertain. Dengue has not been recognized in Argentina since 1916, although its vector, Aedes aegypti, was not eradicated until 1963. Dengue was previously present in coastal localities of Chaco, Corrientes and Misiones Provinces. Within the last few years, Argentina was reinfested by Ae. aegypti. Although no human cases have yet been reported, outbreaks of dengue in bordering countries (Brazil, Paraguay, Bolovia) since 1986, clearly signal that the country in once again at risk of importation and spread of the viruse

Arthropod-Borne viral Diseases in Peru

Arthropode-Borne viral diseases have been a significant cause of morbidity and mortality for several decades in Peru. Epidemics and epizootics of Venezuelan equine encephalitis (VEE), subtype IAB virus occurred among humans and equine at intermittent intervals from 1925 through 1973 along the Pacific coastal plains, extending southward from the most northern Departament of Tumbes to the Departament of Ica. While the VEE IAB virus has not been detected since 1973, several isolates of VEE ID and an isolate VEE IIIC were obtained during 1971 and 1975 from mosquitoes and/or sentinel hamster in Quistococha, northeastern Amazon region. In 1994, the first human cases, associated with VEE virus ID were diagnosed among Peruvian soldiers near Pantoja, northern Amazon region, and during 1995, primarily among students and military personnel in Iquitos, northastern Amazon region. As early as 1913 , a disease resembling yellow fever was recognized in the Amazon region Peru. Outbreaks of this disease have continued to occur, apparently at annual interval, with the most recent and the largest sylvan outbreak ever recorded in Peru being documented during 1995 along the eastern foothills of the Andes Mountains. In 1990, dengue (DEN) 1 and DEN4 were first isolated in Peru during an outbreak of DEN fever among residents of the city of Iquitos, northeastern Amazon basin region. Seroepidemiological and case surveillance studies conducted 1992 through 1995 documented that DEN 1 continued to cause cases of DEN fever in Iquitos, and in 1995, an outbreak was associated with the introduction of DEN 2 into the community. Outbreaks of DEN fever, associated with DEN 1 occurred during 1994 and 1995 in the northern coastal cities of Tumbes and Piura, and in Pucallpa, Amazon basin region. In 1995, the first isolations of DEN 2 were obtained from febriles cases in Tumbes, Piura and Pucallpa. Although 2 serotypes of DEN were associated with human infection, none of the cases presented with hemorragic manifestations. The first isolations of Oropouche (ORO) fever virus were obtained during 1992 from febrile patients in Iquitos. The virus was isolated during 1994 from febrile cases and serological results revealed that ORO was the cause of an outbreak in the southeastern Amazon region. A single isolate of ORO virus was obtained during 1995 from a febrile patient in Iquitos

Evidências sorológicas da circulação do arbovírus Rocio (Flaviviridae) na Bahia / Serological evidence of the circulation of the Rocio arbovirus (Flaviviridae) in Bahia

Oito casos com anticorpos anti-Rocio são descritos, de quatro cidades do Estado da Bahia, sendo seis portadores de anticorpos IgG (IH e TN) e dois IgM (ELISA e TN). Os autores comentam sobre a circulação deste arbovírus no Estado, e as possibilidades de reações cruzadas com outros vírus antigenicamente relacionados.

Eight antibody anti-Rocio cases, from four distinct cities in the state of Bahia, are described; six of them being carriers of the antibody IgG (HI and NT) and two IgM (ELISA and NT). The authors comment on the circulation of these arboviruses in the state of Bahia and on the possibility of cross reactions with other antigenically related viruses.

Application of an immunoperoxidase monolayer assay for the detection of arboviral antibodies.

An immunoperoxidase monolayer assay (IPMA) was adapted for the detection of antibodies to six arboviruses: three viruses within the flavivirus group (dengue 2, West Nile (WN) and yellow fever) and three in the phlebovirus group (Rift Valley fever (RVF), sandfly fever Naples and sandfly fever Sicilian). Antibody titers of homologous hyper-immune mouse ascitic fluid (HMAF) measured by IPMA were two to eight-fold less than those determined by ELISA. In tests with heterologous HMAF, cross-reactions frequently observed in ELISA, particularly in the flavivirus group, were absent in all IPMA titrations. With human serum samples tested for antibodies to RVF (n = 52) and WN (n = 90), the sensitivity of IPMA as compared with ELISA was 96 and 91%, respectively, specificity of IPMA was 100%. In addition, the IPMA format has several advantages that make it a useful alternative to ELISA for diagnosing arboviral infections under field conditions.

A congenital abnormality of calves, suggestive of a new type of arthropod-borne virus infection.

About 1000 calves with a congenital disease were born in Kagoshima prefecture, Japan, between October 1990 and October 1991, the peaks of the epidemic being in March and July 1991. Of 85 abnormal calves examined pathologically and serologically, 70 appeared to have been suffering from a viral disease. Of these 70 animals, 17 had lesions bearing some resemblance to those of the diseases produced by Akabane, Chuzan, Aino, bluetongue and bovine viral diarrhoea-mucosal disease viruses-diseases known to occur in Kagoshima-but serum samples contained no antibodies to these viruses or to infectious bovine rhinotracheitis virus. This suggested the occurrence of a new type of viral infection in southern Japan. Six of the 17 calves were born dead and the others manifested clinical signs such as weakness, difficulty in sucking, inability to stand, vertigo, opisthotonus, staggering and weak eyesight or blindness. They were of small size and showed domed head, scoliosis, arthrogryposis, maxillary retraction, sunken eye, cataracts, and irregularities and defects of the teeth. At necropsy, almost all cases showed hydranencephaly, and many had cerebral defects and cerebellar hypoplasia or agenesis. Both cerebral and cerebellar lesions were seen in six cases, two of which showed a hypoplastic defect of the brain stem. Histopathological examination of the affected organs revealed gliosis, loss of cerebral parenchyma resulting from dilation of the ventricles, perivascular cuffing with round cells such as lymphocytes and plasma cells, proliferation of blood vessels, thick-walled blood vessels in the brain stem, dilation of mesencephalic aqueducts, cerebellar cortical dysplasia, decreased nerve cells in the ventral horn of the spinal cord, and myodysplasia of skeletal muscle.

Natural killer cells appear to play no role in the recovery of mice from Sindbis virus infection.

Previous studies have suggested that non-specific defence mechanisms may be important in the development of age-dependent resistance to fatal Sindbis-virus infection and in the recovery of adult mice from non-fatal infection. In these studies, natural killer (NK) cell induction was studied in 7-day-old susceptible mice and 28-35-day-old resistant mice. It was found that Sindbis virus infection induced NK cells in both the young and older mice, suggesting that NK cells were not important in the acquisition of resistance to fatal Sindbis-virus infection. Transfer of 10(8) lymph node cells from adult, mice, at the peak of NK cell activity, did not protect young mice from fatal infections, supporting the in vitro findings. The pathogenesis of Sindbis virus infection in C57BL/6J bg/bg (NK-cell deficient) and bg/+ (NK-cell normal) mice was also studied. Despite a defect in the induction of NK cells by Sindbis virus infection in the bg/bg mice, there were no significant differences in the pathogenesis of either peripheral or intracerebral infection in these strains of mice. These studies suggest that although NK cells are induced, they may not be important in the recovery of mice from Sindbis virus infection.

Estudos sorológicos para pesquisa de anticorpos de arbovirus em populacao humana da regiao do Vale do Ribeira. II Inquerito em pacientes do Hospital Regional de Pariquera-Acu, 1980. / Serological studies for the research of arbovirus antibodies in human population of the Ribeira Valley region. II - Survey in patients of Pariquera-Acu Regional Hospital, 1980

Foi realizado inquerito sorologico para pesquisa de anticorpos inibidores de hemaglutinacao de arbovirus em 516 moradores das zonas urbana e rural da regiao do Vale do Ribeira, Brasil, area extensamente coberta de florestas onde ocorreu recentemente uma epidemia de encefalite atribuida ao Flavivirus Rocio. Verificou-se que 24,2% destas pessoas tinham anticorpos IH para um ou mais arbovirus (11,2% para Alphavirus; 13,2% para Flavivirus 4,6% para Bunyavirus Caraparu e 0,8% para outros arbovirus). Alguns dos investigados, sem antecedente de vacinacao contra febre amarela apresentaram anticorpos neutralizantes para o virus da encefalite equina do Leste, St.Louis e da febre amarela, os dois ultimos ainda nao isolados na regiao. A analise das caracteristicas dos individuos com sorologia positiva sugeria que a transmissao de arboviroses nao era fato recente e estava se fazendo em pelo menos 9 municipios da area, nao so no ambiente silvestre como fora do mesmo. Os individuos do sexo masculino e entre estes os que trabalham em pesca, em geral no periodo vespertino e noturno, apresentaram maior risco a infeccoes arboviricas

[Protective and damaging action of cytotoxic T-lymphocytes in experimental tick-borne encephalitis]. / Zashchitnoe i povrezhdaiushchee deistvie tsitotoksicheskikh T-limfotsitov pri éksperimental'nom klershchevom éntsefalite.

The methods of adoptive transfer in vivo and cytotoxic action on virus-infected tissue culture in vitro were used to prove that cytotoxic splenocytes produced in experimental tick-borne encephalitis could have both protective and damaging effects. The protective effect was manifested during the first 24 hours after infection, and the damaging effect on the 6th day after infection. Cytotoxicity splenocytes were identified as T lymphocytes on the basis of their sensitivity to anti-theta serum, resistance to the action of hydrocortisone and their inability to adhere to glass, as well as their pronounced specificity and their limited activity in the allogeneic system.

Further studies of macrophages in relationship to avirulent Semliki Forest virus infections.

The amount of virus in macrophages from normal mice infected in vivo and in vitro with avirulent Semliki Forest Virus A7(74)C1 and virulent L10/C1 has been compared to that in macrophages infected similarly from mice given Myocrisin (colloidal gold) before inoculation. Very high titres of virus were found in all macrophages which had been "blockaded" with Myocrisin up to 10(8.5)/ICLD50/ml with the avirulent strain and up to 10(7.2)/ICLD50/ml with the virulent strain. "Blockade" of the macrophages in this way made the normally avirulent strain virulent. The possible reasons for this are discussed.

Cross protection among togaviruses in nude mice and littermates.

After immunization with Sindbis virus, T-cell deficient nude mice, compared to normal littermates, were equally protected against challenge with Sindbis virus. However, the nude mice showed about one-tenth the protection observed with normal littermates after challenge with Semliki Forest virus at a dose of 100 LD50. This consistent with our previous interpretation that sensitized T-cell populations play a major role in cross protection between the two togaviruses. The remaining low level of specific cross protection in nude mice (detectable only at a challenge dose of 10 LD50) could not be attributed to an anamnestic response of neutralizing antibody to the challenge virus or to an effective antibody-dependent, complement-mediated cytolysis of infected cells in vivo. Other possible compensatory mechanisms to explain the low level of specific cross protection in nude mice are discussed.