RESUMEN

From July to September 1999, a widespread outbreak of meningoencephalitis associated with West Nile virus (Flavivirus, Flaviviridae) occurred in southern Russia, with hundreds of cases and dozens of deaths. Two strains of West Nile virus isolated from patient serum and brain-tissue samples reacted in hemagglutination-inhibition and neutralization tests with patients' convalescent-phase sera and immune ascites fluid from other strains of West Nile virus.

Asunto(s)

RESUMEN

Time-resolved fluoroimmunoassay (TR-FIA) was used for the first time for evaluation of infestation of ixodid ticks with tick-borne encephalitis virus. Comparison of TR-FIA results with those obtained in enzyme immunoassay and by virus isolation confirmed the high efficacy of the method in question. Positive results of TR-FIA coincided with the data of virus isolation in 83.6% cases, the level of false-negative results did not exceed 1.2%, the overall time consumption amounted to about 1.2 hr.

Asunto(s)

RESUMEN

The antigenic structure of 5 strains of tick-borne encephalitis (TBE) virus and 7 other viruses of the TBE complex was examined by the highly sensitive and specific technique of time-resolved fluoroimmunoassay (TR-FIA). A collection of 8 monoclonal antibodies to the Austrian strain. Neudörfl, was used in this study. The findings demonstrate the uniformity of the antigenic structure of TBE viruses from different geographic regions of the USSR. In addition, an epitope was detected which is characteristic of western variants of TBE virus, and another epitope was detected which permits the differentiation of the east-Siberian strain, Aina, from other TBE virus strains. The unique nature of Skalica virus was confirmed, and its similarity, but not identity, to Langat TP-21 virus was shown. Substantial variability in the antigenic structure of some TBE complex viruses was also demonstrated.

Asunto(s)

RESUMEN

Blood samples from 160 inhabitants of the Republic of Bangladesh were studied by haemagglutination inhibition (HI), indirect HI, and radial haemolysis in gel tests. The sera were found to contain antibodies to the arborviruses of Sicilian (6.25%) and Naples (1.25%) sandfly fevers and to the Karimabad virus (11.25%) which are transmitted by Phlebotomus papatasi. Antibodies to the Karimabad virus were found among the Bangladesh population for the first time.

Asunto(s)

RESUMEN

Radial haemolysis in gel was successfully used for the detection of antibody in convalescents after laboratory infection with Venezuelan equine encephalomyelitis (VEE) virus at remote intervals after infection (up to 23 years). The antibodies reacted only with VEE antigen but not with Sindbis and Chikungunya alphavirus antigens. Radial haemolysis in gel was sensitive as the haemagglutination inhibition test but the antibody could be titrated by the diameter of the haemolysis zone omitting the serum dilutions. Slight deviations in the virus dose used for sensitization of erythrocytes or in pH values were not critical. For the test, the sera were heated at 56 degrees C for 30 min. Both sera stored for long periods and those collected on paper disks could be used.

Asunto(s)

Asunto(s)

RESUMEN

The family Bunyaviridae comprises over 200 viruses (serotypes, subtypes, and varieties) that infect vertebrates and/or invertebrates. Four genera of viruses have been defined (Bunyavirus, Nairovirus, Phlebovirus, and Uukuvirus). The main characteristics of the member viruses are: (i) the virus particles are for the most part uniformly spherical, 80-110 nm in diameter, and possess a unit membrane envelope from which protrude polypeptide spikes 5-10nm long; (ii) the viruses have three helical nucleocapsids, often in the form of supercoiled circles, each consisting of a single species of single-stranded RNA, major nucleocapsid polypeptide, N, and at least in some cases minor amounts of a large polypeptide which may be a transcriptase component; (iii) the genome is composed of three species of RNA (L, large; M, medium; and S, small), organized in end-hydrogen bonded circular structures; (iv) most viruses have three major virion polypeptides (N, and two surface polypeptides, designated G1 and G2); (v) for at least some member viruses, the virions have been shown to contain an RNA-directed RNA polymerase, believed to be responsible for the synthesis of viral complementary mRNA, so that bunyaviruses are considered to be negative-stranded viruses; (vi) at least some bunyaviruses are capable of heterologous virus genome segment reassortment and can form recombinant viruses at high or low frequency; (vii) viruses appear to mature primarily at smooth membrane surfaces and accumulate in Golgi vesicles and saccules, or nearby; (viii) transovarial, venereal and/or transstadial transmission in arthropods has been shown to occur for some members of the family.

Asunto(s)

RESUMEN

Radial hemolysis-in-agarose gel (HIG) with members of the genera Alphavirus and Flavivirus is described. The test can be reproduced with goose and sheep erythrocytes sensitized at the optimal pH for each virus. Human (O group), rooster, guinea pig, mouse and hamster erythrocytes were found to be unsuitable. The titer of immune ascitic fluids in HIG coincides with the titer in hemagglutination inhibition. Investigation of convalescent sera after laboratory infection suggests the possiblity of HIG application for serologic diagnosis of arbovirus infection.

Asunto(s)

RESUMEN

Optimal conditions of radial haemolysis in gel (HIG) with Chikungunya (Chik) and Japanese encephalitis (JE) viruses were developed and compared with those of rubella virus. Sheep erythrocytes were found preferable for HIG with Chik and JE viruses, unlike rubella virus, where goose erythrocytes gave best results. Rooster erythrocytes were completely negative in the Chik and JE HIG, again differing from rubella virus, which was practically as good with rooster as with goose erythrocytes. Sheep erythrocytes with rubella virus gave incomplete reactions in HIG. Sensitization of erythrocytes with JE and Chik viruses is better, when borate-phosphate, and not phosphate buffer, is used. Optimum pH values for both viruses should be regarded. Sucrose-acetone, freon and borate-saline antigens from infected mice brain may be used for HIG with Chik and JE viruses.

Asunto(s)

RESUMEN

A rapid method has been developed to detect Bhanja virus in experimentally infected Hyalomma asiaticum ticks by an indirect hemagglutination test. The titer of viral antigen is suspensions prepared from infected ticks ranged from 1:640 to 1:2,560; the antigen was demonstrated in both unfed and engorged ticks during an observation period from 2 weeks to 5 months after infection. The test is simple, easily reproduced, highly sensitive and specific, and may be useful for field studies with Bhanja virus.

Asunto(s)

Asunto(s)

Asunto(s)

RESUMEN

The family Togaviridae is described; it contains four genera--Alphavirus, Flavivirus, Pestivirus and Rubivirus--and additional members. The main characteristics of the family are as follows: single-stranded, linear RNA, molecular weight about 4 X 10(6). Virions have isometric nucleocapsids surrounded by a lipoprotein envelope containing host cell lipid and virus-specified polypeptides including one or more glycopeptides. Virions yield infectious RNA. There are at least 80 members; all the alphaviruses and most flaviviruses are arboviruses in the biological sense.

Asunto(s)

RESUMEN

A persistent lymphocytic choriomeningitis virus, noninfectious for mice, was revealed in the continuous human cell line, Detroit-6. The virus was detected in the cell monolayer by an indirect immunofluorescence test and in the cell homogenate by a complement-fixation test. Between 30 and 80% of the cells produced viral antigen in subsequent passages of the culture. Thymidine analogues (BrDU and IDU) stimulated the synthesis of antigen. DNA of the persistently infected cell line was transfected to the mouse lymphoid cell line, L1210, which became persistently infected with the virus.

Asunto(s)

RESUMEN

Sucrose-acetone suckling mouse brain antigens of Na-kayama NIH, JaGAr-01 and Peking-1 strains of Japanese encephalitis (JE) virus treated with beta-propiolactone (BPL) retained their ability to specifically react in haemagglutination inhibition (HI) tests with antibody to JE virus, as demonstrated with convalescent sera. BPL treatment abolished the infectivity but did not affect the haemagglutinating activity of the virus of the pH optimum of the haemagglutination (HA) test.

Asunto(s)

RESUMEN

Immune sera to the envelope and nucleocapsid components of Zaisan 260 and R 16225 strains of Semliki Forest virus (SFV) were prepared with the use of disrupted, partially purified virus.

Asunto(s)

RESUMEN

The sedimentation coefficient of Zaysan virion ribonucleic acid (RNA), estimated by sucrose density gradient centrifugation, was 42 S. Pancreatic ribonuclease digested the viral RNA to acid-soluble fragments. Two viral structural proteins with apparent molecular weight of 50,000 and 30,000 daltons were identified by polyacrylamide gel electrophoresis. A dense, RNA-rich particle, containing the smaller polypeptide, was isolated after mild detergent treatment of Zaysan virus.

Asunto(s)

RESUMEN

A new family is described, the Bunyaviridae, which contains a single genus, Bunyavirus. The main characteristics of the family are as follows: single-stranded RNA, total molecular weight about 7 X 10(6) daltons, probably in three segments. Virions spherical, enveloped particles 90-100 nm in diameter. Envelope contains at least one virus-specified glycopeptide. Develop in the cytoplasm, mature by budding into smooth-surfaced vesicles in the Golgi region or nearby. Internal ribonucleoprotein composed of long strands 2-2.5 nm broad. There are at least 150 members, 87 serologically related bunyaviruses and other probable bunyaviruses.

Asunto(s)

Asunto(s)

Asunto(s)