Antigenic relationships amongst coronaviruses

Several serological interrelationships between various members of the corona-virus group have been revealed in neutralization, complement fixation, and gel-diffusion tests, using human and hyperimmune animal sera. Several members of this group of human and animal pathogens are shown to cross-react in one or more type of test, but one member, avian infectious bronchitis virus, was shown to be unrelated. Mouse hepatitis virus (MHV₃) was found to be antigenically related to a number of human types of coronavirus. Difficulties were encountered in the investigation of paired human sera in demonstrating the specificity of antibody rises, placing doubt on the values of some serological studies. The significance of these interrelationships is discussed in the light of other investigations.

Serological relationship of the Tacaribe complex of viruses to lymphocytic choriomeningitis virus

By means of the indirect fluorescent-antibody test, cross serological reactivity was demonstrated between lymphocytic choriomeningitis (LCM) virus and the viruses of the Tacaribe complex. Antisera to all members of the Tacaribe complex reacted with LCM virus; LCM antisera gave significant staining of Amapari virus, but minimal or inconsistent reactions with Tacaribe virus, and no reaction with two other viruses of the Tacaribe complex. A low level cross-reaction was observed in complement fixation tests of Machupo and Pichinde antisera against LCM antigen. Immunization with Tacaribe and Amapari viruses did not protect mice against challenge with LCM virus. Because of the identical appearance of the virions, the sharing of antigens, and the many biological similarities between LCM and the Tacaribe complex viruses, it is proposed that they be considered as constituting a new taxonomic group of viruses.

Experimental infection of chimpanzees with the Norwalk agent of epidemic viral gastroenteritis

A fecal filtrate of human origin containing the Norwalk agent of epidemic viral gastroenteritis was administered by stomach tube to chimpanzees in an attempt to induce diarrheal disease. Significant postchallenge serum antibody rises against Norwalk viral antigens were demonstrated in all animals using the techniques of immune electron microscopy and radioimmunoassay. In addition, viral antigens were detected in feces from five of nine animals using radioimmunoassay. Clinical illness characterized by diarrhea and/or vomiting did not occur. Infection was transmitted subsequently by feeding four additional chimpanzees a fecal filtrate prepared from one of the previously infected animals. Development of an antibody response in four animals and detection of viral antigen in two animals that received this passage filtrate indicated that viral replication had occurred in the absence of clinical illness. The availability of the chimpanzee as an experimental animal host susceptible to infection with the Norwalk agent should facilitate the study of epidemic viral gastroenteritis.

Borna disease of horses. An immunohistological and virological study of naturally infected animals

The brains of eight horses that had suffered from natural Borna disease were examined with virologic, immunohistological, and electron-microscopic methods. All brains harbored infectious virus as shown by inoculation of experimental animals. Regional assessment of the infectivity exhibited the highest titers in the hippocampus and piriform cortex and the lowest in the cerebellum. Conventional histology yielded pathologic alterations very similar to those of the classical description of the disease. Immunohistology demonstrated the highest amounts of Borna disease virus-specific antigen in the nuclei of neurons. In the perikarya, dendrites, and axons smaller amounts of antigen were found. A comparison of the antigen distribution with the inflammatory reaction established a high concordance of these two parameters. The presence of virus-specific antigen seems to trigger the exsudation of inflammatory cells, which reflect the extension of the infectious process. Heavy inflammatory exsudates in the white matter underlying diseased cortical areas can be explained by the axonal presence of virus-specific antigen. Virus particles could not be demonstrated with the electron microscope. The most significant findings at the ultrastructural level were stacks of fine filaments, adhering closely to cytoplasmic cisterns. These structures might be related to virus components or might be involved in virus morphogenesis.

Prevalence of antibody to the Norwalk agent by a newly developed immune adherence hemagglutination assay

An immune adherence hemagglutination assay (IAHA) for the detection of antibody to the Norwalk agent of acute epidemic nonbacterial gastroenteritis was developed using as antigen virus purified from stool from an experimentally infected volunteer. The assay was sensitive and specific and was efficient for detecting Norwalk antibody seroresponses. The prevalence of Norwalk antibody in various groups in the United States was studied. Antibody to the Norwalk agent was acquired gradually, beginning slowly in childhood and accelerating in the adult period so that by the fifth decade 50% possessed antibody. This pattern of antibody acquisition contrasted sharply with that for the human rotavirus of infantile gastroenteritis. Rotavirus antibody was acquired during early childhood by almost all individuals in the pediatric groups studied. Antibody to the Norwalk agent was also found in rural Bangladesh; in a small prevalence survey of 39 children and adults 21% possessed Norwalk IAHA antibody, whereas 95% possessed antibody to the human rotavirus.

Preliminary characterisation of torovirus-like particles of humans: comparison with Berne virus of horses and Breda virus of calves

Pleomorphic virus-like particles have been observed by electron microscopy in the faeces of children and adults with diarrhoea. Some of these particles were approximately 100 nm in diameter and had a "fringe" of closely applied peplomers approximately 10 nm long; they closely resembled Berne virus of horses and Breda virus of calves, the two representatives of a newly proposed family called the Toroviridae. In one sample a toroidal nucleoprotein-like structure was observed within the particles. For two samples a buoyant density of 1.14 g/ml was determined by centrifugation through a sucrose density gradient. One sample possessed a haemagglutinin for rat erythrocytes. The serological relationship between these different viruses was observed by immune electron microscopy, haemagglutination inhibition, and serum neutralisation. The role of these virus-like particles as candidate pathogens of humans is discussed.

Rapid diagnosis of rotavirus infections: comparison of electron microscopy and immunoelectroosmophoresis for the detection of rotavirus in human infantile gastroenteritis

Eighty-seven faecal samples from infants and children suffering from acute gastroenteritis were investigated for the presence of rotavirus by immunoelectroosmophoresis (IEOP) and electron microscopy (EM). Sixty-one % of the samples contained rotavirus antigens when examined by IEOP whereas only 50% were diagnosed as positive EM. However, where it was possible to perform EM within the same day that the sample was received it took 24 h to establish the diagnosis by IEOP. The high sensitivity of the IEOP method was achieved by application of antiserum produced in rabbits to rotavirus immunoprecipitates. The specificity and sensitivity of the diagnostic antiserum produced were tested by application of different immunoelectrophoretic methods.

Antigenic and morphological similarities of progressive pneumonia virus, a recently isolated "slow virus" of sheep, to visna and maedi viruses

Progressive pneumonia virus, the causative agent of a slow, pulmonary disease of Montana sheep, was shown to be antigenically related to two other slow viruses of sheep, visna and maedi. Electron microscopic examination of infected cells revealed that the virus matures by a budding process and that the budding particles as well as the mature, extracellular virions bear striking resemblances to the oncogenic ribonucleic acid (RNA) viruses. Recent findings of an RNA-dependent deoxyribonucleic acid polymerase associated with the virions of this group of slow viruses lend further support to the notion that they may tentatively be classified with the oncogenic RNA tumor viruses.

Western blot (immunoblot) assay of small, round-structured virus associated with an acute gastroenteritis outbreak in Tokyo

Small, round-structured virus (SRSV) was detected in a stool specimen of a patient during an acute gastroenteritis outbreak in Tokyo and was tentatively named SRSV-9. SRSV-9 was purified by sucrose velocity gradient centrifugation after CsCl density gradient centrifugation. The buoyant density of SRSV-9 appeared to be 1.36 g/ml in CsCl. A Western blot (immunoblot) assay using the biotin-avidin system revealed that SRSV-9 was antigenically related to the Hawaii agent but distinct from the Norwalk agent and contained a single major structural protein with a molecular size of 63.0 +/- 0.6 kilodaltons. The prevalence of SRSV-9 infection in Tokyo was surveyed by the Western blot antibody assay by using a crude virus preparation as the antigen. Seroconversion was observed in 56.5% of the patients involved in the outbreaks from which SRSV was detected by electron microscopy.

Eradication of Aleutian disease of mink by eliminating positive counterimmunoelectrophoresis test reactors

The counterimmunoelectrophorsis test was applied on three Aleutian disease virus-infected mink ranches for the detection of specific Aleutian disease virus antibody. All mink on the ranches were tested during the pelting season and before the breeding season for 4 consecutive years. Aleutian disease has been eliminated from the three commercial mink ranches by culling out all mink that were positive for Aleutian disease virus antibody.

Lymphocytic-choriomeningitis virus in hamster tumor: spread to hamsters and humans

A passage line of a spontaneous hamster fibrosarcoma is contaminated by the virus. of lymphocytic choriomeningitis. Tumors from animals receiving implants when newborn contain high titers of infectious lymphocytic-choriomeningitis virus and complement-fixing antigen, and hamsters receiving implants when weanlings develop high titers of complement-fixing antibody against lymphocytic-choriomeningitis virus. In contrast with the specific reactions of tumorous hamsters to the initiating virus in virus-induced tumors, the development of complement-fixing antibody to lymphocytic-choriomeningitis virus does not depend on the development of tumors. Infant hamsters bearing the tumor have a generalized subclinical infection and seem able to spread virus to other hamsters and to humans.

Oyster-associated gastroenteritis in Australia: the detection of Norwalk virus and its antibody by immune electron microscopy and radioimmunoassay

Following widespread outbreaks of oyster-associated gastroenteritis in Australia during 1978 in which Norwalk virus was implicated as the causative agent, collaborative studies were undertaken between laboratories in Australia and the United States to confirm the etiology. Immune electron microscopy (IEM) techniques were used in Australia and radioimmunoassay (RIA) methods in the United States. Norwalk virus was detected by IEM in seven of 15 faecal samples, and four were positive by RIA. A much better correlation was found with antibody determinations. Both methods demonstrated significant increases in antibody to Norwalk virus in 22 of 30 sets (73%) of "acute" and "convalescent" sera, confirming that Norwalk virus was responsible for the majority of cases. It is significant that the RIA serology was determined using Norwalk antigen originating in the United States and the IEM serology was determined using 27--30-nm particles originating in Australia.

Enzyme-linked immunosorbent assays for Snow Mountain and Norwalk agents of viral gastroenteritis

Enzyme-linked immunosorbent assays (ELISAs) for antigen detection and blocking ELISAs for serum antibody rises were developed for the Snow Mountain and Norwalk agents of viral gastroenteritis. The ELISAs were as sensitive as the existing radioimmunoassays and were specific for the Snow Mountain or Norwalk agent. The blocking ELISAs detected the same number of significant rises in antibodies to these agents as did the existing blocking radioimmunoassays.

Antigenic variation in strains of avian infectious bronchitis virus

Fifteen british field strains of IBV were compared using cross serum neutralization tests in embryonated eggs with seven standard reference strains of IBV. While the British field strains were considered to form a relatively homogeneous group considerable antigenic variation did occur. It was considered that it was not feasible at this time to describe accurately a serotype classification for IBV, similar to that described for other virus groups.

Characterization of the Kilham rat virus

Kilham rat virus (KRV) was found to grow in a rat nephroma cell line and to form plaques on secondary rat embryo monolayers. The virus was purified by enzymatic treatment and isopycnic cesium chloride sedimentation. KRV bands at a density of 1.41 g/cm(3) in cesium chloride. It contains about 26.5% deoxyribonucleic acid (DNA). The sedimentation coefficient S(20,w) in sucrose gradients was 122 corresponding to a molecular weight of 6.6 x 10(6) daltons. The reaction of formaldehyde with the KRV virion suggests that the DNA in situ is single-stranded. DNA extracted from KRV had a buoyant density of 1.715 g/cm(3) in cesium chloride. The S(20,w) was determined in sucrose gradients to be 16, and the molecular weight was calculated to be approximately 1.7 x 10(6) daltons. The base composition of the DNA is 26.7% adenine, 30.8% thymine, 20.0% guanine, and 22.5% cytosine. On the basis of its noncomplementary nucleotide ratio, melting curve, and the reaction with formaldehyde, the DNA of KRV is believed to be single-stranded.

Pathogenesis of aleutian disease of mink: identification of nonpersistent infections

Aleutian disease virus usually produces a persistent infection and progressive immune comples disease in mink of the Aleutian genotype. Study of Aleutian disease virus infection in non-Aleutian mink showed that about one-quarter developed nonpersistent infections by the virus, and that the nonpersistence was not genetically determined by the host. The nonpersistently infected mink developed only a transient elevation of serum gamma globulin, and much lower specific Aleutian disease virus antibody titers than persistently infected mink. No lesions were found in the nonpersistently infected mink.