Juanita Dennis

A plaque assay for rubella virus based upon hemadsorption.

Summary A plaque assay for rubella virus was developed using hemadsorption of pigeon erythrocytes to demonstrate foci of infected cells. Tests conducted by this method can be completed more rapidly than previously-described plaquing procedures based upon a cytopathic effect of the virus, and they are not beset with the variables inherent in interference technics. The number of plaques demonstrable by hemadsorption was proportional to the concentration of virus used to infect the cells, indicating that each plaque was produced by a single infectious particle. Infectivity titers of rubella preparations obtained by plaque assays were comparable to those obtained by the interference technic. Rubella antibody could be assayed by a plaque reduction technic, and plaque production could be used to detect small amounts of virus at low passage levels of field strains of rubella virus.

Hemadsorption and hemadsorption inhibition tests for rubella virus

A hemadsorption (HAd) reaction was demonstrated in rubella-infected cell cultures using erythrocytes of 1-day-old chickens, adult chickens, pigeons, geese, sheep or bovines. HAd occurred at 4°C, room temperature or 37°C, and at a pH of 6.2 or 7.4. BHK-21 cells were the most satisfactory for demonstrating HAd; the reaction could be demonstrated only in heavily-infected cultures of other cell types. Infected BHK-21 cell cultures generally had to attain infectivity titers of 10−3.5 to 10−4.0 InD50 per 0.1 ml in order for HAd to be demonstrable. The HAd reaction could be used to detect unneutralized virus in neutralizing antibody assays, and the inhibition of HAd in infected cell cultures was a very sensitive method for assay of rubella antibodies. A procedure was developed for identification of rubella virus isolates by HAd inhibition.

The Price virus: an unclassified enterovirus isolated from patients with central nervous system disease.

Summary Six immunologically related viral strains have been recovered from the stools of patients with CNS disease. Neutralization tests indicate that they are not polioviruses, group A or group B Coxsackie viruses, ECHO virus types 1-28 or one of 4 ECHO candidate strains. The human origin of these agents is evidenced by the fact that 5 of the 6 patients with isolations showed 4-fold or greater rises in neutralizing antibody to these viruses. The several strains possess the characteristics of human enteroviruses, i.e., ether resistance, particle size, and production of a characteristic “enterovirus cytopathic effect” in monkey kidney cell cultures. All of the strains could be adapted to growth in HeLa cells. They are not pathogenic for suckling mice, and do not agglutinate human group O, chicken or guinea pig erythrocytes. Addendum Since this paper was submitted for publication, information from Dr. H. A. Wenner, as well as the results of tests performed in this laboratory, indicates that the Bastianni, PR-17 and Frater viruses (enterovirus candidates) are related to the Price virus.

Complement-Fixing Antibody Responses to ECHO Virus Types 12 and 19 of Patients with Enterovirus Infections.

Summary Sera from 167 patients with various enterovirus infections were tested against uninactivated CF antigens to ECHO virus types 12 and 19. Four-fold or greater rises in CF antibody titer, unassociated with the presence of neutralizing antibody to these 2 ECHO virus types, were seen in an appreciable proportion of patients infected with ECHO 4, 6, 9 and 11 viruses, possibly indicating antigenic relationships of the viral moieties responsible for production of CF antibodies in man. No evidence was seen of a relationship between ECHO types 12 and 19 and ECHO 5, ECHO 10 (reoviruses) or ECHO 14, nor was there any good evidence of a relationship between these 2 ECHO virus types and the Coxsackie group A, Coxsackie group B or poliovirus types studied.

ANTIGENIC RELATIONSHIP BETWEEN ECHOVIRUS TYPES 29 AND 32.

Summary An antigenic relationship has been demonstrated between the newly classified echovirus types 29 and 32. The amount of crossing seen in conventional tube neutralization tests was relatively minor, but fairly high reciprocal titers were observed in plaque reduction neutralization tests. In cross hemagglutination-inhibition and complement fixation tests these two viral types were virtually indistinguishable. The question arises as to whether these two new echovirus types should be classified as distinct immunotypes or whether they represent antigenic variants of a single viral type.