Sven Gard

Immuno-inactivation of poliovirus

The term immuno-inaotivation as distinct from neutralization is used to designate a technic by which the reaction between virus and antibody as well as by this reaction possibly induced changes in the virus are allowed to proceed to completion after which the residual virus activity is determined. The degree of inactivation was found to be inversely proportional to the amount of virus added. Maximum sensitivity wan thus obtained when the virus dose was reduced to the lowest possible limit. With due regard to this fact the technic was found to be 100 times more sensitive than the conventional neutralization test.

THEORETICAL CONSIDERATIONS IN THE INACTIVATION OF VIRUSES BY CHEMICAL MEANS

On the basis of chemical studies undertaken following the first successful purification experiments, viruses generally were considered to represent giant nucleoprotein molecules. In the virus particle a distinct architecture on a supramolecular level is recognizable, apparently reflected in functional differentiation as well. In principle, all viruses thus far studied consist of a core of nucleic acid (NA), or sometimes nucleoprotein, encased in a shell of non-NA matter, chiefly protein. In several viruses the NA has been shown to carry all the genetic information needed for multiplication of the virus within its host cell (Gierer and Schramm, 1956). Whether the same is true of all viruses must be left an open question for the time being. Efforts to produce an active NA from myxoviruses have failed notoriously. The reason for this is not known-it may be failure to introduce the NA into the cell or it may be that the protein plays a significant part in the intracellular virus synthesis. At all events, it seems safe to assume that an active NA is a necessary condition for virus multiplication, and that damage to the NA will incapacitate completely the virus as an infectious agent. The protein coat seems to have several important functions: (1) By its often remarkable resistance to chemical and other agents the protein coat serves to protect the NA, which is quite labile in the free state. (2) In some viruses a surface protein is the carrier of highly specific receptor mechanisms by which the entrance of the virus into the host cell is mediated. I t is also probable that the protein facilitates infection by viruses in which specific receptor mechanisms have not yet been demonstrated. ( 3 ) More hypothetical is the possibility that some protein constituent participates in the initiation of the intracellular process. Recent observations indicate that the protein enclosed in the head of bacteriophage particles may have such a function (Spizizen, 1957). The reconstitution of plant virus NA by addition of protein, described by Fraenkel-Conrat and Williams (1935), may point in the same direction. Apparently, a true inactivation of a virus particle, that is, a complete destruction of infectivity and capacity of multiplication, must include an irreversible change in its NA. Until recently inactivation of the NA was generally considered to be a one-hit, all-or-none phenomenon, referable to essential sites in the molecule. Most probably, however, the concept of particular chemical groups as carriers of the biological activity represents an oversimplification of the problem. I t seems more reasonable to regard activity as an expression of a complicated pattern of forces, determined by the structure of the molecule a5 a whole. Any particular site is essential only as part of the pattern, and any chemical alteration is important only insofar as it significantly modifies the field of forces. For example, an amino group might be essential only because,

The use of guinea pigs in tests for immunogenic capacity of poliomyelitis virus preparations.

The guinea pig, although apparently resistant to poliomyelitis virus infection, responds to inoculation of living or formol inactivated virus with the formation of neutralizing antibodies. The strenght of the reaction seems to be independent of whether the virus is active or not and, thus, correlated to the administered amount of antigen only. Determination of the minimal amount necessary to elicit antibody formation (extinction limit titration) seems to be a reliable method for assay of immunogenic capacity. Different strains of virus possess widely varying immunogenic capacities. The ratio of infectivity to extinction limit titer (immunogenic index) is an adequate measure of this quality. The importance of selecting for vaccine production Strains of great immunogenic capacity is emphasized.

Measles Vaccination VI. Serological and Clinical Follow‐up Analysis 18 Months after a Booster Injection

Twenty‐one children given three monthly doses of a formalin‐killed vaccine at the age of ½ to 2 years and a booster of the same product or purified hemagglutinin 22 months later were submitted to a serological and clinical follow‐up 18 months after the booster.

Inactivation of Poliovirus by Formaldehyde. Analysis of Inactivation Curves.

As previously reported the equation logy 0 − logy=ta log (1+b t) has been found to describe the course of inactivation of poliovirus by formaldehyde. The present paper reports and discusses different methods of fitting this equation to experimental data. With the aid of the methods described data recently published byHaas et al. and byTimm et al. are analyzed. Those ofHaas et al. show an extraordinarily good fit and, thus, confirm our previous findings. On the other hand, the data ofTimm et al. do not fit the formula. Attention has been directed to certain inadequacies in the technic applied by these authors which seem to offer a plausible explanation for the discrepancies in results.

THE ULTRASTRUCTURE OF CANINE DISTEMPER VIRUS.

The ultrastructure of distemper virus was studied in the electron microscope by use of the negative staining technique. The structure was shown to be generally similar to that of measles, rinderpest and large myxoviruses. The intact virus particles measured 1150 to 2300 å in diameter and a marked pleomorphism of particles was observed. The marginal structure was constituted by a double-contoured membrane with a width of 75–85 å from which extended rather symmetrically arranged club-shaped surface projections with a length of 130 å. An inner component with a probably helical symmetry and a cross-section diameter of 180 å was demonstrable. The presence of filamentous forms and doughnut-shaped particles was also observed.

Studies on the etiology of epidemic pleurodynia (Bornholm disease). I. Clinical and virological observations.

The clinical picture in 28 patients treated for pleurodynia or suspected pleurodynia is briefly described. The incidence of recurrences, dry pleuritis and meningitis was high. Examination of spinal fluid, throat samples and stool specimens were carried out in 20 cases. In 7 of these strains of Coxsackie virus were isolated. Stools were positive in all 7 cases, throat swabs in 2 and spinal fluid in one case. Neutralizing antibodies against the strains isolated were present in convalescent sera in all cases. A certain evidence is presented to show that the virus found was of etiological importance.

L'épidémiologie et la prévention de certaines maladies à virus entériques et respiratoires

Thanks to Professor Debrd, his acute sense of what needs to be discussed and his careful planning and organization, the Seminars at Longchamp have become a widely respected European institution, of great profit to all who are fortunate enough to be able to participate. The most ample way to pay homage and express our grati tude to our host and, I am sure, the one most appreciated by him, is to make this Seminar as successful as the previous ones. This t ime we are going to deal with epidemiology and prevention of certain virus diseases. The field to be covered is a meeting ground for clinicians, virologists and public health specialists. I t is important , throughout our discussions, to remain within the boundaries of the common terri tory; to speak a language, intelligible to everybody; to avoid subjects which, however interesting to the specialists, may yet be of limited general significance. From long experience I know tha t I should turn particularly to my fellow virologists with this request: discussion of intricate, purely virological problems will have to be saved for another occasion. Virus classification and nomenclature is one such question. A new nomenclature system for the enterovirus group has recently been proposed and already caused a certain controversy. In drawing the agenda for the Seminar we had to use some virus names and to group and subdivide the topics somehow. Preference had to be given to clinical and epidemiological aspects. Thus, the use of the terms ECHO and Coxsackie viruses or the subdivision of enterovirus infections in respiratory and intestinal should be regarded only as a mat ter of convenience and not as a mat te r for discussion. With this explanation I ask you to accept the agenda as they stand.

A note on the morphology of rubella virus

I t is only recently tha t the long-standing assumption of a viral etiology of rubella was substantiated by the isolation, successful propagation in tissue culture and immunological identification of the responsible agent (1--3) . Weller and Neva (3) described a specific, mild and limited cytopathic effect but otherwise the main manifestation of infection of tissue cultures was the development of resistance to snperinfection with ECHO 11, or Sindbis virus. The present communication reports preliminary results of electron optic studies on infective tissue culture material. Our strain of virus was kindly provided by Dr. J. L. Sever, National Insti tutes of Health, Bethesda, Md.~ Isolated from the throat of a 6 year old boy, it was received in its 5th passage in grivet monkey kidney cultures. Material from 5 further passages in the same type of cells was used in the present study. Demonstration of virus growth by challenge infection with ECHO 11 virus, virus titrations and neutralization tests were performed mainly according to the technique described by Parkman et al. (1, 2); details will be published later. Titers of about 104 TCD~0/ml. were obtained. Preliminary tests indicated a very low density of the virus, since it did not sediment in a sucrose solution of density 1.12 g/m1. Accordingly preparation for electron microscopy was carried out as follows. Tissue cultures were harvested about l0 days after inoculation. After two cycles of freezing and thawing the fluid was clarified by centrifugation (20 minutes at 1000 r. p. m.) and concentrated 10 to 20 times by dialysis against Carbowax 20 ML (Union Carbide Chemicals Co.). The

The Etiology of Acute Aseptic Meningitis (Wallgren)

At the time when Wallgren coined the term “acute aseptic meningitis” (1924) virus research was still in its very beginning. On purely clinical grounds Wallgren made his distinction. Later development showed that the etiology in the vast majority of cases should be sought among the viruses. To‐day it is often possible to make a specific diagnosis. In the following paper Professor Gard discusses this fact with special emphasis on the importance of the Coxsackie group of viruses.