Björn Bloth

Ultrastructure of gamma-M immunoglobulin and alpha macroglobulin: electron-microscopic study.

Electron microscopy of purified Waldenstr�m macroglobulins and normal human and rabbit γM immunoglobulins revealed spider-like structures with five legs varying in length and often joining a central ring. Usually only the central more rigid part of this structure (about 150 by 170 angstroms) was clearly visible, but occasionally particles were seen with longer very flexible legs having a total span of about 350 angstroms. Molecules of γM antibody retained antibody activity during preparation for electron microscopy. Human and rabbit alpha macroglobulins revealed more rigid symmetric structures (100 by 200 angstroms) which resembled the Russian letter .

Examination of virus-γM antibody complexes by electron microscopy I. Configuration of γM antibodies and mode of attachment to antigen☆

Abstract Poliovirus-γM antibody complexes were examined by the negative staining technique in the electron microscope. The virus was purified by equilibrium centrifugation, and rabbit γM antibodies by zone centrifugation or gel filtration. The specificity of the poliovirus-γM antibody reaction was established by the use of heterologous antigen and γM fractions from normal sera. N- and H-virus particles aggregated separately in the presence of γM antibodies against both these antigens. The size of specific poliovirus aggregates and the density of the cross-linking network of γM antibodies increased as the relative γM antibody concentration went up. With intermediate or high relative antibody concentrations single virions or virions in the periphery of aggregates were often surrounded by an aura of loops. The maximal length of the turn of the loops was 220–250 A and their width 35–40 A, suggesting that they represented γG-like 7 S subunits of the γM molecule. The maximal number of subunits contained in one γM molecule appeared to be 5 or 6. The distribution of the lengths of γM antibodies bridging virions had a mode and median of about 330 A and maximal value of 360–370 A.

Electron microscopic analysis of the internal component of respiratory syncytial (RS) virus.

The internal component of RS virus has been examined in the electron microscope by using the negative contrast technique. It was found that this component when being well preserved, exhibited a “herring-bone”-like structure similar to the one characteristic of paramyxoviruses. The diameter was about 170 Å and a regular periodicity of about 70 Å was found along the axis. Unwound structures suggested the internal component to be single-stranded.

The ultrastructure of respiratory syncytial (RS) virus

I t has been suggested that RS virus should be included among the large myxoviruses (1, 2). Somewhat in contrary to this, data given by Armstrong et al. (3) indicate the presence of virus particles with a diameter of 60--70 m~z in ultrathin sections of infected tissue cultures. The particles consisted of an elec~rondense central core, surrounded by an envelope. Spherical as well as elongated forms were demonstrated. In the present study, the negative staining technique of Brenner and Home (4) was used to obtain further information about the fine structure of the virus particles. The Long strain of RS virus, supplied by American Type Culture Collection, was used and propagated in HEp-2 cells. The titers reached were ~bout 106.o TCID/1.0 ml. of material harvested at the stage of maximum cytopathic effect in the cultures. After clarification of the crude suspension by centrifugation at 3000 r. p. m. for 30 minutes the material was concentrated by forced dialysis. Further purification and concentration was achieved either by centrifugation on a 30~o sucrose solution as described previously by Norrby et al. in connection with canine distemper virus (5), or only by centrifugation at 20,000 r. p. m. for 1 hour. The pellets obtained were resuspended in a 1% ammonium acetate solution and mixed with an equal volume of a 2% solution of phosphotungstie acid (PTA) ajusted to pH 6.5 with N KOH. A drop of this mixture was applied directly on to a grid with a carbon coated formvar film. Excess fluid was sucked off with a filter paper and the preparation left to dry

Morphology of Subunits of Respiratory Syncytial (RS) Virus. (Brief Report.).

In a previous report (1) the ultrastructure of Respiratory Syncytial (RS) virus as revealed by the negative staining technique was described. Structural similarities to myxoviruses were found. The present paper describes the ultrastructure of viral subunits prepared by t reatment of purified virus preparations with Tween 80, either alone or in combination with ether. Special at tention was paid to the internal component of the virus, since the morphological features of this structure have been considered to be of taxonomic importance (2, 3). The Long strain of RS virus propagated in t tep-2 cells and concentrated by forced dialysis against polyethylene glycol was used as in previous studies (1). Purification of intact and almost intact virus particles was obtained by a technique which will be described in detail in a forthcoming paper. Briefly this comprises a centrifugation at 20,000 r. p. m. for 60 minutes (Rotor SW 39, Spinco) of concentrated tissue culture material layered on a stratified CsC1 solution containing two layers with densities of 1.10 and 1.26 g./cc, respectively. Material accumulating in the interface between the two layers carried all infectivity and about 10-20 ~o of the total complement fixing activity. This material was examined either in its crude form or after t reatment with Tween 80 and ether according to the technique used for measles virus (4). The material to be studied was dialysed against a

Fractionation of respiratory syncytial (RS) virus components by centrifugation techniques.

After equilibrium centrifugation in CsCl gradients of concentrated RS virus material, infectious particles were recovered in fractions with densities varying between 1.21 to 1.23 g/cc., whereas CF antigen activity mainly accumulated in the density range 1.25 to 1.34 g/cc. Small quantities of CF antigens also appeared at lower densities. Treatment with Tween 80 and ether eliminated all infectivity without a concomitant destruction of CF antigen. The buoyant density distribution of CF activity in such a preparation was identical with that of untreated material except that all low density (1.25 g/cc.) activity had disappeared. Centrifugation of virus material layered on top of a discontinuous CsCl gradient revealed the presence of two populations of particles. One represented rapidly sedimenting particles carrying all infectivity and about 10% of the total CF antigen activity. The other carried all of the remaining CF antigen activity and had the character of a soluble antigen.