Evening Republican, Volume 20, Number 269, Rensselaer, Jasper County, 9 November 1916 — NEW METHOD OF MAKING SERUM [ARTICLE]

NEW METHOD OF MAKING SERUM

Specialists Find Way to Produce a Clear Sterilised Product Free From Feet and Mouth Virus A new method of preparing anti-hog cholera serum, which permit a the economical production of a clear sterilized product, has just been described in the Journal of Agriculture Research o« the U. S. Department of Agriculture. The ad> antage claimed for the new method is that it makes possible the producllun of an anti hog cholera serum which can be quickly sterilized by heat to a point that will absolutely kill any germs of foot and mouth disease and so >ield a serum that is absolutely safe even if taked from a bog which might harbor foot and mouth disease and yet give no indication of being infected. The method as described by its discoverers, Dr. Marion Dorset and R. R. Henley, of the Biochemic Division, Bu reau of Animal Industry, consists in adding a slight amount of an extract from ordinary white navy beans to the defibrinated hog cholera immune blood which has been the form of the serum used in the past. The addition of this bean extract causes tire red cells of the blood to agglutinate and when the mixture is whirled on a centrifuge the red cells pack together and form a rather stiff jelly like mass, it is then possible to pour off a clear serum, leaving behind the red ceils which play no part in preventing hog cholera and which in fact simply tend to dilute the serum and render its sterilization by heat impracticable. To increase the yield of clear serum the discovers added a small amount of ordinary salt and found that they obtained from 70 to 74 per-cent of clear serum. The clear serum thus obtained it was found could be heated for 30 minutes at a temperature of 60 degrees centigrade without changing its consistency or lessening in any way its effectiveness in preventing hog cholera. The heating to this point for this time is more than sufficient to kill any germs of foot and mouth dis ease which might accidentally be pres /tat tests wWi hogs, show thafpFobably all the anybodies useful {combating hog cholera were retained in the serum and the red cells extracted contained so few, if any, of these valuable bodies as to make the residue of red cells useless in prevent ing the disease. Before the clear serum was-develop-ed, many attempts were made to Her, illze by heat in a practicable way "the ordinary defibrinated blood. It was found, however, that heating the old product up to 60 degrees Centigrade resulted in more or less complete coagulation of the defibrinated blood and in the destruction of the serum so far as its commercial worth is con cerned. It was found that the highest temperature that could be used w-as 50 degrees centigrade and it was necessary to keep the old serum at this temperature for twelve hours to make certain that the virus of foot and mouth disease was killed. Heating serum at a steady temperature over this long period of ordinary practice is difficult and too expensive. Attempts also were made to make

a clear serum by centrifugal zing. IT was found, however, that while the centrifuge would separate to some extent the red cells, they were in such shape that it was difficult to separate the serum completely.An important quantity of antibodies were left behind in the red clot, and the resulting product was a cloudy rather than aclear serum. With this process, moreover, it was possible ordinarily to secure only about 50 per cent of <-erii?tL_ Under the new method it is possible to secure as high as 74 per cent of clear serum, which in actual test has proved to be fully potent. This clear serum, moreover, can be completely sterilized in 30 minutes, whereas the old serum had to be heated steadily for 12 hours. The new form of serum as far as the Department knows is not yet being made or put on sale by the commercial serum laboratories. As this process was discovered by the Federal government, any one in th[e United States is free to use it.