AUSTRALIA ANTIGEN, HEPATITIS VIRUS AND DOWNS SYNDROME *

Australia antigen, originally detected in the serum of an Australian aborigine,l is now known to be associated with viral hepatitis.z-s A series of studies have been completed to test the hypothesis that Australia antigen (abbreviated Au( 1) ) is, or is located on, a virus which causes hepatitis in some people infected with it. The evidence in support of this hypothesis, which is given in detail e l~ewhere ,~~ 6, 7 can be summarized as follows: ( 1 ) Australia antigen is associated with acute hepatitis. (2) Au( 1) is associated with chronic hepatitis. ( 3 ) Isolated Au( 1) has the appearance of a virus (200 A in diameter) under the electron microscope.* (4) Using fluorescent anti-Au( 1 ) , Australia antigen has been identified in the nuclei of the liver cells of patients with hepatitis and Au(1) in the peripheral blood; this is generally not seen in appropriate cont r o l ~ . ~ , lo (5) Australia antigen present in the blood of donors can be transmitted by transfusion to patients.11-13 The amount of Australia antigen which develops in recipients of blood is greater than that transfused. Some of the patients to whom the Au( 1) is transmitted will develop hepatitis. Other patients receiving Australia antigen by transfusion may develop antibodies against it or show no reaction. These findings, in addition to others cited in the referenced publications, provide support for the virus hypothesis, but additional evidence will be needed before it can be concluded that Australia antigen is, in fact, a virus; for example, growth on tissue culture and transmission to experimental animals of purified Au( 1) should be accomplished. These studies are in progress in our laboratory and are very promising. It is necessary to treat blood containing Australia antigen and isolated Au(1) as if the antigen is a virus, since it is possible to contract hepatitis while working with it and administration of serum containing Australia antigen by transfusion or needle injection can cause the disease in patients who receive it. Historically, some of our earliest studies on Australia antigen have been done with Down’s syndrome patients.l4-l6 We first found that Australia antigen was common in leukemia.’ We hypothesized that the presence of the antigen might indicate a susceptibility to leukemia and, if this were so, the antigen would be common in patients who had an increased risk of developing leukemia. It was known that Down’s syndrome patients are at high risk of developing leukemia, and a series of studies was initiated.2JJ7 It was soon found that the