The Antibody Response in Man Following Infection with Viruses of the Pox Group III. Antibody Response in Smallpox

Abstract

From 117 cases of smallpox 140 sera have been examind for antihaemagglutinin, for complement-fixing and for variola-neutralizng antibody.In smallpox patients who had not been vaccinated prior to infection, variola-neutralizing antibody and vaccinial antihaemagglutinin were present in all sera examined after the sixth day of illness. Complement-fixing antibody was not found until the eighth day of illness but was present in all examined after the ninth day.In previously revaccinated smallpox patients variola-neutralizing antibody was present in all sera examined after the third day of illness and antihaemagglutinins in all after the fourth day. Complement-fixing antibody was present by the seventh day and was found in all sera examined after the ninth day. Not only did antibody in general appear earlier in previously vaccinated smallpox patients but the titres were generally considerably higher. In ten fatal cases antibody titres were low except in two in whom the level of variola-neutralizing antibody was quite high—in one case on the second day and in the other on the fourth day of illness.In six variola contacts, who suffered febrile attacks without rash, antibody studies indicated the variolous nature of their illnesses. In these and other atypical smallpox infections, when laboratory confirmation of clinical diagnosis is only requested at a late stage of the disease, a high titre of antibody, particularly complement-fixing antibody, may enable a firm diagnosis to be made.We wish to acknowledge our indebtedness to Dr W. H. Bradley of the Ministry of Health; Dr E. C. Benn of Seacroft Hospital, Leeds; Dr D. C. Liddle of Monsall Fever Hospital, Manchester; Dr E. R. Peirce of Liverpool and other Medical Officers for information concerning smallpox patients. Our thanks are also due to Dr F. O. MacCallum of the Virus Reference Laboratory, Colindale, who kindly sent us sera from some of the cases in the 1950 smallpox outbreak in Brighton.