Polymorphonuclear leukocyte-associated antigenemia in measles: demonstration and significance.

An indirect immunoperoxidase technique was used for the identification of measles virus (MeV) antigen in routinely prepared peripheral blood smears. Characteristic brown immunoperoxidase staining was present in the polymorphonuclear (PMN) leukocytes in 25 of 31 children during the exanthematous stage of measles. No peroxidase staining was seen on peripheral blood smears in any of 9 children convalescing from measles or in 9 children with upper respiratory tract infections ( URTI ) without exanthema. These findings were confirmed by control studies and were reproduced by immunofluorescent staining. The data suggest that MeV antigen is localized in the PMN leukocytes during the acute stage of measles infection, and may be connected to phagocytosis of viral antigenic material by PMN leukocytes. The technique described has potential for rapid laboratory diagnosis of measles and, possibly, of other viral infections during the acute stage and before measurable amounts of antibodies are produced.