Fine structure of human immunodeficiency virus (HIV), immunolocalization of structural proteins and virus-cell relation

Abstract

The classification of a new agent, i.e. its grouping to a defined virus family, is facilitated by electron microscopical investigations. Depending on the method used, the different distinct features of a virus can be evaluated. Combining immunological and electron microscopical techniques we received detailed information on the morphogenesis and fine structure of the human immunodeficiency virus (HIV). Two strains of HIV-1 and HIV-2 were studied. Light microscopy and SEM of virus infected cultures allowed a rapid overview on the cell cultures and gave information on cell morphology and virus production. The more laborious surface replica preparation technique permitted, in addition to an overview, the observation of structural details on the surface of the virion. Rotational image analysis of surface knobs revealed a T = 7 laevo symmetry, indicating that icosahedral principles are governing the envelope architecture. Thin section TEM of tannic acid treated HIV- producing H9 cells proved to be the most rewarding technique for the analysis of the labile HIV. No morphological differences between HIV-1 and -2 strains were detectable. The combination of structural and immuno-electron microscopical findings led to the establishment of a structural model of HIV. Whether the submembrane p17 protein serves as a morphopoetic factor and scaffolding matrix for the envelope is discussed. The viral core is built up as a double cone with a long and a short axis. The core shell containing the major viral capsid protein p24 encloses the electron dense ribonucleoprotein complex. Structural features, including the loss of the viral surface protein gp120 and the incorporation of MHC class I and II antigents into the viral envelope are discussed as factors involved in the pathogenesis of AIDS.