Budding Process and Fine Structure of Lymphadenopathy‐associated Virus (LAV)

Abstract

The budding process and fine structure of lymphadenopathy-associated virus (LAV), were studied by indirect immunofluorescence (IF) and electron microscopy (EM). By IF, LAV antigen was seen to be distributed focally within infected CCRF-CEM cells. Consistent with this finding, electron micrographs showed that LAV particles occurred in a focally aggregated state in a restricted area of the surface of the infected cells. LAV particles possessed bar-shaped, dense and central or eccentric cores. In addition, two or more cores were occasionally observed in one virus particle, or the cores were sometimes absent when thin sections were examined. The envelope of the virus particles had an irregular structure, although LAV particles were approximately spherical.Previous studies have shown that a novel human retrovirus is the causative agent of acquired immunodeficiency syndrome (AIDS) and AIDS-related complex (ARC). Lymphadenopathy-associated-virus (LAV) was isolated initially from cultured T lymphocytes of a homosexual man with lymphadenopathy syndrome (1). Viruses antigenically and morphologically related to LAV were subsequently isolated from individuals with AIDS and ARC, and designated human T-lymphotropic virus type III (HTLV-III) (5) and AIDS-associated retrovirus (ARV) (10). These viruses were later found to be variants of the same virus as shown by comparison of their complete nucleotide sequences (12,15,16,19). The authorized nomenclature of the virus has not yet been decided. LAV has a cytopathic effect on OKT-4 positive lymphocytes (9) and an epitope of the OKT-4 antigen was recently shown to be a component of the receptor for LAV (2,8). Previous studies showed that LAV is released from infected cells by budding from the plasma membrane and that a unique feature of the virus is a cylindrical core observed in many mature virions (5). It is increasingly evident that LAV could be best classified within the lentivirus group of retroviruses (6,(17)(18)(19). However the budding process and fine structure of LAV have not been clearly defined. We report here the data on the budding process and fine structure of LAV obtained by indirect immunofluorescence (IF) and electron microscopy (EM).

Human immunodeficiency virus-like particles produced by a vaccinia virus expression vector.

“…These retrovirus-like particles were detected at 4 hr and increased greatly in amount from 8 hr on. The morphogenesis of the particles, produced by vVK1, was similar to that of HIV-1 and other retroviruses (26)(27)(28)(29). The first indication of particle assembly in infected CV-1 cells was the appearance beneath the plasma membrane of a crescentshaped variably electron-dense nucleoid that became con- centric with an electron-lucent center upon budding.…”

Maturation of Human Immunodeficiency Virus, Strain LAV, in vitro

“…Under the experimental conditions em ployed, 5 days after infection 60% of CCRF-CEM cells were LAV antigen positive by indirect immunofluorescence [2], At this time point viral budding was most abundant. Fig ures la and b are the electron micrographs of the commonest budding profiles.…”

“…This fact may indicate that the incom plete inner dense layer is the result of disper sion of the materials into the central part of the virions to form electron-dense cores, al though morphologically definite cores can not be seen in the electron micrographs. Ma ture virions of HIVshowed marked pleomorphism in their size and large particles con tained more than one core [2], As shown in figure lc, abnormal budding resulted in for mation of virions with an excess amount of envelope material and inner dense layer. The excess amount might lead to the formation of virions with multiple cores.…”

“…Mature virions of human immunodefi ciency virus (HIV) have characteristic elec tron-dense, bar-shaped cores [1][2][3][4][5][6][7]. The size of HIV has been reported to be 85-95 nm [1], 85-220 nm [2], 90-130 nm [3], or 100-120 nm [4].…”

“…The maturation step has been explained in two different ways: (i) maturation free from the cell after budding [3,8,9], or (ii) bridge for mation between immature virions and the cell surface and release from the cell after maturation [10]. Like visna virus, budding HIV particles possess an electron-dense in ner layer between the envelope and electronlucent center [2,3]. The maturation process of HIV has not been well elucidated.…”