ABSTRACT
Looking at the literature, pseudotyped viruses can be found as
early as in the seventies. In 1978, Zavada et al.1 described the
use of pseudotype particles as a sensitive assay for the detection
of neutralizing antibodies (N-Abs), in particular for antigens from
noncytopathogenic or slow-growing viruses.2 At that time, the so-
called pseudoparticles, or phenotypically mixed particles, referred
to replicative virions from doubly infected cells that incorporated
an envelope of one virus on the surface of the second one.
According to these authors, it was possible the rhabdovirus vesicular
stomatitis virus (VSV) could acquire surface glycoproteins (GPs) of
all retroviruses. This approach successfully produced pseudotype
particles from a wild range of viruses extensively used for the
detection of N-Abs. Nevertheless, there were some disadvantages,
in particular the tedious purification and characterization process,
the absence of a reporter signal for the direct observation of the
infection, and the biosafety concern related to the use of live viruses.
Research pioneered by Zavada demonstrated that retroviruses, like
human immunodeficiency virus (HIV), can rather easily incorporate
heterologous GPs from other viruses, including other viral families,
through phenotype mixing. These early observations were the
cornerstone to the subsequent design of HIV-1-based lentiviral
vector strategies.
