Biology Reference
In-Depth Information
cross-strain manner raised considerable interest because it offered a
potential means to design vaccines for diseases such as HIV, influenza,
and hepatitis C, whose multiple and/or evolving strains pose such a
challenge for vaccinologists. While the current influenza vaccine can-
not protect against a virus of the same subtype that has drifted even a
minor amount, the DNA vaccine protected against a challenge from
a completely different subtype. This raised hopes that DNA vaccines
would provide a new means for making vaccines that would be
broadly effective against a variety of strains, thereby helping to pre-
vent the types of global epidemics such as the 1919 influenza pan-
demic that killed about 20 million people, or be a foundation for a
rapidly produced component against bird influenza, H5N1. The hope
was also that the DNA vaccines would be a means to make vaccines
not only against other viral diseases such as HIV, but also against
other viruses whose sequellae included cancer (such as papilloma
virus
5
and hepatitis C) and infectious diseases such as malaria that
would benefit from the cytotoxic T cell response.
During the last few years, progress has been made in the area
of protection against both viral and bacterial diseases. Recent
expression analysis has shown that DNA antigens may act as
endogenous immune activators in specific species.
6,7
Also, the enve-
lope antigens of two acute RNA viruses (rhabdo and filo) have
been shown to confer protective capacity after vaccination with
their DNA homologs. The single DNA representing the G protein
of rhabdovirus was shown early to protect mice. Envelope genes
representing glycoproteins of the Ebola virus strains from central
Africa (Zaire and Sudan), together with the conserved nucle-
oprotein gene induced antibody in all the healthy subjects, while
one third of the immunized persons obtained cytolytic T-cell reac-
tivity.
8
Antibody is assumed to be the most important protective
entity for acute RNA viruses, while cell-mediated immunity is nec-
essary for infections establishing persistent infections. Plasmid DNA
encoding HIV proteins incorporated in a prime-boost schedule
predicted the potent and broad immunogenicity subsequently
found in humans.
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