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Baculoviruses

dlynn at ASRR.ARSUSDA.GOV dlynn at ASRR.ARSUSDA.GOV
Mon Apr 17 08:38:55 EST 1995


On Sat, 15 Apr 1995 19:00:55 GMT, Steve Grendard wrote:

>There is a discussion/controversy of sorts going on on the biz-biotech
>maillist about baculoviruses. Do these insect viruses (being touted as
>a biologic pesticide) enter into higher animals including  humans? If

... snip, snip, snip ...

I have worked with baculoviruses for over twenty years and there is _no_
reported evidence that they can replicate in non-invertebrate cells or
animals.  The most complete compilation of information on safety of these
pathogens to non target organisms is in A. Groner, Specificity and Safety of
Baculoviruses, In _The Biology of Baculoviruses_ (R. R. Granados and B. A.
Federici, eds.) CRC Press (1986).  In his conclusion, "Extensive safety
studies conducted with baculoviruses from Lepidoptera, Hymenoptera, and
Coleoptera have included human beings; in no case were deleterious effects
found."  He also points out that baculoviruses are common "contaminants" of
food, even when grown with conventional pesticides.  This means that every
person that's eaten a salad has ingested viable forms of these viruses.

More recently, papers by P. C. Hartig et al. (Appl. Environ. Microbiol.,
55:1916-1920 (1989) and J. Virol. Meth. 31:335-344 (1991)) use more elegant
procedures and did reveal some cytotoxicity from the budded form of the
_Autographa californica_ virus (AcMNPV) in one monkey and two human cell
lines.  This toxicity was associated with the virus particles.  In our lab, we
have found some cell lines from the gypsy moth (in the same order but a
different family than _A. california_) which are semipermissive for
replication of AcMNPV (new DNA is synthesized as well as three viral-specific
proteins, but no progeny virus) produce a factor which is toxic to a variety
of insect cells.  This factor is, in fact, derived from the envelope of the
input virus and I suspect may also be responsible for the toxicity to the
primate lines (although this has _not_ been examined).

Now, what does this cytotoxicity mean in the real world?  Very little if you
are discussing the wildtype (i.e. occluded form) of these viruses.  The
occlusion bodies which contain the virions are only dissolved in the presence
of highly alkaline conditions (pH 10+).  This happens to be the pH of the
insect gut contents.  On the other hand, mammals have acidic gastric juices
which would not release the viruses.  I suspect the EPA will want extensive
tests performed on OB- recombinant viruses before they will be registered for
use, but even these are very unlikely to have a negative effect on whole
vertebrates.

I hope this helps answer your question.

Dwight E. Lynn
USDA, Beltsville, MD



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