HICNet Medical News Digest      Wed, 01 Jun 1994        Volume 07 : Issue 24

Today's Topics:

  Scientists Use "Fingerprints" to Track Periodontal Bacteria
  AIDS Daily News Summary

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        Douglas B. Hanson, Ph.D., Forsyth Dental Center, Boston, MA

             Lawrence Lee Miller, B.S. Biological Sciences, UCI

            Dr K C Lun, National University Hospital, Singapore

             W. Scott Erdley, MS, RN, SUNY@UB School of Nursing

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Date: Wed, 01 Jun 94 22:09:25 MST
From: mednews (HICNet Medical News)
To: hicnews
Subject: Scientists Use "Fingerprints" to Track Periodontal Bacteria
Message-ID: <ei20mc9w165w@stat.com>

       Scientists Use "Fingerprints" to Track Periodontal Bacteria
                      NIDR Research Digest, April 1994

     Dental researchers can now identify the bacteria that cause periodontal
diseases as precisely as fingerprint experts can identify people.  NIDR
grantee Dr. Joseph Zambon, at the State University of New York at Buffalo,
recently reported on a technique that produces a "DNA fingerprint" so unique
it can be used to track these disease-causing bacteria from one individual
to another. "Identifying bacteria with this degree of precision is a
technological advance that can provide important clues for preventing and
treating gum disease," said Dr. Zambon.    In addition to examining person-to-
person transmission, the new fingerprinting technique can detect subtle
differences in the bacterial distribution within an individual's mouth or
among human populations scattered throughout the world. The technique can be
also used  to follow changes in bacterial populations during disease
progression or in response to different types of treatment. "The applications
are far-reaching," says Dr. Zambon. "We've just begun to apply this
technique to study how to stop the infection by periodontal bacteria and how
to eliminate existing infections."

Identification of Source

The procedure, developed independently  at the California Institute of
Biological  Research and the E.M. duPont  Company, was adapted by Dr. Zambon
to track periodontal bacteria.  The new  technique holds great promise for
unraveling the mystery of how these fragile bacteria, which are readily
killed by oxygen in the air, initially gain access to the human mouth. In
the past, studies attempting to answer questions about the source of an
infection or person-to-person transmission of periodontal bacteria were
hampered by the inability to distinguish between bacteria within the same
species.  These so-called 'strains' can look essentially the same, even when
analyzed in great detail.  In recent years, DNA fingerprinting technology
has made it easier to discriminate between strains. The classic approach to
DNA fingerprinting relies on   enzymes that digest or break apart DNA. In
this way the single bacterial chromosome, which is made up of two
complimentary strands of DNA containing millions of nucleotide bases, is
broken into many smaller fragments. The actual number and size of the DNA
fragments depends on the structure of the bacterial chromosome.  The DNA
fragments can be separated on electrophoresis gels according to the molecular
size of the DNA pieces. The fragments appear in the gel as a pattern of
bands, referred to as the DNA fingerprint, which visually resembles the "bar
codes" used by stores to identify merchandise.  It is now known that each
bacterial species can be separated into a finite number of strains based on
differences in fingerprint patterns. However, the number of strains is highly
variable among the different species of periodontal bacteria. For example,
29 different fingerprints have been reported for one species, Porphyromonas
gingivalis.  Only 3 fingerprints have been identified for another species,
Actinobacillus actinomycetemcomitans (A.a.). Yet even with this  kind of DNA
fingerprinting it is difficult  to do transmission studies on species like
A.a., in which there are a number of patterns.  Moreover, fingerprint
patterns produced by DNA digestion can consist of several hundred bands,
making it difficult to discriminate subtle  existing differences.  To get
around these shortcomings, Dr. Zambon and his colleagues used a modified
version called the arbitrarily  primed polymerase chain reaction, or APPCR.
This technique is based on the polymerase chain reaction (PCR), a method that
is widely used to copy sections of DNA for identifying gene structure or
matching tissue specimens.  PCR uses two small, synthetic strips of DNA
called primers to amplify a larger region of DNA. The primers bind to
specific sites on opposing strands of the double-stranded DNA, and make
millions of copies of the intervening stretch of DNA. The primers usually
have specific nucleotide sequences that bind to previously identified
segments of DNA. However, in the case of AP-PCR, no knowledge of the DNA
sequence is required. A single primer, consisting of an arbitrary sequence
of 10 or 12 bases, binds at random sites along the bacterial chromosome. The
amplified segments vary in number and size depending on the  unique structure
of each bacterial  chromosome.  AP-PCR generates fewer bands and more unique
patterns than  does conventional fingerprinting, thereby  increasing the
ability to discriminate between similar strains.  Although the work is still
in the early stages, Dr. Zambon's group has successfully used AP-PCR to
fingerprint several species of periodontal bacteria.  In the case of A.a.,
14 different fingerprints were produced from 20 isolates examined, compared
to only three distinct genetic patterns from a large number of strains
evaluated in studies using conventional fingerprinting.  When AP-PCR was used
to study A.a. from different families, it was observed that in 6 of 7 cases
husband and wife harbored different strains.  The children, however, carried
strains identical to those found in one of the parents.  These findings
support the hypothesis that periodontal bacteria are transmitted from parent
to child. Such information could eventually be useful in determining how and
when a child is infected with A.a. or other periodontal bacteria, and what
preventive measures may be effective.  The study, funded by the NIDR and the
Norwegian Research Council appeared in the October 1993 issue of the Journal
of Clinical Microbiology and the January 1994 issue of the Journal of
Periodontology.  The investigators were Dr. Hans Preus of the Department of
Periodontology, Dental Faculty, University of Oslo, Norway; and Drs. Violet
Haraszthy, Joseph Roben Dunford and Robert Genco, representing the
Departments of Oral Biology and Periodontology, School of Dental Medicine,
State University of New York at Buffalo.



------------------------------

Date: Wed, 01 Jun 94 22:10:35 MST
From: mednews (HICNet Medical News)
To: hicnews
Subject: AIDS Daily News Summary
Message-ID: <ck20mc10w165w@stat.com>

                     AIDS Daily Summary

The Centers for Disease Control and Prevention (CDC) National AIDS
Clearinghouse makes available the following information as a public
service only. Providing this information does not constitute endorsement
by the CDC, the CDC Clearinghouse, or any other organization. Reproduction
of this text is encouraged; however, copies may not be sold, and the CDC
Clearinghouse should be cited as the source of this information.
Copyright 1994, Information, Inc., Bethesda, MD

           Topic in this issue
           - CDC Warns About Danger of AIDS in Home Care
           - New Test May Check for HIV in Newborn Babies
           - A Cytotoxic Response Against AIDS
           - AIDSLine: Is Some of My Pain Only in My Head?
           - A Novel Technique Fights AIDS Virus From Inside Cells
           - Scientists Recommend New AIDS Drug
           - New AIDS Treatment Acts on 'Resting' Cells--Researcher
           - Persistent Colonisation of Potable Water as a
             Source of Mycobacterium Avium Infection in AIDS


             "CDC Warns About Danger of AIDS in Home Care"
                         Reuters (05/19/94)
                           (Morgan, David)

     The Centers for Disease Control and Prevention yesterday reported two
new cases of household HIV transmission, and issued a warning about the
increasing potential for the spread of the virus in the home.  The two
household transmission cases, among eight that have occurred since 1986,
may be the first in the country in which HIV infection clearly occurred
through care-giving.  In both cases, the virus was transmitted because
standard precautions were not followed.  One case involves the 5-year-old
child of HIV-positive parents who researchers believe may have contracted
the virus either through open sores on her mother's body, or by sharing a
toothbrush at a time when the woman suffered from bleeding gums.  Although
the child initially tested negative for AIDS in 1990 and July 1993, HIV
antibodies were present last December.  More relevant to researchers is the
other case--that of a 75-year-old woman caring for her HIV-infected adult
son.  The elderly woman, who had no other risk factors, tested positive for
HIV in August 1991, a year after her son died.  "She did provide nursing
care to her son," said Dr. Harold Jaffe, director of the CDC's HIV/AIDS
division, explaining that the woman was exposed to her son's urine, feces,
and blood.  "She wore gloves part of the time but not all the time."  The
CDC has issued a set of precautionary guidelines for people caring for
HIV-infected loved ones at home.  The recommendations include wearing
protective gloves, careful handling and disposal of needles, and bandaging
all open sores.  Jaffe says the cases illustrate a problem posed by a lack
of adequate instructions from medical professionals.


              "New Test May Check for HIV in Newborn Babies"
                            Reuters (05/19/94)

     A new test that examines umbilical cord blood samples to detect
cogenital infections in newborns may also effectively track whether HIV is
transmitted from mother to baby, according to researchers.  By testing for
a protein called CD45, found in two forms in white "T" blood cells, in
newborns and measuring the relative proportions of these two proteins,
Drs. Colin Michie and David Harvey of the Royal Postgraduate Medical School
were able to diagnose perinatally acquired infections such as chicken pox,
cytomegalovirus, and toxoplasmosis in the infants.  Michie and Harvey warn
that these were the results of a preliminary study, and that a larger trial
is needed to assess the suitability of the technique for determining whether
HIV has been transmitted from a chronically infected mother to her baby.


                  "A Cytotoxic Response Against AIDS"
            Lancet (04/30/94) Vol. 343, No. 8905, P. 1093
                          (Thompson, Clare)

     In examination of HIV pathology, one area of interest is the difference
between short-term HIV survivors, who progress rapidly to full-blown AIDS,
and long-term survivors, who remain healthy after a decade or more.  There
is also a subset of patients known as long-term non-progressors, who manage
to stay healthy and maintain CD4 T-cell counts above 500.  At the April
meeting on Biotechnology against AIDS in Florence, several AIDS researchers
discussed the possible role of CD8 lymphocytes in long-term survival.  Dr.
Anthony Fauci of the National Institute of Allergy and Infectious Diseases
described how the lymph-nodes of short-term survivors show a high level of
viral burden and virus replication, and ultimately destruction of the
lymph-node architecture, while the lymph-nodes of long-term non-progressors
remain intact even after 10 years of infection.  The differences suggest
either that AIDS progression depends upon viral load, or that long-term
non-progressors have some immune response that can clear the virus.


               "AIDSLine: Is Some of My Pain Only in My Head?"
                     Advocate (05/03/94) No. 654, P. 34
                             (Cohan, Gary R.)

     HIV patients that experience aching, burning, numb, tingling,
hypersensitive, or outright painful feelings in their hands and feet might
think the pain is all in their head.  Predominantly sensory neuropathy (PSN),
however, is a nerve disorder that is actually rather common among people in
the symptomatic, later stages of HIV infection.  The condition, which
develops in more than 30 percent of AIDS patients, often starts in the toes
or fingertips and spreads proximally.  Because PSN can make it painful to
walk or use one's hands, early intervention is crucial.  The patient's
medication list should be reviewed to identify possible contributors to
PSN, such as ddI, ddC, d4T, Dapsone, and isoniazid.  Excess vitamin B6 or
too much alcohol can also contribute to the problem.  Mild neuropathy can
be treated by simply taking ibuprofen (Advil or Motrin), while tricyclic
antidepressants are more effective for more severe symptoms.  Alternatives
include topical capsaicin cream, certain antiseizure medicines, or a hear-
rhythm drug called mexiletine hydrochloride.  Because many of these drugs
have adverse side effects, physicians should consider prescribing drugs to
relieve severe discomfort.


          "A Novel Technique Fights AIDS Virus From Inside Cells"
                  Philadelphia Inquirer (05/24/94) P. A2
                            (Collins, Huntly)

     Using a novel technique of gene therapy, researchers at Thomas
Jefferson University have discovered how to virtually halt HIV's
multiplication inside human cells.  While antibodies usually prevent
infection by binding to viruses outside of cells, this new method involves
creating genetically-engineered antibodies that fight the disease inside
infected cells.  The Jefferson scientists targeted one of 10 known HIV
genes called the Rev, which directs production of a protein that is
essential for the virus to multiply in human cells.  The researchers
induced mice to produce the antibody to the Rev protein, then cloned the
gene responsible for producing that antibody.  They created a fragment
of the gene by clipping out the two tips of the Y-shaped antibody and
linking them together with another molecule.  The synthetic gene fragment
was then inserted into human cells, which were exposed to massive amounts
of HIV.  Although the cells became infected, viral reproduction was
maintained at dramatically low levels, according to the researchers.
Dr. Roger J. Pomerantz, head of the study, said he expects to seek federal
approval this summer to test this novel approach in human subjects.  If
approved, a small safety trial could begin later this year.


                 "Scientists Recommend New AIDS Drug"
                   Baltimore Sun (05/21/94) P. 11A

     An advisory committee to the Food and Drug Administration last week
recommended that the government approve a new drug to treat HIV, but with
strong warnings that doctors still do not know enough about the medicine
to say who should take it.  The panel of scientists said that Stavudine,
or d4T, probably has some benefit over the three existing AIDS drugs, but
could not say precisely who would benefit, how safe the drug is, or whether
the manufacturer is on the right track to answer these and other questions.
The drug seems to help boost the immunity of HIV patients while creating
fewer side effects than other drugs, according to Bristol-Myers Squibb.
The company requested FDA approval of d4T for AIDS patients who cannot
tolerate AZT, ddI, or ddC because of their serious side effects.  The FDA
has not said when it will make a decision regarding d4T.  Related Story:
Boston Globe (05/21) P. 10


         "New AIDS Treatment Acts on 'Resting' Cells--Researcher"
                           Reuters (05/21/94)

     A new HIV treatment unveiled this week is more promising than previous
ones because it acts on inactive or "resting" cells, according to Dr. Jorge
Vila, the doctor leading the researcher.  "Antiviral drugs like AZT ... are
not as efficient in humans as they are 'in vitro,'" Vila told local Argentine
newspaper Pagina 12.  "We believe that this is because the cells on which
they are tested are active."  In humans, 95 percent of the cells affected
by HIV are "resting" ones, he said.  A team of researchers headed by Vila
reported last week that test-tube experiments with a combination of a new
drug, DAH, and ddI, eliminated HIV from "resting" lymphocyte blood cells.
The research may point toward an effective new treatment for the 14 million
HIV-infected people around the globe.


            "Persistent Colonisation of Potable Water as a
            Source of Mycobacterium Avium Infection in AIDS"
             Lancet (05/07/94) Vol. 343, No. 8906, P. 1137
          (Von Reyn, C.F.; Maslow, J.N.;  Barber, T.W. et al.)

     The source of myobacterium avium infection in AIDS has not been
identified; nor is it known whether most AIDS patients acquire the organism
from recent infection or through reactivation of previous infection.  As
part of an epidemiological study, von Reyn et al. isolated colonies of M.
avium from AIDS patients and from potable water to which they had been
exposed.  Of the isolates, which were analyzed with pulsed field gel
electrophoresis, 29 of 39 patients were infected with one or more unique
clinical strains of M. avium and seven patients were infected with three
groups of common strains.  Group 1 included three patients living in
separate rural areas with no common exposures except for treatment at
hospital A.  The same strain was isolated repeatedly over a 41-month
period from a recirculating hot water system at hospital A.  Group 2
included two patients with no common exposure except for treatment at
hospital B.  The same strain was repeatedly isolated over two years from
a recirculating hot water system at hospital B.  Patients in both groups
had numerous possible exposures to hospital hot water.  Von Reyn et al.
conclude that institutions may have hot water systems that are persistently
colonized with a particular strain of M. avium.  HIV patients who are
exposed to such water sources can develop disseminated M. avium infection,
they say.



------------------------------

End of HICNet Medical News Digest V07 Issue #24
***********************************************


---
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