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February 14, 2010)
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February 11, 2010
CBC News
Scientists have made a key
discovery in pinpointing how HIV is transmitted in men who have sex with men.
The researchers hope that
by better understanding how HIV spreads during human sex, that they'll be better
able to stop the epidemic.
"By knowing the
origin of the transmitted virus, scientists may be able to develop new vaccines,
vaginal microbicides and drugs to prevent the spread of sexually transmitted
HIV," study author Dr. Davey Smith, an associate professor of medicine at
the
Semen is made up of sperm,
white blood cells and the fluid around these cells, known as seminal plasma.
HIV in semen comes in two
contagious forms — DNA in the white blood cells and free-floating RNA in the
seminal fluid.
Until now, researchers did
not know whether HIV RNA or DNA was transmitted during sex.
Smith and his colleagues
used genetic analysis to trace the ancestral history of the virus in six pairs
of men, the source partners, who sexually transmitted their HIV to other men,
the recipient partners.
To investigate, the
researchers compared the virus found in the recipients to the DNA and RNA
versions in the men who infected them.
RNA was the closest match,
leading the team to conclude HIV originated from RNA in the seminal fluid of the
source partners.
The findings are reported
in this week's issue of Science Translational Medicine.
Davey's team only looked
at males, so the findings may not apply to HIV transmission in women.
The results also need to
be tested in larger samples of pairs to determine which features of viral
genomes are linked with transmission.
The approval is for a new
formulation of the tablet, which allows it to be stored at room temperature
rather than in a refrigerator. The drug is used in combination with other
antiretroviral medications to treat HIV.
2010-02-12
The sale of HIV home
testing kits must be regulated by the government, the SA Medical Association has
said.
Sama chairman Dr Norman Mabaso said in a statement on Friday that this was
necessary to prevent the kits from being sold to private individuals without any
counselling.
Sama's call comes after the launch of the home kit was put on hold following
concerns that there was no legal obstacle to stop the kit from being distributed
to individuals.
"Home testing for HIV has important implications for the individual,
especially in respect of HIV counselling procedures," Mabaso said.
"Although Sama fully supports testing, as it is essential for people to
know their status, we do not support the ad hoc sale of home testing kits.
"We will do everything in our power to make presentations to government to
ensure that devices of this nature are distributed responsibly.
"Sama implores government to regulate the sale of these kits and also make
it compulsory for counselling to be available via the merchant when it is
sold." - Sapa
Rosa Freedman
guardian.co.uk, Monday 8
February 2010 18.00 GMT
We all know the risks of
unprotected sex, thanks to public education campaigns. And there have also been
efforts to encourage people to seek an STD test, notably for chlamydia, which
can cause infertility: another 200,000 people were diagnosed with it in the
Private medical coverage
has become widespread, and companies often encourage members to improve their
health, such as by using a gym regularly, through discounts on their premiums.
Yet those same companies are effectively discouraging STD testing by the way
they treat potential customers who have been infected. Health insurance is
particularly difficult to obtain for those with HIV. Premiums may be greatly
increased for those with other STDs. A person who has engaged in risky behaviour
is incentivised not to discover his or her status for fear of falling foul of
these companies.
Criminal law offers
similar disincentives. A person may be prosecuted if, knowing they have a
disease, they engage in unprotected sexual intercourse and infect his or her
partner. Prosecution will depend on whether the other party was told of the STD
before intercourse took place, giving them the choice to consent to risk of
infection. Failure to disclose may result in a charge under the Offences Against
the Person Act 1861. Spreading diseases requires heavy sentencing, for both
deterrent and punitive reasons. Criminal law becomes asinine where it deals with
diseases spread by a person ignorant of his or her status. Such persons can
defend a charge on the basis that lack of knowledge negates the duty to
disclose.
In the event of an
epidemic, various methods are used to contain the threat and prevent its spread.
Isolation, mandatory treatment and other measures may be introduced. The spread
of sexually transmitted diseases – including HIV, which is again on the rise
in
Mandatory testing would
not necessarily mean that STD carriers cannot engage in unprotected sex. It
would result in carriers knowing their status, and requiring them to tell the
other person of, and obtain their consent to, the risk of infection. Informed
consent may allow unprotected sex depending on the STD's classification under
the different criminal "harms", as serious diseases like HIV cannot be
consented to under current law. Criminal convictions would deter failure to
disclose, and punish those ignoring that duty.
An individual's right to decide whether to find out their status is trumped by other people's rights to know the risk of infection. Would compulsory tests be unpopular? Probably. But while insurers continue to discriminate against people with STDs, and advertising and educational campaigns will only go so far in preventing further infections, mandatory testing would enable people to stop infecting others without realising it.
Assembly of bullet-shaped
VSV virion. (Credit: UCLA)
ScienceDaily (Feb. 11,
2010) — Vesicular stomatitis virus, or VSV, has long been a model system for
studying and understanding the life cycle of negative-strand RNA viruses, which
include viruses that cause influenza, measles and rabies.
More importantly, research
has shown that VSV has the potential to be genetically modified to serve as an
anti-cancer agent, exercising high selectivity in killing cancer cells while
sparing healthy cells, and as a potent vaccine against HIV.
For such modifications to
occur, however, scientists must have an accurate picture of the virus's
structure. While three-dimensional structural information of VSV's
characteristic bullet shape and its assembly process has been sought for
decades, efforts have been hampered by technological and methodological
limitations.
Now, researchers at UCLA's
California NanoSystems Institute and the UCLA Department of Microbiology,
Immunology and Molecular Genetics and colleagues have not only revealed the 3-D
structure of the trunk section of VSV but have further deduced the architectural
organization of the entire bullet-shaped virion through cryo-electron microscopy
and an integrated use of image-processing methods.
Their research findings
appear this month in the journal Science.
"Structures of
individual rhabdovirus proteins have been reported in Science and other
high-profile journals, but until now, how they are organized into a bullet shape
has remained unclear," said study author Z. Hong Zhou, UCLA professor of
microbiology, immunology and molecular genetics and a member of the CNSI.
"The special shape of VSV-- a bullet head with a short, helical trunk-- has
lent to its evasion from three-dimensional structural studies."
Based on their research
into the structure of VSV, the team proposed a model for the assembly of the
virus, with its origin at the bullet tip. Their data suggest that VSV assembles
through the alternating use of several possible interaction interfaces coded in
viral protein sequences to wind its protein and RNA chain into the
characteristic bullet shape.
"Our structure
provides the first direct visualization of the N and M proteins inside the VSV
virion at 10.6-Ĺ resolution. Surprisingly, our data clearly demonstrated that
VSV is a highly ordered particle, with the nucleocapsid surrounded by, instead
of surrounding, a matrix of M proteins," said lead study author Peng Ge, a
visiting graduate student at UCLA from Baylor College of Medicine. "To our
amusement, the sequence in assembling viral protein and RNA molecules into the
virus appears to rhyme with the first several measures of Mozart's piano sonata
in C-Major, K.545." (This musical correlation is illustrated in the paper's
supplementary movie 2.)
The findings could help
lead to advances in the development of VSV-based vaccines for HIV and other
deadly viruses, according to the researchers.
"Our structure
provides some of the first clues for understanding VSV-derived vaccine
pseudotypes and for optimizing therapeutic VSV variants," Zhou said.
"This work moves our understanding of the biology of this large and
medically important class of viruses ahead in a dramatic way. The next stage of
research for our team will be to reveal the details of molecular interactions at
the atomic scale using advanced imaging instruments now available at CNSI."
The
In addition to Z. Hong
Zhou and Peng Ge, the research team included colleagues from the laboratory of
Ming Luo, professor of microbiology at the
The research was supported
by the National Institutes of Health.
|
Keith Alcorn,
Wednesday, February 10, 2010 |
Extensively drug-resistant
tuberculosis is most likely emerging as a result of delays in diagnosis,
sub-optimal treatment and poor infection control, not failures in patient
adherence, a newly published study of XDR TB cases in a South African gold mine
suggests.
Drug-resistant TB is an emerging concern in
However, drug-resistant TB remains a major challenge for South African and other
nations in the region, where high rates of tuberculosis are being exacerbated by
HIV infection, which makes people exposed to TB much more likely to develop
active disease.
The study, published this week in the US Centers for Disease Control online
journal Emerging Infectious Diseases, looked at 128 patients diagnosed with
drug-resistant TB at a single gold mine in the
Although the gold mine had achieved a cure rate above 85% in the treatment of
new smear-positive cases by 2001, following the introduction of directly
observed treatment that ensured optimal adherence, new cases continued to rise
and the incidence of drug-resistant TB was also growing.
Investigators from Stellenbosch University, Harvard University School of Public
Health and West Vaal Hospital identified 128 drug-resistant TB cases among 3003
TB cases notified at the gold mine’s hospital. Eighty-four were HIV-positive,
seven were HIV-negative and the remainder had an unknown HIV status. Sixty-two
per cent of those with MDR TB had a CD4 count below 200, indicating advanced HIV
infection, but only 8% were already receiving antiretroviral therapy at the time
of MDR TB diagnosis.
Only 31% of those who were diagnosed with MDR TB were cured; 35% died, with the
remainder still receiving treatment at the time of the analysis.
The investigators found that 74 mTB isolates showed similarity to at least one
other isolate, indicating transmission, and they were grouped in 11 transmission
clusters, the largest of which involved 42 patients. The investigators
calculated that 71% of patients had acquired drug-resistant TB from another
patient.
Multi-drug resistant isolates were more likely to be found in clusters than
single-drug resistant isolates; strains that were classified as XDR TB or pre-XDR
(MDR with resistance to the second-line agents kanamycin or ofloxacin) were 27
times more likely to be found in a cluster than isolates with less drug
resistance (OR 27.42, p<0.001), and no additional risk factors for clustering
were identified in the multivariate analysis.
In the largest cluster, of 42 patients, three-quarters of patients had been
hospitalised for non-MDR TB (in a general TB ward) at the same time as another
patient in the cluster was admitted to the hospital with MDR TB care. Since all
patients with TB received care on the same ward until diagnosed with MDR TB, it
is not hard to see how such a large cluster could have emerged within a single
facility.
In addition 92% of MDR TB patients in the cluster had worked in the same mine
shaft as another person in the same MDR TB cluster, and 85% lived in the same
dormitory as another MDR TB case prior to diagnosis.
Fifty-nine per cent of MDR TB patients in any cluster had a previous history of
TB treatment.
The authors make a number of recommendations for curtailing the spread of MDR TB
within hospitals and workplaces:
Ensure that everyone who
is eligible for antiretroviral therapy is getting it, in order to reduce the
number of individuals susceptible to developing active TB.
Greater efforts to
identify infectious cases through intensified case finding, active screening and
improved education about TB symptoms.
More frequent sputum smear
examinations to identify infectious cases, and more frequent culture-based
diagnosis to identify cases before they become infectious.
Development and
implementation of rapid drug susceptibility testing in order to identify MDR
cases, plan appropriate treatment and separate from susceptible patients.
Better infection control
measures on general wards, outpatient waiting areas and TB wards.
Reference
Calver AD et al. Emergence of increased resistance and extensively
drug-resistant tuberculosis despite treatment adherence,