Mr. Chairman and Members of the Committee, I am pleased to appear
before you today to discuss the human immunodeficiency virus (HIV) epidemic,
recent developments in HIV research, and the many challenges that remain in
the fight against HIV and the acquired immunodeficiency syndrome (AIDS).
The scope of the epidemic
HIV continues to exact an enormous toll throughout the world, in human
and economic terms. In the United States, the rate of new HIV infections --
approximately 40,000 per year -- continues at an unacceptably high level,
despite an encouraging downturn in new AIDS cases and AIDS-related deaths.
In the developing world, the epidemic is accelerating, notably in sub-Saharan African,
southeast Asia and on the Indian sub-continent. According to adetailed, country-by-country
analysis of HIV prevalence released earlier this year by UNAIDS, approximately 5.8
million people worldwide were newly infected with HIV in 1997 alone. More than
90 percent of these new infections occurred in
developing countries, where antiretroviral therapy is beyond the reach of all but
the privileged few. Alarmingly, in 27 developing countries, HIV prevalence more
than doubled between 1995 and 1997. The prevalence of HIV infection is
highest in the African nations of Botswana and Zimbabwe, where more than 25
percent of adults are now HIV-infected.
Globally, one in every 100 adults 15 to 49 years of age is HIV-infected; at
least 80 percent of these infections are due to heterosexual transmission. By the
end of 1997, an estimated 30.6 million people worldwide were living with
HIV/AIDS, including 1.1 million children younger than 15 years of age. Since the
beginning of the HIV/AIDS epidemic, at least 8.2 million children younger than 15
have been orphaned because of the premature deaths of HIV-infected parents.
Clearly, HIV remains one of the greatest threats to global health, and
requires a sustained commitment by the various partners in AIDS research and
prevention: U.S. and foreign government agencies, UNAIDS, non-governmental
and philanthropic organizations, academia, industry, and the activist community.
Sadly, we recently lost two of the most valiant soldiers in the battle against AIDS:
Dr. Jonathan Mann and his wife, Dr. Mary Lou Clements-Mann. Collectively, we
must strive to accomplish the goals to which these outstanding individuals
dedicated their lives.
As noted above, new AIDS diagnoses and deaths have dropped
significantly in the United States and other developed countries in the past two
years. These trends are probably due to several factors, particularly the
increased use of potent, albeit expensive, combinations of HIV drugs. Eleven
antiretroviral drugs are now licensed in the United States, and several new
agents are in the final stages of clinical testing and should become available
soon. Consensus guidelines have been developed for the use of anti-HIV
medications, and, when appropriately applied, have greatly improved the
prognosis for HIV-infected individuals.
Unfortunately, many HIV-infected individuals have not responded
adequately to the medications, cannot tolerate their toxicities, or have difficulty
complying with complex dosing schedules and substantial pill burdens. In
addition, the ability of HIV to mutate and become resistant to the current drugs is
a persistent threat. Although there is some evidence of immune system
reconstitution in certain patients who receive combination antiretroviral therapy,
the goals of completely "rebuilding" the immune system or eradicating the virus
from the body appear unlikely with current approaches to treatment.
For these reasons, the development of the next generation of therapies
remains a priority. Currently, all licensed antiretroviral medications are directed
at one of two viral enzymes, but many new strategies are being pursued,
including drugs that prevent the virus from entering a cell, and approaches to
boosting an infected person's immune response.
In developing countries where per capita health care spending may be
only a few dollars a year, discussion of antiretroviral drugs is largely academic,
since combination therapy and attendant care may cost upwards of $15,000 per
year. Therefore, a continued emphasis on effective, low-cost tools of HIV
prevention is crucial to slowing the epidemic.
Researchers have shown that several approaches to HIV prevention can
reduce the number of new infections when properly executed, including:
education and behavior modification; the social marketing and provision of
condoms; treatment of other sexually transmitted diseases; drug abuse
treatment (for example, methadone maintenance for injection drug users); and
the use of antiretroviral drugs to interrupt the transmission of virus from mother to
infant. For example, a recent study supported by the Centers for Disease
Control and Prevention (CDC) found that HIV transmission from mother to child
could be reduced by 50 percent by giving the drug AZT to mothers during the
last four weeks of pregnancy and during labor and delivery.
Other methods of preventing HIV transmission also may have an
important impact on slowing the epidemic. For example, researchers are
developing and testing topical microbicides, substances that a woman could use
in her vagina before sex to prevent the transmission of HIV and other sexually
transmitted diseases. UNAIDS and others also have facilitated the widespread
use in Africa of the female condom. These interventions may help empower
women to protect themselves in situations where they are unable to avoid sex
with partners who are HIV-infected or to persuade their partners to use a
HIV vaccine development
The development of a safe and effective vaccine for HIV infection remains
the "holy grail" of AIDS research, and an important step toward bringing the HIV
epidemic under control. To speed the pace of HIV vaccine discovery, many
public and private agencies have dramatically increased the resources devoted
to HIV vaccine research. For example, at the National Institutes of Health (NIH),
HIV vaccine funding increased by nearly 80 percent between FY 1995 and the
estimated NIH budget for FY 1999. As part of this expanded effort, NIH has
awarded numerous grants to foster innovative research on HIV vaccines, and is
invigorating and reorganizing its vaccine clinical trials effort. In addition, NIH has
established a Vaccine Research Center within the NIH intramural research
program to stimulate multidisciplinary vaccine research.
HIV vaccine developers face a number of formidable obstacles, such as
the variability of the virus and an incomplete understanding of the specific
immune responses that may protect individuals from infection. However, there
are many reasons to be optimistic that a safe and effective HIV vaccine can be
developed. Perhaps most compelling is the fact that the human immune system
can control HIV under certain circumstances. Experimental vaccines have
protected animals from an HIV-like virus known as the simian immunodeficiency
virus, and candidate HIV vaccines have elicited immune responses and been
proven to be safe in early stage trials in humans.
As part of a broad portfolio of research, recent studies supported by the
NIH have assessed so-called "vectored vaccines": harmless viruses (e.g.
canarypox) which are genetically altered to make HIV proteins. These vaccines
have been administered to volunteers in combination with a separate vaccine
made of a purified HIV protein. Results have been encouraging: in phase I and
phase II studies, the combination approach has appeared safe and evoked
several types of immune responses that may have a role in protection from HIV.
NIH-funded researchers are now comparing three different vectors, as
well as other HIV proteins to determine which combination produces the most
robust immune response. These studies, as well as additional data that emerge
from basic research, will provide the information to determine which products will
advance into larger-scale testing.
Meanwhile, a large-scale study of a vaccine based on the surface proteins
of two HIV strains was recently undertaken in the United States by a private
company, with an additional phase III study to be conducted in collaboration with
CDC in Thailand. NIH will collaborate with the company in evaluating the
immunological responses to the vaccine.
Last year, President Clinton set a national goal of having a useful HIV
vaccine within 10 years. We are well-positioned in our attempt to meet this goal
with the extraordinary basic and applied research that is now under way. As we
work to contain the global HIV/AIDS epidemic, it is essential that public and
private sector partners redouble their commitment to working together to speed
HIV vaccine development, refine prevention efforts, and develop new treatments
for those infected with the virus.