HIV stands for Human Immunodeficiency Virus. This is the virus that causes AIDS. HIV is a retrovirus. Retrovirus' infect human cells and use them to reproduce.
The U.S. Centers for Disease Control and Prevention (CDC) defines someone as having a clinical diagnosis of AIDS if they have tested positive for HIV and meet one or both of these conditions:
In healthy individuals, the CD4 count normally ranges from 450 to 1200. A person who is infected with HIV carries the virus in certain body fluids, including blood, vaginal secretions, semen, and breast milk. Sometimes this person may be referred to as HIV+, meaning that they received a "positive" result of his/her HIV test. Conversely, a person who tests negative may be referred to as HIV-. In order for HIV to be transmitted, infected fluids must somehow enter the bloodstream of another person. Some of the most common ways that HIV is transmitted are:
HIV is not easily transmitted. For example, HIV is a relatively weak virus outside the body and usually dies soon after exposure to the air. Moreover, because it is not transmitted through food or air, it requires exposure to specific types of infected body fluids and a mode of entry into the body. There is no evidence of infection by a family of household member, co-worker, or friend through casual contact such as hugging or light kissing (such as a peck on the cheek or mouth), shaking hands, sharing eating utensils and bathroom facilities. While there has been evidence of HIV transmission through deep, prolonged kissing on the mouth, the risk is considered relatively low especially if both parties have healthy mouths and gums (i.e....healthy gums and an absence of sores and cuts). The United
States has been screening the blood supply for HIV for over a decade
so that infection through blood products provided by legitimate
sources, such as hospitals, blood banks, or other established blood
collection centers is virtually non-existent. Other unlikely sources
for HIV infection are sweat, tears, vomit, feces, and urine, and
insects such as mosquitoes and fleas. There are many types of medications available in the United States and several other countries to treat HIV infection and AIDS. Some of these are designed to treat the opportunistic infections and illnesses that affect people with HIV/AIDS. In addition, several types of drugs seek to prevent HIV from reproducing and destroying the body's immune system. With the advent of Highly Active Antiretroviral Therapy (HAART), many people living with HIV/AIDS are living productive and relatively healthy lives. Although treatment options continue to expand, as more medications become available, the management of HIV-infected patients has become increasingly complex. This is a result of more choices for therapy, the emergence of and need for resistence testing (or testing to find out if a person has developed a resistance to any of the available antiviral medications) and the growing understanding that many of the medications can be toxic and cause a variety of different side affects when taken over the long-term. While there is agreement that HIV+ people who have symptoms should be treated, it is not clear how soon therapy should begin with those who are newly diagnosed and not yet sick. Therefore, the approach has often been limit the use of antiretrovitral treatment for those recently infected unless there is assurance that s/he will adhere to the medication schedule and/or to refer him/her to clinical trials whenever possible. The goal of initial antiretroviral therapy is to reduce the viral load (or the amount of HIV viral particles in the blood) to below the ability of the testing methods to detect. The decision
to initiate antiretroviral therapy should be based on the degree
of immunosuppression and the risk of progression, as indicated by
the CD4+ cell count and the plasma viral load. However, patients
should not begin therapy until they understand the reason for treatment,
appreciate the importance of adherence, and are motivated to begin. Because treatment regimens are unpleasant and complex, many patients occasionally miss doses of their medication. Failure to take anti-HIV drugs on schedule and in the prescribed dosage can encourage the development of new viral strains that are resistant to current HIV drugs. Even among those who do respond well to treatment, HAART does not eradicate HIV. The virus continues to replicate at low levels and often remains hidden in "reservoirs" in the body, such as the lymph nodes and brain. Patients who experience failure in their treatment on an initial regimen should not be allowed to continue taking a failing regimen without some intervention, since continued therapy may increase resistance and cross-resistance. Patients who experience extensive drug resistance (or who find that their medications fail because their strain of the virus is resistant to them) may benefit from continued therapy despite lack of complete virologic suppression. However, the benefit of continued therapy in preventing immunologic or clinical progression must be weighed against the accumulation of additional resistance mutations that may decrease activity of drugs not yet available. Because treatment
of HIV is so complex, it is imperative that an experienced HIV physician
guides treatment. There are now many options for effective antiretroviral
therapy. It is no longer necessary to prescribe complex regimens
with dozens of pills taken at different times of the day. The choice
of treatment should be based on such issues as potency, tolerability,
convenience, long-term toxicity, and drug resistance. There are
two primary categories of HIV drugs anti-retroviral medication and
drugs that prevent or treat opportunistic infections. There are
three categories of anti-retroviral medication: Nucleoside (NRTI's),
Non Nucleoside Reverse Transcriptase (NNRTI's) inhibitors, and Protease
inhibitors (PI's). These drugs differ because they attack HIV at
different points in its life cycles. Following is a partial list
of approved HIV medication:
There are also several new types of antiretrovirals currently being tested. New categories of drugs include Nucleotide Reverse Transcriptase, Cellular and Entry inhibitors. Reseachers are also trying to identify new targets for anti-HIV medications and to discover ways of restoring the ability of damaged immune systems to defend against HIV and the many illnesses that affect HIV-infected individuals. In addition to antiretroviral therapy, it is also important to receive medical care to prevent or treat the opportunistic diseases that affect people living with HIV/AIDS. Some of the opportunistic diseases associated with HIV/AIDS are Pneumocystis carinii pneumonia (PCP), cytomegalovirus (CMV) disease, Mycobacterium avium complex (MAC) disease, Candida esophagitis, Kaposi's sarcoma, lymphoma, progressive multifocal leukoencephalopathy (PML), dementia, wasting, toxoplasmosis, cryptococcosis, herpes zoster and cryptosporidiosis. Despite recent progress in treatment and prevention, HIV disease and AIDS continue to exact an enormous toll throughout the world. According to the Joint United Nations Programme on HIV/AIDS (UNAIDS), more than 58 million people worldwide have been infected with HIV since the beginning of the pandemic; 22 million of these individuals have died. An estimated 5.3 million people, most of whom live in developing countries, were infected with HIV in the year 2000 alone. "Historically,
vaccines have provided safe, cost-effective and efficient means
of preventing illness, disability and death from infectious diseases",
says Dr. Fauci. "The development of a safe and effective vaccine
for HIV infection is a central goal of AIDS research and a necessary
tool to bring the HIV epidemic under control." Dr. Fauci adds: "NIAID has played a major role in the development of vaccines for many other important diseases, such as hepatitis B, Haemophilus influenzae type B, pertussis and pneumococcal infections. We fully expect that the experience, expertise and commitment of NIAID-funded investigators and our partners in the United States and abroad will lead to the development of a useful HIV vaccine as well." Ramping Up Research Resources To
speed the pace of HIV vaccine discovery, NIH has increased HIV vaccine
research funding more than six-fold since 1990, to an estimated
$356.6 million for fiscal year (FY) 2002. NIAID is the lead NIH
institute for HIV vaccine research, and accounts for more than 75
percent of NIH vaccine spending. At NIAID, an estimated $450.7 million
will be devoted to all vaccine research in FY 2002, with 61 percent
of that total ($276.5 million) dedicated to HIV vaccine development. In addition to an extensive portfolio of basic research, NIAID-supported investigators are testing diverse HIV vaccine strategies in animal models and human volunteers. NIAID recently launched the HIV Vaccine Trials Network (HVTN, www.hvtn.org), a global research network that will conduct all phases of the clinical HIV vaccine research. FY 2002 funding for the HVTN is an estimated $35.6 million. The HVTN, formerly known as the AIDS Vaccine Evaluation Group, has already provided a wealth of data that contribute to many researchers' optimism that a safe and effective HIV vaccine can be developed. This network will be central to the NIAID's capabilties to perform clinical testing on a variety of candidates in the HIV vaccine "pipeline". Another important NIAID initiative is the Comprehensive International Program of Clinical Research on AIDS (CIPRA, www.niaid.nih.gov/daids/cipra/). CIPRA, with estimated FY 2002 funding of $15.0 million, will provide long-term support for development of research infrastructure and fundamental laboratory and clinical studiesof practical and affordable methods for prevention and treatment of HIV/AIDS in international settings, especially in developing regions. These efforts will enhance the ability of host countries to conduct relevant research, to prepare for and participate in large-scale HIV therapeutic, vaccine and prevention clinical trials, and to study diagnostic and treatment interventions in local populations. On the NIH campus, NIAID's Dale and Betty Bumpers Vaccine Research Center (VRC, www.niaid.nih.gov/vrc) conducts all stages of HIV vaccine research, from basic investigations to clinical trials. FY 2002 funding for VRC is an extimated $40.0 million. The VRC recently began its first clinical trial of a candidate HIV vaccine: a Phase I study of a product made from the DNA of two HIV proteins called "gag" and "pol". When injected into a person, the viral DNA induces the production of small amounts of the HIV proteins but not the intact virus. This study will see if the body mounts an immune response to these proteins. This candidate HIV vaccine, like all other NIAID-sponsored candidates, cannot lead to HIV infection in people. NIAID also supports numerous other programs in HIV vaccine development, such as a network of Simian Vaccine Evaluation Units; and HIV Vaccine and Design Development Teams, public-private partnerships of scientists from industry and/or academia, which have identified specific vaccine concepts amenable to accelarated development. In preclinical and clinical studies, NIAID-supported investigators are testing a wide range of vaccine strategies such as recombinant HIV proteins, synthetic peptides, recombinant viral vectors, recombinant bacterial vectors, DNA vaccines and synthetic HIV-like particles. Currently, NIAID has a diverse research "pipeline" of approximately two dozen vaccine candidates. Approximately 16 of these candidates are directed against the subtypes (clades) of HIV found in the developing world, such as clade A (common in Africa) and clade C (common in Africa and Asia). Among many promising studies, several groups working with vaccines against an HIV-like virus known as simian immunodeficiency virus (SIV) or a combination virus called SHIV (made of components of both HIV and SIV) have shown that vaccinated monkeys challenged with lethal doses of virus do not become sick, and maintain very low levels of virus in their bloodstream. "A number of studies suggest that a vaccine that does not prevent HIV infection, but slows the course of disease, may not only benefit vaccinated individuals, but could slow the dynamics of the HIV epidemic by lowering viral load in infected individuals and thereby reduce transmissibility of the virus", says Dr. Fauci. Despite
many exciting advances, a number of obstacles remain in the search
for a safe and effective HIV vaccine. AIDS Vaccine 2001 is sponsored by the Foundation for AIDS Vaccine Research and Development in Alexandria, Virginia. Co-sponsors include agencies of the NIH (NIAID, Office of AIDS Research, and the National Cancer Institute), the Centers for Disease Control and Prevention, UNAIDS, the World Health Organizations, and the Agence Nationale Recherches sur le SIDA (France). NIAID is a component of the National Institutes of Health (NIH). NIAID conducts and supports research to prevent, diagnose, and treat illnesses such as HIV disease and other sexually transmitted diseases, tuberculosis, malaria, asthma, and allergies. NIH is an agency of the U.S. Department of Health and Human Services. Press
releases, fact sheets, and other NIAID-related materials are available
on the NIAID Web site at www.niaid.nih.gov. Despite continued intensive research, experts believe it will be at least a decade before we have a safe, effective, affordable AIDS vaccine. And even after a vaccine is developed, it will take many years before the millions of people at risk of HIV infection worldwide can be immunized. Until then, other HIV prevention methods, such as using condoms and avoiding needle sharing, will remain essential. |
