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HIV Life Cycle - Evidence That HIV Causes AIDS
The acquired immunodeficiency syndrome (AIDS) which
is caused by the human immunodeficiency virus (HIV), was detected &
recognized in 1981 for the very first time has spread since then and
become a major worldwide epidemic. By leading to the destruction
and/or functional impairment of cells of the immune system, notably
CD4+ T cells, HIV continuously and progressively destroys the body's
ability to fight infections and certain types of cancers.
This document summarizes the abundant evidence that
HIV causes AIDS. Questions and answers further on in this document
address the specific claims of those who assert that HIV is not the
cause of AIDS.
Before the advent of HIV, AIDS-related diseases such
as PCP, KS and MAC were rarely found in developed countries; today,
they are very common in HIV-infected individuals. Prior to the
appearance of HIV, AIDS-related conditions such as Pneumocystis
carinii pneumonia (PCP), Kaposi's sarcoma (KS) and disseminated
infection with the Mycobacterium avium complex (MAC) were
extraordinarily rare in the United States. In a 1967 survey, only
107 cases of PCP in this country had been cited in the medical
literature, virtually all among individuals with underlying
immunosuppressive conditions. Before the AIDS epidemic, the annual
incidence of Kaposi's sarcoma in the United States was 0.2 to 0.6
per million population, and only 32 individuals with disseminated
MAC disease had been described in the medical literature. By the end
of 1999, CDC had received reports of 166, 368 HIV-infected patients
in the United States with definitive diagnoses of PCP, 46, 684 with
definite diagnoses of KS, and 41,873 with definitive diagnoses of
disseminated MAC.
AIDS and HIV infection are invariably linked in
time, place and population group. It is historically evident, that,
the occurrence of AIDS in human populations has closely followed the
appearance of HIV. In the United States of America, the first cases
of AIDS were reported in 1981 among homosexual men in New York and
California and retrospective examination of frozen blood samples
from a cohort of gay men showed the presence of HIV antibodies as
early as 1978 but not before then. Subsequently, in every country
and city where AIDS has appeared, evidence of HIV infection has
preceded AIDS by just a few years.
Many studies reveal and agree upon, that, only a single factor, HIV,
predicts whether a person will develop AIDS or not. Other viral
infections, bacterial infections, sexual behavior patterns and drug
abuse patterns do not predict in any way who develops AIDS.
Individuals from their respective diverse native geographical
backgrounds, including heterosexual men & women, homosexual men &
women, hemophiliacs, sexual partners of hemophiliacs & transfusion
recipients, injection-drug users & infants have all developed AIDS,
with the only common factor being their prior infection with HIV.
Numerous serosurveys show that AIDS is found to be very common in
those populations where many individuals have HIV antibodies. Vice
versa, in that population of people with low seroprevalence of HIV
antibodies, AIDS is is found to be extremely rare. For example, in
the southern African country of Zimbabwe (population 11.4 million),
more than 25 percent of adults ages 15 to 49 are estimated to be
HIV-positive, based on numerous studies. As of November 1999, 74,000
cases of AIDS were reported to the WHO. In contrast, Madagascar, an
island country off the southeast coast of Africa (population 15.1)
with a very low seroprevalence rate, reported only 37 cases of AIDS
to WHO through November 1999.
In cohort studies, severe immunosuppression and
AIDS-defining illnesses occur exclusively in those individuals who
are HIV-infected. Conversely, matched controls, individuals with
similar lifestyles but without HIV infection, practically never
suffer from these symptoms. For example, in one cohort in Vancouver,
investigators followed 715 homosexual men for a median of 8.6 years
And the facts is that every case of AIDS reported in this cohort
occurred in individuals who were found positive for HIV antibodies.
No AIDS-defining illnesses occurred in men who remained negative for
HIV antibodies, regardless of the fact that these men and women had
highly significant patterns of illicit drug use and receptive anal
intercourse. In some studies conducted so far, the pattern has been
shown that death rates are markedly higher among HIV-seropositive
individuals than those among HIV-seronegative individuals. Excessive
mortality rate among HIV-seropositive people has also been
repeatedly observed in numerous studies conducted in many of the
developed nations, perhaps most dramatically among hemophiliacs. For
example, 6,278 hemophiliacs where studied in the United Kingdom
during the period 1977-91. Among 2,448 with severe hemophilia, the
annual death rate was stable at 8 per 1,000 during 1977-84. While
deaths rates remained stable at 8 per 1,000 from 1985-92 among
HIV-negative persons with severe hemophilia, deaths rose sharply
among those people who Became HIV-positive following HIV-tainted
transfusions during 1979-1986, reaching 81 per 1,000. The specific
immunologic profile that typifies AIDS -- a persistently low CD4+ T
cell count -- is extraordinarily rare in the absence of HIV
infection or otherwise a known cause of immunosuppression. For
example, in the MACS study, 22,643 CD4+ T-cell counts were carried
out, related to 2,713 HIV-negative men. There was only one
individual with a CD4 + T-cell count persistently lower than 300
cells/mm3. This individual was taking other drugs that would have
had an effect to his CD4 count. Nearly everyone with AIDS has
developed antibodies to HIV. A In one of the surveys conducted on
230,179 AIDS patients in the United States revealed only 299 HIV-seronegative
individuals. On further evaluation of 172 of these 299 patients it
was found that, 131 out of 172 actually were seropositive; further
to which an additional 34 died before their serostatus could be
confirmed.
HIV can be detected in virtually everyone with AIDS
as per recently developed sensitive testing methods, including the
polymerase chain reaction (PCR) and improved culture techniques
which have enabled researchers to find HIV in patients with AIDS but
with a very few exceptions to the above mentioned finding. HIV has
been repeatedly isolated from the blood, semen and vaginal
secretions of patients with AIDS, findings consistent with the
epidemiologic data demonstrating AIDS transmission via sexual
activity and contact with infected blood. The HIV-infected twins
develop AIDS while the uninfected twins do not get infected with
AIDS. Researchers have documented the cases of HIV-infected mothers
who have given birth to those twins among whom, one of them is
infected with HIV and the other is not infected. The HIV-infected
children developed AIDS, while the other children remained
clinically and immunologically normal. Studies of
transfusion-acquired AIDS cases have repeatedly led to the detection
of HIV to be very much present in the patient receiving the blood,
as well as present in the blood of the blood donor. Numerous other
studies have further revealed an almost perfect correlation between
the incidence of AIDS in a blood recipient and donor, and
substantial evidence of presence of similar HIV strains in both the
blood recipient and the blood donor. HIV causes the death of CD4+ T
lymphocytes in vitro and in vivo as CD4+ T cells are the cells that
are worn-out in people infected with AIDS. Although the loss of CD4+
T cells is not the only immune defect observed in people infected
with AIDS, the examination further discloses that HIV also infects
and damages these cells in vitro establishing an obvious link
between HIV and AIDS in an regenerative capacity.
Among the HIV-infected patients who are being
treated under the anti-HIV therapy, those whose viral loads are
driven to low levels are unlikely to develop AIDS or die than those
patients who do not respond to this therapy. This effect would not
be noticeable otherwise, sif HIV did not have a ‘crucially central
role’ to play in causing AIDS. In various clinical tests &
respective tests assessments in both HIV-infected children & adults
have established a very close link between a good virologic response
to therapy i.e. a reduced risk of developing AIDS or dying. This
effect has also been seen in routine clinical practice. For example,
in an analysis of 2,674 HIV-infected patients who started highly
active antiretroviral therapy (HAART) in 1995-1998, 6.6 percent of
patients who achieved and maintained undetectable viral loads
developed AIDS or died within 30 months, as compared with 20.1
percent of patients who never achieved undetectable concentrations.
HIV fulfils Koch's postulates as the cause of AIDS, stipulated as,
(1) the suspected cause must be strongly associated with the
disease, (2) the suspected agent can be isolated and propagated
outside the host and (3) that the transfer of the agent to an
uninfected host, man or animal, produces the disease in that host.
With regard to postulate 1), innumerous studies undertaken all over
the world manifests that, practically all AIDS patients are HIV-seropositive:
that is they are the carriers of such antibodies that indicate
HIV-infection. With regard of postulate 2), current practices have
permitted the isolation of HIV in virtually all patients suffering
from AIDS, over and above, of most of the HIV seropositive
individuals with both early-& late-stage disease. Postulate 3) has
been fulfilled in an event involving three workers working in a
laboratory without any other risk factors developed AIDS or severe
immunosuppression after accidental exposure to concentrated, cloned
HIV in the laboratory. In all the three above mentioned cases, HIV
was isolated from the infected individual, sequenced and shown to be
the infecting strain of virus.
In addition to all the facts as mentioned as above,
through December 1999, the CDC had received reports of 56 health
care workers in the United States of America alone, with well
documented, occupationally got infected, out of whom 25 workers
developed AIDS even in the absence of other risk factors. It has
also been repeatedly observed in pediatric and adult blood
transfusion cases like in the case of mother-to-child transmission.
Also in various studies of hemophilia, injecting drugs & sexual
transmission in which seroconversion can be documented using serial
blood samples the development of AIDS has followed soon after the
HIV seroconversion was seen. |
