Stress, HIV and AIDS
Res. Immunol. 1992, 143, 145-148
E. Papadopulos-Eleopulos (1) V.F. Turner (2) and J.M. Papadimitriou
Department of Medical Physics, (2) Emergency Department and (3)
Department of Pathology, (University of Western Australia), Royal
Perth Hospital, Wellington St., Perth 6001 (Western Australia)
As long ago as 1983, one of us (E.P.-E.) proposed that oxidative
mechanisms are of critical significance in the genesis of AIDS (acquired
immune deficiency syndrome). A prediction of this hypothesis was
that the mechanisms responsible for AIDS could be reversed by the
administration of reducing agents, especially those containing sulphydryl
groups (SH groups). The discovery of HIV resulted in a broadening
of this hypothesis in that it considered oxidative stress as a principal
mechanism in both the development of AIDS and expression of HIV
(Papadopulos-Eleopulos, 1988; Papadopulos-Eleopulos et al., 1989).
However, the general acceptance of the HIV hypothesis of AIDS completely
overshadowed this alternative hypothesis, and although many other
scientists have questioned the role of HIV in the causation of AIDS
(Duesberg, 1987; Root-Bernstein, 1990) Robert Gallo and most AIDS
researchers consider HIV to be the sole "sine qua non"
cause of AIDS.
some flaws, especially recently, have appeared which cast serious
doubt on the prevailing HIV/AIDS hypothesis. Luc Montagnier, the
discoverer of HIV, is presently of the opinion that cofactors are
necessary for the appearance of AIDS (Lemaitre et al., 1990). It
has been accepted by researchers at the CDC that KS (Kaposi's sarcoma),
the first and most specific of the AIDS indicator diseases, for
which the explanation of the HIV hypothesis was put forward by Gallo
in 1982, is not caused directly or indirectly by HIV (Beral et al.,
1990). On the other hand, recent empirical observations from three
seemingly unrelated areas of AIDS research are in agreement with
the hypothesis that oxidative mechanisms play a critical role in
HIV expression and AIDS development.
et al. (1985a) and more recently researchers from many other institutions
(Lang et al., 1988; Brewton et al., 1989; Reisinger et al., 1990;
Hersh et al., 1991) have shown that a reducing agent, diethyl dithiocarbonate,
previously used as an immunomodulator, and inhibitor of tumour promotion,
may be useful in improving the immune response in HIV infected individuals
and in preventing and treating AIDS. Other reducing agents have
also been found to have similar effects (Schulof et al., 1986; Wu
et al., 1989).
(2) In 1989,
Eck et al. measured the level of acid soluble-SH groups in plasma
and the intracellular concentration of reduced glutathione (GSH)
in peripheral blood mononuclear cells (PBMC) and monocytes in HIV-infected
patients: both were found to be significantly decreased. Following
the above report, Buhl et al. (1989) determined the glutathione
concentration (reduced, oxidised and total) in plasma and lung epithelial
lining fluid of symptom-free HIV seropositive individuals: in both
tissues, both the reduced and total GSH concentration was found
to be significantly decreased.
(3) In 1985,
Pompidou et al. (1985b) and more recently many other researchers
including Anthony Fauci have shown that reducing agents suppress
the expression of HIV (Scheib et al., 1987; Bitterlich et al., 1989;
Kalebic et al., 1991).
the possible therapeutic implications of reducing agents in AIDS
patients it is important to have a basic understanding as to why:
agents suppress the expression of HIV;
HIV-infected individuals and AIDS patients have decreased sulphydryl
and total glutathione levels.
and reducing agents
to the first question is encompassed in basic retroviral research
conducted over half a century. It is well known that all cells contain
retroviral genomic sequences (Martin et al., 1981 ; Callahan et
al., 1989; Nakamura et al., 1991). Recently French researchers suggested
that human DNA also contains sequences which are homologous with
the HIV genome (Parravicini et al., 1988). Many eminent retrovirologists,
including Weiss, did not exclude the possibility that retroviruses
with gene sequences not originally present in cells may arise during
the lifetime of the animal by duplication and/or recombination of
endogenous proviruses or even by rearrangement of cellular DNA,
caused by many factors including the pathogenic process itself,
and that retroviruses may be the effect and not the cause of the
disease (Weiss et al., 1971).
Temin (1974) who shared the Nobel prize with Baltimore for the discovery
of reverse transcriptase (RT) and who, from the time of its discovery
considered the enzyme to be constituent of all cells not just retroviruses,
the genome of a retrovirus (ribodeoxyvirus) may arise by rearrangement
of the normal cell genome by the following mechanism. "A section
of a cell genome becomes modified in successive DNA(w) to RNA(-)
to DNA transfers until it becomes a ribodeoxyvirus genome. First,
these sequences evolve as part of a cellular genome. After they
have escaped as a virus they evolve independently as a virus genome.
The time may be millions of years in germ-line cells and days in
somatic cells". In fact, Temin and Baltimore (1972) did not
exclude the possibility that, in at least some cases, particles
which band at 1. 16 g/ml contain RT and have morphological characteristics
similar to retroviruses, may be nothing more than cellular fragments.
Irrespective of the mechanism it is a fact, firmly established from
basic retroviral research, that retroviruses can appear even in
virus-free cultures with a rate that can be accelerated a million-fold
by radiation, infection with other viruses and mitogens (Weiss et
al., 1971 Aaronson et al., 1971).
relevance to the present discussion is the fact that all mitogenic
agents including radiation exert their biological effect by oxidation
of cellular sulphydryl groups (Papadopulos-Eleopulos, 1982).
and his associate David Klatzmann were the first to draw attention
to the fact that LAV infection of T4 cells in vitro does not lead
to HIV expression unless the cells are stimulated. "Infection
of resting T4 cells does not lead to viral replication or to expression
of viral antigens on the cell surface, while stimulation by lectins
or antigens of the same cells results in production of viral particles,
antigenic expression and the cytopathic effect" (Klatzmann
and Montagnier, 1986). Gallo also expressed the view that without
"activation" the T4 cells do not express virus (Zagury
et al., 1986). But, apparently, they did not realise that oxidative
phenomena are implicated in human T-cell stimulation (Sekkat et
As early as
1984 it was realised that in vivo HIV genomic sequences are not
always detected in tissues obtained from patients with ARC and AIDS
or, when found, the "signal" is low. According to Gallo
and his colleagues "this low signal intensity could also be
explained by the presence of a virus distantly homologous to HTLV-III
in these cells" (Shaw et al., 1984).
and his colleagues, on comparing the evidence obtained from the
study of macrophages in vivo and in vitro, concluded: "These
data indicate that the ability to isolate in vitro macrophage tropic
strains of HIV does not reflect in vivo infection of circulating
monocytes, but is related to phenomena of in vitro selection or
adaptation" (Massari et al., 1990).
(a) to date, with perhaps one exception, no two identical HIV have
been isolated, not even from the same person; in one case where
two sequential isolates were made 16 months apart, none of the provirus
in the first isolate was found in the second (Saag et al., 1988);
(b) the genetic data obtained in vitro does not correlate with the
data obtained in vivo - "To culture is to disturb" (Meyerhans
et al., 1989); (c) many, if not all, of the proviruses detected
in vivo and in vitro are defective.
This data led
researchers at the Pasteur Institute and their associates to conclude
that (1) "the task of defining HIV infection in molecular terms
will be difficult", (2) "virus isolated from PBMC may
be produced by the complementation of defective genes or by recombination
between two of them" (Meyerhans et al., 1989; Wain-Hobson,
1989). Be this as it may, of particular relevance to the present
discussion is the fact that:
a) HIV has
been isolated only from in vitro cultures;
b) no HIV can
be isolated, unless the cultures, one way or the other, are subjected
to oxidative stress, even although the tissue from AIDS patients
is already oxidised; it may be then that oxidative stress is of
pivotal significance in the detection of all retroviruses including
HIV. If oxidation is a prerequisite for HIV expression, it follows
that reducing agents will have the opposite effect: HIV will not
be expressed in their presence.
factors in AIDS patients
suffer from many opportunistic microorganisms. Like all cells, these
microorganisms require reducing equivalents, including SH, for division
and survival (Papadopulos-Eleopulos, 1982) which they obtain to
the detriment of body tissues. In AIDS patients, a decrease in the
level of SH may also result from malnutrition and diarrhoea. However,
opportunistic infections, diarrhoea and malnutrition cannot account
for the low level of GSH and acid-soluble SH found in HIV-positive,
symptom-free, well-nourished homosexuals and haemophiliacs.
production also requires thiols, which they obtain from the host,
it may be reasonable to assume that the decreased SH level in HIV-positive
individuals may be the result of HIV infection, as has already been
proposed for SIV-infected monkeys (Eck et al., 1991). However, because
for both HIV and SIV expression, oxidative stress is a prerequisite,
this cannot be the case, i.e. oxidation cannot be both the cause
and the effect of HIV expression (Papadopulos-Eleopulos et al.,
At first sight
it appears that there is no common factor, apart from HIV infection,
linking the various AIDS risk groups. However, homosexuals are exposed
to relatively high levels of nitrites and anally deposited sperm,
drug abusers to opiates and nitrites, haemophiliacs to factor VIII.
All these are known potent oxidising agents which oxidise many cellular
reducing equivalents such as NADPH and all sulphydryl groups, including
those of cysteine (acid-soluble thiols) (Papadopulos-Eleopulos,
In normal tissue
almost all glutathione is found intracellularly in the reduced form
(GSH) where it is also synthesised from glutamic acid, cysteine
and glycine, in the presence of ATP and magnesium. Cysteine which
is the rate-limiting amino acid cannot be substituted by its oxidised
form, cystine. Oxidation of cysteine (acid-soluble SH) is also known
to decrease cellular ATP and magnesium concentration (Tateishi and
Higashi, 1978; Siliprandi et al., 1987). Malnutrition and diarrhoea
may also lead to cysteine, magnesium and ATP deficiency.
As a result
of the decrease in cysteine, ATP and magnesium concentration, the
synthesis of glutathione will be inhibited. The oxidising agents
to which the AIDS risk groups are exposed would also directly oxidise
GSH to GSSG. GSSG is efficiently excreted from cells (Sies and Akerbrum,
1984). Glutathione exported across the cell membrane interacts with
gamma-glutamyl transpeptidase, an enzyme which catalyses the breakdown
of glutathione by transferring the gamma-glutamyl group to an acceptor.
It should be
noted that: cystine is one of the best acceptors for the gamma-glutamyl
group; with exception of the kidney and pancreas, the highest activity
of the enzyme is in the epididymis and seminal vesicles; the highest
concentration of its soluble form, apart from urine and pancreatic
juice, is in seminal fluid (Meister and Anderson, 1983). Thus, the
systemic decrease of glutathione concentration in HIV seropositive
individuals may result from both, decrease in synthesis and increased
degradation. The oxidative stress to which the AIDS patients are
subjected would lead to cellular anomalies in many cells, including
lymphocytes, resulting in opportunistic infection, immunological
abnormalities and neoplasia.
All this argues
in favour of oxidation as being a critical factor in the pathogenesis
of AIDS and HIV expression.
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