the crossroad of conception and infection: initiatives for immunoglobulin-based
contraceptive R & D
Family Planning Research Institute,Nanjing 210029, China
Asian J Androl 1999 Sep; 1: 87-93
AbstractBetter understanding of the immunological mechanisms implying the insemination and the infertility of some men and women is needed and crucial to the development of an effective immunocontraceptive method. To provide good protection against conception or infection, and avoid any possible and unexpected complications which immunocontraceptive vaccine may arise of, it seems the right time for scientists to create a virtually new thinking for this extremely urgent and important issue. This conceptual article describes our original thoughts of the future development of immunocontraceptives, preferably, based on immunoglobulins rather than vaccines, against human sperm specific antigens and seminal plasma immunosuppressive factors. Its general correctness, advantages and feasibility for fertility regulation and prevention of infection are discussed.
for ideal contraceptives
100 years ago, scientists learned that spermatozoa could provoke an immune
reaction if they were injected into the body. Efforts at translating this
information into a contraceptive vaccine began in the mid-1960s and focused
on inducing an immune reaction to sperm. In the mid-1970s, researchers
realized that human chorionic gonadotropin (hCG) would also be a good
candidate for a contraceptive vaccine, since this hormone is produced
only during early pregnancy. After more than 20 years of research, though,
the first small-scale human trial of an anti-hCG vaccine showed that nearly
20% of the women who received injections failed
to develop an effective immune reaction[1-2]. Research continues
on two anti-hCG vaccines, one
created by India's National Institute of Immunology and one produced
other researchers continue to explore the feasibility of developing vaccines
targeting a variety of proteins on the surface of the egg or on the surface
of the sperm, in the belief that if either gamete could be coated with
antibodies, fertilization would not take place. Another potential vaccine
is aimed at disrupting
a chemical that assists in the fusion of the sperm and egg. Scientists
have found it harder than expected to identify molecules peculiar to the
gametes or the fertilization process, however, a necessary step so as
not to provoke an autoimmune reaction among similar molecules elsewhere
in the body.
evidence for auto- or allo-immune response against sperm antigens that cause
infertility in some men and women has become definite, the
terms of immunoprophylaxis and contraceptive vaccine have unambiguously
been used in the development of immunocontraceptives.This
approach, of course, bring
some best to science but we should be careful in any practical trials. First,
conception was (and still is) not infection caused by microorganisms,
like smallpox, and
will never. Second, reproductive process is an evolutionary result
of life, in which a highly coordinating mechanism between genetic system
and immune system is involved. Third, one should be awareness of that
teaching ones body
to provoke an immune response against a self-like molecule is dangerous,
especially in the era of HIV epidemic. In contrast, one should seek some
beneficial methods to protect and improve our immune systems. In general,
current vaccine approach to fertility regulation substantially contravene
the evolutionary principles.
is not surprising that there are controversies surrounding anti-fertility
vaccines, focusing on the anti-hCG vaccine. It reflects
on the role of women's health advocating in contraceptive technology development,
and the responses of researchers
to their actions. Such controversy is also held by some top leaders in the
contraceptive research and development program. The immunocontraceptive area
is one that we've really cut back on, Gabelnick says, Not knowing
what we would get, we stopped doing new projects. Those skeptical words
sound rational to most scientists and public but might be harmful to researches
toward better understanding and manipulating our reproductive process.
But others show their positive responses to immunocontraception and are
looking for the window in which it will kill sperm and prevent infection
without toxicity effects on vaginal tissue.
The question may arise of what we are doing here, since we have never made a contraceptive vaccine and have no results to present. The reason is that two of us [Y.F. Wang and Y.F. Huang] proposed independently that if there be a method to interfere or eliminate the immunosuppressive factors in human semen, we might find out a good way toward ideal contraception[8-9]. Importantly, one of us N.Q. L in early 1990s, had been thinking about hapten-carrier phenomena[10,11], following, of course, Baruj Benacerrafs work. Central to Ls thinking in his hidden-epitope recognition model was that the nature of the immune T-cells memory is the recognition of the hidden internal structure of the same antigenic determinant as B-cell does, which reflects the restricted recognition of the immune system to a foreign molecule. The most important role of this thinking may be to interpret mysterious hapten-carrier phenomena in rather precise and sound terms. Since current immunological approaches to fertility regulation has been heavily based on the recognition of self-like molecules, and the classical hapten-carrier system is ogten employed, interactions of our thoughts about the development of immunocontraceptive vaccines and the advent of new techniques might open the door for reconsideration of our previous hypothesis and we want a place where we could look things up.
general, whenever we thought of those complicated biological problems,
we did remember what
the genetist Theodosius Dobzhansky said, events in biology will be of
significance only if one thinks it from an evolutionary view [Scientific
American (1985) 253: 4, August].
We also appreciated what one of us [Y.F. Wang] put it some time
ago, immunoinfertility in some men and women could be considered
as the results of contraceptive experiments God conducts in human beings,
if you do understand the implying mechanisms, you might find a good way
to manage ones fertility process.
present evidence, therefore, it would be worthwhile among others to search
for future contraceptive candidates in immunoglobulins rather than vaccines.
Since vaccines are
usually directed against foreign microorganisms or their products,
antifertility vaccines will be directed against self-like molecules.
Therefore, vaccine approaches to fertility regulation will certainly increase
the difficulties in all aspects the vaccine would raise, such as the social, ethical,
legal and regulatory issues. We do not intend to argue the feasibility of
such antifertility vaccines approaches. What we want to do is just to
discover the applications of anti-semen antibodies and to use them. That
will simplify the problems.
2 Immunoglobulin-based passive immunocontraceptionImmunoglobulin-based passive immunocontraception is defined as the application of immunoglobulins against human sperm specific antigens and seminal plasma immunosuppressive factors as contraceptives for fertility regulation and prevention from infection. Its scientific rationale was originated from the investigations of spermatozoal antigens initiated at the end of the last century by Landsteiner and Metchnikoff. In the years following those landmark studies, the literature on reproductive immunology grew at such a rapid pace that it is now difficult to present in this concept article an in-depth review of the immunology of the reproductive system together with that of pregnancy and the female reproductive tract. Only those most attractive findings are cited hereinafter to synthesize, define and support the new concept of immunocontraception.
Advantages of passive immunocontraception
immunization, the administration of exogenously produced antibodies raised
against a reproductive substance, has until recently been limited to
the use of
sera derived from non-human species. In the case of such
application to birth control in humans, the repetitive use of animal sera
has been considered hazardous because of possible reactions to foreign
proteins. However, the recent development of new technology for producing
human immunoglobulins in vitro from transgenic technology and genetic
vaccine techonology opens the door for
reconsideration of passive immunization as a safe method of immunological
immunization procedures have the advantage of allowing control over the
nature of antibodies employed and duration of use of the method. The major disadvantage
is that the duration of effectiveness from a single application is usually
only a few days. However, following advantages will make it most attractive
to both scientists and individuals.
Immunoglobulins against a sperm component of fertility specific can be
shown to completely block the fertility of experimental animals, e.g,
fertilization protein-1 (FA-1)
in sperm-based-immunocontraceptive approaches are critically reviewed
by Naz recently. FA-1 has been purified and characterized
from murine and human sperm and testis using an MCA that completely blocks
murine IVF and human SPA. FA-1 is a glycoprotein. It exists as both a
dimer (51.2 kDa) as well as monomer (23 kDa). FA-1 develops in the testis
during later stages (secondary spermatocyte onward) of spermatogenesis.
FA-1 is an evolutionarily conserved antigen present in sperm of various
mammalian species including mouse, rabbit, bull, rhesus monkey, and humans.
FA-1 seems to have the similar function in these species. Anti-FA-1
MCA completely blocked IVF in these species. Also, the active immunization
of female rabbits with purified FA-1 caused a significant reduction (up
to complete block) in fertility.
mechanism by which the anti-FA-1 antibodies inhibit fertilization is by
affecting sperm-zona interaction. The human FA-1 binds to purified ZP3
of porcine zona pellucida in enzyme-linked immunosorbent assay (ELISA)
and Western blotting, and completely neutralizes its sperm ligand activity
in boar sperm-porcine zonapellucida attachment bioassay. This is an interesting
finding because antibodies to
porcine ZP3 antibodies have been shown to cross-react with human zona
pellucida. The antibodies to FA-1 inhibit human sperm-human zona interaction,
reinforcing the concept that FA-1 is involved in sperm-zona pellucida-ligand
interaction. However, in the heterologous assay, the FA-1 MCA completely
blocks SPA. The SPA
has been reported to be an indirect measure of capacitation. Thus it is
conceivable that these antibodies are directed to an important sperm component
(enzymatic or non-enzymatic) that is vital to capacitation. In fact, the
immunoaffinity-purified FA-1 MCA inhibits acrosome reaction of human sperm
cells in solution (but not on the zona pellucida surface), suggesting
a mechanism through which the antibody can inhibit the human sperm penetration
of zona-free hamster oocytes. Recently, Naz and colleagues found that
the purified FA-1 antigen completely blocks human sperm-human zona binding
in the hemizona assay. Taken together, these findings suggest that FA-1
antigen may be a human sperm receptor (ligand) for the
zona pellucida, that also has a role in sperm cell capacitation and/or
acrosome reaction. It is interesting to find that FA-1 antigen has an
autophosphorylating activity and is tyrosine phosphorylated during human
sperm capacitation/acrosome reaction. Tyrosine phosphorylation of FA-1
antigen seems to have a vital role in capacitation/acrosome reaction and
in zona pellucida binding.
Immunoglobulins against sperm developed in the majority of men after vasectomy
can not affect the health of the individual
antigen is involved in human immunoinfertility (both men and women).
The available data indicate that the anti-FA-1 antibodies that are present
in vasectomized men and in infertile patients may play a causal rather
than an associated casual role in infertility. Involvement of an antigen
in human immunoinfertility indicates: a) its immunogenicity (auto- as
well as iso-) in humans, and b) potential
of its antibodies in causing infertility if a sufficient antibody titer is
present. Since most infertile men are healthy individuals without any
disease concomitant with infertility, the presence of antibodies to an
antigen, is indicative, though not confirmative of its sperm specificity
in humans. Thus, the
involvement of FA-1 in immunoinfertility indirectly indicates its sperm-specificity,
and auto- as well as isoantigenic potentials in humans. Thus, if an antigen, such
as FA-1 is involved in human immunoinfertility, the extensive phase I
clinical trials to investigate its toxicity in actively-immunized subjects
may not be absolutely necessary.
Immunoglobulins per se do not prepare host to provoke both humoral and
cellular immune response against target molecules
has been demonstrated by those classical experiments that passive immunization
of animals with antibodies does not prepare the animals to provoke both
humoral and cellular immune response against the corresponding antigen[10-11].
Therefore, the use of immunoglobulin-based contraceptives will not stimulate
individuals immune response against sperm antigens at all.
Immunoglobulins could neutralize sperms ejaculated into virgina without
activating complement system if the immunoglobulins are chicken immunoglobulins
major concern is then focused on if the immune complex of sperm-antibody
could activate females
complement factors. Recent data show that chicken antibodies in
their reactions with mammalian constituents do not activate the mammalian
complement system [http://www.immunsystem.se/Advantages.html: IgY does
not activate complement factors. Updated 13 August 1998].
Immunoglobulins against HIV/STDs infectious organisms could be produced
by hens and involved
in the contraceptive formula
an extra advantage, immunoglobulins against HIV/STDs could be produced
by hens in large amount and cost-effectively. In addition, chicken is
one of the most infection resistant animals as far as we know. Therefore,
use of the combination of
immunglobulins against both semen and HIV/STDs as contraceptives will
provide women and men with good protection for birth control and infection.
All women, by virtue of their cycles, face some level of immunosuppression in reproductive tract[16-17]. Data suggest that repeated exposure to semen will facilitate the transmission of virus and establishement of infection when all depositions of semen occur, but systemic absorption would also be possible by vaginal intercourse if lesions or abrasions acused for example by other STD's. Although some population of women may experience a higher risk of infection than others, it is almost impossible to predict, on an individual basis, who will develop a life-threatening complication. It is therefore critical that all women have access to passive immunocontraceptives if and when the needs arise.
Immunoglobulins when orally taken up will survive through the gastrointestinal
tract in healthy adult volunteers, implying their potential applications
for human therapy of immunoinfertility and HIV/STDs infection
Concerns that if the orally uptake of immunoglobulins can reach the local site of reproductive tract to play their roles are reasonable. Knowledges about the two functions of the immune system in the gut are now available: (1) to protect the host from enteric infections by viruses, bacteria and parasites; and (2) to minimize the induction of immune responses (both antibody and cell-mediated) to the immense and varied load of food antigens, the vast majority of which do not present a threat to the integrity of the host. Indeed, the induction of such immune responses could pose a greater risk to the host than any of the antigens themselves.
results of many experiments have shown that a state of tolerance develops
after ingesting a wide dose range of a protein such as ovalbumin (OVA)
so that a subsequent parenteral challenge with OVA results in a 90%-100%
reduction in the systemic immune response compared with that of control
animals. Even though very low doses
of OVA may induce immunity, this tolerant state can persist for up to
two years after the
Recent data show that immunoglobulins from different species can survive through the gastrointestinal tract in healthy adult volunteers, suggesting their potential implications for human therapy.
Immunoglobulin formula could be most easily accessible to vagina by female herself
immunoglobulins like those produced by ourselves immune system are virtually
harmless and can protect individuals from conception and infection, therefore,
will be generally acceptable by individuals worldwide. We consulted many
colleagues both males and females and got rather positive response to
accept such formula as a contraceptive choice.
Immunoglobulins from chicken will be most easily produced in large amount
4 Global perspectives
is a global problem of significant magnitude, with grave implications
for the future. It is now generally accepted that the currently
available methods of fertility regulation are inadequate to meet the varied
and changing personal needs of couples at different times in their reproductive
lives and in the widely different geographical, cultural, religious, and
service settings that exist around the world. On the other
hand, the global HIV epidemic continues to expand at an alarming rate.
The current epidemics of AIDS and other sexually transmitted diseases
(STDs) have created an urgent need for a new type of contraceptive: one
that is both a spermicide and a microbicide.
of the steady decline in both industry and foundation support for contraceptive
research, it seems the right time to integrate very limited
resources but great pool of wisdom to tackle this urgent problem and initiate
a pilot study on this approach, since those techniques are already sophisticated
and scientific rationales are sound. Supplemented to traditional immunobiology
and immunochemistry, both transgenic techniques and genetic vaccine techniques
will find their most potentials in this area.
engineered hens for this purpose are encouraged in order to further decline
the cost. First, IgY should not direct against non-reproductive specific
components. Second, IgY should direct against sperm specific antigens,
like FA-1, and
plasma immunosuppressive factors. Third, if applicable, IgY should arm
its ability to neutralize HIV envelop protein, like gp120 and other STDs
cDNA encoding for the FA-1 antigen has been cloned and sequenced from
murine testis. Naz
and colleagues also have isolated two putative clones from the human testis
C gt11 cDNA expression library which react with FA-1 MCA.
The functional epitope of FA-1 antigen, recognizing the FA-1 MCA, has
been isolated, sequenced and synthesized. Interestingly, the sera from
immunoinfertile patients (men
and women) and not from fertile humans show a strong reaction with this
synthetic decapeptide epitope, and the decapeptide-reactive immunoaffinity-purified
antibodies inhibit human SPA. Northern blot analysis of mRNA isolated
from various human tissues, confirmed the testis-specific expression of
the FA-1 antigen in
humans. Active immunization trials using the synthetic decapeptide epitope
as well as purified recombinant antigen obtained by expression using the
pGEX system are being planned in a non-human primate model.
have understood more about the HIV than any other virus. However, development
of vaccine capable of anti-HIV infections remains severe challenge as
it faced when the virus was discoved. The problem is, unlike
the human immune response against most acute virus infections, natural
immune response does not destroy
HIV. This defeat makes researchers unable to understand that an effective
vaccine should initiate what immune activity.
of the greatest concerns to such research has been the increasing awareness
of possible contributions of human seminal plasma immunosuppressive factors
and infections. Evidence for human immunosuppression status during insemination
has been well documented over the years. The immunosuppressive contributions
to fertilization are mainly made by males seminal plasma immunosuppressive
factors although female also prepare herself with lowest level of immune
response against sperms during ovulation.
findings of the presence of a CD4-binding glycoprotein, namely
gp17 (apparent MW=17 500 Da) in human seminal plasma may be relevant to
the control of sexual transmission of HIV-1. Since its binding to CD4
was inhibited by anti-CD4 mAbs directed against V1, a region
of CD4 implicated in the binding to MHC class II
antigens and to the HIV-1 envelope protein gp120, but not by mAbs directed
against other CD4 determinants.
this 17-kDa CD4-binding glycoprotein is also expressed in
mammary tumor cells upon hormone treatment and in biopsies from
breast cancer patients. The finding that breast cancer cells express a
protein able to interact with the CD4 domains involved in the
recognition of class II major histocompatibility antigens suggests a possible
mechanism by which a tumor may affect the activity of tumor-infiltrated
researches of fertilization and HIV infection have been
separated as two relatively independent fields although some authors
have expressed their concerns
on the possible mechanisms by which human immunosuppression status during
insemination might contribute to infections by microorganisms. From the
analyses of the accumulated data, the possible links between human seminal
plasma immunosuppressive factors, HIV infection and tumor genesis are
emerging. A better understanding of those complicated phenomena is needed
for future therapy development.
is not overestimated that overpopulation and rapid prevelance of HIV infections
are threatening our future. We claim and draw public attention to this
matter, probably because there is a mythic force that govern and balance
between human beings
reproductive system and immune system, and no currently available methods
can manipulate it without any unacceptable complications. Of course, currently
available methods of fertility regulation can not meet the practical demands
for fertility regulation and prevention of infection. Therefore, development
of successful strategies for contraception and primary prevention of HIV
infection in women must be a top public health priority.
5 AcknowledgementsThis work was supported partly by Jiangsu Science & Technology Commission 1998 under the aid to N.Q. L.
Aldhous P. A booster for contraceptive vaccines. Science 1994; 266: 1484-6.
to Nian-Qing LÜ,