Just as assisted reproductive technology (ART) is used to bypass anatomic blocks and defects in gamete production, so should it be used to overcome infertility associated with infectious disease. HIV infection in the male embodies many of the controversial medical, social, and technical issues that surround infertility in those with infectious disease.
Setting aside for a moment the social and ethical issues associated with using medical techniques to create children for fathers who have an incurable, life-threatening disease, the next question is: Can ART provide safe conception with sperm from an HIV-infected father? If that is not possible today, will it ever be possible?
Like all retroviruses, HIV is a fragile pathogen, dependent upon the integrity of its outer membrane to gain access to its host cell. Even minor insults to its membrane may prevent infection. Once inside, it must carry out a unique and complex life cycle to establish a productive infection. In contrast to other viral infections, new HIV is produced relatively slowly, or not at all.
These characteristics lead to both the insidious nature of HIV diseaseit is transmitted only by intimate exchange of blood or genital tract fluids and the new infection may go undiscovered for yearsand to its vulnerabilityunique, critical steps in its life cycle provide several targets for antiviral strategies. It became clear a decade ago that reproductive strategies would one day be needed for couples with HIV, given the fact that thousands of men with hemophilia had accidentally been infected with the disease through blood-factor products, and because sexually transmitted pathogens particularly plague young adults in their child-bearing years.1 This is especially true today, with the development of effective antiviral treatment strategies for HIV.
For HIV-infected men, the needed reproductive strategy is straightforward: Create a pregnancy with virus-free sperm. The question is, is it possible? Given the nature of HIV, the answer is undoubtedly yes for some HIV-infected men, and perhaps not for others. Herein lies the principal basis for concern: how to determine with certainty that the fertilizing sperm is not infected. Taken one step further, how do we guarantee that even if the fertilizing sperm is infected, it will not result in an infected mother and/or baby?
The complexity of these infectious disease issues has led to the current refusal by ART programs in the United States to assist HIV-infected men. In addition, the physicians treating their disease also discourage HIV-infected men from having children in order to avoid the risk of disease transmission, the stress of parenting in the face of coping with a serious illness, and the social problems related to families with no father. Similar reasoning by adoption agencies rules out most possibilities for HIV-infected men to adopt an infant. In many cases, therefore, the result of lack of support from the health-care community leads to markedly increased risk to women for whom donor sperm and not having children are intolerable options, because they then resort to natural intercourse for conception.
The solution to these problems is to treat HIV infection as another form of male-factor infertility and devise ART methods to ensure infection-free pregnancies. Central to this task is understanding the nature of the relationship between sperm and HIV in semen. Unfortunately, in spite of the fact that the global HIV pandemic is principally due to sexual transmission, semen infection with HIV has not been a major research focus and remains poorly understood. Semen infection is a complex issue since the testis, epididymis, seminal vesicles, and prostate gland are involved in production of semen and it exits via ejaculatory ducts and the urethra, in contact with their epithelia and glands. In addition to the involvement of multiple organs, spermatozoa are isolated and protected from exposure to the immune system. This increases the likelihood that semen HIV infection is not simply a transudate from blood. Recent work from several laboratories, including our own, supports the view that sexually transmitted HIV arises from isolated reservoirs within the semen-producing organs.2-5
Transmissible HIV infection may be in the form of either free virus or virus-infected cells, which are thought to transmit infection either by continuing to produce free virus in the recipient, or to fuse with the recipient's host cells. The risk of HIV transmission is difficult to measure, but is estimated to be on the order of 1 in 100 to 1 in 200 sexual encounters between an HIV-infected male and an uninfected female.6 If the semen viral burden is high, transmission rates may be higher. Measurements of HIV in semen have led to surprisingly variable results, from lows of 4% of semen specimens to highs of 87% of semen specimens.7,8 Work in our laboratory has shown significant discordance between semen and blood with respect to burden of HIV-infected leukocytes.4 Consistent findings, however, are that not all semen specimens from an individual are positive for virus, that most specimens are positive for either free virus or for virus-infected cells, but usually not both, and that spermatozoa themselves are negative for virus. The possibility that not all sperm are negative for virus has been raised by reports that some patients with AIDS may have HIV-infected testicular germ cells and that under some conditions, virus may bind to sperm.9
Given the confusion, what safe ART measures are available today? Certainly advantage can be taken of the findings that some semen specimens from all men studied appear to be virus-free. Thus, a feasible approach is to cryopreserve half of several semen specimens and thoroughly test the other half. The testing regimen will need to include measures to compensate for the problems inherent in routine semen analyses. For example, a commonly overlooked limit to estimating the number of potential HIV host cells in a semen specimen is the fact that the ratio of spermatozoa to somatic cells usually masks the number of somatic cells present. The lower limit to a hemacytometer, the most common microscope counting chamber, is 10,000 cells per counting grid and the upper limit is about 25 million. Thus, 9,000 HIV host cells per mL of semen would be scored as "zero" in the presence of 25 million sperm. Other counting chambers are less sensitive.
For both manual and computer-imaging system counting, semen specimens are diluted to ranges suitable for the chamber being used. Thus, since normal sperm concentrations range between 20 and 100 million sperm per mL of semen, and sperm counts are generally normal for HIV-infected men, tens of thousands of potential HIV host cells could contaminate a sperm preparation without being detected by either manual or computer-based microscopy systems for quantifying sperm.10
In addition, although polymerase chain reaction-based (PCR) testing methods are sensitive to a few copies of HIV genes, either viral RNA in free virus or proviral DNA inside infected cells, PCR is limited at the upper end by the amount of nucleic acid that can be included in one assay.11 This upper limit is not an important factor in detecting viral RNA in either blood or seminal plasma, but it plays an important role in testing semen cell populations. More than approximately 100,000 cell equivalents of DNA overwhelms the PCR reaction, yielding false-negative results. Thus, in order to detect fewer than one infected cell in 100,000 uninfected cells (including sperm) to adequately evaluate the millions of sperm necessary for fertilization, multiple PCR reactions need to be performed.
Motile sperm can be purified away from other semen cells and seminal plasma by standard procedures currently employed in ART centers. As an additional safety measure, the motile sperm fraction can be treated with specialized research reagents designed to attract and bind specific types of cells and pathogens. For example, magnetic beads coated with antibodies against antigens common to all leukocytes and/or to free HIV virions can be used to bind trace levels of contamination with potential HIV host cells and virus. Such magnetic beads are removed simply by magnetic attraction and are common laboratory reagents for cell purification procedures.
Although these testing protocols are stringent and require multiple semen specimens, such approaches are the most likely to yield "safe" sperm populations.
Assuming virus-free sperm are available, the next major question is what form of ART should be used? An Italian clinic has pioneered the use of purified sperm fractions for intrauterine insemination. Although prior semen testing for HIV was not always used, none of the over 1,000 inseminations performed in that clinic has been reported to transmit infection to the women or the more than 120 babies born.12 These results are significantly more promising than similar approaches in the US, which unfortunately led to infection transmission. This has caused the Centers for Disease Control and Prevention to caution against the safety of such approaches.13
All things considered, the safest ART at this time is fertilization in vitro. First, fewer sperm are needed for IVF, thus limiting the possibility of undetected contaminating virus and HIV host cells in the purified sperm fraction. IVF also provides the opportunity to assist couples with additional infertility problems, such as low sperm count or tubal occlusion. Secondly, exposure of eggs to sperm in vitro for only 1 hour leads to normal rates of fertilization and perhaps improved rates of embryo development, work confirmed in this laboratory.14 Thus, the eggs can be transferred into fresh culture conditions within a short time, further limiting their exposure to seminal cells. Third, the mother is exposed only to fertilized eggs at the time of embryo transfer, not directly to sperm or semen. Fourth, for those men with persistent HIV in semen, it is feasible to utilize intracytoplasmic sperm injection (ICSI) for fertilization if only a small population of HIV-negative sperm can be obtained. This is not the preferred treatment for all until the safety of ICSI has been proved. And finally, if indicated, IVF affords the opportunity to biopsy one cell from the embryo to test for the presence of HIV, just as embryos are biopsied to test for genetic disorders.15
These considerations suggest that the answer to the question posed at the beginning of this review, "Can ART provide safe conception with sperm from HIV-infected men?" is "yes", providing the outcome of the sensitive molecular biology assays identifies semen specimens with no detectable virus. For those men whose semen specimens contain virus, the situation is problematic and will require additional testing and evaluation of the potential risks of infection transmission to the mother and child. Although it is now clear that HIV provirus would be expressed in fertilized human eggs, no information is available about whether or not eggs or early cleaving embryos can be productively infected by HIV.16 Information from embryo transfers in cattle suggests that eggs and embryos themselves are highly resistant to viral infection and do not transmit infection to surrogate mothers.17 Nonetheless, the observation that sperm can serve as vectors for DNA transmission into eggs, giving rise to transgenic offspring, heightens the need for caution in using sperm from HIV-infected men whose semen specimens consistently contain virus.18
Assuming that IVF with HIV-free sperm can be proved to be a safe, reliable procedure for achieving an HIV-free pregnancy, the next question is should ART programs assist in this endeavor? The issues are more complex than obvious at first.
One is a societal issue based on concerns about health-care providers assisting in creating children who might have only one healthy parent. The most appropriate parallel in this regard is men with other serious illnesses, such as those with severe diabetes, hemophilia, hepatitis, or cancer. Since ART is not routinely withheld from such men, it seems inappropriate and unethical, perhaps even unlawful, to apply a different standard of health-care availability to HIV-infected men. This is of particular concern in light of the marked improvement in the health status of infected men on aggressive antiretroviral therapies.
Another issue that is not generally appreciated but which may prove to be fundamentally important to the species is reducing the risk of creating offspring transgenic for HIV. All animal species examined have retroviral genes within their DNA, thought to be remnants of ancient retroviral infections that became integrated into germline DNA. Such endogenous viruses comprise on the order of 1% of the DNA of mice and several full-length retroviruses have been isolated from human DNA, supporting the concept that our ancestors suffered from retroviral infections.19 This confirms that the risk is real, albeit certainly rare, that natural conceptions with HIV-contaminated semen could lead to transgenicity for HIV in the offspring. The species impact of such an event cannot be predicted, but in the absence of information, avoiding this possibility is the best course. For this reason, the health-care community may actually have an obligation to provide ART to couples determined to parent, in order to avoid the risks of HIV transmission inherent in natural intercourse.
In summary, the need for the health-care community to develop guidelines for assisting HIV-positive men to have children remains urgent. The rise in the presence of other human retroviruses, such as human T-cell leukemia virus, in the general population further increases the urgency of the need. The power of the human urge to procreate, even in the face of serious illness, warrants the respect and aid of the health-care community, including the development of specialized ARTs to improve safety to the mother and to future generations.
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Controversies in OB/GYN focuses on controversial issues pertaining to the clinical practice of obstetrics and gynecology and reproductive medicine. The authors have been selected for their ability to articulate a particular point of view, regardless of their own personal convictions.
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David B. Seifer, MD, Series Editor
Department of Obstetrics, Gynecology, and Reproductive Sciences
UMDNJ-Robert Wood Johnson Medical School
New Brunswick, N.J.
Ann Kiessling. Should ART be used to help an HIV-infected man father a child? Yes..