Recovery of human immunodeficiency virus type 1 from semen: minimal impact of stage of infection and current antiviral chemotherapy

HIV treatment as prevention and HPTN 052

PURPOSE OF REVIEW

This review summarizes the development and implementation of a large clinical trial, HIV Prevention Trials Network (HPTN) 052, whose initial results were recently presented and published.

RECENT FINDINGS

A randomized, clinical trial demonstrated that antiretroviral therapy reduces the sexual transmission of HIV in HIV-serodiscordant couples by more than 96%. The logistical challenges in preparing for and conducting such a trial were considerable.

SUMMARY

HPTN 052 required many years of preparation, considerable collaboration between National Institute of Health and six pharmaceutical companies, and careful ongoing consideration of a large number of ethical issues. HPTN 052 revealed the magnitude of benefit when using antiretroviral therapy to prevent the transmission of HIV, and served as proof of a concept. The results have proven central to the development of new global HIV-prevention efforts.

HIV-1 does not significantly influence Chlamydia trachomatis serovar L2 replication in vitro

Individuals with lymphogranuloma venereum (LGV), caused by Chlamydia trachomatis serovar L2, are commonly co-infected with human immunodeficiency virus type 1 (HIV-1), for reasons that remain unknown. One hypothesis is that a biological synergy exists between the two pathogens. We tested this by characterising for the first time in vitro C. trachomatis L2 replication in the presence of HIV-1. The human epithelial cell-line, MAGI P4R5 was infected with C. trachomatis L2 and HIV-1 (MN strain). Co-infected cultures contained fewer and larger chlamydial inclusions, but the inclusions did not contain morphologically aberrant organisms. C. trachomatis remained infectious in the presence of HIV-1 and showed neither an alteration in genome accumulation, nor in the acumulation of ompA, euo or unprocessed 16S rRNA transcripts. However, omcB was slightly elevated. Taken together, these data indicate that HIV-1 co-infection did not significantly alter C. trachomatis replication and the association between HIV-1 and LGV is likely due to other factors that require further investigation. The fewer, larger inclusions observed in co-infected cultures probably result from the fusion of multiple inclusions in HIV-1 induced syncytia and indicate that C. trachomatis-host-cell interactions continue to function, despite considerable host-cell re-modelling.

Prior mucosal exposure to heterologous cells alters the pathogenesis of cell-associated mucosal feline immunodeficiency virus challenge

BACKGROUND

Several lines of research suggest that exposure to cellular material can alter the susceptibility to infection by HIV-1. Because sexual contact often includes exposure to cellular material, we hypothesized that repeated mucosal exposure to heterologous cells would induce an immune response that would alter the susceptibility to mucosal infection. Using the feline immunodeficiency virus (FIV) model of HIV-1 mucosal transmission, the cervicovaginal mucosa was exposed once weekly for 12 weeks to 5,000 heterologous cells or media (control) and then cats were vaginally challenged with cell-associated or cell-free FIV.

RESULTS

Exposure to heterologous cells decreased the percentage of lymphocytes in the mucosal and systemic lymph nodes (LN) expressing L-selectin as well as the percentage of CD4+ CD25+ T cells. These shifts were associated with enhanced ex-vivo proliferative responses to heterologous cells. Following mucosal challenge with cell-associated, but not cell-free, FIV, proviral burden was reduced by 64% in cats previously exposed to heterologous cells as compared to media exposed controls.

CONCLUSIONS

The pathogenesis and/or the threshold for mucosal infection by infected cells (but not cell-free virus) can be modulated by mucosal exposure to uninfected heterologous cells.

HIV infection of the male genital tract--consequences for sexual transmission and reproduction

Despite semen being the main vector of human immunodeficiency virus (HIV) dissemination worldwide, the origin of the virus in this bodily fluid remains unclear. It was recently shown that several organs of the male genital tract (MGT) are infected by HIV/simian immunodeficiency virus (SIV) and likely to contribute to semen viral load during the primary and chronic stages of the infection. These findings are important in helping answer the following questions: (i) does the MGT constitute a viral reservoir responsible for the persistence of virus release into the semen of a subset of HIV-infected men under antiretroviral therapy, who otherwise show an undetectable blood viral load? (ii) What is the aetiology of the semen abnormalities observed in asymptomatic HIV-infected men? (iii) What is the exact nature of the interactions between the spermatozoa, their testicular progenitors and HIV, an important issue in the context of assisted reproductive techniques proposed for HIV-seropositive (HIV+) men? Answers to these questions are crucial for the design of new therapeutic strategies aimed at eradicating the virus from the genital tract of HIV+ men--thus reducing its sexual transmission--and for improving the care of serodiscordant couples wishing to have children. This review summarizes the most recent literature on HIV infection of the male genital tract, discusses the above issues in light of the latest findings and highlights future directions of research.

Acute mucosal pathogenesis of feline immunodeficiency virus is independent of viral dose in vaginally infected cats

BACKGROUND

The mucosal pathogenesis of HIV has been shown to be an important feature of infection and disease progression. HIV-1 infection causes depletion of intestinal lamina propria CD4+ T cells (LPL), therefore, intestinal CD4+ T cell preservation may be a useful correlate of protection in evaluating vaccine candidates. Vaccine studies employing the cat/FIV and macaque/SIV models frequently use high doses of parenterally administered challenge virus to ensure high plasma viremia in control animals. However, it is unclear if loss of mucosal T cells would occur regardless of initial viral inoculum dose. The objective of this study was to determine the acute effect of viral dose on mucosal leukocytes and associated innate and adaptive immune responses.

RESULTS

Cats were vaginally inoculated with a high, middle or low dose of cell-associated and cell-free FIV. PBMC, serum and plasma were assessed every two weeks with tissues assessed eight weeks following infection. We found that irrespective of mucosally administered viral dose, FIV infection was induced in all cats. However, viremia was present in only half of the cats, and viral dose was unrelated to the development of viremia. Importantly, regardless of viral dose, all cats experienced significant losses of intestinal CD4+ LPL and CD8+ intraepithelial lymphocytes (IEL). Innate immune responses by CD56+CD3- NK cells correlated with aviremia and apparent occult infection but did not protect mucosal T cells. CD4+ and CD8+ T cells in viremic cats were more likely to produce cytokines in response to Gag stimulation, whereas aviremic cats T cells tended to produce cytokines in response to Env stimulation. However, while cell-mediated immune responses in aviremic cats may have helped reduce viral replication, they could not be correlated to the levels of viremia. Robust production of anti-FIV antibodies was positively correlated with the magnitude of viremia.

CONCLUSIONS

Our results indicate that mucosal immune pathogenesis could be used as a rapid indicator of vaccine success or failure when combined with a physiologically relevant low dose mucosal challenge. We also show that innate immune responses may play an important role in controlling viral replication following acute mucosal infection, which has not been previously identified.

Sexual transmission of HIV-1

HIV-1 transmission occurs in a limited number of ways all of which are preventable. Overall, the risk of HIV-1 transmission following a single sexual exposure is low especially in comparison with other sexually transmitted infections (STIs); with estimates of the average probability of male to female HIV-1 transmission only 0.0005-0.0026 per coital act. The risk of acquiring HIV-1 from a single contact varies enormously and is dependant upon the infectiousness of the HIV-1 positive individual and the susceptibility to HIV-1 of their sexual partner. An understanding of the determinants of HIV-1 transmission is important not only to assess the infection risk to an individual when exposed to the virus (e.g. to determine the provision of post exposure prophylaxis), but also to make accurate predictions on the potential spread of HIV-1 infection in a population and to direct appropriate targeted prevention strategies. In this review article we summarise the current literature on the major worldwide source of HIV-1 acquisition, sexual transmission. This article forms part of a special issue of Antiviral Research marking the 25th anniversary of antiretroviral drug discovery and development, Vol 85, issue 1, 2010.

Heterosexual spread of HIV infection

Sexual transmission is the most common route of spread of human immunodeficiency virus (HIV), with heterosexual transmission of HIV infection accounting for 90% of those infected in 1992 and over 75% of the 10–12 million of those infected to date worldwide. Yet, heterosexual transmission is poorly understood. Since HIV can be transmitted from HIV-infected people who are asymptomatic as well as from those who have the acquired immunodeficiency syndrome (AIDS), we must better define the potential for transmission of HIV from HIV-infected individuals as well as the factors which influence the susceptibility of HIV-uninfected individuals.

Human immunodeficiency virus viral load in blood plasma and semen: review and implications of empirical findings

The majority of human immunodeficiency virus (HIV) infections in the world are sexually transmitted and quantities of HIV in genital fluids are an important transmission risk-determining factor. Estimating men's sexual HIV infectiousness from blood viral load hinges on the association between HIV in blood plasma (BPVL) and semen viral load (SVL). This article reviews research on the association between BPVL and SVL as reported in 19 empirical studies (N = 1226). Findings yielded a mean correlation between BPVL and SVL of 0.45 (SD = 0.20, median = 0.45, range = 0.07-.64). SVL was generally lower than BPVL, but this pattern was variable across studies. Co-occurring sexually transmitted infections (urethritis), nonsuppressive HIV treatments, and drug resistance account for the variability in observed correlations. HIV disease progression does not reliably influence the association between BPVL and SVL. Research is needed to determine the degree to which BPVL as well as SVL predict HIV transmission.

Mucosal challenge with cell-associated or cell-free feline immunodeficiency virus induces rapid and distinctly different patterns of phenotypic change in the mucosal and systemic immune systems

The majority of human immunodeficiency virus type 1 (HIV-1) infections occur via mucosal transmission through contact with genital secretions containing cell-associated and cell-free virus. However, few studies have assessed whether exposure to cells, HIV-1 infected or uninfected, plays a role in the sexual transmission of HIV-1. This study examined phenotypic changes in mucosal and systemic lymphoid tissue 24 hr after vaginal exposure to in vitro equilibrated infectious doses of cell-associated or cell-free feline immunodeficiency virus, uninfected heterologous cells, or medium alone. We found that even at this early time-point, mucosal exposure to virus induced substantial alterations in the phenotype and distribution of leucocytes, particularly in the tissues of the mucosal immune system. Second, we found that the type of virus inoculum directly influenced the phenotypic changes seen. Vaginal exposure to cell-free virus tended to induce more generalized phenotypic changes, typically in the peripheral immune system (blood and systemic lymph nodes). In contrast, exposure to cell-associated virus was primarily associated with phenotypic shifts in the mucosal immune system (gut and mucosal/draining lymph nodes). In addition, we found that exposure to uninfected heterologous cells also induced alterations in the mucosal immune system. These data suggest that significant immune changes occur within the first 24 hr of virus exposure, well before substantial replication would be anticipated. As the mucosal immune system, and particularly the gut, is an early and persistent target for lentiviral replication, these findings have substantial implications for HIV-1 pathogenesis and vaccine development.

Lower levels of HIV RNA in semen in HIV-2 compared with HIV-1 infection: implications for differences in transmission

BACKGROUND AND OBJECTIVES

HIV-2 infection, in comparison with HIV-1, is characterized by lower plasma viral loads, slower CD4 cell count decline, decreased AIDS-related mortality, and lower rates of mother-to-child and sexual transmission. To gain further insight into why HIV-1 is more readily transmitted as compared with HIV-2, we analyzed semen and plasma HIV RNA levels in HIV-1 and HIV-2-positive men from Senegal.

DESIGN AND METHODS

Twenty-two HIV-1 and 10 HIV-2-infected subjects from the University of Dakar donated semen and blood samples for this analysis. HIV-1 and HIV-2 viral loads in semen and plasma were quantified using type-specific polymerase chain reaction assays.

RESULTS

The mean age of the subjects was 37 and 40 years; mean CD4 cell count was 222 and 276 cells/microl and the mean plasma viral load was 4.7 and 3.0 log10 copies/ml for HIV-1 and HIV-2, respectively (P = 0.002). HIV RNA was detected in semen in 21 of 22 (95%) of HIV-1 and seven of 10 (70%) of HIV-2-infected subjects; P = 0.07). However, the levels of HIV RNA present in semen were markedly different between those with HIV-1 and HIV-2, with a mean of 4.4 log10 copies/ml among those with HIV-1 and a mean of 2.6 log10 copies/ml among those with HIV-2 (P < 0.001). In multivariate analysis, plasma viral load and HIV type, but not CD4 cell count, were independently predictive of semen viral load (P = 0.03, 0.05, 0.48, respectively)

CONCLUSIONS

These data suggest that differences in semen viral load between HIV-1 and HIV-2 may be in part responsible for the markedly different transmission rates of these two viruses. In addition, risk of male genital tract shedding strongly correlates with plasma viral loads. Interventions that decrease viral load may help decrease transmission of both HIV-1 and HIV-2.

Effects of candidate vaginally-applied microbicide compounds on innate immune cells

Ideally, a vaginally-applied microbicide would be effective against a broad range of pathogens but would have minimal effects on the female genital tract. The aim of this study was to determine if representative candidate detergent-type and sulfated/sulfonated polymer-type microbicides altered the composition or function of innate immune cells normally found in the vaginal mucosa. The effect of microbicide on the composition of vaginal leukocytes was tested using a flow cytometric approach. Application of the detergent cholic acid, but not the sulfated polysaccharide lambda carrageenan, resulted in a significant increase in macrophages at the vaginal epithelial surface compared to control treatment (19.3% macrophages compared to 2.8%; p<0.0004). Phagocytosis of fluorochrome-labeled bacteria by macrophages was inhibited greater than 50% in the presence of 1.0mg/ml of the sulfonated polymer PRO 2000 but was not inhibited by the same concentration of lambda carrageenan. PRO 2000-pulsed macrophages regained phagocytic function after being washed free of the compound. Culture of macrophages with PRO 2000 also resulted in diminished detection of the surface proteins CD11b and CD18. After treated cells were washed free of PRO 2000, these proteins were detected at levels similar to control treated cells. In conclusion, application of a detergent-type microbicide, but not a sulfated polymer, resulted in the infiltration of inflammatory cells at the vaginal epithelial surface. Phagocytic function of macrophages was lost in the presence of 1mg/ml PRO 2000 which may have reflected masking of important cell surface proteins by the microbicide; however, there was no evidence of permanent loss of function upon removal of the compound.

Persistent HIV type 1 infection in semen and blood compartments in patients after long-term potent antiretroviral therapy

HIV-1 RNA levels in semen and blood compartments decrease below detection limits during highly active antiretroviral therapy. Despite these therapeutic effects, it is clear that persistent, latent HIV-1 reservoirs are capable of rebounding in the absence of drug treatment or by evolution of escape mutants remain. The current study was designed to examine the presence of latent virus in semen and blood compartments and its evolution following potent combination therapy with indinavir (protease inhibitor) and efavirenz [nonnucleoside reverse transcriptase (RT) inhibitor]. Using an ultrasensitive in situ hybridization assay HIV-1 mRNA was detected in cultured seminal and blood mononuclear cells in all patients up to 1789 days posttherapy. Higher levels of HIV-1 mRNA were consistently detected in seminal mononuclear cells as compared to peripheral blood mononuclear cells (PBMC) in all time points analyzed posttherapy. Analysis of viral RNA from cultured PBMC before and after therapy displayed no evidence of therapy-induced drug resistance in the viral polymerase gene in the majority of patients. However, distinct envelope populations were detected in these viral RNA populations following therapy, indicating possible selection of quasispecies. The observed ongoing replication and evolution in the PBMC viral envelope sequences likely occurred in the seminal compartment HIV populations, given that the seminal cells showed the ability to express HIV-1 mRNA following cultivation. This together with our previous studies (Gupta P, et al.: J Infect Dis 2000;182:79-87) suggest that the genital and blood compartments likely serve as distinct reservoirs harboring latent HIV-1 during prolonged drug therapy.

Carrageenan formulation prevents macrophage trafficking from vagina: implications for microbicide development

Considerable evidence suggests that human immunodeficiency virus (HIV)-infected macrophages and/or lymphocytes may mediate sexual transmission of HIV. We and others have previously demonstrated that when vitally stained donor mouse lymphocytes or macrophages are placed in the vaginas of mice, some of the stained cells can later be found in the iliac lymph nodes. The aim of this study was to assess the extent of mononuclear cell trafficking from the vagina and to test the possibility that carrageenan formulation, a sulfated polysaccharide formulation containing 3% PDR98-15 carrageenan (PC-515; FMC Biopolymer, Rockland, ME), a vaginal microbicide, would prevent vaginal transmigration of macrophages. When supravitally stained mouse macrophages and T cells were inoculated into the vagina of recipient mice, discrete numbers of donor cells migrated to the recipient iliac and inguinal lymph nodes and spleen. When recipient mice were preinoculated with the carrageenan formulation, the number of macrophages in lymph nodes and spleen was reduced by >90%. In contrast, a methylcellulose formulation, which is believed to be inactive, did not significantly reduce migration to the lymphoid organs. Our findings suggest that the carrageenan formulation blocks cell trafficking of macrophages from vagina and that blocking does not result from cytotoxicity. Blocking cell trafficking may help to prevent sexual transmission of HIV.

Assisted reproductive technology for men and women infected with human immunodeficiency virus type 1

In 2001, the World Health Organization reported 4.3 million new human immunodeficiency virus (HIV) infections in adults globally, 41% of which were in women. During the year 2000, 27% of newly diagnosed HIV infections in the United States occurred in women. In developed countries, the perception of HIV infection has changed from an acute, lethal infection to a chronic illness; the introduction of highly active antiretroviral therapy has decreased morbidity and mortality, and new drug therapies have dramatically decreased perinatal transmission. In view of these advances, some HIV-infected individuals are considering reproduction. Following the lead of organizations in other developed countries, the American College of Obstetricians and Gynecologists has recently endorsed the use of reproductive technology in HIV-infected patients. Which patients should be offered assisted reproduction and what the optimal methods are of decreasing heterosexual and perinatal HIV transmission must be determined.

Detection of classical swine fever virus in boar semen by reverse transcription-polymerase chain reaction

A seminested reverse transcription-polymerase chain reaction (RT-PCR) was developed for the detection of classical swine fever virus (CSFV) in semen. Five boars were inoculated intranasally with CSFV isolate propagated in PK15 cells. Two boars inoculated with the supernatant of noninfected PK15 cells were kept as controls. Semen and serum samples were collected twice weekly for 63 days postinoculation (dpi). Samples were tested for the presence of antibodies to CSFV by an enzyme-linked immunosorbent assay and for the presence of CSFV nucleic acid by seminested RT-PCR. Antibodies to CSFV could be detected as early as 7 dpi in 1 boar, and all 5 infected boars were found positive by 14 dpi. CSFV from boar semen was infrequently identified by virus isolation compared with seminested RT-PCR. CSFV nucleic acid was detected in semen by seminested RT-PCR as early as 7 dpi in 3 infected boars and persistently thereafter in all 5 infected boars until 63 dpi. When separated fractions of CSFV-contaminated semen were analyzed by the seminested RT-PCR, the CSFV nucleic acid was detected mainly in seminal fluid and occasionally in nonsperm cells. CSFV antigen was also detected in nonsperm cells from semen smear by immunohistochemistry. Thus, infection via semen, specially through CSFV-infected seminal fluid, seems to be a major route of transmission of CSFV.

Evaluation of FIV protein-expressing VEE-replicon vaccine vectors in cats

Venezuelan equine encephalitis (VEE) virus-replicon particles (VRP) were used to generate feline immunodeficiency virus (FIV) Gag- and ENV-expressing vaccine vectors. Serum and mucosal FIV-specific antibody was detected in cats immunized subcutaneously, once monthly for 5 months, with FIV-expressing VRP. Expansion of the CD8+ L-selectin negative phenotype and transient CD8+ noncytolytic suppressor activity were seen in cats immunized with FIV-expressing or control VRP. Despite induction of FIV-specific immune responses and nonspecific suppressor responses, all cats became infected following vaginal challenge with high dose, pathogenic cell-associated FIV-NCSU(1) although relative early maintenance of CD4+ cells was seen in FIV-immunized cats.

Subcompartmentalization of HIV-1 quasispecies between seminal cells and seminal plasma indicates their origin in distinct genital tissues

The mononuclear cells and plasma components of semen from HIV-infected subjects have been shown to contain HIV-1. However, there is very little information as to whether distinct HIV-1 population are present in these two seminal compartments or as to their tissue of origin. Phylogenetic analysis of nucleotide sequences of the C2-V5 region of the HIV-1 gp120 from HIV-1 RNA isolated from seminal cells and seminal plasma of five subjects indicates that the HIV-1 population derived from seminal plasma was distinct from that present in seminal cells. Such subcompartmentalization of HIV-1 between seminal cells and seminal plasma was detected as early as 3 months after seroconversion and persisted up to 38 months following seroconversion. Furthermore, comparison of HIV-1 sequences between testis and prostate tissues showed distinct HIV-1 populations in these tissue compartments. In situ real-time (Taqman) PCR analysis of prostate and testis tissues indicated that T lymphocytes were the predominant cells infected with HIV-1 in both of these tissues. Since seminal plasma is derived from prostate and most of the seminal cells originate from the rete testis and epididymis, these results are consistent with the idea that HIV-1 in seminal plasma is derived from the prostate, while HIV-1-infected cells in semen originate mostly from the rete testis and epididymis. These findings provide for the first time evidence of subcompartmentalization of HIV-1 in male genital organs and suggest that intervention strategies such as vasectomy may not prevent sexual transmission.

Considerations and development of topical microbicides to inhibit the sexual transmission of HIV

The increased incidence of HIV/AIDS disease in women aged 15 - 49 years has identified the urgent need for a female-controlled, efficacious and safe vaginal topical microbicide. To meet this challenge, new topical microbicide candidates consisting of molecules or formulations that modify the genital environment (BufferGel, engineered Lactobacillus, over-the-counter lubricants), surfactants (C31D/Savvy, sodium dodecyl sulfate, sodium lauryl sulfate), polyanionic polymers (PRO 2000, beta-cyclodextrin, Carraguard, CAP, D2S, SPL-7013), proteins (cyanovirin-N, monoclonal antibodies, thromspondin-1 peptides, Pokeweed antiviral protein and others), reverse transcription inhibitors (PMPA [Tenofovir ]), UC-781, SJ-3366, DABO and thiourea) and other molecules (NCp7-specific virucides, chemokine receptor agonists/antagonists, WHI-05 and WHI-07) are currently being investigated for activity, safety and efficacy. This review will assess the development of these molecules in the context of cervicovaginal defences and the clinical failure of nonoxynol-9.

Residual HIV-1 disease in seminal cells of HIV-1-infected men on suppressive HAART: latency without on-going cellular infections

BACKGROUND

HIV-1-infected men on suppressive highly active antiretroviral therapy (HAART) have a reduction of viral replication in vivo, but HIV-1 RNA is still detectable by certain ultrasensitive reverse transcriptase-PCR assays in blood plasma. Replication-competent virus can also be isolated from both peripheral blood mononuclear cells (PBMC) and seminal cells of these patients. Despite HAART, on-going in vivo infection of HIV-1-seropositive patients' PBMC was demonstrated by the detection of episomal HIV-1 moieties, known as HIV-1 two-long terminal repeat (2-LTR) DNA circles.

METHODS

The present study analyzes whether new cellular infections occur in vivo in seminal cells of HIV-1-infected men on suppressive HAART. PBMC and seminal cells were isolated from a cohort of HIV-1-seropositive men taking suppressive HAART (< 50 copies HIV RNA/ml blood plasma). Viral growth assays were performed in vitro, as well as semi-quantitative PCR to detect HIV-1 2-LTR circular DNA in PBMC and seminal mononuclear cells.

RESULTS

Viral growth in vitro was demonstrated in 16 out of 28 (57%) patients' PBMC, and in five patients' seminal cells (18%). Although 18 patients' PBMC were positive for HIV-1 2-LTR DNA circles, importantly, 2-LTR circular DNA was not detected in any semen sample, even when replication-competent HIV-1 virus had been recovered from a patient's seminal cells by viral co-culture assays.

CONCLUSIONS

The current study suggests that in HIV-1-infected men treated with suppressive HAART, new cellular infections occur in PBMC, but that new infections do not take place in seminal cells in vivo. Thus, these findings suggest that mainly latent HIV-1 occurs in seminal cells of men on suppressive HAART, which may be a compartment-specific mechanism of residual HIV-1 disease.

Binding of LFA-1 (CD11a) to intercellular adhesion molecule 3 (ICAM-3; CD50) and ICAM-2 (CD102) triggers transmigration of human immunodeficiency virus type 1-infected monocytes through mucosal epithelial cells

Transmigration of human immunodeficiency virus (HIV)-infected mononuclear cells through the genital mucosa is one of the possible mechanisms of sexual transmission of HIV. Here, we investigated the transmigration of cell-associated R5-tropic HIV type 1 (HIV-1) through a tight monolayer of human epithelial cells in vitro. We show that this process is dependent on an initial interaction between alphaLbeta2 integrin CD11a/CD18 on infected monocytic cells and intercellular adhesion molecule 2 (ICAM-2; CD102) and ICAM-3 (CD50) on the apical membrane of epithelial cells. The CD50 and CD102 ligands were overexpressed on epithelial cells when the cells were activated by proinflammatory cytokines in the cellular microenvironment. An accumulation of proviral DNA was found in the transmigrated cells, clearly reflecting the preferential transepithelial migration of HIV-1-infected cells under proinflammatory conditions. Our observations provide new insights supporting the hypothesis that HIV-infected mononuclear cells contained in genital secretions from infected individuals may cross the epithelial genital mucosa of an exposed receptive sexual partner, particularly under inflammatory conditions of damaged genital tissue. Understanding the fundamental aspects of the initial HIV entry process during sexual transmission remains a critical step for preventing human infection and developing further vaccinal strategies and virucidal agents.

Differentiation of porcine circovirus (PCV)-1 and PCV-2 in boar semen using a multiplex nested polymerase chain reaction

A multiplex nested polymerase chain reaction (PCR) was developed for the detection of and differentiation between porcine circovirus (PCV)-1 and PCV-2 in boar semen. Eighteen (30%) and 30 (50%) out of 60 whole semen samples were found to be positive for PCV using multiplex conventional PCR and multiplex nested PCR, respectively. Of the 30 positive samples obtained using multiplex nested PCR, two were found to be positive for PCV-1 only, eight for PCV-2 only, and 20 for PCV-1 and PCV-2. When the separated fractions of PCV-contaminated semen were analyzed using multiplex nested PCR, PCV DNA was found to be present mainly in the seminal fluid and nonsperm cell fractions. When compared with the virus isolation method commonly used to detect viruses, this PCR assay was found to be more sensitive and rapid and, as such, may prove to be a good alternative method for the detection of and differentiation between PCV-1 and PCV-2 in boar semen.

[Medically assisted reproduction and the desire for a child by HIV infected couples: has the time for a change in attitude come?]]

Today, in developed countries, many HIV-infected people remain in good health thanks to antiviral medication. A growing number of them want to have children. Medical possibilities for preventing contamination of the partners of seropositive men through assisted reproduction and of children thanks to antiviral medicines during pregnancy are summarized. These changes result in ethical considerations which lead the authors to question the conventional systematic medical advise against pregnancy and has encouraged them to assist reproduction for a number of these couples. Today, the balance between the importance of the message of prevention and the benefit for patients of being assisted in their desire for a child has tilted towards medical intervention. It would seem legitimate today to intervene in the most favourable situations rather than see these couples take the risk of spontaneous conception outside health care structures. This implies to adapt medical structure (separate laboratory, appropriate procedure, precise protocols). This approach, which is coherent from the scientific point of view, respects both the autonomy of people carrying HIV as well as the essential interest for the child, in "being" born uninfected and also has the enormous advantage of allowing access to parenthood without destroying the consistency of the message of prevention of sexual contamination.

Antiretroviral drug concentrations in semen of HIV-1 infected men

Because semen is a major vehicle for the sexual transmission of HIV-1, control of viral replication within the sanctuary of the male genital tract should be a goal of antiretroviral therapy. Local immune responses, virus specific factors, and the degree of viral and cellular trafficking all appear to be important in controlling viral replication and evolution. However, the most important factor influencing viral replication and evolution within the male genital tract may be the disposition of antiretroviral agents into genital tissues and fluids. This review proposes possible mechanisms of antiretroviral distribution into the male genital tract by using other sanctuary barriers; such as the placenta, renal tubules, and blood-brain barrier; as models. In addition, this review summarises recent clinical studies regarding the disposition of currently available antiretroviral drugs into the seminal plasma and discusses some of the difficulties in interpreting drug concentration in the genital tract.

Emerging concepts in gastrointestinal aspects of HIV-1 pathogenesis and management

GASTROENTROLOGY 2001;120:607-621

Multicenter evaluation of methods to quantitate human immunodeficiency virus type 1 RNA in seminal plasma

We have evaluated two commercially available kits (AMPLICOR MONITOR [Roche] and NASBA HIV-1 QT or NucliSens HIV-1 QT [Organon Teknika]) and two noncommercial methods for the accurate quantitation of human immunodeficiency virus type 1 (HIV-1) RNA in seminal plasma. The same panels of coded specimens were tested on four separate occasions. Laboratories using the commercial assays employed silica beads to isolate HIV-1 RNA, which removed inhibitory factors sometimes found in seminal plasma. Sensitivities and specificities, respectively, for each assay were as follows: AMPLICOR MONITOR, 100 and 73%; NASBA HIV-1 QT, 84 and 100%; NucliSens HIV-1 QT, 99 and 98%; and noncommercial assays, 91 and 73%. When results from the laboratory that was inexperienced with the silica bead extraction method were excluded from the analysis, specificity for the Roche assay increased to 100%. The commercial assays demonstrated highly reproducible results, with intra-assay standard deviations (measured in log(10) RNA copies/milliliter of seminal plasma) ranging from 0.11 to 0.32; those of the noncommercial assays ranged from 0.12 to 0.75. Differences in mean estimated HIV-1 RNA concentrations were </=0.67 log(10) and were greater at low viral loads. Suspension matrices that used blood plasma or seminal plasma did not make a difference in recovery of HIV-1 RNA, which suggested that blood plasma specimens can be used as external controls for seminal plasma assays. More variation in the HIV-1 RNA viral loads was observed in the seminal plasma values than in the blood plasma values when paired specimens from HIV-1-infected men were tested. Quantitation of HIV-1 RNA in seminal plasma can be reliably accomplished using two commercially available assays, and may be incorporated into the evaluations of HIV-1 seropositive men enrolled in clinical studies.

Simultaneous determination of lamivudine and zidovudine concentrations in human seminal plasma using high-performance liquid chromatography and tandem mass spectrometry

A HPLC-MS-MS method was developed and validated to measure lamivudine and zidovudine simultaneously in small volumes of human seminal plasma. Sample preparation was simple and rapid, requiring 25 microl of sample, the use of isotopically labeled lamivudine and zidovudine as internal standards and ultrafiltration through a molecular mass cut-off membrane. Lamivudine and its internal standard were separated from zidovudine and its internal standard with isocratic HPLC. Detection was carried out using tandem mass spectrometry. This validated method was used to analyze seminal samples obtained from six HIV-positive patients prescribed lamivudine and zidovudine.

Effect of coinfection with STDs and of STD treatment on HIV shedding in genital-tract secretions: systematic review and data synthesis

OBJECTIVE

To determine whether coinfection with sexually transmitted diseases (STD) increases HIV shedding in genital-tract secretions, and whether STD treatment reduces this shedding.

DESIGN

Systematic review and data synthesis of cross-sectional and cohort studies meeting predefined quality criteria.

MAIN OUTCOME MEASURES

Proportion of patients with and without a STD who had detectable HIV in genital secretions, HIV load in genital secretions, or change following STD treatment.

RESULTS

Of 48 identified studies, three cross-sectional and three cohort studies were included. HIV was detected significantly more frequently in participants infected with Neisseria gonorrhoeae (125 of 309 participants, 41%) than in those without N gonorrhoeae infection (311 of 988 participants, 32%; P = 0.004). HIV was not significantly more frequently detected in persons infected with Chlamydia trachomatis (28 of 67 participants, 42%) than in those without C trachomatis infection (375 of 1149 participants, 33%; P = 0.13). Median HIV load reported in only one study was greater in men with urethritis (12.4 x 104 versus 1.51 x 104 copies/ml; P = 0.04). In the only cohort study in which this could be fully assessed, treatment of women with any STD reduced the proportion of those with detectable HIV from 39% to 29% (P = 0.05), whereas this proportion remained stable among controls (15-17%). A second cohort study reported fully on HIV load; among men with urethritis, viral load fell from 12.4 to 4.12 x 104 copies/ml 2 weeks posttreatment, whereas viral load remained stable in those without urethritis.

CONCLUSION

Few high-quality studies were found. HIV is detected moderately more frequently in genital secretions of men and women with a STD, and HIV load is substantially increased among men with urethritis. Successful STD treatment reduces both of these parameters, but not to control levels. More high-quality studies are needed to explore this important relationship further.

Potent antiretroviral treatment of HIV-infection results in suppression of the seminal shedding of HIV. The Swiss HIV Cohort Study

OBJECTIVE

The amount of HIV in semen likely influences infectiousness. Antiretroviral therapy decreases HIV-RNA in semen, but data on HIV concentrations in semen in a large cohort of men with suppressed HIV-RNA in blood is unavailable.

METHODS

Male patients with a treatment-induced reduction of HIV-RNA load in plasma below 400 copies/ml were asked to donate a semen and blood sample. Blood and seminal plasma were tested for the presence of HIV-RNA by the NucliSens method (detection limit 400 copies/ml). Seminal cell samples from 67 patients were further analysed for the presence of HIV-DNA using a nested DNA-polymerase chain reaction. Results of RNA and DNA testing in semen were compared with 55 HIV-positive antiretroviral therapy-naive men.

RESULTS

A total of 114 patients participated in the study. Seminal plasma HIV-RNA was detectable in only two patients [1.8%, 95% confidence ratio (CI), 0-4.2%] compared with a detection frequency of 67% in untreated controls [Odds ratio (OR), 0.01; 95% CI, 0-0.03]. Detection of cell-associated HIV-DNA in semen was significantly less frequent (16 versus 38%) in patients receiving suppressive therapy compared with untreated controls (OR, 0.32; 95% CI, 0.12-0.80).

CONCLUSION

In patients with treatment-induced suppression of blood viral load the likelihood of having detectable HIV in semen is very low (< 4%). In addition, seminal shedding of cell-free and cell-associated HIV is significantly lower than in an untreated population of HIV-infected asymptomatic men. On a population basis, this effect of therapy may help to reduce sexual transmission of HIV. However, individual patients may still be infected as evidenced by continued shedding of cells harbouring the HIV provirus.

Hydrogels containing monocaprin have potent microbicidal activities against sexually transmitted viruses and bacteria in vitro

OBJECTIVE

To investigate the in vitro microbicidal and cytocidal potency of monocaprin dissolved in pharmaceutical hydrogel formulations and to evaluate their potential use as vaginal microbicides against sexually transmitted pathogens such as herpes simplex virus type 2 (HSV-2), human immunodeficiency virus type 1 (HIV-1), Chlamydia trachomatis, and Neisseria gonorrhoeae.

METHODS

Gel formulations were mixed with equal volumes of virus/bacteria suspensions in culture medium and incubated for 1 and 5 minutes. The reduction in virus/bacteria titre was used as a measure of microbicidal activity. Similarly, gels were mixed with human semen to study their effect on leucocytes. The toxicity of the gels was tested in rabbits by the standard vaginal irritation test.

RESULTS

Gels containing 20 mM of monocaprin caused a greater than 100,000-fold inactivation of HSV-2 and Neisseria in 1 minute and of Chlamydia in 5 minutes. Similarly, the gels caused a greater than 10,000-fold inactivation of HIV-1 in semen in 1 minute. They caused more than a 10,000-fold reduction in the number of viable leucocytes in semen in 1 minute. No toxic effect on the vaginal mucosa of rabbits was observed after daily exposure for 10 days.

CONCLUSIONS

Hydrogels containing monocaprin are potent inactivators of sexually transmitted viruses and bacteria in vitro. This simple lipid seems to be a feasible choice as a mucosal microbicide for prevention of sexually transmitted infections. It is a natural compound found in certain foodstuffs such as milk and is therefore unlikely to cause harmful side effects in the concentrations used.

A Combination of Nucleoside Analogues and a Protease Inhibitor Reduces HIV-1 RNA Levels in Semen: Implications for Sexual Transmission of HIV Infection

Direct contact with semen is the major route of sexual acquisition of human immunodeficiency virus (HIV) in homosexual and heterosexual partners of seropositive men. In this study, we show that concentrations of HIV-1 RNA molecules in plasma and semen of seropositive patients are related to the duration and type of anti-retroviral agents used in treatment. In patients treated with zidovudine alone, 1, 3 and 6 months after the start of therapy, the mean HIV-1 load in plasma was reduced by 0.57, 0.38 and 0.21 log10 and in semen by 0.66, 0.50 and 0.15 log10, respectively. In patients treated with zidovudine plus didanosine at months 1, 3 and 6, the mean decrease in plasma HIV-1 RNA was 1.40, 1.25 and 1.12 log10 and in semen 1.10, 1.41 and 1.32 log10, respectively. In patients treated with a combination of a protease inhibitor and two nucleoside analogues the mean log10 decrease was 1.77, 1.83, 1.71 and 2.38 log10 in plasma and 1.17, 1.74, 2.19 and 3.02 log10 in semen at 1, 2, 3 and 4 months, respectively. Treatment with a combination of a protease inhibitor and two nucleoside analogues caused a dramatic decrease in cell-free HIV-1 RNA in semen, which is a reliable measure of viral load. These findings could have implications for the sexual transmission of HIV-1.

Human immunodeficiency virus type 1 in the semen of men receiving highly active antiretroviral therapy

BACKGROUND

Highly active antiretroviral therapy can effectively decrease the levels of human immunodeficiency virus type 1 (HIV-1) virions in peripheral plasma and seminal fluid of infected men. Whether the genital tract of HIV-1-infected men who are receiving highly active antiretroviral therapy and who have no detectable virus in the peripheral plasma harbors replication-competent virus is not known.

METHODS

We collected peripheral-blood and semen samples from seven men with HIV-1 infections who were receiving highly active antiretroviral therapy and who had no detectable viral RNA (fewer than 50 copies per milliliter) in plasma and analyzed the samples for cell-associated proviral DNA using a quantitative polymerase-chain-reaction assay. Replication-competent viruses were evaluated by cell-coculture assays. Proviral DNA and replication-competent virus obtained from peripheral-blood and seminal cells were also analyzed by sequencing relevant viral genes.

RESULTS

Despite the long-term suppression of HIV-1 RNA in the plasma of the seven men, proviral DNA was detected in seminal cells in four. Replication-competent viruses were recovered from peripheral-blood cells in three men and from the seminal cells in two of these three men. The viruses recovered from the seminal cells had no genotypic mutations suggestive of resistance to antiretroviral drugs and were macrophage-tropic, a feature that is characteristic of HIV-1 strains that are capable of being sexually transmitted.

CONCLUSIONS

In HIV-1-infected men who are receiving highly active antiretroviral therapy and who have no detectable levels of viral RNA in plasma the virus may be present in seminal cells and therefore may be capable of being transmitted sexually.

HIV and germinal cells: how close an association?

Whether semen from someone who is HIV-positive can be prepared so that it is safe for insemination is a critical question particularly to couples in which the male is seropositive and the female is seronegative. It is reassuring that some investigators have reported great success in using sperm washing to dramatically reduce HIV levels in the ejaculate. Such reports suggest that if free virus and leukocytes in the seminal plasma are removed, the specimen may be safe for insemination. Whether the virus ever is associated with spermatozoa themselves is not fully understood. In situ hybridization as well as electron microscopic studies have suggested the presence of viral particles but whether these are preparation artifacts or evidence of viable viral DNA is not known. Studies of whether the virus is incorporated into developing spermatozoa or is shed in the reproductive tract will aid in the elucidation of sexual transmission of HIV.

Analysis of human immunodeficiency virus in semen: indications of a genetically distinct virus reservoir

It is well established that HIV is found in semen, either as cell-free or cell associated virus, yet many questions remain about the source of the virus. A number of factors, including anatomic features of the male reproductive tract, the restricted access of the immune system to the germ cell compartment, and the results from sexually transmitted virus studies, suggest that the source of HIV in semen may be different from that in the peripheral blood. In this study, we examine the HIV in the infected cells of semen as indicators of the virus producing reservoir. The frequency of HIV positive leukocytes in semen is compared to that of concurrent blood samples from eight donors and these values are found to be highly variable and frequently discordant. The protease gene sequences of HIV strains isolated from semen cells and blood cells were determined and phylogenetic analyses were performed which indicate the virus populations in the two sources are genetically distinct. In one patient receiving anti-HIV protease inhibitor therapy, gene sequences indicative of protease inhibitor resistance were found in the blood, but not the semen cell compartment. These results suggest that HIV in the semen and blood compartments are distinct, and further, may respond differently to antiviral therapy.

Modulation of integrin function inhibits HIV transmission to epithelial cells and fertilization

Integrin-mediated adhesive interactions are viewed in the context of HIV transmission to susceptible cells and fertilization. The ability of a low-molecular-weight non-peptide integrin modulator to inhibit HIV infection (virus-to-cell and cell-to-cell) and sperm-egg fusion is demonstrated. It is concluded that integrin-modulating substances offer significant promise as female-controlled means for preventing sexual transmission of HIV (whatever entity acts as HIV vector in semen and other penile secretions) and as female-controlled contraceptives.

Effect of antiretroviral therapy and viral load on the perceived risk of HIV transmission and the need for safer sexual practices

BACKGROUND

Dramatic reductions in plasma HIV RNA levels are possible with current antiretroviral regimens; the effect of potent therapies and "undetectable" viral load on the perceived risk of HIV transmission and need for safer practices remains unknown.

METHODS

A questionnaire was developed to examine perceptions of HIV transmission risk and need for safer practices with unprotected anal, vaginal, and oral sex and intravenous drug use with needle sharing for HIV-discordant couples in which the HIV-infected partner was receiving no therapy, was receiving reverse transcriptase inhibitor therapy, and protease inhibitor (PI)-based therapy with viral load "undetectable". This was applied anonymously to 147 unselected HIV-infected individuals attending a university-based HIV clinic.

RESULTS

Almost all respondents believed that all sexual activities except oral sex were "very risky" and that safer practices were "extremely important" for those not receiving antiretroviral agents. Significantly fewer considered that anal or vaginal sex was "very risky" for those receiving PI therapy (90.9% and 86.0%, respectively), and fewer thought that safer practices for anal or vaginal sex were "very important" for those receiving PI therapy (93.0% and 91.6%, respectively). In total, 20.4% thought the risk of HIV transmission for at least one activity was reduced for those receiving PI therapy, and 19.0% believed that the need for safer practices was reduced by PI therapy.

CONCLUSION

A small but significant proportion of HIV-infected people perceive the need for safer practices to be reduced during antiretroviral therapy, particularly those containing PIs. Even if the risk is truly reduced, the importance of safer practices should be conveyed consistently and terms such as "undetectable" to describe HIV RNA responses should be avoided.

Feline immunodeficiency virus is shed in semen from experimentally and naturally infected cats

Although a laboratory isolate of feline immunodeficiency virus (FIV), FIV-NCSU1, has been transmitted by artificial insemination in domestic cats, transmission by naturally infected males during mating has not been reported. In order to determine whether virus shedding in semen is unique to the NCSU1 isolate, we analyzed electroejaculates from four specific-pathogen-free males infected with another laboratory strain, FIV-Petaluma, and eight random source males with naturally acquired infections. Seminal cell lysates from the cats infected with the Petaluma isolate were screened by nested polymerase chain reaction amplification for FIV gag DNA. Seminal cells and seminal plasma from these FIV-Petaluma cats were further analyzed for the presence of virus by cocultivation with a feline CD4+ T cell line and Crandell feline kidney cells. Electroejaculates from the naturally infected cats were cocultivated with the T cell line. Our results demonstrated that cell-free FIV was present in seminal plasma from two FIV-Petaluma cats and two naturally infected cats. Cell-associated seminal virus was detected in all of the FIV-Petaluma infected cats and one naturally infected cat. Secretion of viral gag p26 antigen, an indication of active viral replication, was evident in cocultures containing motile sperm purified by a swim-up procedure from a FIV-Petaluma cat. These results confirm that FIV shedding in semen is not restricted to a specific virus isolate. Furthermore, swim-up sperm from FIV-infected cats may be infectious in vitro.

Effects of clinical stage and immunological status on semen analysis results in human immunodeficiency virus type 1-seropositive men

Complete semen analyses including computer-assisted sperm motility and morphology assessments were performed to determine if semen and sperm differed between HIV-seropositive men and fertile controls, or differed with symptoms, or CD4+ peripheral cell count categories. Previous studies included small numbers of men and presented conflicting conclusions. Two hundred and fifty non-vasectomized HIV-seropositive men and 38 fertile controls each provided one semen sample. Non-parameteric statistics were used to analyse both continuous and nominal data. Fertile men had significantly greater semen volume, sperm concentration, percent motility, percent rapid and linear motility and total strictly normal spermatozoa than HIV seropositive men. Neither total number nor subtypes of leukocytes in semen differed between the two groups. Among the HIV seropositive men, significant differences in semen analyses were found between CD4+ cell count, clinical, and AIDS categories. Lower CD4+ cell counts (< 200 mm-3) were associated with significantly lower percent motility, percent normal sperm morphology by strict criteria, significantly more spermatids in semen, and higher percentages of teratozoospermia, oligoasthenoteratozoospermia and leukocytospermia. Healthier men, based on clinical categories, had significantly more normal shaped spermatozoa and fewer had azoospermia, oligoasthenoteratozoospermia or leukocytospermia. Many HIV-seropositive men have normal semen analyses, but as the disease progresses more defects are found, particularly in strict criteria sperm morphology.

Presence and cellular distribution of HIV in the testes of seropositive subjects: an evaluation by in situ PCR hybridization

Cellular distribution of HIV-1 proviral DNA has been studied, by in situ PCR hybridization, in the testes of infected men who died at various stages of the disease. In seropositive asymptomatic subjects, HIV-1 proviral DNA was present in the nuclei of germ cells at all stages of their differentiation. The presence of provirus did not induce germ cell damage, was associated with normal spermatogenesis, and was not accompanied by morphologic signs of immune response. The observed HIV hybridization pattern of germ cells suggests clonal infection. Mechanisms responsible for HIV penetration in testicular germ cells remain to be clarified; however, the possibility of a direct infection of the germ cells by cell-free virus is suggested. In the testes of AIDS-deceased men, histologic features of hypoplasia with arrested spermatogenesis were evident, and few infected spermatogonia and spermatocytes were observed. The whole of these data demonstrates that the testis is a site of early viral localization that fails to elicit an immunological response, and that HIV-seropositive men produce infected spermatozoa that are released in the genital tract.

The associations between cervicovaginal HIV shedding, sexually transmitted diseases and immunosuppression in female sex workers in Abidjan, Côte d'Ivoire

OBJECTIVE

To measure the frequency and associated factors of cervicovaginal HIV shedding and to determine the impact of sexually transmitted disease (STD) treatment on HIV shedding.

DESIGN

Cross-sectional study with 1-week follow-up.

SETTING

Confidential clinic for female sex workers in Abidjan, Côte d'Ivoire.

PARTICIPANTS

A total of 1201 female sex workers.

INTERVENTIONS

STD treatment based on clinical signs.

MAIN OUTCOME MEASURES

HIV serostatus; cervicovaginal HIV shedding at enrollment and at 1-week follow-up; STD status at enrollment and at 1-week follow-up.

RESULTS

Cervicovaginal shedding of HIV-1 in HIV-1-seropositive women was more frequent (96 out of 404, 24%) than shedding of HIV-2 in HIV-2-seropositive women [one out of 21, 5%; odds ratio (OR), 6.2; 95% confidence interval (CI), 1.0-261]. Among 609 HIV-1-seropositive or dually seroreactive women, HIV-1 shedding was significantly more frequent in immunosuppressed women [adjusted OR (AOR), 6.3; 95% CI, 3.4-11.9; and AOR, 2.9; 95% CI, 1.6-5.0 for CD4 < 14% and CD4 14-28%, respectively, versus CD4 > 28%], and in women with Neisseria gonorrhoeae (AOR, 1.9; 95% CI, 1.2-3.0), those with Chlamydia trachomatis (AOR, 2.5; 95% CI, 1.1-5.8), and with a cervical or vaginal ulcer (AOR, 3.9; 95% CI, 2.1-7.4). HIV-1 shedding decreased from 42 to 21% (P < 0.005) in women whose STD were cured.

CONCLUSIONS

These data help to explain the difference in transmissibility between HIV-1 and HIV-2 and the increased infectiousness of HIV in the presence of immunosuppression and STD. In addition, they lend biological plausibility to arguments for making STD control an integral part of HIV prevention strategies in Africa.

High viral load in semen of human immunodeficiency virus type 1-infected men at all stages of disease and its reduction by therapy with protease and nonnucleoside reverse transcriptase inhibitors

Seminal viral load is likely to be directly related to the sexual transmissibility of human immunodeficiency virus type 1 (HIV-1). However, it is not clear whether the level of HIV-1 in semen varies with the stage of infection and whether antiretroviral therapy reduces seminal viral load. A nucleic acid sequence-based amplification (NASBA) technique was used to quantify HIV-1 RNA as an indicator of infectious viral load in semen and blood plasma of homosexual men with different stages and durations of HIV-1 infection. The median viral load in a cross section of 34 men was 11,000 HIV-1 RNA copies/ml (range, <400 to 1.3 x 10(7) copies/ml) in whole semen and 5,238 HIV-1 RNA copies/ml (range, <400 to 2.8 x 10(5) copies/ml) in seminal plasma, which is 10- to 1,000-fold higher than previous estimates. Viral loads in whole semen and seminal plasma were strongly correlated with blood plasma viral load (P < 0.001) but not with blood CD4+ T-cell count (P = 0.420). Longitudinal analysis of eight subjects who progressed to AIDS showed that seminal viral load increased in most cases, with viral load consistently higher in blood plasma than in semen. Viral loads in semen and blood plasma decreased markedly in six other patients following initiation of potent combination therapy with a protease inhibitor (indinavir) and a nonnucleoside reverse transcriptase inhibitor (DMP-266). These findings have important implications for the biology of sexual transmission of HIV-1 and its potential reduction by antiretroviral therapy.

Biological correlates of HIV-1 heterosexual transmission

OBJECTIVES

To study the role of HIV-1 biological phenotype, viral load and neutralizing antibodies in male-to-female heterosexual transmission of HIV-1.

METHODS

Seven transmitting and seven non-transmitting HIV-1-seropositive heterosexual male index cases were included in the present study. All couples had engaged in unprotected sex for a period of over 1 year. Transmission was defined by the seroconversion of the female sexual partner. Virus isolates were tested in MT-2 cells for replication and syncytia induction. HIV-1 RNA plasma load was measured by the branched DNA technique. Serum neutralizing activity to primary HIV-1 isolates was tested by using peripheral blood mononuclear cells (PBMC) as target cells.

RESULTS

Non-transmitting index cases had a lower HIV-1 RNA concentration in plasma than transmitting index cases. Non-transmitting index cases also tended to have serum neutralizing activity with broad specificity and to have viruses with low replicative capacity, as characterized by 50% infectious dose titres in PBMC and by the lack of MT-2 tropism.

CONCLUSIONS

The results indicate that plasma viral-RNA load is a marker for transmission. Moreover, an interplay between the host immune response and viral replication may modulate the level of viral load and thereby influence HIV-1 transmission.