Mother-to-child transmission of HIV-1: the 'all mucosal' hypothesis as a predominant mechanism of transmission

KIR2DS4 allelic variants: Differential effects on in utero and intrapartum HIV-1 mother-to-child transmission

KIR2DS4 is the only activating gene within the A haplotype, and alleles of KIR2DS4 can encode either functional (KIR2DS4-f) or non-functional (KIR2DS4-v) variants. To establish the role of KIR2DS4 in the context of HIV-1 mother-to-child transmission, we KIR genotyped 145 HIV-1 non-transmitting mothers (NT) and their exposed uninfected infants (EU), and 72 HIV-1 transmitting mothers (TR) and their infected infants [intrapartum (IP), in utero (IU) or IU2 (an IU-enriched infected group)]. The frequency of KIR2DS4-v was significantly higher in IU2 infants compared to EU infants (P=0.022, OR=2.88); this association was more significant amongst AA haplotypes (P=0.004, OR=18.4). Possession of KIR2DS4-f in the mother with absence in the infant (M+I- discordance) was associated with a higher risk of IP transmission (P=0.005, OR=3.84); whilst in M-I+ discordance, infant possession of KIR2DS4-v was associated with increased risk of IU acquisition (P=0.002; OR=6.40). This study highlights the importance of KIR2DS4 in HIV-1 transmission/acquisition.

Evaluation of the ultrastructure of the small intestine of hiv infected children by transmission and scanning electronic microscopy

OBJECTIVES

To describe HIV children's small intestinal ultrastructural findings.

METHODS

Descriptive, observational study of small intestine biopsies performed between August 1994 and May 1995 at São Paulo, SP, Brazil. This material pertained to 11 HIV infected children and was stored in a laboratory in paraffin blocks. Scanning and transmission electronic microscopy were used to view those intestine samples and ultrastructural findings were described by analyzing digitalized photos of this material. Ethical Committee approval was obtained.

RESULTS

In most samples scanning microscopy showed various degrees of shortening and decreasing number of microvilli and also completes effacements in some areas. Derangement of the enterocytes was seen frequently and sometimes cells well defined borders limits seemed to be loosened. In some areas a mucous-fibrin like membrane with variable thickness and extension appeared to partially or totally coat the epithelial surface. Fat drops were present in the intestinal lumen in various samples and a bacterium morphologically resembling bacilli was seen in two occasions. Scanning microscopy confirmed transmission microscopy microvilli findings and also showed little "tufts" of those structures. In addition, it showed an increased number of vacuoles and multivesicular bodies inside various enterocytes, an increased presence of intraepithelial lymphocytes, mitochondrial vacuolization and basement membrane enlargement in the majority of samples analyzed. However, some samples exhibited normal aspect.

CONCLUSIONS

Our study showed the common occurrence of various important intestinal ultrastructural alterations with variable degrees among HIV infected children, some of them in our knowledge not described before.

Adaptive HIV-specific B cell-derived humoral immune defenses of the intestinal mucosa in children exposed to HIV via breast-feeding

Background

We evaluated whether B cell-derived immune defenses of the gastro-intestinal tract are activated to produce HIV-specific antibodies in children continuously exposed to HIV via breast-feeding.

Methods

Couples of HIV-1-infected mothers (n = 14) and their breastfed non HIV-infected (n = 8) and HIV-infected (n = 6) babies, and healthy HIV-negative mothers and breastfed babies (n = 10) as controls, were prospectively included at the Complexe Pédiatrique of Bangui, Central African Republic. Immunoglobulins (IgA, IgG and IgM) and anti-gp160 antibodies from mother’s milk and stools of breastfed children were quantified by ELISA. Immunoaffinity purified anti-gp160 antibodies were characterized functionally regarding their capacity to reduce attachment and/or infection of R5- and X4- tropic HIV-1 strains on human colorectal epithelial HT29 cells line or monocyte-derived-macrophages (MDM).

Results

The levels of total IgA and IgG were increased in milk of HIV-infected mothers and stools of HIV-exposed children, indicating the activation of B cell-derived mucosal immunity. Breast milk samples as well as stool samples from HIV-negative and HIV-infected babies exposed to HIV by breast-feeding, contained high levels of HIV-specific antibodies, mainly IgG antibodies, less frequently IgA antibodies, and rarely IgM antibodies. Relative ratios of excretion by reference to lactoferrin calculated for HIV-specific IgA, IgG and IgM in stools of HIV-exposed children were largely superior to 1, indicating active production of HIV-specific antibodies by the intestinal mucosa. Antibodies to gp160 purified from pooled stools of HIV-exposed breastfed children inhibited the attachment of HIV-1NDK on HT29 cells by 63% and on MDM by 77%, and the attachment of HIV-1JRCSF on MDM by 40%; and the infection of MDM by HIV-1JRCSF by 93%.

Conclusions

The intestinal mucosa of children exposed to HIV by breast-feeding produces HIV-specific antibodies harbouring in vitro major functional properties against HIV. These observations lay the conceptual basis for the design of a prophylactic vaccine against HIV in exposed children.

Cell-free (RNA) and cell-associated (DNA) HIV-1 and postnatal transmission through breastfeeding

INTRODUCTION

Transmission through breastfeeding remains important for mother-to-child transmission (MTCT) in resource-limited settings. We quantify the relationship between cell-free (RNA) and cell-associated (DNA) shedding of HIV-1 virus in breastmilk and the risk of postnatal HIV-1 transmission in the first 6 months postpartum.

MATERIALS AND METHODS

Thirty-six HIV-positive mothers who transmitted HIV-1 by breastfeeding were matched to 36 non-transmitting HIV-1 infected mothers in a case-control study nested in a cohort of HIV-infected women. RNA and DNA were quantified in the same breastmilk sample taken at 6 weeks and 6 months. Cox regression analysis assessed the association between cell-free and cell-associated virus levels and risk of postnatal HIV-1 transmission.

RESULTS

There were higher median levels of cell-free than cell-associated HIV-1 virus (per ml) in breastmilk at 6 weeks and 6 months. Multivariably, adjusting for antenatal CD4 count and maternal plasma viral load, at 6 weeks, each 10-fold increase in cell-free or cell-associated levels (per ml) was significantly associated with HIV-1 transmission but stronger for cell-associated than cell-free levels [2.47 (95% CI 1.33-4.59) vs. aHR 1.52 (95% CI, 1.17-1.96), respectively]. At 6 months, cell-free and cell-associated levels (per ml) in breastmilk remained significantly associated with HIV-1 transmission but was stronger for cell-free than cell-associated levels [aHR 2.53 (95% CI 1.64-3.92) vs. 1.73 (95% CI 0.94-3.19), respectively].

CONCLUSIONS

The findings suggest that cell-associated virus level (per ml) is more important for early postpartum HIV-1 transmission (at 6 weeks) than cell-free virus. As cell-associated virus levels have been consistently detected in breastmilk despite antiretroviral therapy, this highlights a potential challenge for resource-limited settings to achieve the UNAIDS goal for 2015 of eliminating vertical transmission. More studies would further knowledge on mechanisms of HIV-1 transmission and help develop more effective drugs during lactation.

Maternal antiretroviral prophylaxis and breastfeeding

The prevention of mother-to-child transmission of HIV-1 during breastfeeding is a major concern in resource-poor settings where alternatives to breast milk may be unaffordable, unsafe and limited by social stigma. The use of triple-drug antiretroviral regimens initiated during pregnancy and continued throughout breastfeeding is being studied as a means to prevent transmission by reducing HIV-1 viral load in the maternal serum and breast milk. Studies characterizing the exposure of antiretroviral agents in breast milk and in the breastfed infant are important to understand the dynamics of HIV-1 replication in breast milk and to establish the safety profiles of antiretroviral drugs.

Genotypic and functional properties of early infant HIV-1 envelopes

BACKGROUND

Understanding the properties of HIV-1 variants that are transmitted from women to their infants is crucial to improving strategies to prevent transmission. In this study, 162 full-length envelope (env) clones were generated from plasma RNA obtained from 5 HIV-1 Clade B infected mother-infant pairs. Following extensive genotypic and phylogenetic analyses, 35 representative clones were selected for functional studies.

RESULTS

Infant quasispecies were highly homogeneous and generally represented minor maternal variants, consistent with transmission across a selective bottleneck. Infant clones did not differ from the maternal in env length, or glycosylation. All infant variants utilized the CCR5 co-receptor, but were not macrophage tropic. Relatively high levels (IC₅₀ ≥ 100 μg/ml) of autologous maternal plasma IgG were required to neutralize maternal and infant viruses; however, all infant viruses were neutralized by pooled sera from HIV-1 infected individuals, implying that they were not inherently neutralization-resistant. All infant viruses were sensitive to the HIV-1 entry inhibitors Enfuvirtide and soluble CD4; none were resistant to Maraviroc. Sensitivity to human monoclonal antibodies 4E10, 2F5, b12 and 2G12 varied.

CONCLUSIONS

This study provides extensive characterization of the genotypic and functional properties of HIV-1 env shortly after transmission. We present the first detailed comparisons of the macrophage tropism of infant and maternal env variants and their sensitivity to Maraviroc, the only CCR5 antagonist approved for therapeutic use. These findings may have implications for improving approaches to prevent mother-to-child HIV-1 transmission.

CD4+ T cells spontaneously producing human immunodeficiency virus type I in breast milk from women with or without antiretroviral drugs

Background

Transmission of human immunodeficiency virus type 1 (HIV-1) through breast-feeding may involve both cell-free and cell-associated virus. This latter viral reservoir remains, however, to be fully explored. CD4⁺ T cell-associated virus production in breast milk was therefore investigated.

Methods

The ex vivo spontaneous production of HIV-1 antigen and HIV-1 RNA by CD4⁺ T cells was measured in paired blood and breast milk samples from 15 HIV-1 infected women treated or not with antiretroviral drugs. Spontaneous antigen secreting cells (HIV-1-AgSCs) from breast milk and blood were enumerated by an ELISpot assay, and cell-associated HIV-1 RNA was quantified by real-time PCR in supernatants of CD4⁺ T cells cultured for 18 hours without addition of polyclonal activators.

Results

Among the CD4⁺ T cells present in breast milk, memory cells expressing high levels of cell-surface activation markers were predominant. Spontaneous HIV-1-AgSCs were detected and enumerated in the breast milk of all 15 women, with a median number of 13.0 and 9.5 HIV-1- AgSCs/106 CD4⁺ T cells in aviremic (n = 7) and viremic (n = 8) women, respectively. Cell- associated HIV-1 RNA was detected in cell-free supernatants from 4/7 aviremic and 5/8 viremic individuals at median levels of 190 and 245 copies/ml, respectively.

Conclusions

Activated CD4⁺ T cells producing HIV-1 are detected in the breast milk of untreated individuals as well as those receiving highly active antiretroviral therapy. This finding strongly suggests that HIV-1 replication occurs in latently infected CD4⁺ T cells that, upon spontaneous activation, revert to productively infected cells. These cells might be responsible for a residual breast milk transmission despite maternal highly active antiretroviral therapy.

Fetal immune activation to malaria antigens enhances susceptibility to in vitro HIV infection in cord blood mononuclear cells

Mother-to-child-transmission (MTCT) of human immunodeficiency virus (HIV) remains a significant cause of new HIV infections in many countries. To examine whether fetal immune activation as a consequence of prenatal exposure to parasitic antigens increases the risk of MTCT, cord blood mononuclear cells (CBMCs) from Kenyan and North American newborns were examined for relative susceptibility to HIV infection in vitro. Kenyan CBMCs were 3-fold more likely to be infected with HIV than were North American CBMCs (P=.03). Kenyan CBMCs with recall responses to malaria antigens demonstrated enhanced susceptibility to HIV when compared with Kenyan CBMCs lacking recall responses to malaria (P=.03). CD4(+) T cells from malaria-sensitized newborns expressed higher levels of CD25 and human leukocyte antigen DR ex vivo, which is consistent with increased immune activation. CD4(+) T cells were the primary reservoir of infection at day 4 after virus exposure. Thus, prenatal exposure and in utero priming to malaria may increase the risk of MTCT.

Twin pregnancy as a risk factor for mother-to-child transmission of HIV-1: trends over 20 years

OBJECTIVE

We investigated whether twin pregnancies were at increased risk of mother-to-child HIV-1 transmission (MTCT), in comparison with singletons.

METHODS

Among HIV-1 infected women enrolled in the French Perinatal HIV Cohort (n = 9262), we studied the association between twin deliveries and MTCT rate according to three time periods (pre-1994, 1994-1996, 1997-2004) and the effect of birth order. The mother was considered to have transmitted if at least one of the twins was infected. Univariate and multivariate analyses of risk factors for MTCT were performed for deliveries in the periods up to 1996.

RESULTS

Overall, 2.1% (192/9262) of all the deliveries were twins. The rate of prematurity was greater in twins than in singletons (54% and 13%, respectively). Up to 1996 the rate of MTCT of HIV-1 was 28.3% (15/53) in twin pregnancies, versus 13.5% (414/3077) in singletons [odds ratio (OR), 2.5; 95% confidence interval (CI), 1.4-4.7; P = 0.002; adjusted OR, 2.3: 95% CI, 1.1-2.3; P = 0.03). In the period from 1997 to 2003, MTCT was low and did not differ between twins (1.0%) and singletons (1.8%; P = 1.0). Overall, the transmission rate for the first-born child was threefold that for the second-born child (14/164, 8.5% versus 4/164, 2.4%; P = 0.008).

CONCLUSION

Twin pregnancies were at increased risk of transmission, but in the era of HAART this risk was reduced for twins, as well as singletons. Management of multiple pregnancies should take into account the risks of premature rupture of the membranes and preterm delivery.

Hiv-specific secretory IgA in breast milk of HIV-positive mothers is not associated with protection against HIV transmission among breast-fed infants

OBJECTIVES

To test whether secretory immunoglobulin A (sIgA) to human immunodeficiency virus (HIV) antigens in breast milk of HIV-positive women is associated with protection against HIV transmission among breast-fed infants.

STUDY DESIGN

Nested, case-control design in which HIV-specific sIgA was measured in breast milk collected from 90 HIV-positive women enrolled in a study in Lusaka, Zambia. Milk samples were selected to include 26 HIV-positive mothers with infected infants (transmitters) and 64 mothers with uninfected infants (nontransmitters).

RESULTS

HIV-specific sIgA was detected more often in breast milk of transmitting mothers (76.9%) than in breast milk of nontransmitting mothers (46.9%, P = .009). There were no significant associations between HIV-specific sIgA in breast milk and other maternal factors, including HIV RNA quantities in breast milk, CD4 count, and plasma RNA quantities.

CONCLUSIONS

HIV-specific sIgA in breast milk does not appear to be a protective factor against HIV transmission among breast-fed infants.

Maternal-fetal microtransfusions and HIV-1 mother-to-child transmission in Malawi

BACKGROUND

Between 25% and 35% of infants born to HIV-infected mothers become HIV-1 infected. One potential route of mother-to-child transmission (MTCT) could be through a breakdown in the placental barrier (i.e., maternal-fetal microtransfusions).

METHODS AND FINDINGS

Placental alkaline phosphatase (PLAP) is a 130-kD maternal enzyme that cannot cross the intact placental barrier. We measured PLAP activity in umbilical vein serum as an indicator of maternal-fetal microtransfusion, and related this to the risk of HIV-1 MTCT. A case-cohort study was conducted of 149 women randomly selected from a cohort of HIV-1-infected pregnant Malawians; these women served as a reference group for 36 cases of in utero MTCT and 43 cases of intrapartum (IP) MTCT. Cord PLAP activity was measured with an immunocatalytic assay. Infant HIV status was determined by real-time PCR. The association between cord PLAP activity and HIV-1 MTCT was measured with logistic regression using generalized estimating equations. Among vaginal deliveries, PLAP was associated with IP MTCT (risk ratio, 2.25 per log10 ng/ml PLAP; 95% confidence interval, 0.95-5.32) but not in utero MTCT. In a multivariable model adjusted for HIV-1 RNA load, chorioamnionitis, and self-reported fever, the risk of IP MTCT almost tripled for every log10 increase in cord PLAP activity (risk ratio, 2.87; 95% confidence interval, 1.05-7.83).

CONCLUSION

These results suggest that during vaginal deliveries, placental microtransfusions are a risk factor for IP HIV-1 MTCT. Future studies are needed to identify factors that increase the risk for microtransfusions in order to prevent IP HIV-1 MTCT.

Management of breech presentation in areas with high prevalence of HIV infection

OBJECTIVE

To provide recommendations for the management of breech presentation in areas of high prevalence of human immunodeficiency virus (HIV) infection.

METHOD

Review of relevant literature.

RESULTS

Studies show that elective cesarean section (CS) is safer than vaginal delivery for breech presentation, external cephalic version (ECV) at term increases the chance of vaginal cephalic delivery. Although there are no studies of the risk of mother-to-child transmission of HIV from ECV, indirect evidence suggests that any increased risk is likely to be very small.

RECOMMENDATIONS

Where CS is available and safe, HIV-positive women, or women who might be at risk of HIV, with a fetus at term with breech presentation, should be offered elective CS to reduce the risks of both vaginal breech delivery and mother-to-child HIV infection. HIV-negative women can be offered ECV at term to try to avoid CS. Where women do not have access to a safe CS, or prefer vaginal delivery, the benefit for both mother and child of attempting ECV at term is likely to outweigh the theoretical, very small, risk of facilitating HIV transmission.

Breastfeeding and HIV

Breastfeeding is a route of HIV transmission from an HIV-infected mother to her infant. However, breastfeeding is an important pillar of child survival and the ideal way of feeding an infant, as well as providing a unique biological and emotional basis for child development. This chapter will highlight the dilemma created by the risks and benefits of breastfeeding and will discuss factors which increase the risk of HIV transmission during breastfeeding, as well as strategies which could be employed to reduce these risks. The research agenda is very full as many questions still remain unanswered.

Breastfeeding and the HIV positive mother: the debate continues

Breastfeeding is a route of HIV transmission from an HIV-infected mother to her infant. However, breastfeeding is an important pillar of child survival and the ideal way of feeding an infant as well as providing a unique biological and emotional basis for child development. This article highlights the dilemma created by the risks and benefits of breastfeeding and will discuss factors which increase the risk of HIV transmission during breastfeeding as well as strategies which could be employed to reduce these risks. Many questions still remain unanswered. Until further research results are available, women should be encouraged to follow the UNAIDS guidelines "when replacement feeding is acceptable, feasible, affordable, sustainable and safe, avoidance of all breastfeeding by HIV-infected mothers is recommended, otherwise, exclusive breastfeeding (EBF) is recommended during the first months of life". Anti-retroviral therapy to the mother and/or infant is likely to offer the possibility of maintaining breastfeeding as a safe option for HIV-infected women.

Advances in the prevention of vertical transmission of human immunodeficiency virus

The major mode of acquisition of human immunodeficiency virus (HIV) for children is through mother-to-child transmission, which can occur during pregnancy or labor and delivery, or postnatally through breastfeeding. In resource-rich countries, mother-to-child HIV transmission has decreased to less than 2 percent after recommendations for universal prenatal HIV counseling and testing, antiretroviral prophylaxis and elective cesarean delivery, and avoidance of breastfeeding were implemented. In resource-limited settings, effective, shorter, and less expensive antiretroviral prophylaxis interventions also have been identified, but implementation has been slower, and continued transmission through breastfeeding remains a significant problem. This review summarizes recent advances made in prevention of mother-to-child transmission of HIV in the United States and other resource-rich countries, as well as progress in resource-limited countries.

Breast milk and HIV-1: vector of transmission or vehicle of protection?

Transmission of HIV-1 to the infant through breastfeeding is a major cause of new paediatric HIV-1 infections worldwide. Although extended breastfeeding accounts for approximately 40% of infant HIV infections worldwide, most breastfed infants remain uninfected, despite prolonged and repeated exposure to HIV-1. Mechanisms associated with transmission of HIV-1 through breastfeeding and factors related to protection from such transmission remain poorly understood. Here we focus on the cellular origin of HIV in breast milk and on immune factors within the milk that may offer protection from transmission of HIV infection. The presence of innate immunity and induction of adaptive immunity against HIV is explored: in particular, specific antibodies, cellular responses, and their significance. The role of mucosal immune activation and epithelial integrity in HIV transmission is also addressed. We are of the opinion that advances in laboratory methods that study specific aspects of immunity will help open new areas of understanding of HIV transmission through breastfeeding and mechanisms of protection, and contribute to the development of novel prevention strategies.

Breast-feeding and HIV-1 transmission in resource-limited settings

In many international settings, transmission of the HIV virus during lactation accounts for one third to one half of all HIV transmission from mothers to infants. Reduction of HIV transmission during lactation is one of the most pressing public health dilemmas confronting perinatal researchers, health policy makers, and HIV-infected women in many areas of the world. While results of clinical trials, laboratory and observational studies have increased our understanding of risk factors for breast-feeding transmission and the timing of postnatal transmission, there are no proven strategies known to reduce the risk of HIV transmission during breast-feeding for those HIV-infected women who opt to breast-feed in developing countries. Approaches to decreasing transmission of HIV through breast-feeding that will be studied include trials of combination antiretrovirals given to mothers during lactation. These research efforts using maternal antiretrovirals for perinatal HIV prevention during breast-feeding will interface with emerging plans for treatment programs in developing countries.

Stage of the epidemic and viral phenotype should influence recommendations regarding mother-to-child transmission of HIV-1

This article argues for a new approach to use of nevirapine in the prevention of vertical transmission of HIV-1. Existing antenatal surveillance should be strengthened to plan geographical allocation, and subsequent evaluation, of a "nevirapine plus" programme. As the epidemic evolves the programme should also and, ideally, care should be tailored to individual women. Underpinning this approach is evidence that a more virulent viral phenotype appears in many patients with advanced HIV-1 infection. This phenotype will become more common at the population level as the epidemic progresses. As efficacy of zidovudine correlates with viral phenotype, and use of the drug may alter phenotype, there is an urgent need for a replacement that is safe to use with nevirapine.

Subclinical mastitis as a risk factor for mother-infant HIV transmission

Subclinical mastitis, as diagnosed by an elevated sodium/potassium ratio in milk accompanied by an increased milk concentration of the inflammatory cytokine, interleukin-8 (IL8), was found to be common among breast feeding women in Bangladesh and Tanzania. Subclinical mastitis results in leakage of plasma constituents into milk, active recruitment of leukocytes into milk, and possible infant gut damage from inflammatory cytokines. Therefore, we wished to investigate whether subclinical mastitis was related to known risk factors for postnatal mother-to-child HIV transmission, that is, high milk viral load or increased infant gut permeability. HIV-infected South African women were recruited at the antenatal clinic of McCord's Hospital, Durban. Risks and benefits of different feeding strategies were explained to them and, if they chose to breast feed, they were encouraged to do so exclusively. Women and infants returned to the clinic at 1, 6 and 14 weeks postpartum for an interview about infant health and current feeding pattern, a lactulose/mannitol test of infant gut permeability, and milk sample collection from each breast separately for analysis of Na/K ratio, IL8 concentration and viral load in the cell-free aqueous phase. Only preliminary cross-sectional analyses from an incomplete database are available at this point. Moderately (0.6-1.0) or greatly (>1.0) raised Na/K ratio was common and was often unilateral, although as a group right and left breasts did not differ. Considering both breasts together, normal, moderately raised or greatly raised Na/K was found, respectively, in 51%, 28%, 21% of milk samples at 1 week (n=190); 69%, 20%, 11% at 6 weeks (n=167); and 72%, 16%, 12% at 14 weeks (n=122). IL8 concentration significantly correlated with both Na/K and viral load at all times. Na/K correlated with viral load at 1 and 14, but not 6 weeks. At 1 and 14 weeks, geometric mean viral loads in samples with Na/K > 1.0 were approximately 4 times those in samples with Na/K < 0.6. At 1 week but not later times, exclusive breast feeding was associated with lower milk viral load than was mixed feeding. Gut permeability was unrelated to milk Na/K ratio or IL8 concentration and was not significantly increased by inclusion of other foods than breast milk in the infant's diet. The results suggest that subclinical mastitis among HIV-infected women may increase the risk of vertical transmission through breast feeding by increasing milk viral load. The importance of various causes of subclinical mastitis, which likely differ at 1 week from at later times and may include local infection or sterile inflammation, systemic infection, micronutrient deficiencies, or poor lactation practices, needs to be further clarified so that appropriate interventions can be implemented.

HIV-1 in placentas of untreated HIV-1-infected women in relation to viral transmission, infectious HIV-1 and RNA load in plasma

The presence of HIV in the placenta was analysed in relation to virological and immunological factors and vertical transmission of HIV in 39 pregnancies between 1989 and 1993 among 37 HIV-1-infected women without zidovudine prophylaxis. HIV-1 was detected in 12 of 37 (31%) placentas by immunohistochemistry and in 3 of 18 by PCR. Altogether 14/39 (36%) placentas bore evidence of HIV-1 infection, although there was no relation with the outcome of HIV infection in the child. Neither was there a relation between placental infection and either CD4 cell counts or HIV-1 RNA levels. However, HIV-1 was isolated from plasma in 20 of 39 (50%) pregnancies, which was inversely related to the presence of HIV in the placenta. When HIV-1 was identified in the placenta, HIV-1 was isolated from plasma in 3/14 (21%) pregnancies, vs 17/25 (68%) when it was not (p = 0.01), with a relative risk of having a placenta positive for HIV of 3.9 in pregnancies with a negative plasma HIV isolation. This inverse relation may point to differences in tropism between HIV-1 in placenta and plasma. The results show that the placental barrier prevents HIV transmission, irrespective of whether HIV enters the placenta or not.

Vaginal lavage with chlorhexidine during labour to reduce mother-to-child HIV transmission: clinical trial in Mombasa, Kenya

OBJECTIVES

To evaluate the effect of vaginal lavage with diluted chlorhexidine on mother-to child transmission of HIV (MTCT) in a breastfeeding population.

METHODS

This prospective clinical trial was conducted in a governmental hospital in Mombasa, Kenya. On alternating weeks, women were allocated to non-intervention or to intervention consisting of vaginal lavage with 120 ml 0.2% chlorhexidine, later increased to 0.4%, repeated every 3 h from admission to delivery. Infants were tested for HIV by DNA polymerase chain reaction within 48 h and at 6 and 14 weeks of life.

RESULTS

Enrolment and follow-up data were available for 297 and 309 HIV-positive women, respectively, in the non-lavage and the lavage groups. There was no evidence of a difference in intrapartum MTCT (17.2 versus 15.9%, OR 0.9, 95% CI 0.6-1.4) between the groups. Lavage solely before rupture of the membranes tended towards lower MTCT with chlorhexidine 0.2% (OR 0.6, 95% CI 0.3-1.1), and even more with chlorhexidine 0.4% (OR 0.1, 95% CI 0.0-0.9).

CONCLUSION

The need remains for interventions reducing MTCT without HIV testing, often unavailable in countries with a high prevalence of HIV. Vaginal lavage with diluted chlorhexidine during delivery did not show a global effect on MTCT in our study. However, the data suggest that lavage before the membranes are ruptured might be associated with a reduction of MTCT, especially with higher concentrations of chlorhexidine.

Vertical human immunodeficiency virus type 1--HIV-1--transmission--a review

Several factors appear to affect vertical HIV-1 transmission, dependent mainly on characteristics of the mother (extent of immunodeficiency, co-infections, risk behaviour, nutritional status, immune response, genetical make-up), but also of the virus (phenotype, tropism) and, possibly, of the child (genetical make-up). This complex situation is compounded by the fact that the virus may have the whole gestation period, apart from variable periods between membrane rupture and birth and the breast-feeding period, to pass from the mother to the infant. It seems probable that an extensive interplay of all factors occurs, and that some factors may be more important during specific periods and other factors in other periods. Factors predominant in protection against in utero transmission may be less important for peri-natal transmission, and probably quite different from those that predominantly affect transmission by mothers milk. For instance, cytotoxic T lymphocytes will probably be unable to exert any effect during breast-feeding, while neutralizing antibodies will be unable to protect transmission by HIV transmitted through infected cells. Furthermore, some responses may be capable of controlling transmission of determined virus types, while being inadequate for controlling others. As occurrence of mixed infections and recombination of HIV-1 types is a known fact, it does not appear possible to prevent vertical HIV-1 transmission by reinforcing just one of the factors, and probably a general strategy including all known factors must be used. Recent reports have brought information on vertical HIV-1 transmission in a variety of research fields, which will have to be considered in conjunction as background for specific studies.

Breast milk transmission of HIV-1. Laboratory and clinical studies

Breast milk transmission of HIV-1 can occur at any time during the entire duration of breastfeeding. The risk of late postnatal transmission (after 2.5 months of age) is 3.2 per 100 child/years of breastfeeding, but early postnatal transmission may be more frequent than previously thought. Exclusive breastfeeding has been suggested to be less risky than mixed feeding. Breast milk contains immunoactive cells, antiinfectious substances, immune globulins, cytokines, and complement factors. HIV-1 has been found in breast milk from HIV-infected mothers as both cell-associated and cell-free particles. Mastitis has been suggested to facilitate transmission of HIV-1. The portal of entry of HIV-1 in the infant mucosae may involve tonsilar lymphoepithelium, M cells, and enterocytes from intestinal surfaces. Anti-HIV-1 SIgA and IgM in breast milk and intestinal fluid may confer some protection. Transmission of HIV-1 by breastfeeding has to be taken into account in designing interventions to reduce/prevent mother-to-child transmission in developing countries.

Exclusive breast-feeding: does it have the potential to reduce breast-feeding transmission of HIV-1?

Exclusive breast-feeding is unambiguously the optimal infant feeding practice and is universally promoted in the absence of human immunodeficiency virus (HIV-1). It is associated with reduced morbidity and mortality from diarrheal and respiratory diseases. Recent findings suggest that exclusive breast-feeding may pose less risk of HIV-1 transmission than the more common practice of mixed feeding (i.e., breast-feeding concurrent with the feeding of water, other fluids, and foods), which has important infant feeding policy implications for low-resource settings. This paper reviews the biologic mechanisms associated with exclusive breast-feeding that provide protection against gastrointestinal, respiratory, and atopic diseases, and evaluates the relevance of these mechanisms for HIV-1 transmission. Potential mechanisms include reduction in dietary antigens and enteric pathogens that may maintain integrity of the intestinal mucosal barrier and limit inflammatory responses of the gut mucosa; promotion of beneficial intestinal microflora that may increase resistance to infection and modulate the infant's immune response; alteration in specific antiviral or anti-inflammatory factors in human milk that may modulate maternal hormonal or immunologic status; and maintenance of mammary epithelial integrity that may reduce viral load in breast milk.

Exposure to HIV-1 during delivery and mother-to-child transmission

BACKGROUND

The correlation between the presence of HIV-1 in maternal cervicovaginal secretions and in the infant's oro-pharyngal secretions at birth, and mother-to-child HIV transmission (MTCT) were examined to obtain a better understanding of its mechanism.

METHODS

Women without medical and obstetrical complications, living within a reasonable distance of the government hospital in Mombasa, Kenya, were recruited after informed consent. Maternal and infant characteristics were collected. Polymerase chain reaction was used to detect HIV-1 in cervico-vaginal and oro-pharyngal secretions. Infants were tested for HIV-1 by polymerase chain reaction within 48 h and at 6 weeks after delivery.

RESULTS

Between April 1998 and April 1999, 228 woman-infant pairs were included in the study. HIV-1 DNA in cervico-vaginal secretions was independently associated with HIV-1 maternal viral load and with infant birth-weight, whereas HIV-1 RNA was associated with maternal viral load and maternal age. HIV-1 DNA in the oropharyngal secretions was also independently associated with maternal viral load. MTCT rate at the age of 6 weeks was 23.6%. Intrapartum and early postpartum HIV transmission was independently associated with maternal viral load [adjusted odds ratio (OR), 1.6; 95% confidence interval (CI),1.0-2.7], detection of HIV-1 RNA in cervico-vaginal secretions (adjusted OR, 3.2; 95% CI, 1.5-7.3) and of HIV-1 DNA in oro-pharyngeal secretions (adjusted OR, 3.2; 95% CI, 1.1-9.0).

DISCUSSION

As far as is known, this is the first study showing that infant exposure to HIV-1 in the birth canal and the presence of HIV-infected cells in the infant's oropharyngeal cavity are independently associated with intrapartum and early postpartum MTCT. It supports the hypothesis that MTCT could occur through the oral route.

Physiology, immunology, and disease transmission in human breast milk

Breast feeding is an important mode of mother-to-child transmission of HIV. Interventions to decrease the number of infants becoming infected are particularly required for women in less developed countries where breast feeding is essential for infant survival. This review discusses the physiology and immunology of breast feeding and how maternal health interventions in the postpartum period may help decrease mother-to-child HIV transmission.

Preventing mother-to-child transmission of HIV-1 in Africa in the year 2000

OBJECTIVES

Various approaches to preventing mother-to-child transmission (MTCT) of HIV have recently been, or are being, evaluated in developing countries, especially in Africa. New findings from these trials are now becoming available, the implications of which, for population-based intervention programmes, need urgent consideration.

METHOD

A critical review of 18 randomized trials and other relevant studies from developing and industrialized countries.

RESULTS

Most African results relate to trials of antiretroviral agents (ARV). They demonstrate efficacy in reducing transmission in the first 6 months of life with short regimens of zidovudine (ZDV), with or without lamivudine (3TC), and nevirapine (NVP) alone. Preliminary results suggest the long-term efficacy of zidovudine. Antiseptic and nutritional interventions have been shown to reduce maternal and infant mortality and morbidity but not MTCT of HIV. HIV confidential voluntary counselling and testing for pregnant women, a short regimen of peripartum ARV with alternatives to breastfeeding such as early weaning or breast milk substitutes from birth currently represent the best option to reduce MTCTof HIV in Africa. However, the prevention of postnatal transmission requires further research, particularly in view of the consequences of different feeding options and the possibility of post-perinatal exposure prophylaxis of newborns with ARV. Issues relating to the implementation of currently validated strategies are discussed.