High concentrations of interleukin 15 in breast milk are associated with protection against postnatal HIV transmission

Impact of IgG Isotype on the Induction of Antibody-Dependent Cellular Phagocytosis of HIV by Human Milk Leukocytes

Approximately 100,000 mother-to-child transmission (MTCT) events of HIV via human milk feeding occur each year. However, only about 15% of infants milk-fed by untreated HIV+ mothers become infected, suggesting a protective effect of the milk itself. Infants ingest 105-108 maternal leukocytes daily via milk, which remain functional beyond ingestion. Such function may be elicited by maternal milk antibody (Ab). Though IgA is dominant in milk, most HIV-specific milk Abs are of the IgG subclass, highlighting the importance of investigating the function of each IgG isotype in the milk context. Though Ab effector function mediated by the constant (Fc) domain via interaction with Fc Receptors (FcRs), such as Ab-dependent cellular phagocytosis (ADCP), are critical in protecting against HIV infection, ADCP is largely unexplored as it relates to mitigation of MTCT. Presently we report the ADCP activity of milk leukocytes against HIV particles and immune complexes (ICs), using 57 unique samples from 34 women, elicited by IgG1/2/3/4 of monoclonal (m)Ab 246-D. Granulocyte ADCP of HIV was most potent compared to other phagocytes when elicited by IgG1/3/4. IgG1/3 activated granulocytes similarly, exhibiting 1.6x-4.4x greater activity compared to IgG2/4, and a preference for virus compared to ICs. Notably, CD16- monocyte ADCP of a given target were unaffected by isotype, and CD16+ monocytes were poorly stimulated by IgG1. IgG2/4 elicited potent IC ADCP, and in terms of total leukocyte IC ADCP, IgG4 and IgG3 exhibited similar function, with IgG4 eliciting 1.6x-2.1x greater activity compared to IgG1/IgG2, and CD16+ monocytes most stimulated by IgG2. These data contribute to a more comprehensive understanding of Fc-mediated functionality of milk leukocytes, which is critical in order to develop therapeutic approaches to eliminating this route of MTCT, including mucosal administration of mAbs and/or a maternal vaccination aimed to elicit a potent milk Ab response.

Immediate Pre-Partum SARS-CoV-2 Status and Immune Profiling of Breastmilk: A Case-Control Study

Objetive

To address the prevalence of SARS-CoV-2 and the evolutionary profile of immune compounds in breastmilk of positive mothers according to time and disease state.

Methods

Forty-five women with term pregnancies with confirmed non-severe SARS-CoV-2 infection (case group), and 96 SARS-CoV-2 negative women in identical conditions (control group) were approached, using consecutive sample. Weekly (1st to 5th week postpartum) reverse transcription polymerase chain reaction (RT-PCR) in nasopharyngeal swabs (cases) and breastmilk (cases and controls) were obtained. Concentration of cytokines, chemokines, and growth factors in breastmilk (cases and controls) were determined at 1st and 5th week post-partum.

Results

Thirty-seven (study group) and 45 (control group) women were enrolled. Symptomatic infection occurred in 56.8% of women in the study group (48% fever, 48% anosmia, 43% cough). SARS-CoV-2 RNA was not found in breastmilk samples. Concentrations of cytokines (IFN-γ, IL-1ra, IL-4, IL-6, IL-9, IL-13, and TNF-α) chemokines (eotaxin, IP-10, MIP-1α, and RANTES) and growth factors (FGF, GM-CSF, IL7, and PDGF-BB) were higher in breastmilk of the study compared with the control group at 1st week postpartum. Immune compounds concentrations decreased on time, particularly in the control group milk samples. Time of nasopharyngeal swab to become negative influenced the immune compound concentration pattern. Severity of disease (symptomatic or asymptomatic infection) did not affect the immunological profile in breast milk.

Conclusions

This study confirms no viral RNA and a distinct immunological profile in breastmilk according to mother’s SARS-CoV-2 status. Additional studies should address whether these findings indicate efficient reaction against SARS-CoV-2 infection, which might be suitable to protect the recipient child.

Maternal Intervention to Prevent Mother-to-Child Transmission of HIV: Moving Beyond Antiretroviral Therapy

Widespread availability of antiretroviral therapy among pregnant women living with HIV has greatly reduced the rate of mother-to-child transmission (MTCT) of HIV across the globe. However, while Joint United Nations Programme on HIV/AIDS has set targets to reduce the annual number of new pediatric HIV infections to fewer than 40,000 in 2018 and fewer than 20,000 in 2020, progress towards these targets has plateaued at an unacceptably high global estimate of greater than 160,000 children newly infected with HIV in 2018. Moreover, it has become clear that expansion of maternal antiretroviral therapy alone will not be sufficient to close the remaining gap and eliminate MTCT of HIV. Additional strategies such as maternal or infant passive and/or active immunization that synergize with maternal antiretroviral therapy will be required to end the pediatric HIV epidemic. In this review, we outline the landscape of existing maternal interventions and emerging maternal immune-based approaches to prevent MTCT of HIV.

Investigational drugs with dual activity against HBV and HIV (Review)

Chronic hepatitis B (CHB) and acquired immunodeficiency syndrome (AIDS) are global public health problems that pose a significant health burden. Human immunodeficiency virus (HIV) and hepatitis B virus (HBV) coinfection is common, as these viruses have similar transmission routes, such as blood transmission, sexual transmission and mother-to-child transmission. Coinfection frequently leads to accelerated disease progression. For individuals coinfected with HIV/HBV, combination antiretroviral therapy containing dual anti-HBV drugs is recommended. Certain studies have also indicated the benefits of antiretroviral drugs with anti-HBV activity in patients with coinfection. A total of four Food and Drug Administration-approved HIV drugs also have anti-HBV activity; namely, emtricitabine, lamivudine, tenofovir disoproxil fumarate and tenofovir alafenamide, which are all nucleoside reverse transcriptase inhibitors. However, various issues, including drug resistance and side effects, limit their application. Therefore, it is necessary to develop more drugs with dual activity against HBV and HIV. The present review outlines the mechanisms, safety and efficacy of certain drugs that have been investigated for this purpose.

Sialic acid levels in breast milk from HIV-positive Tanzanian women and impact of maternal diet

OBJECTIVE

To quantify total sialic acid in milk from HIV-positive Tanzanian mothers and to determine the impact of maternal diet on milk sialic acid levels.

DESIGN

Milk samples were analyzed from 74 HIV-positive, Tanzanian women enrolled in a randomized, controlled clinical study of a dietary macronutrient supplement. Women were provided with a daily protein-calorie supplement and a micronutrient supplement or micronutrient supplement only during the last trimester of pregnancy and up to the first 6 months of breastfeeding.

METHODS

Milk samples were collected at approximately 2 weeks and at least 3 months postpartum and assayed for total sialic acid. Milk sialic acid was assessed relative to maternal macronutrient intake, age, BMI, CD4+ cell count and infant birth weight.

RESULTS

The mean concentration of milk sialic acid was highest in the first 2 weeks postpartum (6.89 ± 2.79 mmol/l) and declined rapidly by 3 months (2.49 ± 0.60 mmol/l). Sialic acid content in milk was similar between both treatment arms of the study, and did not correlate with maternal macronutrient intake. No correlation was found between maternal age, BMI, CD4+ cell count or infant birth weight and total milk sialic acid concentration.

CONCLUSION

Milk sialic acid levels in HIV-positive, Tanzanian women without malnutrition are comparable with reported values for women of European descent and show a similar temporal decline during early lactation. These findings suggest that total milk sialic acid is maintained despite macronutrient deficiencies in maternal diet and support a conserved role for milk sialic acid in neonatal development.

Polyclonal HIV envelope-specific breast milk antibodies limit founder SHIV acquisition and cell-associated virus loads in infant rhesus monkeys

Breast milk HIV-1 transmission is currently the predominant contributor to pediatric HIV infections. Yet, only ~10% of breastfeeding infants born to untreated HIV-infected mothers become infected. This study assessed the protective capacity of natural HIV envelope-specific antibodies isolated from the milk of HIV-infected women in an infant rhesus monkey (RM), tier 2 SHIV oral challenge model. To mimic placental and milk maternal antibody transfer, infant RMs were i.v. infused and orally treated at the time of challenge with a single weakly neutralizing milk monoclonal antibody (mAb), a tri-mAb cocktail with weakly neutralizing and ADCC functionalities, or an anti-influenza control mAb. Of these groups, the fewest tri-mAb-treated infants had SHIV detectable in plasma or tissues (2/6, 5/6, and 7/8 animals infected in tri-mAb, single-mAb, and control-mAb groups, respectively). Tri-mAb-treated infants demonstrated significantly fewer plasma transmitted/founder variants and reduced peripheral CD4+ T cell proviral loads at 8 weeks post-challenge compared to control mAb-treated infants. Abortive infection was observed as detectable CD4+ T cell provirus in non-viremic control mAb- and single mAb-, but not in tri-mAb-treated animals. These results suggest that polyfunctional milk antibodies contribute to the natural inefficiency of HIV-1 transmission through breastfeeding and infant vaccinations eliciting non-neutralizing antibody responses could reduce postnatal HIV transmission.

The immune response to sub-clinical mastitis is impaired in HIV-infected women

Background

Subclinical mastitis (SCM) is relatively common in lactating women and may be associated with HIV shedding in breast milk. The potential association between HIV infection and breast milk immunologic factors and immune response to SCM needs to be addressed.

Methods

In this cross-sectional study, SCM (Na/K ratio > 1) was tested in 165 mature breast milk samples collected from 40 HIV-infected women who didn’t transmit HIV to their child by breastfeeding and 43 HIV-uninfected women enrolled in an interventional cohort in South-Africa (Vertical Transmission Study). The level of 33 immune markers related to Th1/Th2 related response, inflammation and bacterial exposure were compared in ART-naive HIV-infected versus HIV-uninfected women. The associations between HIV infection and SCM on the concentration of immune factors were tested separately by Wilcoxon rank-sum test and corrected for false discovery rate. To control for potential confounder effects and take into account the clustering of breast milk samples from a single woman, multivariate mixed linear models adjusted on child age at the time of sampling were performed for each immune factor.

Results

Subclinical mastitis was detected in 15 (37.5%) HIV-infected women and 10 (23.3%) HIV-uninfected women. In the absence of SCM, the breast milk levels of IP-10 and MIG were higher and IL1-RA lower in HIV-infected women than in HIV-uninfected women (respectively p < 0.001, p = 0.001, p = 0.045). In HIV-uninfected women, SCM was characterized by a robust immune response with higher concentrations of a broad panel of Th1 and inflammatory related immune markers than in samples without SCM. By contrast, in HIV-infected women a limited number of immune markers were increased and lower increases were observed in samples with SCM than without SCM.

Conclusion

HIV infection in ART-naïve women was associated with elevated breast milk levels of IP-10 and MIG, which areTh1-related cytokines induced by IFN-γ. During SCM, a lower and narrower immune response was observed in HIV-infected than HIV-uninfected women, suggesting that HIV infection affects the capacity of the mammary gland to respond to SCM.

Electronic supplementary material

The online version of this article (10.1186/s12967-018-1667-4) contains supplementary material, which is available to authorized users.

Marginal Effects of Systemic CCR5 Blockade with Maraviroc on Oral Simian Immunodeficiency Virus Transmission to Infant Macaques

Current approaches do not eliminate all human immunodeficiency virus type 1 (HIV-1) maternal-to-infant transmissions (MTIT); new prevention paradigms might help avert new infections. We administered maraviroc (MVC) to rhesus macaques (RMs) to block CCR5-mediated entry, followed by repeated oral exposure of a CCR5-dependent clone of simian immunodeficiency virus (SIV) mac251 (SIVmac766). MVC significantly blocked the CCR5 coreceptor in peripheral blood mononuclear cells and tissue cells. All control animals and 60% of MVC-treated infant RMs became infected by the 6th challenge, with no significant difference between the number of exposures (P = 0.15). At the time of viral exposures, MVC plasma and tissue (including tonsil) concentrations were within the range seen in humans receiving MVC as a therapeutic. Both treated and control RMs were infected with only a single transmitted/founder variant, consistent with the dose of virus typical of HIV-1 infection. The uninfected RMs expressed the lowest levels of CCR5 on the CD4+ T cells. Ramp-up viremia was significantly delayed (P = 0.05) in the MVC-treated RMs, yet peak and postpeak viral loads were similar in treated and control RMs. In conclusion, in spite of apparent effective CCR5 blockade in infant RMs, MVC had a marginal impact on acquisition and only a minimal impact on the postinfection delay of viremia following oral SIV infection. Newly developed, more effective CCR5 blockers may have a more dramatic impact on oral SIV transmission than MVC.IMPORTANCE We have previously suggested that the very low levels of simian immunodeficiency virus (SIV) maternal-to-infant transmissions (MTIT) in African nonhuman primates that are natural hosts of SIVs are due to a low availability of target cells (CCR5+ CD4+ T cells) in the oral mucosa of the infants, rather than maternal and milk factors. To confirm this new MTIT paradigm, we performed a proof-of-concept study in which we therapeutically blocked CCR5 with maraviroc (MVC) and orally exposed MVC-treated and naive infant rhesus macaques to SIV. MVC had only a marginal effect on oral SIV transmission. However, the observation that the infant RMs that remained uninfected at the completion of the study, after 6 repeated viral challenges, had the lowest CCR5 expression on the CD4+ T cells prior to the MVC treatment appears to confirm our hypothesis, also suggesting that the partial effect of MVC is due to a limited efficacy of the drug. New, more effective CCR5 inhibitors may have a better effect in preventing SIV and HIV transmission.

Breastfeeding Behaviors and the Innate Immune System of Human Milk: Working Together to Protect Infants against Inflammation, HIV-1, and Other Infections

The majority of infants’ breastfeeding from their HIV-infected mothers do not acquire HIV-1 infection despite exposure to cell-free virus and cell-associated virus in HIV-infected breast milk. Paradoxically, exclusive breastfeeding regardless of the HIV status of the mother has led to a significant decrease in mother-to-child transmission (MTCT) compared with non-exclusive breastfeeding. Although it remains unclear how these HIV-exposed infants remain uninfected despite repeated and prolonged exposure to HIV-1, the low rate of transmission is suggestive of a multitude of protective, short-lived bioactive innate immune factors in breast milk. Indeed, recent studies of soluble factors in breast milk shed new light on mechanisms of neonatal HIV-1 protection. This review highlights the role and significance of innate immune factors in HIV-1 susceptibility and infection. Prevention of MTCT of HIV-1 is likely due to multiple factors, including innate immune factors such as lactoferrin and elafin among many others. In pursuing this field, our lab was the first to show that soluble toll-like receptor 2 (sTLR2) directly inhibits HIV infection, integration, and inflammation. More recently, we demonstrated that sTLR2 directly binds to selective HIV-1 proteins, including p17, gp41, and p24, leading to significantly reduced NFκB activation, interleukin-8 production, CCR5 expression, and HIV infection in a dose-dependent manner. Thus, a clearer understanding of soluble milk-derived innate factors with known antiviral functions may provide new therapeutic insights to reduce vertical HIV-1 transmission and will have important implications for protection against HIV-1 infection at other mucosal sites. Furthermore, innate bioactive factors identified in human milk may serve not only in protecting infants against infections and inflammation but also the elderly; thus, opening the door for novel innate immune therapeutics to protect newborns, infants, adults, and the elderly.

The Role of Immune Responses in HIV Mother-to-Child Transmission

HIV mother-to-child transmission (MTCT) represents a success story in the HIV/AIDS field given the significant reduction in number of transmission events with the scale-up of antiretroviral treatment and other prevention methods. Nevertheless, MTCT still occurs and better understanding of the basic biology and immunology of transmission will aid in future prevention and treatment efforts. MTCT is a unique setting given that the transmission pair is known and the infant receives passively transferred HIV-specific antibodies from the mother while in utero. Thus, infant exposure to HIV occurs in the face of HIV-specific antibodies, especially during delivery and breastfeeding. This review highlights the immune correlates of protection in HIV MTCT including humoral (neutralizing antibodies, antibody-dependent cellular cytotoxicity, and binding epitopes), cellular, and innate immune factors. We further discuss the future implications of this research as it pertains to opportunities for passive and active vaccination with the ultimate goal of eliminating HIV MTCT.

Mother-to-Child HIV-1 Transmission Events Are Differentially Impacted by Breast Milk and Its Components from HIV-1-Infected Women

Breast milk is a vehicle of infection and source of protection in post-natal mother-to-child HIV-1 transmission (MTCT). Understanding the mechanism by which breast milk limits vertical transmission will provide critical insight into the design of preventive and therapeutic approaches to interrupt HIV-1 mucosal transmission. However, characterization of the inhibitory activity of breast milk in human intestinal mucosa, the portal of entry in postnatal MTCT, has been constrained by the limited availability of primary mucosal target cells and tissues to recapitulate mucosal transmission ex vivo. Here, we characterized the impact of skimmed breast milk, breast milk antibodies (Igs) and non-Ig components from HIV-1-infected Ugandan women on the major events of HIV-1 mucosal transmission using primary human intestinal cells and tissues. HIV-1-specific IgG antibodies and non-Ig components in breast milk inhibited the uptake of Ugandan HIV-1 isolates by primary human intestinal epithelial cells, viral replication in and transport of HIV-1- bearing dendritic cells through the human intestinal mucosa. Breast milk HIV-1-specific IgG and IgA, as well as innate factors, blocked the uptake and transport of HIV-1 through intestinal mucosa. Thus, breast milk components have distinct and complementary effects in reducing HIV-1 uptake, transport through and replication in the intestinal mucosa and, therefore, likely contribute to preventing postnatal HIV-1 transmission. Our data suggests that a successful preventive or therapeutic approach would require multiple immune factors acting at multiple steps in the HIV-1 mucosal transmission process.

Factors affecting breast milk composition and potential consequences for development of the allergic phenotype

There is conflicting evidence on the protective role of breastfeeding in relation to allergic sensitization and disease. The factors in breast milk which influence these processes are still unclear and under investigation. We know that colostrum and breast milk contain a variety of molecules which can influence immune responses in the gut-associated lymphoid tissue of a neonate. This review summarizes the evidence that variations in colostrum and breast milk composition can influence allergic outcomes in the infant, and the evidence that maternal and environmental factors can modify milk composition. Taken together, the data presented support the possibility that maternal dietary interventions may be an effective way to promote infant health through modification of breast milk composition.

Breast Milk of HIV-Positive Mothers Has Potent and Species-Specific In Vivo HIV-Inhibitory Activity

Despite the nutritional and health benefits of breast milk, breast milk can serve as a vector for mother-to-child HIV transmission. Most HIV-infected infants acquire HIV through breastfeeding. Paradoxically, most infants breastfed by HIV-positive women do not become infected. This is potentially attributed to anti-HIV factors in breast milk. Breast milk of HIV-negative women can inhibit HIV infection. However, the HIV-inhibitory activity of breast milk from HIV-positive mothers has not been evaluated. In addition, while significant differences in breast milk composition between transmitting and nontransmitting HIV-positive mothers have been correlated with transmission risk, the HIV-inhibitory activity of their breast milk has not been compared. This knowledge may significantly impact the design of prevention approaches in resource-limited settings that do not deny infants of HIV-positive women the health benefits of breast milk. Here, we utilized bone marrow/liver/thymus humanized mice to evaluate the in vivo HIV-inhibitory activity of breast milk obtained from HIV-positive transmitting and nontransmitting mothers. We also assessed the species specificity and biochemical characteristics of milk's in vivo HIV-inhibitory activity and its ability to inhibit other modes of HIV infection. Our results demonstrate that breast milk of HIV-positive mothers has potent HIV-inhibitory activity and indicate that breast milk can prevent multiple routes of infection. Most importantly, this activity is unique to human milk. Our results also suggest multiple factors in breast milk may contribute to its HIV-inhibitory activity. Collectively, our results support current recommendations that HIV-positive mothers in resource-limited settings exclusively breastfeed in combination with antiretroviral therapy.

IMPORTANCE

Approximately 240,000 children become infected with HIV annually, the majority via breastfeeding. Despite daily exposure to virus in breast milk, most infants breastfed by HIV-positive women do not acquire HIV. The low risk of breastfeeding-associated HIV transmission is likely due to antiviral factors in breast milk. It is well documented that breast milk of HIV-negative women can inhibit HIV infection. Here, we demonstrate, for the first time, that breast milk of HIV-positive mothers (nontransmitters and transmitters) inhibits HIV transmission. We also demonstrate that breast milk can prevent multiple routes of HIV acquisition and that this activity is unique to human milk. Collectively, our results support current guidelines which recommend that HIV-positive women in resource-limited settings exclusively breastfeed in combination with infant or maternal antiretroviral therapy.

Longitudinal analysis of mature breastmilk and serum immune composition among mixed HIV-status mothers and their infants

BACKGROUND & AIMS

Understanding mature breastmilk immunology may benefit infants chronically exposed to infectious pathogens in resource-limited regions.

METHODS

This prospective rural/semi-rural Tanzanian cohort of women (n = 102 at delivery; 38% HIV-positive) and their infants (n = 102) investigated breastmilk, maternal and infant serum immunoglobulins (IgA/IgG1-4/IgM) and cytokines (IL-1β/IL-2/IL-6/IL-10/IL-12p70/IL-13/IL-15/TNF-α/IFN-γ) at 1, 2, 3, 6-months postpartum.

RESULTS

Milk immunoglobulins followed an inverse U-shaped pattern, while cytokine patterns were mixed. Exclusive breastfeeding duration and feeding intensity were associated with greater breastmilk total immunoglobulin and IgA, IgG1-3 and IL-12p70 concentrations. Maternal mastitis, fever or cough was associated with higher breastmilk total cytokine concentrations, while infant fever was associated with lower milk immunoglobulins or cytokines. Strong (r ≥ 0.40) to weak (r = 0.20-0.29) positive correlations between maternal serum-breastmilk or breastmilk-infant serum immunoglobulins were evident. Breastmilk cytokines were moderate to weakly negatively correlated with infant serum. Breastmilk immunology did not differ by maternal malnutrition or HIV-seropositivity.

CONCLUSIONS

Mature breastmilk is a dynamic source of many specific and non-specific immune factors associated with maternal and infant health and infant nutrition. Breastfeeding practices are associated with differential breastmilk immunological composition providing immunological support for universal recommendations to exclusively breastfeed for 6-months.

In Vivo Activation of Human NK Cells by Treatment with an Interleukin-15 Superagonist Potently Inhibits Acute In Vivo HIV-1 Infection in Humanized Mice

Natural killer (NK) cells with anti-HIV-1 activity may inhibit HIV-1 replication and dissemination during acute HIV-1 infection. We hypothesized that the capacity of NK cells to suppress acute in vivo HIV-1 infection would be augmented by activating them via treatment with an interleukin-15 (IL-15) superagonist, IL-15 bound to soluble IL-15Rα, an approach that potentiates human NK cell-mediated killing of tumor cells. In vitro stimulation of human NK cells with a recombinant IL-15 superagonist significantly induced their expression of the cytotoxic effector molecules granzyme B and perforin; their degranulation upon exposure to K562 cells, as indicated by cell surface expression of CD107a; and their capacity to lyse K562 cells and HIV-1-infected T cells. The impact of IL-15 superagonist-induced activation of human NK cells on acute in vivo HIV-1 infection was investigated by using hu-spl-PBMC-NSG mice, NOD-SCID-IL2rγ(-/-) (NSG) mice intrasplenically injected with human peripheral blood mononuclear cells (PBMCs) which develop productive in vivo infection after intrasplenic inoculation with HIV-1. IL-15 superagonist treatment potently inhibited acute HIV-1 infection in hu-spl-PBMC-NSG mice even when delayed until 3 days after intrasplenic HIV-1 inoculation. Removal of NK cells from human PBMCs prior to intrasplenic injection into NSG mice completely abrogated IL-15 superagonist-mediated suppression of in vivo HIV-1 infection. Thus, the in vivo activation of NK cells, integral mediators of the innate immune response, by treatment with an IL-15 superagonist increases their anti-HIV activity and enables them to potently suppress acute in vivo HIV-1 infection. These results indicate that in vivo activation of NK cells may represent a new immunotherapeutic approach to suppress acute HIV-1 infection.

IMPORTANCE

Epidemiological studies have indicated that NK cells contribute to the control of HIV-1 infection, and in vitro studies have demonstrated that NK cells can selectively kill HIV-1-infected cells. We demonstrated that in vivo activation of NK cells by treatment with an IL-15 superagonist that potently stimulates the antitumor activity of NK cells markedly inhibited acute HIV-1 infection in humanized mice, even when activation of NK cells by IL-15 superagonist treatment is delayed until 3 days after HIV-1 inoculation. NK cell depletion from PBMCs prior to their intrasplenic injection abrogated the suppression of in vivo HIV-1 infection observed in humanized mice treated with the IL-15 superagonist, demonstrating that activated human NK cells were mediating IL-15 superagonist-induced inhibition of acute HIV-1 infection. Thus, in vivo immunostimulation of NK cells, a promising therapeutic approach for cancer therapy, may represent a new treatment modality for HIV-1-infected individuals, particularly in the earliest stages of infection.

Does the national program of prevention of mother to child transmission of HIV (PMTCT) reach its target in Ouagadougou, Burkina Faso?

BACKGROUND

In the context of universal access to prevention, treatment, care and support, each country has to ensure that 80% of women and children in need have access to PMTCT interventions.

OBJECTIVE

To assess the PMTCT program achievement in Ouagadougou, the capital city of Burkina Faso.

METHODS

Between August and October 2008, a cross sectional study was carried out in the five health districts of the Centre Health Region. We reviewed weekly statistics from all health care centres (HCC) to compute the coverage of PMTCT program. In 38 HCC with functional PMTCT program, we extracted data of interest from HCC registers and made direct observations of PMTCT services.

RESULTS

The PMTCT program was implemented in 49% of HCC (target for the national program: 70%). Fifteen to 31% of these centers were often in shortage for PMTCT consumables. Patients' privacy was not observed in 67% of Voluntary Counselling & HIV Testing wards. Care providers were not qualified enough to deliver PMTCT services. Vitamin A supplementation was not implemented. None of the facilities offered the whole package of PMTCT program interventions. HCC providing HIV testing in labour or in postnatal ward were consistently lacking. Only 86% of antenatal care new attendants benefited from pre-test counselling; 2.4% of pretested women were HIV-positive and 39% of positive mothers received antiretroviral prophylaxis.

CONCLUSION

Coverage and quality of PMTCT programme in the Centre Health Region in Burkina Faso are still limited. Particular support is needed for training, supervision and infrastructures upgrading.

Soluble toll-like receptor 2 is significantly elevated in HIV-1 infected breast milk and inhibits HIV-1 induced cellular activation, inflammation and infection

OBJECTIVES

We previously demonstrated that immunodepletion of soluble Toll-like receptor 2 (sTLR2) from human breast milk significantly increased HIV infection in vitro. The aims of this study were to characterize sTLR2 levels in breast milk from HIV-infected and uninfected women, and identify a mechanism by which sTLR2 inhibits HIV-induced cellular activation and infection.

DESIGN

Blinded studies of breast milk from HIV-infected and uninfected Nigerian and Canadian women were evaluated for levels of sTLR2, proinflammatory cytokines and viral antigenemia. In-vitro experiments were conducted using cell lines to assess sTLR2 function in innate responses and effect on HIV infection.

RESULTS

Breast milk from HIV-infected women showed significantly higher levels of sTLR2 than uninfected breast milk. Further, sTLR2 levels correlated with HIV-1 p24 and interleukin (IL)-15, thus suggesting a local innate compensatory response in the HIV-infected breast. Given the significantly higher levels of sTLR2 in breast milk from HIV-infected women, we next demonstrated that mammary epithelial cells and macrophages, which are prevalent in milk, produced significantly increased levels of sTLR2 following exposure to HIV-1 proteins p17, p24 and gp41 or the TLR2 ligand, Pam3CSK4. Our results also demonstrated that sTLR2 physically interacts with p17, p24 and gp41 and inhibits HIV-induced nuclear factor kappa-light-chain-enhancer of activated B cells activation, and inflammation. Importantly, binding of sTLR2 to HIV-1 proteins inhibited a TLR2-dependent increase in chemokine receptor 5 expression, thus resulting in significantly reduced HIV-1 infection.

CONCLUSION

These results indicate novel mechanisms by which sTLR2 plays a critical role in inhibiting mother-to-child HIV transmission.

Target cell availability, rather than breast milk factors, dictates mother-to-infant transmission of SIV in sooty mangabeys and rhesus macaques

Mother-to-infant transmission (MTIT) of HIV is a serious global health concern, with over 300,000 children newly infected in 2011. SIV infection of rhesus macaques (RMs) results in similar rates of MTIT to that of HIV in humans. In contrast, SIV infection of sooty mangabeys (SMs) rarely results in MTIT. The mechanisms underlying protection from MTIT in SMs are unknown. In this study we tested the hypotheses that breast milk factors and/or target cell availability dictate the rate of MTIT in RMs (transmitters) and SMs (non-transmitters). We measured viral loads (cell-free and cell-associated), levels of immune mediators, and the ability to inhibit SIV infection in vitro in milk obtained from lactating RMs and SMs. In addition, we assessed the levels of target cells (CD4+CCR5+ T cells) in gastrointestinal and lymphoid tissues, including those relevant to breastfeeding transmission, as well as peripheral blood from uninfected RM and SM infants. We found that frequently-transmitting RMs did not have higher levels of cell-free or cell-associated viral loads in milk compared to rarely-transmitting SMs. Milk from both RMs and SMs moderately inhibited in vitro SIV infection, and presence of the examined immune mediators in these two species did not readily explain the differential rates of transmission. Importantly, we found that the percentage of CD4+CCR5+ T cells was significantly lower in all tissues in infant SMs as compared to infant RMs despite robust levels of CD4+ T cell proliferation in both species. The difference between the frequently-transmitting RMs and rarely-transmitting SMs was most pronounced in CD4+ memory T cells in the spleen, jejunum, and colon as well as in central and effector memory CD4+ T cells in the peripheral blood. We propose that limited availability of SIV target cells in infant SMs represents a key evolutionary adaptation to reduce the risk of MTIT in SIV-infected SMs.

Currently 2.5 million children are infected with HIV, largely as a result of mother-to-child transmission, and there is no effective vaccine or cure. Studies of Simian Immunodeficiency Virus (SIV) infection of nonhuman primate species termed “natural hosts” have shown that mother-to-infant transmission of SIV in these animals is rare. Natural hosts are African monkey species that are naturally infected with SIV in the wild but do not develop AIDS. We sought to understand the mechanism by which natural hosts are protected from mother-to-infant transmission of SIV, aiming to translate our findings into novel strategies to prevent perinatal HIV infection. We found that natural host sooty mangabey infants have extremely low levels of target cells for SIV infection in lymphoid and gastrointestinal tissues. Direct comparison of infant sooty mangabeys and infant rhesus macaques (non-natural host species with high SIV transmission rates) confirmed that natural hosts have significantly lower levels of SIV target cells compared with non-natural hosts. Analysis of the breast milk of sooty mangabeys and rhesus macaques revealed similar levels of virus and ability to inhibit SIV infection. Our study provides evidence for target cell restriction as the main mechanism of protection from mother-to-infant SIV transmission in natural hosts.

The oral mucosa immune environment and oral transmission of HIV/SIV

The global spread of human immunodeficiency virus (HIV) is dependent on the ability of this virus to efficiently cross from one host to the next by traversing a mucosal membrane. Unraveling how mucosal exposure of HIV results in systemic infection is critical for the development of effective therapeutic strategies. This review focuses on understanding the immune events associated with the oral route of transmission (via breastfeeding or sexual oral intercourse), which occurs across the oral and/or gastrointestinal mucosa. Studies in both humans and simian immunodeficiency virus (SIV) monkey models have identified viral changes and immune events associated with oral HIV/SIV exposure. This review covers our current knowledge of HIV oral transmission in both infants and adults, the use of SIV models in understanding early immune events, oral immune factors that modulate HIV/SIV susceptibility (including mucosal inflammation), and interventions that may impact oral HIV transmission rates. Understanding the factors that influence oral HIV transmission will provide the foundation for developing immune therapeutic and vaccine strategies that can protect both infants and adults from oral HIV transmission.

Immunology of pediatric HIV infection

Most infants born to human immunodeficiency virus (HIV)-infected women escape HIV infection. Infants evade infection despite an immature immune system and, in the case of breastfeeding, prolonged repetitive exposure. If infants become infected, the course of their infection and response to treatment differs dramatically depending upon the timing (in utero, intrapartum, or during breastfeeding) and potentially the route of their infection. Perinatally acquired HIV infection occurs during a critical window of immune development. HIV's perturbation of this dynamic process may account for the striking age-dependent differences in HIV disease progression. HIV infection also profoundly disrupts the maternal immune system upon which infants rely for protection and immune instruction. Therefore, it is not surprising that infants who escape HIV infection still suffer adverse effects. In this review, we highlight the unique aspects of pediatric HIV transmission and pathogenesis with a focus on mechanisms by which HIV infection during immune ontogeny may allow discovery of key elements for protection and control from HIV.

Mucosal correlates of protection in HIV-1-exposed sero-negative persons

Resistance to HIV-1 infection in HIV-1-exposed sero-negative (HESN) persons offers a promising opportunity to identify mechanisms of 'natural' protection. Unique features of the mucosa in particular may contribute to this protection. Here, we highlight several key issues pertaining to the mucosal correlates of protection in HESN persons, including humoral immune responses, mechanisms of mucosal HIV-1 neutralization, immune cell activation, and role of the microbiota in mucosal responses. We also discuss mucosal model systems that can be used to investigate the mechanisms of resistance in HESN subjects. A clear understanding of the mucosal correlates of protection against HIV-1 in HESN persons will provide critical new insights for the development of effective vaccine and microbicide strategies for the prevention of HIV-1 transmission.

Lack of B cell dysfunction is associated with functional, gp120-dominant antibody responses in breast milk of simian immunodeficiency virus-infected African green monkeys

The design of an effective vaccine to reduce the incidence of mother-to-child transmission (MTCT) of human immunodeficiency virus (HIV) via breastfeeding will require identification of protective immune responses that block postnatal virus acquisition. Natural hosts of simian immunodeficiency virus (SIV) sustain nonpathogenic infection and rarely transmit the virus to their infants despite high milk virus RNA loads. This is in contrast to HIV-infected women and SIV-infected rhesus macaques (RhMs), nonnatural hosts which exhibit higher rates of postnatal virus transmission. In this study, we compared the systemic and mucosal B cell responses of lactating, SIV-infected African green monkeys (AGMs), a natural host species, to that of SIV-infected RhMs and HIV-infected women. AGMs did not demonstrate hypergammaglobulinemia or accumulate circulating memory B cells during chronic SIV infection. Moreover, the milk of SIV-infected AGMs contained higher proportions of naive B cells than RhMs. Interestingly, AGMs exhibited robust milk and plasma Env binding antibody responses that were one to two logs higher than those in RhMs and humans and demonstrated autologous neutralizing responses in milk at 1 year postinfection. Furthermore, the plasma and milk Env gp120-binding antibody responses were equivalent to or predominant over Env gp140-binding antibody responses in AGMs, in contrast to that in RhMs and humans. The strong gp120-specific, functional antibody responses in the milk of SIV-infected AGMs may contribute to the rarity of postnatal transmission observed in natural SIV hosts.

Presence of IL-9 in paired samples of human colostrum and transitional milk

BACKGROUND

Human colostrum and breast milk are known to contain high levels of cytokines, cytokine receptors, and chemokines.

OBJECTIVE

To investigate the presence and compare levels of soluble cytokines in paired samples of human colostrum and milk.

METHODS

Levels of 27 cytokines were measured in 9 paired samples of human colostrum (day 2 after delivery) and breast milk (day 4 or 5 after delivery) by using multiplex technology.

RESULTS

The majority of cytokines and chemokines investigated have been previously described in colostrum and/or breast milk. For the first time, we describe the presence of IL-9 in both human colostrum and milk. Of the 27 cytokines investigated, only IL-5 was absent in both colostrum and milk, whereas IL-1β, IL-2, IL-4, IL-15, IL-17, and MIP-1α were present in colostrum, but not in breast milk. In general, colostrum contained higher concentrations of cytokines with respect to human milk.

CONCLUSION

Our data confirm and expand previous studies showing that human colostrum and breast milk are rich in cytokines and chemokines, including IL-9, which might contribute to the development of the immune system of the newborn.

Human milk oligosaccharide concentration and risk of postnatal transmission of HIV through breastfeeding

BACKGROUND

The inefficiency of HIV breast-milk transmission may be caused by the presence of immunologically active factors, including human milk oligosaccharides (HMOs).

OBJECTIVE

We investigated whether HMO concentrations are associated with a reduced risk of postnatal HIV transmission.

DESIGN

A nested case-control study was conducted within a larger cohort study of HIV-infected women and their infants followed from birth to 24 mo in Lusaka, Zambia. Breast-milk samples collected at 1 mo from 81 HIV-infected women who transmitted via breastfeeding, a random sample of 86 HIV-infected women who did not transmit despite breastfeeding, and 36 uninfected breastfeeding women were selected. Total and specific HMO concentrations were measured by HPLC and compared between groups with adjustment for confounders by using logistic regression.

RESULTS

HIV-infected women with total HMOs above the median (1.87 g/L) were less likely to transmit via breastfeeding (OR: 0.45; 95% CI: 0.21, 0.97; P = 0.04) after adjustment for CD4 count and breast-milk HIV RNA concentrations; a trend toward higher concentrations of lacto-N-neotetraose being associated with reduced transmission (OR: 0.49; 95% CI: 0.23, 1.04; P = 0.06) was also observed. The proportion of 3'-sialyllactose (3'-SL) per total HMOs was higher among transmitting than among nontransmitting women (P = 0.003) and correlated with higher plasma and breast-milk HIV RNA and lower CD4 counts. Neither Secretor nor Lewis status distinguished between transmitting and nontransmitting women.

CONCLUSIONS

Higher concentrations of non-3'-SL HMOs were associated with protection against postnatal HIV transmission independent of other known risk factors. Further study of these novel, potentially anti-HIV components of breast milk is warranted.

Influence of cytokines on HIV-specific antibody-dependent cellular cytotoxicity activation profile of natural killer cells

There is growing interest in HIV-specific antibody-dependent cellular cytotoxicity (ADCC) as an effective immune response to prevent or control HIV infection. ADCC relies on innate immune effector cells, particularly NK cells, to mediate control of virus-infected cells. The activation of NK cells (i.e., expression of cytokines and/or degranulation) by ADCC antibodies in serum is likely subject to the influence of other factors that are also present. We observed that the HIV-specific ADCC antibodies, within serum samples from a panel of HIV-infected individuals induced divergent activation profiles of NK cells from the same donor. Some serum samples primarily induced NK cell cytokine expression (i.e., IFNγ), some primarily initiated NK cell expression of a degranulation marker (CD107a) and others initiated a similar magnitude of responses across both effector functions. We therefore evaluated a number of HIV-relevant soluble factors for their influence on the activation of NK cells by HIV-specific ADCC antibodies. Key findings were that the cytokines IL-15 and IL-10 consistently enhanced the ability of NK cells to respond to HIV-specific ADCC antibodies. Furthermore, IL-15 was demonstrated to potently activate “educated” KIR3DL1⁺ NK cells from individuals carrying its HLA-Bw4 ligand. The cytokine was also demonstrated to activate “uneducated” KIR3DL1⁺ NK cells from HLA-Bw6 homozygotes, but to a lesser extent. Our results show that cytokines influence the ability of NK cells to respond to ADCC antibodies in vitro. Manipulating the immunological environment to enhance the potency of NK cell-mediated HIV-specific ADCC effector functions could be a promising immunotherapy or vaccine strategy.

The role of interleukin-15 in inflammation and immune responses to infection: implications for its therapeutic use

Interleukin-15 (IL-15) is a pleiotropic cytokine with a broad range of biological functions in many diverse cell types. It plays a major role in the development of inflammatory and protective immune responses to microbial invaders and parasites by modulating immune cells of both the innate and adaptive immune systems. This review provides an overview of the mechanisms by which IL-15 modulates the host response to infectious agents and its utility as a cytokine adjuvant in vaccines against infectious pathogens.

The magnitude and kinetics of the mucosal HIV-specific CD8+ T lymphocyte response and virus RNA load in breast milk

BACKGROUND

The risk of postnatal HIV transmission is associated with the magnitude of the milk virus load. While HIV-specific cellular immune responses control systemic virus load and are detectable in milk, the contribution of these responses to the control of virus load in milk is unknown.

METHODS

We assessed the magnitude of the immunodominant GagRY11 and subdominant EnvKY9-specific CD8+ T lymphocyte response in blood and milk of 10 A*3002+, HIV-infected Malawian women throughout the period of lactation and correlated this response to milk virus RNA load and markers of breast inflammation.

RESULTS

The magnitude and kinetics of the HIV-specific CD8+ T lymphocyte responses were discordant in blood and milk of the right and left breast, indicating independent regulation of these responses in each breast. However, there was no correlation between the magnitude of the HIV-specific CD8+ T lymphocyte response and the milk virus RNA load. Further, there was no correlation between the magnitude of this response and markers of breast inflammation.

CONCLUSIONS

The magnitude of the HIV-specific CD8+ T lymphocyte response in milk does not appear to be solely determined by the milk virus RNA load and is likely only one of the factors contributing to maintenance of low virus load in milk.

High cell-free virus load and robust autologous humoral immune responses in breast milk of simian immunodeficiency virus-infected african green monkeys

The design of immunologic interventions to prevent postnatal transmission of human immunodeficiency virus (HIV) will require identification of protective immune responses in this setting. Simian immunodeficiency virus (SIV)-infected rhesus monkeys (RMs), a species that develops an AIDS-like illness following experimental infection, transmit the virus at a high rate during breastfeeding. In contrast, postnatal transmission of SIV occurs rarely or not at all in natural, asymptomatic primate hosts of SIV. These contrasting transmission patterns provide a unique opportunity to study mechanisms that evolved to protect suckling infants from SIV infection. We compared the virologic and immunologic properties of milk of SIV-infected and uninfected natural hosts of SIV, African green monkeys (AGMs), to that of RMs. Interestingly, despite a low number of milk CD4(+) T lymphocytes in uninfected AGMs, milk virus RNA load in SIV-infected AGMs was comparable to that of SIV-infected RMs and that in AGM plasma. This observation is in contrast to the relatively low virus load in milk compared to that in plasma of SIV-infected RMs and HIV-infected women. Milk of SIV-infected AGMs also displayed robust virus-specific cellular immune responses. Importantly, an autologous challenge virus-specific neutralization response was detected in milk of five of six SIV-infected AGMs that was comparable in magnitude to that in plasma. In contrast, autologous challenge virus neutralization was not detectable in milk of SIV-infected RMs. The autologous virus-specific adaptive immune responses in breast milk of AGMs may contribute to impedance of virus transmission in the infant oral/gastrointestinal tract and the rarity of postnatal virus transmission in natural hosts of SIV.

IL-15 ex vivo overcomes CD4+ T cell deficiency for the induction of human antigen-specific CD8+ T cell responses

CD4(+) Th cells are important for the induction and maintenance of antigen-specific CD8(+) T cell function, so their loss or dysfunction in HIV-infected or cancer patients could reduce the patients' ability to control viral infection. Previous work in murine systems indicated that IL-15 codelivered with vaccines could overcome CD4(+) Th cell deficiency for induction of functionally efficient CD8(+) T cells and maintenance of viral-specific CTLs, but its efficacy in helping primary human CD8(+) T cell responses is unknown. In the present study, a peptide-pulsed, DC-based human coculture ex vivo system was used to study the role of IL-15 in overcoming CD4(+) Th deficiency to elicit CD8(+) T cell responses in CD4-depleted PBMCs from healthy individuals and PBMCs from HIV-1-infected patients. We found that IL-15 could overcome CD4(+) Th deficiency to induce primary and recall memory CD8(+) T cell responses in healthy individuals. Moreover, in CD4-deficient, HIV-1-infected patients with diminished CD8(+) T cell responses, IL-15 greatly enhanced CD8(+) T cell responses to alloantigen. These results suggest that IL-15 may be useful in the development of therapeutic and preventive vaccines against cancers and viral infections in patients defective in CD4(+) Th cell.

Primary human mammary epithelial cells endocytose HIV-1 and facilitate viral infection of CD4+ T lymphocytes

The contribution of mammary epithelial cells (MEC) to human immunodeficiency virus type 1 (HIV-1) in breast milk remains largely unknown. While breast milk contains CD4(+) cells throughout the breast-feeding period, it is not known whether MEC directly support HIV-1 infection or facilitate infection of CD4(+) cells in the breast compartment. This study evaluated primary human MEC for direct infection with HIV-1 and for indirect transfer of infection to CD4(+) target cells. Primary human MEC were isolated and assessed for expression of HIV-1 receptors. MEC were exposed to CCR5-, CXCR4- and dual-tropic strains of HIV-1 and evaluated for viral reverse transcription and integration and productive viral infection. MEC were also tested for the ability to transfer HIV to CD4(+) target cells and to activate resting CD4(+) T cells. Our results demonstrate that MEC express HIV-1 receptor proteins CD4, CCR5, CXCR4, and galactosyl ceramide (GalCer). While no evidence for direct infection of MEC was found, HIV-1 virions were observed in MEC endosomal compartments. Coculture of HIV-exposed MEC resulted in productive infection of activated CD4(+) T cells. In addition, MEC secretions increased HIV-1 replication and proliferation of infected target cells. Overall, our results indicate that MEC are capable of endosomal uptake of HIV-1 and can facilitate virus infection and replication in CD4(+) target cells. These findings suggest that MEC may serve as a viral reservoir for HIV-1 and may enhance infection of CD4(+) T lymphocytes in vivo.

Feeding of infants of HIV-positive mothers

PURPOSE OF REVIEW

To highlight recent research that has contributed to an improved understanding of, or resulted in, important changes in the approach to feeding HIV-exposed infants.

RECENT FINDINGS

The administration of antiretroviral therapy to a HIV-positive pregnant woman and its continued use during breast-feeding significantly reduce postnatal HIV transmission to her child. Similarly, extended antiretroviral prophylaxis to the breast-feeding infant dramatically decreases HIV transmission and promotes HIV-free child survival. Predominant breast-feeding may be as effective as exclusive breast-feeding in reducing HIV transmission risk. The protective role of immune modulators such as interferon-gamma and interleukin-15 in preventing breast milk transmission is being better appreciated. Although infant-feeding counseling is critical to the success of infant survival strategies, it is generally done poorly with few examples of successful consequences other than in research settings.

SUMMARY

Breast-feeding of HIV-exposed infants can be made considerably safer in resource-constrained settings through the provision of maternal highly active antiretroviral therapy (HAART), maternal short-course antiretrovirals, and extended infant antiretroviral prophylaxis.