Detection of a large T-cell reservoir able to replicate HIV-1 actively in breast milk

Viruses and Human Milk: Transmission or Protection?

Human milk (HM) is considered the best source of nutrition for infant growth and health. This nourishment is unique and changes constantly during lactation to adapt to the physiological needs of the developing infant. It is also recognized as a potential route of transmission of some viral pathogens although the presence of a virus in HM rarely leads to a disease in an infant. This intriguing paradox can be explained by considering the intrinsic antiviral properties of HM. In this comprehensive and schematically presented review, we have described what viruses have been detected in HM so far and what their potential transmission risk through breastfeeding is. We have provided a description of all the antiviral compounds of HM, along with an analysis of their demonstrated and hypothesized mechanisms of action. Finally, we have also analyzed the impact of HM pasteurization and storage methods on the detection and transmission of viruses, and on the antiviral compounds of HM. We have highlighted that there is currently a deep knowledge on the potential transmission of viral pathogens through breastfeeding and on the antiviral properties of HM. The current evidence suggests that, in most cases, it is unnecessarily to deprive an infant of this high-quality nourishment and that the continuation of breastfeeding is in the best interest of the infant and the mother.

Women living with HIV in high-income settings and breastfeeding

Guidelines in high-income settings recommend breastfeeding avoidance amongst women living with HIV (WLWH). Increasingly, WLWH in high-income settings, who are well-treated with fully suppressed viral loads, are choosing to breastfeed their infants, even with these recommendations. The purpose of this article is to review existing research and guidance on infant feeding amongst WLWH in high-income countries and to identify gaps in this evidence that require further investigation. Current evidence on the risk of HIV transmission through breastfeeding in the context of antiretroviral therapy (ART), the significance of cell-associated virus, transmission risk factors, retention in care and adherence postpartum, infant prophylaxis and antiretroviral exposure, and monitoring of the breastfeeding WLWH are summarized. A latent HIV reservoir is persistently present in breast milk, even in the context of ART. Thus, suppressive maternal ART significantly reduces, but does not eliminate, the risk of postnatal transmission of HIV. There are currently limited data to guide the optimal frequency of virologic monitoring and the clinical actions to take in case of maternal detectable viral load whilst breastfeeding. Moreover, retention in care and adherence to ART in the postpartum period may be difficult and more research is needed to understand what clinical and psychosocial support would benefit these mothers so that successful engagement in care can be achieved. The long-term effects of antiretroviral drug exposure in the infants also need further exploration. Thus, there is a need for collecting enhanced surveillance data on WLWH who breastfeed and their infants to augment clinical guidance in high-income settings.

Pediatric HIV-1 Acquisition and Lifelong Consequences of Infant Infection

Increased availability of antiretroviral therapy to pregnant and breastfeeding women in resource-limited areas has proven remarkably successful at reducing HIV vertical transmission rates over the past several decades. Yet, still more than 170,000 children are infected annually due to failures in therapy implementation, monitoring, and adherence. Mother-to-child transmission (MTCT) of HIV-1 can occur at one of several distinct stages of infant development - intrauterine, intrapartum, and postpartum. The heterogeneity of the maternal-fetal interface at each of these modes of transmission poses a challenge for the implementation of immune interventions to prevent all modes of HIV MTCT. However, using mother-infant human cohorts and nonhuman primate models of infant simian immunodeficiency virus (SIV) acquisition, investigators have made important observation about the biology of pediatric HIV infection and have identified unique protective immune factors for each mode of transmission. Knowledge of immune factors protective against HIV MTCT will be critical to the development of targeted immune therapies to prevent infant HIV acquisition and to bring an end to the pediatric AIDS epidemic.

Does U=U for breastfeeding mothers and infants? Breastfeeding by mothers on effective treatment for HIV infection in high-income settings

Can the campaign Undetectable=Untransmittable (U=U), established for the sexual transmission of HIV, be applied to the transmission of HIV through breastfeeding? European AIDS Clinical Society and, to some extent, American guidelines now state that mothers with HIV who wish to breastfeed should be supported, with increased clinical and virological monitoring. This Viewpoint summarises existing evidence on transmission of HIV through breastfeeding, differences in HIV dynamics and viral load between breastmilk and plasma, and the effects of antiretroviral therapy on infants. At present, insufficient evidence exists to make clear recommendations for the required frequency of clinical and virological monitoring for mother and infant in a breastfeeding relationship or for the action to be taken in the event of viral rebound. We propose a roadmap for collaborative research to provide the missing evidence required to enable mothers who wish to breastfeed to make a fully informed choice.

Breast milk cellular HIV-specific interferon γ responses are associated with protection from peripartum HIV transmission

OBJECTIVE

Breast milk is a major route of infant HIV infection, yet the majority of breast-fed, HIV-exposed infants escape infection by unknown mechanisms. This study aimed to investigate the role of HIV-specific breast milk cells in preventing infant HIV infection.

DESIGN

A prospective study was designed to measure associations between maternal breast milk HIV-specific interferon-γ (IFN-γ) responses and infant HIV-1 detection at 1 month of age.

METHODS

In a Kenyan cohort of HIV-infected mothers, blood and breast milk HIV-gag IFN-γ ELISpot responses were measured. Logistic regression was used to measure associations between breast milk IFN-γ responses and infant HIV infection at 1 month of age.

RESULTS

IFN-γ responses were detected in breast milk from 117 of 170 (69%) women. IFN-γ responses were associated with breast milk viral load, levels of macrophage inflammatory protein (MIP) 1α, MIP-1β, regulated upon activation, normal T-cell expressed, and secreted and stromal-cell derived factor 1 and subclinical mastitis. Univariate factors associated with infant HIV infection at 1 month postpartum included both detection and breadth of breast milk IFN-γ response (P = 0.08, P = 0.04, respectively), breast milk MIP-1β detection (P = 0.05), and plasma (P = 0.004) and breast milk (P = 0.004) viral load. In multivariate analyses adjusting for breast milk viral load and MIP-1β, breast milk IFN-γ responses were associated with an approximately 70% reduction in infant HIV infection [adjusted odds ratio (aOR) 0.29, 95% confidence interval (CI) 0.092-0.91], and each additional peptide pool targeted was associated with an approximately 35% reduction in infant HIV (aOR 0.65, 95% CI 0.44-0.97).

CONCLUSION

These data show breast milk HIV-gag-specific IFN-γ cellular immune responses are prevalent and may contribute to protection from early HIV transmission. More broadly, these data suggest breast milk cellular responses are potentially influential in decreasing mother-to-child transmission of viruses.

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.

Cumulative exposure to cell-free HIV in breast milk, rather than feeding pattern per se, identifies postnatally infected infants

In a nested case-control study, postnatal HIV infection was strongly associated with cumulative HIV RNA breastmilk exposure, even after allowing for maternal CD4 and plasma viral load; cases ingested approximately 15 times more HIV-1 RNA particles than controls.

Background. We quantified the relationship between human immunodeficiency virus (HIV) RNA shedding in breast milk, cumulative RNA exposure, and postnatal transmission, relating timing of infection in the infant to estimated total volume of milk exposure.

Methods. Nested case-control study of 36 infants of HIV-infected mothers. Case patients were infants who acquired HIV infection through breastfeeding from age 6 through 28 weeks, and control subjects were uninfected infants matched on age at obtainment of a breast milk sample. Mothers and infants received peripartum single-dose nevirapine prophylaxis. Feeding data were collected daily; breast milk samples were collected and infant anthropometry was performed at 6 weeks and monthly thereafter. Volume of milk ingested was estimated using infant weight and feeding pattern.

Results. Before HIV acquisition in case patients, feeding pattern (exclusive breastfeeding; median duration, 65 vs 70 days; P = .6) and daily milk intake (mean volume, 638 vs 637 mL; P = .97) did not differ significantly between case patients and control subjects. Case mothers were more likely to shed virus (64% vs 9% always, 22% vs 20.5% intermittently, 14% vs 70.5% never shed; overall, P < .001). Case patients ingested ∼15 times more HIV-1 RNA particles than did control subjects (196.5 vs 13 × 10⁶ copies; P < .001). Allowing for maternal antenatal CD4 cell count and plasma HIV-1 load, child sex and duration of mixed breastfeeding, the association between HIV RNA exposure and infection remained statistically significant (P < .001).

Conclusions. Postnatal acquisition of HIV-1 is more strongly associated with cumulative exposure to cell-free particles in breast milk than with feeding mode. Reducing breast milk viral load through antiretroviral therapy to mother or child can further decrease postnatal transmission in exclusively breastfed infants.

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.

The potential impact of CD4+ T cell activation and enhanced Th1/Th2 cytokine ratio on HIV-1 secretion in the lungs of individuals with advanced AIDS and active pulmonary infection

Bronchoalveolar lavage fluid (BALF) provides a source of mucosal CD4(+) T cells. We investigated the physiological properties of T lymphocytes from BALF and blood and their role on the dynamic of HIV-1 replication among AIDS patients with active lung infections. Pulmonary CD4(+) T cells consist mainly of effector memory cells (CD45RO(+) and CCR7(-)) with increased expression of activation markers (HLA-DR(+) and CD69(+)) when compared to the blood counterpart. We observed a high frequency of BALF cells capable of secreting HIV-1-Ags suggesting that the local lung environment may support favorable conditions for CD4(+) T lymphocytes harboring HIV-1 DNA to initiate the viral cycle. Nevertheless, the high number of IFN-γ-producing cells and the predominance of Th1 immune response in the lung could limit the secretion of HIV-1 RNA. In conclusion, the capacity of activated CD4(+) T cells to produce HIV-1 is driven by both the level and quality of cellular activation in the lung.

Infants with late breast milk acquisition of HIV-1 generate interferon-gamma responses more rapidly than infants with early peripartum acquisition

Infants infected with HIV-1 after the first month of life have a lower viral set-point and slower disease progression than infants infected before 1 month. We investigated the kinetics of HIV-1-specific CD8(+) T lymphocyte secretion of interferon (IFN)-gamma in infants infected before 1 month of life compared with those infected between months 1 and 12 (late infection). HIV-1 infection was assessed at birth and at months 1, 3, 6, 9 and 12 and timing of infection was determined by HIV-1 gag DNA from dried blood spots and verified by plasma HIV-1 RNA levels. HIV-1 peptide-specific IFN-gamma responses were measured by enzyme-linked immunospot at months 1, 3, 6, 9 and 12. Timing of development of IFN-gamma responses was compared using the log-rank test and Kaplan-Meier survival curves. Infants infected late developed HIV-1-specific CD8(+) T cell responses 2.8 months sooner than infants infected peripartum: 2.3 versus 5.1 months after HIV-1 infection (n = 52, P = 0.04). Late-infected infants had more focused epitope recognition than early-infected infants (median 1 versus 2 peptides, P = 0.03); however, there were no differences in the strength of IFN-gamma responses. In infants infected with HIV-1 after the first month of life, emergence of HIV-1-specific CD8(+) IFN-gamma responses is coincident with the decline in viral load, nearly identical to what is observed in adults and more rapid than in early-infected infants.

Functional Epstein-Barr virus reservoir in plasma cells derived from infected peripheral blood memory B cells

The Epstein-Barr virus (EBV) causes infectious mononucleosis, establishes latency in resting memory B lymphocytes, and is involved in oncogenesis through poorly understood mechanisms. The EBV lytic cycle is initiated during plasma cell differentiation by mRNAs transcripts encoded by BZLF1, which induce the synthesis of EBV proteins such as the immediate-early antigen ZEBRA and the late membrane antigen gp350. Therefore, we assessed the capacity of circulating EBV-infected B lymphocytes from healthy EBV-seropositive subjects to enter and complete the EBV lytic cycle. Purified B lymphocytes were polyclonally stimulated and BZLF1- or gp350-secreting cells (BZLF1-SCs or gp350-SCs) were enumerated by ELISpot assays. The number of BZLF1-SCs ranged from 50 to 480/107 lymphocytes (median, 80; 25th-75th percentiles, 70-150) and gp350-SCs from 10 to 40/107 lymphocytes (median, 17; 25th-75th percentiles, 10-20). gp350-SCs represented only 7.7% to 28.6% of BZLF1-SCs (median, 15%; 25th-75th percentiles, 10.5%-20%). This EBV functional reservoir was preferentially restricted to plasma cells derived from CD27(+) IgD(-) memory B lymphocytes. In 9 of 13 subjects, EBV DNA quantification in B-cell culture supernatants gave evidence of completion of EBV lytic cycle. These results demonstrate that EBV proteins can be secreted by EBV-infected B lymphocytes from healthy carriers, a majority generating an abortive EBV lytic cycle and a minority completing the cycle.

Low and undetectable breast milk interleukin-7 concentrations are associated with reduced risk of postnatal HIV transmission

OBJECTIVE

To investigate if breast milk interleukin [IL]-7 concentrations are associated with postnatal HIV transmission.

DESIGN

A case-control study nested within a cohort of women recruited in Lusaka, Zambia.

METHODS

IL-7 breast milk concentrations were measured in samples from 24 HIV-infected breast-feeding women who transmitted HIV to their child after the neonatal period and from 47 women who did not transmit. Samples were frequency-matched by the time of sample collection (1 week and 1 month postpartum). Logistic regression was used to adjust for possible confounders. For comparison, samples from 18 HIV-uninfected women from the same community were included in the analysis, and plasma IL-7 was determined.

RESULTS

Breast milk IL-7 concentrations were significantly higher than plasma IL-7 concentrations in all 3 groups. In contrast to levels among transmitters and HIV-uninfected women, breast milk IL-7 concentrations exhibited a bimodal distribution among nontransmitters. Breast milk IL-7 concentrations undetectable or less than 30 pg/mL were significantly associated with less HIV transmission (odds ratio = 0.13, 95% confidence interval: 0.03 to 0.64). The association remained strong after adjustment for breast milk viral load and sodium, maternal CD4 cell counts, parity, and time of sample collection.

CONCLUSION

Breast milk IL-7 may be necessary for effective HIV transmission.

Unintegrated HIV-1 provides an inducible and functional reservoir in untreated and highly active antiretroviral therapy-treated patients

Background

The presence of HIV-1 preintegration reservoir was assessed in an in vitro experimental model of latent HIV-1 infection, and in patients treated or not with highly active antiretroviral therapy (HAART).

Results

In resting CD4⁺ T lymphocytes latently infected in vitro with HIV-1, we demonstrated that the polyclonal activation induced a HIV-1 replication, which could be prevented by the use of an HIV-1 integrase inhibitor. We also showed that this reservoir was labile since the rescuable HIV-1-antigens production from unintegrated HIV-1 genomes declined over time. These data confirm that our experimental approach allows the characterization of a functional unintegrated HIV-1 reservoir. We then explored the preintegration reservoir in HIV-1-infected patients. This reservoir was detected in 11 of 12 untreated patients, in 4 of 10 sustained responders to HAART, and in one incomplete responder. This reservoir was also inducible, labile, and anti-HIV-1 integrase drug inhibited its induction. Finally, this reservoir was associated with the presence of spontaneous HIV-1 antigens producing CD4⁺ T cells in blood from 3 of 3 untreated patients and 2 of 2 sustained responders to HAART harboring a preintegration reservoir.

Conclusion

This preintegration phase of HIV-1 latency could be a consequence of the ongoing viral replication in untreated patients and of a residual viral replication in treated patients.

Preserving breastfeeding practice through the HIV pandemic

Breastfeeding, particularly for the first 6 months of life, is unquestionably the ideal way to feed most infants. However, the human immunodeficiency virus (HIV) pandemic has caused debate and confusion about the best way for HIV-positive mothers to feed their children. This review provides recent key findings and opinions around making breastfeeding safer for HIV-positive women, and argues for preservation of breastfeeding, as opposed to complete avoidance of breastfeeding for all HIV-positive women.

Isolation and characterization of HIV-1-infected resting CD4+ T lymphocytes in breast milk

An HIV-1 reservoir comprised primarily of latently infected resting CD4+ T lymphocytes that can be stimulated in vivo to produce virus may play a critical role in mother-to-child postnatal transmission of HIV-1 by breastfeeding. Here, we describe an experimental protocol for the detection of resting CD4+ T cell HIV-1 reservoir from breast milk. We adapted a method for the purification of resting CD4+ T lymphocytes in blood to isolate resting CD4+ T cells in breast milk from HIV-1-infected-lactating women (n=18) and from controls (n=3). Purified resting CD4+ T cells from blood and breast milk samples of HIV-1-infected-lactating women were polyclonally stimulated to characterize and enumerate HIV-1-antigen-secreting cells (HIV-1-Ag-SCs) by an enzyme-linked immunospot (ELISpot) assay. Resting CD4+ T cells represented more than 90% of purified viable breast milk cells. CD4+ T cell polyclonal stimulation combined with the ELISpot assay led to the characterization of a breast milk T cell HIV-1 reservoir greater than the blood reservoir (median 400 and 57.14 HIV-1-Ag-SCs/10(6) resting CD4+ T cells, respectively, p<0.001). Our strategy could be adapted to other body fluids and be useful for characterizing new HIV-1 reservoirs.