Background
Despite highly effective preventive interventions, perinatal HIV infections continue to occur. Our objective was to describe factors associated with new incident HIV infections among Canadian-born children in the last decade, to better understand remaining gaps in the elimination of perinatal HIV infection in Canada.

Methods
Data were analyzed from the Canadian Perinatal HIV Surveillance Program (CPHSP), collected annually from 22 perinatal HIV centers. Demographic and clinical data for children living with HIV (CLHIV) were extracted and analyzed.

Results
197 CLHIV were registered in the CPHSP database between 2012-2021, of whom 36(18.3%) had been born in Canada. Of these Canadian-born children, 92% were confirmed perinatal infections, while 3 were acquired non-perinatally. Most new infections occurred in central Canada (QC/ON)(50%), followed by the Prairies (AB/SK/MB)(39%), Northwest (BC & territories)(8.3%), and Atlantic provinces (2.7%).
Among the 33 perinatal transmissions, 11(33%) mothers had been diagnosed prior to delivery, 7(21%) at delivery and 14(42%) after delivery. In those diagnosed antenatally, likely reasons for transmission included difficulties engaging in care (3), delayed access to care due to recent immigration (2) and late diagnosis in pregnancy (3). Of those diagnosed at delivery, barriers included difficulties engaging in care (3) and failure to screen for HIV in pregnancy despite engagement in care (2). Of those diagnosed after delivery, 9 had had negative first trimester testing, while 3 were not tested during pregnancy. Median age at HIV diagnosis for CLHIV born to women diagnosed after delivery was 22 months [IQR 5.75-38.75]; 6 presented with opportunistic infections, while 7 were diagnosed following parental diagnosis.

Conclusion
Of current Canadian CLHIV, one in five was Canadian-born in the last decade. While significant gains have been made in eliminating perinatal infection, seroconversion after first trimester testing, difficulties engaging in care, and failure to screen in pregnancy remain gaps in perinatal HIV prevention.

Background
There is increasing recognition that children who were HIV exposed and uninfected (CHEU) are at increased risk of morbidity compared to children HIV unexposed and uninfected (CHUU) controls. With an estimated 1.5 million CHEU born annualy, there is therefore a need to identify which specific CHEU may be at risk of adverse outcomes in order to better direct health services for these children.

Methods
Longitudinal cohort study linking data from the Centre maternel et infantile sur le SIDA (CMIS; CHU Sainte-Justine) cohort in Montreal to administrative data from the Régie de l’assurance maladie du Québec (RAMQ). CHEU were matched 1:3 by birth’s year, sex and postal code, to CHUU controls, to compare the risk of hospitalization between them.

Results
Among 847 CHEU enrolled in the CMIS cohort between 1988 and 2015, 726 were linked to the RAMQ database and matched to 2178 CHUU. There was a significantly higher risk of hospitalization among CHEU at 5-years (Incidence Rate Ratio 1.59[1.39-1.82]). Among CHEU, significant risk factors for hospitalization on univariate analysis included birth’s year prior to 2005, prematurity, groth delay, detectable maternal viral load, lower maternal CD4 count, maternal IV drug use, and hepatitis C co-infection (Figure1). Only birth’s year was significant in multivariate analysis.

Conclusion
In this resource-rich setting with universal health-care, significant risk factors for hospitalization among CHEU were defined by severity of maternal HIV disease and associated co-infections. These data suggest that infants born to women with advanced HIV disease or co-infections may benefit from enhanced pediatric care.

Background: Migration contributes significantly to new HIV cases in Canada. We describe geographic origin trends among mothers living with HIV and children with vertical infection and the impact of geographic origin on vertical HIV transmission (VT) rates among mother-infant pairs (MIPs) in Canada from 2008-2021.

Methods: The Canadian Perinatal HIV Surveillance Program collects data at 22 centres across Canada. Data reviewed included: antiretroviral use, HIV suppression and infant outcomes. Chi square and Fisher’s exact test were used to determine VT rate differences for foreign-born (FBM) versus Canadian-born mothers (CBM).

Results: 3322 MIPs were identified and 1934 (58.2%) were FBM. The majority of FBP were born in Africa (1505), followed by the Caribbean (214), Asia (110), South and Central America (55), Europe (47) and the United States (3). Of African-born mothers, 22%, 26%, 16%, 24% came from Central, East, Horn and West Africa, respectively. The largest numbers of FBM originated from Congo (9.4%), Ethiopia (9.2%), Nigeria (8.9%) and Haiti (6.2%). Over the past 14 years, there has been a decrease in mothers from Haiti and increases in mothers from Congo, Ethiopia and Nigeria. Compared to CBM, FBM were more likely to be diagnosed prior to pregnancy (90.5% vs 82.9%, p<0.001) and to be on ARV at the time of conception (70.7% vs 52.0%, p<0.001), and more likely to be virally suppressed near delivery (90.9% vs 81.5%, p<0.001). Accordingly, VT rate was 1.1% among infants born to FBM versus 2.2% among infants born to CBM (p=0.018).

Conclusions: Geographic origins of HIV+ FBM in Canada have changed over time, shifting to predominantly African in the past 14 years. FBM have higher rates of HIV suppression and lower rates of VT compared to CBM. Understanding the impact of global migration and country-specific cultural and obstetrical/paediatric health issues is imperative to providing optimal HIV care.

Background: Exclusive formula feeding remains the preferred infant feeding recommendation for women living with HIV (WLWH) in Canada because vertical transmission (VT) through breastfeeding can occur despite an undetectable maternal viral load (VL). In recent years, some mothers on combination antiretroviral therapy (ART) have elected to breastfeed their infants after informed decision-making. The objective of this study was to describe demographic characteristics, management and outcomes of breast-fed infants born to WLWH in Toronto, Canada.
Methods: A retrospective chart review of all known breastfed infants born to WLWH in Toronto, Canada from 2015-2022. Demographic characteristics, management and clinical outcomes were reviewed.
Results: Twenty-six breastfed infants (1 set of twins) and 20 mothers were included. The median age of mothers at entry to prenatal care was 34.5 years (range 22-47 years); 85% (17/20) were foreign-born. All mothers were on ART during pregnancy and 92% (23/25 pregnancies) had virologic suppression at delivery (2 had detectable VL, 40 copies/mL and 136 copies/mL, respectively). The most common indicated reasons for breastfeeding were bonding with baby, health benefits to baby, and fear of inadvertent HIV disclosure. Median breastfeeding duration was 11 weeks (range 1 day-49 weeks). Fifteen infants exclusively breastfed and 11 mixed-fed. Infant antiretroviral prophylaxis consisted of zidovudine/lamivudine/nevirapine (21/26), zidovudine only (3/26), and nevirapine only (2/26); 88% (22/25) of infants remained on prophylaxis until 1 month after weaning (1 still breastfeeding). No cases of VT were observed. No safety concerns led to discontinuation of infant ART.
Conclusions: Increasingly, WLWH on effective ART are choosing to breastfeed their infants after informed discussions with their care providers. This is the largest series of Canadian data demonstrating no episodes of VT and no safety concerns of extended ART in breastfeeding infants. This information will inform consensus Canadian guidelines on counselling and management of breastfeeding WLWH and their infants.

Each year, ~1.1M children are cART-exposed in utero to prevent vertical transmission of HIV. A recent study demonstrated that second-generation InSTIs bictegravir (BIC), cabotegravir (CAB), and dolutegravir (DTG) exert toxic effects in cultured human embryonic stem cells (hESCs) and a pregnancy mouse model. As their safety is not fully elucidated during pregnancy, our objective was to characterize the effects of four InSTIs in two hESC lines, with respect to markers of early germ layer differentiation.

CA1S and H9 hESCs (n=4 independent experiments) were directed to differentiate towards ectoderm (7-days), endoderm (5-days), or mesoderm (5-days) lineages. During culture, cells were exposed to BIC, CAB, DTG or raltegravir (RAL) (all at 0.5X peak plasma drug concentration) or 0.1% DMSO diluent control. At harvest, hESCs were counted and assessed via flow cytometry for viability, and ectoderm (PAX6+/NESTIN+), endoderm (SOX17+/FOXA2+), or mesoderm (TBXT+/CXCR4+) lineages. InSTI-exposed hESCs were compared to DMSO controls by one-way ANOVA with Bonferroni correction.

CA1S hESCs exposed to BIC, CAB, or DTG during differentiation exhibited decreased proliferation (all ≥2-fold, p≤0.03), and BIC exposure reduced viability (2.5-fold) during mesoderm differentiation (p<0.001). CA1S hESCs directed to differentiate toward ectoderm with CAB or DTG exposure showed a ≥90% decrease in ectoderm marker expression (p≤0.007). No changes were detected for cells differentiated toward endoderm or mesoderm. In H9 hESCs, exposure to BIC, CAB, and DTG was so cytotoxic that too few cells remained for flow. In both hESC lines, RAL did not induce any cytotoxicity or differentiation dysregulation.

Second-generation InSTIs can dysregulate ectoderm differentiation, which gives rise to neural tube, neural crest cells, and epidermis. In contrast, RAL exhibited a profile similar to controls, a reassuring finding warranting further clinical investigation. Now that cART has virtually eliminated HIV vertical transmission, it is imperative to concentrate on safety in the context of pregnancy and embryonic development.

Introduction. Integrase strand transfer inhibitors (INSTIs) and non-nucleoside reverse transcriptase inhibitors (NNRTIs) are common antiretroviral therapies for pregnant people with HIV. Both have been associated with small-for-gestational-age babies and metabolic complications. The system L-amino acid transporter system is pivotal to normal fetal growth. The Na+-independent system L transporters (LAT1, LAT2) are expressed in the placenta but have not been investigated in the context of HIV/antiretroviral exposure. We hypothesize that the expression of system L transporters in the placenta will be altered by antiretrovirals and that this may contribute to poor fetal outcomes.

Methods. Term placentas were collected from 22 Canadian people (16 with HIV, 6 HIV-negative). People with HIV were either on INSTI-based (raltegravir or dolutegravir) or NNRTI-based (nevirapine or efavirenz) antiretroviral regimens. Protein levels of LAT1 and LAT2 were quantified in placenta tissues by Western blot. Placental distribution of LAT1 was confirmed by immunofluorescence. Statistical analyses were performed in GraphPad Prism (v9.0.1).

Results. Babies and placentas were significantly smaller in the NNRTI group than in the control and INSTI groups. LAT2 protein levels were lower in the NNRTI group and correlated with birth weight centile. In contrast, LAT2 protein levels were significantly elevated in the INSTI group compared to controls. LAT1 protein levels were only significantly decreased in the INSTI group compared to the NNRTI group. Immunostaining of LAT1 showed expression in the placental blood vessels and was lower in placentas exposed to INSTIs vs. controls.

Conclusions. Our data suggest differential expression of LAT1 and LAT2 in INSTI vs. NNRTI-exposed placentas. Higher LAT2 in INSTI-exposed placentas may be a compensatory mechanism to account for lower LAT1. Further work is required to determine the differential contributions of the System L transporters to amino acid transfer and how they affect birth outcomes in people taking antiretroviral therapy.

Introduction. Antiretroviral (ARV) use during pregnancy in individuals with HIV is important for maternal health and minimizing perinatal transmission. However, ARVs have been associated with increased risk for adverse birth outcomes including preterm births (PTB) and small for gestational age (SGA) births. The mechanism underlying these adverse effects remain poorly understood. ARV-associated effects on key pathways regulating placenta development and function, including angiogenesis, may contribute to adverse outcomes. We hypothesize that NNRTI use will alter the expression of two key angiogenic factors, angiopoietin-1 and angiopoietin-2, potentially contributing to altered placentation and adverse birth outcomes.

Methods. Term placentas from 16 Canadian individuals (6 HIV positive controls and 10 HIV negative individuals) were included. All individuals with HIV were taking NNRTI-based (nevirapine or efavirenz) ARV regimens. Angiopoietin-1 and 2 protein expression was quantified via Western blot and morphological observations were made via immunohistochemistry for cytokeratin and smooth muscle actin, and H&E staining.

Results. Compared to controls, angiopoietin-1 expression levels were significantly higher in NNRTI-exposed placentas (p<0.005), while angiopoietin-2 expression levels were lower in the NNRTI-exposed placentas compared to controls. Angiopoietin-1/Angiopoietin-2 ratio was significantly higher in the NNRTI-group compared to controls (p<0.005), indicating a potential shift to non-branching angiogenesis. This was supported by immunohistochemical studies showing a prevalence of intermediate villi, and a lack of terminal villi. The stem and intermediate villi of NNRTI-exposed placentas also showed long non-branched blood vessels, while the terminal villi had small, occluded vessels, indicative of non-branching angiogenesis and advanced villous maturation.

Conclusions. Our data provides evidence that NNRTI exposure during pregnancy may influence angiopoietin balance towards a switch from branching to non-branching angiogenesis. Our findings highlight the need for closer investigation of ARVs and their effects on the placenta.

Background: Potential bidirectional drug-drug interactions (DDIs) between feminizing hormone therapy (FHT) and antiretroviral therapy (ART) are of concern for trans women living with HIV and their healthcare providers. As preliminary exploration of this issue, this study aimed to characterize prescribing patterns of FHT and ART among trans women living with HIV and to compare serum estradiol levels to trans women without HIV.

Methods: Retrospective chart review of trans women engaged with primary, HIV, or endocrinology care was completed at seven clinics in Toronto and Montreal from 2018-2019. FHT use (yes vs. no), type of anti-androgen and estrogen, and serum estradiol levels were compared based on HIV status (positive, negative, missing/unknown) using chi-square or Fisher’s exact and Kruskal-Wallis tests for categorical and continuous variables, respectively.

Results: Of 1,495 trans women, there were 86 trans women with HIV, of whom 79 (91.8%) were on ART. ART regimens were most commonly integrase inhibitor-based (67.4%). Fewer (71.8%) trans women with HIV were prescribed FHT, compared to 88.4% of those without HIV and 90.2% of those with missing/unknown HIV status (p<0.001). Of the trans women on FHT with recorded serum estradiol (n=1,153), there was no statistical difference in serum estradiol between those with HIV (median: 203 pmol/L, IQR: 95.5, 417.5) and those with negative HIV status (200 pmol/L [113, 407]) or those with missing/unknown HIV status (227 pmol/L [127.5, 384.5) (p=0.633).

Conclusions: In this chart review, trans women with HIV were prescribed FHT less often than trans women with negative or unknown HIV status. There was no statistical difference in serum estradiol levels of trans women on FHT regardless of HIV status. Further research on DDIs between FHT and ART is needed to better meet the health needs of trans women living with HIV.