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Objective The impact of evolving guidelines and clinical practices on SARS-CoV-2-positive dyads across New York City Health and Hospitals during the early peak of COVID-19. Design A retrospective cohort study of positive-positive (P/P), positive-negative (P/N), and positive-untested (P/U) dyads delivered from March 1 to May 9, 2020. Wilcoxon rank sum, Chi-squared, and Fisher exact tests were used to analyze demographics, clinical variables, and system-wide management practices. Result A total of 2598 mothers delivered. 23.8% (286/1198) of mothers tested for SARS-CoV-2 were positive. 89.7% (260/ 290) newborns of SARS-CoV-2-positive mothers were tested and 11 were positive. Positive-positive newborns were more likely to be breastfed (81%), be admitted to NICU, and have longer length of stay (7.5 days) than P/N and P/U newborns. Conclusion Our study shows that varied testing, feeding, and isolation practices resulted in favorable short-term outcomes for SARS-CoV-2-positive mothers and their newborns. High-risk populations can be safely and effectively treated in resource-limited environments.

In December 2020, the first COVID-19 vaccines were approved for emergency use by the U.S. Food and Drug Administration, and vaccination efforts rapidly launched across the country. Concurrently, New York City experienced an increase in COVID-19 hospitalizations. This created an immediate need to inoculate frontline workers in a strained health system that lacked sufficient personnel to meet the demand. In response, New York State permitted medical students with appropriate clinical experience to administer vaccinations. Albert Einstein College of Medicine students rapidly stepped in to administer vaccines and serve as clinic navigators. Student leaders at Einstein collaborated with Montefiore Medical Center to rapidly implement a student vaccination initiative. Medical students underwent virtual and on-site training regarding COVID-19 vaccines and their administration. In January 2021, students began to staff vaccine clinics across the Bronx. By July 2021, 291 out of 830 eligible medical and Medical Scientist Training Program (MSTP) students (35.1%) had volunteered >2400 h. Of the 291 volunteers, 77 (26.5%) worked as vaccinators and administered approximately 2929 COVID-19 vaccines from January to May 2021. We demonstrate success using the concept of Entrustable Professional Activities (EPAs) in the context of training medical students in a specific clinical skill. Our framework resulted in the administration of approximately 2929 COVID-19 vaccines from January to May 2021. The authors believe that this framework can be implemented at peer institutions to alleviate the burden on hospital systems and outpatient clinics vaccinating their communities against COVID-19, or to meet future clinical needs.

The Class IA PI3 kinase isoforms (p110α, β, and δ) transduce many growth factor signals that are important for the proliferation, differentiation, and self-renewal of hematopoietic stem cells (HSCs). Mutations in growth factor receptors or RAS proteins are commonly observed in patients with acute myeloid leukemia (AML), leading to activation of the PI3K/AKT pathway. Therefore, PI3K inhibition is an attractive therapeutic strategy for a large subset of AML patients. We previously reported that p110α is dispensable for HSC function, suggesting that redundancy exists between the Class IA isoforms in HSCs (Gritsman et al., J Clin Invest 2014). However, we have identified a specific role for p110α in RAS-mutated myeloid leukemia. Furthermore, we found that the p110α-selective inhibitor BYL-719 can sensitize RAS-mutated leukemic cells to the MEK inhibitor MEK-162. While PI3K inhibitors have multiple clinical indications, including in hematologic malignancies, it is still unclear whether PI3K plays an important role in normal HSC function. Upon environmental stresses like chemotherapy or infection, quiescent HSCs must enter the cell cycle to re-establish homeostasis and promote emergency myelopoiesis. To test for redundancy between p110α and p110δ in HSCs, we generated p110α and p110δ double knockout (DKO) mice, with germline deletion of p110δ and conditional deletion of p110α. DKO mice have leukopenia, anemia, and decreased numbers of lymphoid-primed multipotent progenitors (LMPPs) in the bone marrow, though HSC numbers are unchanged. In competitive repopulation assays, B-cell maintenance was severely impaired, while the myeloid and T-cell lineages were relatively preserved. This suggests that HSC function is not impaired at steady state. We performed transcriptome analysis of DKO, p110δ, and p110α KO HSCs and LMPPs after bone marrow transplantation. Gene set enrichment analysis revealed downregulation of gene sets associated with cell cycle progression. Interestingly, we also observed negative enrichment of inflammatory response gene sets in both p110δ KO and DKO HSCs and LMPPs. To examine the roles of p110δ and α in the hematopoietic stress response, we injected p110δ, DKO, and WT mice with 5-fluorouracil. We observed significantly decreased survival of 5-FU-treated DKO mice due to impaired hematopoietic recovery, associated with the failure of HSCs to enter the cell cycle. Consistent with this finding, we also observed a decrease in myeloid reconstitution by DKO HSCs in secondary competitive transplantation, suggesting that p110α and p110δ play redundant roles in emergency myelopoiesis. We also observed defects in downstream signaling in DKO HSCs and progenitors in response to IL1β or TNFα stimulation. Our results suggest that p110α and δ act in a redundant fashion to transduce specific inflammatory signals in HSPCs in response to hematopoietic stress. Our results have important implications for the use of PI3K inhibitors in combination with chemotherapy and in other hematopoietic stress conditions. Citation Format: Shayda Hemmati, Taneisha Sinclair, Meng Tong, Boris Bartholdy, Rachel Okabe, Kristina Ames, Leanne Ostrodka, Tamanna Haque, Imit Kaur, Anupriya Agarwal, Jean Zhao, Thomas Roberts, Kira Gritsman. The PI3K isoforms in myeloid leukemia and hematopoietic stem cells [abstract]. In: Proceedings of the AACR Special Conference on Targeting PI3K/mTOR Signaling; 2018 Nov 30-Dec 8; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Res 2020;18(10_Suppl):Abstract nr IA18.

Myelodysplastic syndrome (MDS) is a clonal malignancy arising in hematopoietic stem cells (HSCs). The mechanisms of MDS initiation in HSCs are still poorly understood. The phosphatidylinositol 3-kinase (PI3K)/AKT pathway is frequently activated in acute myeloid leukemia, but in MDS, PI3K/AKT is often down-regulated. To determine whether PI3K down-regulation can perturb HSC function, we generated a triple knockout (TKO) mouse model with Pik3ca , Pik3cb , and Pik3cd deletion in hematopoietic cells. Unexpectedly, PI3K deficiency caused cytopenias, decreased survival, and multilineage dysplasia with chromosomal abnormalities, consistent with MDS initiation. TKO HSCs exhibit impaired autophagy, and pharmacologic autophagy induction improved HSC differentiation. Using intracellular LC3 and P62 flow cytometry and transmission electron microscopy, we also observed abnormal autophagic degradation in patient MDS HSCs. Therefore, we have uncovered an important protective role for PI3K in maintaining autophagic flux in HSCs to preserve the balance between self-renewal and differentiation and to prevent MDS initiation.

Hematopoietic stem cells (HSCs) are a rare population in the bone marrow (BM) that mostly exists in a quiescent state. Upon environmental stresses such as infection, inflammatory signals are released and induce HSCs to proliferate to quickly re-establish homeostasis and maintain the blood system. Many hematopoietic growth factors and chemokines signal through PI3K pathway. In hematopoietic cells, 3 Class IA PI3K isoforms are expressed (p110α, β, and δ), each encoded by a different gene. While p110α and p110β are ubiquitously expressed, p110δ is enriched in leukocytes. We previously showed that p110α is dispensable for HSC function (Gritsman et al, J Clin Invest 2014 124:1794-1809), suggesting redundancy between Class I PI3K isoforms in HSCs. To test for potential redundancy between p110α and p110δ in HSCs, we generated mice with conditional deletion of p110α and germline deletion of p110δ (DKO mice). DKO mice have anemia, leukopenia and decreased BM cellularity. While there is no change in HSC numbers, the number of lymphoid-primed multipotent progenitors (LMPPs) is significantly decreased. In the primary competitive repopulation assay, DKO BM cells fail to reconstitute the B cell lineage, while the myeloid and T cell lineages were relatively preserved. However, in a secondary competitive transplantation setting, we also observed a significant decrease in myeloid reconstitution, suggesting that p110α and p110δ play redundant roles in emergency myelopoiesis. To examine effects of p110α and p110δ deletion on gene expression, we performed microarray analysis of WT, DKO, p110δ-/-, and p110α-/- hematopoietic stem and progenitor cells (HSPCs) after bone marrow transplantation. Gene set enrichment analysis revealed negative enrichment of gene sets associated with inflammatory response pathways in both DKO HSCs and LMPPs. In DKO HSCs, we also observed negative enrichment of gene sets associated with cell cycle progression. To further examine the roles of p110δ and p110α in the hematopoietic stress response, we injected DKO, p110δ-/-, and WT; Mx1-Cre mice with 5-fluorouracil (5-FU). We observed decreased survival of 5-FU-treated DKO mice associated with impaired hematopoietic recovery, and with the failure of HSCs to enter the cell cycle. Given the important roles of inflammatory signaling pathways in HSC activation and emergency myelopoiesis, we examined the roles of p110α and p110δ in signal transduction in HSPCs in response to IL1β or TNFα. Our phospho-flow cytometry analysis revealed a decrease in p38-MAPK phosphorylation in both p110δ-/- and DKO HSPCs, both at baseline and after stimulation with either IL1β or TNFα. To confirm these results, we stimulated p110δ KO and DKO cKit-enriched bone marrow cells with IL1β or TNFα. We observed a significant decrease in both p38-MAPK phosphorylation and phosphorylation of Akt at Ser473 in DKO cells, but not in p110δ-/- cells, both at baseline and with IL1-β or TNF-α stimulation. This suggests that both p110α and p110δ are required for optimal transduction of IL1β or TNFα in hematopoietic progenitors. Surprisingly, we found that DKO HSPCs can enter the cell cycle normally upon in vivo stimulation with lipopolysaccharide (LPS), which simulates bacterial infection. Our results suggest that p110α and δ act in a redundant fashion to transduce specific inflammatory signals in HSPCs, such as IL1β and TNFα, in response to hematopoietic stress. Our findings have important implications for the use of PI3K inhibitors in combination with chemotherapy and in the setting of infection or inflammation. Disclosures No relevant conflicts of interest to declare.

Hematopoietic stem cells (HSCs) maintain the blood system through a delicate equilibrium between self-renewal and differentiation. Most hematopoietic growth factors and cytokines signal through phosphoinositide 3-kinase (PI3K) via three Class IA catalytic PI3K isoforms (P110α, β, and δ), encoded by Pik3ca, Pik3cb, and Pik3cd, respectively. The PI3K/AKT pathway is commonly activated in acute myeloid leukemia (AML), and PI3K is a common therapeutic target in cancer. However, it is not known whether PI3K is required for HSC differentiation or self-renewal. We previously demonstrated that individual PI3K isoforms are dispensable in HSCs1,2. To determine the redundant roles of PI3K isoforms in HSCs, we generated a triple knockout (TKO) mouse model with deletion of all three Class IA PI3K isoforms in the hematopoietic system. Surprisingly, we observed significant expansion of TKO HSCs after transplantation, with decreased differentiation capacity and impaired multilineage repopulation. Additionally, the bone marrow of TKO mice exhibited myelodysplastic features with chromosomal abnormalities. Interestingly, we found that macroautophagy (thereafter autophagy) is impaired in TKO HSCs, and that pharmacologic induction of autophagy improves their differentiation. Therefore, we have uncovered important roles for PI3K in autophagy regulation in HSCs to maintain the balance between self-renewal and differentiation.

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