The gut microbiota is associated with immune cell dynamics in humans.

The gut microbiota influences development1-3 and homeostasis4-7 of the mammalian immune system, and is associated with human inflammatory8 and immune diseases9,10 as well as responses to immunotherapy11-14. Nevertheless, our understanding of how gut bacteria modulate the immune system remains limited, particularly in humans, where the difficulty of direct experimentation makes inference challenging. Here we study hundreds of hospitalized-and closely monitored-patients with cancer receiving haematopoietic cell transplantation as they recover from chemotherapy and stem-cell engraftment. This aggressive treatment causes large shifts in both circulatory immune cell and microbiota populations, enabling the relationships between the two to be studied simultaneously. Analysis of observed daily changes in circulating neutrophil, lymphocyte and monocyte counts and more than 10,000 longitudinal microbiota samples revealed consistent associations between gut bacteria and immune cell dynamics. High-resolution clinical metadata and Bayesian inference allowed us to compare the effects of bacterial genera in relation to those of immunomodulatory medications, revealing a considerable influence of the gut microbiota-together and over time-on systemic immune cell dynamics. Our analysis establishes and quantifies the link between the gut microbiota and the human immune system, with implications for microbiota-driven modulation of immunity.

Microbiota-derived lantibiotic restores resistance against vancomycin-resistant Enterococcus.

Intestinal commensal bacteria can inhibit dense colonization of the gut by vancomycin-resistant Enterococcus faecium (VRE), a leading cause of hospital-acquired infections1,2. A four-strained consortium of commensal bacteria that contains Blautia producta BPSCSK can reverse antibiotic-induced susceptibility to VRE infection3. Here we show that BPSCSK reduces growth of VRE by secreting a lantibiotic that is similar to the nisin-A produced by Lactococcus lactis. Although the growth of VRE is inhibited by BPSCSK and L. lactis in vitro, only BPSCSK colonizes the colon and reduces VRE density in vivo. In comparison to nisin-A, the BPSCSK lantibiotic has reduced activity against intestinal commensal bacteria. In patients at high risk of VRE infection, high abundance of the lantibiotic gene is associated with reduced density of E. faecium. In germ-free mice transplanted with patient-derived faeces, resistance to VRE colonization correlates with abundance of the lantibiotic gene. Lantibiotic-producing commensal strains of the gastrointestinal tract reduce colonization by VRE and represent potential probiotic agents to re-establish resistance to VRE.

The Effect of Neutropenia and Filgrastim (G-CSF) on Cancer Patients With Coronavirus Disease 2019 (COVID-19) Infection.

BACKGROUND: Neutropenia is commonly encountered in cancer patients. Recombinant human granulocyte colony-stimulating factor (G-CSF, filgrastim), a cytokine that initiates proliferation and differentiation of mature granulocytes, is widely given to oncology patients to counteract neutropenia, reducing susceptibility to infection. However, the clinical impact of neutropenia and G-CSF use in cancer patients with coronavirus disease 2019 (COVID-19) remains unknown. METHODS: An observational cohort of 379 actively treated cancer patients with COVID-19 was assembled to investigate links between concurrent neutropenia and G-CSF administration on COVID-19-associated respiratory failure and death. These factors were encoded as time-dependent predictors in an extended Cox model, controlling for age and underlying cancer diagnosis. To determine whether the degree of granulocyte response to G-CSF affected outcomes, the degree of response to G-CSF, based on rise in absolute neutrophil count (ANC) 24 hours after growth factor administration, was also incorporated into a similar Cox model. RESULTS: In the setting of active COVID-19 infection, outpatient receipt of G-CSF led to an increased number of hospitalizations (hazard ratio [HR]: 3.54, 95% confidence interval [CI]: 1.25-10.0, P value: .017). Furthermore, among inpatients, G-CSF administration was associated with increased need for high levels of oxygen supplementation and death (HR: 3.56, 95% CI: 1.19-10.2, P value: .024). This effect was predominantly seen in patients that exhibited a high response to G-CSF based on their ANC increase post-G-CSF administration (HR: 7.78, 95% CI: 2.05-27.9, P value: .004). CONCLUSIONS: The potential risks versus benefits of G-CSF administration should be considered in neutropenic cancer patients with COVID-19, because G-CSF administration may lead to worsening clinical and respiratory status.

COVID-19 in patients with cancer: can baseline radiologic severity and early evolution predict clinical outcomes?

OBJECTIVE: To determine whether the degree of parenchymal involvement on chest radiograph (CXR) at the time of COVID-19 diagnosis and its early radiologic evolution can predict adverse events including hospitalization, intubation, and death in patients with cancer. METHODS: Retrospective study of 627 COVID-19-positive patients between March and April 2020, of which 248 had baseline CXR within 72 h of diagnosis and 64 patients had follow-up wihtin72 h. CXRs were classified as abnormal (i.e., radiologic findings suggestive of COVID-19 infection were noted), normal, or indeterminate. Baseline and follow-up severity scores were calculated based on lung regions in abnormal CXRs. Statistical analysis was performed to determine associations between abnormal CXR or severity score with adverse events. RESULTS: Of 248 patients (median age = 65) with a baseline CXR, 172/248 (69%) had an abnormal baseline study, which was associated with hospitalization (p < 0.001), intubation (p = 0.001), and death (p = 0.005). For patients with solid neoplasms, when adjusted for stage, it was associated with hospitalization (p = 0.0002), intubation (p = 0.019), and death (p = 0.03). The median baseline severity score was 3 (range = 1-10); the greater the score, the higher the likelihood of adverse outcome (p < 0.003 for all). A baseline severity score > 9 predicted > 50% probability of intubation and a score of ≥ 10 predicted > 50% of probability of death. The baseline severity score was not correlated with cancer-related treatment. Early radiologic progression was not correlated with hospitalization, intubation, or death. CONCLUSION: The degree of parenchymal involvement on CXR within 72 h of COVID-19 diagnosis is associated with adverse outcomes in patients with cancer. KEY POINTS: • In patients with cancer, the presence and severity of radiologic manifestation of COVID-19 on chest radiographs within 72 h of COVID-19 diagnosis are associated with hospitalization, intubation, and death. • Early radiologic progression on chest radiographs is not correlated with adverse outcomes.

Performance of the sona Aspergillus Galactomannan Lateral Flow Assay in a Cancer Patient Population.

The diagnosis of invasive aspergillosis can be challenging in cancer patients. Herein, the analytical and clinical performance of the sona Aspergillus galactomannan lateral flow assay (GM LFA) was evaluated and its performance compared to that of the Bio-Rad galactomannan enzyme immunoassay (GM EIA). Serum and bronchoalveolar lavage (BAL) fluid samples received for GM EIA testing between March and August 2019 were included. Positive and negative percent agreement (PPA and NPA) were calculated for the GM LFA compared to the GM EIA. Discrepant analysis was performed by review of the patient's medical records assessing for any evidence of a fungal infection. Five hundred thirty-three samples (85 BAL samples and 448 serum samples) from 379 patients were included in the study. The overall PPA and NPA were 100% (95% confidence interval [CI], 72.2 to 100%) and 97.5% (95% CI, 95.5 to 98.4%), respectively. Fourteen of 24 samples were positive by LFA only. The sensitivity of the GM LFA for proven and probable invasive aspergillosis (IA) was 100% (95% CI, 51.0 to 100%) and 87.5% (95% CI, 55.9 to 99.4%), with a specificity of 95.5% (95% CI, 92.3 to 97.2%) and 96.2% (95% CI, 93.4 to 97.7%), respectively. The sensitivity of the GM EIA for proven and probable IA was 25% (95% CI, 1.28 to 69.9%) and 62.5% (95% CI, 30.6 to 86.3%), with a specificity of 98.2% (95% CI, 96.2 to 99.1%) and 99.2% (95% CI, 97.7 to 99.8%), respectively. The Aspergillus GM LFA outperformed the Aspergillus GM EIA for the detection of the galactomannan antigen in our patient population. The simplicity and rapid time to results makes the Aspergillus GM LFA easy to implement in a wide range of laboratory settings.

Projecting COVID-19 disease severity in cancer patients using purposefully-designed machine learning.

BACKGROUND: Accurately predicting outcomes for cancer patients with COVID-19 has been clinically challenging. Numerous clinical variables have been retrospectively associated with disease severity, but the predictive value of these variables, and how multiple variables interact to increase risk, remains unclear. METHODS: We used machine learning algorithms to predict COVID-19 severity in 348 cancer patients at Memorial Sloan Kettering Cancer Center in New York City. Using only clinical variables collected on or before a patient's COVID-19 positive date (time zero), we sought to classify patients into one of three possible future outcomes: Severe-early (the patient required high levels of oxygen support within 3 days of being tested positive for COVID-19), Severe-late (the patient required high levels of oxygen after 3 days), and Non-severe (the patient never required oxygen support). RESULTS: Our algorithm classified patients into these classes with an area under the receiver operating characteristic curve (AUROC) ranging from 70 to 85%, significantly outperforming prior methods and univariate analyses. Critically, classification accuracy is highest when using a potpourri of clinical variables - including basic patient information, pre-existing diagnoses, laboratory and radiological work, and underlying cancer type - suggesting that COVID-19 in cancer patients comes with numerous, combinatorial risk factors. CONCLUSIONS: Overall, we provide a computational tool that can identify high-risk patients early in their disease progression, which could aid in clinical decision-making and selecting treatment options.

Impact of gut colonization with butyrate-producing microbiota on respiratory viral infection following allo-HCT.

Respiratory viral infections are frequent in patients undergoing allogeneic hematopoietic stem cell transplantation (allo-HCT) and can potentially progress to lower respiratory tract infection (LRTI). The intestinal microbiota contributes to resistance against viral and bacterial pathogens in the lung. However, whether intestinal microbiota composition and associated changes in microbe-derived metabolites contribute to the risk of LRTI following upper respiratory tract viral infection remains unexplored in the setting of allo-HCT. Fecal samples from 360 allo-HCT patients were collected at the time of stem cell engraftment and subjected to deep, 16S ribosomal RNA gene sequencing to determine microbiota composition, and short-chain fatty acid levels were determined in a nested subset of fecal samples. The development of respiratory viral infections and LRTI was determined for 180 days following allo-HCT. Clinical and microbiota risk factors for LRTI were subsequently evaluated using survival analysis. Respiratory viral infection occurred in 149 (41.4%) patients. Of those, 47 (31.5%) developed LRTI. Patients with higher abundances of butyrate-producing bacteria were fivefold less likely to develop viral LRTI, independent of other factors (adjusted hazard ratio = 0.22, 95% confidence interval 0.04-0.69). Higher representation of butyrate-producing bacteria in the fecal microbiota is associated with increased resistance against respiratory viral infection with LRTI in allo-HCT patients.

Insights into pathogenesis of fatal COVID-19 pneumonia from histopathology with immunohistochemical and viral RNA studies.

INTRODUCTION: We describe post-mortem pulmonary histopathologic findings of COVID-19 pneumonia in patients with a spectrum of disease course, from rapid demise to prolonged hospitalisation. METHODS AND RESULTS: Histopathologic findings in post-mortem lung tissue from eight patients who died from COVID-19 pneumonia were reviewed. Immunohistochemistry (IHC) and next-generation sequencing (NGS) were performed to detect virus. Diffuse alveolar damage (DAD) was seen in all cases with a spectrum of acute phase and/or organising phase. IHC with monoclonal antibodies against SARS-CoV-2 viral nucleoprotein and spike protein detected virus in areas of acute but not organising DAD, with intracellular viral antigen and RNA expression seen predominantly in patients with duration of illness less than 10 days. Major vascular findings included thrombi in medium- and large-calibre vessels, platelet microthrombi detected by CD61 IHC and fibrin microthrombi. CONCLUSIONS: Presence of SARS-CoV-2 viral RNA by NGS early in the disease course and expression of viral antigen by IHC exclusively in the acute, but not in the organising phase of DAD, suggests that the virus may play a major role in initiating the acute lung injury of DAD, but when DAD progresses to the organising phase the virus may have been cleared from the lung by the patient's immune response. These findings suggest the possibility of a major change during the disease course of COVID-19 pneumonia that may have therapeutic implications. Frequent thrombi and microthrombi may also present potential targets for therapeutic intervention.

Rethinking the need for a platelet transfusion threshold of 50 × 109 /L for lumbar puncture in cancer patients.

BACKGROUND: Lumbar puncture (LP) is a frequently performed diagnostic and therapeutic procedure in oncology patients. Transfusing to a minimum preprocedural platelet threshold of 50 × 109 /L is widely upheld without good quality evidence. The objective was to compare the outcomes of LPs performed with platelets above and below this threshold. An increased risk of adverse events in patients with lower platelet counts was not expected. As a corollary, transfusion reaction rates incurred by transfusing to this recommended threshold are also reported. METHODS: A total of 2259 LPs performed on 1137 oncology patients (adult, n = 871, and pediatric, n = 266) were retrospectively analyzed between February 2011 and December 2017. The incidence of LP-related complications for groups above and below the minimum platelet threshold was compared. Traumatic tap was defined as 500 or more red blood cells per high-power field in the cerebral spinal fluid. Groups were compared using the 2-Proportion Z-test and Fisher exact test. RESULTS: At time of LP, the total number of events with platelets less than 50 × 109 /L and 50 × 109 /L or greater were 110 and 2149, respectively. There were no significant differences in LP-associated complications between patients with platelet counts above or below 50 × 109 /L (P = .29). Patients with a pre-LP platelet count of less than 50 × 109 /L had a higher proportion of traumatic taps (P < .001). Three patients developed transfusion-related adverse events. CONCLUSION: Patients with platelet counts less than 50 × 109 /L did not have a higher incidence of clinically significant post-lumbar puncture complications (P = .29).

Antibiotic-Induced Shifts in Fecal Microbiota Density and Composition during Hematopoietic Stem Cell Transplantation.

Dramatic microbiota changes and loss of commensal anaerobic bacteria are associated with adverse outcomes in hematopoietic cell transplantation (HCT) recipients. In this study, we demonstrate these dynamic changes at high resolution through daily stool sampling and assess the impact of individual antibiotics on those changes. We collected 272 longitudinal stool samples (with mostly daily frequency) from 18 patients undergoing HCT and determined their composition by multiparallel 16S rRNA gene sequencing as well as the density of bacteria in stool by quantitative PCR (qPCR). We calculated microbiota volatility to quantify rapid shifts and developed a new dynamic systems inference method to assess the specific impact of antibiotics. The greatest shifts in microbiota composition occurred between stem cell infusion and reconstitution of healthy immune cells. Piperacillin-tazobactam caused the most severe declines among obligate anaerobes. Our approach of daily sampling, bacterial density determination, and dynamic systems modeling allowed us to infer the independent effects of specific antibiotics on the microbiota of HCT patients.

Clinical Performance of (1,3) Beta-D Glucan for the Diagnosis of Pneumocystis Pneumonia (PCP) in Cancer Patients Tested With PCP Polymerase Chain Reaction.

BACKGROUND: Serum (1,3)-beta-D glucan (BDG) is increasingly used to guide the management of suspected Pneumocystis pneumonia (PCP). BDG lacks specificity for PCP, and its clinical performance in high-risk cancer patients has not been fully assessed. Polymerase chain reaction (PCR) for PCP detection is highly sensitive, but cannot differentiate between colonization and infection. We evaluated the diagnostic performance of serum BDG in conjunction with PCP PCR on respiratory samples in patients with cancer and unexplained lung infiltrates. METHODS: We performed a retrospective analysis of adult patients evaluated for PCP at our institution from 2012 to 2015, using serum BDG and PCP PCR. The sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of the serum BDG at different thresholds were evaluated using PCP PCR alone or in conjunction with clinical presentation in PCP PCR-positive patients. RESULTS: With PCP PCR alone as the reference method, BDG (≥80 pg/mL) had a sensitivity of 69.8%, specificity of 81.2%, PPV of 34.6%, and NPV of 95.2% for PCP. At ≥200 pg/mL in patients with a positive PCR and a compatible PCP clinical syndrome, BDG had a sensitivity of 70%, specificity of 100%, PPV of 100%, and NPV of 52.0% for PCP. CONCLUSIONS: Patients negative by both BDG and PCR were unlikely to have PCP. In patients with a compatible clinical syndrome for PCP, higher BDG values (>200 pg/mL) were consistently associated with clinically-significant PCP infections among PCP PCR-positive oncology patients.

Distinctive Infectious Complications in Patients with Central Nervous System Lymphoma Undergoing Thiotepa, Busulfan, and Cyclophosphamide-conditioned Autologous Stem Cell Transplantation.

We investigated the incidence of viral, fungal, bacterial, and parasitic infections observed in 57 patients with central nervous system lymphoma after thiotepa, busulfan, and cyclophosphamide-conditioned autologous stem cell transplantation (TBC-ASCT) and 79 patients with systemic non-Hodgkin lymphoma after traditional carmustine, etoposide, cytarabine, and melphalan-conditioned ASCT (BEAM-ASCT). Twenty of 57 (35%) TBC-ASCT patients had detectable viremia with human herpesvirus 6, cytomegalovirus, adenovirus, or BK virus, versus 9 of 79 (11%) BEAM-ASCT patients. Eight TBC-ASCT patients had clinically relevant viral infections (4 human herpesvirus 6, 2 cytomegalovirus, 1 adenovirus, 2 BK virus), versus 0 in the BEAM-ASCT group. Four TBC-ASCT patients suffered infections from either a fungal or parasitic pathogen versus 1 BEAM-ASCT patient. TBC was associated with greater risk of viral reactivation compared with BEAM, independent of other factors (hazard ratio, 4.42; 95% confidence interval, 1.9 to 11.3; P < .001). Prolonged lymphopenia and steroid use in the peri- and post-ASCT period did not explain these observed differences. The pathogenesis of these unusual infections in TBC-ASCT patients remains incompletely understood, and may involve more potent immune suppression with TBC conditioning. Clinicians should be aware of these differences in infection risk in TBC-ASCT patients, which more closely parallel those seen in allogenic hematopoietic cell transplantation recipients. New prophylactic approaches to help minimize these infections should be considered in this population.

Gut Microbiota Predict Pulmonary Infiltrates after Allogeneic Hematopoietic Cell Transplantation.

RATIONALE: Pulmonary complications (PCs) cause significant morbidity and mortality after allogeneic hematopoietic stem cell transplantation (HCT). Shifts in gut microbiota have been linked to HCT outcomes; however, their effect on PCs is unknown. OBJECTIVES: To investigate whether changes in gut microbiota are associated with PCs after HCT. METHODS: A single-center observational study was performed on 94 patients who underwent HCT from 2009 to 2011 and who were previously enrolled in a protocol for 16S ribosomal RNA sequencing of fecal microbiota. The primary endpoint, PC, was defined by new abnormal parenchymal findings on chest imaging in the setting of respiratory signs and/or symptoms. Outcomes were collected up to 40 months after transplant. Clinical and microbiota risk factors for PCs and mortality were evaluated using survival analysis. MEASUREMENTS AND MAIN RESULTS: One hundred twelve PCs occurred in 66 (70.2%) subjects. A high comorbidity index (hazard ratio [HR], 2.30; 95% confidence interval [CI], 1.30-4.00; P = 0.004), fluoroquinolones (HR, 2.29, 95% CI, 1.32-3.98; P = 0.003), low baseline diversity (HR, 2.63; 95% CI, 1.22-5.32; P = 0.015), and γ-proteobacteria domination of fecal microbiota (HR, 2.64; 95% CI, 1.10-5.65; P = 0.031), which included common respiratory pathogens, predicted PCs. In separate analyses, low baseline diversity was associated with PCs that occurred preengraftment (HR, 6.30; 95% CI, 1.42-31.80; P = 0.016), whereas γ-proteobacteria domination predicted PCs postengraftment (HR, 3.68; 95% CI, 1.49-8.21; P = 0.006) and overall mortality (HR, 3.52; 95% CI, 1.28-9.21; P = 0.016). Postengraftment PCs were also independent predictors of death (HR, 2.50; 95% CI, 1.25-5.22; P = 0.009). CONCLUSIONS: This is the first study to demonstrate prospective changes in gut microbiota associated with PCs after HCT. Postengraftment PCs and γ-proteobacteria domination were predictive of mortality. This suggests an adverse relationship between the graft and lung, which is perhaps mediated by bacterial composition in the gut. Further study is warranted.

The effects of intestinal tract bacterial diversity on mortality following allogeneic hematopoietic stem cell transplantation.

Highly diverse bacterial populations inhabit the gastrointestinal tract and modulate host inflammation and promote immune tolerance. In allogeneic hematopoietic stem cell transplantation (allo-HSCT), the gastrointestinal mucosa is damaged, and colonizing bacteria are impacted, leading to an impaired intestinal microbiota with reduced diversity. We examined the impact of intestinal diversity on subsequent mortality outcomes following transplantation. Fecal specimens were collected from 80 recipients of allo-HSCT at the time of stem cell engraftment. Bacterial 16S rRNA gene sequences were characterized, and microbial diversity was estimated using the inverse Simpson index. Subjects were classified into high, intermediate, and low diversity groups and assessed for differences in outcomes. Mortality outcomes were significantly worse in patients with lower intestinal diversity; overall survival at 3 years was 36%, 60%, and 67% for low, intermediate, and high diversity groups, respectively (P = .019, log-rank test). Low diversity showed a strong effect on mortality after multivariate adjustment for other clinical predictors (transplant related mortality: adjusted hazard ratio, 5.25; P = .014). In conclusion, the diversity of the intestinal microbiota at engraftment is an independent predictor of mortality in allo-HSCT recipients. These results indicate that the intestinal microbiota may be an important factor in the success or failure in allo-HSCT.

Factors Associated with Antimicrobial Use at the End-Of-Life Among Hospitalized Cancer Patients.

Background: Antimicrobials are frequently administered at end-of-life (EOL) and their non-beneficial use may subject patients to unnecessary harms. Studies analyzing factors for antimicrobial prescribing in solid tumor cancer patients at the EOL are lacking. Thus, we aimed to identify factors and patterns associated with antimicrobial use in hospitalized adults with cancer at EOL. Methods: We used a retrospective cohort design to review electronic medical records of terminal hospitalized patients ≥18 years with solid tumors admitted to non-intensive care units in a metropolitan comprehensive cancer center during 2019 and assessed antimicrobial use in the last 7 days of life. Results: Among 633 cancer patients, 59% (n = 376) received antimicrobials (AM+) within the last 7 days of life. AM + patients were older (P = .012), mostly of male gender (55%), and non-Hispanic ethnicity (87%). AM + patients were significantly more likely to have a foreign device, suspected signs of infection, neutropenia, positive blood culture result, documented advance directive; receive laboratory or radiologic testing, and a palliative care or infectious disease consultation (all P < .05). No statistically significant differences were observed in the presence of documented goals of care discussions, or EOL discussions/EOL care orders. Conclusion: Antimicrobial use at the EOL is common in solid tumor cancer patients at the EOL and is associated with increased utilization of invasive interventions. There is an opportunity for infectious disease specialists to build primary palliative care skills and partner with antimicrobial stewardship programs to better advise patients, decision makers, and primary teams on the use of antimicrobials at the EOL.

Penicillin Allergy Testing: An Outpatient Nurse-Driven Program for Patients With Cancer.

BACKGROUND: Penicillin allergy testing (PAT) can decrease the use of unnecessary antibiotics by clarifying who is truly allergic. OBJECTIVES: This article describes the development and implementation of an oncology outpatient nurse-driven PAT program. METHODS: A nurse-driven program, initiated with allergy screening at the first encounter, was designed to identify patients with oncologic diagnoses eligible for PAT. Once verified eligible, patients undergo a three-step testing process (scratch test, intradermal injection, and IV challenge dose) administered by the infusion nurse. FINDINGS: From November 2018 to December 2019, 82 outpatients with reported penicillin allergies were screened; 90% were eligible for PAT, and 97% of patients tested were negative for penicillin allergy. A significant reduction in aztreonam use among patients admitted for hematopoietic stem cell transplantation was also noted as compared to before PAT was offered.

Who to Test, When, and for What: Why Diagnostic Stewardship in Infectious Diseases Matters.

New rapid molecular diagnostic technologies for infectious diseases provide faster diagnostic test results and, if used correctly, will enable more rapid delivery of care to patients. This perspective piece outlines how this new technology can be used more effectively-with a focus on collaborative team approaches and tools clinicians and laboratorians can use to optimally affect patient care. This article also showcases a patient case, outlining problems with the diagnostic process as it currently stands, and poses potential strategies on how this process may be improved.

Monocyte Reconstitution and Gut Microbiota Composition after Hematopoietic Stem Cell Transplantation.

BACKGROUND: Monocytes are an essential cellular component of the innate immune system that support the host's effectiveness to combat a range of infectious pathogens. Hemopoietic cell transplantation (HCT) results in transient monocyte depletion, but the factors that regulate recovery of monocyte populations are not fully understood. In this study, we investigated whether the composition of the gastrointestinal microbiota is associated with the recovery of monocyte homeostasis after HCT. METHODS: We performed a single-center, prospective, pilot study of 18 recipients of either autologous or allogeneic HCT. Serial blood and stool samples were collected from each patient during their HCT hospitalization. Analysis of the gut microbiota was done using 16S rRNA gene sequencing, and flow cytometric analysis was used to characterize the phenotypic composition of monocyte populations. RESULTS: Dynamic fluctuations in monocyte reconstitution occurred after HCT, and large differences were observed in monocyte frequency among patients over time. Recovery of absolute monocyte counts and subsets showed significant variability across the heterogeneous transplant types and conditioning intensities; no relationship to the microbiota composition was observed in this small cohort. CONCLUSION: In this pilot study, a relationship between the microbiota composition and monocyte homeostasis could not be firmly established. However, we identify multivariate associations between clinical factors and monocyte reconstitution post-HCT. Our findings encourage further longitudinal surveillance of the intestinal microbiome and its link to immune reconstitution.

The Effect of Neutropenia and Filgrastim (G-CSF) in Cancer Patients With COVID-19 Infection.

BACKGROUND: Neutropenia is commonly encountered in cancer patients, and recombinant human granulocyte colony-stimulating factor (G-CSF, filgrastim) is widely given to oncology patients to counteract neutropenia and prevent infection. G-CSF is both a growth factor and cytokine that initiates proliferation and differentiation of mature granulocytes. However, the clinical impact of neutropenia and G-CSF use in cancer patients, who are also afflicted with coronavirus disease 2019 (COVID-19), remains unknown. METHODS: An observational cohort of 304 hospitalized patients with COVID-19 at Memorial Sloan Kettering Cancer Center was assembled to investigate links between concurrent neutropenia (N=55) and G-CSF administration (N=16) on COVID-19-associated respiratory failure and death. These factors were assessed as time-dependent predictors using an extended Cox model, controlling for age and underlying cancer diagnosis. To determine whether the degree of granulocyte response to G-CSF affected outcomes, a similar model was constructed with patients that received G-CSF, categorized into high- and low-response, based on the level of absolute neutrophil count (ANC) rise 24 hours after growth factor administration. RESULTS: Neutropenia (ANC < 1 K/mcL) during COVID-19 course was not independently associated with severe respiratory failure or death (HR: 0.71, 95% Cl: 0.34-1.50, P value: 0.367) in hospitalized COVID-19 patients. When controlling for neutropenia, G-CSF administration was associated with increased need for high oxygen supplementation and death (HR: 2.97, 95% CI: 1.06-8.28, P value: 0.038). This effect was predominantly seen in patients that exhibited a high response to G-CSF based on their ANC increase post-G-CSF administration (HR: 5.18, 95% CI: 1.61-16.64, P value: 0.006). CONCLUSION: Possible risks versus benefits of G-CSF administration should be weighed in neutropenic cancer patients with COVID-19 infection, as G-CSF may lead to worsening clinical and respiratory status in this setting.