Age-specific predictors of disease severity in children with respiratory syncytial virus infection beyond infancy and through the first 5 years of age

BACKGROUND

Respiratory syncytial virus (RSV) infection is associated with significant morbidity in infants. Risk factors for severe disease beyond the first 2 years of life have not been fully defined.

METHODS

Children <5 years hospitalized with virologically confirmed RSV infection were identified over six respiratory seasons (10/2012-4/2018) and their medical records manually reviewed. Multivariable analyses were performed to define the age-specific (<6, 6-24, and >24-59 months) risk factors associated with oxygen administration, PICU admission, mechanical ventilation, and duration of hospitalization.

RESULTS

We identified 5143 children hospitalized with RSV infection: 53.5% (n = 2749) <6 months; 31.7% (n = 1631) 6-24 months; and 14.8% (n = 763) >24-59 months. Rates of ICU admission were high (35%-36%) and comparable across age groups, while children >24-59 and 6-24 versus those <6 months required supplemental oxygen more frequently (73%; 71%; 68%, respectively; p = .003). The presence of comorbidities increased with age (25%, <6 months; 46%, 6-24 months; 70%, >24-59 months; p < .001). Specifically, neuromuscular disorders, chronic lung disease, and reactive airway disease/asthma were predictive of worse clinical outcomes in children aged 6-24 and >24-59 months, while RSV-viral codetections increased the risk of severe outcomes in children aged <6 and 6-24 months of age.

CONCLUSIONS

Almost half of children hospitalized with RSV infection were >6 months. Underlying comorbidities increased with age and remained associated with severe disease in older children, while RSV-viral codetections were predictive of worse clinical outcomes in the youngest age groups. These data suggest the importance of defining the clinical phenotype associated with severe RSV according to age, and the persistent burden associated with RSV beyond infancy.

Abstract 2100: Dendritic cell-intrinsic PTPN22 negatively regulates anti-tumor immunity

Checkpoint blockade immunotherapies have revolutionized cancer treatment; however, only a subset of patients benefit. Individuals with a loss-of-function single nucleotide polymorphism (SNP) in the gene encoding tyrosine-protein phosphatase non-receptor type 22 (PTPN22) are at increased risk for autoimmune disease and display a lower incidence of certain cancers. Studies in PTPN22 knockout (KO) mice have established it as a negative regulator of T cell responses in autoimmune and cancer models attributed to a hyperactive T cell response. However, these studies have not defined the cell lineage-intrinsic roles of PTPNN22 in distinct immune cell compartments, and the potential role of PTPN22 in myeloid cells remains undefined. Myeloid cells in general, and dendritic cells specifically, are critical modulators of antitumor T cell responses. We have developed a novel dendritic cell (DC) PTPN22 conditional KO (cKO) mouse model that enables deletion in CD11c+ cells. Deletion of PTPN22 in DCs resulted in augmented tumor control, evidenced by a significant reduction in tumor burden at endpoint. We found that at end point total CD8+ T cells, but not CD4+ T cells or Tregs, were increased in the tumors of CD11c+ PTPN22 cKO mice compared to control mice. The use of the syngeneic murine melanoma cell line B16.F10 expressing the model antigen “SIY” (B16.SIY) allowed for the tracking of endogenous tumor antigen-specific T cell responses. Indeed, CD8+ T cells demonstrated increased expression of both activation and memory markers at day 10 in the tumor draining lymph node (tdLN) and in day 27 tumor infiltrating lymphocytes. Depletion of CD8+ T cells with an anti-CD8β monoclonal antibody eliminated the tumor growth control in this model, suggesting a mechanism of action based on the DC-CD8+ T cell axis. To test precisely for increased antigen-specific T cell priming, we utilized IFN-γ ELISpot analysis on the tdLN and spleen of tumor bearing mice. We found an increased frequency of IFN-γ-producing T cells in the presence of tumor antigen SIY, but not irrelevant control antigen SIINFKL. Spectral analysis of tumor antigen-specific T cells in the tdLN at the same timepoint showed a significant increase in the number and percentage of CD8+ SIY+ T cells displaying elevated activation and memory markers. Lastly, analysis of DCs in the tdLN similarly revealed an increase in the quantity and percentage of DCs attributed to an increase of CD103+ DCs, but not CD11b+ DCs, displaying increased activation and proliferation markers. Thus, we show that deletion of PTPN22 in DCs is sufficient to drive a tumor antigen-specific T cell response resulting in enhanced tumor control. This work highlights the potential to modulate anti-tumor immunity through the manipulation of DCs.

Citation Format: Santiago Acero-Bedoya, Emily F. Higgs, Thomas F. Gajewski. Dendritic cell-intrinsic PTPN22 negatively regulates anti-tumor immunity [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 2100.

Immune profiles provide insights into respiratory syncytial virus disease severity in young children

Respiratory syncytial virus (RSV) is associated with major morbidity in infants, although most cases result in mild disease. The pathogenesis of the disease is incompletely understood, especially the determining factors of disease severity. A better characterization of these factors may help with development of RSV vaccines and antivirals. Hence, identification of a "safe and protective" immunoprofile induced by natural RSV infection could be used as a as a surrogate of ideal vaccine-elicited responses in future clinical trials. In this study, we integrated blood transcriptional and cell immune profiling, RSV loads, and clinical data to identify factors associated with a mild disease phenotype in a cohort of 190 children <2 years of age. Children with mild disease (outpatients) showed higher RSV loads, greater induction of interferon (IFN) and plasma cell genes, and decreased expression of inflammation and neutrophil genes versus children with severe disease (inpatients). Additionally, only infants with severe disease had increased numbers of HLA-DR^low monocytes, not present in outpatients. Multivariable analyses confirmed that IFN overexpression was associated with decreased odds of hospitalization, whereas increased numbers of HLA-DR^low monocytes were associated with increased risk of hospitalization. These findings suggest that robust innate immune responses are associated with mild RSV infection in infants.

Abrupt involution induces inflammation, estrogenic signaling, and hyperplasia linking lack of breastfeeding with increased risk of breast cancer

Background

A large collaborative analysis of data from 47 epidemiological studies concluded that longer duration of breastfeeding reduces the risk of developing breast cancer. Despite the strong epidemiological evidence, the molecular mechanisms linking prolonged breastfeeding to decreased risk of breast cancer remain poorly understood.

Methods

We modeled two types of breastfeeding behaviors in wild type FVB/N mice: (1) normal or gradual involution of breast tissue following prolonged breastfeeding and (2) forced or abrupt involution following short-term breastfeeding. To accomplish this, pups were gradually weaned between 28 and 31 days (gradual involution) or abruptly at 7 days postpartum (abrupt involution). Mammary glands were examined for histological changes, proliferation, and inflammatory markers by immunohistochemistry. Fluorescence-activated cell sorting was used to quantify mammary epithelial subpopulations. Gene set enrichment analysis was used to analyze gene expression data from mouse mammary luminal progenitor cells. Similar analysis was done using gene expression data generated from human breast samples obtained from parous women enrolled on a tissue collection study, OSU-2011C0094, and were undergoing reduction mammoplasty without history of breast cancer.

Results

Mammary glands from mice that underwent abrupt involution exhibited denser stroma, altered collagen composition, higher inflammation and proliferation, increased estrogen receptor α and progesterone receptor expression compared to those that underwent gradual involution. Importantly, when aged to 4 months postpartum, mice that were in the abrupt involution cohort developed ductal hyperplasia and squamous metaplasia. Abrupt involution also resulted in a significant expansion of the luminal progenitor cell compartment associated with enrichment of Notch and estrogen signaling pathway genes. Breast tissues obtained from healthy women who breastfed for < 6 months vs ≥ 6 months showed significant enrichment of Notch signaling pathway genes, along with a trend for enrichment for luminal progenitor gene signature similar to what is observed in BRCA1 mutation carriers and basal-like breast tumors.

Conclusions

We report here for the first time that forced or abrupt involution of the mammary glands following pregnancy and lack of breastfeeding results in expansion of luminal progenitor cells, higher inflammation, proliferation, and ductal hyperplasia, a known risk factor for developing breast cancer.

Electronic supplementary material

The online version of this article (10.1186/s13058-019-1163-7) contains supplementary material, which is available to authorized users.

Recent Trends in RSV Immunoprophylaxis: Clinical Implications for the Infant

Respiratory syncytial virus (RSV) remains the leading cause for hospitalizations in infants worldwide, resulting in significant health and financial burden. Since 1998, the humanized monoclonal antibody palivizumab remains the only available option licensed for the prevention of severe RSV disease in high-risk children, namely premature infants and those with chronic lung disease and congenital heart disease. In 2014, the American Academy of Pediatrics modified the recommendations on the use of RSV prophylaxis in these high-risk children, and limited its use to premature infants born at < 28 weeks' gestational age (wGA). Following this last guidance update, studies have confirmed that premature infants of 29 to 34 wGA remain at high risk for severe RSV disease, especially those of younger chronologic age. New and more cost-effective strategies are being developed that would help alleviate both the health and financial burden associated with severe RSV disease.