Impact of Sepsis and Stress Hematopoiesis on the Acquisition and Persistence of Clonal Hematopoiesis

*O.O and T.K are co-first authors

While various conditions contribute to the acquisition of clonal hematopoiesis (CH) such as chemotherapy and germline predisposition, CH of indeterminate potential (CHIP) has mostly been attributed to age-related factors. Aging in chronologic sense is also associated with a greater chance of manifesting recurrent events of infection, inciting stress hematopoiesis but the quantity (number of episodes) and quality (severity) is difficult to capture. Here we hypothesize that sepsis, as a marker of infectious emergency hematopoiesis, can be experimentally exploited to determine whether clinical and subclinical events of hematopoietic proliferative capacity contribute to the emergency of CH.

To strengthen the hypothesis, we first conducted an exploratory analysis of publicly available resources. We examined pathogenic CHIP variants (variant allele frequency [VAF] ≥ 2%) of 63 canonical myeloid genes in patients with sepsis leveraging whole genome sequencing (WGS) data from the All of Us NIH Research Program (N=245,388). Among 6,258 participants with the diagnosis of sepsis, we reviewed clinical parameters and molecular features of 565 individuals (median age 57, IQR 22-68) without a history of malignancy who had WGS performed within 30 days from leukocytosis (>11 K/uL) onset. Overall, the frequency of CH was 36% vs 4.8% in controls (n=98 560; p<.00001).

With this supporting evidence we have conducted an observational multicenter study by prospectively accruing ICU admitted patients with sepsis and leukocytosis (N=78) excluding individuals with prior malignancy. In this confirmatory cohort, the median age was 70 years (IQR 61-77), median WBC was 18K/uL (IQR 16-21) and median ANC was 16 K/uL (IQR: 12-20). Sampling for deep targeted NGS occurred at a median of 3 days (IQR 1-5) after leukocytosis onset. Using the same set of myeloid genes, 47% of patients harbored CH. The most frequent somatic variants included DNMT3A (median %VAF 17), TET2 (median % VAF 43) and ASXL1 (median % VAF 45). As expected, baseline demographic factors associated with higher CHIP prevalence included older age with 29% in the age category 30-49, 49% in 50-69, and 51% in patients aged ≥70 years, as well as history of smoking (p=0.003). Notably, bacterial infections, which has a neutrophil predominance, conferred a higher risk of having CH (CHIP +ve) (RR: 1.7 [CI 1.06-2.73], p=0.03). CHIP prevalence, however, did not correlate with degree of leukocytosis or ANC.

We then performed a longitudinal analysis of the impact of CHIP on ICU outcomes by using multivariate logistic regression accounting for demographics, mutation type and sequential organ failure assessment (SOFA) score during ICU admission. This latter score is generally used to assess degree of organ dysfunction scored from 0 (no organ dysfunction) to 4 (severe organ dysfunction) for six organ systems. We found that CH was associated with higher incidence of organ dysfunction at end of ICU admission (p=0.0001). Specifically, DNMT3A mutations conferred a higher risk of diagnosis of overt septic shock (log OR= 2.4, 95%CI 0.19-5.4, p<0.05) with worse cardiovascular SOFA sub scores compared to CHIP-ve patients (median score 4 vs 1, p=0.02).

At median follow up of 18 months, ICU CHIP +ve patients had higher rates of new onset cytopenia (30% vs 7%, p= 0.01), namely CCUS, which was sustained by anemia in majority of cases (88%). Clonal evolution was examined in 6 longitudinal blood samples after leukocytosis resolution at a median follow up of 18.3 (IQR 17-20) months. In 2/6 patients CH persisted with decreased clonal burden. In 1 patient, additional clonal mutations, such as DNMT3A (VAF 5.7%) and ASXL1 (VAF 2.7%) emerged.

In summary, our results suggest that sepsis, here used as example of stress hematopoiesis, can contribute to acquisition of CH and impact on outcomes in a critical care setting. Thus, recurrent infectious episodes can quantitatively (number of episodes, time factor) or qualitatively (severity) lead to increased risk of CHIP. We stipulate that reducing infections that lead to sepsis may decrease the ‘opportunities’ for emergence of CH.

We gratefully acknowledge All of Us participants for their contributions, without whom this research would not have been possible. We also thank the National Institutes of Health's All of Us Research Program for making available the participant data [and/or samples and/or cohort] examined in this study

No relevant conflicts of interest to declare.