PI-07. Detection frequency of herpesviruses in colonic mucosal biopsies in the patients with intestinal complications after hematopoietic stem cell transplantation

Summary

Intestinal syndromes are common after allogeneic HSCT, due to acute graft-versus-host disease (aGVHD) and/or infectious conditions. Later on, they may manifest as overlap syndrome combining the features of acute and chronic GVHD. Early reactivation of herpesviruses is a common finding after intensive cytostatic therapy and HSCT. The aim of our study was to assess detection frequency of cytomegalovirus (CMV), Epstein-Barr virus (EBV), human herpesvirus type 6 (HHV6) and herpes simplex virus (HSV) in colonic mucosal biopsies within first 180 days post-HSCT, as well as their possible association with common clinical complications.

Materials and methods

Our study group included 119 patients (1 to 72 years old) admitted to the R. Gorbacheva Research Institute for allo-HSCT from 2014 to 2020. Most patients were treated for acute myeloid leukemia (n=34), acute lymphoblastic leukemia (n=36), Hodgkin’s disease (n=10), severe aplastic anemias (n=15). The patients were subjected to haploidentical related (48%), allogeneic unrelated (41%), or allogeneic related HSCT (11%). Bone marrow or peripheral blood stem cells were transplanted in, resp., 42 and 58% of cases. Myeloablative conditioning was applied in 57% of cases. A total of 155 diagnostic forceps biopsies of colonic mucosa were taken during diagnostic fibrocolonoscopy in the patients with intestinal syndromes. The endoscopy was made in severe therapy-resistant intestinal syndromes. Intestinal GVHD or local infections were assessed by means of clinical criteria and biopsy histology. Most biopsies were taken from descending and sigmoid colon (52%) followed by transverse colon (25%), ascending colon (10%), caecum (5%), ileum (5%). All patients or their guardians have given their informed consent for medical procedures (HSCT and endoscopy). The samples of mucosa (3 to 6 specimens) were studied by standard histology with immunoassays for some viral antigens. DNA from colonic mucosa was monitored for EBV, CMV, HSV, and HHV type 6 A/B by means of commercial PCR test systems. The results were considered positive or negative, at a sensitivity of 400-1000 gene copies/mL (depending on the virus type). Statistical evaluation was performed by Statistica 10 software, using both parametric and non-parametric criteria.

Results

Positive HSV findings in colon mucosa were infrequent (up to 8% at 2-3 months post-transplant). High HHV6 incidence (a mean of 62%) was revealed over 6 months, whereas CMV reactivation was less common in mucosal biopsies (28-35%) within 4 months post-transplant. EBV incidence exhibited a significant increase, especially, at later terms (until 5-6 months post-HSCT). In available time-matched blood/biopsy pairs, the HHV6 detection rates in colon mucosa was sufficiently higher than in blood samples (resp., 59% and 18%, p<0.04). The CMV and EBV detection rates were similar in colon and blood samples. A significant correlation was found between blood and colon positivity for both CMV and EBV (r=0.489 and r=0.583; p<0.05). Looking for possible associations between positive viral findings in mucosal biopsies and patient characteristics, we did not reveal any significant correlations with most demographic and clinical features of the patients, including age, gender or primary diagnosis of the patients. However, we have revealed significant associations between EBV incidence and some post-transplant outcomes. E.g., higher EBV detection rates in colonic mucosa correlated with prolonged bone marrow engraftment in terms of delayed leukocyte and platelet recovery. Moreover, increased frequency of EBV-positive colonic biopsies was found in deceased patients with intestinal syndromes (resp., 56% versus 21%, p=0.02).

Conclusion

Significant correlation between EBV incidence in blood and gut biopsies suggests some relations between systemic and local EBV reactivation. Moreover, post-transplant hematopoietic reconstitution seems to be associated with local EBV reactivation, thus confirming a special role of EBV in post-transplant complications within 6 months post-transplant.

The study was supported by the Russian Science Foundation (Grant No. 22-15-00149 of 18.05.2022).

Keywords

Hematopoietic stem cell transplantation, colonic mucosa, biopsies, herpesviruses, detection rates, clinical associations.