[Safety and humoral immune responses of an inactivated whole-cell lysate of Mycobacterium tuberculosis B/R fusion strain prepared by combined ultrasonic disruption and enzymatic digestion].

Authors

Zhimin Pan, Zhixun Liu, Su Liang, Xiaomei Li, Xiling Deng, Jiangtao Dong, Jie Zhang, Xiaoling Liu, Le Zhang, Fang Wu, Wanjiang Zhang

Published in

Zhong nan da xue xue bao. Yi xue ban = Journal of Central South University. Medical sciences. Volume 51. Issue 8. Pages 1677-1687. Aug 28, 2026.

Abstract

Tuberculosis remains the leading cause of death from a single infectious disease. Because currently available vaccines provide limited protection, the development of novel tuberculosis vaccines with favorable safety and high efficacy remains necessary. An inactivated whole-cell lysate of Mycobacterium tuberculosis B/R fusion strain prepared by combined ultrasonic disruption and enzymatic digestion (UK-B/R) retains key antigenic components while ensuring complete bacterial inactivation; however, its safety and immunogenicity have not been fully characterized. This study aims to evaluate the safety of UK-B/R and the humoral immune responses induced by UK-B/R.
In the cell experiments, murine monocyte/macrophage leukemia RAW264.7 cells were divided into a blank control (control) group, a BCG group, a B/R group, and a UK-B/R group. After 24 h of treatment, the levels of interleukin-1β (IL-1β) and interleukin-6 (IL-6) in the cell culture supernatants were measured using enzyme-linked immunosorbent assay (ELISA), and the apoptotic rate was determined by flow cytometry. In the animal experiments, 6-8-week-old C57BL/6J mice were randomly assigned to the phosphate-buffered saline (PBS), BCG, B/R, and UK-B/R groups for acute and long-term toxicity studies. In the acute toxicity study, mice in each group received a single subcutaneous administration and were observed continuously for 14 days. General condition, changes in body weight, mortality, and other parameters were recorded. In the long-term toxicity study, mice in each group were immunized subcutaneously on days 0, 14, and 28. Serum and lung, liver, spleen, and kidney tissues were collected on day 3 (acute phase) and day 14 (recovery phase) after the final immunization. Organ indices were calculated, and levels of alanine aminotransferase (ALT), aspartate aminotransferase (AST), albumin (ALB), serum creatinine (SCr), and blood urea nitrogen (BUN) were measured. Hematoxylin and eosin staining was performed to assess histopathological changes in major organs. In addition, 15 female C57BL/6J mice aged 6 to 8 weeks were randomly assigned to the PBS, BCG, and UK-B/R groups. On day 14 after the final subcutaneous immunization, antigen-specific antibody levels in serum and bronchoalveolar lavage fluid (BALF) were measured by ELISA.
IL-1β and IL-6 levels in the cell culture supernatants were significantly higher in the UK-B/R group than in the control group (both P<0.05). IL-1β levels did not differ significantly between the UK-B/R group and either the BCG or B/R group (both P>0.05), whereas IL-6 levels were significantly lower in the UK-B/R group than in the BCG and B/R groups (both P<0.05). The apoptotic rate did not differ significantly between the UK-B/R and control groups (P>0.05). In the acute toxicity study, no abnormal reactions or deaths occurred in any group. Body weight showed an increasing trend in all groups, with no significant between-group differences (P>0.05). In the long-term toxicity study, no significant differences were observed among the groups in the organ indices of the lung, liver, spleen, and kidney or in ALT, AST, ALB, SCr, and BUN levels (all P>0.05). Histopathological examination revealed no obvious pathological changes in the lung, liver, spleen, or kidney tissues of mice in any group. Immunological evaluation showed that serum antigen-specific IgG antibody levels were significantly higher in the UK-B/R group than in the PBS and BCG groups. Antigen-specific IgG and IgA antibody levels in BALF were also significantly higher in the UK-B/R group than in the PBS and BCG groups (all P<0.05).
UK-B/R demonstrated favorable safety profiles at both the cellular and animal levels and induced antigen-specific humoral and mucosal immune responses.

PMID:
42935198
Bibliographic data and abstract were imported from PubMed on 27 Oct 2026.

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