Serological biomarker screening and host factor analysis elucidating immune response heterogeneity in active pulmonary tuberculosis

ABSTRACT

While mortality and morbidity from pulmonary tuberculosis (PTB) have improved, diagnosis of this infectious disease remains suboptimal without a point-of-care test. Antibody/ antigen-based serodiagnostics is the most amenable for point-of-care translation but hampered by a lack of validated biomarkers and a heterogeneous patient antibody response. Using a case-control design, we assessed serodiagnostic potential of immunoglobulins G, A, and dimeric IgA responses against 18 antigenic preparations, followed by antibody-subclass responses against antigen 60 (A60), and four markers of host innate immunity by enzymelinked immunoassay using sera samples (n=110) collected from April to October 2007 in VietNam from human immunodeficiency-negative patients with provisional diagnosis of PTB. We further analyzed host variables to investigate factors driving biomarker heterogeneity observed in patients. Among active pulmonary tuberculosis patients, low correlation was observed between anti-A60 antibody-classes, and between anti-A60 immunoglobulin G subclasses, but anti-A60 immunoglobulin A subclasses were significantly correlated. The best diagnostic combination of anti-A60 immunoglobulin G/A and a C-reactive protein “ruleout” remains insufficient at 82%/92% sensitivity/specificity (95%CI 72-92%/82-98%). Heterogeneity of anti-A60 immunoglobulins G2, G3, M, as well as C-reactive protein and serum amyloid A levels observed in this study population appeared to be significantly associated with history of previous tuberculosis, hemoptysis, age, vaccination, night sweats, smoking, chest pain, fever, alcohol, and solid culture count. Further research on tuberculosis serological biomarkers may require consideration of host factors and new approaches using multiple biomarkers.