A total of 100 untreated new leprosy patients were recruited prospectively and examined for the presence of phenolic glycolipid I (PGL-I) antigen in their serum specimens by dot enzyme-linked immunosorbent assay (ELISA) using rabbit anti-PGL-I antiserum. The presence of circulating PGL-I antigen was closely related to the bacterial indices (BI) of the patients. The PGL-I antigen was detectable in 27 (93.1%) of 29 patients with a BI of 4.0 or above and in 15 (68.2%) of 22 patients with a BI of 3.0 to 3.9. However, none of the 37 patients with a BI of less than 1.9 had detectable PGL-I antigen by the methods used in this study. The level of PGL-I in serum declined rapidly by about 90% 1 month after the start of multidrug therapy. This study showed clearly that anti-PGL-I IgM antibodies and circulating PGL-I antigen levels reflect the bacterial loads in untreated leprosy patients. The serological parameters based on the PGL-I antigen may therefore be useful in the assessment of leprosy patients at the time of diagnosis and possibly in monitoring patients following chemotherapy.

SummaryLittle information is available regarding changes in immune status for patients with Mycobacterium avium complex (MAC) lung disease during antibiotic therapy. Serum immunomolecules from 42 patients with MAC lung disease were assayed comparatively using an array-based system according to (i) patients with MAC lung disease at the time of diagnosis versus healthy controls and (ii) alterations after 12 months of antibiotic therapy in the MAC lung disease group. In addition, cytokine analyses were performed to determine whether cytokine responses were associated specifically with the disease phenotype, treatment outcome and aetiological agent. Notably, the serum concentrations of type 1 cytokine-associated molecules, such as CD40L, interferon (IFN)-γ, interleukin (IL)-8 and IL-23, were decreased significantly in patients at the time of diagnosis, suggesting that these molecules may serve as indicators of host susceptibility to MAC disease. Although the overall serum level of T helper type 1 (Th1)-related molecules, such as CD40L and IFN-γ, was restored after treatment, Th17-related cytokines, such as IL-17 and IL-23, were down-regulated significantly at 12 months posttreatment compared to pretreatment. Furthermore, these cytokine patterns differed among patient subgroups. Decreased serum concentrations of IL-17 and/or IL-23 were associated with failure of sputum conversion, the fibrocavitary disease phenotype and M. intracellulare lung disease. Thus, the reciprocal balance between Th1 and Th17 immunity during antibiotic therapy for MAC lung disease is critical for dictating the treatment response. In conclusion, a low level of Th1-related immunomolecules may perpetuate MAC lung disease, and the serum concentrations of Th17-related cytokines can reflect the treatment outcome, disease phenotype and aetiological agent.

The development of clinically relevant biomarkers is important for diagnosing latent tuberculosis infection (LTBI) and active tuberculosis (TB) and predicting their prognoses. This study examined whether the responses of multiple cytokines can be used as a biomarker to distinguish the TB infection status and mycobacterial load. We analysed the responses of multiple cytokines (IFN-c, IL-2, IL-10, IL-13, IL-17 and TNF-a) in the supernatant from the QuantiFERON-TB Gold In-Tube assay following stimulation of whole blood from the TB group (n = 32), LTBI group (n = 19) and healthy controls (n = 30) with TB antigens (ESAT-6, CFP-10 and TB7.7). The median responses of IFN-c, IL-2, IL-10 and IL-13 were higher in the LTBI and active TB groups than in the non-TB control group (IFN-c, P < 0.001; IL-2, P < 0.001; IL-10, P = 0.012; IL-13, P < 0.001). The median IL-2/IFN-c ratio of the LTBI group was higher than that of the active TB group (P = 0.014) and differed significantly between patients with LTBI, patients with smear-negative TB and patients with smearpositive TB (P = 0.027). This difference was especially evident between the patients with LTBI and patients with smear-positive TB (P = 0.047). In conclusion, IFN-c, IL-2, IL-10 and IL-13 can serve as biomarkers for distinguishing TB infection. In addition, the IL-2/IFN-c ratio appears to be a biomarker for diagnosing LTBI and may be useful as a prognostic factor and for evaluating treatment responses.

Novel immunogenic antigens are continually required for the improvement of diagnostic techniques for Mycobacterium tuberculosis infection. Some proteins with serodiagnostic value are not expressed under normal culture conditions, but may be induced under specific conditions such as gradual oxygen depletion and low pH, and from inside macrophages. Using a customized amplification library, we previously found that Rv2041c from M. tuberculosis H37Rv was highly expressed in vitro under conditions of low pH and hypoxia. In this study, recombinant (r)Rv2041c was produced in Escherichia coli to examine its role in immune responses. Increased Rv2041c expression in vitro during dormancy and during infection in human macrophages was confirmed by Western blotting and reverse transcription polymerase chain reaction, respectively. Interestingly, positive antibody responses to rRv2041c were detected only in those patients with active tuberculosis (TB) and in mice infected with M. tuberculosis H37Rv. Finally, Rv2041c was used successfully in the serodiagnosis of active M. tuberculosis infection in Korean patients in conjunction with other M. tuberculosis proteins, including Ag85 complex, 38 kDa, rESAT‐6, rHSP‐X and rCFP‐10. Our Rv2041c–ELISA had comparable diagnostic sensitivity and equivalent specificity to the use of an M. tuberculosis H37Rv cellular extract. In addition, seven of 46 serum samples collected from TB patients (15.28%) showed positive antibody responses to Rv2041c, but not to the other proteins. These results suggest that Rv2041c can be used to increase assay sensitivity alongside well‐known antigens for the serodiagnosis of M. tuberculosis infection.

Agglutinating antibodies to neuraminidase-treated red blood cells (anti-T agglutinins) are known to be reduced in patients with gastric cancer. The antigenic determinant of anti-T agglutinin is known to have a disaccharide structure [Gal(beta1-3)GalNAc], the same specificity as peanut agglutinin (PNA). We examined sera of 27 patients with gastric cancer and 30 controls for anti-T agglutinins, anti-T antibodies and PNA-binding glycoproteins. Anti-T agglutinins were titrated by a microtiter hemagglutination method. Levels of anti-T antibodies were determined by enzyme immunoassay using synthetic glycoconjugate [Gal(beta1-3)GalNAc O-alpha-linked to human serum albumin] as an antigen. Levels of PNA-binding glycoproteins in sera were measured by sandwich enzyme-linked lectin assay using wheat germ agglutinin and peroxidase-conjugated PNA. Titers of anti-T agglutinins were significantly lower in patients with gastric cancer than in controls (P = 0.041). Levels of anti-T antibodies were not significantly different in patients with gastric cancer and controls; however, decreased levels of anti-T antibodies were more frequent in patients with gastric cancer than in controls (P = 0. 001). Levels of PNA-binding glycoproteins were significantly higher in sera of patients with gastric cancer than in controls (P = 0.001). The levels of anti-T antibodies inversely correlated with the levels of PNA-binding glycoproteins in sera of patients with gastric cancer (r = -0.44, P = 0.021). These results suggest that the decrease in anti-T antibodies in sera of patients with gastric cancer might be due to immune complex formation between circulating PNA-binding glycoproteins and anti-T antibodies.