Research on the occurrence of Mycobacterium tuberculosis antigens in the circulating immune complexes, isolated from serum of patients with tuberculosis

Mycobacterium tuberculosis Cell Wall Antigens Induce the Formation of Immune Complexes and the Development of Vasculitis in an Experimental Murine Model

Tuberculosis (TB) of the central nervous system (CNS) presents high mortality due to brain damage and inflammation events. The formation and deposition of immune complexes (ICs) in the brain microvasculature during Mycobacterium tuberculosis (Mtb) infection are crucial for its pathobiology. The relevance of ICs to Mtb antigens in the pathogenesis of CNS-TB has been poorly explored. Here, we aimed to establish a murine experimental model of ICs-mediated brain vasculitis induced by cell wall antigens of Mtb. We administered a cell wall extract of the prototype pathogenic Mtb strain H37Rv to male BALB/c mice by subcutaneous and intravenous routes. Serum concentration and deposition of ICs onto blood vessels were determined by polyethylene glycol precipitation, ELISA, and immunofluorescence. Histopathological changes in the brain, lung, spleen, liver, and kidney were evaluated by hematoxylin and eosin staining. Our results evidenced that vasculitis developed in the studied tissues. High serum levels of ICs and vascular deposition were evident in the brain, lung, and kidneys early after the last cell wall antigen administration. Cell wall Mtb antigens induce strong type III hypersensitivity reactions and the development of systemic vasculitis with brain vascular changes and meningitis, supporting a role for ICs in the pathogenesis of TB.

A proteomics-based method for identifying antigens within immune complexes

A novel approach to recover and identify immune complexes (ICs) was developed using size exclusion chromatography (SEC) and affinity chromatography on immunoglobulin binding columns (HiTrap Protein G). The purification process was monitored by 1D SDS-PAGE, protein staining, Western blotting and, finally, liquid chromatography tandem mass spectrometry (LC MS/MS) was used to identify the recovered antigens. This approach was applied to serum with artificially created immune complexes (ICs) comprising vaccine antigen (influenza) and antibody, which led to recovery and identification of influenza peptides within the recovered ICs. This approach was compared with the established method for IC detection and recovery, polyethylene glycol (PEG) precipitation, followed by LC MS/MS. Both approaches successfully enabled capture, recovery and characterization of immunoglobulins and influenza antigen(s) in complex with the immunoglobulins. However, PEG precipitation has the advantage of simplicity and is more suited for large scale studies.

Circulating Immune Complexes and Heat Shock Protein 70 in the Sera of Patients with Sudden Sensorineural Hearing Loss

OBJECTIVES

The aim of this paper is to analyze and assess the usefulness of heat shock protein 70 (Hsp70) and circulating immune complexes (CIC) in patients with sudden sensorineural hearing loss (SSHL) in a tertiary care hospital in a research university (2014-2017).

MATERIALS AND METHODS

Patients were interviewed about the history of diseases; underwent an ear, nose, and throat (ENT) examination; a hearing test; and were analyzed for the presence of CIC and Hsp70 protein. A simple dot blot method was designed for the purpose of identification of Hsp70 bound to CIC and free Hsp70.

RESULTS

In 59.4% of patients with idiopathic SSHL, elevated levels of immune complexes were observed. Compared with healthy subjects, a significant difference was noted (p=0.00016). Positive reactions to the presence of free Hsp70 protein were noted in the sera of 48.4% of patients. In the control group, free Hsp70 was observed in 8% of patients (p=0.0000034). Hsp70 bound to CIC was detected in the sera of 62.5% of patients; and in healthy cases, in 12% (p<0.0001).

CONCLUSION

In the sera of persons with SSHL, there are elevated levels of CIC and Hsp70. After the application of the innovative method for determining the occurrence of Hsp70 bound to CIC, it was stated that its presence is greater than that of free Hsp70, commonly detected by means of the Western-blot method. The dot blot method applied in the present study increases the Hsp70 identification and by the same token increases the probability of detection of autoimmunological background of SSHL.

Protective effect of antigen excess immune complex in guinea pigs infected with Mycobacterium tuberculosis

Background & objectives:

Immune complexes (ICs) play a crucial role which can either be beneficial or pathological to the host. Involvement of circulating immune complexes (CICs) has been shown in tuberculosis (TB) cases (adults and neonates form), but its immunomodulatory effect has not been studied in vivo. Hence, this study was carried out to understand and explore the prognostic therapeutic potential of CICs on the host immune system in guinea pigs animal TB model.

Methods:

In this study, the guinea pigs (group I) were immunized with in vitro synthesized antigen excess IC (AgX-IC), group II with antibody excess IC (AbX-IC) and group III with phosphate-buffered saline. All these animals were sensitized with Mycobacterium tuberculosis H37Rv before immunization and subsequently infected with M. tuberculosis H37Rv strain post-immunization with IC.

Results:

Mortality was observed in animals belonging of groups II and III, while all animals in group I survived. A steady increase in the body weight of animals immunized with AgX-IC was observed when compared to the other groups. The infection load in the spleen and lungs was less in animals from group I when compared to the other groups. The CICs were found to be in higher concentration in serum of IC-immunized guinea pigs when compared to ICs non-immunized animals.

Interpretation & conclusions:

Based on our findings, it can be speculated that the ICs may have a protective immunomodulatory role pertaining to disease progression and development of pathology. As a new perspective, with further insight into the underlying mechanism of action and correlation with clinical data, ICs may also be used as a potential tool for assessing the immune status of the infected individuals, especially the close contacts of TB patients.