A significant therapeutic effect of immunoglobulins administered alone, or in combination with conventional chemotherapy, in experimental pulmonary tuberculosis caused by drug-sensitive or drug-resistant strains

Comprehensive insights into tuberculosis-associated hemophagocytic lymphohistiocytosis: a systematic review

BACKGROUND

Tuberculosis-associated hemophagocytic lymphohistiocytosis (TB-HLH) presents significant challenges in diagnosis and treatment due to its complex interplay between TB and HLH. This systematic review aims to provide comprehensive insights into the epidemiology, clinical characteristics, and treatment outcomes of TB-HLH patients.

METHODS

We performed a systematic review following Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, searching PubMed, Scopus, Web of Science, and Embase up to May 16, 2023, without language restrictions. We included case reports and cases series on patients with both TB and HLH with documented treatment outcomes. Data were analyzed using descriptive statistics, chi-square or Fisher's exact tests, t-tests, and mortality rates. Significant variables (p < 0.05) from univariate analysis and clinically relevant factors were used in binary logistic regression to determine odds ratios, 95% confidence intervals, and p-values.

RESULTS

A total of 185 articles involving 213 patients were included. The overall mortality rate was 39%. Age ≥ 44 years and comorbidities were identified as independent risk factors for increased mortality (p = 0.005). Anti-tuberculosis treatment (ATT) combined with HLH-specific therapies, was associated with reduced mortality compared to ATT alone (p < 0.05), especially IVIG (p = 0.04).

CONCLUSION

Integrating ATT with HLH-specific therapies significantly enhances survival in TB-HLH patients. Additionally, IVIG plays a key role in improving outcomes. Age ≥ 44 years and comorbidities are critical risk factors for increased mortality. Early and high suspicion of TB-HLH is essential, especially in high TB burden regions or recent travel contexts. Future research should focus on prospective multicenter studies to validate our findings and develop standardized treatment strategies on TB-HLH.

PROSPERO

CRD42022364180.

In vitro evaluation of human intravenous immunoglobulin in combination with antimicrobials and human serum against multidrug-resistant isolates of Acinetobacter baumannii

The high incidence of multidrug-resistant (MDR) Acinetobacter baumannii has been a challenge for health worldwide, due to the reduction of therapeutic options, making the use of antimicrobial combinations necessary for the treatment, such as meropenem, amikacin, and colistin. Antibodies against bacterial species, mainly immunoglobulins G (IgG), are produced for acting as effector mechanisms (neutralization, opsonization, phagocytosis, and complement system activation). Some studies have demonstrated promising results of IgG in combination with antimicrobial preparations against bacterial infections, in which the direct action of IgG has restored the immune system balance. Serious problem caused by the increase of MDR A. baumannii isolates results in a constant search for therapeutic alternatives to defeat these infections. However, this study aims to verify in vitro the phagocytosis rate of the A. baumannii-infected human monocytes, as well as to analyze possible morphological changes induced by intravenous immunoglobulin G (IVIG) with human serum in association with antimicrobials. The phagocytosis rate and bacterial cell binding capacity of IVIG were determined for two A. baumannii isolates submitted to 4 mg/mL of human IVIG alone and in combination with different sub-minimum inhibitory concentrations (sub-MICs) of meropenem, amikacin, and colistin and processed for indirect immunofluorescence. Subsequently, these isolates were resubmitted and coupled with human serum and processed for scanning electron microscopy. There was no statistical difference for phagocytosis rates in the isolates tested. Bacterial isolates showed alterations in cell morphology when exposed to IVIG/human serum alone and in combination with antimicrobials such as alteration in shape, wrinkling, membrane depression, and especially cell rupture with extravasation of cytoplasmic material. The isolates visually differed in the IVIG binding to the bacterial cell, with higher fluorescence intensity, which corresponds to the highest IVIG binding, in the isolate more sensitive to meropenem, amikacin, and colistin. No differences between treatments were observed in the IVIG binding to the bacterial cell. The combined action of IVIG with meropenem, amikacin, and colistin against A. baumannii MDR isolates induced several bacterial cell damages. And when associated with human serum, a massive destruction of cells can be observed. These results may suggest the analysis of the use of IgG preparations for the treatment of A. baumannii MDR infections.

Harnessing the Immunomodulatory Properties of Bacterial Ghosts to Boost the Anti-mycobacterial Protective Immunity

Tuberculosis (TB) pathogenesis is characterized by inadequate immune cell activation and delayed T cell response in the host. Recent immunotherapeutic efforts have been directed at stimulating innate immunity and enhancing interactions between antigen presenting cells and T cells subsets to improve the protective immunity against TB. In this study, we investigated the immunostimulatory properties of bacterial ghosts (BG) as a novel approach to potentiate the host immunity against mycobacterial infection. BG are intact cytoplasm-free Escherichia coli envelopes and have been developed as bacterial vaccines and adjuvant/delivery system in cancer immunotherapy. However, BG have yet to be exploited as immunopotentiators in the context of infectious diseases. Here, we showed that BG are potent inducers of dendritic cells (DC), which led to enhanced T cell proliferation and differentiation into effector cells. BG also induced macrophage activation, which was associated with enhanced nitric oxide production, a key anti-mycobacterial weapon. We further demonstrated that the immunostimulatory capability of BG far exceeds that of LPS and involves both TLR4-dependent and independent pathways. Consistently, BG treatment, but not LPS treatment, reduced the bacterial burden in infected mice, which correlated with increased influx of innate and adaptive effector immune cells and increased production of key cytokines in the lungs. Finally and importantly, enhanced bacilli killing was seen in mice co-administered with BG and second-line TB drugs bedaquiline and delamanid. Overall, this work paves the way for BG as potent immunostimulators that may be harnessed to improve mycobacteria killing at the site of infection.

Adjunct antibody administration with standard treatment reduces relapse rates in a murine tuberculosis model of necrotic granulomas

Matrix metalloproteinase (MMP)-9 is a zinc-dependent protease associated with early immune responses to Mycobacterium tuberculosis infection, macrophage recruitment and granuloma formation. We evaluated whether adjunctive inhibition of MMP-9 could improve the response to standard TB treatment in a mouse model that develops necrotic lesions. Six weeks after an aerosol infection with M. tuberculosis, C3HeB/FeJ mice received standard TB treatment (12 weeks) comprising rifampin, isoniazid and pyrazinamide alone or in combination with either anti-MMP-9 antibody, etanercept (positive control) or isotype antibody (negative control) for 6 weeks. Anti-MMP-9 and the isotype control had comparable high serum exposures and expected terminal half-life. The relapse rate in mice receiving standard TB treatment was 46.6%. Compared to the standard TB treatment, relapse rates in animals that received adjunctive treatments with anti-MMP-9 antibody or etanercept were significantly decreased to 25.9% (P = 0.006) and 29.8% (P = 0.019) respectively, but were not different from the arm that received the isotype control antibody (25.9%). Immunostaining demonstrated localization of MMP-9 primarily in macrophages in both murine and human lung tissues infected with M. tuberculosis, suggesting the importance of MMP-9 in TB pathogenesis. These data suggest that the relapse rates in M. tuberculosis-infected mice may be non-specifically improved by administration of antibodies in conjunction with standard TB treatments. Future studies are needed to evaluate the mechanism(s) leading to improved outcomes with adjunctive antibody treatments.

The use of immunotherapy for the treatment of tuberculosis

INTRODUCTION

Tuberculosis (TB) is the first cause of mortality by a single infectious agent in the world, causing more than one million deaths worldwide as reported by the World Health Organization (WHO). For the optimal control of TB infection, a protective immune response that limits bacterial spread without causing damage to the host is essential. Although most healthy individuals are capable of generating protective responses, patients who suffer pulmonary TB commonly present a defective immune function. Areas covered: We intend to highlight the potential of novel immunotherapeutic strategies that enhance and promote effective immune responses. The following methodology was undertaken for establishing a literature search: the authors used PubMed to search for 'Pulmonary Tuberculosis' and keywords that denoted the novel immunotherapeutic strategies discussed in length in the text including antibodies, antimicrobial peptides, cell therapy, cytokines and gene therapy. Expert commentary: The current therapeutic regimens for this disease are complex and involve the prolonged use of multiple antibiotics with diverse side effects that lead to therapeutic failure and bacterial resistance. The standard appliance of immunotherapy and its deployment to vulnerable populations will require coordinated work and may serve as a powerful tool to combat the ensuing threat of TB.