Mycobacterium tuberculosis latency-associated antigen Rv1733c SLP improves the accuracy of differential diagnosis of active tuberculosis and latent tuberculosis infection

Tuberculosis in infertility and in vitro fertilization-embryo transfer

ABSTRACT

Tuberculosis (TB) is a prominent infectious disease globally that imposes a substantial health burden. Genital TB (GTB), an extrapulmonary manifestation, leads to complications such as tubal adhesions, blockage, and diminished ovarian function, culminating in infertility, and is recognized as a prevalent cause of infertility in nations with high-burden TB. In regions with low TB rates, infertility and active TB during pregnancy have been reported to be most common among female immigrants from countries with high-burden TB. In the context of TB, pregnant women often exhibit exacerbated symptoms after in vitro fertilization-embryo transfer (IVF-ET), heightening the risk of dissemination. Miliary pulmonary TB and tuberculous meningitis pose a serious threat to maternal and fetal health. This article integrates recent epidemiological data and clinical research findings, delineating the impact of TB on infertility and assisted reproduction and particularly focusing on the diagnosis and treatment of GTB, underscored by the imperative of TB screening before IVF-ET. Our objective is to increase awareness among respiratory and reproductive health professionals, promoting multidisciplinary management to enhance clinical vigilance. This approach seeks to provide patients with judicious reproductive plans and scientifically rigorous pregnancy management, thereby mitigating adverse pregnancy outcomes related to TB activity.

Specific Cytokines Analysis Incorporating Latency-Associated Antigens Differentiates Mycobacterium tuberculosis Infection Status: An Exploratory Study

Introduction

Current immunologic methods cannot distinguish Mycobacterium tuberculosis (Mtb) infection statuses, especially to discriminate active tuberculosis (ATB) from latent tuberculosis infection (LTBI). This study explored the potential of latency-associated antigens (Rv1733cSLP and Rv2028c) and multifactorial cytokine detection to distinguish tuberculosis infection states.

Methods

ATB patients (20), LTBI healthcare workers (25), fever patients (11), and healthy controls (10) were enrolled. Cytokine levels (IFN-γ, TNF-α, IL-2, IL-6, IP-10, IL-1Ra, CXCL-1, and MCP-1) were measured using Luminex with/without MTB-specific virulence factor and latency-associated antigens stimulation.

Results

Without antigen stimulation, IL-6, IP-10, MCP-1, and IL-1Ra were higher in the ATB group than in the LTBI group (p<0.05), but no significant differences between the ATB group and the fever group. Stimulated with the four antigens, respectively, the cytokines, including IP-10Esat-6, IP-10CFP-10, IFN-γRv1733cSLP, IFN-γRv2028c, IL-6Esat-6, IL-6Rv1733cSLP, IL-6Rv2028c, IL-2Rv1733cSLP, IL-2 Rv2028c, IL-1RaEsat-6, IL-1RaCFP-10, IL-1RaRv2028c, CXCL-1Esat-6, CXCL-1CFP-10, CXCL-1Rv1733cSLP, CXCL-1Rv2028c, MCP-1Esat-6 and MCP-1CFP-10, demonstrated accurate discrimination between ATB and LTBI (p<0.05). Additive concentrations demonstrated significant secretion differences of IFN-γ, IP-10 and IL-2, primarily by virulence factors in ATB and latency-associated antigens in LTBI. Latency-associated antigens synergized with virulence factors, enhancing TH1-type cytokine diagnostic efficacy for discriminating ATB from LTBI, the AUC for TNF-α increased from 0.696 to 0.820 (p=0.038), IFN-γ increased from 0.806 to 0.962 (p=0.025), and IL-2 increased from 0.565 to 0.868 (p=0.007). Model selected by forward likelihood method indicated combined detection of IFN-γCFP-10, IFN-γRv1733cSLP, IP-10Rv1733cSLP, and CXCL-1Rv1733cSLP achieved ATB diagnosis (AUC=0.996) and ATB-LTBI differentiation (AUC=0.992). Combined detection of IFN-γCFP-10 and IFN-γRv1733cSLP achieved tuberculosis infection diagnosis (AUC=0.943).

Conclusion

Latency-associated antigens enhance multiple cytokine discriminatory ability, particularly TH1-type cytokines, for differentiating Mtb infection statuses.

HigA2 (Rv2021c) Is a Transcriptional Regulator with Multiple Regulatory Targets in Mycobacterium tuberculosis

Toxin-antitoxin (TA) systems are the major mechanism for persister formation in Mycobacterium tuberculosis (Mtb). Previous studies found that HigBA2 (Rv2022c-Rv2021c), a predicted type II TA system of Mtb, could be activated for transcription in response to multiple stresses such as anti-tuberculosis drugs, nutrient starvation, endure hypoxia, acidic pH, etc. In this study, we determined the binding site of HigA2 (Rv2021c), which is located in the coding region of the upstream gene higB2 (Rv2022c), and the conserved recognition motif of HigA2 was characterized via oligonucleotide mutation. Eight binding sites of HigA2 were further found in the Mtb genome according to the conserved motif. RT-PCR showed that HigA2 can regulate the transcription level of all eight of these genes and three adjacent downstream genes. DNA pull-down experiments showed that twelve functional regulators sense external regulatory signals and may regulate the transcription of the HigBA2 system. Of these, Rv0903c, Rv0744c, Rv0474, Rv3124, Rv2603c, and Rv3583c may be involved in the regulation of external stress signals. In general, we identified the downstream target genes and possible upstream regulatory genes of HigA2, which paved the way for the illustration of the persistence establishment mechanism in Mtb.

Immunogenicity of PE18, PE31, and PPE26 proteins from Mycobacterium tuberculosis in humans and mice

Introduction

The large family of PE and PPE proteins accounts for as much as 10% of the genome of Mycobacterium tuberculosis. In this study, we explored the immunogenicity of three proteins from this family, PE18, PE31, and PPE26, in humans and mice.

Methods

The investigation involved analyzing the immunoreactivity of the selected proteins using sera from TB patients, IGRA-positive household contacts, and IGRA-negative BCG vaccinated healthy donors from the TB endemic country Mozambique. Antigen-recall responses were examined in PBMC from these groups, including the evaluation of cellular responses in healthy unexposed individuals. Moreover, systemic priming and intranasal boosting with each protein, combined with the Quil-A adjuvant, were conducted in mice.

Results

We found that all three proteins are immunoreactive with sera from TB patients, IGRA-positive household contacts, and IGRA-negative BCG vaccinated healthy controls. Likewise, antigen-recall responses were induced in PBMC from all groups, and the proteins stimulated proliferation of peripheral blood mononuclear cells from healthy unexposed individuals. In mice, all three antigens induced IgG antibody responses in sera and predominantly IgG, rather than IgA, responses in bronchoalveolar lavage. Additionally, CD4+ and CD8+ effector memory T cell responses were observed in the spleen, with PE18 demonstrating the ability to induce tissue-resident memory T cells in the lungs.

Discussion

Having demonstrated immunogenicity in both humans and mice, the protective capacity of these antigens was evaluated by challenging immunized mice with low-dose aerosol of Mycobacterium tuberculosis H37Rv. The in vitro Mycobacterial Growth Inhibition Assay (MGIA) and assessment of viable bacteria in the lung did not demonstrate any ability of the vaccination protocol to reduce bacterial growth. We therefore concluded that these three specific PE/PPE proteins, while immunogenic in both humans and mice, were unable to confer protective immunity under these conditions.

Challenges and the Way forward in Diagnosis and Treatment of Tuberculosis Infection

Globally, it is estimated that one-quarter of the world's population is latently infected with Mycobacterium tuberculosis (Mtb), also known as latent tuberculosis infection (LTBI). Recently, this condition has been referred to as tuberculosis infection (TBI), considering the dynamic spectrum of the infection, as 5-10% of the latently infected population will develop active TB (ATB). The chances of TBI development increase due to close contact with index TB patients. The emergence of multidrug-resistant TB (MDR-TB) and the risk of development of latent MDR-TB has further complicated the situation. Detection of TBI is challenging as the infected individual does not present symptoms. Currently, there is no gold standard for TBI diagnosis, and the only screening tests are tuberculin skin test (TST) and interferon gamma release assays (IGRAs). However, these tests have several limitations, including the inability to differentiate between ATB and TBI, false-positive results in BCG-vaccinated individuals (only for TST), false-negative results in children, elderly, and immunocompromised patients, and the inability to predict the progression to ATB, among others. Thus, new host markers and Mtb-specific antigens are being tested to develop new diagnostic methods. Besides screening, TBI therapy is a key intervention for TB control. However, the long-course treatment and associated side effects result in non-adherence to the treatment. Additionally, the latent MDR strains are not susceptible to the current TBI treatments, which add an additional challenge. This review discusses the current situation of TBI, as well as the challenges and efforts involved in its control.