Effects of in vitro HIV-1 infection on mycobacterial growth in peripheral blood monocyte-derived macrophages

Uncovering the Bronchoalveolar Single-Cell Landscape of Patients With Pulmonary Tuberculosis With Human Immunodeficiency Virus Type 1 Coinfection

BACKGROUND

Coinfection of human immunodeficiency virus type 1 (HIV-1) is the most significant risk factor for tuberculosis (TB). The immune responses of the lung are essential to restrict the growth of Mycobacterium tuberculosis and avoid the emergence of the disease. Nevertheless, there is still limited knowledge about the local immune response in people with HIV-1-TB coinfection.

METHODS

We employed single-cell RNA sequencing (scRNA-seq) on bronchoalveolar lavage fluid from 9 individuals with HIV-1-TB coinfection and 10 with pulmonary TB.

RESULTS

A total of 19 058 cells were grouped into 4 major cell types: myeloid cells, T/natural killer (NK) cells, B cells, and epithelial cells. The myeloid cells and T/NK cells were further divided into 10 and 11 subsets, respectively. The proportions of dendritic cell subsets, CD4+ T cells, and NK cells were lower in the HIV-1-TB coinfection group compared to the TB group, while the frequency of CD8+ T cells was higher. Additionally, we identified numerous differentially expressed genes between the CD4+ and CD8+ T-cell subsets between the 2 groups.

CONCLUSIONS

HIV-1 infection not only affects the abundance of immune cells in the lungs but also alters their functions in patients with pulmonary TB.

Plasma Ribonuclease Activity in Antiretroviral Treatment-Naive People With Human Immunodeficiency Virus and Tuberculosis Disease

BACKGROUND

The role of ribonucleases in tuberculosis among people with human immunodeficiency virus (HIV; PWH) is unknown. We explored ribonuclease activity in plasma from PWH with and without tuberculosis.

METHODS

Participants were identified from a cohort of treatment-naive PWH in Ethiopia who had been classified for tuberculosis disease (HIV positive [HIV+]/tuberculosis positive [tuberculosis+] or HIV+/tuberculosis negative [tuberculosis-]). Ribonuclease activity in plasma was investigated by quantification of synthetic spike-in RNAs using sequencing and quantitative polymerase chain reaction and by a specific ribonuclease activity assay. Quantification of ribonuclease 1, 2, 3, 6, 7, and T2 proteins was performed by enzyme-linked immunosorbent assay. Ribonuclease activity and protein concentrations were correlated with markers of tuberculosis and HIV disease severity and with concentrations of inflammatory mediators.

RESULTS

Ribonuclease activity was significantly higher in plasma of HIV+/tuberculosis+ (n = 51) compared with HIV+/tuberculosis- (n = 78), causing reduced stability of synthetic spike-in RNAs. Concentrations of ribonucleases 2, 3, and T2 were also significantly increased in HIV+/tuberculosis+ compared with HIV+/tuberculosis-. Ribonuclease activity was correlated with HIV viral load, and inversely correlated with CD4 cell count, mid-upper arm circumference, and body mass index. Moreover, ribonuclease activity was correlated with concentrations of interleukin 27, procalcitonin and the kynurenine-tryptophan ratio.

CONCLUSIONS

PWH with tuberculosis disease have elevated plasma ribonuclease activity, which is also associated with HIV disease severity and systemic inflammation.

Mitochondrial Metabolism in Alveolar Macrophages of Patients Infected with HIV, Tuberculosis, and HIV/Tuberculosis

Tuberculosis (TB) is one of the most common opportunistic infections and is a leading cause of mortality in patients with HIV and AIDS. HIV infection causes serious defects in the host immune system and increases the risk of active TB. TB infection promotes HIV replication and aggravates host damage in patients with HIV/AIDS. Alveolar macrophages (AMs) are essential immune cells during TB and HIV infections. AMs undergo a shift in mitochondrial metabolism during TB or HIV infection, that is, metabolic reprogramming, allowing them to act in the form of classical activated macrophages (M1) and alternative activated macrophages (M2) at different stages of infection. We reviewed the alterations in the mitochondrial energy metabolism of AMs in patients with HIV, TB, and HIV/TB to provide ideas for further research on the role of metabolic reprogramming by AMs in the pathogeneses of HIV, TB, and HIV/TB coinfection.

Early innate cell interactions with Mycobacterium tuberculosis in protection and pathology of tuberculosis

Tuberculosis (TB) remains a significant global health challenge, claiming the lives of up to 1.5 million individuals annually. TB is caused by the human pathogen Mycobacterium tuberculosis (Mtb), which primarily infects innate immune cells in the lungs. These immune cells play a critical role in the host defense against Mtb infection, influencing the inflammatory environment in the lungs, and facilitating the development of adaptive immunity. However, Mtb exploits and manipulates innate immune cells, using them as favorable niche for replication. Unfortunately, our understanding of the early interactions between Mtb and innate effector cells remains limited. This review underscores the interactions between Mtb and various innate immune cells, such as macrophages, dendritic cells, granulocytes, NK cells, innate lymphocytes-iNKT and ILCs. In addition, the contribution of alveolar epithelial cell and endothelial cells that constitutes the mucosal barrier in TB immunity will be discussed. Gaining insights into the early cellular basis of immune reactions to Mtb infection is crucial for our understanding of Mtb resistance and disease tolerance mechanisms. We argue that a better understanding of the early host-pathogen interactions could inform on future vaccination approaches and devise intervention strategies.

A Review of the Development of Multitarget Molecules against HIV-TB Coinfection Pathogens

The human immunodeficiency virus (HIV) produces the pathologic basis of acquired immunodeficiency syndrome (AIDS). An increase in the viral load in the body leads to a decline in the number of T lymphocytes, compromising the patient's immune system. Some opportunistic diseases may result, such as tuberculosis (TB), which is the most common in seropositive patients. Long-term treatment is required for HIV-TB coinfection, and cocktails of drugs for both diseases are used concomitantly. The most challenging aspects of treatment are the occurrence of drug interactions, overlapping toxicity, no adherence to treatment and cases of resistance. Recent approaches have involved using molecules that can act synergistically on two or more distinct targets. The development of multitarget molecules could overcome the disadvantages of the therapies used to treat HIV-TB coinfection. This report is the first review on using molecules with activities against HIV and Mycobacterium tuberculosis (MTB) for molecular hybridization and multitarget strategies. Here, we discuss the importance and development of multiple targets as a means of improving adherence to therapy in cases of the coexistence of these pathologies. In this context, several studies on the development of structural entities to treat HIV-TB simultaneously are discussed.

Systems biology approaches to investigate the role of granulomas in TB-HIV coinfection

The risk of active tuberculosis disease is 15-21 times higher in those coinfected with human immunodeficiency virus-1 (HIV) compared to tuberculosis alone, and tuberculosis is the leading cause of death in HIV+ individuals. Mechanisms driving synergy between Mycobacterium tuberculosis (Mtb) and HIV during coinfection include: disruption of cytokine balances, impairment of innate and adaptive immune cell functionality, and Mtb-induced increase in HIV viral loads. Tuberculosis granulomas are the interface of host-pathogen interactions. Thus, granuloma-based research elucidating the role and relative impact of coinfection mechanisms within Mtb granulomas could inform cohesive treatments that target both pathogens simultaneously. We review known interactions between Mtb and HIV, and discuss how the structure, function and development of the granuloma microenvironment create a positive feedback loop favoring pathogen expansion and interaction. We also identify key outstanding questions and highlight how coupling computational modeling with in vitro and in vivo efforts could accelerate Mtb-HIV coinfection discoveries.

Direct Attachment with Erythrocytes Augments Extracellular Growth of Pathogenic Mycobacteria

Pathogenic intracellular mycobacteria, such as Mycobacterium tuberculosis and Mycobacterium avium, which cause lung diseases, can grow in macrophages. Extracellular mycobacteria have been reported in the lungs, blood, and sputum of patients, indicating the involvement of these pathogens in disease progression. Erythrocytes are involved in the symptoms associated with pulmonary mycobacterial diseases, such as bloody sputum and hemoptysis; however, little attention has been paid to the role of erythrocytes in mycobacterial diseases. Herein, we found that Mycobacterium avium subsp. hominissuis (MAH) and Mycobacterium intracellulare colocalized with erythrocytes at the sites of lung infection, inside capillaries and necrotic areas of granulomas, using histopathological examinations. Electron microscopy showed that MAH adhered and entered human erythrocytes when they were cocultured in vitro. MAH adhered to erythrocytes through complement receptor 1 and cell-surface sialo-glycoproteins. Importantly, MAH grew vigorously without causing any pronounced damage to erythrocytes. This erythrocyte-mediated enhancement of MAH growth occurred extracellularly depending on its direct attachment to erythrocytes. In contrast, MAH failed to multiply inside erythrocytes. Similarly, erythrocytes augmented the growth of other pathogenic mycobacteria, such as M. intracellulare and M. tuberculosis. THP-1 cell-derived human macrophages preferentially phagocytosed erythrocytes that were attached to mycobacteria (compared to bacteria alone), suggesting that erythrocyte-attached mycobacteria are an efficient infectious source for macrophages. Our findings provide new insights into the pathogenesis of mycobacterial diseases and offer an alternative and useful strategy for treating mycobacterial disease. IMPORTANCE Pathogenic mycobacteria, such as Mycobacterium tuberculosis, Mycobacterium avium subsp. hominissuis (MAH), and Mycobacterium intracellulare, cause pulmonary infections as intracellular parasites of lung macrophages and epithelial cells. Here, using histopathological examinations we found that MAH and M. intracellulare colocalized with erythrocytes in lung infection sites. Subsequent studies demonstrated that direct interaction with erythrocytes enhances the extracellular proliferation of mycobacteria based on the following results: 1. MAH adhered and invaded human erythrocytes upon coculture in vitro; 2. MAH adhered to erythrocytes through complement receptor 1 and cell-surface sialo-glycoproteins; 3. MAH rapidly proliferated when directly attached to erythrocytes but not within them; 4. other mycobacteria, such as M. intracellulare and M. tuberculosis, also proliferated in the same way as MAH. The finding that pathogenic mycobacteria grow extracellularly in an erythrocyte-dependent manner is of considerable clinical importance for understanding disease progression and latent infection.

Expression of MicroRNAs Is Dysregulated by HIV While Mycobacterium tuberculosis Drives Alterations of Small Nucleolar RNAs in HIV Positive Adults With Active Tuberculosis

HIV infection affects the course of tuberculosis (TB), and HIV and Mycobacterium tuberculosis (Mtb) synergize in disease progression through complex immunological interplay. To gain further understanding of these mechanisms, we compared the microRNA (miRNA) and small nucleolar RNA (snoRNA) expression patterns in whole blood of individuals with active TB, with and without HIV coinfection (HIV+/TB+ and HIV-/TB+), and HIV and TB-negative individuals (HIV-/TB-). We found that 218 miRNAs were differentially expressed between HIV+/TB+ and HIV-/TB+, while no statistically significant difference in snoRNA expression was observed between these groups. In contrast, both miRNA (n = 179) and snoRNA (n = 103) expression patterns were significantly altered in HIV+/TB+ individuals compared to those of the HIV-/TB- controls. Of note, 26 of these snoRNAs were also significantly altered between the HIV-/TB+ and HIV-/TB- groups. Normalization toward the miRNA and snoRNA expression patterns of the HIV-/TB- control group was noted during anti-TB and antiretroviral treatment in HIV+/TB+ participants. In summary, these results show that HIV coinfection influences miRNA expression in active TB. In contrast, snoRNA expression patterns differ between individuals with and without active TB, independently of HIV coinfection status. Moreover, in coinfected individuals, therapy-induced control of HIV replication and clearance of Mtb appears to normalize the expression of some small non-coding RNA (sncRNA). These findings suggest that dysregulation of miRNA is a mechanism by which HIV may modify immunity against TB, while active TB alters snoRNA expression. Improved understanding of how regulation of sncRNA expression influences the disease course in coinfected individuals may have implications for diagnostics, risk stratification, and host-directed therapy. Here, we propose a novel mechanism by which HIV alters the immune response to TB.

Clinical Characteristics, Diagnosis, Treatment, and Mortality Rate of TB/COVID-19 Coinfectetd Patients: A Systematic Review

Introduction: Novel coronavirus (COVID-19) and tuberculosis (TB) are the newest and one of the oldest global threats, respectively. In the COVID-19 era, due to the health system's focus on the COVID-19 epidemic, the national TB control program received less attention, leading to a worsening of the global TB epidemic. In this study, we will review the characteristics of TB patients coinfected with COVID-19.

Material and Methods: Using Scopus, PubMed/Medline, Embase, and Web of Science databases, a systematic search was performed. Case reports and case series on TB/COVID-19 coinfection published from January 1, 2019 to February 24, 2021 were collected. There were no limitations regarding publication language.

Results: Eleven case series and 20 case reports were identified from 18 countries, with the majority them being from India (N = 6) and China (N = 4). Overall, 146 patients (114 men and 32 women) coinfected with TB and COVID-19 enrolled. Smoking (15.1%), diabetes (14.4%), and hypertension (8.9%) were the most frequent comorbidities among these patients. The COVID-19 patients with TB mainly suffered fever (78.8%), cough (63.7%), and respiratory distress (22.6%). Hydroxychloroquine (64.0%) and lopinavir/ritonavir (39.5%) were the most common treatments for them. The mortality rate was 13.0% and the rate of discharged patients was 87.0%.

Conclusion: Global prevalence of COVID-19-related deaths is 6.6%. Our results showed that 13.0% of patients with TB/COVID-19 died. Thus, this study indicated that coinfection of TB and COVID-19 can increase the mortality. The respiratory symptoms of TB and COVID-19 are very similar, and this causes them to be misdiagnosed. In addition, TB is sometimes diagnosed later than COVID-19 and the severity of the disease worsens, especially in patients with underlying conditions. Therefore, patients with TB should be screened regularly in the COVID-19 era to prevent the spread of the TB/COVID-19 coinfection.

The Pathology of Lymphocytes, Histiocytes, and Immune Mechanisms in Mycobacterium tuberculosis Granulomas

Granuloma formation is the pathologic hallmark of tuberculosis (TB). Few studies have detailed the exact production of cytokines in human granulomatous inflammation and little is known about accessory molecule expressions in tuberculous granulomas. We aimed to identify some of the components of the immune response in granulomas in HIV-positive and -negative lymph nodes. We investigated the immunohistochemical profiles of CD4+, CD8+, CD68+, Th-17, Forkhead box P3 (FOXP3) cells, accessory molecule expression (human leukocyte antigen [HLA] classes I and II), and selected cytokines (interleukins 2, 4, and 6 and interferon-γ) of various cells, in granulomas within lymph nodes from 10 HIV-negative (-) and 10 HIV-positive (+) cases. CD4+ lymphocyte numbers were retained in HIV- granulomas, whereas CD4+:CD8 + cell were reversed in HIV+ TB granulomas. CD68 stained all histiocytes. Granulomas from the HIV+ group demonstrated a significant increase in FOXP3 cells. Interleukin-2 cytoplasmic expression was similar in both groups. Interferon-gamma (IFN-γ) expression was moderately increased, IL-6 was statistically increased and IL-4 expression was marginally lower in cells from HIV- than HIV+ TB granulomas. Greater numbers of cells expressed IFN-γ and IL-6 than IL-2 and IL-4 in HIV- TB granulomas. This study highlights the varied cytokine production in HIV-positive and -negative TB granulomas and indicates the need to identify localized tissue factors that play a role in mounting an adequate immune response required to halt infection. Although TB mono-infection causes variation in cell marker expression and cytokines in granulomas, alterations in TB and HIV coinfection are greater, pointing toward evolution of microorganism synergism.

Monocytic-Myeloid Derived Suppressor Cells of HIV-Infected Individuals With Viral Suppression Exhibit Suppressed Innate Immunity to Mycobacterium tuberculosis

Tuberculosis can occur during any stage of Human Immunodeficiency virus 1 (HIV) -infection including times when CD4⁺ T cell numbers have reconstituted and viral replication suppressed. We have previously shown that CD11b⁺CD33⁺CD14⁺HLA-DR^-/lo monocytic myeloid-derived suppressor cells (MDSC) persist in HIV-infected individuals on combined anti-retroviral therapy (cART) and with virologic suppression. The response of MDSC to Mycobacterium tuberculosis (Mtb) is not known. In this study, we compared the anti-mycobacterial activity of MDSC isolated from HIV –infected individuals on cART with virologic suppression (HIV MDSC) and HIV-uninfected healthy controls (HIV (-) MDSC). Compared to HIV (-) MDSC, HIV MDSC produced significantly less quantities of anti-mycobacterial cytokines IL-12p70 and TNFα, and reactive oxygen species when cultured with infectious Mtb or Mtb antigens. Furthermore, HIV MDSC showed changes in the Toll-like receptor and IL-27 signaling, including reduced expression of MyD88 and higher levels of IL-27. Neutralizing IL-27 and overexpression of MyD88 synergistically controlled intracellular replication of Mtb in HIV MDSC. These results demonstrate that MDSC in fully suppressed HIV-infected individuals are permissive to Mtb and exhibit downregulated anti-mycobacterial innate immune activity through mechanisms involving IL-27 and TLR signaling. Our findings suggest MDSC as novel mediators of tuberculosis in HIV-Mtb co-infected individuals with virologic suppression.

Trehalose limits opportunistic mycobacterial survival during HIV co-infection by reversing HIV-mediated autophagy block

Opportunistic bacterial infections amongst HIV-infected individuals contribute significantly to HIV-associated mortality. The role of HIV-mediated modulation of innate mechanisms like autophagy in promoting opportunistic infections, however, remains obscure. Here we show, HIV reactivation in or infection of macrophages inhibits autophagy and helps the survival of pathogenic Mycobacterium tuberculosis (Mtb) and nonpathogenic non-tuberculous mycobacterial strains (NTMs). The HIV-mediated impairment of xenophagy flux facilitated bacterial survival. Activation of autophagy by trehalose could induce xenophagy flux and kill intracellular Mtb or NTMs either during single or co-infections. Trehalose, we delineate, activates PIKFYVE leading to TFEB nuclear translocation in MCOLN1-dependent manner to induce autophagy. Remarkably, trehalose significantly reduced HIV-p24 levels in ex-vivo-infected PBMCs or PBMCs from treatment-naive HIV patients and also controlled mycobacterial survival within Mtb-infected animals. To conclude, we report leveraging of HIV-mediated perturbed host innate-immunity by opportunistic bacterial pathogens and show an attractive therapeutic strategy for HIV and associated co-morbidities.Abbreviations: AIDS: acquired immune deficiency syndrome; AMPK: AMP-activated protein kinase; ATG5: autophagy related 5; BafA1: bafilomycin A1; CFU: colony forming unit; CTSD: cathepsin D; CD63: CD63 molecule; EGFP: enhanced green fluorescent protein; FRET: Förster resonance energy transfer; GABARAP: gamma-aminobutyric acid receptor-associated protein; GAPDH: glyceraldehyde 3-phosphate dehydrogenase; GLUT: glucose transporter; HIV: human immunodeficiency virus; hMDMs: human monocyte derived macrophages; IL2: interleukin 2; LAMP1: lysosomal-associated membrane protein 1; LC3B-II: lipidated microtubule-associated proteins 1A/1B light chain 3B; Mtb: Mycobacterium tuberculosis; MTOR: mechanistic target of rapamycin; mRFP: monomeric red fluorescent protein; M6PR: mannose-6-phosphate receptor; NAC: N- acetyl- L -cysteine; NTM's: non-tuberculous mycobacteria; PBMC: Peripheral Blood Mononuclear cells; PIKFYVE: phosphoinositide kinase; FYVE-Type Zinc Finger; PHA: phytohemagglutinin; PMA: phorbol 12-myristate 13-acetate; PtdIns(3,5)P2: Phosphatidylinositol 3,5-bisphosphate; ptfLC3: pEGFP-mRFP-LC3; ROS: reactive oxygen species; SQSTM1: sequestosome1; TFEB: transcription factor EB; MCOLN1/TRPML1: mucolipin 1; PIP4P1/TMEM55B: Human trans-membrane Protein 55B; UVRAG: UV Radiation Resistance Associate; VPS35: vacuolar protein sorting associated protein 35; WDR45: WD repeat domain 45; YCAM: Yellow Chameleon.

Perspectives and Advances in the Understanding of Tuberculosis

Mycobacterium tuberculosis (Mtb), the causative agent of tuberculosis (TB), remains a leading cause of death due to infection in humans. To more effectively combat this pandemic, many aspects of TB control must be developed, including better point of care diagnostics, shorter and safer drug regimens, and a protective vaccine. To address all these areas of need, better understanding of the pathogen, host responses, and clinical manifestations of the disease is required. Recently, the application of cutting-edge technologies to the study of Mtb pathogenesis has resulted in significant advances in basic biology, vaccine development, and antibiotic discovery. This leaves us in an exciting era of Mtb research in which our understanding of this deadly infection is improving at a faster rate than ever, and renews hope in our fight to end TB. In this review, we reflect on what is known regarding Mtb pathogenesis, highlighting recent breakthroughs that will provide leverage for the next leaps forward in the field.

Fatal central nervous system co-infection with SARS-CoV-2 and tuberculosis in a healthy child

BACKGROUND

Central and peripheral nervous system symptoms and complications are being increasingly recognized among individuals with pandemic SARS-CoV-2 infections, but actual detection of the virus or its RNA in the central nervous system has rarely been sought or demonstrated. Severe or fatal illnesses are attributed to SARS-CoV-2, generally without attempting to evaluate for alternative causes or co-pathogens.

CASE PRESENTATION

A five-year-old girl with fever and headache was diagnosed with acute SARS-CoV-2-associated meningoencephalitis based on the detection of its RNA on a nasopharyngeal swab, cerebrospinal fluid analysis, and magnetic resonance imaging findings. Serial serologic tests for SARS-CoV-2 IgG and IgA showed seroconversion, consistent with an acute infection. Mental status and brain imaging findings gradually worsened despite antiviral therapy and intravenous dexamethasone. Decompressive suboccipital craniectomy for brain herniation with cerebellar biopsy on day 30 of illness, shortly before death, revealed SARS-CoV-2 RNA in cerebellar tissue using the Centers for Disease Control and Prevention 2019-nCoV Real-Time Reverse Transcriptase-PCR Diagnostic Panel. On histopathology, necrotizing granulomas with numerous acid-fast bacilli were visualized, and Mycobacterium tuberculosis complex DNA was detected by PCR. Ventricular cerebrospinal fluid that day was negative for mycobacterial DNA. Tracheal aspirate samples for mycobacterial DNA and culture from days 22 and 27 of illness were negative by PCR but grew Mycobacterium tuberculosis after 8 weeks, long after the child's passing. She had no known exposures to tuberculosis and no chest radiographic findings to suggest it. All 6 family members had normal chest radiographs and negative interferon-γ release assay results. The source of her tuberculous infection was not identified, and further investigations by the local health department were not possible because of the State of Michigan-mandated lockdown for control of SARS-CoV-2 spread.

CONCLUSION

The detection of SARS-CoV-2 RNA in cerebellar tissue and the demonstration of seroconversion in IgG and IgA assays was consistent with acute SARS-CoV-2 infection of the central nervous infection. However, the cause of death was brain herniation from her rapidly progressive central nervous system tuberculosis. SARS-CoV-2 may mask or worsen occult tuberculous infection with severe or fatal consequences.

SIV and Mycobacterium tuberculosis synergy within the granuloma accelerates the reactivation pattern of latent tuberculosis

Human immunodeficiency virus infection is the most common risk factor for severe forms of tuberculosis (TB), regardless of CD4 T cell count. Using a well-characterized cynomolgus macaque model of human TB, we compared radiographic, immunologic and microbiologic characteristics of early (subclinical) reactivation of latent M. tuberculosis (Mtb) infection among animals subsequently infected with simian immunodeficiency virus (SIV) or who underwent anti-CD4 depletion by a depletion antibody. CD4 depleted animals had significantly fewer CD4 T cells within granulomas compared to Mtb/SIV co-infected and Mtb-only control animals. After 2 months of treatment, subclinical reactivation occurred at similar rates among CD4 depleted (5 of 7 animals) and SIV infected animals (4 of 8 animals). However, SIV-induced reactivation was associated with more dissemination of lung granulomas that were permissive to Mtb growth resulting in greater bacterial burden within granulomas compared to CD4 depleted reactivators. Granulomas from Mtb/SIV animals displayed a more robust T cell activation profile (IFN-α, IFN-γ, TNF, IL-17, IL-2, IL-10, IL-4 and granzyme B) compared to CD4 depleted animals and controls though these effectors did not protect against reactivation or dissemination, but instead may be related to increased viral and/or Mtb antigens. SIV replication within the granuloma was associated with reactivation, greater overall Mtb growth and reduced Mtb killing resulting in greater overall Mtb burden. These data support that SIV disrupts protective immune responses against latent Mtb infection beyond the loss of CD4 T cells, and that synergy between SIV and Mtb occurs within granulomas.

Mycobacterium avium complex infection in pigs: A review

Mycobacterial infections in pigs are caused particularly by the Mycobacterium avium complex (MAC) and these infections lead to great economic losses mainly within the countries with high pork meat production. The importance of the MAC infections in humans is rising because of its higher prevalence and also higher mortality rates particularly in advanced countries. In addition, treatment of the MAC infections in humans tends to be complicated because of its increasing resistance to antimicrobial agents. Several studies across Europe have documented the MAC occurrence in the slaughtered pigs - not only in their lymph nodes and tonsils, which are the most frequent, but also in the diaphragmas, other organs and not least in meat. This is why we need both more specific and more sensitive methods for the MAC infection detection. Different PCR assays were established as well as advanced intravital testing by the gamma interferon release test. On the other hand, tuberculin skin test is still one of the cheapest methods of mycobacterial infections detection.

The Immune Response to Mycobacterium tuberculosis in HIV-1-Coinfected Persons

Globally, about 36.7 million people were living with HIV infection at the end of 2015. The most frequent infection co-occurring with HIV-1 is Mycobacterium tuberculosis-374,000 deaths per annum are attributable to HIV-tuberculosis, 75% of those occurring in Africa. HIV-1 infection increases the risk of tuberculosis by a factor of up to 26 and alters its clinical presentation, complicates diagnosis and treatment, and worsens outcome. Although HIV-1-induced depletion of CD4⁺ T cells underlies all these effects, more widespread immune deficits also contribute to susceptibility and pathogenesis. These defects present a challenge to understand and ameliorate, but also an opportunity to learn and optimize mechanisms that normally protect people against tuberculosis. The most effective means to prevent and ameliorate tuberculosis in HIV-1-infected people is antiretroviral therapy, but this may be complicated by pathological immune deterioration that in turn requires more effective host-directed anti-inflammatory therapies to be derived.

Epigenetic alterations are associated with monocyte immune dysfunctions in HIV-1 infection

Monocytes are key cells in the immune dysregulation observed during human immunodeficiency virus (HIV) infection. The events that take place specifically in monocytes may contribute to the systemic immune dysfunction characterized by excessive immune activation in infected individuals, which directly correlates with pathogenesis and progression of the disease. Here, we investigated the immune dysfunction in monocytes from untreated and treated HIV + patients and associated these findings with epigenetic changes. Monocytes from HIV patients showed dysfunctional ability of phagocytosis and killing, and exhibited dysregulated cytokines and reactive oxygen species production after M. tuberculosis challenge in vitro. In addition, we showed that the expression of enzymes responsible for epigenetic changes was altered during HIV infection and was more prominent in patients that had high levels of soluble CD163 (sCD163), a newly identified plasmatic HIV progression biomarker. Among the enzymes, histone acetyltransferase 1 (HAT1) was the best epigenetic biomarker correlated with HIV - sCD163 high patients. In conclusion, we confirmed that HIV impairs effector functions of monocytes and these alterations are associated with epigenetic changes that once identified could be used as targets in therapies aiming the reduction of the systemic activation state found in HIV patients.

Pathogenesis of HIV-1 and Mycobacterium tuberculosis co-infection

Co-infection with Mycobacterium tuberculosis is the leading cause of death in individuals infected with HIV-1. It has long been known that HIV-1 infection alters the course of M. tuberculosis infection and substantially increases the risk of active tuberculosis (TB). It has also become clear that TB increases levels of HIV-1 replication, propagation and genetic diversity. Therefore, co-infection provides reciprocal advantages to both pathogens. In this Review, we describe the epidemiological associations between the two pathogens, selected interactions of each pathogen with the host and our current understanding of how they affect the pathogenesis of TB and HIV-1/AIDS in individuals with co-infections. We evaluate the mechanisms and consequences of HIV-1 depletion of T cells on immune responses to M. tuberculosis. We also discuss the effect of HIV-1 infection on the control of M. tuberculosis by macrophages through phagocytosis, autophagy and cell death, and we propose models by which dysregulated inflammatory responses drive the pathogenesis of TB and HIV-1/AIDS.

The Immune Interaction between HIV-1 Infection and Mycobacterium tuberculosis

The modulation of tuberculosis (TB)-induced immunopathology caused by human immunodeficiency virus (HIV)-1 coinfection remains incompletely understood but underlies the change seen in the natural history, presentation, and prognosis of TB in such patients. The deleterious combination of these two pathogens has been dubbed a "deadly syndemic," with each favoring the replication of the other and thereby contributing to accelerated disease morbidity and mortality. HIV-1 is the best-recognized risk factor for the development of active TB and accounts for 13% of cases globally. The advent of combination antiretroviral therapy (ART) has considerably mitigated this risk. Rapid roll-out of ART globally and the recent recommendation by the World Health Organization (WHO) to initiate ART for everyone living with HIV at any CD4 cell count should lead to further reductions in HIV-1-associated TB incidence because susceptibility to TB is inversely proportional to CD4 count. However, it is important to note that even after successful ART, patients with HIV-1 are still at increased risk for TB. Indeed, in settings of high TB incidence, the occurrence of TB often remains the first presentation of, and thereby the entry into, HIV care. As advantageous as ART-induced immune recovery is, it may also give rise to immunopathology, especially in the lower-CD4-count strata in the form of the immune reconstitution inflammatory syndrome. TB-immune reconstitution inflammatory syndrome will continue to impact the HIV-TB syndemic.

Human Immunology of Tuberculosis

Immunology is a central theme when it comes to tuberculosis (TB). The outcome of human infection with Mycobacterium tuberculosis is dependent on the ability of the immune response to clear or contain the infection. In cases where this fails, the bacterium replicates, disseminates within the host, and elicits a pathologic inflammatory response, and disease ensues. Clinical presentation of TB disease is remarkably heterogeneous, and the disease phenotype is largely dependent on host immune status. Onward transmission of M. tuberculosis to new susceptible hosts is thought to depend on an excessive inflammatory response causing a breakdown of the lung matrix and formation of lung cavities. But this varies in cases of underlying immunological dysfunction: for example, HIV-1 infection is associated with less cavitation, while diabetes mellitus comorbidity is associated with increased cavitation and risk of transmission. In compliance with the central theme of immunology in tuberculosis, we rely on detection of an adaptive immune response, in the form of interferon-gamma release assays or tuberculin skin tests, to diagnose infection with M. tuberculosis. Here we review the immunology of TB in the human host, focusing on cellular and humoral adaptive immunity as well as key features of innate immune responses and the underlying immunological dysfunction which associates with human TB risk factors. Our review is restricted to human immunology, and we highlight distinctions from the immunological dogma originating from animal models of TB, which pervade the field.

Prevalence of small ruminant lentivirus and Mycobacterium avium subsp. paratuberculosis co-infection in Ontario dairy sheep and dairy goats

Infection with small ruminant lentiviruses (SRLV) causes a variety of chronic inflammatory conditions that limit production. Mycobacterium avium subsp. paratuberculosis (MAP) is also a major production-limiting disease of sheep and goats, which causes severe inflammation of the small intestine. Previous studies have indicated that both SRLV and MAP are widespread in small ruminants in Ontario. This study estimated the prevalence of SRLV and MAP co-infection. Serum samples that were previously tested for MAP infection were re-tested for SRLV. The apparent prevalence of co-infection was low, with 3.4% [95% confidence interval (CI): 1.9 to 5.9] and 14.3% (95% CI: 11.6 to 17.5) of sheep and goats respectively, positive for both infections. However, co-infection is widespread with 36.8% (95% CI: 19.1 to 59.1) and 71.4% (95% CI: 52.8 to 84.9) of sheep and goat farms with 1 or more co-infected animals. A significant association was found between SRLV seropositivity and MAP fecal culture (P = 0.021), suggesting that co-infected goats may be more likely to shed MAP in their feces.

Relationship Between HIV Coinfection, Interleukin 10 Production, and Mycobacterium tuberculosis in Human Lymph Node Granulomas

BACKGROUND

 Human immunodeficiency virus type 1 (HIV)-infected persons are more susceptible to tuberculosis than HIV-uninfected persons. Low peripheral CD4+ T-cell count is not the sole cause of higher susceptibility, because HIV-infected persons with a high peripheral CD4+ T-cell count and those prescribed successful antiretroviral therapy (ART) remain more prone to active tuberculosis than HIV-uninfected persons. We hypothesized that the increase in susceptibility is caused by the ability of HIV to manipulate Mycobacterium tuberculosis-associated granulomas.

METHODS

 We examined 71 excised cervical lymph nodes (LNs) from persons with HIV and M. tuberculosis coinfection, those with HIV monoinfection, and those with M. tuberculosis monoinfection with a spectrum of peripheral CD4+ T-cell counts and ART statuses. We quantified differences in M. tuberculosis levels, HIV p24 levels, cellular response, and cytokine presence within granulomas.

RESULTS

 HIV increased M. tuberculosis numbers and reduced CD4+ T-cell counts within granulomas. Peripheral CD4+ T-cell depletion correlated with granulomas that contained fewer CD4+ and CD8+ T cells, less interferon γ, more neutrophils, more interleukin 10 (IL-10), and increased M. tuberculosis numbers. M. tuberculosis numbers correlated positively with IL-10 and interferon α levels and fewer CD4+ and CD8+ T cells. ART reduced IL-10 production.

CONCLUSIONS

 Peripheral CD4+ T-cell depletion correlated with increased M. tuberculosis presence, increased IL-10 production, and other phenotypic changes within granulomas, demonstrating the HIV infection progressively changes these granulomas.

Autophagy induction targeting mTORC1 enhances Mycobacterium tuberculosis replication in HIV co-infected human macrophages

To survive and replicate in macrophages Mycobacterium tuberculosis (Mtb) has developed strategies to subvert host defence mechanisms, including autophagy. Autophagy induction has the potential to clear Mtb, but little is known about its effect during controlled tuberculosis and HIV co-infection. Mammalian target of rapamycin complex1 (mTORC1) inhibitors were used to induce autophagy in human macrophages pre-infected with HIV-1_BaL and infected with a low dose of Mtb (co-infected), or single Mtb infected (single infected). The controlled Mtb infection was disrupted upon mTOR inhibition resulting in increased Mtb replication in a dose-dependent manner which was more pronounced during co-infection. The increased Mtb replication could be explained by the marked reduction in phagosome acidification upon mTOR inhibition. Autophagy stimulation targeting mTORC1 clearly induced a basal autophagy with flux that was unlinked to the subcellular environment of the Mtb vacuoles, which showed a concurrent suppression in acidification and maturation/flux. Overall our findings indicate that mTOR inhibition during Mtb or HIV/Mtb co-infection interferes with phagosomal maturation, thereby supporting mycobacterial growth during low-dose and controlled infection. Therefore pharmacological induction of autophagy through targeting of the canonical mTORC1-pathway should be handled with caution during controlled tuberculosis, since this could have serious consequences for patients with HIV/Mtb co-infection.

Understanding HIV-Mycobacteria synergism through comparative proteomics of intra-phagosomal mycobacteria during mono- and HIV co-infection

Mycobacterium tuberculosis (Mtb) is the most common co-infection in HIV patients and a serious co-epidemic. Apart from increasing the risk of reactivation of latent tuberculosis (TB), HIV infection also permits opportunistic infection of environmental non-pathogenic mycobacteria. To gain insights into mycobacterial survival inside host macrophages and identify mycobacterial proteins or processes that influence HIV propagation during co-infection, we employed proteomics approach to identify differentially expressed intracellular mycobacterial proteins during mono- and HIV co-infection of human THP-1 derived macrophage cell lines. Of the 92 proteins identified, 30 proteins were upregulated during mycobacterial mono-infection and 40 proteins during HIV-mycobacteria co-infection. We observed down-regulation of toxin-antitoxin (TA) modules, up-regulation of cation transporters, Type VII (Esx) secretion systems, proteins involved in cell wall lipid or protein metabolism, glyoxalate pathway and branched chain amino-acid synthesis during co-infection. The bearings of these mycobacterial factors or processes on HIV propagation during co-infection, as inferred from the proteomics data, were validated using deletion mutants of mycobacteria. The analyses revealed mycobacterial factors that possibly via modulating the host environment, increased viral titers during co-infection. The study provides new leads for investigations towards hitherto unknown molecular mechanisms explaining HIV-mycobacteria synergism, helping address diagnostics and treatment challenges for effective co-epidemic management.

Interleukin-17 mediated differences in the pathogenesis of HIV-1-associated tuberculous and cryptococcal meningitis

OBJECTIVE

Mycobacterium tuberculosis and Cryptococcus neoformans are major causes of meningitis in HIV-1-infected patients. Identifying differences in the inflammatory profiles of HIV-1-associated tuberculous meningitis (TBM) and cryptococcal meningitis may inform differences in immunopathogenic mechanisms in these diseases. In this study we compared the clinical and inflammatory features of HIV-1-associated TBM, and cryptococcal meningitis.

METHODS

A prospective study of HIV-1-infected adults who presented with either TBM [antiretroviral therapy (ART)-naive] or cryptococcal meningitis (regardless of ART prescription). Clinical and laboratory findings and concentrations of 40 inflammatory mediators measured in cerebrospinal fluid (CSF, 33 paired with blood) were compared between TBM and cryptococcal meningitis patients regardless of ART prescription and between TBM and cryptococcal meningitis patients not receiving ART.

RESULTS

Clinical and laboratory findings were similar in TBM (n=34) and cryptococcal meningitis (n = 19; ART prescribed: n = 10, no ART prescribed: n = 9). Exceptions included a higher median CD4 cell count [interquartile: 113 (69-199) vs. 25 (8-49) cells/μl, P = 0.0001] and higher HIV-1 median viral load [plasma: 5.46 (4.82-5.89) vs. 4.87 (4.36-5.17) log10copies/ml, P = 0.037; CSF: 6.05 (5.43-6.56) vs. 5.56 (4.52-5.80) log10copies/ml, P = 0.03] in TBM vs. cryptococcal meningitis patients not receiving ART. CSF interleukin (IL)-17A was lower in TBM compared with cryptococcal meningitis [1.00 (0.25-2.35) vs. 9.31 (1.24-23.36) pg/ml, P-adjusted = 0.03].

CONCLUSION

Despite presenting with higher peripheral CD4 cell counts, TBM patients also presented with higher HIV-1 viral loads compared with cryptococcal meningitis patients, suggesting a greater propensity of M. tuberculosis compared with C. neoformans to increase HIV-1 replication in vivo. CSF IL-17A was lower in TBM; its role in the immunopathogenesis of TBM and cryptococcal meningitis deserves further research.

HIV-1 Tat regulates the expression of the dcw operon and stimulates the proliferation of bacteria

Infections of pathogenic bacteria are very common in acquired immunodeficiency syndrome (AIDS) patients. However, the biological effects of HIV-1 Tat on bacteria are incompletely understood. In this study, HIV-1 Tat was expressed in Escherichia coli and Pseudomonas aeruginosa (PA01) to investigate its biological effects on bacteria. Bacterial cells expressing either HIV-1 Tat1-86 (Tat1-86) or HIV-1 Tat1-72 (Tat1-72) grow significantly faster than those with either only an empty vector or an unrelated control (GFP or Rluc). Supplementation of purified HIV-1 Tat1-86 or Tat1-101 protein into bacterial culture medium stimulated the growth of both E. coli and PA01. The expression profile of certain cell division-associated genes, such as those in the division cell wall (dcw) operon (ftsA, ftsQ, ftsW and ftsZ), yafO and zipA, was altered in HIV-1 Tat1-86 expressing E. coli BL21(DE3). Furthermore, the expression of firefly luciferase (Fluc) reporter gene, when engineered for control by the dcw promoter and terminator, was enhanced by HIV-1 Tat in E. coli, confirming that HIV-1 Tat transcriptionally regulates the expression of the dcw operon. The finding that HIV-1 Tat stimulates bacterial growth whether it is produced intracellularly or applied extracellularly may have relevance for HIV patients who are highly susceptible to opportunistic bacterial infections. Contents category: Viruses -Retroviruses. The GenBank accession number for the sequence of HIV-1 Tat1-86 is AF324439.1.

Tuberculosis and HIV Coinfection

Tuberculosis (TB) and human immunodeficiency virus/acquired immunodeficiency syndrome (HIV/AIDS) constitute the main burden of infectious disease in resource-limited countries. In the individual host, the two pathogens, Mycobacterium tuberculosis and HIV, potentiate one another, accelerating the deterioration of immunological functions. In high-burden settings, HIV coinfection is the most important risk factor for developing active TB, which increases the susceptibility to primary infection or reinfection and also the risk of TB reactivation for patients with latent TB. M. tuberculosis infection also has a negative impact on the immune response to HIV, accelerating the progression from HIV infection to AIDS. The clinical management of HIV-associated TB includes the integration of effective anti-TB treatment, use of concurrent antiretroviral therapy (ART), prevention of HIV-related comorbidities, management of drug cytotoxicity, and prevention/treatment of immune reconstitution inflammatory syndrome (IRIS).

Anti-Inflammatory and Antimicrobial Actions of Vitamin D in Combating TB/HIV

TUBERCULOSIS (TB) DISEASE ACTIVATION IS NOW BELIEVED TO ARISE DUE TO A LACK OF INFLAMMATORY HOMEOSTATIC CONTROL AT EITHER END OF THE SPECTRUM OF INFLAMMATION: either due to immunosuppression (decreased antimicrobial activity) or due to immune activation (excess/aberrant inflammation). Vitamin D metabolites can increase antimicrobial activity in innate immune cells, which, in the context of HIV-1 coinfection, have insufficient T cell-mediated help to combat Mycobacterium tuberculosis (MTB) infection. Moreover, maintaining vitamin D sufficiency prior to MTB infection enhances the innate antimicrobial response to T cell-mediated interferon-γ. Conversely, vitamin D can act to inhibit expression and secretion of a broad range of inflammatory mediators and matrix degrading enzymes driving immunopathology during active TB and antiretroviral- (ARV-) mediated immune reconstitution inflammatory syndrome (IRIS). Adjunct vitamin D therapy during treatment of active TB may therefore reduce lung pathology and TB morbidity, accelerate resolution of cavitation and thereby decrease the chance of transmission, improve lung function following therapy, prevent relapse, and prevent IRIS in those initiating ARVs. Future clinical trials of vitamin D for TB prevention and treatment must be designed to detect the most appropriate primary endpoint, which in some cases should be anti-inflammatory and not antimicrobial.

In vitro model of mycobacteria and HIV-1 co-infection for drug discovery

Tuberculosis (TB) has become a global health threat in the wake of the Human Immunodeficiency Virus (HIV) pandemic and is the leading cause of death in people with HIV/AIDS. Treatment of patients with Mycobacterium tuberculosis (Mtb)/HIV co-infection is complicated by drug interactions and toxicity that present huge challenges for clinical intervention. Discovery efforts to identify novel compounds with increased effectiveness and decreased drug-drug interactions against Mtb, HIV-1, or both, would be greatly aided by the use of a co-infection model for screening drug libraries. Currently, inhibitors of Mtb are screened independently in mycobacterial cell cultures or target based biochemical screens and less often in macrophages or peripheral blood leukocytes. Similarly, HIV-1 drugs are screened in vitro independently from anti-mycobacterial compounds. Here, we describe an in vitro model where primary human peripheral blood mononuclear cells or monocyte-derived macrophages are infected with Mycobacterium bovis BCG and HIV-1, and used to evaluate drug toxicity and activity in a co-infection setting. Our results with standard compounds (e.g. Azidothymidine, Rifampicin) demonstrate the utility of this in vitro model to evaluate drug effectiveness relevant to cellular toxicity, HIV-1 replication, and intracellular mycobacterial growth, through the use of ELISA, bacterial enumeration, and multi-variate flow cytometry. This model and associated assays have great value in accelerating the discovery of compounds for use in Mtb/HIV-1 co-infected patients.

Magnetic barcode assay for genetic detection of pathogens

The task of rapidly identifying patients infected with Mycobacterium tuberculosis in resource-constrained environments remains a challenge. A sensitive and robust platform that does not require bacterial isolation or culture is critical in making informed diagnostic and therapeutic decisions. Here we introduce a platform for the detection of nucleic acids based on a magnetic barcoding strategy. PCR-amplified mycobacterial genes are sequence-specifically captured on microspheres, labelled by magnetic nanoprobes and detected by nuclear magnetic resonance. All components are integrated into a single, small fluidic cartridge for streamlined on-chip operation. We use this platform to detect M. tuberculosis and identify drug-resistance strains from mechanically processed sputum samples within 2.5 h. The specificity of the assay is confirmed by detecting a panel of clinically relevant non-M. tuberculosis bacteria, and the clinical utility is demonstrated by the measurements in M. tuberculosis-positive patient specimens. Combined with portable systems, the magnetic barcode assay holds promise to become a sensitive, high-throughput and low-cost platform for point-of-care diagnostics.

HIV-Mycobacterium tuberculosis co-infection: a 'danger-couple model' of disease pathogenesis

Tuberculosis (TB) and human immunodeficiency virus (HIV) infection interfere and impact the pathogenesis phenomena of each other. Owing to atypical clinical presentations and diagnostic complications, HIV/TB co-infection continues to be a menace for healthcare providers. Although the increased access to highly active antiretroviral therapy (HAART) has led to a reduction in HIV-associated opportunistic infections and mortality, the concurrent management of HIV/TB co-infection remains a challenge owing to adverse effects, complex drug interactions, overlapping toxicities and tuberculosis -associated immune reconstitution inflammatory syndrome. Several hypotheses have been put forward for the exacerbation of tuberculosis by HIV and vice versa supported by immunological studies. Discussion on the mechanisms produced by infectious cofactors with impact on disease pathology could shed light on how to design potential interventions that could decelerate disease progression. With no vaccine for HIV and lack of an effective vaccine for tuberculosis, it is essential to design strategies against HIV-TB co-infection.

HIV-1 infection of macrophages dysregulates innate immune responses to Mycobacterium tuberculosis by inhibition of interleukin-10

Human immunodeficiency virus (HIV)-1 and Mycobacterium tuberculosis (M. tuberculosis) both target macrophages, which are key cells in inflammatory responses and their resolution. Therefore, we tested the hypothesis that HIV-1 may modulate macrophage responses to coinfection with M. tuberculosis. HIV-1 caused exaggerated proinflammatory responses to M. tuberculosis that supported enhanced virus replication, and were associated with deficient stimulus-specific induction of anti-inflammatory interleukin (IL)-10 and attenuation of mitogen-activated kinase signaling downstream of Toll-like receptor 2 and dectin-1 stimulation. Our in vitro data were mirrored by lower IL-10 and higher proinflammatory IL-1β in airway samples from HIV-1-infected patients with pulmonary tuberculosis compared with those with non-tuberculous respiratory tract infections. Single-round infection of macrophages with HIV-1 was sufficient to attenuate IL-10 responses, and antiretroviral treatment of replicative virus did not affect this phenotype. We propose that deficient homeostatic IL-10 responses may contribute to the immunopathogenesis of active tuberculosis and propagation of virus infection in HIV-1/M. tuberculosis coinfection.

The immune response in tuberculosis

There are 9 million cases of active tuberculosis reported annually; however, an estimated one-third of the world's population is infected with Mycobacterium tuberculosis and remains asymptomatic. Of these latent individuals, only 5-10% will develop active tuberculosis disease in their lifetime. CD4(+) T cells, as well as the cytokines IL-12, IFN-γ, and TNF, are critical in the control of Mycobacterium tuberculosis infection, but the host factors that determine why some individuals are protected from infection while others go on to develop disease are unclear. Genetic factors of the host and of the pathogen itself may be associated with an increased risk of patients developing active tuberculosis. This review aims to summarize what we know about the immune response in tuberculosis, in human disease, and in a range of experimental models, all of which are essential to advancing our mechanistic knowledge base of the host-pathogen interactions that influence disease outcome.

Heme oxygenase-1 induction alters chemokine regulation and ameliorates human immunodeficiency virus-type-1 infection in lipopolysaccharide-stimulated macrophages

We have elucidated a putative mechanism for the host resistance against HIV-1 infection of primary human monocyte-derived macrophages (MDM) stimulated with lipopolysaccharide (LPS). We show that LPS-activated MDM both inhibited HIV-1 entry into the cells and were refractory to post-entry productive viral replication. LPS-treated cells were virtually negative for mature virions as revealed by transmission electron microscopy. LPS activation of MDM markedly enhanced the expression of heme oxygenase-1 (HO-1), a potent inducible cytoprotective enzyme. Increased HO-1 expression was accompanied by elevated production of macrophage inflammatory chemokines (MIP1α and MIP1β) by LPS-activated MDM, significantly decreased surface chemokine receptor-5 (CCR-5) expression, and substantially reduced virus replication. Treatment of cells with HO-1 inhibitor SnPP IX (tin protoporphyrin IX) attenuated the LPS-mediated responses, HIV-1 replication and secretion of MIP1α, MIP1β, and LD78β chemokines with little change in surface CCR-5 expression. These results identify a novel role for HO-1 in the modulation of host immune response against HIV infection of MDM.

HIV-1 and the immune response to TB

TB causes 1.4 million deaths annually. HIV-1 infection is the strongest risk factor for TB. The characteristic immunological effect of HIV is on CD4 cell count. However, the risk of TB is elevated in HIV-1 infected individuals even in the first few years after HIV acquisition and also after CD4 cell counts are restored with antiretroviral therapy. In this review, we examine features of the immune response to TB and how this is affected by HIV-1 infection and vice versa. We discuss how the immunology of HIV-TB coinfection impacts on the clinical presentation and diagnosis of TB, and how antiretroviral therapy affects the immune response to TB, including the development of TB immune reconstitution inflammatory syndrome. We highlight important areas of uncertainty and future research needs.

Mycobacteria-infected bystander macrophages trigger maturation of dendritic cells and enhance their ability to mediate HIV transinfection

Synergistic interplay between Mycobacterium tuberculosis (Mtb) and HIV in coinfected individuals leads to the acceleration of both tuberculosis and HIV disease. Mtb, as well as HIV, may modulate the function of many immune cells, including DCs. To dissect the bystander impact of Mφs infected with Mtb on DC functionality, we here investigated changes in DC phenotype, cytokine profiles, and HIV-1 transinfecting ability. An in vitro system was used in which human monocyte-derived DCs were exposed to soluble factors released by Mφs infected with mycobacteria, including virulent clinical Mtb isolates and nonvirulent BCG. Soluble factors secreted from Mtb-infected Mφs, and to a lesser extent BCG-infected Mφs, resulted in the production of proinflammatory cytokines and partial upregulation of DC maturation markers. Interestingly, the HIV-1 transinfecting ability of DCs was enhanced upon exposure to soluble factors released by Mtb-infected Mφs. In summary, our study shows that DCs exposed to soluble factors released by mycobacteria-infected Mφs undergo maturation and display an augmented ability to transmit HIV-1 in trans. These findings highlight the important role of bystander effects during the course of Mtb-HIV coinfection and suggest that Mtb-infected Mφs may contribute to an environment that supports DC-mediated spread and amplification of HIV in coinfected individuals.

Counting mycobacteria in infected human cells and mouse tissue: a comparison between qPCR and CFU

Due to the slow growth rate and pathogenicity of mycobacteria, enumeration by traditional reference methods like colony counting is notoriously time-consuming, inconvenient and biohazardous. Thus, novel methods that rapidly and reliably quantify mycobacteria are warranted in experimental models to facilitate basic research, development of vaccines and anti-mycobacterial drugs. In this study we have developed quantitative polymerase chain reaction (qPCR) assays for simultaneous quantification of mycobacterial and host DNA in infected human macrophage cultures and in mouse tissues. The qPCR method cannot discriminate live from dead bacteria and found a 10- to 100-fold excess of mycobacterial genomes, relative to colony formation. However, good linear correlations were observed between viable colony counts and qPCR results from infected macrophage cultures (Pearson correlation coefficient [r] for M. tuberculosis = 0.82; M. a. avium = 0.95; M. a. paratuberculosis = 0.91). Regression models that predict colony counts from qPCR data in infected macrophages were validated empirically and showed a high degree of agreement with observed counts. Similar correlation results were also obtained in liver and spleen homogenates of M. a. avium infected mice, although the correlations were distinct for the early phase (< day 9 post-infection) and later phase (≥ day 20 post-infection) liver r = 0.94 and r = 0.91; spleen r = 0.91 and r = 0.87, respectively. Interestingly, in the mouse model the number of live bacteria as determined by colony counts constituted a much higher proportion of the total genomic qPCR count in the early phase (geometric mean ratio of 0.37 and 0.34 in spleen and liver, respectively), as compared to later phase of infection (geometric mean ratio of 0.01 in both spleen and liver). Overall, qPCR methods offer advantages in biosafety, time-saving, assay range and reproducibility compared to colony counting. Additionally, the duplex format allows enumeration of bacteria per host cell, an advantage in experiments where variable cell death can give misleading colony counts.

Leishmania induces survival, proliferation and elevated cellular dNTP levels in human monocytes promoting acceleration of HIV co-infection

Leishmaniasis is a parasitic disease that is widely prevalent in many tropical and sub-tropical regions of the world. Infection with Leishmania has been recognized to induce a striking acceleration of Human Immunodeficiency Virus Type 1 (HIV-1) infection in coinfected individuals through as yet incompletely understood mechanisms. Cells of the monocyte/macrophage lineage are the predominant cell types coinfected by both pathogens. Monocytes and macrophages contain extremely low levels of deoxynucleoside triphosphates (dNTPs) due to their lack of cell cycling and S phase, where dNTP biosynthesis is specifically activated. Lentiviruses, such as HIV-1, are unique among retroviruses in their ability to replicate in these non-dividing cells due, at least in part, to their highly efficient reverse transcriptase (RT). Nonetheless, viral replication progresses more efficiently in the setting of higher intracellular dNTP concentrations related to enhanced enzyme kinetics of the viral RT. In the present study, in vitro infection of CD14+ peripheral blood-derived human monocytes with Leishmania major was found to induce differentiation, marked elevation of cellular p53R2 ribonucleotide reductase subunit and R2 subunit expression. The R2 subunit is restricted to the S phase of the cell cycle. Our dNTP assay demonstrated significant elevation of intracellular monocyte-derived macrophages (MDMs) dNTP concentrations in Leishmania-infected cell populations as compared to control cells. Infection of Leishmania-maturated MDMs with a pseudotyped GFP expressing HIV-1 resulted in increased numbers of GFP+ cells in the Leishmania-maturated MDMs as compared to control cells. Interestingly, a sub-population of Leishmania-maturated MDMs was found to have re-entered the cell cycle, as demonstrated by BrdU labeling. In conclusion, Leishmania infection of primary human monocytes promotes the induction of an S phase environment and elevated dNTP levels with notable elevation of HIV-1 expression in the setting of coinfection.

Leishmaniasis is a parasitic disease that infects several human host immune cells, including neutrophils, monocytes, and macrophages. Moreover, while HIV-1 infects monocytes and macrophages, only the infected macrophages productively release viral progenies. Importantly, patients coinfected with both pathogens progress more rapidly to AIDS. In this study, we examine how Leishmania major changes the cellular environment of monocytes in vitro. We found that Leishmania-infected monocytes actively mature into macrophages in the absence of GM-CSF, and that these cells up-regulate the expression of ribonucleotide reductase, an enzyme that catalyzes the formation of deoxynucleoside triphosphates (dNTPs). We confirmed the elevation of dNTP concentrations using a very sensitive dNTP assay for monocytes and monocyte-maturated macrophages. Collectively, these data support a model in which infection of monocytes with Leishmania elevates the intracellular dNTP pools, which is one of the natural anti-viral blocks to HIV-1 infection in monocytes and macrophages in patients.

A comparative study of Mycobacterium avium subsp. avium and Mycobacterium avium subsp. hominissuis in experimentally infected pigs

Background

Mycobacterium avium subsp. avium (Maa) and Mycobacterium avium subsp. hominissuis (Mah) are opportunistic pathogens that may infect several species, including humans and pigs. Mah is however more frequently isolated from pigs than Maa, and it is unclear if this is due to difference in virulence or in exposure to the two organisms. Clinical isolates of each subspecies were administered perorally to ten domestic pigs, respectively. The animals were sacrificed at six and 12 weeks after inoculation. At necropsy, macroscopic lesions were recorded, and tissue samples were collected for mycobacterial culture, IS1245 real time PCR and histopathological examination. Culturing was also performed on faecal samples collected at necropsy.

Results

Macroscopic and histopathological lesions were detected in pigs infected with each subspecies, and bacterial growth and histopathological changes were demonstrated, also in samples from organs without gross pathological lesions. Six weeks after inoculation, live Mah was detected in faeces, as opposed to Maa. The presence of live mycobacteria was also more pronounced in Mah infected tonsils. In comparison, the Maa isolate appeared to have a higher ability of intracellular replication in porcine macrophages compared to the Mah isolate.

Conclusions

The study shows that both subspecies were able to infect pigs. Additionally, the more extensive shedding of Mah might cause pig-to-pig transmission and contribute to the higher incidence of infection caused by this subspecies.

HIV-1 and the macrophage

Macrophages and CD4+ T cells are natural target cells for HIV-1, and both cell types contribute to the establishment of the viral reservoir that is responsible for continuous residual virus replication during antiretroviral therapy and viral load rebound upon treatment interruption. Scientific findings that support a critical role for the infected monocyte/macrophage in HIV-1-associated diseases, such as neurological disorders and cardiovascular disease, are accumulating. To prevent or treat these HIV-1-related diseases, we need to halt HIV-1 replication in the macrophage reservoir. This article describes our current knowledge of how monocytes and certain macrophage subsets are able to restrict HIV-1 infection, in addition to what makes macrophages respond less well to current antiretroviral drugs as compared with CD4+ T cells. These insights will help to find novel approaches that can be used to meet this challenge.