Interaction of Bartonella bacilliformis with human erythrocyte membrane proteins

Sneaky tactics: Ingenious immune evasion mechanisms of Bartonella

Gram-negative Bartonella species are facultative intracellular bacteria that can survive in the harsh intracellular milieu of host cells. They have evolved strategies to evade detection and degradation by the host immune system, which ensures their proliferation in the host. Following infection, Bartonella alters the initial immunogenic surface-exposed proteins to evade immune recognition via antigen or phase variation. The diverse lipopolysaccharide structures of certain Bartonella species allow them to escape recognition by the host pattern recognition receptors. Additionally, the survival of mature erythrocytes and their resistance to lysosomal fusion further complicate the immune clearance of this species. Certain Bartonella species also evade immune attacks by producing biofilms and anti-inflammatory cytokines and decreasing endothelial cell apoptosis. Overall, these factors create a challenging landscape for the host immune system to rapidly and effectively eradicate the Bartonella species, thereby facilitating the persistence of Bartonella infections and creating a substantial obstacle for therapeutic interventions. This review focuses on the effects of three human-specific Bartonella species, particularly their mechanisms of host invasion and immune escape, to gain new perspectives in the development of effective diagnostic tools, prophylactic measures, and treatment options for Bartonella infections.

Carrion's disease: more than a neglected disease

Infections with Bartonella bacilliformis result in Carrion's disease in humans. In the first phase of infection, the pathogen causes a hemolytic fever ("Oroya fever") with case-fatality rates as high as ~90% in untreated patients, followed by a chronical phase resulting in angiogenic skin lesions ("verruga peruana"). Bartonella bacilliformis is endemic to South American Andean valleys and is transmitted via sand flies (Lutzomyia spp.). Humans are the only known reservoir for this old disease and therefore no animal infection model is available. In the present review, we provide the current knowledge on B. bacilliformis and its pathogenicity factors, vectors, possible unknown reservoirs, established and potential infection models and immunological aspects of the disease.

Molecular Mechanisms of Bartonella and Mammalian Erythrocyte Interactions: A Review

Bartonellosis is an infectious disease caused by Bartonella species that are distributed worldwide with animal and public health impact varying according to Bartonella species, infection phase, immunological characteristics, and geographical region. Bartonella is widely present in various mammals including cats, rodents, ruminants, and humans. At least 13 Bartonella species or subspecies are zoonotic. Each species has few reservoir animals in which it is often asymptomatic. Bartonella infection may lead to various clinical symptoms in humans. As described in the B.tribocorum-rat model, when Bartonella was seeded into the blood stream, they could escape immunity, adhered to and invaded host erythrocytes. They then replicated and persisted in the infected erythrocytes for several weeks. This review summarizes the current knowledge of how Bartonella prevent phagocytosis and complement activation, what pathogenesis factors are involved in erythrocyte adhesion and invasion, and how Bartonella could replicate and persist in mammalian erythrocytes. Current advances in research will help us to decipher molecular mechanisms of interactions between Bartonella and mammalian erythrocytes and may help in the development of biological strategies for the prevention and control of bartonellosis.

Carrion's Disease: the Sound of Silence

Carrion's disease (CD) is a neglected biphasic vector-borne illness related to Bartonella bacilliformis. It is found in the Andean valleys and is transmitted mainly by members of the Lutzomyia genus but also by blood transfusions and from mother to child. The acute phase, Oroya fever, presents severe anemia and fever. The lethality is high in the absence of adequate treatment, despite the organism being susceptible to most antibiotics. Partial immunity is developed after infection by B. bacilliformis, resulting in high numbers of asymptomatic carriers. Following infection there is the chronic phase, Peruvian warts, involving abnormal proliferation of the endothelial cells. Despite potentially being eradicable, CD has been expanded due to human migration and geographical expansion of the vector. Moreover, in vitro studies have demonstrated the risk of the development of antimicrobial resistance. These findings, together with the description of new Bartonella species producing CD-like infections, the presence of undescribed potential vectors in new areas, the lack of adequate diagnostic tools and knowledge of the immunology and bacterial pathogenesis of CD, and poor international visibility, have led to the risk of increasing the potential expansion of resistant strains which will challenge current treatment schemes as well as the possible appearance of CD in areas where it is not endemic.

Proteins of Bartonella bacilliformis: Candidates for Vaccine Development

Bartonella bacilliformis is the etiologic agent of Carrión's disease or Oroya fever. B. bacilliformis infection represents an interesting model of human host specificity. The notable differences in clinical presentations of Carrión's disease suggest complex adaptations by the bacterium to the human host, with the overall objectives of persistence, maintenance of a reservoir state for vectorial transmission, and immune evasion. These events include a multitude of biochemical and genetic mechanisms involving both bacterial and host proteins. This review focuses on proteins involved in interactions between B. bacilliformis and the human host. Some of them (e.g., flagellin, Brps, IalB, FtsZ, Hbp/Pap31, and other outer membrane proteins) are potential protein antigen candidates for a synthetic vaccine.

Blood Groups in Infection and Host Susceptibility

Blood group antigens represent polymorphic traits inherited among individuals and populations. At present, there are 34 recognized human blood groups and hundreds of individual blood group antigens and alleles. Differences in blood group antigen expression can increase or decrease host susceptibility to many infections. Blood groups can play a direct role in infection by serving as receptors and/or coreceptors for microorganisms, parasites, and viruses. In addition, many blood group antigens facilitate intracellular uptake, signal transduction, or adhesion through the organization of membrane microdomains. Several blood groups can modify the innate immune response to infection. Several distinct phenotypes associated with increased host resistance to malaria are overrepresented in populations living in areas where malaria is endemic, as a result of evolutionary pressures. Microorganisms can also stimulate antibodies against blood group antigens, including ABO, T, and Kell. Finally, there is a symbiotic relationship between blood group expression and maturation of the gastrointestinal microbiome.

Frequencies of Blood Group Systems MNS, Diego, and Duffy and Clinical Phases of Carrion's Disease in Amazonas, Peru

Carrion's disease (CD), is a human bartonellosis, that is, endemic in the Andes of Peru, Ecuador, and Colombia. Bartonella bacilliformis, a native hemotrophic bacteria, is the causative agent of CD, and the interaction with the host could have produced changes in the gene frequencies of erythrocyte antigens. The goal here is to investigate the relationship between allele frequencies of blood group systems MNS, Diego, and Duffy and the clinical phases of CD, within a genetic context. In this associative and analytical study, 76 individuals from Bagua Grande, the province of Utcubamba, and the department of Amazonas in Peru, were enrolled. Forty of them resided in Tomocho-Collicate-Vista Hermosa area (high prevalence of cases in chronic phase, verrucous, or eruptive phase, without previous acute phase). Thirty-six individuals were from the area of Miraflores (high prevalence of cases in acute phase only) and were evaluated for blood group systems MNS, Diego, and Duffy. This study constitutes one of the first attempts at evaluating the genetic factors and clinical phases of CD. No significant statistical differences (P > 0.05) between allele frequencies of blood groups MNS, Diego, and Duffy and the prevalence of chronic and acute phases were detected in the two areas of Amazonas, Peru.

Bartonella and Brucella--weapons and strategies for stealth attack

Bartonella spp. and Brucella spp. are closely related α-proteobacterial pathogens that by distinct stealth-attack strategies cause chronic infections in mammals including humans. Human infections manifest by a broad spectrum of clinical symptoms, ranging from mild to fatal disease. Both pathogens establish intracellular replication niches and subvert diverse pathways of the host's immune system. Several virulence factors allow them to adhere to, invade, proliferate, and persist within various host-cell types. In particular, type IV secretion systems (T4SS) represent essential virulence factors that transfer effector proteins tailored to recruit host components and modulate cellular processes to the benefit of the bacterial intruders. This article puts the remarkable features of these two pathogens into perspective, highlighting the mechanisms they use to hijack signaling and trafficking pathways of the host as the basis for their stealthy infection strategies.

Identification of Bartonella Trw host-specific receptor on erythrocytes

Each Bartonella species appears to be highly adapted to one or a limited number of reservoir hosts, in which it establishes long-lasting intraerythrocytic bacteremia as the hallmark of infection. Recently, we identified Trw as the bacterial system involved in recognition of erythrocytes according to their animal origin. The T4SS Trw is characterized by a multiprotein complex that spans the inner and outer bacterial membranes, and possesses a hypothetical pilus structure. TrwJ, I, H and trwL are present in variable copy numbers in different species and the multiple copies of trwL and trwJ in the Bartonella trw locus are considered to encode variant forms of surface-exposed pilus components. We therefore aimed to identify which of the candidate Trw pilus components were located on the bacterial surface and involved in adhesion to erythrocytes, together with their erythrocytic receptor. Using different technologies (electron microscopy, phage display, invasion inhibition assay, far western blot), we found that only TrwJ1 and TrwJ2 were expressed and localized at the cell surface of B. birtlesii and had the ability to bind to mouse erythrocytes, and that their receptor was band3, one of the major outer-membrane glycoproteins of erythrocytes, (anion exchanger). According to these results, we propose that the interaction between TrwJ1, TrwJ2 and band 3 leads to the critical host-specific adherence of Bartonella to its host cells, erythrocytes.

Persistence of Bartonella spp. stealth pathogens: from subclinical infections to vasoproliferative tumor formation

Bartonella spp. are facultative intracellular bacteria that typically cause a long-lasting intraerythrocytic bacteremia in their mammalian reservoir hosts, thereby favoring transmission by blood-sucking arthropods. In most cases, natural reservoir host infections are subclinical and the relapsing intraerythrocytic bacteremia may last weeks, months, or even years. In this review, we will follow the infection cycle of Bartonella spp. in a reservoir host, which typically starts with an intradermal inoculation of bacteria that are superficially scratched into the skin from arthropod feces and terminates with the pathogen exit by the blood-sucking arthropod. The current knowledge of bacterial countermeasures against mammalian immune response will be presented for each critical step of the pathogenesis. The prevailing models of the still-enigmatic primary niche and the anatomical location where bacteria reside, persist, and are periodically seeded into the bloodstream to cause the typical relapsing Bartonella spp. bacteremia will also be critically discussed. The review will end up with a discussion of the ability of Bartonella spp., namely Bartonella henselae, Bartonella quintana, and Bartonella bacilliformis, to induce tumor-like vascular deformations in humans having compromised immune response such as in patients with AIDS.

Intruders below the radar: molecular pathogenesis of Bartonella spp

Bartonella spp. are facultative intracellular pathogens that employ a unique stealth infection strategy comprising immune evasion and modulation, intimate interaction with nucleated cells, and intraerythrocytic persistence. Infections with Bartonella are ubiquitous among mammals, and many species can infect humans either as their natural host or incidentally as zoonotic pathogens. Upon inoculation into a naive host, the bartonellae first colonize a primary niche that is widely accepted to involve the manipulation of nucleated host cells, e.g., in the microvasculature. Consistently, in vitro research showed that Bartonella harbors an ample arsenal of virulence factors to modulate the response of such cells, gain entrance, and establish an intracellular niche. Subsequently, the bacteria are seeded into the bloodstream where they invade erythrocytes and give rise to a typically asymptomatic intraerythrocytic bacteremia. While this course of infection is characteristic for natural hosts, zoonotic infections or the infection of immunocompromised patients may alter the path of Bartonella and result in considerable morbidity. In this review we compile current knowledge on the molecular processes underlying both the infection strategy and pathogenesis of Bartonella and discuss their connection to the clinical presentation of human patients, which ranges from minor complaints to life-threatening disease.

Cytokines and T-Lymphocute count in patients in the acute and chronic phases of Bartonella bacilliformis infection in an endemic area in peru: a pilot study

Human Bartonellosis has an acute phase characterized by fever and hemolytic anemia, and a chronic phase with bacillary angiomatosis-like lesions. This cross-sectional pilot study evaluated the immunology patterns using pre- and post-treatment samples in patients with Human Bartonellosis. Patients between five and 60 years of age, from endemic areas in Peru, in the acute or chronic phases were included. In patients in the acute phase of Bartonellosis a state of immune peripheral tolerance should be established for persistence of the infection. Our findings were that elevation of the anti-inflammatory cytokine IL-10 and numeric abnormalities of CD4(+) and CD8(+) T-Lymphocyte counts correlated significantly with an unfavorable immune state. During the chronic phase, the elevated levels of IFN-γ and IL-4 observed in our series correlated with previous findings of endothelial invasion of B. henselae in animal models.

Pestilence, persistence and pathogenicity: infection strategies of Bartonella

It has been nearly two decades since the discovery of Bartonella as an agent of bacillary angiomatosis in AIDS patients and persistent bacteremia and 'nonculturable' endocarditis in homeless people. Since that time, the number of Bartonella species identified has increased from one to 24, and 10 of these bacteria are associated with human disease. Although Bartonella is the only genus that infects human erythrocytes and triggers pathological angiogenesis in the vascular bed, the group remains understudied compared with most other bacterial pathogens. Numerous questions regarding Bartonella's molecular pathogenesis and epidemiology remain unanswered. Virtually every mammal harbors one or more Bartonella species and their transmission typically involves a hematophagous arthropod vector. However, many details regarding epidemiology and the public health threat imposed by these animal reservoirs is unclear. A handful of studies have shown that bartonellae are highly-adapted pathogens whose parasitic strategy has evolved to cause persistent infections of the host. To this end, virulence attributes of Bartonella include the subversion of host cells with effector molecules delivered via a type IV secretion system, induction of pathological angiogenesis through various means, including inhibition of apoptosis and activation of hypoxia-inducing factor 1, use of afimbrial adhesins that are orthologs of Yersinia adhesin A, incorporation of lipopolysaccharides with low endotoxic potency in the outer membrane, and several other virulence factors that help Bartonella infect and persist in erythrocytes and endothelial cells of the host circulatory system.

Characteristics of new Staphylococcus aureus-RBC adhesion mechanism independent of fibrinogen and IgG under hydrodynamic shear conditions

Staphylococcus aureus infection begins when bacterial cells circulating in blood adhere to components of the extracellular matrix or endothelial cells of the host and initiate colonization. S. aureus is known to exhibit extensive interactions with platelets. S. aureus is also known to bind to red blood cells (RBCs) in the presence of plasma proteins, such as fibrinogen and IgG. Herein we report a new binding mechanism of S. aureus to RBC independent of those plasma proteins. To characterize the new adhesion mechanism, we experimentally examine the binding kinetics and molecular constituents mediating the new adhesive interactions between S. aureus and RBCs under defined shear conditions. The results demonstrate that the receptors for fibrinogen (clumping factor A) and IgG (protein A) of S. aureus are not involved in the adhesion. S. aureus binds to RBCs with maximal adhesion at the shear rate 100 s(-1) and decreasing adhesion with increasing shear. The heteroaggregates formed after shear are stable when subjected to the shear rate 2,000 s(-1), indicating that intercellular contact time rather than shear forces controls the adhesion at high shear. S. aureus binding to RBC requires plasma, and 10% plasma is sufficient for maximal adhesion. Plasma proteins involved in the cell-cell adhesion, such as fibrinogen, fibronectin, von Willebrand factor, IgG, thrombospondin, laminin, and vitronectin are not involved in the observed adhesion. The extent of heteroaggregation is dramatically reduced on RBC treatment with trypsin, chymotrypsin, or neuraminidase, suggesting that the receptor(s) mediating the heteroaggregation process is a sialylated glycoprotein on RBC surface. Adhesion is divalent cation dependent and also blocked by heparin. This work demonstrates a new mechanism of S. aureus-RBC binding under hydrodynamic shear conditions via unknown RBC sialoglycoprotein(s). The binding requires plasma protein(s) other than fibrinogen or IgG and does not involve the S. aureus adhesins clumping factor A or protein A.

Molecular and Cellular Basis ofBartonellaPathogenesis

The genus Bartonella comprises several important human pathogens that cause a wide range of clinical manifestations: cat-scratch disease, trench fever, Carrion's disease, bacteremia with fever, bacillary angiomatosis and peliosis, endocarditis, and neuroretinitis. Common features of bartonellae include transmission by blood-sucking arthropods and the specific interaction with endothelial cells and erythrocytes of their mammalian hosts. For each Bartonella species, the invasion and persistent intracellular colonization of erythrocytes are limited to a specific human or animal reservoir host. In contrast, endothelial cells are target host cells in probably all mammals, including humans. Bartonellae subvert multiple cellular functions of human endothelial cells, resulting in cell invasion, proinflammatory activation, suppression of apoptosis, and stimulation of proliferation, which may cumulate in vasoproliferative tumor growth. This review summarizes our understanding of Bartonella-host cell interactions and the molecular mechanisms of bacterial virulence and persistence. In addition, current controversies and unanswered questions in this area are highlighted.

Bartonella interactions with endothelial cells and erythrocytes

Bartonella species are emerging human pathogens responsible for a wide range of clinical manifestations, including Carrion's disease, trench fever, cat-scratch disease, bacillary angiomatosis-peliosis, endocarditis and bacteraemia. During infection of their human or animal reservoir host(s), these arthropod-borne pathogens typically invade and persistently colonize mature erythrocytes. However, in both reservoir and incidentally infected hosts, endothelial cells are target cells for bartonellae. Endothelial interactions involve a unique mode of cellular invasion, the activation of a proinflammatory phenotype and the formation of vasoproliferative tumours. Based on the establishment of bacterial genetics and appropriate infection models, recent work has begun to elucidate the cell and molecular biology of these unusual pathogen-host cell interactions.