Host immune response to intracellular bacteria: A role for MHC-linked class-Ib antigen-presenting molecules

Pathogenesis of Brucella epididymoorchitis-game of Brucella death

Brucellosis is a worldwide zoonotic disease caused by Brucella spp. Human infection often results from direct contact with tissues from infected animals or by consumption of undercooked meat and unpasteurised dairy products, causing serious economic losses and public health problems. The male genitourinary system is a common involved system in patients with brucellosis. Among them, unilateral orchitis and epididymitis are the most common. Although the clinical and imaging aspect of orchi-epididymitis caused by brucellosis have been widely described, the cellular and molecular mechanisms involved in the damage and the immune response in testis and epididymis have not been fully elucidated. In this review, we first summarised the clinical characteristics of Brucella epididymo-orchitis and the composition of testicular and epididymal immune system. Secondly, with regard to the mechanism of Brucella epididymoorchitis, we mainly discussed the process of Brucella invading testis and epididymis in temporal and spatial order, including i) Brucella evades innate immune recognition of testicular PRRs；ii) Brucella overcomes the immune storm triggered by the invasion of testis through bacterial lipoproteins and virulence factors, and changes the secretion mode of cytokines; iii) Brucella breaks through the blood-testis barrier with the help of macrophages, and inflammatory cytokines promote the oxidative stress of Sertoli cells, damaging the integrity of BTB; iv) Brucella inhibits apoptosis of testicular phagocytes. Finally, we revealed the structure and sequence of testis invaded by Brucella at the tissue level. This review will enable us to better understand the pathogenesis of orchi-epididymitis caused by brucellosis and shed light on the development of new treatment strategies for the treatment of brucellosis and the prevention of transition to chronic form. Facing the testicle with immunity privilege, Brucella is like Bruce Lee in the movie Game of Death, winning is survival while losing is death.HIGHLIGHTSWe summarized the clinical features and pathological changes of Brucellaepididymoorchitis.Our research reveals the pathogenesis of Brucella epididymoorchitis, which mainly includes the subversion of testicular immune privilege by Brucella and a series of destructive reactions derived from it.As a basic framework and valuable resource, this study can promote the exploration of the pathogenesis of Brucella and provide reference for determining new therapeutic targets for brucellosis in the future.

Transcriptome Functional Analysis of Mammary Gland of Cows in Heat Stress and Thermoneutral Condition

Simple Summary

The current study employed RNA-seq technology to analyze the impact of heat stress on the whole transcript sequencing profile in the mammary glands of lactating Holstein dairy cows. In the findings of the current study, heat stress downregulated the expression of casein genes, which resulted in a decrease in milk production. Moreover, heat stress upregulated the gene expression of HSPA1A and HSP90B1, while it downregulated the expression of immune response-related genes that resulted in a reduction in milk yield. Furthermore, there was an increased synthesis of heat shock proteins and unfolded proteins that could reduce the availability of circulating amino acids for milk protein synthesis. The findings of the current experiment may help to explore the impact of heat stress on immune function, milk production, and milk protein synthesis in cows.

Abstract

Heat stress (HS) exerts significant effects on the production of dairy animals through impairing health and biological functions. However, the molecular mechanisms related to the effect of HS on dairy cow milk production are still largely unknown. The present study employed an RNA-sequencing approach to explore the molecular mechanisms associated with a decline in milk production by the functional analysis of differentially expressed genes (DEGs) in mammary glands of cows exposed to HS and non-heat-stressed cows. The results of the current study reveal that HS increases the rectal temperature and respiratory rate. Cows under HS result in decreased bodyweight, dry matter intake (DMI), and milk yield. In the current study, a total of 213 genes in experimental cow mammary glands was identified as being differentially expressed by DEGs analysis. Among identified genes, 89 were upregulated, and 124 were downregulated. Gene Ontology functional analysis found that biological processes, such as immune response, chaperone-dependent refolding of protein, and heat shock protein binding activity, were notably affected by HS. The Kyoto Encyclopedia of Genes and Genomes enrichment analysis found that almost all of the top-affected pathways were related to immune response. Under HS, the expression of heat shock protein 90 kDa beta I (HSP90B1) and heat shock 70 kDa protein 1A was upregulated, while the expression of bovine lymphocyte antigen (BoLA) and histocompatibility complex, class II, DRB3 (BoLA-DRB3) was downregulated. We further explored the effects of HS on lactation-related genes and pathways and found that HS significantly downregulated the casein genes. Furthermore, HS increased the expression of phosphorylation of mammalian target of rapamycin, cytosolic arginine sensor for mTORC1 subunit 2 (CASTOR2), and cytosolic arginine sensor for mTORC1 subunit 1 (CASTOR1), but decreased the phosphorylation of Janus kinase-2, a signal transducer and activator of transcription factor-5. Based on the findings of DMI, milk yield, casein gene expression, and the genes and pathways identified by functional annotation analysis, it is concluded that HS adversely affects the immune function of dairy cows. These results will be beneficial to understand the underlying mechanism of reduced milk yield in HS cows.

Molecular characterization and expressional affirmation of the beta proteasome subunit cluster in rock bream immune defense

Immunoproteasomes are primarily induced upon infection and formed by replacing constitutive beta subunits with inducible beta subunits which possess specific cleavage properties that aid in the release of peptides necessary for MHC class I antigen presentation. In this study, we report the molecular characterization and expression analysis of the inducible immunosubunits PSMB8, PSMB9, PSMB9-L, and PSMB10 from rock bream, Oplegnathus fasciatus. The three subunits shared common active site residues and were placed in close proximity to fish homologues in the reconstructed phylogenetic tree, in which the mammalian homologues formed separate clades, indicating a common ancestral origin. The rock bream immunosubunits possessed higher identity and similarity with the fish homologues. RbPSMB8, RbPSMB9, RbPSMB9-L, and RbPSMB10 were multi-exonic genes with 6, 6, 7 and 8 exons, respectively. These four genes were constitutively expressed in all the examined tissues. Immunostimulants such as lipopolysaccharide and poly I:C induced RbPSMB8, RbPSMB9, RbPSMB9-L, and RbPSMB10 in liver and head kidney, suggesting their possible involvement in immune defense in rock bream.

CD8 knockout mice are protected from challenge by vaccination with WR201, a live attenuated mutant of Brucella melitensis

CD8+ T cells have been reported to play an important role in defense against B. abortus infection in mouse models. In the present report, we use CD8 knockout mice to further elucidate the role of these cells in protection from B. melitensis infection. Mice were immunized orally by administration of B. melitensis WR201, a purine auxotrophic attenuated vaccine strain, then challenged intranasally with B. melitensis 16M. In some experiments, persistence of WR201 in the spleens of CD8 knockout mice was slightly longer than that in the spleens of normal mice. However, development of anti-LPS serum antibody, antigen-induced production of γ-interferon (IFN-γ) by immune splenic lymphocytes, protection against intranasal challenge, and recovery of nonimmunized animals from intranasal challenge were similar between normal and knockout animals. Further, primary Brucella infection was not exacerbated in perforin knockout and Fas-deficient mice and these animals' anti-Brucella immune responses were indistinguishable from those of normal mice. These results indicate that CD8+ T cells do not play an essential role as either cytotoxic cells or IFN-γ producers, yet they do participate in a specific immune response to immunization and challenge in this murine model of B. melitensis infection.

The analysis of groEL gene in Salmonella enterica subspecies enterica serovar Typhimurium isolated from avians by PCR-Restriction Fragment Length Polymorphism method

Salmonella enterica subspecies enterica serovar Typhimurium causes food-borne outbreaks and systemic diseases in humans and animals. groEL gene (also known as mopA gene in S. Typhimurium), possessing conserved sequence, plays an important role in invasion of bacteria. The purpose of present study was to identify the polymorphism of groEL gene among different avians in different regions by PCR-RFLP method. Fifty two S. Typhimurium isolates (Broiler (n = 13), Layer (n = 12), Duck (n = 5), Goose (n = 5), Sparrow (n = 8), Canary (n = 3), Pigeon (n = 5) and Casco parrot (n = 1). were identified using serotyping as well as multiplex-PCR. Then, amplification of groEL gene performed and amplified products subjected to restriction digestion with BsuRI enzyme. Three RFLP profiles, A, B and C, generated DNA fragments between approximately 100-1,000 bp in size, were observed. The RFLP profile A was observed in 35 (67.3%), profile B in 14 (26.9%) and profile C in 3 (5.77%) of isolates. S. Typhimurium isolates recovered from 13 broilers (two of which profile A, 9 profile B and 2 profile C) and from 8 sparrows (two of which profile A, 5 profile B and 1 profile C) showed all three profiles, but 12 layers and other avians (including Canary (n = 3), Goose (n = 5), Duck (n = 5), Pigeon (n = 5) and Casco parrot (n = 1)) showed profile A. None of these profiles was allotted for a special region. The result of present study showed that S. Typhimurium undergoes genetic mutations in groEL gene under unpleasant milieu in different regions and in different avians. Thus, genetic diversity, despite conserved nature of groEL gene in S. Typhimurium, may exist but it depends on the condition where bacteria have settled. To our knowledge, three RFLP profiles of groEL gene generated by BsuRI restriction enzyme were not reported previously.

Non-classical MHC-E (Mamu-E) expression in the rhesus monkey placenta

The aim of this study was to characterize the expression of the rhesus HLA-E ortholog Mamu-E, particularly at the maternal-fetal interface. Mamu-E expression was confirmed by locus-specific RT-PCR in the placenta as well as in peripheral blood mononuclear cells (PBMC) and other organs. We evaluated the utility of antibodies recognizing HLA-E (MEM-E/06 against native HLA-E, MEM-E/02 against denatured HLA-E) to detect Mamu-E by flow cytometry/immunofluorescence, Western blot, and immunohistochemistry (IHC). Western blot analysis of cells and selected transfectants confirmed the recognition of Mamu-E but not Mamu-AG by antibodies MEM-E/06 and HC10 but not MEM-E/02. Immunohistochemical staining of frozen sections of rhesus placenta with the MEM-E/06 antibody demonstrated expression in most populations of rhesus monkey trophoblast cells, including villous cytotrophoblasts (strong positive staining), apical membrane of syncytiotrophoblasts (light to moderate staining) and extravillous cytotrophoblasts (moderate to strong staining, especially endovascular trophoblasts in early pregnancy). Expression was not trophoblast cell-specific, especially at term, when endothelial cells in both the chorionic plate and placental villi showed strong staining for Mamu-E. Staining of rhesus extravillous trophoblast cells suggested the co-expression of Mamu-E and Mamu-AG (the rhesus HLA-G homolog) on these cells. MEM-E/06 was shown also to react with differentiating rhesus placental syncytiotrophoblasts in primary culture, detecting intracellular and weak surface expression of Mamu-E. We conclude that the gestation-dependent co-expression of Mamu-E with Mamu-AG in villous and extravillous trophoblast cells suggests important and perhaps complementary but distinct roles of these two non-classical MHC class I loci in pregnancy at the maternal-fetal interface. In addition, the MEM-E/06 antibody will be useful for the detection of Mamu-E at the maternal-fetal interface in the rhesus monkey.

Effective control of chronic gamma-herpesvirus infection by unconventional MHC Class Ia-independent CD8 T cells

Control of virus infection is mediated in part by major histocompatibility complex (MHC) Class Ia presentation of viral peptides to conventional CD8 T cells. Although important, the absolute requirement for MHC Class Ia–dependent CD8 T cells for control of chronic virus infection has not been formally demonstrated. We show here that mice lacking MHC Class Ia molecules (K^b−/−xD^b−/− mice) effectively control chronic γ-herpesvirus 68 (γHV68) infection via a robust expansion of β₂-microglobulin (β₂-m)-dependent, but CD1d-independent, unconventional CD8 T cells. These unconventional CD8 T cells expressed: (1) CD8αβ and CD3, (2) cell surface molecules associated with conventional effector/memory CD8 T cells, (3) TCRαβ with a significant Vβ4, Vβ3, and Vβ10 bias, and (4) the key effector cytokine interferon-γ (IFNγ). Unconventional CD8 T cells utilized a diverse TCR repertoire, and CDR3 analysis suggests that some of that repertoire may be utilized even in the presence of conventional CD8 T cells. This is the first demonstration to our knowledge that β₂-m–dependent, but Class Ia–independent, unconventional CD8 T cells can efficiently control chronic virus infection, implicating a role for β₂-n–dependent non-classical MHC molecules in control of chronic viral infection. We speculate that similar unconventional CD8 T cells may be able to control of other chronic viral infections, especially when viruses evade immunity by inhibiting generation of Class Ia–restricted T cells.

In this paper the authors identify a β2-microglobulin–dependent but major histocompatibility complex (MHC) Class Ia– and CD1-independent class of CD8 T cells that effectively control chronic γ-herpesvirus infection in mice. The important point that should be of general interest to the readers of PLoS Pathogens is that an effective CD8 T cell response develops during chronic infection of mice lacking MHC Class Ia molecules. Enormous efforts have gone into characterizing the role of conventional CD8 T cells that recognize viral peptides together with MHC Class Ia molecules during chronic viral infection, and many vaccine approaches focus solely on this response. This paper shows that additional types of CD8 T cells can operate during chronic infection, and that indeed, conventional MHC Class Ia–restricted T cells may be dispensable for control of chronic herpesvirus infection. The authors believe this is a fundamentally important point because it raises the question of whether unconventional CD8 T cells are important for control of other chronic viral infections such as infection with HIV, Hepatitis C virus, Hepatitis B virus, or human herpesviruses.

H2-M3-restricted CD8+ T cells are not required for MHC class Ib-restricted immunity against Listeria monocytogenes

Studies using major histocompatibility complex (MHC)-Ia-deficient mice have shown that MHC-Ib-restricted CD8+ T cells can clear infections caused by intracellular pathogens such as Listeria monocytogenes. M3-restricted CD8+ T cells, which recognize short hydrophobic N-formylated peptides, appear to comprise a substantial portion of the MHC-Ib-restricted T cell response in the mouse model of L. monocytogenes infection. In this study, we isolated formyltransferase (fmt) mutant strains of L. monocytogenes that lacked the ability to add formyl groups to nascent polypeptides. These fmt mutant Listeria strains did not produce antigens that could be recognized by M3-restricted T cells. We showed that immunization of MHC-Ia-deficient mice with fmt mutant Listeria resulted in stimulation of a protective memory response that cleared subsequent challenge with wild-type L. monocytogenes, despite the fact that M3-restricted CD8+ T cells did not proliferate in these mice. These data suggest that M3-restricted T cells are not required for protection against L. monocytogenes and underscore the importance of searching for new antigen-presenting molecules among the large MHC-Ib family of proteins.

Genetic resistance to bovine tuberculosis in the Iberian wild boar

Bovine tuberculosis (bTB) is an important re-emerging zoonotic disease, causing major economic losses and constraining international trade of animals and their products. Despite eradication programmes, some countries continue to encounter outbreaks, mainly due to wildlife acting as primary hosts or reservoirs. While the genetic component of tuberculosis in humans and cattle is well documented, the role of genetic factors as modulators of bTB resistance remains unclear for natural populations. To address this issue, we investigated the relative contribution of host genetic variability to susceptibility to bTB infection and disease progression in wild boars from southern Spain. We found that genetic heterozygosity is an important predictor of bTB, not only modulating resistance to infection but also influencing containment of disease progression in infected individuals. Our results provide further evidence that host genetic variability plays a central role in natural populations. Testing each marker separately reveals evidence of both general and single-locus associative effects on bTB and several loci reveal high homology to regions of the genome with known immune function. Our results may prove to be crucial for understanding outbreaks of bTB in wildlife that could potentially affect domestic livestock and humans.

Ubiquitination of intracellular bacteria: a new bacteria-sensing system?

Ubiquitination is a protein modification generally used by cells to tag proteins that are destined for proteasomal degradation. In a recent article, Perrin et al. reported that the ubiquitination system has a role in the recognition of bacterial pathogens in the cytosol of mammalian cells. They showed that polyubiquitinated proteins accumulate on the surface of cytosolic Salmonella typhimurium. In macrophages, but not epithelial cells, proteasomes become associated with the surface of cytosolic bacteria. The authors proposed that the ubiquitin-proteasome machinery might be implicated indirectly in bacterial clearance.

Polymorphism and conservation of the genes encoding Qa1 molecules

To evaluate the polymorphism and conservation of the major histocompatibility complex class Ib molecule Qa1 in wild mouse populations, we determined the nucleotide sequence of exons 1-3 of Qa1 of eight mouse haplotypes derived from wild mice, including Mus musculus domesticus, M. m. castaneus, M. m. bactrianus, and M. spretus, as well as two t haplotypes. Our data identify eight new alleles of Qa1. Taken together with previously published data on Qa1 among the common laboratory inbred strains, and in agreement with cytotoxic T-lymphocyte, serological, and biochemical data, these results further confirm the existence of two families of Qa1 molecules, Qa1(a)-like and Qa1(b)-like, and illuminate the extreme conservation of the peptide-binding region of these molecules, even across species.

T cell immunity to brucellosis

Brucellosis is an ancient disease of animals and man that still threatens the health and prosperity of many, primarily in the third world, who depend on animal agriculture for their livelihood. Further, its pathogenicity and the facts that it is zoonotic is effectively eradicated from many Western nations make it a dangerous bioterrorism threat. Targeted human vaccination may reduce the various threats brucellosis poses. Significant effort has been expended toward this goal and many candidate vaccines exist. However, the ideal vaccine would be a subunit vaccine that specifically targets only the critical aspects of the immune response necessary to induce immunity. Much about the immune response, in particular the T cell response, remains to be discovered in order to accomplish that goal. In this review we focus on T cell responses to brucellosis with particular attention to the specific roles of T cell subtypes. We also point out areas of research on T cell responses that may allow exploitation of cutting edge vaccine technologies for the next generation vaccine for brucellosis.

Functional characterization of class Ia- and non-class Ia-restricted Chlamydia-reactive CD8+ T cell responses in humans

CD8(+) T cells are a key immune component for the eradication of many intracellular pathogens. This study aims to characterize the human CD8(+) T cell response to naturally processed chlamydial Ags in individuals exposed to the intracellular pathogen Chlamydia trachomatis. By using C. trachomatis-infected autologous dendritic cells (DCs) as stimulators, Chlamydia-reactive CD8(+) T cell responses were detected in all 10 individuals tested. The majority of the Chlamydia-reactive CD8(+) T cells were non-MHC class Ia restricted in all three of the individuals tested. From one donor, three non-class Ia-restricted and two class Ia-restricted Chlamydia-specific CD8(+) T cells were cloned and characterized further. All five T cell clones secreted IFN-gamma in response to autologous DCs infected with viable Chlamydia, but not with DCs pulsed with inactivated chlamydial elementary bodies. MHC class Ia-restricted and non-class Ia-restricted responses were inhibited by DC treatment with a proteasomal inhibitor and an endoplasmic reticulum-Golgi transport inhibitor, suggesting that these T cells recognize a peptide Ag translocated to the host cell cytosol during infection that is processed via the classical class Ia Ag-processing pathway. Even though both restricted and nonrestricted CD8(+) T cells produced IFN-gamma in response to Chlamydia-infected fibroblasts, only the non-class Ia-restricted cells were lytic for these targets. The class Ia-restricted CTLs, however, were capable of cytolysis as measured by redirected killing. Collectively, these data demonstrate that both class Ia-restricted and non-classically restricted CD8(+) T cells are elicited in C. trachomatis-exposed individuals. Their role in host immunity remains to be elucidated.

Listeria monocytogenes: clinical and experimental update

Listeria monocytogenes, a small gram-positive bacillus, causes sepsis and meningitis in immunocompromised patients and a devastating maternal/fetal infection in pregnant women. Recent outbreaks demonstrated that L. monocytogenes can cause gastroenteritis in otherwise healthy individuals and more severe invasive disease in immunocompromised patients. Centralized processing in the food industry may be the cause of these large-scale listeriosis outbreaks. The mouse model of listeriosis, which was developed in the 1960s, has been extraordinarily useful for studying T cell-mediated immunity. Contrary to the original concept that macrophages are the principal effector cells in listeriosis, we found that immigrating neutrophils play the predominant role in early liver defenses. At later time points, CD8(+) T cells lyse infected hepatocytes by both perforin- and Fas-L/Fas--dependent mechanisms. Of interest, nonclassical major histocompatibility complex (MHC) class Ib--restricted cytolytic activity is expressed early during primary infection, whereas MHC class Ia--restricted activity is predominant through late primary and secondary infections.

Contribution of MHC class I-dependent immune mechanisms induced by attenuated recombinant Salmonella typhimurium secreting superoxide dismutase to protection against murine listeriosis

A recombinant (r)Salmonella typhimurium aroA strain secreting the naturally non-secreted superoxide dismutase (SOD) of Listeria monocytogenes controls murine listeriosis dependent on 'transporter associated with antigen processing' (TAP)-mediated immune mechanisms. TAP1-deficient mice (devoid of most CD8 T cells) vaccinated with this rSalmonella SODs strain succumbed to lethal L. monocytogenes challenge, whereas C57BL/6 mice were protected by this vaccine. Moreover, vaccination of H-2I-Abeta-deficient mice (lacking major histocompatibility class (MHC) II molecules and thus devoid of mature CD4 TCR-alphabeta cells), of TAP1-deficient as well as of beta2microglobulin-deficient mice (devoid of conventional CD8 T cells) with a sublethal dose of L. monocytogenes and subsequent challenge with rSalmonella control or SODs strain revealed contribution of both MHC class I- and MHC class II-dependent immune mechanisms to the control of secondary Salmonella infection. Finally, the clearance of rSalmonella SODs bacteria was achieved in TAP1-deficient animals vaccinated with L. monocytogenes. Our data suggest a role of TAP-dependent mechanisms in priming of protective immunity by rSalmonella micro-organisms secreting SOD.