Rhodococcus equi Infection in HIV-positive Subjects: A Retrospective Analysis of 24 Cases

Arlotti, Massimo; Zoboli, G.; Moscatelli, Gianluigi; Magnani, Giacomo; Maserati, Renato; Borghi, Vanni; Andreoni, Massimo; Libanore, Marco; Bonazzi, L; Piscina, A.; Ciammarughi, R.

doi:10.3109/00365549609037941

Cited by 73 publications

(63 citation statements)

References 24 publications

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“…R. equi has also emerged as a common opportunistic pathogen in immunosuppressed people, especially those infected with the human immunodeficiency virus (1)(2)(3). Infection in either species is most commonly characterized by life-threatening pyogranulomatous pneumonia (3,4).…”

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confidence: 99%

Comparison of Etest, Disk Diffusion, and Broth Macrodilution for In Vitro Susceptibility Testing of Rhodococcus equi

et al. 2015

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confidence: 99%

Comparison of Etest, Disk Diffusion, and Broth Macrodilution for In Vitro Susceptibility Testing of Rhodococcus equi

et al. 2015

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“…R. equi has also emerged as a significant opportunistic pathogen in immunosuppressed people, especially those infected with the human immunodeficiency virus (3,9,14). In foals, the course of the disease is insidious and pathology is often extensive by the time the disease is diagnosed.…”

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confidence: 99%

In Vivo Expression of and Cell-Mediated Immune Responses to the Plasmid-Encoded Virulence-Associated Proteins ofRhodococcus equiin Foals

Jacks

Giguère

Prescott

2007

Clin Vaccine Immunol

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Rhodococcus equi is a facultative intracellular pathogen that causes pneumonia in foals but does not induce disease in adult horses. Virulence of R. equi depends on the presence of a large plasmid, which encodes a family of seven virulence-associated proteins (VapA and VapC to VapH). Eradication of R. equi from the lungs depends on gamma interferon (IFN-␥) production by T lymphocytes. The objectives of the present study were to determine the relative in vivo expression of the vap genes of R. equi in the lungs of infected foals, to determine the recall response of bronchial lymph node (BLN) lymphocytes from foals and adult horses to each of the Vap proteins, and to compare the cytokine profiles of proliferating lymphocytes between foals and adult horses. vapA, vapD, and vapG were preferentially expressed in the lungs of infected foals, and expression of these genes in the lungs was significantly (P < 0.05) higher than that achieved during in vitro growth. VapA and VapC induced the strongest lymphoproliferative responses for foals and adult horses. There was no significant difference in recall lymphoproliferative responses or IFN-␥ mRNA expression by bronchial lymph node lymphocytes between foals and adults. In contrast, interleukin 4 (IL-4) expression was significantly higher for adults than for foals for each of the Vap proteins. The ratio of IFN-␥ to IL-4 was significantly higher for foals than for adult horses for most Vap proteins. Therefore, foals are immunocompetent and are capable of mounting lymphoproliferative responses of the same magnitude and cytokine phenotype as those of adult horses.Rhodococcus equi, a gram-positive facultative intracellular pathogen, is one of the most important causes of pneumonia in foals between ages 3 weeks and 5 months. R. equi has also emerged as a significant opportunistic pathogen in immunosuppressed people, especially those infected with the human immunodeficiency virus (3,9,14). In foals, the course of the disease is insidious and pathology is often extensive by the time the disease is diagnosed. Unlike environmental R. equi, isolates from pneumonic foals typically contain an 80-to 90-kb plasmid. Plasmid-cured derivatives of virulent R. equi strains lose their ability to replicate and survive in macrophages (12). Plasmid-cured derivatives also fail to induce pneumonia and are completely cleared from the lungs of foals, confirming the absolute necessity of the large plasmid for the virulence of R. equi (12, 37).A 27.5-kb region of the virulence plasmid bears the hallmark of a pathogenicity island and contains the genes for a family of seven closely related virulence-associated (Vap) proteins, designated VapA and VapC to VapH (35). Although a recent study has proposed the designation vapI for another gene of the pathogenicity island, vapI is not functional (31). In a recent study, an R. equi mutant lacking a 7.9-kb DNA region spanning five vap genes (vapA, -C, -D, -E, and -F) was attenuated for virulence in mice and failed to replicate in macrophages (20). Only complementa...

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“…This gram-positive, facultatively intracellular bacterium is an opportunistic pathogen in immunocompromised humans, such as those infected with human immunodeficiency virus (2,9,13). Foal-virulent R. equi strains possess an 81-kb plasmid and express VapA, a plasmid-encoded, surface-expressed lipoprotein (38,(40)(41)(42).…”

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confidence: 99%

Immunoglobulin G Subisotype Responses of Pneumonic and Healthy, Exposed Foals and Adult Horses toRhodococcus equiVirulence-Associated Proteins

Hooper-McGrevy

Wilkie

Prescott

2003

Clin Vaccine Immunol

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Rhodococcus equi causes severe pyogranulomatous pneumonia in foals and in immunocompromised humans. Replication of virulent isolates within macrophages correlates with the presence of a large plasmid which encodes a family of seven virulence-associated proteins (VapA and VapC to VapH), whose functions are unknown. Although cell-mediated immunity is thought to be crucial in eliminating R. equi infection, antibody partially protects foals. The antibody response to both VapA and VapC was similar in six adult horses and six naturally exposed but healthy foals, as well as in eight foals with R. equi pneumonia. The immunoglobulin G (IgG) subisotype response of pneumonic foals to Vap proteins was significantly IgGb biased and also had a trend toward higher IgGT association compared to the isotype association of antibody in adult horses and healthy exposed foals. This suggests that in horses, IgGb and IgGT are Th2 isotypes and IgGa is a Th1 isotype. Furthermore, it suggests that foals which develop R. equi pneumonia have a Th2-biased, ineffective immune response whereas foals which become immune develop a Th1-biased immune response. Pneumonic foals had significantly more antibody to VapD and VapE than did healthy exposed foals. This may indicate a difference in the expression of these two Vap proteins during persistent infection. Alternatively, in pneumonic foals the deviation of the immune response toward VapD and VapE may reflect a bias unfavorable to R. equi resistance. These data indicate possible age-related differences in the equine immune response affecting Th1-Th2 bias as well as antibody specificity bias, which together favor the susceptibility of foals to R. equi pneumonia.

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Rhodococcus equi Infection in HIV-positive Subjects: A Retrospective Analysis of 24 Cases

Cited by 73 publications

References 24 publications

Comparison of Etest, Disk Diffusion, and Broth Macrodilution for In Vitro Susceptibility Testing of Rhodococcus equi

Comparison of Etest, Disk Diffusion, and Broth Macrodilution for In Vitro Susceptibility Testing of Rhodococcus equi

In Vivo Expression of and Cell-Mediated Immune Responses to the Plasmid-Encoded Virulence-Associated Proteins ofRhodococcus equiin Foals

Immunoglobulin G Subisotype Responses of Pneumonic and Healthy, Exposed Foals and Adult Horses toRhodococcus equiVirulence-Associated Proteins

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