Philana g Lin

Tumor Necrosis Factor and Chemokine Interactions in the Formation and Maintenance of Granulomas in Tuberculosis

Inflammatory cells migrate to the lungs in response to Mycobacterium tuberculosis infection. These infiltrating cells organize into a structure called a granuloma, which controls and contains infection. The signals that influence the formation of granulomas are largely unknown. Tumor necrosis factor (TNF) has been demonstrated to be required for formation of granulomas, in mouse models of tuberculosis, and for control of latent tuberculosis, in humans. We investigated the mechanisms by which TNF controls cell migration in response to M. tuberculosis infection, focusing on the effects of this cytokine on chemokine expression. Chemokines are small molecules that direct the migration of cells within the body. Our data support the notion that TNF is required for appropriate chemokine expression by M. tuberculosis-infected macrophages, both in vitro and in vivo.

Early Trends for Invasive Pneumococcal Infections in Children After the Introduction of the 13-valent Pneumococcal Conjugate Vaccine

Background: The 13-valent pneumococcal conjugate vaccine (PCV13) was introduced for routine administration to infants and children in 2010 in the United States. We have monitored clinical and microbiologic features of invasive pneumococcal infections among children before and after PCV13 use. Methods: Infants and children cared for at 8 children hospitals in the United States with culture-proven invasive infections caused by S. pneumoniae were identified in an ongoing prospective surveillance study. Demographic and clinical data were recorded on a standard case report form. Serotype and antimicrobial susceptibilities of isolates were determined. Results: Since routine PCV13 immunization in 2010, invasive pneumococcal infections decreased 42% overall and 53% for children <24 months of age in 2011 compared with the average number of cases for 2007 to 2009. PCV13 serotype isolates decreased 57% during these same time periods; 19A, 7F and 3 decreased by 58%, 54% and 68%, respectively. The number of infections caused by serotypes 1 and 6C also decreased in 2011. The most common non-PCV13 serotypes encountered in 2010 and 2011 combined were 33F, 22F, 12, 15B, 15C, 23A and 11. Bacteremia, pneumonia and mastoiditis cases decreased more than meningitis cases. Conclusions: After the introduction of PCV13, invasive pneumococcal infections decreased among 8 children hospitals compared with the 3 years before PCV13 use. Slight increases in some non-PCV13 serotype isolates were noted in 2011. Continued surveillance is necessary to determine the effectiveness of PCV13 including herd protection as well as any emerging invasive serotypes.

Increase in Prevalence of Streptococcus pneumoniae Serotype 6C at Eight Children's Hospitals in the United States from 1993 to 2009

ABSTRACT Streptococcus pneumoniae serotype 6C, which was described in 2007, causes invasive disease in adults and children. We investigated the prevalence of 6C among pediatric isolates obtained from eight childrens hospitals in the United States. S. pneumoniae isolates were identified from a prospective multicenter study (1993 to 2009). Fifty-seven serotype 6C isolates were identified by multiplex PCR and/or Quellung reaction. Five were isolated before 2000, and the prevalence increased over time (P < 0.000001). The median patient age was 2.1 years (range, 0.2 to 22.5 years). Clinical presentations included bacteremia (n = 24), meningitis (n = 7), pneumonia (n = 4), abscess/wound (n = 3), mastoiditis (n = 2), cellulitis (n = 2), peritonitis (n = 1), septic arthritis (n = 1), otitis media (n = 10), and sinusitis (n = 3). By broth microdilution, 43/44 invasive serotype 6C isolates were susceptible to penicillin (median MIC, 0.015 μg/ml; range, 0.008 to 2 μg/ml); all were susceptible to ceftriaxone (median MIC, 0.015 μg/ml; range, 0.008 to 1 μg/ml). By disk diffusion, 16/44 invasive isolates (36%) were nonsusceptible to erythromycin, 19 isolates (43%) were nonsusceptible to trimethoprim-sulfamethoxazole (TMP-SMX), and all isolates were clindamycin susceptible. Multilocus sequence typing (MLST) revealed 24 sequence types (STs); 9 were new to the MLST database. The two main clonal clusters (CCs) were ST473 and single-locus variants (SLVs) (n = 13) and ST1292 and SLVs (n = 23). ST1292 and SLVs had decreased antibiotic susceptibility. Serotype 6C causes disease in children in the United States. Emerging CC1292 expressed TMP-SMX resistance and decreased susceptibility to penicillin and ceftriaxone. Continued surveillance is needed to monitor changes in serotype prevalence and possible emergence of antibiotic resistance in pediatric pneumococcal disease.

Immunological concepts in tuberculosis diagnostics for non-human primates: a review.

Accurate diagnosis of tuberculosis in non‐human primates is of critical importance. As with natural human infection with Mycobacterium tuberculosis, infected primates develop a broad spectrum of disease, including subclinical (latent) infection, chronic primary tuberculosis, rapidly progressing fulminant disease, and reactivation tuberculosis. In a primate colony, clinical suspicion is the key to diagnosis. The course of action should be based on careful and thorough clinical assessments in conjunction with screening and microbiologic methods. Diagnostic modalities can be categorized into pathogen identification and immunologic host response techniques. While the classic tuberculin skin test is the standard screening tool, it has limited sensitivity and specificity. Other tools such as interferon gamma releasing assays have similar accuracy results but use different immunologic mechanisms and may be helpful as an additional screening tool. Advantages and disadvantages to these and other assays (e.g., lymphocyte proliferation assay, antibody detection) are also discussed. Surrogates to sputum sample (e.g., gastric aspirate, stool samples, respiratory sample via bronchoscopy) should be obtained for microbiologic identification, as acid‐fast smear and culture are critical to pathogen identification for optimal sensitivity and specificity. Interpretation of these immunologic screening tools should be performed cautiously and must be correlated with level of suspicion. While the identification of M. tuberculosis or M. bovis confirms the diagnosis of tuberculosis, negative results do not exclude the diagnosis. Without pathogen detection to confirm diagnosis, thorough gross and microscopic pathological review at necropsy may be required to make a definitive diagnosis. Lastly, the risk and benefits to the primate colony, staff and resources must be carefully weighed when deciding to euthanize monkeys to make the diagnosis of tuberculosis.

Rhesus Macaques Are More Susceptible to Progressive Tuberculosis than Cynomolgus Macaques: a Quantitative Comparison

ABSTRACT In the past 2 decades, it has become increasingly clear that nonhuman primates, specifically macaques, are useful models for human tuberculosis (TB). Several macaque species have been used for TB studies, and questions remain about the similarities and differences in TB pathogenesis among macaque species, which can complicate decisions about the best species for a specific experiment. Here we provide a quantitative assessment, using serial positron emission tomography and computed tomography (PET-CT) imaging and precise quantitative determination of bacterial burdens of low-dose Mycobacterium tuberculosis infection in cynomolgus macaques of Chinese origin, rhesus macaques of Chinese origin, and Mauritian cynomolgus macaques. This comprehensive study demonstrates that there is substantial variability in the outcome of infection within and among species. Overall, rhesus macaques have higher rates of disease progression, more lung, lymph node, and extrapulmonary involvement, and higher bacterial burdens than Chinese cynomolgus macaques. The small cohort of Mauritian cynomolgus macaques assessed here indicates that this species is more similar to rhesus macaques than to Chinese cynomolgus macaques in terms of M. tuberculosis infection outcome. These data provide insights into the differences among species, providing valuable data to the field for assessing macaque studies of TB.

A new method to evaluate macaque health using exhaled breath: A case study of M. tuberculosis in a BSL-3 setting

Breath is hypothesized to contain clinically relevant information, useful for the diagnosis and monitoring of disease, as well as understanding underlying pathogenesis. Nonhuman primates, such as the cynomolgus macaque, serve as an important model for the study of human disease, including over 70 different human infections. In this feasibility study, exhaled breath was successfully collected in less than 5 min under Biosafety Level 3 conditions from five anesthetized, intubated cynomolgus and rhesus macaques, before and after lung infection with M. tuberculosis The breath was subsequently analyzed using comprehensive two-dimensional gas chromatography coupled to time-of-flight mass spectrometry. A total of 384 macaque breath features were detected, with hydrocarbons being the most abundant. We provide putative identification for 19 breath molecules and report on overlap between the identified macaque breath compounds and those identified in previous human studies.NEW & NOTEWORTHY To the best of our knowledge, this is the first time the volatile molecule content of macaque breath has been comprehensively sampled and analyzed. We do so here in a Biosafety Level 3 setting in the context of M. tuberculosis lung infection. The breath of nonhuman primates represents a novel fluid that could provide insight into disease pathogenesis.

New kids on the block: an old problem for a growing pediatric population.

SOT in children has come a long way since our first experiences with these procedures in the 1950s (1). This remarkable success story and the long-term survival that pediatric SOT recipients now experience has pediatricians facing a new set of unanswered questions. While the use of immunosuppressive medications has clearly shown a benefit in preventing graft rejection, the use of these agents also has a major impact on the transplant recipient’s host defenses against infection. Beyond the immediate impact of the net amount of immune suppression present at any given time, an additional potential consequence of exposure to these medications is the interruption of the natural immune maturation process particularly when exposure occurs early in life. In the face of these questions, we are left to wonder just how do common pediatric infections impact on an uncommon but growing population of children who have undergone solid organ transplantation? In this edition of Pediatric Transplantation, Tran et al. (2) conducted a retrospective chart review to evaluate the rate of invasive pneumococcal disease among pediatric SOT recipients. Consistent with previous reports (3–5), the authors demonstrate that pediatric SOT recipients are at increased risk of invasive pneumococcal disease compared with their healthy counterparts and that the overwhelming majority of children with invasive disease underwent transplantation before the age of 2 yr. In contrast to the previous reports, the relatively large number of pediatric SOT recipients evaluated in this study has allowed the authors to compare the risk of invasive pneumococcal disease by organ transplant type. Tran et al. (2) found that heart transplant recipients were at a greater risk than recipients of other solid organ transplants. A significant observation of this study was that there was an average of 20 months between the transplantation and the occurrence of invasive disease, allowing a window of opportunity for vaccination among this high-risk group. Beyond these important observations, a number of question are raised by the authors that merit further discussion and study in the area of transplant immunology, particularly as it relates to the pediatric population. These authors and others (4) have identified the receipt of a heart transplant before the age of 2 yr to be a specific risk factor for invasive pneumococcal disease. In the study by Stoval et al. (4), the incidence of graft rejection, a marker of a requirement for more intense immune suppression, did not appear to be greater in the infected group. This suggests that the overall impact of immunosuppression for transplantation (i.e. therapeutic induction and maintenance immune suppression) during a critical time period of immune maturation may have a greater impact than the net intensity of immune suppression alone. In general, heart transplant recipients constitute a significant proportion of the very young pediatric SOT recipients but other factors beyond age at transplant may play a role. Recipient thymectomy at the time of transplantation has been performed as part of the cardiac transplant procedure and may be another factor that could impact on immune maturation. As this procedure is not mentioned in either report, we cannot know if it might be an explanation for the excessive risk that was identified in the pediatric heart recipients. Further studies are needed to look at the potential impact of transplantation during immune maturation. The documentation of an increased risk of developing invasive pneumococcal infections raises the question of the potential benefit of prophylactic strategies to prevent these complications. Tran et al. and others (2–4) suggest that there may be a window of opportunity after transplant and before the onset of invasive pneumococcal disease in which immunization could be performed. While most pediatric experts Pediatr Transplantation 2005: 9: 138–140. DOI: 10.1111/j.1399-3046.2005.00310.x