Faculty Bibliography

OBJECTIVE: Humoral and cell-mediated immune responses to monovalent 2009 pandemic influenza A (H1N1/2009) and seasonal trivalent influenza (TIV) vaccines were evaluated in healthy children and children with asthma, sickle cell disease (SCD), systemic lupus erythematosus (SLE), and solid organ transplantation (SOT). STUDY DESIGN: Blood was collected from 112 subjects at the time of H1N1/2009 vaccination and 46 +/- 15 days later for hemagglutination inhibition titers and gamma-interferon ELISPOT responses to H1N1/2009 vaccine and TIV; unvaccinated children also received TIV at enrollment. RESULTS: A significant increase in the percentage of subjects with seroprotective hemagglutination inhibition titers to both vaccines was observed in all high-risk groups. Children with asthma and SCD were most likely to achieve seroprotective titers to H1N1/2009, whereas <50% of subjects with SOT and SLE had a seroprotective response. Subjects with SOT and SLE also had lower rates of seroprotection after TIV, and subjects with SLE had the lowest ELISPOT responses to both vaccines. Overall, 73% of healthy children exhibited protective responses to TIV; only 35% achieved seroprotection for H1N1/2009. CONCLUSIONS: This evaluation of immune responses to H1N1/2009 in high-risk children suggests suboptimal responses for SOT and SLE subjects, but not for subjects with SCD or asthma. Higher antigen dose, additional dose regimens, or both for immunocompromised children warrant further investigation.

BACKGROUND: Female genital tract secretions are bactericidal for Escherichia (E.) coli ex vivo. However, the intersubject variability and molecules that contribute to this activity have not been defined. METHODS: The bactericidal activity and concentration of immune mediators in cervicovaginal lavage (CVL) collected from 99 healthy women were determined. RESULTS: CVL reduced the number of E. coli colonies by 68% [-26, 100] (median [range]). CVL were active against laboratory and clinical isolates of E. coli, but were inactive against Lactobacillus species. Bactericidal activity correlated with the concentration of protein recovered (p<0.001), but not with cytokines, chemokines or antimicrobial peptides. Four CVL with>90% inhibitory activity (active) and two with<30% activity were subjected to MS/MS proteomic analysis. 215 proteins were identified and six were found exclusively in active samples. Four of these corresponded to Lactobacillus crispatus or jensenii proteins. Moreover, culture supernatants from Lactobacillus jensenii were bactericidal for E. coli. CONCLUSION: Both host and commensal microbiota proteins contribute to mucosal defense. Identification of these proteins will facilitate the development of strategies to maintain a healthy vaginal microbiome and prevent colonization with pathogenic bacteria such as E. coli that increase the risk for urinary tract infections, preterm labor and perinatal infection.

BACKGROUND: Genital secretions collected from adult women exhibit in vitro activity against herpes simplex virus (HSV) and Escherichia coli (E. coli), but prior studies have not investigated this endogenous antimicrobial activity or its mediators in adolescent females. METHODOLOGY/PRINCIPAL FINDINGS: Anti-HSV and anti-E.coli activity were quantified from cervicovaginal lavage (CVL) specimens collected from 20 sexually active adolescent females (15-18 years). Soluble immune mediators that may influence this activity were measured in CVL, and concentrations of Lactobacillus jensenii and crispatus were quantified by PCR from vaginal swabs. Results for adolescents were compared to those obtained from 54 healthy, premenopausal adult women. Relative to specimens collected from adults, CVL collected from adolescent subjects had significantly reduced activity against E. coli and diminished concentrations of protein, IgG, and IgA but significantly increased anti-HSV activity and concentrations of interleukin (IL)-1alpha, IL-6 and IL-1 receptor antagonist. Vaginal swabs collected from adolescent subjects had comparable concentrations of L. crispatus but significantly reduced concentrations of L. jensenii, relative to adult swabs. CONCLUSIONS/SIGNIFICANCE: Biomarkers of genital mucosal innate immunity may differ substantially between sexually active adolescents and adult women. These findings warrant further study and may have significant implications for prevention of sexually transmitted infections in adolescent females.

Pharmacologic strategies for the prevention of HIV include vaccines, post-exposure prophylaxis with antiretroviral therapy, and topical microbicides. Vaginal microbicides have the potential to augment innate defenses in the genital tract but may also disrupt endogenous protection and increase HIV acquisition risk, as observed in clinical trials of nonoxynol-9. The initially disappointing results of microbicide clinical trials stimulated the development of more sensitive and comprehensive pre-clinical safety studies, which include dual-chamber culture systems to model the epithelial barrier and post-coital studies to evaluate the effects of semen and sexual intercourse on microbicide efficacy. This review discusses the key factors that contribute to a healthy female genital tract environment, the impact of semen on mucosal defense, and how our understanding of these mediators informs the development of effective vaginal microbicides.

BACKGROUND: Preclinical and early phase clinical microbicide studies have not consistently predicted the outcome of efficacy trials. To address this gap, candidate biomarkers of microbicide pharmacodynamics and safety were evaluated in a double-blind, placebo-controlled trial of tenofovir gel, the first microbicide to demonstrate significant protection against HIV acquisition. METHODS: 30 women were randomized to apply a single daily dose of tenofovir or placebo gel for 14 consecutive days. Anti-HIV activity was measured in cervicovaginal lavage (CVL) on Days 0, 3, 7, 14 and 21 by luciferase assay as a surrogate marker of pharmacodynamics. Endogenous activity against E. coli and HSV-2 and concentrations of immune mediators were quantified in CVL as candidate biomarkers of safety. Tenofovir levels were measured in CVL and blood. RESULTS: A significant increase in anti-HIV activity was detected in CVL from women who applied tenofovir gel compared to their endogenous anti-HIV activity in genital tract secretions on Day 0 and compared to activity in CVL from women in the placebo group. The activity correlated significantly with CVL concentration of tenofovir (r = 0.6, p<0.001) and fit a sigmoid E(max) pharmacodynamic model. Anti-HIV activity in CVL from women who applied tenofovir persisted when virus was introduced in semen, whereas endogenous anti-HIV activity decreased. Tenofovir did not trigger an inflammatory response or induce sustained loss in endogenous antimicrobial activity or immune mediators. CONCLUSIONS: Tenofovir gel had no deleterious impact on soluble mucosal immunity. The increased anti-HIV activity in CVL, which persisted in the presence of semen and correlated with tenofovir concentration, is consistent with the efficacy observed in a recent clinical trial. These results promote quantified CVL anti-HIV activity as a surrogate of tissue pharmacodynamics and as a potential biomarker of adherence to product. This simple, feasible and inexpensive bioassay may promote the development of models more predictive of microbicide efficacy. TRIAL REGISTRATION: ClinicalTrials.gov NCT00594373.

We describe a case of transfusion-associated babesiosis following bidirectional Glenn procedure. This unique case highlights the importance of including babesiosis and other typically vector-borne infections in the differential diagnosis for patients with recent blood transfusions and fever without obvious source.

Pediatric PTLD is often associated with primary EBV infection and immunosuppression. The aim was to retrospectively review the spectrum of histologically documented PTLD for two time intervals differentiated by changes in use of molecular EBV monitoring. Eleven of 146 patients (7.5%) in 2001-2005 (Era A) and 10 of 92 (10.9%) in 1993-1997 (Era B) were diagnosed with PTLD. The median age at liver transplantation (0.8 and 0.9 yr, respectively) and the median duration between liver transplant and diagnosis of PTLD (0.6 and 0.7 yr, respectively) were similar in both eras. However, patients in Era A presented with significantly less advanced histological disease compared to patients in Era B (p=0.03). Specifically, nine patients (82%) in Era A had Pl hyperplasia/polymorphic PTLD, whereas in Era B, six had advanced histological disease (five monomorphic and one unclassified). Three transplant recipients in Era B died secondary to PTLD, whereas there were no PTLD-related deaths in Era A (p=0.03). Heightened awareness of risk for PTLD, alterations in baseline immunosuppression regimens, implementation of molecular EBV monitoring, pre-emptive reduction in immunosuppression and improved therapeutic options may have all contributed to a milder PTLD phenotype and improved clinical outcomes

PURPOSE OF REVIEW: The review highlights advances in the diagnosis and treatment of viral infections in organ transplant recipients, with emphasis on the most significant pathogens for liver transplant recipients. RECENT FINDINGS: The development of molecular diagnostics has markedly improved the ability to rapidly identify infections in transplantation patients and has improved clinical care. Multiplex polymerase chain reaction (PCR) has enhanced the ability to identify respiratory viruses, permitting earlier treatment. Monitoring for cytomegalovirus and Epstein-Barr virus by PCR offers the opportunity for preemptive interventions. However, imperfect negative predictive values may result in failure to treat early disease, and poor positive predictive values may lead to increased risk of rejection in patients in whom immunosuppression is prematurely reduced and/or unnecessary administration of antiviral therapy. For several viral pathogens, there is an absence of specific and well tolerated therapies, and several treatment modalities have not been rigorously evaluated in controlled clinical trials. SUMMARY: Viral infections remain a leading cause of morbidity and mortality in the solid organ transplantation population, particularly in pediatric patients. Whereas diagnostic testing has greatly improved, there is an urgent need for the development of novel therapies, including adoptive immunotherapy, to provide well tolerated and effective therapy.

The history of antibiotic resistance in Staphylococcus aureus spans more than half a century. Methicillin-resistant S. aureus (MRSA) has emerged as an almost ubiquitous pathogen in both the community and hospital settings. The predominant clone responsible for community-associated MRSA, USA300, is a highly successful pathogen, as demonstrated by its rapid global spread and associated morbidity and mortality. The management of MRSA infections in pediatric patients is complicated by the limited number of effective antibiotics that have been well-studied in children. The gold standard antimicrobial, vancomycin, has several shortcomings that have prompted the development of newer agents for the treatment of MRSA disease. Moreover, the emergence of vancomycin-intermediate or -resistant S. aureus, while uncommon, portends a potential new era of resistance that will require research and development of the next generation of antibiotics that act by novel mechanisms.