Publications

Inactivation of β-lactams by the action of β-lactamase enzymes is the most common mode of resistance to these drugs among Gram-negative organisms. The genomes of some key clinical pathogens such as Enterobacter and Pseudomonas encode AmpC, an inducible chromosomal β-lactamase. The potent activity of AmpC against broad-spectrum β-lactams complicates treatment of organisms with this gene. Antibiotic exposure can select for mutants expressing high levels of this enzyme, leading to the emergence of resistant isolates and failure of therapy, even when the initial isolate is fully susceptible. The risk of selecting for resistant organisms varies according to the particular β-lactam used for treatment. This article reviews the microbiology of these enzymes, summarizes clinical data on the frequency emergence of resistance, and discusses considerations for antimicrobial treatment of these organisms.

PURPOSE OF REVIEW

To discuss recent advances in our understanding of the diverse roles of NF-κB/Rel family members in HIV-1 latency.

RECENT FINDINGS

Various NF-κB/Rel family members can reinforce maintenance of HIV-1 latency. For example, p50 recruits histone deacetylase 1 to the HIV-1 long terminal repeat promoting chromatin condensation and reduced RNA Pol II recruitment. Low-level NF-κB activation during homeostatic proliferation of memory CD4 T cells induced by IL-7 and TCR signaling or OX40 action promotes expression of antiapoptotic gene targets such as BCL2 and BCLXL. Additionally, the IκB kinase phosphorylates FOXO3a transcription factor, blocking its induction of proapoptotic genes. These combined effects promote memory CD4 T-cell survival, thus maintaining the latent reservoir. Conversely, when the nontumorigenic phorbol ester prostratin is combined with histone deacetylase inhibitors, potent synergistic activation of latent HIV-1 occurs involving nuclear expression of NF-κB.

SUMMARY

These recent findings highlight both the antagonistic and agonistic effects of the NF-κB signaling pathway on HIV-1 latency. Synergistic inducers might be useful for flushing of latent virus from reservoirs in infected patients. The ultimate, albeit lofty, goal is to achieve full viral eradication. However, a more reasonable goal might be a functional cure where patients experience a drug-free remission.

BACKGROUND

Without virologic testing, HIV-infected African children starting antiretroviral (ARV) therapy are at risk for undetected virologic failure and the development of ARV resistance. We sought to determine the prevalence of early virologic failure (EVF), to characterize the evolution of ARV-resistance mutations and to predict the impact on second-line therapy.

METHODS

The prevalence of EVF (HIV RNA >400 copies/mL on sequential visits after 6 months of therapy) was identified among 120 HIV-infected Ugandan children starting ARV therapy. ARV mutations were identified by population sequencing of HIV-1 pol in sequential archived specimens. Composite discrete genotypic susceptibility scores were determined for second-line ARV regimens.

RESULTS

EVF occurred in 16 children (13%) and persisted throughout a median (interquartile ratio) 938 (760-1066) days of follow-up. M184V and nonnucleoside reverse transcriptase inhibitor-associated mutations emerged within 6 months of EVF; thymidine-analog-mutations arose after 12 months. Worse discrete genotypic susceptibility scores correlated with increasing duration of failure (Spearman R = -0.47; P = 0.001). Only 1 child met World Health Organization CD4 criteria for ARV failure at the time of EVF or during the follow-up period.

CONCLUSIONS

A significant portion of HIV-infected African children experience EVF that would be undetected using CD4/clinical monitoring and resulted in the accumulation of ARV mutations that could compromise second-line therapy options.

Melanocortins (MSH's) are three structurally related peptides derived from proopiomelanocortin. They regulate several physiologic functions including energy metabolism, appetite, and inflammation. Recent work in rodents has also identified important effects of MSH's, particularly γ-MSH, on sodium metabolism and blood pressure regulation. Normal rats and mice respond to a high sodium diet with an increase in the plasma concentration of γ-MSH, and remain normotensive, while those with genetic or pharmacologic γ-MSH deficiency become hypertensive on a high sodium diet. This hypertension is corrected by exogenous administration of the peptide. Mice lacking the γ-MSH receptor (the melanocortin 3 receptor, Mc3r) also become hypertensive on a high sodium diet but remain so when administered γ-MSH, and infusions of physiologic levels of the peptide stimulate urinary sodium excretion in normal rats and mice, but not in mice with deletion of Mc3r. The salt-sensitive hypertension in rodents with impaired γ-MSH signaling appears due to stimulation of noradrenergic activity, since plasma noradrenaline is increased and the hypertension is rapidly corrected with infusion of the α-adrenoceptor antagonist phentolamine. In contrast to the antihypertensive property of physiologic levels of γ-MSH, intravenous or intracerebroventricular injections of high levels of the peptide raise blood pressure. This occurs in mice lacking Mc3r, indicating an interaction with some other central receptor. Finally, the salt-sensitive hypertension in rodents with disruption of γ-MSH signaling is accompanied by insulin resistance, an observation which offers a new window into the study of the association of salt-sensitive hypertension with insulin resistance and type II diabetes.

Proteases are the most abundant class of proteins produced by mast cells. Many of these are stored in membrane-enclosed intracellular granules until liberated by degranulating stimuli, which include cross-linking of high affinity IgE receptor F(c)εRI by IgE bound to multivalent allergen. Understanding and separating the functions of the proteases is important because expression differs among mast cells in different tissue locations. Differences between laboratory animals and humans in protease expression also influence the degree of confidence with which results obtained in animal models of mast cell function can be extrapolated to humans. The inflammatory potential of mast cell proteases was the first aspect of their biology to be explored and has received the most attention, in part because some of them, notably tryptases and chymases, are biomarkers of local and systemic mast cell degranulation and anaphylaxis. Although some of the proteases indeed augment allergic inflammation and are potential targets for inhibition to treat asthma and related allergic disorders, they are protective and even anti-inflammatory in some settings. For example, mast cell tryptases may protect from serious bacterial lung infections and may limit the "rubor" component of inflammation caused by vasodilating neuropeptides in the skin. Chymases help to maintain intestinal barrier function and to expel parasitic worms and may support blood pressure during anaphylaxis by generating angiotensin II. In other life-or-death examples, carboxypeptidase A3 and other mast cell peptidases limit systemic toxicity of endogenous peptideslike endothelin and neurotensin during septic peritonitis and inactivate venom-associated peptides. On the other hand, mast cell peptidase-mediated destruction of protective cytokines, like IL-6, can enhance mortality from sepsis. Peptidases released from mast cells also influence nonmast cell proteases, such as by activating matrix metalloproteinase cascades, which are important in responses to infection and resolution of tissue injury. Overall, mast cell proteases have a variety of roles, inflammatory and anti-inflammatory, protective and deleterious, in keeping with the increasingly well-appreciated contributions of mast cells in allergy, tissue homeostasis and innate immunity.

OBJECTIVE

Systemic lupus erythematosus (SLE) primarily affects women of reproductive age. Here we summarize the scientific evidence supporting recently developed quality indicators (QIs) pertaining to reproductive health.

METHODS

We used a modification of the RAND/UCLA Appropriateness Method to develop QIs for SLE. We performed systematic reviews of the literature pertaining to each proposed indicator. Three indicators focusing on reproductive health were included in the final set. Relevant literature was presented to an expert panel, who rated the validity and feasibility of the indicators.

RESULTS

Three QIs were rated as valid and feasible. These indicators specifically address laboratory testing during pregnancy in SLE, the treatment of antiphospholipid antibody syndrome, and counseling for drugs with teratogenic potential.

CONCLUSION

We used a rigorous method to develop reproductive health QIs for SLE. In the future, these indicators can be used in the assessment and delivery of care to patients with SLE.