The reinfection threshold, revisited

One mode by which infection-derived immunity fails is when recovery leads to a reduced but nonzero risk of reinfection. This type of partial protection is called leaky immunity with the degree of leakiness quantified by the relative probability a previously infected individual will get infected upon exposure compared to a naively susceptible individual. Previous authors have defined the reinfection threshold, which occurs when the basic reproduction number equals the inverse of the leakiness, however, there has been some debate about whether or not this is a real threshold. Here we show how the reinfection threshold relates to two important occurrences: (1) the point at which the endemic equilibrium changes from being a stable spiral to a stable node, and (2) the point at which the rate of change of the prevalence increases the most relative to leakiness. When the recovery period is short relative to the average lifetime then both occurrences are close to the reinfection threshold. We show how these results are related to the reinfection threshold found in other models of imperfect immunity. To further demonstrate the significance of this threshold in modeling, we conducted a simulation study to evaluate some of the consequences the reinfection threshold might have in parameter estimation and modeling. Using specific parameter values chosen to reflect an acute infection, we found that the basic reproduction number values larger than that of the reinfection threshold value were less identifiable than those below the threshold.

Development and maintenance of a biospecimen repository for clinical samples derived from pulmonary patients

The Pulmonary Biospecimen Repository (PBR) at the University of Alabama at Birmingham (UAB) was launched in 2009. The purpose of the UAB PBR is to provide investigators within the pulmonary community at UAB and elsewhere with clinical samples derived from multiple lung diseases, including transplant recipients, idiopathic pulmonary fibrosis, chronic obstructive pulmonary disease, cystic fibrosis, and asthma. Cell and fluid samples isolated from bronchoalveolar lavage (BAL), plasma, and serum are collected and stored; samples are assessed routinely for viability. Each sample is linked directly with the respective patient information via the Pulmonary Translational Research and Clinical Database, a Health Insurance Portability and Accountability Act compliant database that includes detailed information allowing for the study of specific patient cohorts. To access samples, investigators must complete a request form, which is reviewed by the UAB PBR Steering Committee. To date, more than 800 patients have provided approximately 7,000 BAL, serum and plasma fluid, and cell samples. Over the past 4 years, nearly 800 of these samples have been distributed to investigators at UAB and elsewhere. Future plans for the UAB PBR include expanding sample collection to additional pulmonary diseases, such as mycobacterial infections, increasing the number of sample users and obtaining external funding to ensure its continued sustainability.

Tamanu (Calophyllum inophyllum) - the African, Asian, Polynesian and Pacific Panacea

Tamanu or Calophyllum inophyllum has been used traditionally as a local medicine for many different purposes. The oil has been proven to be vulnerary and cicatrising in its effects. The chemicals responsible for this action are calophyllolide and inophyllum in addition to other complex polyphenols.

Urinary protein profiles after burn injury

A study of the change of urinary protein excretion has been made in 26 patients followed from the time of admission to time of discharge from the Yorkshire Regional Burn Centre (7-200 days). Total protein, IgG and albumin (as indicators of glomerular function) and alpha 1-microglobulin, beta 2-microglobulin, retinol binding protein and N-acetyl-beta-D-glucosaminidase (as indicators of proximal tubular function) as well as the patterns on SDS polyacrylamide gel electrophoresis were examined. Patients were divided into three groups according to their urinary protein profiles. The first group was 3 patients who showed little or no evidence of proteinuria; the second group consisted of 7 patients who showed a mild and transient tubular proteinuria, all of whom recovered normal function within one week. The third group, 16 patients, developed moderate to severe proteinuria usually started as a mixed pattern of glomerular and tubular proteinuria, characterized by the excretion of a high level of total protein. After a few days, this pattern changed to a typical tubular proteinuria and the latter could last for as long as 200 days; in some of these patients a secondary increase of low molecular weight protein excretion occurred either due to a latent renal complication or induced by the administration of aminoglycosides. There is a close correlation between the intensity and patterns of the proteinuria and the severity and clinical progress of the burn.