ARCHIVED - Infectious Diseases News Brief - January 27, 2012

Entry Point for Hepatitis C Infection Identified

A molecule embedded in the membrane of human liver cells that aids in cholesterol absorption also allows the entry of hepatitis C virus, the first step in hepatitis C infection, according to research at the University of Illinois at Chicago College of Medicine. The cholesterol receptor offers a promising new target for anti-viral therapy, for which an approved drug may already exist, say the researchers, whose findings were reported online in advance of publication in Nature Medicine. An estimated 4.1 million Americans are infected with hepatitis C virus, or HCV, which attacks the liver and leads to inflammation, according to the National Institutes of Health. Most people have no symptoms initially and may not know they have the infection until liver damage shows up decades later during routine medical tests. Previous studies showed that cholesterol was somehow involved in HCV infection. The researchers suspected that a receptor called NPC1L1, known to help maintain cholesterol balance might also be transporting the virus into the cell. The receptor is common in the gut of many species -- but is found on liver cells only in humans and chimpanzees, says Susan Uprichard, assistant professor in medicine and microbiology and immunology and principal investigator in the study.

Source: Science Daily January 24, 2012

The Number Needed to Vaccinate to Prevent Infant Pertussis Hospitalization and Death Through Parent Cocoon Immunization

Background. Parental immunization has been recommended as a “cocoon” strategy to prevent serious pertussis outcomes in early infancy. The researchers illustrate the high number needed to vaccinate (NNV) for this program based on recent epidemiologic data from the provinces of Québec and British Columbia (BC), Canada.

Methods. Surveillance trends were summarized for the period 1990–2010. Hospitalization, intensive care unit (ICU) admission, and mortality data were compiled from 2000 to 2009. The proportion of infant pertussis attributed to a parent was estimated at 35%, explored up to 55%. Adult vaccine efficacy (VE) was estimated at 85%. The NNV was calculated as [2 parents/(parent-attributable infant risk × parent VE)]. To capture at least 1 recent cyclical peak, NNV was derived for the period 2005–2009 and explored for peak/trough years.

Results. Substantial decline has occurred in pertussis incidence across all age groups including infants, reaching a 20-year nadir in 2010 in both provinces. For the period 2005–2009, the risk of infant hospitalization and ICU admission was 57 and 7, respectively, per 100 000 in Québec and 33 and 7, respectively, per 100 000 in BC. In both provinces the risk of infant pertussis-related death over that period was <0.5 per 100?000. The NNV for parental immunization was at least 1 million to prevent 1 infant death, approximately 100 000 for ICU admission, and >10 000 for hospitalization.

Conclusions. In the context of low pertussis incidence, the parental cocoon program is inefficient and resource intensive for the prevention of serious outcomes in early infancy. Regions contemplating the cocoon program should consider the NNV based on local epidemiology.

Source: Clinical Infectious Diseases, (2012) 54 (3): 318-327