CCR5 deficiency increases risk of symptomatic West Nile virus infection

West Nile virus (WNV) is a reemerging pathogen that causes fatal encephalitis in several species, including mouse and human. Recently, we showed that the chemokine receptor CCR5 is critical for survival of mice infected with WNV, acting at the level of leukocyte trafficking to the brain. To test whether this receptor is also protective in man, we determined the frequency of CCR5Δ32, a defective CCR5 allele found predominantly in Caucasians, in two independent cohorts of patients, one from Arizona and the other from Colorado, who had laboratory-confirmed, symptomatic WNV infection. The distribution of CCR5Δ32 in a control population of healthy United States Caucasian random blood donors was in Hardy-Weinberg equilibrium and CCR5Δ32 homozygotes represented 1.0% of the total group (n = 1,318). In contrast, CCR5Δ32 homozygotes represented 4.2% of Caucasians in the Arizona cohort (odds ratios [OR] = 4.4 [95% confidence interval [CI], 1.6–11.8], P = 0.0013) and 8.3% of Caucasians in the Colorado cohort (OR = 9.1 [95% CI, 3.4–24.8], P < 0.0001). CCR5Δ32 homozygosity was significantly associated with fatal outcome in the Arizona cohort (OR = 13.2 [95% CI, 1.9–89.9], P = 0.03). We conclude that CCR5 mediates resistance to symptomatic WNV infection. Because CCR5 is also the major HIV coreceptor, these findings have important implications for the safety of CCR5-blocking agents under development for HIV/AIDS

Bat-associated Rabies Virus in Skunks

Rabies was undetected in terrestrial wildlife of northern Arizona until 2001, when rabies was diagnosed in 19 rabid skunks in Flagstaff. Laboratory analyses showed causative rabies viruses associated with bats, which indicated cross-species transmission of unprecedented magnitude. Public health infrastructure must be maintained to address emerging zoonotic diseases

Bat-Associated Rabies Virus in Skunks

Rabies was undetected in terrestrial wildlife of northern Arizona until 2001, when rabies was diagnosed in 19 rabid skunks in Flagstaff. Laboratory analyses showed causative rabies viruses associated with bats, which indicated cross-species transmission of unprecedented magnitude. Public health infrastructure must be maintained to address emerging zoonotic diseases. In North America, >90% of cases of rabies in animals occur in wildlife (1); several mammalian taxa harbor characteristic rabies virus variants (RABVV). In Arizona, skunks (Mephitis mephitis) and gray foxes (Urocyon cinereoargenteus) maintain independent rabies enzootic cycles, and in indigenous bats, rabies has been diagnosed in 14 of 28 species (Arizona Department of Health Services, unpub. data). Although skunks live throughout Arizona, until 2001, rabid skunks had been found only in the southeastern quadrant of the state. In the United States, but RABVV are a source of infection for humans and other mammals (2-8). Typically, interspecies infection produces a single fatal spillover event; secondary transmission has rarely been observed. Antigenic typing of rabid carnivores in Arizona from 1996 through 2000 identified bat RABVV in 1 domestic dog and 2 gray foxes. This report describes the largest documented rabies epizootic among terrestrial mammals infected with bat RABVV, with perpetuated animal-to-animal transmission. Coincident with the zoonotic disease significance, this report provides contemporary insight into pathogen evolution (9).Clinical Laboratory Scienc

Validation of a Microsphere-Based Immunoassay for Detection of Anti-West Nile Virus and Anti-St. Louis Encephalitis Virus Immunoglobulin M Antibodies▿

A microsphere-based immunoassay (MIA) was previously developed that is capable of determining the presence of anti-West Nile (WN) virus or anti-St. Louis encephalitis (SLE) virus immunoglobulin M (IgM) antibodies in human serum or cerebrospinal fluid. The original data set on which the classification rules were based comprised 491 serum specimens obtained from the serum bank at the Division of Vector-Borne Infectious Diseases of the Centers for Disease Control and Prevention (DVBID). The classification rules were used to provide a result and to determine whether confirmatory testing was necessary for a given sample. A validation study was coordinated between the DVBID and five state health laboratories to determine (i) the reproducibility of the test between different laboratories, (ii) the correlation between the IgM-enzyme-linked immunosorbent assay (MAC-ELISA) and the MIA, and (iii) whether the initial nonspecific parameters could be refined to reduce the volume of confirmatory testing. Laboratorians were trained in the method, and reagents and data analysis software developed at the DVBID were shipped to each validating laboratory. Validating laboratories performed tests on approximately 200 samples obtained from their individual states, the collections of which comprised approximately equal numbers of WN virus-positive and -negative samples, as determined by MAC-ELISA. In addition, 377 samples submitted to the DVBID for arbovirus testing were analyzed using the MIA and MAC-ELISA at the DVBID only. For the specimens tested at both the state and the DVBID laboratories, a correlation of results indicated that the technology is readily transferable between laboratories. The detection of IgM antibodies to WN virus was more consistent than detection of IgM antibodies to SLE virus. Some changes were made to the analysis software that resulted in an improved accuracy of diagnosis

Growth factors mobilize CXCR4 low/negative primitive hematopoietic stem/progenitor cells from the bone marrow of nonhuman primates

AbstractThe chemokine receptor CXCR4 is expressed by CD34+ hematopoietic stem/progenitor cells (HSC/HPC). Several investigators have suggested that expression of CXCR4 may be an important characteristic of HSC/HPC. We studied the dynamic expression of CXCR4 during growth factor-induced mobilization of HSC in a clinically relevant nonhuman primate model, Papio anubis (baboons). We evaluated whether CXCR4 expression in HSC/HPC varies during steady-state hematopoiesis as well as during growth factor-induced mobilization. Peripheral blood stem cells from 5 baboons were mobilized with growth factors. During mobilization, there was a consistent stepwise increase in the proportion of peripheral blood CD34+ cells that were CXCR4−. The highest number of CD34+CXCR4− cells appeared in the peripheral blood at the same time as the maximum number of assayable colony-forming cells. The cloning efficiency of the CD34+CXCR4− population was 3-fold greater than that of CD34+CXCR4+ cells, and the frequency of cobblestone area-forming cells was 6 times higher in the CD34+CXCR4− population in comparison to CD34+CXCR4+ cells. Furthermore, the most quiescent CD34+ cells isolated on the basis of low Hoechst 33342 (Ho) and rhodamine 123 (Rho) staining (HoLow/RhoLow) were highly enriched in the CXCR4Low/− cell population. Ex vivo incubation of mobilized peripheral blood CD34+ cells with growth factors for 40 hours resulted in increasing numbers of cells expressing CXCR4. Peripheral blood stem cell grafts containing CD34+ cells that consisted of predominantly CXCR4− cells were able to rapidly engraft lethally irradiated baboons. Because the overwhelming number of CD34+ cells within the mobilized peripheral blood grafts were CXCR4− and were capable of rescuing lethally irradiated baboons, it seems unlikely that the expression of CXCR4 in vitro is an absolute requirement for HSC homing and engraftment. In summary, our data suggest the dynamic nature of CXCR4 expression on CD34+ cells during growth factor-induced HSC/HPC mobilization. In addition, our data indicate that the lack of CXCR4 expression is possibly a characteristic of relatively more primitive HSC/HPC characterized by a higher proliferative capacity