Arboviral vaccines for use in pregnant travelers.

Pregnant women traveling abroad can be exposed to a variety of arboviruses, primarily spread by mosquitoes or ticks. Some arboviral infections can be of particular concern for pregnant women or their fetuses. Vaccination is one preventive measure that can reduce the risk for infection. Several arboviral vaccines have been licensed for many years and can be used to prevent infection in travelers, namely Japanese encephalitis, yellow fever, and tick-borne encephalitis vaccines. Recommendations on use of these vaccines in pregnancy vary. Other arboviral vaccines have been licensed but are not indicated for use in pregnant travelers (e.g., dengue vaccines) or are in development (e.g., chikungunya, Zika vaccines). This review describes arboviral vaccines for travelers, focusing on women who are pregnant and those planning travel during pregnancy.

Hospital-based enhanced surveillance for West Nile virus neuroinvasive disease.

Accurate data on the incidence of West Nile virus (WNV) disease are important for directing public health education and control activities. The objective of this project was to assess the underdiagnosis of WNV neuroinvasive disease through laboratory testing of patients with suspected viral meningitis or encephalitis at selected hospitals serving WNV-endemic regions in three states. Of the 279 patients with cerebrospinal fluid (CSF) specimens tested for WNV immunoglobulin M (IgM) antibodies, 258 (92%) were negative, 19 (7%) were positive, and two (1%) had equivocal results. Overall, 63% (12/19) of patients with WNV IgM-positive CSF had WNV IgM testing ordered by their attending physician. Seven (37%) cases would not have been identified as probable WNV infections without the further testing conducted through this project. These findings indicate that over a third of WNV infections in patients with clinically compatible neurological illness might be undiagnosed due to either lack of testing or inappropriate testing, leading to substantial underestimates of WNV neuroinvasive disease burden. Efforts should be made to educate healthcare providers and laboratorians about the local epidemiology of arboviral diseases and the optimal tests to be used in different clinical situations.

Use of laboratory reports as predictors of West Nile virus disease cases, Texas, 2008-2012.

We evaluated laboratory reports as early indicators of West Nile virus (WNV) disease cases in Texas. We compared WNV laboratory results in the National Electronic Disease Surveillance System Base System (NBS) to WNV disease cases reported to the state health department from 2008 to 2012. We calculated sensitivity and positive predictive value (PPV) of NBS reports, estimated the number of disease cases expected per laboratory report, and determined lead and lag times. The sensitivity and PPV of NBS laboratory reports were 86% and 77%, respectively. For every 10 positive laboratory reports, we expect 9·0 (95% confidence interval 8·9-9·2) reported disease cases. Laboratory reports preceded case reports with a lead time of 7 days. Electronic laboratory reports provided longer lead times than manually entered reports (P < 0·01). NBS laboratory reports are useful estimates of future reported WNV disease cases and may provide timely information for planning public health interventions.

Current practices and evaluation of screening solid organ donors for West Nile virus.

The first cases of West Nile virus (WNV) transmitted through solid organ transplantation (SOT) were identified in 2002. Subsequently, 5 additional clusters have been reported to public health officials in the United States. Based upon a limited number of known cases, patients who acquire WNV from infected donor organs might be at higher risk for severe neurologic disease and death, compared with patients infected through mosquito bites. In response, some organ procurement organizations (OPOs) have instituted pre-transplant screening of organ donors for WNV infection. We evaluated the current practices, concerns, and challenges related to screening organ donors for WNV in the United States by reviewing the relevant medical literature and interviewing key stakeholders. Screening organ donors for WNV is not required by national policy. In 2008, 11 (19%) of 58 OPOs performed WNV screening using nucleic acid amplification testing (NAT). These OPOs differ in their screening strategies, NAT performed, and logistical challenges. Concerns of delays in receiving NAT results before transplant and potential false-positive results leading to organ wasting are limitations to more widespread screening. Furthermore, it is unknown if WNV screening practices decrease SOT-related morbidity and mortality, or if screening is cost-effective. Additional data are needed to assess and improve transplant outcomes related to WNV.

Completeness of West Nile virus testing in patients with meningitis and encephalitis during an outbreak in Arizona, USA.

Accurate data on West Nile virus (WNV) cases help guide public health education and control activities, and impact regional WNV blood product screening procedures. During an outbreak of WNV disease in Arizona, records from patients with meningitis or encephalitis were reviewed to determine the proportion tested for WNV. Of 60 patients identified with meningitis or encephalitis, 24 (40%) were tested for WNV. Only 12 (28%) of 43 patients aged <50 years were tested for WNV compared to 12 (71%) of 17 patients aged ≥50 years (P<0·01). Patients with clinical signs of weakness or paralysis, elevated CSF protein, admitted to an inpatient facility, or discharged to a rehabilitation facility were also more likely to have WNV testing performed. The lack of testing in younger age groups and in those with less severe disease probably resulted in substantial underestimates of WNV neuroinvasive disease burden.

Role of estrogen receptor alpha in hematopoietic stem cell development and B lymphocyte maturation in the male mouse.

Although estrogens and estrogen receptors (ERs) are known to function in the male brain and reproductive tract, few studies have evaluated their involvement in the male hematopoietic and immune systems. This study was undertaken to determine the role of ERalpha in hematopoietic progenitor and B lymphocyte maturation. ERalpha knockout (ER-/-), wild-type (ER+/+), and radiation chimeric (ERalpha positive or negative in either nonhematopoietic or hematopoietic elements, or both) male mice were used to determine target tissues. ER-/- and ER+/+ animals showed similar hematopoietic progenitor profiles, but the ER-/- animals had fewer cells in all bone marrow B lymphocyte subpopulations. Animals receiving a pharmacological dose (5 mg/kg BW) of 17beta-estradiol (E2) with both elements, ER+/+, had decreased early hematopoietic progenitors and a shift toward a mature B cell subpopulation, whereas animals with both elements, ER-/-, showed changes only in early hematopoietic progenitors. Hematopoietic element ER+/+ animals exhibited greater E2-induced hematopoietic progenitor and B lymphocyte alterations than those having only nonhematopoietic ERalpha. These data indicate that 1) ERalpha is not necessary for regulating male mouse normal hematopoietic progenitor cell proportions, but is involved in B cell regulation; and 2) ERalpha in hematopoietic elements is predominantly responsible for mediating E2-induced hematopoietic and B cell changes.

The aryl hydrocarbon receptor has a role in the in vivo maturation of murine bone marrow B lymphocytes and their response to 2,3,7,8-tetrachlorodibenzo-p-dioxin.

The ligand-activated aryl hydrocarbon receptor (AHR) is a cytosolic DNA binding protein. Although no biologic role for AHR has been elucidated, it mediates the immunotoxicity of xenobiotics such as 2, 3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), and its targeted inactivation produces abnormal immune system development. While investigators have demonstrated AHR's involvement in TCDD-induced B lymphocyte functional alterations, little is known about the receptor's possible role in early B cell maturation and whether exogenous ligands change this process. The purpose of this study was to determine, (1) whether bone marrow B lymphocyte maturation is affected by AHR presence, (2) if so, its relative importance in hematopoietic and/or nonhematopoietic elements and, (3) whether TCDD alters this process. Radiation chimeras were produced that were AHR positive (Ahr+/+) or negative (Ahr-/-) in either their nonhematopoietic or hematopoietic elements, or both. Marrow cells were analyzed for alterations in B lymphocyte maturation stage cell numbers in both vehicle- and TCDD-treated animals. Our results showed that (1) Ahr-/- animals had significantly higher numbers of pro/pre-B cells than Ahr+/+ animals, (2) TCDD treatment of Ahr+/+ animals produced a decrease in pro/pre-B cell numbers, whereas no effect was observed on Ahr-/- animals, and (3) AHR is required in both hematopoietic and stromal elements for maintenance of B cell subset maturation profiles.

Estrogen receptor alpha is necessary in thymic development and estradiol-induced thymic alterations.

Estrogens affect the development, maturation, and function of multiple organ systems, including the immune system. One of the main targets of estrogens in the immune system is the thymus, which undergoes atrophy and phenotypic alterations when exposed to elevated levels of estrogen. To determine how estrogens influence the thymus and affect T cell development, estrogen receptor alpha (ERalpha) knockout (ERKO) mice were examined. ERKO mice have significantly smaller thymi than their wild-type (WT) littermates. Construction of ER radiation bone marrow chimeras indicated that the smaller thymi were due to a lack of ERalpha in radiation-resistant tissues rather than hemopoietic elements. ERKO mice were also susceptible to estradiol-induced thymic atrophy, but the extent of their atrophy was less than what was seen in WT mice. The estradiol-treated ERKO mice failed, however, to manifest alterations in their thymic CD4/CD8 phenotypes compared with WT mice. Therefore, ERalpha is essential in nonhemopoietic cells to obtain a full-sized thymus, and ERalpha also mediates some of the response of the thymus to elevated estrogen levels. Finally, these results suggest that in addition to ERalpha, another receptor pathway is involved in estradiol-induced thymic atrophy.

A chimeric aryl hydrocarbon receptor knockout mouse model indicates that aryl hydrocarbon receptor activation in hematopoietic cells contributes to the hepatic lesions induced by 2,3,7, 8-tetrachlorodibenzo-p-dioxin.

Pathologic changes associated with 2,3,7, 8-tetrachlorodibenzo-p-dioxin (TCDD) exposure have been reported in the livers of a wide range of species. While these changes have been extensively described, the mechanisms of toxic interaction(s) that produce these lesions remain unclear. Using an aryl hydrocarbon receptor (Ahr) knockout male mouse chimeric model, we investigated whether the presence of this receptor in hematopoietic and/or parenchymal cells affects TCDD-induced hepatotoxicity. Bone marrow chimeras were produced by hematopoietic reconstitution of irradiated mice. Specifically, chimeras were generated with aryl hydrocarbon receptor (AHR) positive hematopoietic and parenchymal cells (Ahr+/+ animal bone marrow cells into irradiated Ahr+/+ animals), AHR positive hematopoietic and negative parenchymal cells (Ahr+/+ into Ahr-/-), AHR negative hematopoietic and positive parenchymal cells (Ahr-/- into Ahr+/+), and AHR negative hematopoietic and parenchymal cells (Ahr-/- into Ahr-/-). Male wild-type (Ahr+/+) and knockout (Ahr-/-) animals were used as nonchimeric controls. Following TCDD treatment (30 microg/kg body wt), liver sections from mice in each control and chimeric group were histologically evaluated for necrotic and inflammatory changes. TCDD treatment produced moderate inflammation in Ahr+/+ controls and Ahr+/+ into Ahr+/+ chimeras. This response was mild in TCDD-treated Ahr-/-, Ahr-/- into Ahr-/-, Ahr+/+ into Ahr-/-, and Ahr-/- into Ahr+/+ animals and was not different from the corresponding vehicle-treated groups. Moderate necrosis was observed in all TCDD-treated controls or chimeras with AHR-positive parenchyma. No or mild necrosis was observed in TCDD- and vehicle-treated animals containing AHR-negative parenchyma. These data indicate that the presence of AHR in hepatic parenchyma alone is sufficient for TCDD induction of hepatic necrosis, and its presence in hematopoietic cells is necessary for the inflammatory response to TCDD-induced hepatic lesions.

Overexpression of the anti-apoptotic oncogene, bcl-2, in the thymus does not prevent thymic atrophy induced by estradiol or 2,3,7, 8-tetrachlorodibenzo-p-dioxin.

Dexamethasone (Dex), estradiol (E2), and 2,3,7, 8-tetrachlorodibenzo-p-dioxin (TCDD) all affect the immune system, causing immunosuppression and thymic atrophy. It is still uncertain how and where these compounds act to induce thymic atrophy. However, it has been suggested that these compounds may have similar actions and targets, i.e., apoptosis of immature thymocytes for Dex and TCDD and preferential targeting of double-positive cells by Dex and E2. The lckpr-bcl-2 transgenic mouse has been shown to be protected against Dex-induced thymic atrophy. We used this murine model to determine if bcl-2 expression would also protect against E2- and TCDD-induced thymic atrophy. Our results indicate that, although the bcl-2 transgenic (TG+) mice were fully protected from atrophy induced by a single dose of Dex, atrophy was still induced in these mice following treatment with E2 or TCDD. Phenotypic analysis of thymocytes from TG- and TG+ mice also showed distinct consequences of atrophy induced by Dex, E2, and TCDD. Finally, since there are alternative pathways for apoptosis that are bcl-2 independent, both TG- and TG+ thymocytes were examined directly for indications of apoptosis using the TUNEL assay. After TCDD and E2 treatment there were no detectable signs of apoptosis in either TG- or TG+ mice even at early time points and at elevated dose levels. These results indicate that there are distinct mechanisms for the actions of Dex, E2, and TCDD in the thymus and that apoptosis is not a key mechanism of E2- and TCDD-induced thymic atrophy.

Thymic alterations induced by 2,3,7,8-tetrachlorodibenzo-p-dioxin are strictly dependent on aryl hydrocarbon receptor activation in hemopoietic cells.

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) and related congeners affect the immune system, causing immunosuppression and thymic atrophy in a variety of animal species. TCDD is believed to exert its effects primarily through the ligand-activated transcription factor, the aryl hydrocarbon receptor (AhR). Although the AhR is found at high levels in both thymocytes and thymic stroma, it is uncertain in which cells TCDD is activating the AhR to cause alterations in the thymus. Some investigators have suggested that stromal elements, primarily epithelial cells, within the thymus are the primary targets for TCDD. Others have suggested that atrophy is due to a direct effect on thymocytes, either by apoptosis or by altering the development of progenitor cells. By producing chimeric mice with TCDD-responsive (AhR[+/+]) stromal components and TCDD-unresponsive (AhR[-/-]) hemopoietic components, or the reverse, we have clarified the role of stromal vs hemopoietic elements in TCDD-induced thymic alterations. Our results show that the targets for TCDD-induced thymic atrophy and phenotypic alterations are strictly in the hemopoietic compartment and that TCDD activation of epithelial cells in the stroma is not required for thymic alterations. Furthermore, changes observed in the putative stem cell populations of these chimeric mice are also dependent on TCDD activation of the AhR in hemopoietic elements.

Molecular cloning of L-JAK, a Janus family protein-tyrosine kinase expressed in natural killer cells and activated leukocytes.

Protein-tyrosine kinases (PTKs) are critical enzymes for receptor-mediated signaling in lymphocytes. Because natural killer (NK) cells are large granular lymphocytes with specialized effector function, we set out to identify PTKs preferentially expressed in these cells. One such PTK was identified and molecularly cloned. The predicted amino acid sequence shows that this kinase lacks SH2 or SH3 domains typical of src family kinases but has tandem nonidentical catalytic domains, indicating that it is a member of the Janus family of PTKs. Immunoprecipitation using antiserum generated against a peptide corresponding to the deduced amino acid sequence of this gene revealed a kinase with a molecular weight of approximately 125,000. The pattern of expression of this kinase contrasted sharply with that of other Janus kinases, which are ubiquitously expressed. The kinase described in the present study was found to be more limited in its expression; expression was found in NK cells and an NK-like cell line but not in resting T cells or in other tissues. In contrast, stimulated and transformed T cells expressed the gene, suggesting a role in lymphoid activation. Because of its homology and tissue expression, we have tentatively termed this PTK gene L-JAK for leukocyte Janus kinase.

Molecular cloning of lsk, a carboxyl-terminal src kinase (csk) related gene, expressed in leukocytes.

Regulation of the activity of src-family kinases is thought to occur, in part, through the phosphorylation of conserved carboxyl-terminal tyrosine residues. Although the src-family includes several molecules with tissue or cell-type restricted expression, the only kinase implicated in the regulatory phosphorylation of these enzymes is p50csk. Herein we report the molecular cloning of a tissue specific p50csk-related gene. Like p50csk, the deduced protein sequence of this novel cDNA includes a tyrosine kinase catalytic domain, SH2 and SH3 domains, a short amino terminus, and no autophosphorylation or carboxyl-terminal tyrosine residues. Additionally, neither this novel kinase nor p50csk contain the amino-terminal myristoylation site characteristic of the src-family. However, whereas csk is ubiquitously expressed, mRNA corresponding to this novel gene is expressed in brain, natural killer (NK) cells, and activated T cells but not in a variety of other tissues and cell lines. In agreement with the mRNA expression pattern, antiserum reactive with the predicted carboxyl-terminus of the cDNA recognizes a 57 kDa polypeptide in immunoblots of NK cells and PHA-activated T cells. Because of its limited expression and high homology to p50csk, we named this gene lsk; leukocyte carboxyl-terminal src kinase related gene. Identification of a molecule like lsk suggests the existence of tissue specific src-regulatory pathways that function in activated lymphocytes.