American Society for Microbiology

Nhiễm virus West Nile (WNV) lần đầu có thể được chẩn đoán thông qua một số phương pháp xét nghiệm phát hiện các hạt virus, axit nucleic, và kháng thể IgM và/hoặc IgG đặc hiệu. Tuy nhiên, việc xác định huyết thanh của tác nhân gây bệnh trong các nhiễm flavivirus thứ cấp hoặc sau này là vấn đề khó khăn do khả năng phản ứng chéo rộng rãi của các kháng thể flavivirus. Điều này đặc biệt khó khăn ở các vùng nhiệt đới châu Mỹ nơi mà nhiều flavivirus tồn tại đồng thời. Một nghiên cứu về nhiễm flavivirus liên tiếp ở ngựa đã được tiến hành sử dụng ba flavivirus quan trọng về mặt y tế và năm xét nghiệm chẩn đoán được sử dụng rộng rãi để xác định liệu nhiễm WNV ở ngựa đã từng bị nhiễm virus viêm não St. Louis (SLEV) hoặc virus dengue type 2 (DENV-2) có thể được chẩn đoán hay không. Sau khi tiêm phòng ban đầu, 25% (3/12) và 75% (3/4) ngựa đã tạo ra phản ứng kháng thể đối với SLEV và DENV-2, tương ứng. Tám mươi tám phần trăm ngựa được tiêm tiếp theo bằng WNV có phản ứng kháng thể đặc hiệu đối với WNV mà có thể được phát hiện bằng một trong các xét nghiệm này. Xét nghiệm trung hòa giảm tấm (PRNT) có độ nhạy cao trong phát hiện nhưng thiếu tính đặc hiệu, đặc biệt là sau khi tiếp xúc flavivirus lặp đi lặp lại. Xét nghiệm enzyme liên kết immunosorbent IgM đặc hiệu WNV (IgM ELISA) có khả năng phát hiện phản ứng kháng thể IgM và không có phản ứng chéo trong phản ứng SLEV hoặc DENV ban đầu. Xét nghiệm ELISA chặn đặc hiệu WNV cho kết quả tích cực chỉ sau khi một mũi tiêm WNV. Điều quan trọng là, chúng tôi đã chứng minh rằng thời điểm thu thập mẫu và nhu cầu sử dụng nhiều mẫu là rất quan trọng, vì tác nhân gây bệnh có thể bị chẩn đoán sai nếu chỉ kiểm tra một mẫu duy nhất.

Coordination of the primary defense mechanisms against pathogens relies on the appropriate expression of pathogen recognition receptors (PRRs) triggering the early release of effector molecules of the innate immune system. To analyze the impact of this system on the counteraction of infections of the mammary gland (mastitis), we characterized the bovine gene encoding the key PRR Toll-like receptor 9 (TLR9) and mapped its precise position on chromosome BTA22. The sequence information was used to establish real-time PCR quantification assays to measure the mRNA abundances of TLR9, TLR2, and TLR4 together with those of β-defensin 5 (BNBD5), an early bactericidal effector molecule of the innate system, in healthy and infected mammary glands. Mastitis strongly increased (4- to 13-fold) the mRNA abundances of all of these genes except TLR9. Slight subclinical infections already caused a substantial increase in the copy numbers, though they did so the least for TLR9. Induction was not systemic, since mRNA abundance was low in uninfected control quarters of the udder but high in the severely infected quarters of the same animal. The number of TLR2 copies correlated well with those of TLR4, indicating coordinated regulation of these two PRRs during infection of the udder. Their coordinated regulation explains our unexpected observation that pureStaphylococcus aureusinfections caused a strong increase also in TLR4 mRNA abundance. In situ hybridizations revealed that BNBD5 is expressed predominantly in the mammary epithelial cells (MEC) of the infected gland. Our data therefore suggest a significant contribution of the innate immune system to counteract mastitis and attribute a prominent effector function to the MEC.

We used a severe challenge model that produces clinical West Nile virus (WNV) disease to test the efficacy of three commercially available equine WNV vaccines in horses. Twenty-four healthy, WNV-seronegative horses of varying ages and genders were placed, in random and blind manner, into three trial groups consisting of eight horses each; two horses in each group received (i) an inactivated WNV vaccine (K-WN), (ii) a modified-live vaccine (CP-WN) containing the WNV prM and E proteins expressed by a canarypox vector, (iii) a live-chimera vaccine (WN-FV) containing WNV prM and E proteins expressed in a YF17D vector, or (iv) a diluent control. Challenge by this model caused grave neurological signs, viremia, moderate to severe histopathologic lesions in the brain and spinal cord, and an outcome of 0% survivorship in all six control horses. In contrast, challenge in horses at between 28 days postvaccination with the chimera vaccine and 56 days postvaccination with the commercial inactivated or modified-live vaccine resulted in 100% survivorship (protection from the onset of WNV encephalitis and viremia). Horses vaccinated with the live-chimera vaccine showed significantly fewer clinical signs than did the control horses ( P ≤ 0.01) and the horses vaccinated with inactivated vaccine ( P = 0.035). Mild residual inflammatory lesions were seen in a few of the vaccinated horses.

The leptospiral immunoglobulin-like (Lig) proteins LigA and LigB possess immunoglobulin-like domains with 90-amino-acid repeats and are adhesion molecules involved in pathogenicity. They are conserved in pathogenicLeptospiraspp. and thus are of interest for use as serodiagnostic antigens and in recombinant vaccine formulations. The N-terminal amino acid sequences of the LigA and LigB proteins are identical, but the C-terminal sequences vary. In this study, we evaluated the protective potential of five truncated forms of LigA and LigB proteins fromLeptospira interrogansserovar Canicola as DNA vaccines using the pTARGET mammalian expression vector. Hamsters immunized with the DNA vaccines were subjected to a heterologous challenge withL. interrogansserovar Copenhageni strain Spool via the intraperitoneal route. Immunization with a DNA vaccine encoding LigBrep resulted in the survival of 5/8 (62.5%) hamsters against lethal infection (P< 0.05). None of the control hamsters or animals immunized with the other vaccine preparations survived. The vaccine induced an IgG antibody response and, additionally, conferred sterilizing immunity in 80% of the surviving animals. Our results indicate that the LigBrep DNA vaccine is a promising candidate for inclusion in a protective leptospiral vaccine.

Leptospirosis, a worldwide zoonosis, lacks an effective, safe, and cross-protective vaccine. LipL32, the most abundant, immunogenic, and conserved surface lipoprotein present in all pathogenic species ofLeptospira, is a promising antigen candidate for a recombinant vaccine. However, several studies have reported a lack of protection when this protein is used as a subunit vaccine. In an attempt to enhance the immune response, we used LipL32 coupled to or coadministered with the B subunit of theEscherichia coliheat-labile enterotoxin (LTB) in a hamster model of leptospirosis. After homologous challenge with 5× the 50% lethal dose (LD₅₀) ofLeptospira interrogans, animals vaccinated with LipL32 coadministered with LTB and LTB::LipL32 had significantly higher survival rates (P< 0.05) than animals from the control group. This is the first report of a protective immune response afforded by a subunit vaccine using LipL32 and represents an important contribution toward the development of improved leptospirosis vaccines.

The transforming growth factor β1/interleukin-31 (TGF-β1/IL-31) pathway plays an important role in the process of cell injury and inflammation. The purpose of this work was to explore the role of the TGF-β1/IL-31 pathway in the cytopathic process of hepatitis B virus (HBV)-related acute-on-chronic liver failure (ACLF). The quantitative serum levels of TGF-β1, IL-9, IL-10, IL-17, IL-22, IL-23, IL-31, IL-33, and IL-35 were analyzed among chronic hepatitis B (CHB) patients (n= 17), ACLF patients (n= 18), and normal control (NC) subjects (n= 18). Disease severity in patients with ACLF was assessed using the model for end-stage liver disease (MELD) and Child-Pugh scores. Serum TGF-β1 levels were strongly positively correlated with IL-31 in all subjects, and both of them were positively correlated with IL-17, IL-22, and IL-33. In CHB and ACLF patients, serum levels of TGF-β1 and IL-31 were both increased significantly compared with those in NC subjects and positively correlated with total bilirubin (TBil) and alpha-fetoprotein (AFP) levels. ACLF patients showed the highest levels of TGF-β1 and IL-31, which were positively correlated with Child-Pugh scores. Furthermore, the recovery from the liver injury in CHB was accompanied by decreased TGF-β1 and IL-31 levels. More importantly, serum levels of TGF-β1 and IL-31 were markedly upregulated in ACLF nonsurvivors, and IL-31 displayed the highest sensitivity and specificity (85.7% and 100.0%, respectively) in predicting nonsurvival of ACLF patients. Increasing activity of the TGF-β1/IL-31 pathway is well correlated with the extent of liver injury, disease severity, and nonsurvival of ACLF patients, while reducing activity is detected along the recovery from liver injury in CHB, suggesting its potential role in the pathogenesis of liver injury during chronic HBV infection.

Dendritic cells (DCs) are antigen-presenting cells with the ability to induce primary immune responses necessary in innate immunity and adaptive immunity. Osteopontin (OPN) is a secreted acidic phosphoprotein containing an arginine-glycine-aspartate sequence and has been suggested to play an important role in early cellular immune responses. The interaction between DCs and OPN has not been clarified. We hypothesized that there is an important interaction between DCs and OPN, which is an indispensable extracellular matrix component in early cellular immune responses. Human monocyte-derived DCs synthesized OPN especially during the differentiation from monocytes to immature DCs. By blocking of OPN with anti-OPN antibody, cultured DCs became smaller and expressed lower levels of costimulatory molecules and major histocompatibility complex class II antigens than untreated DCs. Furthermore, DCs treated with anti-OPN antibody easily underwent apoptosis. These results suggest that human DCs can produce OPN and that OPN may play a role in the differentiation, maturation, and survival of DCs by autocrine and/or paracrine pathways.

Noroviruses are the leading cause of acute gastroenteritis worldwide, and norovirus vaccine prevention strategies are under evaluation. The immunogenicity of two doses of bivalent genogroup 1 genotype 1 (GI.1)/GII.4 (50 μg of virus-like particles [VLPs] of each strain adjuvanted with aluminum hydroxide and 3- O -desacyl-4′monophosphoryl lipid A [MPL]) norovirus vaccine administered to healthy adults in a phase 1/2 double-blind placebo-controlled trial was determined using virus-specific serum total antibody enzyme-linked immunosorbent assay (ELISA), IgG, IgA, and histoblood group antigen (HBGA)-blocking assays. Trial participants subsequently received an oral live virus challenge with a GII.4 strain, and the vaccine efficacy results were reported previously (D. I. Bernstein et al., J Infect Dis 211:870–878, 2014, doi: 10.1093/infdis/jiu497 ). This report assesses the impact of prechallenge serum antibody levels on infection and illness outcomes. Serum antibody responses were observed in vaccine recipients by all antibody assays, with first-dose seroresponse frequencies ranging from 88 to 100% for the GI.1 antigen and from 69 to 84% for the GII.4 antigen. There was little increase in antibody levels after the second vaccine dose. Among the subjects receiving the placebo, higher prechallenge serum anti-GII.4 HBGA-blocking and IgA antibody levels, but not IgG or total antibody levels, were associated with a lower frequency of virus infection and associated illness. Notably, some placebo subjects without measurable serum antibody levels prechallenge did not become infected after norovirus challenge. In vaccinees, anti-GII.4 HBGA-blocking antibody levels of >1:500 were associated with a lower frequency of moderate-to-severe vomiting or diarrheal illness. In this study, prechallenge serum HBGA antibody titers correlated with protection in subjects receiving the placebo; however, other factors may impact the likelihood of infection and illness after virus exposure. (This study is registered at ClinicalTrials.gov under registration number NCT1609257.)

We describe the development and evaluation of a rapid diagnostic test for Vibrio cholerae O1 and O139 based on lipopolysaccharide detection using gold particles. The specificity ranged between 84 and 100%. The sensitivity of the dipsticks ranged from 94.2 to 100% when evaluated with stool samples obtained in Madagascar and Bangladesh. The dipstick can provide a simple tool for epidemiological surveys.

In the context of a serosurvey conducted on the Anaplasma marginale prevalence in Swiss cattle, we suspected that a serological cross-reactivity between A. marginale and A. phagocytophilum might exist. In the present study we demonstrate that cattle, sheep and horses experimentally infected with A. phagocytophilum not only develop antibodies to A. phagocytophilum (detected by immunofluorescent-antibody assay) but also to A. marginale (detected by a competitive enzyme-linked immunosorbent assay). Conversely, calves experimentally infected with A. marginale also developed antibodies to A. phagocytophilum using the same serological tests. The identity of 63% determined in silico within a 209-amino-acid sequence of major surface protein 5 of an isolate of A. marginale and one of A. phagocytophilum supported the observed immunological cross-reactivity. These observations have important consequences for the serotesting of both, A. marginale and A. phagocytophilum infection of several animal species. In view of these new findings, tests that have been considered specific for either infection must be interpreted carefully.