Spectrum of activity testing for therapeutics against all four dengue virus serotypes in AG129 mouse models: Proof-of-concept studies with the adenosine nucleoside inhibitor NITD-008.

Dengue is a mosquito-borne disease of global public health importance caused by four genetically and serologically related viruses (DENV-1 to DENV-4). Efforts to develop effective vaccines and therapeutics for dengue have been slowed by the paucity of preclinical models that mimic human disease. DENV-2 models in interferon receptor deficient AG129 mice were an important advance but only allowed testing against a single DENV serotype. We have developed complementary AG129 mouse models of severe disseminated dengue infection using strains of the other three DENV serotypes. Here we used the adenosine nucleoside inhibitor NITD-008 to show that these models provide the ability to perform comparative preclinical efficacy testing of candidate antivirals in vivo against the full-spectrum of DENV serotypes. Although NITD-008 was effective in modulating disease caused by all DENV serotypes, the variability in protection among DENV serotypes was greater than expected from differences in activity in in vitro testing studies emphasizing the need to undertake spectrum of activity testing to help in prioritization of candidate compounds for further development.

Evaluation of immunological markers of ovine vaginal irritation: Implications for preclinical assessment of non-vaccine HIV preventive agents.

The presence of genital inflammatory responses and a compromised vaginal epithelial barrier have been linked to an increased risk of HIV acquisition. It is important to assure that application of candidate microbicides designed to limit HIV transmission will not cause these adverse events. We previously developed high resolution in vivo imaging methodologies in sheep to assess epithelial integrity following vaginal application of a model microbicide, however characterization of genital inflammation in sheep has not been previously possible. In this study, we significantly advanced the sheep model by developing approaches to detect and quantify inflammatory responses resulting from application of a nonoxynol-9-containing gel known to elicit vaginal irritation. Vaginal application of this model microbicide resulted in foci of disrupted epithelium detectable by confocal endomicroscopy. Leukocytes also infiltrated the treated mucosa and the number and composition of leukocytes obtained by cervicovaginal lavage (CVL) were determined by differential staining and flow cytometry. By 18h post-treatment, a population comprised predominantly of granulocytes and monocytes infiltrated the vagina and persisted through 44h post-treatment. The concentration of proinflammatory cytokines and chemokines in CVL was determined by quantitative ELISA. Concentrations of IL-8 and IL-1ß were consistently significantly increased after microbicide application suggesting these cytokines are useful biomarkers for epithelial injury in the sheep model. Together, the results of these immunological assessments mirror those obtained in previous animal models and human trials with the same compound and greatly extend the utility of the sheep vaginal model in assessing the vaginal barrier and immune microenvironment.

Status of vaccine research and development of vaccines for Nipah virus.

Nipah virus (NiV) is a highly pathogenic, recently emerged paramyxovirus that has been responsible for sporadic outbreaks of respiratory and encephalitic disease in Southeast Asia. High case fatality rates have also been associated with recent outbreaks in Malaysia and Bangladesh. Although over two billion people currently live in regions in which NiV is endemic or in which the Pteropus fruit bat reservoir is commonly found, there is no approved vaccine to protect against NiV disease. This report examines the feasibility and current efforts to develop a NiV vaccine including potential hurdles for technical and regulatory assessment of candidate vaccines and the likelihood for financing.

Mouse models of dengue virus infection for vaccine testing.

Dengue is a mosquito-borne disease caused by four serologically and genetically related viruses termed DENV-1 to DENV-4. With an annual global burden of approximately 390 million infections occurring in the tropics and subtropics worldwide, an effective vaccine to combat dengue is urgently needed. Historically, a major impediment to dengue research has been development of a suitable small animal infection model that mimics the features of human illness in the absence of neurologic disease that was the hallmark of earlier mouse models. Recent advances in immunocompromised murine infection models have resulted in development of lethal DENV-2, DENV-3 and DENV-4 models in AG129 mice that are deficient in both the interferon-α/ß receptor (IFN-α/ß R) and the interferon-γ receptor (IFN-γR). These models mimic many hallmark features of dengue disease in humans, such as viremia, thrombocytopenia, vascular leakage, and cytokine storm. Importantly AG129 mice develop lethal, acute, disseminated infection with systemic viral loads, which is characteristic of typical dengue illness. Infected AG129 mice generate an antibody response to DENV, and antibody-dependent enhancement (ADE) models have been established by both passive and maternal transfer of DENV-immune sera. Several steps have been taken to refine DENV mouse models. Viruses generated by peripheral in vivo passages incur substitutions that provide a virulent phenotype using smaller inocula. Because IFN signaling has a major role in immunity to DENV, mice that generate a cellular immune response are desired, but striking the balance between susceptibility to DENV and intact immunity is complicated. Great strides have been made using single-deficient IFN-α/ßR mice for DENV-2 infection, and conditional knockdowns may offer additional approaches to provide a panoramic view that includes viral virulence and host immunity. Ultimately, the DENV AG129 mouse models result in reproducible lethality and offer multiple disease parameters to evaluate protection by candidate vaccines.

Entry of inflammatory cells into the mouse vagina following application of candidate microbicides: comparison of detergent-based and sulfated polymer-based agents.

BACKGROUND: Because topical microbicides designed to prevent the spread of sexually transmitted diseases may be applied frequently, it is important to ensure product safety as well as efficacy. A murine model was developed to test for induction of inflammatory responses following application of candidate microbicides. GOAL: A comparison was made of the induction of inflammation following vaginal application of detergent-based and sulfated polymer-based microbicides. STUDY DESIGN: Vaginal leukocytes were collected, identified, and quantified following microbicide application to detect the entry of inflammatory leukocytes into the vaginal lumen. RESULTS: Large numbers of neutrophils and macrophages entered the vaginal lumen following a single application of detergent-based microbicides. No significant increase in vaginal leukocytes was detected following a single or repeated application of sulfated polymer-based microbicides. CONCLUSION: Application of sulfated polymer-based microbicides was less likely to result in inflammatory responses than was application of detergent-based compounds. This murine model should prove useful as part of a screening process to prioritize candidate microbicides before clinical trial.