PD-1 of Sigmodon hispidus: Gene identification, characterization and preliminary evaluation of expression in inactivated RSV vaccine-induced enhanced respiratory disease.

Sigmodon hispidus or cotton rat is an excellent animal model for studying human infections of respiratory viruses including respiratory syncytial virus (RSV), which is the leading cause of hospitalization in infants and causes high rates of infection in the elderly and immunocompromised patient populations. Despite several decades of research, no vaccine has been licensed whereas inactivated vaccines have been shown to induce severe adverse reaction in a clinical trial, with other forms of RSV vaccine also found to induce enhanced disease in preclinical animal studies. While arguably the cotton rat is the best small animal model for evaluation of RSV vaccines and antivirals, many important genes of the immune system remain to be isolated. Programmed cell death-1 (PD-1) plays an integral role in regulating many aspects of immunity by inducing suppressive signals. In this study, we report the isolation of mRNA encoding the cotton rat PD-1 (crPD-1) and characterization of the PD-1 protein. crPD-1 bound to its cognate ligand on dendritic cells and effectively suppressed cytokine secretion. Moreover, using the newly acquired gene sequence, we observed a decreased level of crPD-1 levels in cotton rats with enhanced respiratory disease induced by inactivated RSV vaccine, unraveling a new facet of vaccine-induced disease.

Chitosan alters inactivated respiratory syncytial virus vaccine elicited immune responses without affecting lung histopathology in mice.

Chitosan is a polysaccharide capable of augmenting immune responses with a proven safety record in animals and humans. These properties make it a potentially attractive agent for the prevention and treatment of infectious disease. Infection by respiratory syncytial virus (RSV) is the leading cause of serious lower respiratory disease in young children throughout the world. There is no licensed vaccine available against RSV whereas inactivated vaccine is known to cause enhanced respiratory disease instead of protection. Here, we investigated whether chitosan administered one or three days post-infection could protect animals against RSV infection and whether it could alter immune responses or immunopathology induced by inactivated RSV vaccine when administered twice before RSV infection. We found chitosan could modestly protect animals against RSV infection when given post-infection, while, in conjunction with inactivated RSV vaccine when given pre-infection, it could significantly reduce RSV infection in mice. Further mechanistic investigation revealed that chitosan enhanced antigen-specific immune responses through augmenting the induction of regulatory T cells, lung resident T cells and neutralizing antibodies while reversing Th2-skewed immune responses induced by inactivated RSV vaccine but, surprisingly, failing to reverse lung histopathology. Overall, this study sheds more light on the molecular mechanisms underlying inactivated RSV vaccine-induced disease.

Unveiling Integrated Functional Pathways Leading to Enhanced Respiratory Disease Associated With Inactivated Respiratory Syncytial Viral Vaccine.

Respiratory syncytial virus (RSV) infection is a severe threat to young children and the elderly. Despite decades of research, no vaccine has been approved. Notably, instead of affording protection, a formalin-inactivated RSV vaccine induced severe respiratory disease including deaths in vaccinated children in a 1960s clinical trial; however, recent studies indicate that other forms of experimental vaccines can also induce pulmonary pathology in pre-clinical studies. These findings suggest that multiple factors/pathways could be involved in the development of enhanced respiratory diseases. Clearly, a better understanding of the mechanisms underlying such adverse reactions is critically important for the development of safe and efficacious vaccines against RSV infection, given the exponential growth of RSV vaccine clinical trials in recent years. By employing an integrated systems biology approach in a pre-clinical cotton rat model, we unraveled a complex network of pulmonary canonical pathways leading to disease development in vaccinated animals upon subsequent RSV infections. Cytokines including IL-1, IL-6 GRO/IL-8, and IL-17 in conjunction with mobilized pulmonary inflammatory cells could play important roles in disease development, which involved a wide range of host responses including exacerbated pulmonary inflammation, oxidative stress, hyperreactivity, and homeostatic imbalance between coagulation and fibrinolysis. Moreover, the observed elevated levels of MyD88 implicate the involvement of this critical signal transduction module as the central node of the inflammatory pathways leading to exacerbated pulmonary pathology. Finally, the immunopathological consequences of inactivated vaccine immunization and subsequent RSV exposure were further substantiated by histological analyses of these key proteins along with inflammatory cytokines, while hypercoagulation was supported by increased pulmonary fibrinogen/fibrin accompanied by reduced levels of plasma D-dimers. Enhanced respiratory disease associated with inactivated RSV vaccine involves a complex network of host responses, resulting in significant pulmonary lesions and clinical manifestations such as tachypnea and airway obstruction. The mechanistic insight into the convergence of different signal pathways and identification of biomarkers could help facilitate the development of safe and effective RSV vaccine and formulation of new targeted interventions.

Targeting CD40 enhances antibody- and CD8-mediated protection against respiratory syncytial virus infection.

Respiratory Syncytial Virus (RSV) infects almost all children under the age of one and is the leading cause of hospitalization among infants. Despite several decades of research with dozens of candidate vaccines being vigorously evaluated in pre-clinical and clinical studies, there is no licensed vaccine available to date. Here, the RSV fusion protein (F) was fused with CD40 ligand and delivered by an adenoviral vector into BALB/c mice where the CD40 ligand serves two vital functions as a molecular adjuvant and an antigen-targeting molecule. In contrast to a formaldehyde-inactivated vaccine, the vectored vaccine effectively protected animals against RSV without inducing enhanced respiratory disease. This protection involved a robust induction of neutralizing antibodies and memory CD8 T cells, which were not observed in the inactivated vaccine group. Finally, the vectored vaccine was able to elicit long-lasting protection against RSV, one of the most challenging issues in RSV vaccine development. Further studies indicate that the long lasting protection elicited by the CD40 ligand targeted vaccine was mediated by increased levels of effector memory CD8 T cell 3 months post-vaccination.

Identification and characterisation of the CD40-ligand of Sigmodon hispidus.

Cotton rats are an important animal model to study infectious diseases. They have demonstrated higher susceptibility to a wider variety of human pathogens than other rodents and are also the animal model of choice for pre-clinical evaluations of some vaccine candidates. However, the genome of cotton rats remains to be fully sequenced, with much fewer genes cloned and characterised compared to other rodent species. Here we report the cloning and characterization of CD40 ligand, whose human and murine counterparts are known to be expressed on a range of cell types including activated T cells and B cells, dendritic cells, granulocytes, macrophages and platelets and exerts a broad array of immune responses. The cDNA for cotton rat CD40L we isolated is comprised of 1104 nucleotides with an open reading frame (ORF) of 783bp coding for a 260 amino acid protein. The recombinant cotton rat CD40L protein was recognized by an antibody against mouse CD40L. Moreover, it demonstrated functional activities on immature bone marrow dendritic cells by upregulating surface maturation markers (CD40, CD54, CD80, and CD86), and increasing IL-6 gene and protein expression. The availability of CD40L gene identity could greatly facilitate mechanistic research on pathogen-induced-immunopathogenesis and vaccine-elicited immune responses.

Identification of immunodominant CD8 epitope in the stalk domain of influenza B viral hemagglutinin.

Human infections by type B influenza virus constitute about 25% of all influenza cases. The viral hemagglutinin is comprised of two subunits, HA1 and HA2. While HA1 is constantly evolving in an unpredictable fashion, the HA2 subunit is highly conserved, making it a potential candidate for a universal vaccine. However, immunodominant epitopes in the HA2 subunit remain largely unknown. To delineate MHC Class I epitopes, we first identified 9-mer H-2Kd-restricted CD8 T cell epitopes in the HA2 domain by in silico analyses, followed by evaluating the immunodominance of these peptides in mice challenged with the virus. Of three peptides selected through in silico analysis, the universally conserved peptide, YYSTAASSL (B/HA2-190), possessed the highest predicted binding affinity to MHC Class I and was most effective in inducing IL-2 and TNF-α in mouse splenocytes. Importantly, the peptide demonstrated best capability of stimulating peptide-specific ex-vivo cytotoxicity against target cells. Taken together, this finding would be of value for assessment of cell-mediated immune responses elicited by vaccines based on the highly conserved HA2 stalk domain.

Further Evidence that Human Endogenous Retrovirus K102 is a Replication Competent Foamy Virus that may Antagonize HIV-1 Replication.

OBJECTIVE: The goals of the research were to determine if a foamy effect on macrophages was due to human endogenous retrovirus K102 (HERV-K102) replication, and to further address its potential significance in HIV-1 infection. METHODS: An RT-PCR HERV-K HML-2 pol method was used to screen the unknown HERV, and isolated bands were sent for sequencing. Confirmation of RNA expression was performed by a real time quantitative PCR (qPCR) pol ddCt method. Rabbit antibodies to Env peptides were used to assess expression by immunohistology and processing of Env by western blots. A qPCR pol ddCt method to ascertain genomic copy number was performed on genomic DNA isolated from plasma comparing HIV-1 exposed seronegative (HESN) commercial sex workers (CSW) to normal controls and contrasted with HIV-1 patients. RESULTS: HERV-K102 expression, particle production and replication were associated with foamy macrophage generation in the cultures of cord blood mononuclear cells under permissive conditions. A five-fold increased HERV-K102 pol genomic copy number was found in the HESN cohort over normal which was not found in HIV-1 positive patients (p=0.0005). CONCLUSIONS: This work extends the evidence that HERV-K102 has foamy virus attributes, is replication competent, and is capable of high replication rate in vivo and in vitro. This may be the first characterization of a replication-competent, foamy-like virus of humans. High particle production inferred by increased integration in the HESN cohort over HIV-1 patients raises the issue of the clinical importance of HERV-K102 particle production as an early protective innate immune response against HIV-1 replication.

Universal anti-neuraminidase antibody inhibiting all influenza A subtypes.

The only universally conserved sequence amongst all influenza A viral neuraminidase (NA) is located between amino acids 222-230 and plays crucial roles in viral replication. However, it remained unclear as to whether this universal epitope is exposed during the course of infection to allow binding and inhibition by antibodies. Using a monoclonal antibody (MAb) targeting this specific epitope, we demonstrated that all nine subtypes of NA were inhibited in vitro by the MAb. Moreover, the antibody also provided heterosubtypic protection in mice challenged with lethal doses of mouse-adapted H1N1 and H3N2, which represent group I and II viruses, respectively. Furthermore, we report amino acid residues I222 and E227, located in close proximity to the active site, are indispensable for inhibition by this antibody. This unique, highly-conserved linear sequence in viral NA could be an attractive immunological target for protection against diverse strains of influenza viruses.

Rapid and accurate determination of the potency of varicella vaccine by quantitative polymerase chain reaction.

The potency of varicella vaccines is currently determined by a plaque assay technique, which usually takes seven days and is laborious and has considerable inter- and intra-assay variability. Here, we report a new potency assay for varicella vaccine based on quantitative polymerase chain reaction in conjunction with a much more efficient virus infection step. Potency results can be obtained within 24h of infection and demonstrates acceptable accuracy and reproducibility when compared with the plaque assay, which relies on manual counting of plaques formed one week after viral infection. Using multiple vaccine lots from 7 manufacturers, we found no significant difference in infectivity determined between the new assay and plaque assay. The optimized conditions for viral infection and polymerase chain reaction are of significant value for the potency determination of the vaccine due to its rapidity, accuracy and the high throughput capacity of the assay.

Bioactivity determination of native and variant forms of therapeutic interferons.

The traditional antiviral assays for the determination of interferon potency are reported to have considerable variability between and within assays. Although several reporter gene assays based on interferon-inducible promoter activities have been reported, data from comprehensive validation studies are lacking and few studies have been conducted to analyze the variant forms of interferons, which could have undesirable clinical implications. Here, a reporter gene assay employing a HEK293 cell line stably transfected with luciferase gene under the control of interferon-stimulated response element promoter was developed and validated. The assay was found to be more sensitive, with a larger detection range than the antiviral assay. Several cytokines tested did not interfere with the test, suggesting the assay possesses a certain degree of selectivity. Moreover, the robustness of the assay was demonstrated by minimal variations in the results generated by different analysts and cell passage number (up to 52 passages). Finally, the method was employed to analyze several interferon variants (interferon-α 2a) and we found that the aggregated form has completely lost its potency; while a modest loss of bioactivity in oxidized interferon was observed (approx. 23%), the deamidated form essentially retained its activity.

Study of aggregation, denaturation and reduction of interferon alpha-2 products by size-exclusion high-performance liquid chromatography with fluorescence detection and biological assays.

Interferon alpha-2 (IFN alpha-2) products have been widely used as antivirals for the treatment of serious diseases such as hepatitis B and C. However, reports of adverse reactions following treatment have prompted investigations into the cause of these undesirable events. In this study size-exclusion HPLC (SE-HPLC) methods coupled with intrinsic fluorescence detection were developed for evaluating the stability and degradation profiles of IFN alpha-2 drug substances and drug products. The method allowed baseline resolution of the active ingredient from the excipients present in the finished products that included large amounts of albumin. Limits of detection (S/N>or=3) for IFN alpha-2a and IFN alpha-2b were 32 ng/mL and 28 ng/mL, respectively and good repeatability of chromatographic profiles (%RSD<2.1) was obtained. High molecular weight (HMW) aggregates with apparent molecular weight of approximately 650 kDa as well as dimers, denatured and reduced variants were successfully identified and separated from native IFN alpha-2 proteins. This chromatographic method, which quantitatively measures physical and chemical changes taking place in solution formulations, was found to be capable of monitoring IFN alpha-2a and IFN alpha-2b stability. Potency assay results revealed up to 87% decrease in biological activity of the physically and chemically altered variants compared to the original IFNs.

The replicative activity of human endogenous retrovirus K102 (HERV-K102) with HIV viremia.

OBJECTIVE: To address the activation and replicative activity of HERV-K102 in vivo associated with HIV viremia. DESIGN AND METHODS: Initially serology was performed on HERV-K102 specific envelope peptides to determine if HERV-K102 may become activated with HIV viremia. Before developing a quantitative PCR (qPCR) assay, we first determined whether plasma associated particles contained DNA or RNA genomes in a pilot study which surprisingly revealed predominantly DNA genomes. A relative, ddCt qPCR ratio method was then devised to detect excess levels of HERV-K102 pol DNA templates over genomic levels which served as a surrogate marker to reliably index the level of particles found in plasma. RESULTS: Both the peptide serology and ddCt qPCR excess ratio methods suggested the activation of HERV-K102 in about 70-80% of HIV viremic cases whereas only 2-3% of normal healthy adults had marginally activated HERV-K102 (P < 0.0001). Moreover, by digestion with dUTPase we were able to confirm that the vast majority of excess DNA template in plasma related to cDNA production rather than representing genomic copies. CONCLUSIONS: Our work uniquely suggests the common activation of HERV-K102 with HIV viremia and may be first to directly demonstrate HERV-K102 cDNA production in vivo. The potential implications of the induction of HERV-K102 activation and replication for the prevention and control of HIV are discussed.

Cytotoxic doses of ketoconazole affect expression of a subset of hepatic genes.

Ketoconazole is a widely prescribed antifungal drug, which has also been investigated as an anticancer therapy in both clinical and pre-clinical settings. However, severe hepatic injuries were reported to be associated with the use of ketoconazole, even in patients routinely monitored for their liver functions. Several questions concerning ketoconazole-induced hepatic injury remain unanswered, including (1) does ketoconazole alter cytochrome P450 expression at the transcriptional level?, (2) what types of gene products responsible for cytotoxicity are induced by ketoconazole?, and (3) what role do the major metabolites of ketoconazole play in this pathophysiologic process? A mouse model was employed to investigate hepatic gene expression following hepatotoxic doses of ketoconazole. Hepatic gene expression was analyzed using a toxicogenomic microarray platform, which is comprised of cDNA probes generated from livers exposed to various hepatoxicants. These hepatoxicants fall into five well-studied toxicological categories: peroxisome proliferators, aryl hydrocarbon receptor agonists, noncoplanar polychlorinated biphenyls, inflammatory agents, and hypoxia-inducing agents. Nine genes encoding enzymes involved in Phase I metabolism and one Phase II enzyme (glutathione S-transferase) were found to be upregulated. Serum amyloid A (SAA1/2) and hepcidin were the only genes that were downregulated among the 2364 genes assessed. In vitro cytotoxicity and transcription analyses revealed that SAA and hepcidin are associated with the general toxicity of ketoconazole, and might be usefully explored as generalized surrogate markers of xenobiotic-induced hepatic injury. Finally, it was shown that the primary metabolite of ketoconazole (de-N-acetyl ketoconazole) is largely responsible for the hepatoxicity and the downregulation of SAA and hepcidin.