Exploring Novel Vitamin K Derivatives with Anti-SARS-CoV-2 Activity.

From our compound library of vitamin K derivatives, we found that some compounds exhibited anti-SARS-CoV-2 activity in VeroE6/TMPRSS2 cells. The common structure of these compounds was menaquinone-2 (MK-2) with either the m-methylphenyl or the 1-naphthyl group introduced at the end of the side chain. Therefore, new vitamin K derivatives having more potent anti-SARS-CoV-2 activity were explored by introducing various functional groups at the ω-position of the side chain. MK-2 derivatives with a purine moiety showed the most potent antiviral activity among the derivatives. We also found that their mechanism of action was the inhibition of RNA-dependent RNA polymerase (RdRp) of SARS-CoV-2. The chemical structures of our compounds were completely different from those of nucleic acid derivatives such as remdesivir and molnupiravir, clinically approved RdRp inhibitors for COVID-19 treatment, suggesting that our compounds may be effective against viruses resistant to these nucleic acid derivatives.

Amodiaquine derivatives as inhibitors of severe fever with thrombocytopenia syndrome virus (SFTSV) replication.

Severe fever with thrombocytopenia syndrome (SFTS) is an emerging tick-borne viral infection caused by a bandavirus in the family of Phenuiviridae, commonly known as SFTS virus (SFTSV). We have previously isolated SFTSV from blood samples of SFTS patients and established an antiviral assay system to identify selective inhibitors of SFTSV in vitro. Using the assay system, the antimalarial agent amodiaquine was identified as a selective inhibitor of SFTSV replication. However, due to its insufficient antiviral activity, 98 amodiaquine derivatives were newly synthesized and examined for their anti-SFTSV activity. Among the derivatives, some compounds showed selective inhibitory effect on SFTSV replication in vitro. The 50% effective concentration (EC50) and cytotoxic concentration (CC50) of the most active compound (C-90) were 2.6 ± 0.6 and >50 µM, respectively. This EC50 value was comparable to or slightly better than that of favipiravir (4.1 ± 0.6 µM). On the other hand, pharmacokinetic studies in vivo revealed that C-90 was poor in its oral bioavailability in mice. Therefore, we further designed and synthesized derivatives and obtained 2 compounds with selective anti-SFTSV activity in vitro and improved pharmacokinetics in vivo.

Novel RT-PCR Using Sugar Chain-Immobilized Gold-Nanoparticles Correlates Patients' Symptoms: The Follow-Up Study of COVID-19 Hospitalized Patients.

Background: The transmissible capacity and toxicity of SARS-CoV-2 variants are continually changing. We report here the follow-up study of hospitalized COVID-19 patients from 2020 to 2022. It is known that the PCR diagnosis for hospitalized patients sometimes causes confusion because of the incompatibility between their diagnosis and symptoms. We applied our sugar chain-immobilized gold-nanoparticles for the extraction and partial purification of RNA from specimens for quantitative RT-PCR assay and evaluated whether the results correlate with patients' symptoms. Methods and Results: Saliva specimens were taken from hospitalized patients with mild or moderate symptoms every early morning. At the time of RT-PCR diagnosis, two methods for the extraction and partial purification of RNA from the specimen were performed: a commonly used Boom (Qiagen) method and our original sugar chain-immobilized gold nanoparticle (SGNP) method. For symptoms, body temperature and oxygen saturation (SpO2) of patients were monitored every 4 h. Conclusions: It was clear that patients infected with the Delta variant needed more time to recover than those with the Omicron variant, and that the SGNP method showed more realistic correlation with the symptoms of patients compared with the common Qiagen method.

Novel Neplanocin A Derivatives as Selective Inhibitors of Hepatitis B Virus with a Unique Mechanism of Action.

Novel neplanocin A derivatives have been identified as potent and selective inhibitors of hepatitis B virus (HBV) replication in vitro. These include (1S,2R,5R)-5-(5-bromo-4-methyl-7H-pyrrolo[2,3-d]-pyrimidin-7-yl)-3-(hydroxymethyl)cyclopent-3-ene-1,2-diol (AR-II-04-26) and (1S,2R,5R)-5-(4-amino-3-iodo-1H-pyrazolo[3,4-d]pyrimidin-1-yl)-3-(hydroxylmethyl)cyclopent-3-ene-1,2-diol (MK-III-02-03). The 50% effective concentrations of AR-II-04-26 and MK-III-02-03 were 0.77 ± 0.23 and 0.83 ± 0.36 µM in HepG2.2.15.7 cells, respectively. These compounds reduced intracellular HBV RNA levels in HepG2.2.15.7 cells and infected primary human hepatocytes. Accordingly, they could reduce HBs and HBe antigen production in the culture supernatants, which was not observed with clinically approved anti-HBV nucleosides and nucleotides (reverse transcriptase inhibitors). The neplanocin A derivatives also inhibited HBV RNA derived from cccDNA. In addition, unlike neplanocin A itself, the compounds did not inhibit S-adenosyl-l-homocysteine hydrolase activity. Thus, it appears that the mechanism of action of AR-II-04-26 and MK-III-02-03 differs from that of the clinically approved anti-HBV agents. Although their exact mechanism (target molecule) remains to be elucidated, the novel neplanocin A derivatives are considered promising candidate drugs for inhibition of HBV replication.

Mechanism on antigen delivery under mucosal vaccination using cell-penetrating peptides immobilized at multiple points on polymeric platforms.

We have developed an aggregate of D-octaarginine immobilized at multiple points on a co-polymer of N-vinylacetamide and acrylic acid. Previous studies revealed that immunoglobulin G and A were induced when mice were inoculated with influenza virus antigens under coadministration with the D-octaarginine-immobilized polymers as a mucosal vaccine adjuvant. Infection experiments demonstrated that mice vaccinated with a mixture of inactivated influenza viruses and the polymers were protected from infection with mouse-adapted infectious viruses. In the present study, we investigated the mechanism on antigen delivery under mucosal vaccination using the polymers. Two-hour retention of fluorescein-labeled ovalbumin (F-OVA) on the nasal mucosa was observed when applied with the polymers; nevertheless F-OVA was eliminated less than 10 min under polymer-free conditions. F-OVA mixed with the polymers was vigorously taken up into murine dendritic cells. Electrophoresis and dynamic light scattering analysis indicated that OVA interacted with the polymers. The uptake of F-OVA was hardly ever inhibited by the addition of an excess amount of intact OVA. The results suggested that viral antigens were accumulated on the mucosa and delivered into dendritic cells under basolateral membranes via dendrites extending to the mucosal surface and/or subsequent to their permeation through epithelial cells, when they were coadministered with D-octaarginine-immobilized polymers.

The chemokine receptor antagonist cenicriviroc inhibits the replication of SARS-CoV-2 in vitro.

Cenicriviroc (CVC) is a small-molecule chemokine receptor antagonist with highly potent and selective anti-human immunodeficiency virus type 1 (HIV-1) activity through antagonizing C-C chemokine receptor type 5 (CCR5) as a coreceptor of HIV-1. CVC also strongly antagonizes C-C chemokine receptor type 2b (CCR2b), thereby it has potent anti-inflammatory and immunomodulatory effects. CVC is currently under clinical trials in the patients for treatment of nonalcoholic steatohepatitis, in which immune cell activation and dysregulation of proinflammatory cytokines play an important role in its pathogenesis. In this study, CVC was examined for its inhibitory effect on the replication of SARS-CoV-2, the causative agent of COVID-19, in cell cultures and found to be a selective inhibitor of the virus. The 50% effective concentrations of CVC were 19.0 and 2.9 µM in the assays based on the inhibition of virus-induced cell destruction and viral RNA levels in culture supernatants of the infected cells, respectively. Interestingly, the CCR5-specific antagonist maraviroc did not show any anti-SARS-CoV-2 activity. Although the mechanism of SARS-CoV-2 inhibition by CVC remains to be elucidated, CCR2b does not seem to be its target molecule. Considering the fact that the regulation of excessive immune activation is required to treat COVID-19 patients at the late stage of the disease, CVC should be further pursued for its potential in the treatment of SARS-CoV-2 infection.

Induction of E. coli-derived endonuclease MazF suppresses HIV-1 production and causes apoptosis in latently infected cells.

The current antiretroviral therapy cannot cure the patients infected with human immunodeficiency virus type 1 (HIV-1) due to the existence of latently infected cells capable of virus production from harboring proviral DNA. MazF is an ACA nucleotide sequence-specific endoribonuclease derived from Escherichia coli. The conditional expression of MazF by binding of HIV-1 Tat to the promoter region of a MazF-expression vector has previously been shown to selectively inhibit HIV-1 replication in acutely infected cells. The expression of MazF significantly suppressed tumor necrosis factor (TNF)-α-induced HIV-1 production and viral RNA expression in the HIV-1 latently infected cell line OM-10.1 transduced with the MazF-expression vector (OM-10.1/MFR). Moreover, the viability of OM-10.1/MFR cells decreased with increasing concentrations of TNF-α, whereas such decrease was not observed for HL-60 cells transduced with the MazF-expression vector (HL-60/MFR), the uninfected parental cell line of OM-10.1. TNF-α increased the expression of cleaved caspase-3 and cleaved poly (ADP-ribose) polymerase in OM-10.1/MFR cells, indicating that the cell death was caused by the induction of apoptosis. TNF-α-induced expression of MazF mRNA was detected in OM-10.1/MFR but not HL-60/MFR cells, suggesting that TNF-α-induced apoptosis of latently infected cells was due to the expression of MazF. Thus, the anti-HIV-1 gene therapy using the MazF-expression vector may have potential for the cure of HIV-1 infection in combination with suitable latency reversing agents through reducing the size of latently infected cells without viral reactivation.

Novel Anti-CD70 Antibody Drug Conjugate for the Treatment of Adult T-Cell Leukemia (ATL).

BACKGROUND/AIM: Adult T-cell leukemia (ATL) is a hematological malignancy caused by infection with human T-cell leukemia virus type 1 (HTLV-1). Chemotherapy, antibody therapy, and bone marrow transplantation are used to treat this disease, however, median survival time has not been significantly improved. Our aim was to develop and evaluate a novel antibody-drug conjugate (ADC) with regards to cell cytotoxicity and target specificity. MATERIALS AND METHODS: In this study, we have constructed a novel ADC, which is composed of an anti-CD70 single chain Fv-Fc antibody conjugated with the anticancer agent emtansine using a novel antibody modification method. Cell cytotoxicity and target specificity were assessed using a cell proliferation assay. RESULTS: The anti-CD70 ADC selectively killed HTLV-1-infected cells and ATL cells without affecting other cells. CONCLUSION: The anti-CD70 ADC offers some chemotherapeutic potential for the treatment of ATL.

Synthesis and anti-HBV activity of carbocyclic nucleoside hybrids with salient features of entecavir and aristeromycin.

Modified carbocyclic nucleosides (4a-g) constituting 7-deazapurine, 4'-methyl, exocyclic double bond and 2',3'-hydroxy were synthesized. NOE and X-ray studies of 4c confirmed the α-configuration of 4'-methyl. The anti-HBV assay demonstrated 4e (IC50 = 3.4 µM) without notable cytotoxicity (CC50 = 87.5 µM) as a promising lead for future exploration.

Successful treatment of an AIDS patient with prolonged Mycobacterium avium bacteremia, high HIV RNA, HBV infection, Kaposi's sarcoma and cytomegalovirus retinitis.

We report an AIDS patient with a high HIV RNA copy number in the plasma who was successfully treated for prolonged Mycobacterium avium bacteremia and other complications. An HIV-infected patient with high fever, anemia, high alkaline phosphatase, cystic lung lesions, hepatitis B virus infection and Kaposi's sarcoma was referred to our hospital. PCR of the blood revealed Mycobacterium avium bacteremia and the time to blood culture positivity was 8 days. The HIV-1 RNA copy number in the plasma was more than ten million copies/ml and the CD4-positive T cell count was 21 cells/µL. Although the high fever resolved five days after therapy for Mycobacterium avium was started, the fever recurred just before starting anti-retroviral therapy (ART) including dolutegravir. The patient experienced repeated but self-limiting bouts of severe inflammation. Mycobacteremia was intermittently detected up to 79 days, suggesting that the recurrent episodes of inflammation were due to the intermittent dissemination of mycobacteria, and that persistent treatment is needed. Five months after the beginning of ART, the HIV-1 RNA copy number in the plasma was still 28,000 copies/ml. An HIV drug-resistance test revealed sensitivity to all anti-retroviral drugs. Eleven months after the initiation of ART, the HIV RNA copy number in the plasma decreased to 45 copies/mL and the CD4-positive T cell count recovered to 205 cells/µL. Our case also suggests that dolutegravir can be effective in cases with prolonged high levels of HIV RNA. Our findings emphasize that prompt diagnosis and persistent therapy for mycobacterial infection are important for successful treatment.

Cross-Protective Abilities of Hyaluronic Acid Modified with Tetraglycine-l-octaarginine as a Mucosal Adjuvant against Infection with Heterologous Influenza Viruses.

Mucosal vaccination, which secretion of immunoglobulin A (IgA) on the mucosa is accompanied by induction of immunoglobulin G (IgG) in the blood, is one of the most effective ways to circumvent influenza epidemics caused by incorrect prediction of epidemic viral strains or viral mutation. Secreted IgA is expected to prevent hosts from being infected with heterologous viruses because this antibody cross-reacts to strains other than those used for immunization. Our previous mouse experiments revealed that intranasal IgA with cross-reactivity was induced through nasal inoculation with inactivated whole viral particles of the H1N1 A/New Caledonia/20/99 IVR116 (NCL) strain in the presence of hyaluronic acid modified with tetraglycine-l-octaarginine. In the present study, heterologous influenza virus challenge was performed to validate a potential of the hyaluronic acid derivative as a mucosal adjuvant with cross-protective abilities. Serious weight loss was observed when mice were nasally inoculated with inactivated NCL viruses alone and subsequently exposed to mouse-adapted infectious viruses of the H1N1 A/Puerto Rico/8/34 (PR8) strain. The symptom associated with virus infection was hardly ever observed for mice inoculated with a mixture of the viral antigens and tetraglycine-l-octaarginine-linked hyaluronic acid, presumably due to high induction of IgG and IgA capable of cross-reacting to PR8 viruses. Less proliferation of PR8 viruses in those mice was also supported by an insignificant elevation of antibody levels through virus exposure. Our polysaccharide derivative enabled hosts to acquire adaptive immunity with cross-protective abilities against heterologous virus infection.

Pyrimidotriazine derivatives as selective inhibitors of HBV capsid assembly.

Chronic hepatitis B virus (HBV) infection is currently treated with nucleoside/nucleotides analogs. They are potent inhibitors of HBV DNA polymerase, which also functions as reverse transcriptase. Although nucleoside/nucleotide analogs efficiently suppress HBV replication in liver cells, they cannot eradicate HBV DNA from liver cells and cure the disease. Therefore, it is still mandatory to identify and develop effective inhibitors that target a step other than reverse transcription in the viral replication cycle. HBV capsid assembly is a critical step for viral replication and an attractive target for inhibition of HBV replication. We conducted in silico screening of compounds expected to bind to the HBV capsid dimer-dimer interaction site. The selected compounds were further examined for their anti-HBV activity in vitro. Among the test compounds, novel pyrimidotriazine derivatives were found to be selective inhibitors of HBV replication in HepG2.2.15.7 cells. Among the compounds, 2-[(2,3-dichlorophenyl)amino]-4-(4-tert-butylphenyl)-8-methyl-4H,9H-pyrimido[1,2-a][1,3,5]triazin-6-one was the most active against HBV replication. Studies on its mechanism of action revealed that the compound interfered with HBV capsid assembly determined by a cell-free capsid assembly system. Thus, the pyrimidotriazine derivatives are considered to be potential leads for novel HBV capsid assembly inhibitors.

Biodegradable Hyaluronic Acid Modified with Tetraglycine-l-octaarginine as a Safe Adjuvant for Mucosal Vaccination.

We have been investigating the potential use of polymers modified with cell-penetrating peptides as an adjuvant for mucosal vaccination and have already developed nondegradable poly( N-vinylacetamide- co-acrylic acid) (PNVA- co-AA) with which d-octaarginine, a typical cell-penetrating peptide, was grafted. Our previous murine infection experiments demonstrated that immunoglobulin G (IgG) and immunoglobulin A (IgA) were induced in systemic circulation and secreted on nasal mucosa, respectively, through 4-time nasal inoculations with a mixture of influenza viral antigens and d-octaarginine-linked PNVA- co-AA at 7-day intervals, and that immunized mice were perfectly protected from homologous virus infection. In the present study, we designed novel biodegradable polymers bearing cell-penetrating peptides from a perspective of clinical application. Hyaluronic acid whose glucuronic acid was modified with tetraglycine-l-octaarginine at a monosaccharide unit ratio of 30% was successfully developed. The hyaluronic acid derivative exhibited adjuvant activities identical to PNVA- co-AA bearing either d-octaarginine or tetraglycine-d-octaarginine under the above-mentioned inoculation schedule. We further found that there was no difference in humoral immunity between the 4-time inoculations at 7-day intervals and the 2-time inoculations at 28-day intervals. Intranasal IgA induced through the latter schedule with a smaller number of inoculations, which is clinically practical, exhibited cross-reactivity beyond the subtype of viral strains. In vitro toxicity studies demonstrated that the hyaluronic acid derivative was much less toxic than the corresponding PNVA- co-AA derivatives, and that both the polymers and their metabolites did not exhibit genotoxicity. Our results suggested that tetraglycine-l-octaarginine-linked hyaluronic acid would be a clinically valuable and safe adjuvant for mucosal vaccination.

Galectin-3 is involved in HIV-1 expression through NF-κB activation and associated with Tat in latently infected cells.

Galectin-3 (Gal-3) is involved in many biological processes and pathogenesis of diseases in part through nuclear factor (NF)-κB activation. We demonstrated that Gal-3 expression was significantly induced by tumor necrosis factor (TNF)-α or phorbol 12-myristate 13-acetate in OM-10.1 and ACH-2 cells, which are considered as a model of HIV-1 latently infected cells. The expression of Gal-3 was also associated with their viral production. However, the induction of Gal-3 by TNF-α was not observed in their uninfected parental cells. Knockdown of Gal-3 resulted in the suppression of NF-κB activation and HIV-1 replication in the latently infected cells. The expression level of Gal-3 was highly correlated with that of HIV-1 Tat in the latently infected cells stimulated with TNF-α. Furthermore, colocalization and possible interaction of Gal-3 and Tat were observed in the stimulated cells. These results suggent that Gal-3 expression is closely correlated with HIV-1 expression in latently infected cells through NF-κB activation and the interaction with Tat.

Novel amodiaquine derivatives potently inhibit Ebola virus infection.

Ebola virus disease is a severe disease caused by highly pathogenic Ebolaviruses. Although it shows a high mortality rate in humans, currently there is no licensed therapeutic. During the recent epidemic in West Africa, it was demonstrated that administration of antimalarial medication containing amodiaquine significantly lowered mortality rate of patients infected with the virus. Here, in order to improve its antiviral activity, a series of amodiaquine derivatives were synthesized and tested for Ebola virus infection. We found that multiple compounds were more potent than amodiaquine. The structure-activity relationship analysis revealed that the two independent parts, which are the alkyl chains extending from the aminomethyl group and a halogen bonded to the quinoline ring, were keys for enhancing antiviral potency without increasing toxicity. When these modifications were combined, the antiviral efficacy could be further improved with the selectivity indexes being over 10-times higher than amodiaquine. Mechanistic evaluation demonstrated that the potent derivatives blocked host cell entry of Ebola virus, like the parental amodiaquine. Taken together, our work identified novel potent amodiaquine derivatives, which will aid in further development of effective antiviral therapeutics.

Effects of the Chemical Structures of Oligoarginines Conjugated to Biocompatible Polymers as a Mucosal Adjuvant on Antibody Induction in Nasal Cavities.

We have been investigating the potential of oligoarginine-linked polymers as an adjuvant for mucosal vaccination that induces immunoglobulin G (IgG) in systemic circulation and immunoglobulin A (IgA) secreted on the mucosa. Our latest infection experiments demonstrated that mice immunized nasally with a mixture of inactivated influenza viruses and poly(N-vinylacetamide-co-acrylic acid) (PNVA-co-AA) modified with D-octaarginine were perfectly protected from homologous virus infection. On the contrary, virus infection was observed in mice immunized with the antigen alone. This difference was presumably due to insignificant induction of secreted IgA on the nasal mucosa in the latter mice. Since it was unclear whether the current induction level was sufficient for heterologous virus infection, we evaluated the effects of the chemical structures of oligoarginines conjugated to PNVA-co-AA on induction of intranasal IgA. The number and optical activity of the arginine residues and the degree of modification with oligoarginines in the polymer backbone were listed as a factor that would influence IgA induction. Mouse experiments revealed that maximization of the modification resulted in an increase in adjuvant activities of oligoarginine-linked polymers most effectively. Glycine segments inserted between oligoarginines and the polymer backbone were a prerequisite for the maximization. The highest IgA level was observed when antigens were coadministered with diglycine-D-octaarginine-linked PNVA-co-AA.

Development of sugar chain-binding single-chain variable fragment antibody to adult T-cell leukemia cells using glyco-nanotechnology and phage display method.

Adult T-cell leukemia (ATL) is an intractable blood cancer caused by the infection of human T-cell leukemia virus type-1, and effective medical treatment is required. It is known that the structure and expression levels of cell surface sugar chains vary depending on cell states such as inflammation and cancer. Thus, it is expected that the antibody specific for ATL cell surface sugar chain would be an effective diagnostic tool and a strong candidate for the development of an anti-ATL drug. Here, we developed a stable sugar chain-binding single-chain variable fragment antibody (scFv) that can bind to ATL cells using a fibre-type Sugar Chip and phage display method. The fiber-type Sugar Chips were prepared using O-glycans released from ATL cell lines. The scFv-displaying phages derived from human B cells (diversity: 1.04 × 108) were then screened using the fiber-type Sugar Chips, and an O-glycan-binding scFv was obtained. The flow cytometry analysis revealed that the scFv predominantly bound to ATL cell lines. The sugar chain-binding properties of the scFv was evaluated by array-type Sugar Chip immobilized with a library of synthetic glycosaminoglycan disaccharide structures. Highly sulphated disaccharide structures were found to have high affinity to scFv.

Synthesis, Anti-HBV, and Anti-HIV Activities of 3'-Halogenated Bis(hydroxymethyl)-cyclopentenyladenines.

Synthesis of 3'-halogeno analogues (5a-d) of 9-[c-4,t-5-bis(hydroxymethyl)-cyclopent-2-en-r-1-yl]-9H-adenine (BCA, 3) was accomplished by means of dual utilization of the vinyl sulfone functional moieties in both 10 and 16 utilizing a SN2' conjugate-addition reaction and a sulfur-extrusive stannylation, respectively. Evaluation of the antiviral activities of 5a-d revealed that introduction of a halogeno-substituent into the 3'-position of (-)-BCA diminished its anti-HIV-1 activity but increased the inhibitory activity for the reverse transcriptase of HBV in that the 3'-fluorinated BCA 5d exhibited the highest activity without significant cytotoxicity.

Establishment of an antiviral assay system and identification of severe fever with thrombocytopenia syndrome virus inhibitors.

Aims Severe fever with thrombocytopenia syndrome (SFTS) is an emerging tick-borne infectious disease. SFTS is epidemic in Asia, and its fatality rate is around 30% in Japan. The causative virus severe fever with thrombocytopenia syndrome virus (SFTSV) is a phlebovirus of the family Phenuiviridae (the order Bunyavirales). Although effective treatments are required, there are no antiviral agents currently approved for clinical use. Ribavirin and favipiravir were examined for their anti-SFTSV activity and found to be selective inhibitors of SFTSV replication in vitro. However, their activity was not sufficient. Therefore, it is mandatory to identify novel compounds active against SFTSV. To this end, we have established a safe and rapid assay system for screening selective inhibitors of SFTSV. Methods The virus was isolated from SFTS patients treated in Kagoshima University Hospital. Vero cells were infected with SFTSV and incubated in the presence of various concentrations of test compounds. After three days, the cells were examined for their intracellular viral RNA levels by real-time reverse transcription-PCR without extracting viral RNA. The cytotoxicity of test compounds was determined by a tetrazolium dye method. Results Among the test compounds, the antimalarial agent amodiaquine was identified as a selective inhibitor of SFTSV replication. Its 50% effective concentration (EC50) and cytotoxic concentration (CC50) were 19.1 ± 5.1 and >100 µM, respectively. The EC50 value of amodiaquine was comparable to those of ribavirin and favipiravir. Conclusion Amodiaquine is considered to be a promising lead of novel anti-SFTSV agents, and evaluating the anti-SFTSV activity of its derivatives is in progress.

Demonstration of d-Octaarginine-Linked Polymers as Promising Adjuvants for Mucosal Vaccination through Influenza Virus Challenge.

Mucosal vaccination is one of the most effective ways to reduce the risk of pandemics as a result of incorrect prediction of epidemic strains of influenza viruses or virus mutation. However, adjuvants and antigen carriers with potent immunostimulatory activities are a prerequisite for significant induction of mucosal immunity because most antigens are poorly immunogenic when solely applied to the mucosa. Our previous studies demonstrated that poly(N-vinylacetamide-co-acrylic acid) bearing d-octaarginine induced the secretion of antigen-specific immunoglobulin A (IgA) on the mucosa when nasally administered with virus antigens and that intranasal IgA reacts to viral strains other than the one used for immunization. Therefore, the present study evaluated capabilities of secreted IgA for protection against virus infection. When mice were inoculated with a mixture of inactivated H1N1 A/Puerto Rico/8/34 influenza viruses and d-octaarginine-linked polymers, antigen-specific secreted IgA was induced on the nasal mucosa. Immunized mice were completely protected from virus infection of the inoculated strain. To the contrary, mice nasally inoculated with inactivated viruses alone were infected with the homologous viruses presumably because of insignificant induction of secreted IgA. Results demonstrated that our polymer would be a promising adjuvant for mucosal vaccination.