Herpes Simplex Virus 1 Infection Does Not Increase Amyloid-ß Pathology in APP/PS1 Mice.

Using APP/PS1 mice that overproduce amyloid-ß (Aß) peptides, we investigated whether intranasal infection with a neurovirulent clinical strain of herpes simplex virus 1 (HSV-1) before Aß deposition could accelerate or increase Alzheimer's disease-like pathology. After HSV-1 infection, APP/PS1 mice presented a similar disease as wild type animals based on body weight changes, clinical symptoms, and survival rates. The number and volume of Aß plaques, the number of microglia, and the percentages of circulating monocyte subsets were similar in APP/PS1 mice infected or not with HSV-1. Thus, intranasal infection with HSV-1 does not alter Aß pathology in this mouse model.

Viral Fitness of Baloxavir-Resistant Recombinant Influenza B/Victoria- and B/Yamagata-like Viruses Harboring the I38T PA Change, In Vitro, Ex Vivo and in Guinea Pigs.

Seasonal influenza A and B viruses may cause severe infections requiring therapeutic interventions. Baloxavir, the latest antiviral drug approved against those infections, targets the endonuclease activity encoded by the polymerase acidic (PA) protein. While appearing effective at cessation of viral shedding, baloxavir demonstrated a low barrier of resistance. Herein, we aimed to assess the impact of PA-I38T substitution, a major marker of baloxavir-resistance, on the fitness of contemporary influenza B viruses. Recombinant wild-type (WT) influenza B/Phuket/2073/13 (B/Yamagata/16/88-like) and B/Washington/02/19 (B/Victoria/2/87-like) viruses and their respective PA-I38T mutants were used to evaluate replication kinetics in vitro, using A549 and Calu3 cells, and ex vivo, using nasal human airway epithelium (HAE) cells. Infectivity was also assessed in guinea pigs. In the B/Washington/02/19 background, there were no major differences between the recombinant WT virus and its I38T mutant when viral replication kinetics were evaluated in human lung cell lines and HAE as well as in nasal washes of experimentally infected guinea pigs. By contrast, the I38T mutation moderately impacted the B/Phuket/2073/13 viral fitness. In conclusion, contemporary influenza B viruses that may acquire baloxavir-resistance through the PA-I38T substitution could retain a significant level of fitness, highlighting the importance of monitoring the emergence of such variant.

In vitro fitness of SARS-CoV-2 variants as assessed by competition experiments followed by ddRT-PCR and whole genome sequencing.

OBJECTIVE: To develop a new method for reliable and rapid determination of the fitness of SARS-CoV-2 variants of concern. METHODS: Competition experiments between two SARS-CoV-2 variants were performed in cells of the upper (nasal human airway epithelium) and lower (Calu-3 cells) respiratory tracts followed by quantification of variant ratios by droplet digital reverse transcription (ddRT)-PCR. RESULTS: In competition experiments, the delta variant outcompeted the alpha variant in both cells of the upper and lower respiratory tracts. A 50/50% mixture of delta and omicron variants indicated a predominance of omicron in the upper respiratory tract whereas delta predominated in the lower respiratory tract. There was no evidence of recombination events between variants in competition as assessed by whole gene sequencing. CONCLUSION: Differential replication kinetics were shown between variants of concern which may explain, at least partly, the emergence and disease severity associated with new SARS-CoV-2 variants.

Evaluation of pre- and post-fusion Human metapneumovirus F proteins as subunit vaccine candidates in mice.

Human metapneumovirus (hMPV) is an important respiratory pathogen especially in young children and elderly subjects. Our objective was to assess the immunogenicity and protection conferred by predominant pre- and post-fusion (F) hMPV-F constructs in Balb/C mice. Immunizations without adjuvant were not immunogenic whereas alum-adjuvanted hMPV-F proteins, regardless of their conformations, generated comparable neutralizing antibody titers with undetectable pulmonary viral titers following viral challenge. In conclusion, we found no apparent advantage for mixtures of predominant pre-fusion F proteins over post-fusion conformations for hMPV vaccination in opposite to recent data obtained with the human respiratory syncytial virus.

Repurposing of Drugs as Novel Influenza Inhibitors From Clinical Gene Expression Infection Signatures.

Influenza virus infections remain a major and recurrent public health burden. The intrinsic ever-evolving nature of this virus, the suboptimal efficacy of current influenza inactivated vaccines, as well as the emergence of resistance against a limited antiviral arsenal, highlight the critical need for novel therapeutic approaches. In this context, the aim of this study was to develop and validate an innovative strategy for drug repurposing as host-targeted inhibitors of influenza viruses and the rapid evaluation of the most promising candidates in Phase II clinical trials. We exploited in vivo global transcriptomic signatures of infection directly obtained from a patient cohort to determine a shortlist of already marketed drugs with newly identified, host-targeted inhibitory properties against influenza virus. The antiviral potential of selected repurposing candidates was further evaluated in vitro, in vivo, and ex vivo. Our strategy allowed the selection of a shortlist of 35 high potential candidates out of a rationalized computational screening of 1,309 FDA-approved bioactive molecules, 31 of which were validated for their significant in vitro antiviral activity. Our in vivo and ex vivo results highlight diltiazem, a calcium channel blocker currently used in the treatment of hypertension, as a promising option for the treatment of influenza infections. Additionally, transcriptomic signature analysis further revealed the so far undescribed capacity of diltiazem to modulate the expression of specific genes related to the host antiviral response and cholesterol metabolism. Finally, combination treatment with diltiazem and virus-targeted oseltamivir neuraminidase inhibitor further increased antiviral efficacy, prompting rapid authorization for the initiation of a Phase II clinical trial. This original, host-targeted, drug repurposing strategy constitutes an effective and highly reactive process for the rapid identification of novel anti-infectious drugs, with potential major implications for the management of antimicrobial resistance and the rapid response to future epidemic or pandemic (re)emerging diseases for which we are still disarmed.

Design and Validation with Influenza A Virus of an Aerosol Transmission Chamber for Ferrets.

Background: The importance of aerosols in the spread of viruses like influenza is still a subject of debate. Indeed, most viruses can also be transmitted through direct contact and droplets. Therefore, the importance of the airborne route in a clinical context is difficult to determine. The aim of this study was to design a chamber system to study the airborne transmission of viruses between ferrets. Methods: A system composed of three chambers connected in series, each one housing one ferret and preventing direct contact, was designed. The chambers were designed to house the ferrets for several days and to study the transmission of viruses from an infected (index) ferret to two naïve ferrets via aerosols and droplets or aerosols only. A particle separator was designed that can be used to modulate the size of the particles traveling between the chambers. The chamber system was validated using standard dust as well as with ferrets infected with influenza A virus. Conclusions: The 50% efficiency cut-off of the separator could be modulated between a 5-µm and an 8-µm aerodynamic diameter. In the described setup, influenza A virus was transmitted through the aerosol route in two out of three experiments, and through aerosols and droplets in all three experiments.

The recruitment of peripheral blood leukocytes to the brain is delayed in susceptible BALB/c compared to resistant C57BL/6 mice during herpes simplex virus encephalitis.

The cerebral immune response induced by herpes simplex virus (HSV) encephalitis (HSE) was evaluated in susceptible BALB/c and resistant C57BL/6 mice. BALB/c and C57BL/6 (named C57BL/6-high) mice were respectively infected intranasally with 1 × 103 and 5 × 105 plaque-forming units (PFUs) of HSV-1. C57BL/6 mice (named C57BL/6-low) infected with a low inoculum (1 × 103 PFUs) of HSV-1 were tested in parallel. Mice were monitored for weight loss, sickness signs, and survival for 21 days. The viral load, infectious titers, cytokine/chemokine levels, and peripheral leukocyte infiltration were determined in brain homogenates on days 0 (non-infected), 4, 6, and 8 post-infection (p.i.) by qPCR, plaque assay, ELISA/Luminex™, and flow cytometry, respectively. Our results showed that the mortality of BALB/c mice (67%) was higher compared to those of C57BL/6-low (0%; P ≤ 0.01) and C57BL/6-high (20%; P ≤ 0.05) animals. This higher mortality was associated with increased infectious titers and cytokine/chemokine levels in the brains of BALB/c compared to C57BL/6 mice. Recruitment of inflammatory monocytes, dendritic cells, natural killer, and natural killer T cells to the brain was higher in C57BL/6-high compared to BALB/c animals on day 4 p.i. Infiltration of inflammatory monocytes and T cells in the brain of BALB/c mice was seen on day 6 p.i. Our data suggest that a rapid, sustained, and coordinated recruitment of peripheral leukocytes to the brain of C57BL/6-high mice results in an effective control of viral replication and inflammation whereas the delayed infiltration of immune cells in the brain of BALB/c mice was associated with an exacerbated inflammatory response during HSE.

Zika-Induced Male Infertility in Mice Is Potentially Reversible and Preventable by Deoxyribonucleic Acid Immunization.

Background: Zika virus (ZIKV) infection has been associated with prolonged viral excretion in human semen and causes testicular atrophy and infertility in 10-week-old immunodeficient mice. Methods: Male IFNAR-/- mice, knockout for type I interferon receptor, were immunized with GLS-5700, a deoxyribonucleic acid-based vaccine, before a subcutaneous ZIKV challenge with 6 × 105 plaque-forming units at 13 weeks of age. On day 28 postinfection, testes and epididymides were collected in some mice for histological and functional analyses, whereas others were mated with naive female wild-type C57BL/6J. Results: Although all mice challenged with ZIKV developed viremia, most of them were asymptomatic, showed no weight loss, and survived infection. On day 28 postinfection, none of the unvaccinated, infected mice (9 of 9) exhibited abnormal spermatozoa counts or motility. However, 33% (3 of 9) and 36% (4 of 11) of mated males from this group were infertile, from 2 independent studies. Contrarily, males from the noninfected and the vaccinated, infected groups were all fertile. On days 75 and 207 postinfection, partial recovery of fertility was observed in 66% (2 of 3) of the previously infertile males. Conclusions: This study reports the effects of ZIKV infection on male fertility in a sublethal, immunodeficient mouse model and the efficacy of GLS-5700 vaccination in preventing male infertility.

Combination Therapy with Oseltamivir and Favipiravir Delays Mortality but Does Not Prevent Oseltamivir Resistance in Immunodeficient Mice Infected with Pandemic A(H1N1) Influenza Virus.

Immunosuppressed individuals can shed influenza virus for prolonged periods of time, leading to the frequent emergence of antiviral resistance. We evaluated the benefits of oseltamivir and favipiravir combination therapy compared to single antiviral agents and monitored the emergence of drug-resistant variants in a pharmacologically immunosuppressed mouse model infected with the A(H1N1) pandemic influenza virus. C57BL/6 mice were immunosuppressed with cyclophosphamide and infected with a lethal dose of pandemic influenza A(H1N1) virus. Forty-eight hours post-infection, mice were treated with oseltamivir (20 mg/kg), favipiravir (20 or 50 mg/kg) or both agents BID for 5 or 10 days. Body weight losses, survival rates, lung viral titers, cytokine levels and emergence of resistant viruses were evaluated. Treatment of immunosuppressed mice with high (50 mg/kg) but not low (20 mg/kg) doses of favipiravir in combination with oseltamivir (20 mg/kg) significantly delayed mortality and reduced lung viral titers compared to treatment with a single drug regimen with oseltamivir but did not prevent the emergence of oseltamivir-resistant H275Y neuraminidase variants. Combination therapy with oseltamivir and favipiravir should be considered for evaluation in clinical trials.

Both IRF3 and especially IRF7 play a key role to orchestrate an effective cerebral inflammatory response in a mouse model of herpes simplex virus encephalitis.

The impact of a deficiency in interferon regulatory factor (IRF)3 and IRF7 was evaluated in an herpes simplex virus encephalitis (HSE) model. Compared to wild type (WT), the mortality rates of infected IRF3-/- and IRF7-/- mice were higher and associated with increased brain viral titers. At a critical time post-infection, IRF7-/- mice exhibited a deficit in IFN-ß production. At a later time point, levels of type I IFNs and cytokines were increased in brains of both deficient mice compared to WT. Our results suggest that IRF3, and especially IRF7, are important for an effective control of inflammatory responses during HSE.

Predominant role of IPS-1 over TRIF adaptor proteins in early innate immune response against Zika virus in mice.

Toll-like receptors and RNA helicases are involved in the control of RNA virus infection through production of type I interferons (IFNs). To delineate the relative contributions of these signalling pathways in the innate immune response and the control of Zika virus (ZIKV) pathogenesis, the impact of a deficiency in TRIF and/or IPS-1 adaptor proteins was investigated in mice. Mice were infected intravenously with ZIKV and monitored for clinical signs for 14 days. Groups of mice were sacrificed on days 1, 3 and 7 post-infection (p.i.) and viral RNA was measured by digital droplet PCR in serum, spleen, brain and eyes. Some mice were sacrificed at 12 h p.i. for determination of the levels of IFN-α/-ß (ELISA), cytokines/chemokines (Luminex) and total/phosphorylated IRF3 and IRF7 (Western blotting). All groups of mice infected with ZIKV exhibited no clinical signs of infection. However, IPS-1-/- and TRIF-/-xIPS-1-/- mice developed higher viraemia than WT and TRIF-/- groups on days 1, 3 and 7. TRIF-/-xIPS-1-/- mice presented higher viral RNA levels in spleen, brain and eyes over time than TRIF-/-, IPS-1-/- and WT groups. At 12 h, IFN-α/-ß and cytokine/chemokine levels in spleen were significantly decreased in IPS-1-/- and TRIF-/-xIPS-1-/- compared to WT and TRIF-/-. On day 1 p.i., IFN-ß levels were significantly reduced in spleen of TRIF-/-xIPS-1-/- mice compared to all other groups. These data suggest that IPS-1 plays a more important role than TRIF in the early type I IFN response and that both IPS-1 and TRIF are involved at later stages of ZIKV infection.

Protease-activated receptor 1 inhibition protects mice against thrombin-dependent respiratory syncytial virus and human metapneumovirus infections.

BACKGROUND AND PURPOSE: Protease-activated receptor 1 (PAR1) has been demonstrated to be involved in the pathogenesis of viral diseases. However, its role remains controversial. The goal of our study was to investigate the contribution of PAR1 to respiratory syncytial virus (RSV) and human metapneumovirus (hMPV) infections. EXPERIMENTAL APPROACH: Pharmacological approaches were used to investigate the role of PAR1 during RSV and hMPV infection, in vitro using epithelial A549 cells and in vivo using a mouse model of virus infection. KEY RESULTS: In vitro, the PAR1 antagonist RWJ-56110 reduced the replication of RSV and hMPV in A549 cells. In agreement with these results, RWJ-56110-treated mice were protected against RSV and hMPV infections, as indicated by less weight loss and mortality. This protective effect in mice correlated with decreased lung viral replication and inflammation. In contrast, hMPV-infected mice treated with the PAR1 agonist TFLLR-NH2 showed increased mortality, as compared to infected mice, which were left untreated. Thrombin generation was shown to occur downstream of PAR1 activation in infected mice via tissue factor exposure as part of the inflammatory response, and thrombin inhibition by argatroban reduced the pathogenicity of the infection with no additive effect to that induced by PAR1 inhibition. CONCLUSION AND IMPLICATIONS: These data show that PAR1 plays a detrimental role during RSV and hMPV infections in mice via, at least, a thrombin-dependent mechanism. Thus, the use of PAR1 antagonists and thrombin inhibitors may have potential as a novel approach for the treatment of RSV and hMPV infections.

The combination of oseltamivir with azithromycin does not show additional benefits over oseltamivir monotherapy in mice infected with influenza A(H1N1)pdm2009 virus.

The combination of azithromycin, an immunomodulator, with oseltamivir was compared to oseltamivir monotherapy in a lethal BALB/c model of influenza A(H1N1)pdm09 infection. Groups of 14-16 mice received oral oseltamivir (10 mg/kg once daily for 5 days, starting at day 2 post-inoculation) alone or combined to azithromycin (a single 100 mg/kg dose, injected intraperitoneally at day 3 post-inoculation). Based on survival rates, lung viral titers, and pro-inflammatory cytokine levels, the combination therapy did not provide obvious additional clinical/virological benefits over oseltamivir monotherapy. Additional studies are still needed to better define the potential role of adjunctive immunomodulatory therapy for severe influenza infections.

In vitro and in vivo evidence of a potential A(H1N1)pdm09 antigenic drift mediated by escape mutations in the haemagglutinin Sa antigenic site.

Influenza A(H1N1)pdm09 virus continues to circulate worldwide without evidence of significant antigenic drift between 2009 and 2016. By using escape mutants, we previously identified six haemagglutinin (HA) changes (T80R, G143E, G158E, N159D, K166E and A198E) that were located within antigenic sites. Combinations of these mutations were introduced into the A(H1N1)pdm09 HA plasmid by mutagenesis. Reassortant 6 : 2 viruses containing both the HA and NA genes of the A(H1N1)pdm09 and the six internal gene segments of A/PR/8/34 were rescued by reverse genetics. In vitro, HA inhibition and microneutralization assays showed that the HA hexa-mutant reassortant virus (RG1) escaped A(H1N1)pdm09 hyper-immune ferret antiserum recognition. C57Black/6 mice that received the vaccine formulated with A/California/07/09 were challenged with 2×104 p.f.u. of either the 6 : 2 wild-type (WT) or RG1 viruses. Reductions in body weight loss, mortality rate and lung viral titre were observed in immunized animals challenged with the 6 : 2 WT virus compared to non-immunized mice. However, immunization did not protect mice challenged with RG1 virus. To further characterize the mutations causing this antigenic change, 11 additional RG viruses whose HA gene contained single or combinations of mutations were evaluated in vitro. Although the RG1 virus was still the least reactive against hyper-immune serum by HAI testing, mutations G158E and N159D within the Sa antigenic site appeared to play the major role in the altered antigenicity of the A(H1N1)pdm09 virus. These results show that the Sa antigenic site contains the most prominent epitopes susceptible to cause an antigenic drift, escaping actual vaccine protection.

The E119D neuraminidase mutation identified in a multidrug-resistant influenza A(H1N1)pdm09 isolate severely alters viral fitness in vitro and in animal models.

We recently isolated an influenza A(H1N1)pdm09 E119D/H275Y neuraminidase (NA) variant from an immunocompromised patient who received oseltamivir and zanamivir therapies. This variant demonstrated cross resistance to zanamivir, oseltamivir, peramivir and laninamivir. In this study, the viral fitness of the recombinant wild-type (WT), E119D and E119D/H275Y A(H1N1)pdm09 viruses was evaluated in vitro and in experimentally-infected C57BL/6 mice and guinea pigs. In replication kinetics experiments, viral titers obtained with the E119D and E119D/H275Y recombinants were up to 2- and 4-log lower compared to the WT virus in MDCK and ST6GalI-MDCK cells, respectively. Enzymatic studies revealed that the E119D mutation significantly decreased the surface NA activity. In experimentally-infected mice, a 50% mortality rate was recorded in the group infected with the WT recombinant virus whereas no mortality was observed in the E119D and E119D/H275Y groups. Mean lung viral titers on day 5 post-inoculation for the WT (1.2 ± 0.57 × 10(8) PFU/ml) were significantly higher than those of the E119D (9.75 ± 0.41 × 10(5) PFU/ml, P < 0.01) and the E119D/H275Y (1.47 ± 0.61 × 10(6) PFU/ml, P < 0.01) groups. In guinea pigs, comparable seroconversion rates and viral titers in nasal washes (NW) were obtained for the WT and mutant index and contact groups. However, the D119E reversion was observed in most NW samples of the E119D and E119D/H275Y animals. In conclusion, the E119D NA mutation that could emerge in A(H1N1)pdm09 viruses during zanamivir therapy has a significant impact on viral fitness and such mutant is unlikely to be highly transmissible.

Valacyclovir combined with artesunate or rapamycin improves the outcome of herpes simplex virus encephalitis in mice compared to antiviral therapy alone.

Despite antiviral therapy, the mortality rate of herpes simplex virus encephalitis (HSE) remains high and many surviving patients harbor neurological sequelae. Although viral replication is responsible for substantial neurological damages, an exaggerated inflammatory response could also contribute to this process. Artesunate (ART) and rapamycin (RAPA) have shown some benefits in the treatment of herpes simplex virus infections. Herein, we evaluated the benefit of combining ART or RAPA with valacyclovir (VACV) in a murine model of HSE. Infected mice were treated with VACV (1mg/mL in drinking water) from day 3 post-infection (p.i.) combined or not with daily intraperitoneal administration of ART (30mg/kg) or RAPA (20mg/kg) from days 4 to 13 p.i. Viral load, infectious titers, cytokine and chemokine levels were measured in brain homogenates on days 5, 7 and 9. The survival rates of mice treated with VACV and ART or RAPA were higher than with VACV alone (71.9% versus 43.2% for ART and 66.7% versus 43.2% for RAPA; both P⩽0.05) but no significant difference was seen in the brain viral loads. Levels of IL-1ß, IL-2 (both P⩽0.05), IL-6, IFN-γ (both P⩽0.01), CCL2 (P⩽0.01), CCL3 and CCL4 (both P⩽0.05) were reduced in mice treated with VACV combined with ART versus VACV alone. Levels of IL-6, IL-1ß and IFN-γ slightly increased on day 7 in mice treated with VACV combined with RAPA compared to VACV alone and then decreased on day 9. Our results suggest that immunomodulatory compounds such as ART or RAPA could benefit antiviral therapy in HSE.

Effect of in vitro syncytium formation on the severity of human metapneumovirus disease in a murine model.

Human metapneumovirus (HMPV) is an important cause of acute respiratory tract infections (ARTI) in children, elderly individuals and immunocompromised patients. In vitro, different HMPV strains can induce variable cytopathic effects ranging from large multinucleated syncytia to focal cell rounding. In this study, we investigated the impact of different in vitro phenotypes of two HMPV strains on viral replication and disease severity in a BALB/c mouse model. We first generated two recombinant GFP-expressing HMPV viruses: C-85473, a syncytium-inducing strain (rC-85473) belonging to the A1 subtype and CAN98-75, a focal cell rounding-inducing strain (rCAN98-75) of the B2 subtype. We subsequently exchanged the F genes of both strains to create the chimeric viruses rC-85473_F and rCAN98-75_F. We demonstrated that the F protein was the sole protein responsible for the syncytium phenotype and that viruses carrying a syncytium-inducing F protein replicated to significantly higher titers in vitro. In vivo, however, the virulence and replicative capacity of the different HMPV strains did not appear to be solely dependent on the F gene but also on the viral background, with the strains containing the C-85473 background inducing more weight loss as well as increased lung viral titers, pro-inflammatory cytokines and inflammation than strains containing the CAN98-75 background. In conclusion, the F protein is the main determinant of syncytium formation and replication kinetics in vitro, although it is not the only factor implicated in HMPV disease severity in mice.

Heterosubtypic protection conferred by the human monoclonal antibody PN-SIA28 against influenza A virus lethal infections in mice.

PN-SIA28 is a human monoclonal antibody (Hu-MAb) targeting highly conserved epitopes within the stem portion of the influenza virus hemagglutinin (HA) (N. Clementi, et al, PLoS One 6:e28001, 2011, http://dx.doi.org/10.1371/journal.pone.0028001). Previous in vitro studies demonstrated PN-SIA28 neutralizing activities against phylogenetically divergent influenza A subtypes. In this study, the protective activity of PN-SIA28 was evaluated in mice inoculated with lethal influenza A/WSN/33 (H1N1), A/Quebec/144147/09 (H1N1)pdm09, and A/Victoria/3/75 (H3N2) viruses. At 24 h postinoculation (p.i.), animals received PN-SIA28 intraperitoneally (1 or 10 mg/kg of body weight) or 10 mg/kg of unrelated Hu-MAb (mock). Body weight loss and mortality rate (MR) were recorded for 14 days postinfection (p.i.). Lung viral titers (LVT) were determined at day 5 p.i. In A/WSN/33 (H1N1)-infected groups, all untreated and mock-receiving mice died, whereas MRs of 87.5% and 25% were observed in mice that received PN-SIA28 1 and 10 mg/kg, respectively. In influenza A(H1N1) pdm09-infected groups, an MR of 75% was recorded for untreated and mock-treated groups, whereas the PN-SIA28 1-mg/kg and 10-mg/kg groups had rates of 62.5% and 0%, respectively. In A/Victoria/3/75 (H3N2)-infected animals, untreated and mock-treated animals had MRs of 37.5% and 25%, respectively, and no mortalities were recorded after PN-SIA28 treatments. Accordingly, PN-SIA28 treatments significantly reduced weight losses and resulted in a ≥ 1-log reduction in LVT compared to the control in all infection groups. This study confirms that antibodies targeting highly conserved epitopes in the influenza HA stem region, like PN-SIA28, not only neutralize influenza A viruses of clinically relevant subtypes in vitro but also, more importantly, protect from a lethal influenza virus challenge in vivo.

Adjuvant effect of the human metapneumovirus (HMPV) matrix protein in HMPV subunit vaccines.

The human metapneumovirus (HMPV) fusion (F) protein is the most immunodominant protein, yet subunit vaccines containing only this protein do not confer complete protection. The HMPV matrix (M) protein induces the maturation of antigen-presenting cells in vitro. The inclusion of the M protein into an F protein subunit vaccine might therefore provide an adjuvant effect. We administered the F protein twice intramuscularly, adjuvanted with alum, the M protein or both, to BALB/c mice at 3 week intervals. Three weeks after the boost, mice were infected with HMPV and monitored for 14 days. At day 5 post-challenge, pulmonary viral titres, histopathology and cytokine levels were analysed. Mice immunized with F+alum and F+M+alum generated significantly more neutralizing antibodies than mice immunized with F only [titres of 47 ± 7 (P<0.01) and 147 ± 13 (P<0.001) versus 17 ± 2]. Unlike F only [1.6 ± 0.5 × 10(3) TCID50 (g lung)(-1)], pulmonary viral titres in mice immunized with F+M and F+M+alum were undetectable. Mice immunized with F+M presented the most important reduction in pulmonary inflammation and the lowest T-helper Th2/Th1 cytokine ratio. In conclusion, addition of the HMPV-M protein to an F protein-based vaccine modulated both humoral and cellular immune responses to subsequent infection, thereby increasing the protection conferred by the vaccine.

Adjuvanted inactivated influenza A(H3N2) vaccines induce stronger immunogenicity in mice and confer higher protection in ferrets than unadjuvanted inactivated vaccines.

Influenza viruses are major respiratory pathogens and the development of improved vaccines to prevent these infections is of high priority. Here, we evaluated split inactivated A(H3N2) vaccines (A/Uruguay/716/2007) combined or not with adjuvants (AS03, AS25 and Protollin) and administered by three different routes, intramuscular (i.m.), intranasal (i.n.) or intradermal (i.d.), both in BALB/c mice and in ferrets. Ferrets were challenged with the homologous strain A/Uruguay/716/2007 (H3N2) or the heterologous strain A/Perth/16/2009 (H3N2) 4 weeks after the second immunization with A/Uruguay/716/2007 vaccines. Temperature, weight loss and clinical signs were monitored on a daily basis and nasal washes were performed to evaluate viral titers in the upper respiratory tract. All adjuvanted vaccines induced stronger humoral immune responses than unadjuvanted ones in both mice and ferrets. In mice, the AS03- and AS25-adjuvanted i.m. vaccines generated a mixed Th1-Th2 response at 6 and 19 weeks after the last immunization as shown by the production of IgG1 and IgG2a antibodies as well as the production of IL-2, IL-4 and IFN-γ by CD4+ and CD8+ T cells. HAI and MN titers were also higher in those groups when compared to the i.n. Protollin-adjuvanted and unadjuvanted groups. The Protollin-adjuvanted i.n. vaccine induced a more Th1 oriented response with a significant production of IgA in bronchoalveolar lavages. In ferrets, the AS03- and AS25-adjuvanted i.m. vaccines also induced higher HAI and MN titers compared to the other groups. These vaccines also significantly decreased viral titers after challenge with both the homologous A/Uruguay/716/2007 (H3N2) and the heterologous A/Perth/16/2009 (H3N2) strains. In conclusion, adjuvanted influenza vaccines elicited stronger humoral response in mice and conferred greater protection in naive ferrets than unadjuvanted ones. Interestingly, the AS25 adjuvant system containing monophosphoryl-lipid-A appears particularly promising for developing more potent inactivated influenza vaccines.