Comparison of influenza virus yields and apoptosis-induction in an adherent and a suspension MDCK cell line

Cell culture-based manufacturing of influenza vaccines is ideally based on easily scalable platforms using suspension cells that grow in chemically defined media. Consequently, different adherent cell lines selected for high virus yields were adapted to grow in suspension culture. This includes the MDCK suspension cell line MDCK.SUS2, which was shown to be a suitable substrate for influenza virus propagation in previous studies. In this study, we investigated options for further improvement of influenza A/PR/8 (H1N1) virus titres and cell-specific virus yields. Best results were achieved by performing a 1:2 dilution with fresh medium at time of infection. In shake flask cultivations, even for multiplicities of infection as low as 10⁻⁵, all cells were infected at 36 h post infection as determined by flow cytometry. In addition, these cells showed a better viability than cells infected without previous washing steps, which was reflected by a reduced level of apoptotic cells, and virus yields exceeding 3 log₁₀ HAU/100 μL. Comparison of bioreactor infections of MDCK.SUS2 cells to the parental adherent MDCK cells showed similar HA titres of 2.94 and 3.15 log₁₀ HAU/100 μL and TCID₅₀ of 1 × 10⁹ and 2.37 × 10⁹ infectious virions/mL. Surprisingly, virus-induced apoptosis differed between the two cell lines, with the MDCK.SUS2 cells showing a much stronger apoptosis induction than the adherent MDCK cells. Obviously, despite their resistance to anoikis, the suspension cells were more susceptible to virus-induced apoptosis. Whether this is related to the adaptation process itself and/or to changes in cell survival pathways influenced by adhesion molecules or influenza virus proteins needs to be clarified in additional studies.     

Safety and immunogenicity of three tetravalent dengue vaccine formulations in healthy adults in the USA

Background

A candidate recombinant, live-attenuated, CYD tetravalent dengue vaccine (CYD-TDV) has recently demonstrated immunogenicity, efficacy and good tolerability. This study was performed to evaluate three CYD-TDV formulations in adults.

Methods

This was a randomized, double-blind, multicenter, phase II trial. The vaccine formulations were: CYD-TDV 5555 (≈5 log₁₀ tissue culture infectious dose 50% [TCID₅₀] of serotypes 1–4); CYD-TDV 5553 (≈5 log₁₀ TCID₅₀ of serotypes 1–3 and ≈3 log₁₀ TCID₅₀ of serotype 4); and CYD-TDV 4444 (≈4 log₁₀ TCID₅₀ of serotypes 1–4). Vaccinations were administered at 0, 6 and 12 months. Immunogenicity was assessed using the plaque reduction neutralization test.

Results

In total, 260 individuals were enrolled. The 5555 formulation elicited a superior serotype 4 response versus the 5553 formulation, with seropositivity rates of 89.7% and 58.3%, respectively, after the second dose (between-group difference 31.4%; 95% confidence interval 18.2–43.2). After each of the three doses, seropositivity rates for serotypes 1–3 were numerically highest with CYD-TDV 5553 and lowest with the 4444 formulation; seropositivity rates for serotype 4 were similar with the 5555 and 4444 formulations, and much lower among recipients of CYD-TDV 5553. Geometric mean titers followed the same pattern as that seen with seropositivity rates. Safety/reactogenicity results were similar for all three vaccine formulations, although the percentage of participants reporting solicited injection site reactions was lower with CYD-TDV 4444 than with the other two formulations. All serious adverse events were unrelated to vaccination.

Conclusions

Reducing the dose of serotype 4 antigen (5553 formulation) creates an imbalance in the immune response to CYD-TDV. Immune responses to CYD-TDV 5555 were slightly higher than to the 4444 formulation. Development of CYD-TDV 5555 has subsequently been pursued.     

Decreased immune response to pneumococcal conjugate vaccine after 23-valent pneumococcal polysaccharide vaccine in children

Background

Pneumococcal polysaccharide vaccine (PPV) is used in children at high risk of IPD. PPV is generally not considered to induce immunologic memory, whereas pneumococcal conjugate vaccines (PCVs) elicit protective antibody responses in infants and induce immunologic memory. Little is known about the characteristics of immune responses to PCV in children who previously received PCV and PPV in series.

Objective

To characterize immune responses to 13-valent pneumococcal CRM₁₉₇ conjugate vaccine (PCV13; serotypes 1, 3, 4, 5, 6A, 6B, 7F, 9V, 14, 18C, 19A, 19F, and 23F) in children vaccinated in infancy with 9-valent pneumococcal–meningococcal C-CRM₁₉₇ conjugate combination vaccine (PCV9-MnCC), followed by a toddler dose of PCV9-MnCC or 23-valent pneumococcal polysaccharide vaccine (PPV23).

Methods

Children (n = 89) who received PCV9-MnCC in infancy and PPV23 or PCV9-MnCC at age 12 months in a previous (2002–2003) study were vaccinated at age 7.5 years with PCV13; groups PPV23/PCV13 (n = 50) and PCV9/PCV13 (n = 39). Immunoglobulin (Ig)G antibodies, avidity, and opsonophagocytic activity (OPA) were measured before and at 1 and 4 weeks postvaccination.

Results

One week postvaccination, IgG levels increased significantly for all serotypes in both groups, and >97% of vaccinees achieved IgG ≥0.35 μg/ml 4 weeks after PCV13 vaccination. The PCV9/PCV13 group had higher IgG responses compared with the PPV23/PCV13 group. The upper limits of the 95% confidence intervals of the PPV23/PCV13:PCV9/PCV13 IgG geometric mean concentration ratios were <1.0 for serotypes 1, 4, 5, 9V, 18C, and 23F at 1 week. OPA and avidity results supported these findings.

Conclusions

PPV23 vaccination of toddlers may compromise subsequent responses to pneumococcal conjugate vaccines. The clinical relevance of this finding is unclear.     

Novel chimeric porcine circovirus (PCV) with the capsid gene of the emerging PCV2b subtype cloned in the genomic backbone of the non-pathogenic PCV1 is attenuated in vivo and induces protective and cross-protective immunity against PCV2b and PCV2a subtypes in pigs

Porcine circovirus type-2b (PCV2b) is the primary global causative agent of porcine circovirus-associated disease (PCVAD). In this study, we first constructed a novel chimeric virus (PCV1-2b) with the PCV2b capsid gene cloned into the backbone of non-pathogenic PCV1. A pathogenicity study conducted in caesarean-derived colostrum-deprived pigs showed that pigs inoculated with PCV1-2b (n = 10) had decreased lymphoid lesions and significantly lower viral load at 21 dpi, and significantly lower viremia starting at 14 dpi compared to pigs inoculated with PCV2b (n = 10). All PCV1-2b infected pigs remained clinically healthy, while four of ten PCV2b-infected pigs died or were euthanized early due to clinical PCVAD. In a subsequent challenge study, conventional pigs were first vaccinated with PCV1-2b (n = 20) or left unvaccinated (n = 20), and 10 pigs in each group were then challenged with PCV2a and PCV2b, respectively. Vaccinated pigs had no detectable viremia and significantly decreased overall lymphoid lesion scores and lower viral loads compared to unvaccinated controls. The results indicate the chimeric PCV1-2b virus is a good candidate for a live-attenuated vaccine against both PCV2b and PCV2a subtypes.     

One dose of a porcine circovirus 2 (PCV2) sub-unit vaccine administered to 3-week-old conventional piglets elicits cell-mediated immunity and significantly reduces PCV2 viremia in an experimental model

The immunogenicity and efficacy generated by one dose of a PCV2 sub-unit vaccine (Porcilis PCV^®) were evaluated in 3-week-old conventional piglets. Vaccination induced both humoral and cell-mediated responses against PCV2, which were increased after the challenge with a PCV2 genotype “b” isolate. High levels of maternally derived antibodies (IPMA ≥ 10 log₂) at the time of vaccination were found to interfere with the active seroconversion, whereas titres below 8 log₂ allowed the development of a proper antibody response. Nevertheless, the immunity induced by one dose of the product was partly protective against PCV2 infection, since viremia, shedding and viral load in tissues were significantly reduced in vaccinated pigs compared to controls.     

Efficacy of a reformulated inactivated chimeric PCV1-2 vaccine based on clinical,virological, pathological and immunological examination under field conditions

Inactivated chimeric porcine circovirus (PCV) 1-2 vaccine was initially taken off the market due to concerns that the vaccine virus was not killed and thus further replicated and spread in the pig population. In August 2011, a reformulated inactivated chimeric PCV1-2 vaccine re-entered the market. The efficacy of the reformulated inactivated chimeric PCV1-2 vaccine was evaluated under field conditions for registration as recommended by the Republic of Korea's Animal, Plant & Fisheries Quarantine & Inspection Agency. Three farms were selected based on their history of postweaning multisystemic wasting syndrome (PMWS). On each farm, a total of 50 3-week-old pigs were randomly allocated to one of two treatment groups: (i) vaccinated at 3 weeks of age and (ii) non-vaccinated. Clinical examination indicated that vaccinated animals displayed an improved average daily weight gain (672.2 g/day vs. 625 g/day; difference of +47.3 g/day; P < 0.05) and a reduced time to market (177 days vs. 183 days; difference of −6 days; P < 0.05). Virological examination indicated that vaccinated animals displayed a reduced PCV2 load in the blood and nasal swabs compared to non-vaccinated animals. Pathological examination indicated that vaccination of pigs against PCV2 effectively reduced the number of PMWS-associated microscopic lesions and the PCV2 load in lymphoid tissues compared to non-vaccinated animals in the 3 herds. Immunological examination indicated that vaccinated animals induced PCV2-specific neutralizing antibodies (NA) and interferon-γ-secreting cells (IFN-γ-SCs). A reduction in the PCV2 load in the blood coincided with the appearance of both PCV2-specific NA and IFN-γ-SCs in the vaccinated animals. The number of CD4⁺ cells was decreased in non-vaccinated animals compared to vaccinated animals. The reformulated inactivated chimeric PCV1-2 vaccine seems to be very effective in controlling PCV2 infection based on clinical, virological, pathological, and immunological evaluations under field conditions.     

The immunogenicity and impact on nasopharyngeal carriage of fewer doses of conjugate pneumococcal vaccine immunization schedule

The immunogenicity and impact on carriage of fewer doses of pneumococcal conjugate vaccine (PCV7) followed by booster with pneumococcal polysaccharide vaccine (PPV) were investigated. 684 infants were assigned randomly to one of the three groups that received one (A), two (B) or three (C) doses of PCV7 between 2 and 4 months of age, plus PPV at 10 months. Following primary vaccination protective antibody titers of >0.35 μg/ml against the PCV7 serotypes combined increased significantly with the number of PCV7 doses, 44% vs. 77% vs. 94% (p < 0.001), and correlated positively with the opsonophagocytic indices, but negatively with nasopharyngeal carriage of pneumococcus. The differences in antibody responses and pneumococcal carriage between the groups diminished following booster with PPV, implying that administration of one or two doses of PCV7, with a booster dose of PPV might lower the cost of protection against IPD in young children in resource poor countries.     

Evaluation of 13-valent pneumococcal conjugate vaccine and concomitant meningococcal group C conjugate vaccine in healthy infants and toddlers in Spain

Background

Given the concurrent administration of multiple vaccines during routine pediatric immunizations, efforts to elucidate the potential interference of any vaccine on the immune response to the concomitantly administered antigens are fundamental to prelicensure clinical research.

Methods

This phase 3 randomized controlled trial of 13-valent pneumococcal conjugate vaccine (PCV13) versus 7-valent PCV (PCV7) assessed immune responses of concomitantly administered meningococcal group C conjugated to diphtheria toxin cross-reactive material 197 (MnCCV-CRM₁₉₇) in a 2-dose infant series and 15-month toddler dose.

Results

619 subjects were randomized, 315 to PCV13 and 304 to PCV7. MnCCV-CRM₁₉₇-induced immune responses were similar between the PCV13 and PCV7 groups, with >97% of the subjects achieving a ≥1:8 meningococcal serum bactericidal assay (SBA) titer after both dose 2 and the toddler dose. Geometric mean titers were lower in the PCV13 group 191.22 (167.72, 218.02) versus 266.19 (234.86, 301.71) following dose 2 and 432.28 (361.22, 517.31) versus 730.84 (642.05, 831.91) following the toddler dose. The geometric mean (GM) meningococcal SBA titer ratios (PCV13/PCV7) were 0.72 after dose 2 and 0.59 after the toddler dose. The criteria for MnCCV-CRM₁₉₇ non-inferiority for GM titers were satisfied after dose 2. Percent responders was similar up to titers of 1:128. PCV13 elicited substantial antipneumococcal responses against all 13 serotypes, with ≥90% of the subjects achieving an antibody concentration ≥0.35 μg/mL after dose 3 in the infant series. Safety and tolerability were similar between the vaccine groups.

Conclusions

Immunogenicity results of MnCCV-CRM₁₉₇ for PCV13 compared with PCV7 included lower GMTs, but the clinical significance of this is unknown as the proportion of infants achieving protective MenC antibody titers was comparable in the two groups. Percent responders were similar up to titers of 1:128. PCV13 has an acceptable safety profile in infants and toddlers, while providing expanded coverage against pneumococcal disease.     

Development of a live-attenuated influenza B ΔNS1 intranasal vaccine candidate

We discovered a unique, single amino acid mutation in the influenza B M1 protein promoting viral growth of NS1 truncation mutants in Vero cells. Due to this mutation, we were able to generate an influenza B virus lacking the complete NS1 open reading frame (ΔNS1-B virus) by reverse genetics, which was growing to titers of 8 log₁₀ TCID₅₀/ml in a Vero cell culture-based micro-carrier fermenter. The ΔNS1-B vaccine candidate was attenuated in IFN-competent hosts such as human alveolar epithelial cells (A549) similar to influenza A ΔNS1 viruses. In ferrets, the ΔNS1-B virus was replication-deficient and did not provoke any clinical symptoms. Importantly, a single intranasal immunization of ferrets at a dose as low as 6 log₁₀ TCID₅₀/animal induced a significant HAI response and provided protection against challenge with wild-type influenza B virus. So far, the lack of a ΔNS1-B virus component growing to high titers in cell culture has been limiting the possibility to formulate a trivalent vaccine based on deletion of the NS1 gene. Our study closes this gap and paves the way for the clinical evaluation of a seasonal, trivalent, live replication-deficient ΔNS1 intranasal influenza vaccine.     

Dose-ranging study of a single injection of pneumococcal conjugate vaccine (1 ×, 2 ×, or 4 ×) in healthy subjects aged 70 years or older

Healthy adults aged ≥70 years (N = 443) with no history of pneumococcal vaccination received 7- or 9-valent pneumococcal conjugate vaccine (PCV7 or PCV9) at 1× (PCV7 only), 2× (PCV7 + PCV9), or 4× (2× PCV7 + 2× PCV9) dosage in a randomised, open-label study evaluating pneumococcal protein conjugate vaccine (PnC). Controls received 23-valent pneumococcal polysaccharide vaccine (PPV). Both geometric mean concentration enzyme-linked immunosorbent assay and opsonophagocytic activity antibody titres assessed 1 month after vaccination were significantly increased over baseline titres for all PCV7 serotypes, with a trend toward a dose-dependent immune response. Local reactions for the 4× dose, but not the 2× dose, were statistically significantly higher than for the 1× dose. No treatment-related serious adverse events occurred.     

Have changing pneumococcal vaccination programmes impacted disease in Ontario?

Background

Publicly funded infant 7-valent pneumococcal conjugate vaccine (PCV7) was introduced in Ontario, Canada in 2005 and was replaced by 10- and 13-valent vaccines (PCV10, PCV13) in October 2009 and November 2010, respectively. Among adults ≥ 65 years, a 23-valent polysaccharide vaccine (PPV23) has been universally available since 1996. In January 2012, PCV13 was approved for adults  ≥ 50 years. This study examines the impact of publicly funded vaccination programmes on invasive pneumococcal disease (IPD).

Methods

Laboratory data from population-based surveillance for IPD conducted at the Toronto Invasive Bacterial Disease Network and from Public Health Ontario Laboratories between January 1, 2008 and December 31, 2010 were analyzed.

Results

Between 2008 and 2010 there were 3259 cases of IPD; overall incidence was 7.4/9.3/8.3 per 100,000 in 2008/9/10, respectively. Incidence increased significantly among adults 65+ years during the period; this group had the highest incidence (21.5–25.6/100,000). The second highest incidence in 2008 and 2009 was in infants <1 year, whereas in 2010 it was in children 1–4 years. Among children <5 years, 68% and 19% of serotypes were covered by PCV13 and PCV10, respectively, between 2008 and 2010. In 2009, 6 cases with the 3 additional PCV10 serotypes were reported in infants compared with 2 in 2010. Among persons eligible for PCV7 (born ≥ 2004), there was a 77% decrease in the rate of IPD due to PCV7 serotypes between 2008 and 2010 and a 60% decrease in PCV7 serotypes among persons not vaccine-eligible (born < 2004). There was a 15% difference in serotype coverage between PCV13 and the 23-valent polysaccharide vaccine in adults ≥ 50 years.

Conclusions

During Ontario's PCV7 programme, serotype-specific decreases in IPD were observed, suggesting vaccine programme success, including herd immunity. Our results also suggest some early impact among infants from PCV10 introduction. A substantial burden of disease was also observed among older adults.     

Cost-utility analysis of 10- and 13-valent pneumococcal conjugate vaccines: Protection at what price in the Thai context?

Objective

This study aims to evaluate the costs and outcomes of offering the 10-valent pneumococcal conjugate vaccine (PCV10) and 13-valent pneumococcal conjugate vaccine (PCV13) in Thailand compared to the current situation of no PCV vaccination.

Methods

Two vaccination schedules were considered: two-dose primary series plus a booster dose (2 + 1) and three-dose primary series plus a booster dose (3 + 1). A cost-utility analysis was conducted using a societal perspective. A Markov simulation model was used to estimate the relevant costs and health outcomes for a lifetime horizon. Costs were collected and values were calculated for the year 2010. The results were reported as incremental cost-effectiveness ratios (ICERs) in Thai Baht (THB) per quality adjusted life year (QALY) gained, with future costs and outcomes being discounted at 3% per annum. One-way sensitivity analysis and probabilistic sensitivity analysis using a Monte Carlo simulation were performed to assess parameter uncertainty.

Results

Under the base case-scenario of 2 + 1 dose schedule and a five-year protection, without indirect vaccine effects, the ICER for PCV10 and PCV13 were THB 1,368,072 and THB 1,490,305 per QALY gained, respectively. With indirect vaccine effects, the ICER of PCV10 was THB 519,399, and for PCV13 was THB 527,378. The model was sensitive to discount rate, the change in duration of vaccine protection and the incidence of pneumonia for all age groups.

Conclusions

At current prices, PCV10 and PCV13 are not cost-effective in Thailand. Inclusion of indirect vaccine effects substantially reduced the ICERs for both vaccines, but did not result in cost effectiveness.     

Immunogenicity and safety of pneumococcal conjugate polysaccharide and free polysaccharide vaccines alone or combined in HIV-infected adults in Brazil

Background

Streptococcus pneumoniae is a leading cause of hospitalization in HIV-infected adults therefore pneumococcal vaccine is recommended. The ideal antipneumococcal vaccine and effective vaccination regimen remain controversial and needs further evaluation.

Methods

To assess the efficacy of pneumococcal vaccines alone and combined, a randomized, blinded clinical trial was conducted in Brazil with 331 HIV-patients aged 18–60, with CD4-T cell count ≥200 cells/mm³. Two interventions 60 days apart were done in three schedules: 23-valent pneumococcal polysaccharide vaccine (PPV23)/placebo; 7-valent pneumococcal conjugate vaccine (PCV7)/placebo; and PCV7 plus PPV23. Safety and reactogenicity were evaluated, and immunogenicity was assessed by an IgG enzyme-linked immunosorbent assay to S. pneumoniae serotypes 6B, 9V and 14, performed at baseline, 60 and 180 days after first intervention. Comparison of immunogenicity was based on geometric mean concentration (GMC), percentages of individuals with serotype-specific IgG ≥ 0.35 μg/mL and ≥1.0 μg/mL and proportion of individuals with ≥4-fold increase in specific antibody concentrations for each serotype.

Results

Demographic and HIV conditions were similar, and both vaccines were well tolerated across vaccine groups. Significant increase in IgG-antibodies was observed to all serotypes evaluated. A greater proportion of PCV7 recipients reached and sustained IgG antibody concentrations at least four times as high as those at baseline, for serotypes 6B and 9V. A PPV23 dose after PCV7 did not enhance immunogenicity.

Conclusions

In this first trial conducted with HIV-infected immunologically stable adults in South America, both PPV23 and PCV7 were safe and immunogenic. Evidence suggesting PCV7 was more immunogenic than PPV23, as it elicited higher and persistent ≥4-fold increase of antibodies for 6B and 9V serotypes in a greater proportion of HIV-patients is noteworthy. Despite current recommendation of schedules combining PCV7 and PPV23, there is little evidence to support this practice and we did not observe benefits in this combination.     

Revaccination with 7-valent pneumococcal conjugate vaccine elicits better serologic response than 23-valent pneumococcal polysaccharide vaccine in HIV-infected adult patients who have undergone primary vaccination with 23-valent pneumococcal polysaccharide vaccine in the era of combination antiretroviral therapy

HIV-infected adults who had received 23-valent pneumococcal polysaccharide vaccine (PPV23) five years or more earlier consecutively underwent revaccination with one dose of PPV23 (127 subjects) from December 2005 through October 2007, or upon change in standard of care, non-randomly one (50) or two doses (44) of 7-valent pneumococcal conjugate vaccine (PCV7) from October 2008 through June 2010. Serologic response was defined as ≥2-fold increase in the IgG level plus a level ≥1000 ng/ml 48 weeks following revaccination. At week 48, the response rate was significantly higher in the 2-dose PCV7 group compared with that in the 1-dose PCV7 or PPV23 group (63.6% vs 32.0% vs 8.7%, respectively; P < 0.05). Revaccination with one dose of PCV7 (AOR, 4.57), two doses of PCV7 (AOR, 22.66), and CD4 >350 cells/μl (AOR, 3.24) and undetectable viral load (AOR, 3.87) at revaccination were statistically significantly associated with a better serologic response at week 48. Despite the limitation that study arms were neither randomized nor contemporaneous, we conclude that revaccination with PCV7 appears to elicit a better serologic response than PPV23 in the HIV-infected adults who have received PPV23 five years or more earlier (clinical trial registration number: NCT00885625).     

Impact and effectiveness of 23-valent pneumococcal polysaccharide vaccine against invasive pneumococcal disease in the elderly in England and Wales

In 2003 the existing 23-valent pneumococcal vaccine (PPV23) programme for high risk groups was extended to include all ≥65 year olds in England and Wales, starting with ≥80 year olds and moving to 75–79 and 65–74 year olds by 2005. We conducted an ecological study to assess the impact of the extended PPV23 programme on serotype-specific incidence of invasive pneumococcal disease (IPD) and a case–control study to assess vaccine effectiveness (VE) using the national IPD surveillance dataset. Between 1998 and 2006 IPD incidence caused by PPV23 serotypes in the targeted age-groups was unchanged. IPD caused by the serotypes covered by the 7-valent conjugate vaccine (PCV7) introduced for children in 2006 declined in ≥65 year olds after 2006 but was offset by an increase in non-PCV7 serotypes. This increase was similar for the additional 16 serotypes covered by PPV23 and the non-PPV23 serotypes. For the VE study, vaccine history was obtained for controls (n = 1270) with non-PPV23 IPD diagnosed between November 2003 and December 2010 and a subset of cases (n = 1272) matched for age and time period. VE declined from 48% (95% confidence interval; 32–60%) within two years of vaccination to 15% (−3% to 30%) after five years. Although differences in VE by age and having risk conditions were not statistically significant the highest estimates were in the youngest age group (65–74 years) and in those without risk conditions with a VE estimate of 65% (23–84%) within 2 years of vaccination for non-risk 65–74 year olds. VE differed by serotype (p = 0.005), from −23% (−85% to 19%) for serotype 3 to 63% (29–81%) for 12F. In conclusion PPV23 was effective, particularly in healthy under 75 year olds, but protection waned after 5 years. There was no discernible impact of PPV23 on IPD incidence or PCV7-induced serotype replacement, consistent with the modest overall effectiveness, the 45% increased coverage over the former risk-based programme and lack of herd immunity from the PPV23 programme. Based on the VE estimates PPV23 was still considered a cost-effective intervention for the low risk elderly.     

Intranasal administration of a live non-pathogenic avian H5N1 influenza virus from a virus library confers protective immunity against H5N1 highly pathogenic avian influenza virus infection in mice: Comparison of formulations and administration routes of vaccines

Outbreaks of highly pathogenic avian influenza viruses (HPAIVs) would cause disasters worldwide. Various strategies against HPAIVs are required to control damage. It is thought that the use of non-pathogenic avian influenza viruses as live vaccines will be effective in an emergency, even though there might be some adverse effects, because small amounts of live vaccines will confer immunity to protect against HPAIV infection. Therefore, live vaccines have the advantage of being able to be distributed worldwide soon after an outbreak. In the present study, we found that intranasal administration of a live H5N1 subtype non-pathogenic virus induced antibody and cytotoxic T lymphocyte responses and protected mice against H5N1 HPAIV infection. In addition, it was found that a small amount (100 PFU) of the live vaccine was as effective as 100 μg (approximately 10^10–11 PFU of virus particles) of the inactivated whole particle vaccine in mice. Consequently, the use of live virus vaccines might be one strategy for preventing pandemics of HPAIVs in an emergency.     

Semi-perfusion cultures of suspension MDCK cells enable high cell concentrations and efficient influenza A virus production

Control and prevention of rapid influenza spread among humans depend on the availability of efficient and safe seasonal and pandemic vaccines, made primarily from inactivated influenza virus particles. Current influenza virus production processes rely heavily on embryonated chicken eggs or on cell culture as substrate for virus propagation. Today’s efforts towards process intensification in animal cell culture could innovate viral vaccine manufacturing using high-yield suspension cells in high cell density perfusion processes. In this work, we present a MDCK cell line adapted to grow as single cell suspension with a doubling time of less than 20 h, achieving cell concentrations over 1 × 10⁷ cells/mL in batch mode. Influenza A virus titer obtained in batch infections were 3.6 log₁₀(HAU/100 µL) for total- and 10⁹ virions/mL for infectious virus particles (TCID₅₀), respectively. In semi-perfusion mode concentrations up to 6 × 10⁷ cells/mL, accumulated virus titer of 4.5 log₁₀(HAU/100 µL) and infectious titer of almost 10¹⁰ virions/mL (TCID₅₀) were possible. This exceeds results reported previously for cell culture-based influenza virus propagation by far and suggests perfusion cultures as the preferred method in viral vaccine manufacturing.     

A PCV2 vaccine based on genotype 2b is more effective than a 2a-based vaccine to protect against PCV2b or combined PCV2a/2b viremia in pigs with concurrent PCV2, PRRSV and PPV infection

The predominant genotype of porcine circovirus (PCV) in the pig population today is PCV2b yet PCV2a-based commercial vaccines are considered effective in protecting against porcine circovirus associated disease. The objective of this study was to compare the ability of PCV2a- and PCV2b-based vaccines to control PCV2b viremia in a challenge model that mimics the U.S. field situation. Sixty-three pigs were randomly assigned to one of eight groups. Sixteen pigs were vaccinated with an experimental live-attenuated chimeric PCV1-2a vaccine based on genotype 2a and another 16 pigs with a chimeric PCV1-2b vaccine based on genotype 2b. Challenge was done 28 days post vaccination (dpv) using PCV2b (or a combination of PCV2a and PCV2b), porcine reproductive and respiratory syndrome virus (PRRSV), and porcine parvovirus (PPV) to mimic what commonly occurs in the field. The experiment was terminated 21 days post challenge (dpc) or 49 dpv. Pigs vaccinated with the chimeric PCV1-2b vaccine had significantly higher levels of PCV1-2b viremia and shedding of the PCV1-2b vaccine virus in feces and nasal secretions but also a more robust humoral immune response as evidenced by significantly higher ELISA S/P ratios compared to the PCV1-2a vaccination. Regardless of challenge, the PCV1-2b vaccination significantly reduced the prevalence and amount of PCV2 viremia compared to the PCV1-2a vaccination. Interestingly, in the non-vaccinated pigs concurrent PCV2a infection resulted in clinical disease and increased macroscopic lung lesions compared to pigs challenged with PCV2b alone, further supporting the idea that concurrent PCV2a/PCV2b infection is necessary for optimal PCV2 replication.