An inactivated poliovirus vaccine using Sabin strains produced on the serum-free PER.C6® cell culture platform is immunogenic and safe in a non-human primate model

BackgroundThe World Health Organization recommends the development of affordable next-generation inactivated poliovirus vaccines (IPV) using attenuated poliovirus Sabin strains. Previously, we introduced a novel PER.C6® cell culture platform, which allows for high yield production of an affordable trivalent Sabin IPV vaccine.MethodsImmunogenicity and safety of this novel PER.C6®-based Sabin-IPV (sIPV) was assessed in rats and non-human primates (NHPs). NHPs received one of four different dose dilutions vaccine according to current human schedule (three prime-immunizations and one boost immunization). For comparison, NHPs received commercially available reference Salk IPV or sIPV.ResultsDose-dependent immunogenicity and good tolerability was observed for the PER.C6®-based sIPV formulations in rats and NHPs. In NHPs, the lowest tested dose that induced anti-Sabin virus-neutralizing antibody titers that were non-inferior to commercial sIPV after three immunizations was 5-7.5-25 D-antigen units for type 1, 2 and 3 respectively.DiscussionPER.C6®-based sIPV induced comparable immunogenicity to commercial Salk IPV and sIPV vaccines in NHPs. Together with the absence of any preclinical safety signals, these data warrant further testing in clinical trials. sIPV produced on the PER.C6® cell platform could be one solution to the need for an affordable and immunogenic IPV to achieve and maintain global polio eradication.     

Safety and immunogenicity of a primary series of Sabin-IPV with and without aluminum hydroxide in infants

Background

An inactivated poliovirus vaccine (IPV) based on attenuated poliovirus strains (Sabin-1, -2 and -3) was developed for technology transfer to manufacturers in low- and middle-income countries in the context of the global polio eradication initiative.

Method

Safety and immunogenicity of Sabin-IPV (sIPV) was evaluated in a double-blind, randomized, controlled, dose-escalation trial in the target population. Healthy infants (n = 20/group) aged 56–63 days, received a primary series of three intramuscular injections with low-, middle- or high-dose sIPV with or without aluminum hydroxide or with the conventional IPV based on wild poliovirus strains (wIPV). Virus-neutralizing titers against both Sabin and wild poliovirus strains were determined before and 28 days after three vaccinations.

Results

The incidence of local and systemic reactions was comparable with the wIPV. Seroconversion rates after three vaccinations were 100% for type 2 and type 3 polioviruses (both Sabin and wild strains) and 95–100% for type 1 polioviruses. Median titers were high in all groups. Titers were well above the log₂(titer) correlated with protection (=3) for all groups. Median titers for Sabin-2 were 9.3 (range 6.8–11.5) in the low-dose sIPV group, 9.2 (range 6.8–10.2) in the low-dose adjuvanted sIPV group and 9.8 (range 5.5–15.0) in the wIPV group, Median titers against MEF-1 (wild poliovirus type 2) were 8.2 (range 4.8–10.8) in the low-dose sIPV group, 7.3 (range 4.5–10.2) in the low-dose adjuvanted Sabin-IPV group and 10.3 (range 8.5–17.0) in the wIPV group. For all poliovirus types the median titers increased with increasing dose levels.

Conclusion

sIPV and sIPV adjuvanted with aluminum hydroxide were immunogenic and safe at all dose levels, and comparable with the wIPV.EudraCTnr: 2011-003792-11, NCT01709071.     

候选无细胞百白破-Sabin株灭活脊髓灰质炎联合疫苗在大鼠上的免疫保护效果研究

目的观察候选无细胞百白破-Sabin株灭活脊髓灰质炎联合疫苗(DTaP-sIPV)在大鼠中的免疫保护效果,为疫苗临床前研究提供依据。方法将候选疫苗DTaP-sIPV、无细胞百白破-灭活脊髓灰质炎-b型流感嗜血杆菌联合疫苗(DTaP-IPV/Hib)、吸附无细胞百白破-b型流感嗜血杆菌联合疫苗(DTaP/Hib)、百日咳疫苗效力参考品(全细胞疫苗,wP)按0、30、60 d 3剂免疫程序免疫Wistar大鼠,检测各组大鼠每剂免疫后的血清中各组分抗体水平。在免疫完成后3周,用百日咳18323株通过气雾攻击的方式感染大鼠。在感染后的第3、7、14、21和28天检测各组白细胞数、肺部菌落克隆形成数以及百日咳疫苗组分抗体变化水平。结果候选疫苗组3剂次免疫完成后PT抗体几何平均滴度(GMT,log2)为16.74,FHA抗体GMT为18.44,PRN抗体GMT为10.75,DT抗体GMT为17.34,TT抗体GMT为17.84,针对3种Sabin脊髓灰质炎病毒株(Ⅰ、Ⅱ和Ⅲ型)的抗体的GMT分别为7.57、8.41和9.70,均达到100%阳转。候选疫苗抗原组分抗体除了PRN和I型IPV外,其他组分抗体水平均与疫苗对照组相比无显著性差异。在基础免疫完成后3周对大鼠进行百日咳杆菌气雾攻击,各疫苗组均表现较好的保护效果,白细胞水平都呈现平稳状态,虽然在肺部也检测到少量细菌定植,但各疫苗组间差异不明显,且在感染后第28天都清除至检测限;而空白对照组在肺部则检测到了大量细菌定植,且在感染后第28天都并未清除至检测限,百日咳特异性的FHA和PRN抗体在感染后的第14天也出现了相应的升高。结论候选疫苗在Wistar大鼠模型上具有较好的免疫保护效果。     

Production of high titer attenuated poliovirus strains on the serum-free PER.C6® cell culture platform for the generation of safe and affordable next generation IPV

BackgroundAs poliovirus eradication draws closer, alternative Inactivated Poliovirus Vaccines (IPV) are needed to overcome the risks associated with continued use of the Oral Poliovirus Vaccine and of neurovirulent strains used during manufacture of conventional (c) IPV. We have previously demonstrated the susceptibility of the PER.C6^® cell line to cIPV strains; here we investigated the suspension cell culture platform for growth of attenuated poliovirus strains.MethodsWe examined attenuated Sabin strain productivity on the PER.C6^® cell platform compared to the conventional Vero cell platform. The suitability of the suspension cell platform for propagation of rationally-attenuated poliovirus strains (stabilized Sabin type 3 S19 derivatives and genetically attenuated and stabilized MonoCre(X) strains), was also assessed. Yields were quantified by infectious titer determination and D-antigen ELISA using either serotype-specific polyclonal rabbit sera for Sabin strains or monoclonal cIPV-strain-specific antibodies for cIPV, S19 and MonoCre(X) strains.ResultsPER.C6^® cells supported the replication of Sabin strains to yields of infectious titers that were in the range of cIPV strains at 32.5 °C. Sabin strains achieved 30-fold higher yields (p < 0.0001) on the PER.C6^® cell platform as compared to the Vero cell platform in infectious titer and D-antigen content. Furthermore, Sabin strain productivity on the PER.C6^® cell platform was maintained at 10 l scale. Yields of infectious titers of S19 and MonoCre(X) strains were 0.5–1 log₁₀ lower than seen for cIPV strains, whereas D-antigen yield and productivities in doses/ml using rationally-attenuated strains were in line with yields reported for cIPV strains.ConclusionsSabin and rationally-attenuated polioviruses can be grown to high infectious titers and D-antigen yields. Sabin strain infection shows increased productivity on the PER.C6^® cell platform as compared to the conventional Vero cell platform. Novel cell platforms with the potential for higher yields could contribute to increased affordability of a next generation of IPV vaccines needed for achieving and maintaining poliovirus eradication.     

Reactogenicity and immunogenicity of inactivated poliovirus vaccine produced from Sabin strains: A phase I Trial in healthy adults in Cuba

Background

To ensure that developing countries have the option to produce inactivated poliovirus vaccine (IPV), the Global Polio Eradication Initiative has promoted the development of an IPV using Sabin poliovirus strains (Sabin IPV). This trial assessed the reactogenicity and immunogenicity of Sabin IPV and adjuvanted Sabin IPV in healthy adults in Cuba.

Methods

This is a randomized, controlled phase I trial, enrolling 60 healthy (previously vaccinated) male human volunteers, aged 19–23 years to receive one dose of either Sabin IPV (20:32:64 DU/dose), adjuvanted Sabin IPV (10:16:32 DU/dose), or conventional Salk IPV (40:8:32 DU/dose). The primary endpoint for reactogenicity relied on monitoring of adverse events. The secondary endpoint measured boosting immune responses (i.e. seroconversion or 4-fold rise) of poliovirus antibody, assessed by neutralization assays.

Results

Sixty subjects fulfilled the study requirements. No serious adverse events reported were attributed to trial interventions during the 6-month follow-up period. Twenty-eight days after vaccination, boosting immune responses against poliovirus types 1–3 were between 90% and 100% in all vaccination groups. There was a more than 6-fold increase in median antibody titers between pre- and post-vaccination titers in all vaccination groups.

Discussion

Both Sabin IPV and adjuvanted Sabin IPV were well tolerated and immunogenic against all poliovirus serotypes. This result suggests that the aluminum adjuvant may allow a 50% (or higher) dose reduction.     

Development of oral CTL vaccine using a CTP-integrated Sabin 1 poliovirus-based vector system

We developed a CTL vaccine vector by modification of the RPS-Vax system, a mucosal vaccine vector derived from a poliovirus Sabin 1 strain, and generated an oral CTL vaccine against HIV-1. A DNA fragment encoding a cytoplasmic transduction peptide (CTP) was integrated into the RPS-Vax system to generate RPS-CTP, a CTL vaccine vector. An HIV-1 p24 cDNA fragment was introduced into the RPS-CTP vector system and a recombinant poliovirus (rec-PV) named vRPS-CTP/p24 was produced. vRPS-CTP/p24 was genetically stable and efficiently induced Th1 immunity and p24-specific CTLs in immunized poliovirus receptor-transgenic (PVR-Tg) mice. In challenge experiments, PVR-Tg mice that were pre-immunized orally with vRPS-CTP/p24 were resistant to challenge with a lethal dose of p24-expressing recombinant vaccinia virus (rMVA-p24). These results suggested that the RPS-CTP vector system had potential for developing oral CTL vaccines against infectious diseases.