Vaccine and Infectious Disease Organization (VIDO), University of Saskatchewan, Saskatoon, SK, Canada.
School of Public Health, University of Saskatchewan, Saskatoon, SK, Canada.
Front Immunol. 2022 Aug 2;13:943481. doi: 10.3389/fimmu.2022.943481. eCollection 2022.
Increasing the number of CpG dinucleotides in RNA viral genomes, while preserving the original amino acid composition, leads to impaired infection which does not cause disease. Beneficially, impaired infection evokes antiviral host immune responses providing a cutting-edge vaccine approach. For example, we previously showed that CpG-enriched Zika virus variants cause attenuated infection phenotypes and protect against lethal challenge in mice. While CpG recoding is an emerging and promising vaccine approach, little is known about infection phenotypes caused by recoded viruses , particularly in non-rodent species. Here, we used well-established mouse and porcine models to study infection phenotypes of the CpG-enriched neurotropic and congenital virus-Zika virus, directly in the target tissues-the brain and placenta. Specifically, we used the uttermost challenge and directly injected mice intracerebrally to compare infection phenotypes caused by wild-type and two CpG-recoded Zika variants and model the scenario where vaccine strains breach the blood-brain barrier. Also, we directly injected porcine fetuses to compare infection phenotypes and model the scenario where recoded vaccine strains breach the placental barrier. While overall infection kinetics were comparable between wild-type and recoded virus variants, we found convergent phenotypical differences characterized by reduced pathology in the mouse brain and reduced replication of CpG-enriched variants in fetal lymph nodes. Next, using next-generation sequencing for the whole virus genome, we compared the stability of introduced CpG dinucleotides during prolonged virus infection in the brain and placenta. Most introduced CpG dinucleotides were preserved in sequences of recoded Zika viruses showing the stability of vaccine variants. Altogether, our study emphasized further directions to fine-tune the CpG recoding vaccine approach for better safety and can inform future immunization strategies.
增加 RNA 病毒基因组中 CpG 二核苷酸的数量，同时保持原始的氨基酸组成，会导致感染受损而不会引起疾病。有益的是，受损的感染会引发抗病毒的宿主免疫反应，为疫苗提供了一种前沿的方法。例如，我们之前曾表明，富含 CpG 的寨卡病毒变体导致感染表型减弱，并在小鼠中预防致命性挑战。虽然 CpG 重编码是一种新兴且有前途的疫苗方法，但人们对重编码病毒引起的感染表型知之甚少，特别是在非啮齿动物物种中。在这里，我们使用成熟的小鼠和猪模型来研究富含 CpG 的神经毒和先天性病毒寨卡病毒在目标组织-大脑和胎盘-中的感染表型。具体来说，我们使用最极端的挑战，直接向小鼠脑内注射，以比较野生型和两种 CpG 重编码寨卡变体引起的感染表型，并模拟疫苗株突破血脑屏障的情况。此外，我们直接向猪胎儿注射，以比较感染表型，并模拟重编码疫苗株突破胎盘屏障的情况。虽然野生型和重编码病毒变体之间的总体感染动力学相似，但我们发现了趋同的表型差异，其特征是在小鼠大脑中的病理学减少和富含 CpG 的变体在胎儿淋巴结中的复制减少。接下来，我们使用下一代测序对整个病毒基因组进行测序，以比较在大脑和胎盘中长期感染过程中引入的 CpG 二核苷酸的稳定性。大多数引入的 CpG 二核苷酸在重编码寨卡病毒的序列中得到了保留，这表明了疫苗变体的稳定性。总之，我们的研究强调了进一步调整 CpG 重编码疫苗方法的方向，以提高安全性，并为未来的免疫策略提供信息。
