Timing of maternal vaccination against COVID-19 for effective protection of neonates: cohort study.

Introduction: Although the safety and effectiveness of COVID-19 vaccination during pregnancy have been proven, there is still little data explaining neonatal outcomes of maternal pre-pregnancy vaccination. Methods: Here, we investigated the impact of vaccination and SARS-CoV-2 infection on maternal-neonate immune response in a cohort study involving 141 pregnant individuals, and defined the importance of maternal COVID-19 vaccination timing for its effectiveness. Results and discussion: Our data indicate that vertically transferred maternal hybrid immunity provides significantly better antiviral protection for a neonate than either maternal post-infection or post-vaccination immunity alone. Higher neutralization potency among mothers immunized before pregnancy and their newborns highlights the promising role of pre-pregnancy vaccination in neonatal protection. A comparison of neutralizing antibody titers calculated for each dyad suggests that infection and pre-/during-pregnancy vaccination all support transplacental transfer, providing the offspring with strong passive immunity against SARS-CoV-2. Analysis of neutralizing antibody levels in maternal sera collected during pregnancy and later during delivery shows that immunization may exert a positive effect on maternal protection.

Baculovirus Vector-Based Varicella-Zoster Virus Vaccine as a Promising Alternative with Enhanced Safety and Therapeutic Functions.

Varicella-zoster virus (VZV) poses lifelong risks, causing varicella and herpes zoster (HZ, shingles). Currently, varicella and HZ vaccines are predominantly live attenuated vaccines or adjuvanted subunit vaccines utilizing VZV glycoprotein E (gE). Here, we propose our vaccine candidates involving a comparative analysis between recombinant baculoviral vector vaccines (AcHERV) and a live attenuated vaccine strain, vOka. AcHERV vaccine candidates were categorized into groups encoding gE only, VZV glycoprotein B (gB) only, or both gE and gB (gE-gB) as AcHERV-gE, AcHERV-gB, and AcHERV-gE-gB, respectively. Humoral immune responses were evaluated by analyzing total IgG, IgG1, IgG2a, and neutralizing antibodies. Cell-mediated immunity (CMI) responses were evaluated by enzyme-linked immunospot (ELISPOT) assay and Th1/Th2/Th17 cytokine profiling. In the mouse model, AcHERV-gE-gB elicited similar or higher total IgG, IgG2a, and neutralizing antibody levels than vOka and showed robust VZV-specific CMI responses. From the perspective of antigens encoded in vaccines and their relationship with CMI response, both AcHERV-gB and AcHERV-gE-gB demonstrated results equal to or superior to AcHERV-gE, encoding only gE. Taken together, these results suggest that AcHERV-gE-gB can be a novel candidate for alleviating risks of live attenuated vaccine-induced latency and effectively preventing varicella during early stages of life while providing strong CMI for effective resistance against HZ and therapeutic potential in later stages of life.

Comparative Biodistribution Study of Baculoviral and Adenoviral Vector Vaccines against SARS-CoV-2.

Various types of vaccines have been developed against COVID-19, including vector vaccines. Among the COVID-19 vaccines, AstraZeneca's chimpanzee adenoviral vaccine was the first to be commercialized. For viral vector vaccines, biodistribution studies are critical to vaccine safety, gene delivery, and efficacy. This study compared the biodistribution of the baculoviral vector vaccine (AcHERV-COVID19) and the adenoviral vector vaccine (Ad-COVID19). Both vaccines were administered intramuscularly to mice, and the distribution of the SARS-CoV-2 S gene in each tissue was evaluated for up to 30 days. After vaccination, serum and various tissue samples were collected from the mice at each time point, and IgG levels and DNA copy numbers were measured using an enzyme-linked immunosorbent assay and a quantitative real-time polymerase chain reaction. AcHERV-COVID19 and Ad-COVID19 distribution showed that the SARS-CoV-2 spike gene remained predominantly at the injection site in the mouse muscle. In kidney, liver, and spleen tissues, the AcHERV-COVID19 group showed about 2-4 times higher persistence of the SARS-CoV-2 spike gene than the Ad-COVID19 group. The distribution patterns of AcHERV-COVID19 and Ad-COVID19 within various organs highlight their contrasting biodistribution profiles, with AcHERV-COVID19 exhibiting a broader and prolonged presence in the body compared to Ad-COVID19. Understanding the biodistribution profile of AcHERV-COVID19 and Ad-COVID19 could help select viral vectors for future vaccine development.

Baculoviral COVID-19 Delta DNA vaccine cross-protects against SARS-CoV2 variants in K18-ACE2 transgenic mice.

After severe acute respiratory syndrome coronavirus-2 (SARS-CoV2) made the world tremble with a global pandemic, SARS-CoV2 vaccines were developed. However, due to the coronavirus's intrinsic nature, new variants emerged, such as Delta and Omicron, refractory to the vaccines derived using the original Wuhan strain. We developed an HERV-enveloped recombinant baculoviral DNA vaccine against SARS-CoV2 (AcHERV-COVID19S). A non-replicating recombinant baculovirus that delivers the SARS-CoV2 spike gene showed a protective effect against the homologous challenge in a K18-hACE2 Tg mice model; however, it offered only a 50 % survival rate against the SARS-CoV2 Delta variant. Therefore, we further developed the AcHERV-COVID19 Delta vaccine (AcHERV-COVID19D). The AcHERV-COVID19D induced higher neutralizing antibodies against the Delta variant than the prototype or Omicron variant. On the other hand, cellular immunity was similarly high for all three SARS-CoV2 viruses. Cross-protection experiments revealed that mice vaccinated with the AcHERV-COVID19D showed 100 % survival upon challenge with Delta and Omicron variants and 71.4 % survival against prototype SARS-CoV2. These results support the potential of the viral vector vaccine, AcHERV-COVID19D, in preventing the spread of coronavirus variants such as Omicron and SARS-CoV2 variants.

The Safe Baculovirus-Based PrM/E DNA Vaccine Protected Fetuses Against Zika Virus in A129 Mice.

The Zika virus (ZIKV) is a mosquito-borne member of the Flaviviridae family of enveloped RNA viruses. The correlation between viral infection and fetal microcephaly was revealed in 2015, yet we still lack a vaccine against ZIKV. Here, we present a genetic vaccine that delivers the premembrane (prM) and envelope (E) genes of ZIKV using a recombinant baculovirus vector that expresses a human endogenous retrovirus (HERV) envelope on its surface to enhance gene delivery. We observed that baculoviruses with HERV envelopes (AcHERV) exhibited specifically higher gene transfer efficiency in human cells compared to the wild-type baculovirus vector. Using the AcHERV baculovirus vector, we constructed a recombinant baculovirus vaccine encoding ZIKV prM/E genes (AcHERV-ZIKV), which are major targets of neutralizing antibodies. Mice immunized twice with AcHERV-ZIKV exhibited high levels of IgG, neutralizing antibodies, and IFN-γ. In challenge tests in IFN knock-out mice (A129), AcHERV-ZIKV showed complete protection in both challenge and pregnancy tests. These results suggest that AcHERV-ZIKV could be a potential vaccine candidate for human application.

Effect of Fc Fusion on Folding and Immunogenicity of Middle East Respiratory Syndrome Coronavirus Spike Protein.

Middle East respiratory syndrome coronavirus (MERS-CoV) induces severe respiratory impairment with a reported mortality rate of ~36% in humans. The absence of clinically available MERS-CoV vaccines and treatments to date has resulted in uncontrolled incidence and propagation of the virus. In vaccine design, fusion with the IgG Fc domain is reported to increase the immunogenicity of various vaccine antigens. However, limited reports have documented the potential negative effects of Fc fusion on vaccine antigens. To determine whether Fc fusion affects the immunogenicity of MERS-CoV antigen, we constructed a Fcassociated MERS-CoV spike protein (eS770-Fc, 110 kDa), whereby human IgG4 Fc domain was fused to MERS-CoV spike protein (eS770) via a Gly/Pro linker using baculovirus as the expression system. For comparative analyses, two eS770 proteins lacking the IgG4 Fc domain were generated using the IdeS protease (eS770-ΔFc) or His tag attachment (eS770-His) and the immunogenicity of the above constructs were examined following intramuscular immunization in mice. Contrary to expectations, non-Fc spike proteins (eS770-ΔFc, eS770-His; 90 kDa) showed higher immunogenicity than the Fc fusion protein (eS770-Fc). Moreover, unlike non- Fc spike proteins, eS770-Fc immunization did not elicit neutralizing antibodies against MERSCoV. The lower immunogenicity of Fc-fused eS770 was related to alterations in the structural conformation of the spike protein. Taken together, our results indicate that IgG Fc fusion reduces the immunogenicity of eS770 by interfering with the proper folding structure.