Induction of cross-neutralizing antibodies by sequential immunization with heterologous papillomavirus L1VLPs and its implications for HPV prophylactic vaccines

Enhancement of Neutralization Responses through Sequential Immunization of Stable Env Trimers Based on Consensus Sequences from Select Time Points by Mimicking Natural Infection

HIV-1 vaccines have been challenging to develop, partly due to the high level of genetic variation in its genome. Thus, a vaccine that can induce cross-reactive neutralization activities will be needed. Studies on the co-evolution of antibodies and viruses indicate that mimicking the natural infection is likely to induce broadly neutralizing antibodies (bnAbs). We generated the consensus Env sequence for each time point in subject CH505, who developed broad neutralization activities, and selected five critical time points before broad neutralization was detected. These consensus sequences were designed to express stable Env trimers. Priming with the transmitted/founder Env timer and sequential boosting with these consensus Env trimers from different time points induced broader and more potent neutralizing activities than the BG505 Env trimer in guinea pigs. Analysis of the neutralization profiles showed that sequential immunization of Env trimers favored nAbs with gp120/gp41 interface specificity while the BG505 Env trimer favored nAbs with V2 specificity. The unique features such as consensus sequences, stable Env trimers and the sequential immunization to mimic natural infection likely has allowed the induction of improved neutralization responses.

Genetic diversity and bioinformatic analysis in the L1 gene of HPV genotypes 31, 33, and 58 circulating in women with normal cervical cytology

BACKGROUND

HPV-31, -33, and -58, along with HPV-45 and -52, account for almost 11% of HPV-associated cancers. Our previous studies showed that after HPV-16 and -51, HPV-58 was common and HPV-31 was as frequent as HPV-18 among Iranian women with normal cytology. Hence, in this study, we aimed to investigate the intra-type variations in L1 genes of HPV-58, -31, and -33 to find the predominant lineages circulating in women with normal cytology.

METHODS

Complete coding sequencing of the L1 gene was amplified and nucleotide and amino acid sequences were compared to those of the references. The selective pressure on L1 protein and whether the variations of the L1 genes embed in L1 loops, or N-glycosylated sites were also investigated.

RESULTS

B1, A, and A1 (sub)lineages were common in the HPV-58, -33, and -31 samples, respectively. Ninety nucleotide mutations were observed. Twenty nine nucleotide changes corresponded to nonsynonymous substitutions in which seventeen mutations were located in L1 loops. Only one codon position in HPV-58 sequences was found as the positive selection. No difference was observed in N-glycosylation sites between reference and understudied amino acid sequences.

CONCLUSION

In the current study, we reported, for the first time, the (sub) lineages, amino acid, and genetic diversity in the L1 gene of circulating HPV-58, -33, and -31, in women with normal cytology, in Iran. Such studies can not only have epidemiological values, but also aid to set vaccination programs.

Immunogenicity of novel DNA vaccines encoding receptor-binding domain (RBD) dimer-Fc fusing antigens derived from different SARS-CoV-2 variants of concern

The continuously emerging of severe acute respiratory syndrome coronavirus-2 variants of concern (VOCs) led to a decline in effectiveness of the first-generation vaccines. Therefore, optimized vaccines and vaccination strategies, which show advantages in protecting against VOCs, are urgently needed. Here we constructed an optimized DNA vaccine plasmid containing built-in CpG adjuvant, and designed vaccine candidates encoding five forms of antigens derived from Wuhan-Hu-1. The results showed that plasmid with receptor binding domain (RBD) dimer-Fc fusing antigen (2RBD-Fc) induced the highest level of RBD-specific IgG and neutralizing antibodies in mice. Then 2dRBD-Fc and 2omRBD-Fc vaccines, respectively derived from delta and omicron VOCs, were constructed. The 2dRBD-Fc induced potent humoral and cellular immune responses, while the immunogenicity of 2omRBD-Fc was low. We also observed that sequential immunization with 2RBD-Fc, 2dRBD-Fc and 2omRBD-Fc effectively elicited neutralizing antibodies against each immunized strain, and RBD-specific T cell responses. To be noted, the Wuhan-Hu-1, delta and omicron neutralizing antibody titers induced by sequential immunization were comparable to that induced by repetitive immunization with 2RBD-Fc, 2dRBD-Fc or 2omRBD-Fc respectively. The results suggest that sequential immunization with DNA vaccines encoding potent antigens derived from different VOCs, may be a promising strategy to elicit immune responses against multiple variants.

Innovative vaccine platforms against infectious diseases: Under the scope of the COVID-19 pandemic

While classic vaccines have proved greatly efficacious in eliminating serious infectious diseases, innovative vaccine platforms open a new pathway to overcome dangerous pandemics via the development of safe and effective formulations. Such platforms play a key role either as antigen delivery systems or as immune-stimulators that induce both innate and adaptive immune responses. Liposomes or lipid nanoparticles, virus-like particles, nanoemulsions, polymeric or inorganic nanoparticles, as well as viral vectors, all belong to the nanoscale and are the main categories of innovative vaccines that are currently on the market or in clinical and preclinical phases. In this paper, we review the above formulations used in vaccinology and we discuss their connection with the development of safe and effective prophylactic vaccines against SARS-CoV-2.