Short-term and long-term antibody response by mice after immunization against Neisseria meningitidis B or diphtheria toxoid

A dual-targeting approach using a human bispecific antibody against the receptor-binding domain of the Middle East Respiratory Syndrome Coronavirus

The emergence of the Middle East Respiratory Syndrome Coronavirus (MERS-CoV) has posed a significant global health concern due to its severe respiratory illness and high fatality rate. Currently, despite the potential for resurgence, there are no specific treatments for MERS-CoV, and only supportive care is available. Our study aimed to address this therapeutic gap by developing a potent neutralizing bispecific antibody (bsAb) against MERS-CoV. Initially, we isolated four human monoclonal antibodies (mAbs) that specifically target the MERS-CoV receptor-binding domain (RBD) using phage display technology and an established human antibody library. Among these four selected mAbs, our intensive in vitro functional analyses showed that the MERS-CoV RBD-specific mAb K111.3 exhibited the most potent neutralizing activity against MERS-CoV pseudoviral infection and the molecular interaction between MERS-CoV RBD and human dipeptidyl peptidase 4. Consequently, we engineered a novel bsAb, K207.C, by utilizing K111.3 as the IgG base and fusing it with the single-chain variable fragment of its non-competing pair, K111.1. This engineered bsAb showed significantly enhanced neutralization potential against MERS-CoV compared to its parental mAb. These findings suggest that K207.C may serve as a potential candidate for effective MERS-CoV neutralization, further highlighting the promise of the bsAb dual-targeting approach in MERS-CoV neutralization.

Construction and protective immunogenicity of DNA vaccine pNMB0315 against Neisseria meningitidis serogroup B

Neisseria meningitidis (N. meningitidis) is a major cause of meningitis and sepsis. Capsular polysaccharide‑based vaccines against serogroups A, C, Y, and W135 are available; however, the development of a vaccine against N. meningitidis serogroup B (NMB) has been problematic. NMB0315 is an outer membrane protein of NMB that may be a virulence factor for N. meningitidis and a possible target for functional bactericidal antibodies. The present study aimed to develop a potent DNA vaccine against NMB by cloning the NMB0135 gene into the pcDNA3.1(+) vector to construct the recombinant plasmid pcDNA3.1(+)/NMB0315 (designated pNMB0315). pNMB0315 was transfected into eukaryotic COS‑7 and RAW264.7 cells to express the recombinant (r)NMB0315 protein. Protective immunogenicity of the DNA vaccine was assessed in an in vivo mouse model. The levels of rNMB0315‑specific immunoglobulin G (IgG), IgG1 and IgG2a antibodies in the pNMB0315‑immunized group increased dramatically up to week 6 following the initial vaccination, and were significantly higher compared with the levels in the Control groups. The serum concentrations of interleukin‑4 and interferon‑γ were significantly higher in the pNMB0315‑immunized group compared with the control groups. Following intraperitoneal challenge with a lethal dose of NMB strain MC58, the survival rate in the pNMB0315 + CpG group was 70% (14 out of 20 mice) at 14 days; by contrast, all mice in the control groups succumbed within 3 days. The serum bactericidal titers of the pNMB0315 + CpG group in vitro reached 1:128 following three immunizations. The results indicated that pNMB0315 may serve as a promising DNA vaccine against NMB.

A purified MAA-based ELISA is a useful tool for determining anti-MAA antibody titer with high sensitivity

Atherosclerosis is widely accepted to be a chronic inflammatory disease, and the immunological response to the accumulation of LDL is believed to play a critical role in the development of this disease. 1,4-Dihydropyridine-type MAA-adducted LDL has been implicated in atherosclerosis. Here, we have demonstrated that pure MAA-modified residues can be chemically conjugated to large proteins without by-product contamination. Using this pure antigen, we established a purified MAA-ELISA, with which a marked increase in anti-MAA antibody titer was determined at a very early stage of atherosclerosis in 3-month ApoE-/- mice fed with a normal diet. Our methods of Nε-MAA-L-lysine purification and purified antigen-based ELISA will be easily applicable for biomarker-based detection of early stage atherosclerosis in patients, as well as for the development of an adduct-specific Liquid Chromatography/Mass Spectrometry-based quantification of physiological and pathological levels of MAA.

Recombinant Neisseria surface protein A is a potential vaccine candidate against Neisseria meningitides serogroup B

Neisseria meningitidis is the pathogen of epidemic encephalomyelitis and is responsible for permanent damage to the brain and nervous system. In the present study, the prokaryotic expression vector pGEX-6p-1/neisseria surface protein A (NspA) was constructed and the immune protective effect was investigated with the purified recombinant rNspA. Female BALB/c mice were immunized by intraperitoneal inoculation of rNspA, glutathione S-transferase (GST) or phosphate-buffered saline (PBS). The protection experiment in mice demonstrated that the protection rate of the rNspA group was 85% against the N. meningitidis strain MC58, and a serum bactericidal assay in vitro revealed that the serum bactericidal titer of the rNspA group reached 1:64 following three immunizations. The levels of specific immunoglobulin (Ig) A (SIgA), IgG, IgG1, IgG2a, IgG2b and IgG3 of mice in the rNspA group peaked at week six and were higher than those in the mice in the GST and PBS groups. The levels of stimulation index, interleukin-4 and interferon-γ in the culture supernatant of the spleen lymphocytes of the rNspA group increased in a time-dependent manner and were higher than those of the mice in the GST and PBS groups over the same period. The results suggested that rNspA may induce increased specific humoral and cellular immune responses, and that it is effectively protective against N. meningitidis serogroup B in mice. The present study offered novel evidence that may lead to the development of a novel effective N. meningitidis serogroup B vaccine.