Impact of the Route and Schedule of Immunization on the Serological and Virological Response of Chronic Hepatitis B Patients Treated with HeberNasvac.

HeberNasvac is a recently developed therapeutic vaccine for chronic hepatitis B (CHB) administered by intranasal (IN) and subcutaneous (SC) routes in a 14 days/10 doses schedule. To compare different schedules and routes of immunizations, a group of patients received four different vaccination regimens in a placebo-controlled factorial study. Subsequently, patients were followed for a minimum time of 48 weeks. Samples collected at the end of the follow-up were compared with initial samples. Groups I and II received the product by IN/SC routes, every 14 and 7 days, respectively. Groups III and IV were treated by SC route alone following a 14 and 7 days schedule. A group of 21 CHB patients received the vaccine in four different schedules and eight patients received placebo for a total of 29 patients enrolled. The 61.9% of vaccinees reduced their VL ≥2Log compared with baseline levels and 25% in placebo group. The 47.6% of vaccines reduced HBV levels to undetectable, 25% in placebo. HBeAg loss and seroconversion to anti-HBeAg was only achieved in vaccinees, 4 out of 9 (44.4%), and 40% (8 out of 20) developed anti-HBs response, none in placebo group. Reduction of HBsAg level in ≥1Log was achieved in the 35.0% of vaccinees and in none of the placebo-treated patients. Considering the individual and factorial analysis, significant HBV DNA reduction was detected in groups I and II, immunized by IN/SC routes. A significantly higher proportion of patients reducing VL to ≥2Log was also detected grouping the patients treated by IN/SC routes (G I + II) and grouping those inoculated every 14 days (G I + III), with 72.7% and 63.6%, respectively, compared with the placebo group (25.0%). The patients immunized every 14 days (G I + G III) also reduced the HBsAg levels compared with baseline. In conclusion, after more than 48 weeks of treatment-free follow-up, HeberNasvac-treated patients demonstrated superior responses compared with the placebo group in terms of antiviral and serological responses. The factorial analysis evidenced that the schedule combining the IN route of immunization and the frequency of 14 days resulted in the stronger antiviral and serological responses. Present results support the study of IN-only immunization schedules in future and was consistent with previous results. Long-lasting follow-ups were done to explore histological variables and the progression of serological variables in order to detect late responders. How to cite this article: Freyre FM, Aguiar JA, Cinza Z, et al. Impact of the Route and Schedule of Immunization on the Serological and Virological Response of Chronic Hepatitis B Patients Treated with HeberNasvac. Euroasian J Hepato-Gastroenterol 2023;13(2):73-78.

Identification and characterization of phage-displayed peptide mimetics of Neisseria meningitidis serogroup B capsular polysaccharide.

Neisseria meningitidis causes meningitis and septicemia. There is no single vaccine against all serogroup B meningococcal (MenB) strains up to now. Their capsular polysaccharide (MenB CPS) bears epitopes both cross-reacting and non-cross-reactive with human polysialic acid. A bactericidal and protective antibody mAb (13D9) recognizing a unique epitope in MenB CPS was used to screen a phage-displayed peptide library. Four peptides, able to bind mAb 13D9 in competition with MenB CPS, were identified. Immunization of mice with the phage-displayed peptides elicited anti-peptide IgG antibodies, mainly IgG(2a) for 3 of the peptides and bactericidal and protective antibody levels for one of them. Peptides specifically targeting the immune response toward epitopes found only in MenB CPS could be considered for a universal vaccine against serogroup B meningococcal strains.

Study of various presentation forms for a peptide mimetic of Neisseria meningitidis serogroup B capsular polysaccharide.

The formulation of a broadly protective vaccine to prevent the serogroup B Neisseria meningitidis (MenB) disease is still an unmet medical need. We have previously reported the induction of bactericidal and protective antibodies against MenB after immunization of mice with a phage-displayed peptide named 4 L-5. This peptide mimics a capsular polysaccharide (CPS) epitope in MenB. With the aim of developing vaccine formulations that could be used in humans, we evaluate in this study various forms of presentation to the immune system of the 4 L-5 sequence, based on synthetic peptides. We synthesized the following: (i) a linear 4 L-5 peptide, (ii) a multiple antigen peptide containing four copies of the 4 L-5 sequence (named MAP), which was then dimerized, and the product named dimeric MAP, and (iii) a second multiple antigen peptide, in this case with two copies of the 4 L-5 sequence and a copy of a T-helper cell epitope of tetanus toxoid, which was then dimerized and the product named MAP-TT. The linear peptide, the MAP, and the dimeric MAP were conjugated to the carrier protein P64K by different conjugation methods. Plain antigens and antigens coupled to P64K were used to immunize BALB/c mice. Of those variants that gave immunogenic results, MAP-TT rendered the highest levels of specific antipeptide IgG antibodies and serum bactericidal activity. These results can find application in the development of meningococcal vaccine candidates and in peptide-based vaccines strategies.

Purified capsular polysaccharide of Neisseria meningitidis serogroup A as immune potentiator for antibody production.

The development of new immune potentiators for human vaccines is an important and expanding field of research. In the present study, the ability of the capsular polysaccharide from Neisseria meningitidis serogroup A (CPS-A), a mannose-containing carbohydrate, to enhance the antibody production against a co-administered model vaccine antigen, is examined. A protein-meningococcal serogroup C capsular polysaccharide (CPS-C) conjugate was selected as the model antigen for this study. After subcutaneous immunization of Balb/C mice, the conjugate mixed with CPS-A induced higher anti-CPS-C IgG and IgG(2a) antibody levels and higher anti-meningococcal serogroup C bactericidal titers than the conjugate alone or mixed with CPS-C. The immuno-stimulatory properties exhibited by CPS-A and the fact that vaccines based on purified CPS-A has been safely used during decades to fight the serogroup A meningococcal disease, support the proposal to use CPS-A as immune potentiator for human vaccination studies.

Enzyme-linked immunosorbent assay for quantitative determination of capsular polysaccharide production in Streptococcus pneumoniae clinical isolates.

A simple, specific, sensitive and reproducible ELISA has been developed to quantify the level of CPS (capsular polysaccharide) production in supernatants of Streptococcus pneumoniae cell cultures. CPSs from Strep. pneumoniae have been widely used as vaccine antigens. The quantification method is based on two type-23F serotype-specific polyclonal antibodies: IgG, purified from sera of mice immunized with a pneumococcal type-23F CPS conjugate, used in the coating step, and a serotype-specific rabbit serum as the second antibody. Solutions of purified type-23F CPS were used as standards. The relationship between A(492) and type-23F CPS concentration was linear over the range 1-310 ng/ml (r=0.989), with 1 ng/ml as the lower limit of sensitivity. The specificity of ELISA was assessed because purified type-19F CPS and cell-wall polysaccharide samples were not detected after their evaluation by the ELISA described in the present study. Repeatability and intermediate precision of the assay were good, the coefficients of variation being 3 and 10% respectively. This ELISA allowed selection of an appropriate vaccine strain, for a natural polysaccharide vaccine, among several 23F pneumococcal clinical isolates and constituted a valuable analytical tool for Strep. pneumoniae fermentation and CPS purification follow-up.