In vitro lymphocyte stimulation by recombinant hepatitis B surface antigen: A tool to detect the persistence of cellular immunity after vaccination

Zika virus precursor membrane peptides induce immune response in peripheral blood mononuclear cells

Zika virus is a re-merging flavivirus allied to serious mental health conditions in the fetuses. There is currently no preventives or treatment available for Zika infection. In this work, we have extended the in silico analysis by performing the molecular docking of previous reported three conserved Zika virus precursor membrane (prM) peptides (MP1, MP2 and MP3) with HLA complex (pHLA) and T cell receptors (TCR) and also evaluated the peptide specific immune response in human peripheral blood mononuclear cells (PBMC). Most of the CD8+ and CD4+ T cell peptides-HLA complexes demonstrated good binding energies (ΔG) and HADDOCK scores in molecular docking analysis. Immunogenic response of peptides is measured as human peripheral blood mononuclear cell (PBMC) proliferation and interferon-gamma (IFN-γ) production using a 3-(4,5- dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay and a sandwich enzyme-linked immunosorbent assay (ELISA) respectively on ten different healthy blood samples. Peptide MP3 exhibited significant results in eight (cell proliferation) and seven (IFN-γ secretion) healthy volunteers' blood samples out of ten. Additionally, peptides MP1 and MP2 presented significant cell proliferation and IFN-γ release in six healthy blood samples. Thus, the outcomes from in silico and in vitro studies showed the immunogenic potential of peptides which need to validated in different experimental system before considering as candidate vaccine against Zika virus infection.

Conserved immunogenic peptides of Ebola glycoprotein elicit immune response in human peripheral blood mononuclear cells

In the past 45 years, ebolaviruses have periodically caused epidemics on the African continent. In December 2019, approval of a recombinant vector-based EBOV vaccine, named Ervebo, came as encouraging news; still, there is a long way to go in the development of an accessible, global, and pan-ebolavirus vaccine. The current study expanded our previous in silico work which was conducted on ebolavirus glycoprotein and this resulted in the identification of three potentially immunogenic peptides (P1 - FKRTSFFLWVIILFQRTFSIPL, P2 - LANETTQALQLF, and P3 - RATTELRTFSILNRKAIDF). An analysis to estimate the number of expected human leukocyte antigen (HLA) responders revealed that P1, P2, and P3 can potentially interact with 2540, 2150, and 2802 HLA alleles, respectively. Further, these peptides were subject to in vitro analysis wherein the human peripheral blood mononuclear cell proliferation and interferon-gamma (IFN-γ) production by peptide stimulated cells was studied in 10 healthy human blood samples with the help of a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay and a sandwich enzyme-linked immunosorbent assay (ELISA) respectively. P3 presented the best results, a significant (P < 0.05) peptide induced cell proliferation and IFN-γ stimulation for 8 and 10 samples, respectively, followed by P1 (5 and 6) and P2 (5 and 7). The in silico and in vitro results obtained in this study indicate the immunogenic potential of these peptides and warrant exploration of the effects on other cytokines as well as in vivo experimental validation.

A Prospective Study of Humoral and Cellular Immune Responses to Hepatitis B Vaccination in Habitual Marijuana Smokers

Exposure to Δ⁹-tetrahydrocannabinol (THC) in vitro and in animal models can significantly impair the differentiation, activation and function of dendritic cells, T cells and B cells. However, studies directly assessing the impact of marijuana smoking on human immunity are lacking. A prospective study of immune responses to a standard hepatitis B vaccination was therefore carried out in a matched cohort of 9 marijuana smokers (MS) and 9 nonsmokers (NS). In addition to their regular marijuana use, MS smoked four marijuana cigarettes in a monitored setting on the day of each vaccination. Blood samples were collected over time to assess the development of hepatitis B-specific immunity. The majority of subjects from both the NS (8) and MS (6) groups developed positive hepatitis B surface antibody titers (>10 IU/L) and of these 6 NS and 5 MS were classified as high antibody (good) responders (>100 IU/L). The development of a good response correlated with the presence of hepatitis B-specific T cell proliferation and cytokine production, resulting in a clear distinction regarding the immune status of good responders versus non-responders. However, even though there were slighter more non-responders in the MS cohort, there were no significant differences between MS and NS with respect to peripheral blood cell phenotypes or vaccination-related changes in hepatitis B responses. While a larger cohort may be required to rule out a small suppressive effect, our findings do not suggest that habitual marijuana smoking exerts a major impact on the development of systemic immunity to hepatitis B vaccination.

Immune responses to highly conserved influenza A virus matrix 1 peptides

Influenza vaccine development is considered to be complicated and challenging. Constantly evolving influenza viruses require continuous global monitoring and reformulation of the vaccine strains. Peptides that are conserved among different strains and subtypes of influenza A virus are strongly considered to be attractive targets for development of cross protective influenza vaccines that stimulate cellular responses. In this study, three highly conserved (>90%) matrix 1 peptides that contain multiple T cell epitopes, ILGFVFTLTVPSERGLQRRRF (P_M 1), LIRHENRMVLASTTAKA (P_M 2) and LQAYQKRMGVQMQR (P_M 3), were assessed for their immunogenic potential in vitro by subjecting peripheral blood mononuclear cells from healthy volunteers to repetitive stimulation with these chemically synthesised peptides and measuring their IFN-γ concentrations, proliferation by ELISA, and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay, respectively. Seven samples were screened for immunogenicity of P_M 1 and P_M 2, and six for that of P_M 3. All six samples had positive responses (IFN-γ secretion) to P_M 3 stimulation, as did five and three for P_M 2 and P_M 1 respectively. In contrast, seven (P_M 1 and P_M 2) and four (P_M 3) samples showed proliferative response as compared with unstimulated cells. The encouraging immunogenic response generated by these highly conserved matrix 1 peptides indicates they are prospective candidates for development of broadly reactive influenza vaccines.

Memory T cells specific for HBV enumerated by a peptide-based cultured enzyme-linked immunospot assay in healthy HBV-vaccinated subjects

Hepatitis B vaccine is the most effective strategy to control hepatitis B virus (HBV) infection and disease. It is considered that an anti-HBs (antibodies against HBV surface antigen) titer >10 mIU/ml, measured shortly after a complete vaccination schedule, provides protection against infection. Approximately 4-10% of healthy individuals fail to respond to 3-dose vaccination. Long-term HBV-specific memory T-cell response has not been fully investigated, mainly due to the lack of a suitable assay. We quantified HBV-specific expandable memory T cells by using a cultured IFN-γ enzyme-linked immunospot (ELISPOT) assay. Cultured ELISPOT response to an overlapping peptide pool representing the complete L (large) HBV envelope polypeptide was evaluated in 41 healthy subjects vaccinated 15-20 y earlier and 5 unvaccinated. Plasma samples were tested for anti-HBs. Vaccinated subjects had significantly higher HBV-specific T-cellular response than unvaccinated (p = 0.0002). HBV-specific T-cell response was mainly mediated by CD4⁺ T cells. No concordance was found between cultured ELISPOT and anti-HBs data in vaccinated subjects. Thirty-one (76%) vaccinated subjects were responders (anti-HBs >10 mIU/ml). Nineteen (46%) vaccinated subjects were considered to be responders in cultured ELISPOT. Twenty-two (54%) vaccinated subjects were considered non-responders in cultured ELISPOT; 5 of them (23%) were also humoral non-responders. About 12% of healthy HBV-vaccinated subjects are both humoral and cellular non-responders. Although the prognostic value of this assay has not been established in terms of predictability for susceptibility to de-novo HBV infection, ELISPOT data suggest that these subjects may be at risk for HBV infection and disease, especially health care workers.