SARS-CoV spike protein-expressing recombinant vaccinia virus efficiently induces neutralizing antibodies in rabbits pre-immunized with vaccinia virus

A vaccine for severe acute respiratory syndrome (SARS) is being intensively pursued against its re-emergence. We generated a SARS coronavirus (SARS-CoV) spike protein-expressing recombinant vaccinia virus (RVV-S) using highly attenuated strain LC16m8. Intradermal administration of RVV-S into rabbits induced neutralizing (NT) antibodies against SARS-CoV 1 week after administration and the NT titer reached 1:1000 after boost immunization with RVV-S. Significantly, NT antibodies against SARS-CoV were induced by administration of RVV-S to rabbits that had been pre-immunized with LC16m8. RVV-S can induce NT antibodies against SARS-CoV despite the presence of NT antibodies against VV. These results suggest that RVV-S may be a powerful SARS vaccine, including in patients previously immunized with the smallpox vaccine.     

Plant-derived measles virus hemagglutinin protein induces neutralizing antibodies in mice

Measles remains a significant problem in both the developed and developing world, and new measles vaccination strategies need to be developed. This paper examines the strategy of utilizing transgenic plants expressing a measles antigen for the development of an oral sub-unit measles vaccine. A 1.8 kb fragment encompassing the coding region of the measles virus hemagglutinin (H) protein was cloned into a plant expression cassette. Three different expression constructs were tested: pBinH (H gene alone), pBinH/KDEL (addition of a C-terminal endoplasmic reticulum-retention sequence SEKDEL) and pBinSP/H/KDEL (further addition of an authentic N-terminal plant signal peptide). The highest levels of recombinant H protein production were observed in plants transformed with pBinH/KDEL. Mice inoculated intraperitoneally with transgenic plant derived recombinant H protein produced serum anti-H protein antibodies that neutralized the measles virus (MV) in vitro. Mice gavaged with transgenic tobacco leaf extracts also developed serum H protein-specific antibodies with neutralizing activity against MV in vitro. These results indicate that the plant-derived measles H protein is immunogenic when administered orally and that, with further development, oral vaccination utilizing transgenic plants may become a viable approach to measles vaccine development.     

Crossreactive neutralizing antibodies induced by immunization with caprine arthritis-encephalitis virus surface glycoprotein

Four Saanen goats were immunized with affinity purified gp135 surface glycoprotein (SU) of caprine arthritis-encephalitis virus isolate 79-63 (CAEV-63) and evaluated for homologous and crossreactive serum neutralizing antibodies. CAEV-63 neutralizing antibodies were detected in all goats after seven immunizations with SU in Quil A adjuvant. Sera from three goats neutralized an independent CAEV isolate (CAEV-Co). However, serum from one goat did not detectably neutralize heterologous CAEV-Co and inhibited CAEV-Co neutralization by another serum.     

非结构蛋白1抗原捕获酶联免疫吸附法评价登革病毒抗体中和活性

目的 在获得具有中和活性的针对Ⅰ型登革病毒(dengue virus serotype Ⅰ,DENV-1)的抗体基础上,评价已建立的非结构蛋白1(nonstructural protein 1,NSI)抗原捕获酶联免疫吸附法(enzyme-linked immunosorbent assay,ELISA)分析抗体中和活性的可行性,为中和抗体的筛选和疫苗效果的评价提供一个更为快速、简便的检测方法.方法 使用重组DENV-1包膜蛋白Ⅲ区(envelopeprotein domainⅢ,EDⅢ)免疫5只BALB/c小鼠制备单克隆抗体(简称单抗),采用间接ELISA、间接免疫荧光法(immunofluorescenee assay,IFA)和免疫印迹法(Western Blot)对单抗进行筛选及鉴定;同时用该重组蛋白免疫1只新西兰兔,制备多克隆抗体血清;以传统噬斑减少中和试验(plaquereduction neutralization test,PRNT)作为参比方法,采用NSI抗原捕获ELISA对所获抗体进行中和活性检测.结果 获得4株针对DENV-1 EDⅢ单抗和1份兔多抗血清,且被PRNT试验证明均具有中和活性,四株单抗腹水(1A1、1B3、3D3、9D6)和兔多抗血清中和效价分别为1:1024、1:512、1:256、1:4096和1:4096.使用NS1抗原捕获ELISA法检测不到PRNT中和效价最低的3D3抗体对DENV-1有中和能力,而检测其余3株单抗(1A1、1B3、9D6)和多抗兔血清中和效价均远低于PRNT测定结果,分别为1:32、1:32、1:128和1:128.结论 简单、快速的NS1抗原捕获ELISA可用于评价DENV抗体的中和活性,该方法适合于高效价中和抗体的筛选,有望成为评价疫苗效果的方法之一.     

Targeting of envelope domain III protein of DENV type 2 to DEC-205 receptor elicits neutralizing antibodies in mice

Dengue virus (DENV) is the causal agent of severe disease and, in some cases, mortality in humans, but no licensed vaccines against dengue are available. An effective vaccine against dengue requires long-term humoral and cellular immune responses. Several viral proteins have been the subjects of intense research, especially the envelope (E) protein, aimed at developing a vaccine. Domain III of the envelope protein (EDIII) has been identified as a potential candidate because it is involved in binding to host cell receptors and contains epitopes that elicit virus neutralizing antibodies. However, this domain is not sufficiently antigenic when is expressed and administered as antigen to elicit a strong immune response. One alternative to enhance immunogenicity is to target the antigen to dendritic cells to induce T-cells for broad antibody responses. In this work, a single chain antibody fragment (scFv) raised against the DEC-205 receptor fused with the EDIII was successfully expressed in Nicotiana benthamiana. The recombinant protein was expressed and purified from the plant and evaluated in BALB/c mice to test its immunogenicity and ability to induce neutralizing antibodies against DENV. The mice immunized with the recombinant protein produced specific and strong humoral immune responses to DENV. Only two immunizations were required to generate a memory response to DENV without the presence of adjuvants. Also, recognition of the recombinant protein with sera from DENV-infected patients was observed. These findings suggest that this strategy has potential for development of an effective vaccine against DENV.     

The immune response to infection with vaccinia virus in mice. I. Infection and the production of antibody neutralizing cell-associated and cell-free virus.

The onset, duration and magnitude of antibody responses to a poxvirus infection were examined. Mice were inoculated intravenously with the WR strain of vaccinia virus and developed pocks on their tails. The number of pocks was related to the size of the inoculum. Virus was detectable in the spleen and infected mice were subsequently immune to intravenous and intra-nasal challenge. Sera of infected animals neutralized both cell-free and cell-associated virus. Antibody against cell-free virus appeared first; maximum titres were reached sooner but were lower than those of antibody neutralizing cell-associated virus. Titres remained high for at least 100 days after infection.     

Disabling complement regulatory activities of vaccinia virus complement control protein reduces vaccinia virus pathogenicity

Poxviruses encode a repertoire of immunomodulatory proteins to thwart the host immune system. One among this array is a homolog of the host complement regulatory proteins that is conserved in various poxviruses including vaccinia (VACV) and variola. The vaccinia virus complement control protein (VCP), which inhibits complement by decaying the classical pathway C3-convertase (decay-accelerating activity), and by supporting inactivation of C3b and C4b by serine protease factor I (cofactor activity), was shown to play a role in viral pathogenesis. However, the role its individual complement regulatory activities impart in pathogenesis, have not yet been elucidated. Here, we have generated monoclonal antibodies (mAbs) that block the VCP functions and utilized them to evaluate the relative contribution of complement regulatory activities of VCP in viral pathogenesis by employing a rabbit intradermal model for VACV infection. Targeting VCP by mAbs that inhibited the decay-accelerating activity as well as cofactor activity of VCP or primarily the cofactor activity of VCP, by injecting them at the site of infection, significantly reduced VACV lesion size. This reduction however was not pronounced when VCP was targeted by a mAb that inhibited only the decay-accelerating activity. Further, the reduction in lesion size by mAbs was reversed when host complement was depleted by injecting cobra venom factor. Thus, our results suggest that targeting VCP by antibodies reduces VACV pathogenicity and that principally the cofactor activity of VCP appears to contribute to the virulence.     

Adsorption of recombinant poxvirus L1-protein to aluminum hydroxide/CpG vaccine adjuvants enhances immune responses and protection of mice from vaccinia virus challenge

The stockpiling of live vaccinia virus vaccines has enhanced biopreparedness against the intentional or accidental release of smallpox. Ongoing research on future generation smallpox vaccines is providing key insights into protective immune responses as well as important information about subunit-vaccine design strategies. For protein-based recombinant subunit vaccines, the formulation and stability of candidate antigens with different adjuvants are important factors to consider for vaccine design. In this work, a non-tagged secreted L1-protein, a target antigen on mature virus, was expressed using recombinant baculovirus technology and purified. To identify optimal formulation conditions for L1, a series of biophysical studies was performed over a range of pH and temperature conditions. The overall physical stability profile was summarized in an empirical phase diagram. Another critical question to address for development of an adjuvanted vaccine was if immunogenicity and protection could be affected by the interactions and binding of L1 to aluminum salts (Alhydrogel) with and without a second adjuvant, CpG. We thus designed a series of vaccine formulations with different binding interactions between the L1 and the two adjuvants, and then performed a series of vaccination-challenge experiments in mice including measurement of antibody responses and post-challenge weight loss and survival. We found that better humoral responses and protection were conferred with vaccine formulations when the L1-protein was adsorbed to Alhydrogel. These data demonstrate that designing vaccine formulation conditions to maximize antigen–adjuvant interactions is a key factor in smallpox subunit-vaccine immunogenicity and protection.     

Protective efficacy of neutralizing antibodies against Ebola virus infection

Ebola virus causes lethal hemorrhagic fever in humans and nonhuman primates, but no effective antiviral compounds are available for the treatment of this infection. The surface glycoprotein (GP) of Ebola virus is an important target of neutralizing antibodies. Although passive transfer of GP-specific antibodies has been evaluated in mouse and guinea pig models, protection was achieved only by treatment shortly before or after virus challenge. Using these animal models, we evaluated the protective efficacy of two monoclonal antibodies whose epitopes are distinct from those of the antibodies tested by others. Treatment of mice with these antibodies 2 days after challenge completely protected most of the animals; even treatment 3 or 4 days after challenge was partially effective. Although antibody treatment in the guinea pig model was not as effective as in the mouse model, single-dose treatment of guinea pigs 1 day before, or 1 or 2 days after challenge did protect some animals. Interestingly, the protective effects seen in these animal models did not correlate with the in vitro neutralizing activity of the antibodies, suggesting different mechanisms of the neutralization by these antibodies. These results underscore the potential therapeutic utility of monoclonal antibodies for postexposure treatment of Ebola virus infections.     

An ELISA for putative neutralizing antibodies to hepatitis E virus detects antibodies to genotypes 1, 2, 3, and 4

Two monoclonal antibodies that neutralize hepatitis E virus (HEV) were used to identify a subregion of ORF2 capsid protein spanning amino acids 459-607 as the shortest peptide to form the corresponding neutralization epitopes. An enzyme-linked immunosorbent assay (ELISA) based on a purified recombinant protein covering amino acids 458-607 in ORF2 of the Sar-55 strain (genotype 1) efficiently detected anti-HEV in non-human primates which had been experimentally infected with the four known mammalian genotypes of HEV, respectively. However, anti-HEV in these animals did not react with a shorter ORF2 peptide spanning amino acids 475-607. The ELISA was highly specific and sensitive when human or non-human primate sera were tested in parallel with a previously established ELISA based on amino acids 112-607 in ORF2. The antibody titer to peptides 458-607 in two ORF2-vaccinated rhesus monkeys which had different HEV challenge outcomes differed at the time of challenge. Since the ELISA appeared to be specific for neutralizing antibodies against HEV, it should be especially useful for quantifying the humoral immune response in hepatitis E vaccine trials.     

The prevalence of serum neutralizing antibodies to infectious bovine rhinotracheitis virus in Scotland

The prevalence of serum neutralizing antibodies to infectious bovine rhinotracheitis virus in 1152 serum samples from adult cattle in 114 dairy and beef herds in different regions of Scotland was 12%. In the Grampian region, the number of seropositive cattle in the self-contained herds was significantly less (P less than 0.01) than in the "other" herds. Holstein cattle had been introduced into five of these "other" herds, and significantly more (P less than 0.01) of the samples from these five herds were seropositive compared with the samples from the rest of the "other" herds in the same region into which recently purchased cattle had been introduced. The introduction of Holstein cattle was also a major factor in the association between the prevalence of antibodies and herd size in the Grampian region. The prevalence of serum neutralizing antibodies to infectious bovine rhinotracheitis virus was significantly greater (P less than 0.001) in this survey than in those previously undertaken in the United Kingdom.     

Recombinant measles virus encoding the spike protein of SARS-CoV-2 efficiently induces Th1 responses and neutralizing antibodies that block SARS-CoV-2 variants

Owing to the rapid spread of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and its variants, the development of effective and safe vaccines has become a priority. The measles virus (MeV) vaccine is an attractive vaccine platform as it has been administered to children for more than 40 years in over 100 countries. In this study, we developed a recombinant MeV expressing the full-length SARS-CoV-2 spike protein (rMeV-S) and tested its efficacy using mouse and hamster models. In hCD46Tg mice, two-dose rMeV-S vaccination induced higher Th1 secretion and humoral responses than one-dose vaccination. Interestingly, neutralizing antibodies induced by one-dose and two-dose rMeV-S immunization effectively blocked the entry of the α, β, γ, and δ variants of SARS-CoV-2. Furthermore, two-dose rMeV-S immunization provided complete protection against SARS-CoV-2 in the hamster model. These results suggest the potential of rMeV-S as a vaccine candidate for targeting SARS-CoV-2 and its variants.     

The prevalence of serum neutralizing antibodies to infectious bovine rhinotracheitis virus in Scotland.

The prevalence of serum neutralizing antibodies to infectious bovine rhinotracheitis virus in 1152 serum samples from adult cattle in 114 dairy and beef herds in different regions of Scotland was 12%. In the Grampian region, the number of seropositive cattle in the self-contained herds was significantly less (P less than 0.01) than in the "other" herds. Holstein cattle had been introduced into five of these "other" herds, and significantly more (P less than 0.01) of the samples from these five herds were seropositive compared with the samples from the rest of the "other" herds in the same region into which recently purchased cattle had been introduced. The introduction of Holstein cattle was also a major factor in the association between the prevalence of antibodies and herd size in the Grampian region. The prevalence of serum neutralizing antibodies to infectious bovine rhinotracheitis virus was significantly greater (P less than 0.001) in this survey than in those previously undertaken in the United Kingdom.     

Seroprevalence of neutralizing antibodies to measles virus in a vaccinated population in Iran, 1998

Measles is an acute highly infectious viral disease. Although live attenuated vaccine is used throughout the world, outbreaks of disease still occur in many countries including Iran. In this cross-sectional study, by implementing a viral neutralization test and cell culture techniques, the seroprevalence of neutralizing anti-measles antibodies was assessed. Three hundred and fifty-four blood samples were collected and random-cluster classified from healthy subjects 6 months to 16 years old, residing in the town of Khodabandeh and its rural areas. Of the total subjects, 174 (49.2%) were girls and 180 (50.8%) were boys. From 354 subjects studied, 310 (87.6%) had neutralizing anti-measles antibody titer of 1:8 or higher and were considered to be immune and 44 (12.4%) had lower antibody titers. At the time of specimen collection, information with regards to age, sex, history of vaccination and place of residence were collected. ² statistical test demonstrated a significant association between immune status and grouped age at the time of first vaccination (p < 0.009). The proportion test indicated significant differences in rate of seropositivity in paired age groups (3–8 vs. 9–11 and 9–11 vs. 12–64 months) (p < 0.02). The use of reliable techniques for assessing success of vaccination programs and performing seroepidemiological studies in order to organize national programs of control and eradication of measles are necessary.