Apudocytes in experimental cholera vaccination

The morphofunctional state of apudocytes in the gastrointestinal tract and immunocompetent organs (spleen, mesenteric lymph nodes) of mice immunized with chemical bivalent cholera vaccine was studied. The study revealed that the APUD system of the intestine and the argyrophil elements of the immunocompetent organs of white mice gave a response to the oral administration of commercial cholera vaccine. The reaction of the APUD system of the gastrointestinal tract was manifested by a significant increase in the number of apudocytes and their greater synthesizing activity in the immunized animals during the period of maximum immunological transformation of the macroorganism. The immunization of mice with Vibrio cholerae facilitated the maintenance of homeostasis in the macroorganism and prevented appearance of morphological disturbances in its organs and system after subsequent challenge with V. cholerae.     

The determination of the optimal inoculation dose of an oral cholera chemical bivalent vaccine in a controlled experiment

276 volunteers aged 19 years and over were placed under observation in the course of the trial of oral cholera vaccine in tablets, containing choleragen toxoid, O-antigens of serovars Inaba and Ogawa and a number of Vibrio cholerae exoenzymes, for safety, reactogenic properties and immunological effectiveness. The vaccine was found to produce no reactions in a dose of 1-4 tablets; the administration of 3 tablets (300,000 binding units of the toxoid and 10,000 units of O-antigens, serovars Inaba and Ogawa) was shown to induce the most intensive synthesis of both antitoxins and vibriocidal antibodies in the blood sera of volunteers, as well as IgA coproantibodies. The oral vaccine was found to have an advantage over parenteral vaccines due to the absence of reactogenic properties and the formation of local immunity: coproantibodies appeared in 80% and 9% of the vaccinees respectively.     

An experimental study of the safety of a chemical monovalent tableted cholera vaccine in enteral administration]

The safety of experimental chemical cholera monovalent vaccine in tablets, produced by the institute "Microbe" (Saratov, USSR), has been studied. The study has shown that the vaccine, administered to adult rabbits and germ-free suckling rabbits by the enteral route, retains residual toxicity, mainly due to the presence of O-antigen. One or two administrations of 1-2 human doses of this preparation to adult rabbits induce minimal structural changes admissible from the viewpoint of safety. After immunization made in two administrations immunobiological transformation develops more rapidly and is more pronounced than after immunization in a single administration.     

The role of vaccine coverage within social networks in cholera vaccine efficacy

Background

Traditional vaccine trial methods have an underlying assumption that the effect of a vaccine is the same throughout the trial area. There are, however, many spatial and behavioral factors that alter the rates of contact among infectious and susceptible individuals and result in different efficacies across a population. We reanalyzed data from a field trial in Bangladesh to ascertain whether there is evidence of indirect protection from cholera vaccines when vaccination rates are high in an individual''s social network.

Methods

We analyzed the first year of surveillance data from a placebo-controlled trial of B subunit-killed whole-cell and killed whole-cell-only oral cholera vaccines in children and adult women in Bangladesh. We calculated whether there was an inverse trend for the relation between the level of vaccine coverage in an individual''s social network and the incidence of cholera in individual vaccine recipients or placebo recipients after controlling for potential confounding variables.

Results

Using bari-level social network ties, we found incidence rates of cholera among placebo recipients were inversely related to levels of vaccine coverage (5.28 cases per 1000 in the lowest quintile vs 3.27 cases per 1000 in the highest quintile; p = 0.037 for trend). Receipt of vaccine by an individual and the level of vaccine coverage of the individual''s social network were independently related to a reduced risk of cholera.

Conclusions

Findings indicate that progressively higher levels of vaccine coverage in bari-level social networks can lead to increasing levels of indirect protection of non-vaccinated individuals and could also lead to progressively higher levels of total protection of vaccine recipients.     

Choleragen-anatoxin chemical cholera vaccine enriched with Ogawa O-antigen

The cultural fluid of Vibrio cholerae strains of serovar Ogawa, grown under the conditions of submerged cultivation, has been shown to contain a large amount of soluble O-antigen which sharply differs from all other concomitant components in its molecular weight. By enriching the commercial chemical cholera vaccine known as Choleragen Toxoid with purified Ogawa O-antigen a new preparation, consisting mainly of cholera toxoid and Ogawa and Inaba O-antigens and capable of producing pronounced immunity to V. cholerae of both serovars, has been obtained.     

Progress towards development of a cholera subunit vaccine

Cholera, an enteric disease that can reach pandemic proportions, remains a world-wide problem that is positioned to increase in incidence as changes in global climate or armed conflict spawn the conditions that enhance transmission to humans and, thus, precipitate epidemic cholera. An effective subunit cholera vaccine that can provide protective immunity with one parenteral immunization would be a major advantage over the existing oral vaccines that can require two doses for optimal protection. The existing vaccines are clearly effective in some settings, but are less so in others, especially with respect to specific groups such as young (2-5 years) children. In our efforts to develop a cholera subunit vaccine, we focused on two Vibrio cholerae antigens, LPS (lipopolysaccharide) and TCP (toxin co-regulated pilus), that are known to induce protective antibodies in animal models and, in the case of anti-LPS antibodies, to be associated with clinical protection of V. cholerae exposed or vaccinated individuals. This review discusses the current cholera vaccines and compares the advantages of a cholera subunit vaccine to that of the whole cell vaccines. We discuss the possible subunit antigens and prospective targeted use of a subunit cholera vaccine.     

Targeted vaccine adjuvants based on modified cholera toxin

The present review describes immunomodulation with targeted adjuvants that will allow for the development of efficacious mucosal vaccines. We have studied cholera toxin (CT) and derivatives thereof, to rationally design vaccine adjuvant vectors that are both highly efficacious as well as safe and non-toxic. Two strategies were exploited; the first using CT or the enzymatically inactive receptor-binding B-subunit of CT (CTB) and the second, using CTA1 or an enzymatically inactive mutant CTA1R7K., that was linked, in a fusion protein, to the B-cell targeting moiety, DD, from Staphylococcus areus proteinA. Our studies provide compelling evidence that delivery of Ag in the absence of ADP-ribosylation can promote tolerance, whereas, ADP-ribosyltransferase-active conjugates, prevent tolerance but induce IgA immunity. Our analysis revealed unique subsets of mucosal and systemic DC that appeared to be responsible for the ADP-ribosyltransferase sensitive dichotomy between tolerance and IgA immunity. Whether targeting of B cells suffice for tolerance-induction or requires participation of DCs, is at present an unresolved issue. Nevertheless, enzymatic modulation differentiates and matures the DC to promote CD4 T cell help for IgA B cell development. Ag-presentation in the absence of enzyme, as seen with CTA1R7K-DD, expands specific T cells to a similar extent as enzymatically active CTA1-DD, but fails to recruit help for germinal center expansion of activated B cells. We have given special attention to the genes that adjuvants turn on using Affymetrix technology. In particular, modulation of the expression of co-stimulatory molecules on the targeted APC; CD80, CD86, CD83 and B7RP-1, play important roles for the effect of the ADP-ribosylating CTA1-based adjuvants for the development of tolerance or active IgA immunity.     

霍乱疫苗中残余霍乱毒素检测方法的建立及验证

采用间接酶联免疫法,即用神经节苷脂包被,加入待检样品,再加入兔抗霍乱毒素B亚单位抗体,用标准样品的吸光值(A值)对标准样品的浓度绘制4-参数拟合曲线,根据标准曲线计算出待测样品中的CT浓度。结果显示,在浓度范围(0.6～16)ng/ml之间,CT标准浓度和检测浓度成线性关系,r2=0.9986。精确度在浓度范围(0.6～16)ng/ml,CT的平均回收率在96.24%～114.44%之间。精密度:批内变异CV%≤12.98%,批间变异CV%≤18.48%。特异性CT浓度在10ng/ml时,平均回收率为102.6%;CT浓度在5ng/ml时,平均回收率为111.17%;CT浓度在2.5ng/ml时,平均回收率为123.83%。实验表明该方法可检测霍乱疫苗原液中CT的含量。     

Excretion of cholera toxin from Escherichia coli: a potential oral vaccine for cholera

Escherichia coli strain N100 has been mutagenized by transposon mutagenesis and mutants with a cell surface leaky phenotype have been isolated. The mutant designated as E. coli N100::Tn5 excreted periplasmic proteins like ribonuclease and alkaline phosphatase. When this mutant strain was transformed with plasmids containing cloned cholera toxin genes, the toxin protein synthesized in the cells were excreted. The potentiality of this strain as a live oral vaccine for cholera has been discussed.