Expression in Saccharomyces boulardii of recombinant Toxin-coregulated pilus A subunit (TcpA) of Vibrio cholerae O1

Cholera is endemic in over 50 countries with an estimated mortality of 100,000-120,000. Vaccination is considered the complementary key to prevent and control cholera; therefore, alternative vaccine preparations are needed. Toxin Co-regulated Pilus is part of the toxR virulence regulon, which is necessary for colonization in the intestinal mucosa. In order to express Vibrio cholerae TcpA protein in Saccharomyces boulardii, the expression plasmid pYES2 was constructed by inserting tcpA gene isolated from local Vibrio cholerae Eltor Inaba isolates. The new construct was transferred into Saccharomyces boulardii cells and the expression of tcpA gene was induced from the GAL1 promoter by adding galactose to the medium. The SDS-PAGE and Western blot analysis showed the presence of TcpA in yeast. These results showed that Saccharomyces boulardii is a promising host to express Vibrio cholerae toxin TcpA as the first step in attempt to produce an oral Vibrio cholerae vaccine(AU)

El cólera es endémico en más de 50 países. Se estima una mortalidad entre 100.000 - 120.000 debido a esta enfermedad. La vacunación se considera una medida complementaria para prevenir y controlar el cólera, por lo tanto, se necesitan preparaciones vacunales alternativas a las existentes. El Pili corregulado con la toxina, es parte del regulón de virulencia toxR, y es necesario para la colonización en la mucosa intestinal. Para expresar la proteína tcpA de Vibrio cholerae en Saccharomyces boulardii, se construyó el plásmido de expresión pYES2 insertando el gen tcpA obtenido a partir de aislamientos locales de Vibrio cholerae El Tor Inaba. La nueva construcción se transfirió a las células de Saccharomyces boulardii y se indujo la expresión del gen tcpA a partir del promotor GAL1 mediante la adición de galactosa al medio. El análisis mediante SDS-PAGE y Western blot demostró la presencia de TcpA en levaduras. Los resultados demostraron que Saccharomyces boulardii es un hospedero prometedor para expresar el gen tcpA de Vibrio cholerae como el primer paso en el intento de producir una vacuna oral contra Vibrio cholerae(AU)

Cholera: an overview with reference to the Yemen epidemic / 医学前沿

Cholera is a secretory diarrhoeal disease caused by infection with Vibrio cholerae, primarily the V. cholerae O1 El Tor biotype. There are approximately 2.9 million cases in 69 endemic countries annually, resulting in 95 000 deaths. Cholera is associated with poor infrastructure and lack of access to sanitation and clean drinking water. The current cholera epidemic in Yemen, linked to spread of V. cholerae O1 (Ogawa serotype), is associated with the ongoing war. This has devastated infrastructure and health services. The World Health Organization had estimated that 172 286 suspected cases arose between 27th April and 19th June 2017, including 1170 deaths. While there are three oral cholera vaccines prequalified by the World Health Organization, there are issues surrounding vaccination campaigns in conflict situations, exacerbated by external factors such as a global vaccine shortage. Major movements of people complicates surveillance and administration of double doses of vaccines. Cholera therapy mainly depends on rehydration, with use of antibiotics in more severe infections. Concerns have arisen about the rise of antibiotic resistance in cholera, due to mobile genetic elements. In this review, we give an overview of cholera epidemiology, virulence, antibiotic resistance, therapy and vaccines, in the light of the ongoing epidemic in Yemen.

Immunogenicity of a bivalent killed thimerosal-free oral cholera vaccine, Euvichol, in an animal model

PURPOSE: An oral cholera vaccine (OCV), Euvichol, with thimerosal (TM) as preservative, was prequalified by the World Health Organization (WHO) in 2015. In recent years, public health services and regulatory bodies recommended to eliminate TM in vaccines due to theoretical safety concerns. In this study, we examined whether TM-free Euvichol induces comparable immunogenicity to its TM-containing formulation in animal model. MATERIALS AND METHODS: To evaluate and compare the immunogenicity of the two variations of OCV, mice were immunized with TM-free or TM-containing Euvichol twice at 2-week interval by intranasal or oral route. One week after the last immunization, mice were challenged with Vibrio cholerae O1 and daily monitored to examine the protective immunity against cholera infection. In addition, serum samples were obtained from mice to measure vibriocidal activity and vaccine-specific IgG, IgM, and IgA antibodies using vibriocidal assay and enzyme-linked immunosorbent assay, respectively. RESULTS: No significant difference in immunogenicity, including vibriocidal activity and vaccine-specific IgG, IgM, and IgA in serum, was observed between mice groups administered with TM-free and -containing Euvichol, regardless of immunization route. However, intranasally immunized mice elicited higher levels of serum antibodies than those immunized via oral route. Moreover, intranasal immunization completely protected mice against V. cholerae challenge but not oral immunization. There was no significant difference in protection between two Euvichol variations. CONCLUSION: These results suggested that TM-free Euvichol could provide comparable immunogenicity to the WHO prequalified Euvichol containing TM as it was later confirmed in a clinical study. The pulmonary mouse cholera model can be considered useful to examine in vivo the potency of OCVs.

Yemen OCV risk assessment

The Ministry of Public Health and Population [MoHP], Yemen, WHO and other partners conducted assessment to determine risk profile of governorates and districts for occurrence and spread of cholera in order to prioritize the high risk districts for use of oral cholera vaccine [OCV] as a preventive measure for prevention and control of cholera

OCV risk assessment in Sudan

In October 2017, the Federal Ministry of Health, Sudan, in collaboration with WHO and other partners conducted as-sessment to determine risk profile of states and localities for occurrence and spread of cholera in order to prioritize localities and special high risk groups for use of oral cholera vaccine [OCV] for prevention of the outbreak

Implementation research: reactive mass vaccination with single-dose oral cholera vaccine, Zambia

Objective:To describe the implementation and feasibility of an innovative mass vaccination strategy ­ based on single-dose oral cholera vaccine ­ to curb a cholera epidemic in a large urban setting.Method:In April 2016, in the early stages of a cholera outbreak in Lusaka, Zambia, the health ministry collaborated with Médecins Sans Frontières and the World Health Organization in organizing a mass vaccination campaign, based on single-dose oral cholera vaccine. Over a period of 17 days, partners mobilized 1700 health ministry staff and community volunteers for community sensitization, social mobilization and vaccination activities in 10 townships. On each day, doses of vaccine were delivered to vaccination sites and administrative coverage was estimated.Findings:Overall, vaccination teams administered 424 100 doses of vaccine to an estimated target population of 578 043, resulting in an estimated administrative coverage of 73.4%. After the campaign, few cholera cases were reported and there was no evidence of the disease spreading within the vaccinated areas. The total cost of the campaign ­ 2.31 United States dollars (US$) per dose ­ included the relatively low cost of local delivery ­ US$ 0.41 per dose.Conclusion:We found that an early and large-scale targeted reactive campaign using a single-dose oral vaccine, organized in response to a cholera epidemic within a large city, to be feasible and appeared effective. While cholera vaccines remain in short supply, the maximization of the number of vaccines in response to a cholera epidemic, by the use of just one dose per member of an at-risk community, should be considered

Cholera Outbreak in Somalia

Somalia has been experiencing recurring outbreaks of cholera in the last few years. The current cholera outbreak started in November 2016 and is still ongoing. Since the beginning of the outbreak in early 2016, a cumulative total of 20 684 cases including 689 deaths have been reported so far [CFR=3.2%] from the country

Communications in public health emergencies

Recent experience with famine and cholera outbreak in Somalia has shown that communication, whether with affected communities, among public health response actors, or with the media, is a critical component of effective response to public health emergencies

Oral cholera vaccination in hard-to-reach communities, Lake Chilwa, Malawi

Objective To evaluate vaccination coverage, identify reasons for non-vaccination and assess satisfaction with two innovative strategies for distributing second doses in an oral cholera vaccine campaign in 2016 in Lake Chilwa, Malawi, in response to a cholera outbreak. Methods We performed a two-stage cluster survey. The population interviewed was divided in three strata according to the second-dose vaccine distribution strategy: (i) a standard strategy in 1477 individuals (68 clusters of 5 households) on the lake shores; (ii) a simplifiedcold-chain strategy in 1153 individuals (59 clusters of 5 households) on islands in the lake; and (iii) an out-of-cold-chain strategy in 295 fishermen (46 clusters of 5 to 15 fishermen) in floating homes, called zimboweras. Finding Vaccination coverage with at least one dose was 79.5% (1153/1451) on the lake shores, 99.3% (1098/1106) on the islands and 84.7% (200/236) on zimboweras. Coverage with two doses was 53.0% (769/1451), 91.1% (1010/1106) and 78.8% (186/236), in the three strata, respectively. The most common reason for non-vaccination was absence from home during the campaign. Most interviewees liked the novel distribution strategies. Conclusion Vaccination coverage on the shores of Lake Chilwa was moderately high and the innovative distribution strategies tailored to people living on the lake provided adequate coverage, even among hard-to-reach communities. Community engagement and simplified delivery procedures were critical for success. Off-label, out-of-cold-chain administration of oral cholera vaccine should be considered as an effective strategy for achieving high coverage in hard-to-reach communities. Nevertheless, coverage and effectiveness must be monitored over the short and long term

Epidemiology, management, and prevention of cholera

Cholera is an acute secretory form of diarrhea caused by a potent enterotoxin (cholera toxin) after ingestion of toxigenic Vibrio cholerae of the O1 or O139 serogroups. Although cholera is very common in Africa and Asia as a whole, the incidence of cholera has been very low in recent years in Korea. Dehydration and electrolyte abnormalities due to massive watery diarrhea can lead to death, and the mortality rates in untreated patients with severe cholera can exceed 70%. Effective rehydration therapy is the cornerstone of the management of patients with cholera and can reduce the mortality rate to less than 0.2%. Antibiotics reduce the volume and duration of diarrhea, but are recommended for patients with severe disease because of the rapid emergence and spread of multidrug-resistant V. cholerae across the globe. Two oral cholera vaccines are available, and the World Health Organization recommends that these oral vaccines be considered in integrated prevention programs in endemic countries at risk for outbreaks.

Use of single dose OCV: New strate-gies for cholera control

Recent evidence has emerged on the effectiveness of single dose of oral cholera vaccine for outbreak response. This finding has generated interest in the control of cholera outbreaks in the epidemic belt of the Eastern Mediterranean Region

Cholera in Yemen: cases rise

Cholera outbreak in Yemen continues while cases increase in recent time. As of date, a total of 7,730 suspected cases including 82 relate deaths have been reported since the outbreak began during the first week of October [epidemiological week no 34]

Cholera in Somalia: outbreak contained but sporadic cases continue

The cholera outbreak in Somalia which was reported at the beginning of the year is gradually tapering off despite slight increase in number of reported cases during epidemiological week from 45 to 47. As of 30 November 2016, a total of 14, 710 suspected cases including 497 related deaths [CFR: 3.51%] were reported from this outbreak so far

Cholera elimination in the Eastern Mediterranean Region

Cholera continued to threaten public health and claim lives in the countries of Eastern Mediterranean Region [EMR]. During this year, a total of 49,519 suspected cases of cholera including 12 related deaths [CFR: 0.02%] were officially reported to WHO by three Member States in the EMR

Development of oral cholera vaccine and its vaccination / 中华预防医学杂志

The application of the cholera vaccine is one of the cholera prevention and control strategies. Cholera vaccines stimulate mucosal immune to play the role of antibacteria and antitoxin. When the cholera toxin B subunit is added in the cholera vaccine, it could also defend against some diarrhea associated pathogens by cross-protection. Oral inactivated cholera vaccines are commercially available now. The oral live vaccine candidates are under development. The development of cholera vaccine is not only on the technical aspect, based on the situations of epidemic areas and population, cost, storage and transportation condition should also be considered. Though the argument on the use of cholera vaccine in epidemic areas and population in high risk existed previously, its vaccination has reached agreement now based on the clinical trials and evaluations during epidemic period.

Strategic framework for cholera control

A recent initiative to develop strategic framework for prevention and control of cholera in the Eastern Mediterranean Region [EMR] of WHO has been kicked off. The aim of this framework is to prevent and eliminate the risk of cholera from the region as an acute public health problem

Safety and Immunogenicity Assessment of an Oral Cholera Vaccine through Phase I Clinical Trial in Korea

The safety, tolerability and immunogenicity of an oral cholera vaccine (OCV) was assessed in adult Korean male through an open-label, non-comparative clinical study. Two doses of vaccine with an interval of 2 weeks were given to 20 healthy subjects. A total of 7 adverse events occurred in 6 subjects. However, no clinically significant change was observed in electrocardiograms, vital signs, physical examinations, and clinical laboratory tests. The immunogenicity of OCV was evaluated by serum vibriocidal assay where anti-Vibrio cholerae O1 and O139 antibodies were measured at day 0, 14, and 28 of vaccine administration. The antibody titers ranged from < 2.5-5,120 for V. cholerae O1 Inaba, < 2.5-10,240 for V. cholerae O1 Ogawa and < 2.5-480 for V. cholerae O139. In addition, the fold increase in antibody titers ranged from 1-4,096 for O1 Inaba, 1-8,192 for O1 Ogawa, and 1-384 for O139. The seroconversion rate was 95% and 45% for O1 and O139 antibodies, respectively. Our study clearly shows that administration of two doses of OCV at a 2 week-interval increases an appropriate level of antibody titer in the serum of healthy Korean adult males (Clinical Trial Number, NCT01707537).

Cholera in Somalia: Is the use of OCVs feasible

In 2011, Somalia reported 68,424 cases of acute watery diarrhea including 1,099 related deaths. Some cases were laboratory confirmed as Vibrio cholera 01 serotype Inaba. Majority of the cases [73%] were reported in the under 5 year age group. Of the total reported deaths, over 65% [713/1099] were also in the under 5 year age group. Given this situation in Somalia, considerations for the use of Oral Cholera Vaccines [OCVs] in one of the cholera endemic areas of Somalia are being discussed despite the operational and logistic challenges in organizing a mass vaccination campaign in a complex and humanitarian emergency situation