Response of Volta children to live attenuated measles virus vaccine

Experience so far with the Enders B-level Edmonston strain of live attenuated measles vaccine has been principally with children in the USA in whom natural measles carries a low mortality. Measles is associated with an appreciably higher mortality rate in developing countries; in Upper Volta, climate, nutritional status, degree of parasitic infestation and concurrent infections may contribute to this. The present report summarizes a pilot study in Ouagadougou, Upper Volta, designed to obtain information on the response of Volta children to Enders vaccine and to determine the feasibility of using this vaccine on a large scale.     

Experience with live rubella virus vaccine combined with live vaccines against measles and mumps

Vaccination of pre-school children in the 1-7-years age-group for the specific prophylaxis of mumps and rubella is often difficult to arrange because of the already large number of inoculations given to these children. Combined vaccines to protect against measles, mumps and rubella should therefore be a valuable development. The existence of effective live vaccines for each of these 3 diseases makes possible the production of a single preparation suitable for subcutaneous inoculation.     

Alpha-C-galactosylceramide as an adjuvant for a live attenuated influenza virus vaccine

There is a substantial need to develop better influenza virus vaccines that can protect populations that are not adequately protected by the currently licensed vaccines. While live attenuated influenza virus vaccines induce superior immune responses compared to inactivated vaccines, the manufacturing process of both types of influenza virus vaccines is time consuming and may not be adequate during a pandemic. Adjuvants would be particularly useful if they could enhance the immune response to live attenuated influenza virus vaccines so that the amount of vaccine needed for a protective dose could be reduced. The glycolipid, alpha-galactosylceramide (alpha-GalCer), has recently been shown to have adjuvant activity for both inactivated and replicating recombinant vaccines. The goal of these experiments was to determine whether a derivative of alpha-GalCer, alpha-C-galactosylceramide (alpha-C-GalCer) can enhance the immune response elicited by a live attenuated influenza virus vaccine containing an NS1 protein truncation and reduce the amount of vaccine required to provide protection after challenge. Our results indicated that the adjuvant reduced both morbidity and mortality in BALB/c mice after challenge with wild type influenza virus. The adjuvant also increased the amount of influenza virus specific total IgG, IgG1, and IgG2a antibodies as well as IFN-γ secreting CD8⁺ T cells. By using knockout mice that are not able to generate NKT cells, we were able to demonstrate that the mechanism of adjuvant activity is dependent on NKT cells. Thus, our data indicate that stimulators of NKT cells represent a new avenue of adjuvants to pursue for live attenuated virus vaccines.     

Development and characterization of a live attenuated influenza B virus vaccine candidate

A human influenza B/Lee/40 virus was cold-adapted by serial passages in embryonated chicken eggs, at progressively lower temperatures, for possible use as a future influenza B vaccine donor strain. Temperature sensitive and cold-adapted phenotypes were achieved as a consequence of the adaptation process. It was determined that the virus was attenuated in mice since the replication of the viral genome was significantly reduced in the lung. Despite decreased viral replication, the attenuated infection effectively induced a virus-specific immune response. We next developed a reassortant virus carrying two major surface proteins, hemagglutinin and neuraminidase from virulent B/Shangdong/7/97 and six internal genes from the cold-adapted B/Lee/40. The reassortant virus was also attenuated and protected mice from lethal challenge with wild type B/Shangdong/7/97. In addition, vaccination with the reassortant virus resulted in a specific antibody response and inhibited the replication of wild type virus in mice. We conclude that the cold-adapted B/Lee/40 donor strain merits further investigation as potential live vaccine carrier as an alternative means for protection from influenza B virus epidemics.     

Generation of a recombinant Oka varicella vaccine expressing mumps virus hemagglutinin-neuraminidase protein as a polyvalent live vaccine

We constructed a recombinant varicella-zoster virus (VZV) Oka vaccine strain (vOka) that contained the mumps virus (MuV) hemagglutinin-neuraminidase (HN) gene, inserted into the site of the ORF 13 gene by using the bacterial artificial chromosome (BAC) system in Escherichia coli. Insertion of the HN gene into the VZV genome was confirmed by PCR and Southern blot. The infectious virus reconstituted from the vOka-HN genome (rvOka-HN) had a growth curve similar to the original recombinant vOka without the HN gene. The mumps virus HN protein expressed in rvOka-HN infected cells was expressed diffusely in the cytoplasm, and modification of the protein was similar to that seen in MuV-infected cells. Electron microscopic examination of infected cells revealed that HN was expressed on the plasma membrane of the cells but not in the viral envelope, suggesting that the tropism of rvOka-HN would be unchanged from that of the original vOka strain. Immunization of guinea pigs with rvOka-HN-induced VZV- and HN-specific antibodies. Interestingly, the induced antibodies had a strong neutralizing activity against virus-cell infections of both MuV and VZV. Therefore, the novel varicella vaccine expressing MuV HN protein is suitable as a polyvalent live attenuated vaccine against VZV and MuV infections.     

Development of a live attenuated duck hepatitis A virus type 3 vaccine (strain SD70)

Duck hepatitis A virus type 3 (DHAV-3) is an important pathogen that causes substantial losses in the Chinese duck industry. DHAV-3 is highly fatal to ducklings and there is no licensed vaccine in China available to reduce DHAV-3 infection. Our goal was to develop a live attenuated vaccine candidate against DHAV-3. A field isolated strain, SD, was attenuated by serially passaging in specific-pathogen-free (SPF) chicken embryos, and it lost its pathogenicity after 40 passages. The 70th passaged strain (SD70), which achieved good growth capacity in chicken embryos with a viral titer of 10^7.5 ELD₅₀/mL, was chosen to be the live attenuated vaccine candidate. The SD70 strain did not cause clinical signs of disease or mortality in 1-day-old ducklings and showed no virulence reversion after seven rounds of in vivo back passages. The minimum effective dose of SD70 was determined to be 10^2.5 ELD₅₀ via the vaccination route of subcutaneous inoculation. A single dose of the SD70 provided good protection to susceptible ducklings against the lethal DHAV-3 strain. Compared with the genomic sequence of the parent SD strain, the SD70 had 12 amino acid substitutions, some of which may play a role in virulence attenuation. This study demonstrated that the attenuated SD70 strain is a promising vaccine candidate for the prevention of DHAV-3 infection in China. It exhibited safety, good stability and excellent protection.     

Characterization of West Nile virus live vaccine candidates attenuated by capsid deletion mutations

Protein C deletion mutants of West Nile virus (WNV) were evaluated for their potential use as live virus vaccine candidates in vivo. Double and triple mutants carrying small deletions and second-site point mutations, as well as mutants with large deletions of 36 and 37 amino acid residues were tested in a stringent mouse challenge model. The mutant viruses were found to be non-pathogenic and to induce protective immunity in a wide range of inoculation doses (10¹–10⁶ FFU). Furthermore, the effects of combining three different previously identified resuscitating point mutations, as well as the combination of a large protein C deletion with a deletion mutation in the 3′ non-coding region were studied. The data indicate that the production of safe and efficacious WNV live vaccines based on protein C deletion mutations is feasible.     

Efficacy of seasonal live attenuated influenza vaccine against virus replication and transmission of a pandemic 2009 H1N1 virus in ferrets

In March 2009, a swine origin influenza A (2009 H1N1) virus was introduced into the human population and quickly spread from North America to multiple continents. Human serologic studies suggest that seasonal influenza virus vaccination or infection would provide little cross-reactive serologic immunity to the pandemic 2009 H1N1 virus. However, the efficacy of seasonal influenza infection or vaccination against 2009 H1N1 virus replication and transmission has not been adequately evaluated in vivo. Here, ferrets received one or two doses of the US licensed 2008-2009 live attenuated influenza vaccine (LAIV) intranasally. An additional group of ferrets were inoculated with the A/Brisbane/59/07 (H1N1) virus to model immunity induced by seasonal influenza virus infection. All vaccinated and infected animals possessed high titer homologous hemagglutination-inhibition (HI) and neutralizing antibodies, with no demonstrable cross-reactive antibodies against 2009 H1N1 virus. However, in comparison to non-immune controls, immunized ferrets challenged with pandemic A/Mexico/4482/09 virus displayed a significant reduction in body temperature and virus shedding. The impact of single-dose LAIV inoculation on 2009 H1N1 disease and virus transmission was also measured in vaccinated ferrets that were challenged with pandemic A/Netherlands/1132/09 virus. Although a single dose of LAIV reduced virus shedding and the frequency of transmission following homologous seasonal virus challenge, it failed to reduce respiratory droplet transmission of 2009 H1N1 virus. The results demonstrate that prior immunization with seasonal LAIV or H1N1 virus infection provides some cross-protection against the 2009 H1N1 virus, but had no significant effect on the transmission efficiency of the 2009 H1N1 virus.     

Yellow fever live attenuated vaccine: A very successful live attenuated vaccine but still we have problems controlling the disease

Yellow fever (YF) is regarded as the original hemorrhagic fever and has been a major public health problem for at least 250 years. A very effective live attenuated vaccine, strain 17D, was developed in the 1930s and this has proved critical in the control of the disease. There is little doubt that without the vaccine, YF virus would be considered a biosafety level 4 pathogen. Significantly, YF is currently the only disease where an international vaccination certificate is required under the International Health Regulations. Despite having a very successful vaccine, there are occasional issues of supply and demand, such as that which occurred in Angola and Democratic Republic of Congo in 2016 when there was insufficient vaccine available. For the first time fractional dosing of the vaccine was approved on an emergency basis. Thus, continued vigilance and improvements in supply and demand are needed in the future.     

Induction of T lymphocyte responses to dengue virus by a candidate tetravalent live attenuated dengue virus vaccine

Development of a safe and immunogenic tetravalent dengue virus (DV) vaccine has been designated as a priority by the World Health Organization. We characterized the T cell response to DV induced by a candidate live attenuated tetravalent DV vaccine as part of a phase I study. Proliferation and cytotoxic T lymphocyte (CTL) responses to multiple DV serotypes were detected in six of six and four of four subjects studied, respectively. Proliferation responses were higher to DV serotypes 1 and 3 than to serotypes 2 and 4. CTL responses were higher to DV serotypes 2 and 3 than to serotype 1, and included serotype cross-reactive responses. Production of interferon-γ, but not IL-4, was observed in response to DV stimulation. This candidate vaccine is immunogenic for both CD4+ and CD8+ T lymphocytes. However, T cell responses to the four DV serotypes were not equivalent, suggesting that the vaccine could be further optimized.     

Concomitant administration of live attenuated Japanese encephalitis chimeric virus vaccine (JE-CV) and measles,mumps, rubella (MMR) vaccine: Randomized study in toddlers in Taiwan

Background

Japanese encephalitis (JE) is the most important cause of viral encephalitis in Asia.

Methods

In this randomized, open-label, multicenter trial in 550 children aged 12 to 18 months in Taiwan, children received one dose of JE-CV and one dose of MMR vaccine. Vaccines were either administered separately 6 weeks apart (Groups ‘JE-CV’ and ‘MMR’, named after which vaccine was given first), or concomitantly (Group ‘Co-Ad’). JE neutralizing antibody titers were assessed using PRNT₅₀. MMR antibody levels were determined by ELISA.

Results

All groups had low seroprotection/seropositivity rates (<10%) before vaccination for all antigens. Forty two days after vaccination, on either Study Day 42 or 84, seroconversion rates for all antigens were high in all groups, irrespective of the order of vaccinations. Seroconversion for JE ranged from 96.9% in Group Co-Ad on D42 to 100% in Group MMR. Non-inferiority was demonstrated for all analyses as the lower bound of the 95% CI of the difference in seroconversion rates between groups was above the pre-defined limit of −10.0%. The immune responses remained high for all antigens and well above the level of protection 12 months after vaccination in all groups. There were no safety concerns.

Conclusions

JE-CV is safe and induces a strong protective immune response which persists over 1 year when co-administered with MMR vaccine.     

不同毒株制备的腮腺炎疫苗的免疫效果分析

目的了解不同毒株制备的腮腺炎减毒活疫苗的免疫效果,为计划免疫接种疫苗种类的选择提供依据。方法选定广州市东山区1~2岁组未免疫及未患过腮腺炎儿童,分别接种国产S79株、Jeryl-Lynn株、Jeryl-Lynn衍生株腮腺炎减毒活疫苗,开展免疫成功率监测。结果接种国产S79株腮腺炎减毒活疫苗92人,抗体阳性率为54·35%(50/92),GMT为1∶10.43;接种Jeryl-Lynn株疫苗62人,抗体阳性率为91.94%(57/62),GMT为1∶17.72;接种Jeryl-Lynn衍生株疫苗70人,抗体阳性率为90.00%(63/70),GMT为1∶18.72。各组抗体阳性率比较差异有统计学意义(χ2=39.68,P<0.01)。各组抗体几何平均滴度比较,差异有统计学意义(F=13.571,P<0.01)。结论国产S79株腮腺炎疫苗免疫后抗体阳性率较低;为提高免疫成功率,建议尽量选用免疫效果较好的Jeryl-Lynn株和Jeryl-Lynn衍生株腮腺炎减毒活疫苗接种。     

Persistence of rubella antibodies 15 years after subcutaneous administration of Wistar 27/3 strain live attenuated rubella virus vaccine

The rubella-specific antibody levels of children vaccinated with RA27/3 rubella vaccine have been determined over the 15 years since vaccination. Over the period monitored, titres have declined at a comparable rate to those observed in children who had experienced natural rubella infection. In both cohorts the mean rate of decay was similar throughout the 15 years of the study. One in eleven vaccinated children monitored for the entire period of the study reverted to a state of susceptibility to rubella as judged by routine rubella antibody tests used in practice today. The implications of the findings for rubella prophylaxis are discussed.     

Viral interference induced by live attenuated virus vaccine (OPV) can prevent otitis media

Background

The goal of this study was to evaluate whether a live attenuated poliovirus vaccine (OPV) has clinically relevant interfering effect with non-polio infections causing otitis media in young children.

Methods

Open trial in which the intervention group (64 children) received OPV at the age of 2, 3, 6 and 12 months. The control group (250 children) received IPV (inactivated polio vaccine) at the age of 6 and 12 months. Clinical symptoms were recorded by a questionnaire at the age of 3, 6, 12, 18 and 24 months.

Results

Otitis media episodes were less frequent in the OPV than in the control group. A significant difference was seen at the age of 6-18 months (IRR = 0.76 [95% CI 0.59-0.94], P = 0.011) and was particularly clear among children, who attended daycare (IRR 0.37 [95% CI 0.19-0.71], P = 0.003).

Conclusions

OPV provides some protection against otitis media. This effect may be mediated by viral interference with non-polio viruses.     

Efficacy of killed virus vaccine,live attenuated chimeric virus vaccine,and passive immunization for prevention of West Nile virus encephalitis in hamster model

Results of experiments evaluating the efficacy of three immunization strategies for the prevention of West Nile virus (WNV) encephalitis are reported. Immunization strategies evaluated included a killed virus veterinary vaccine, a live attenuated chimeric virus vaccine candidate, and passive immunization with WNV-immune serum; all were tested by using a hamster model of the disease. Each product protected the animals from clinical illness and death when challenged with a hamster-virulent éwild-type WNV strain 1 month after initial immunization. The live attenuated chimeric virus vaccine candidate induced the highest humoral antibody responses, as measured by hemagglutination inhibition, complement fixation, and plaque reduction neutralization tests. Although the duration of protective immunity was not determined in this study, our preliminary results and the cumulative experience of other virus vaccines suggest that the live attenuated chimeric virus provides the longest lasting immunity.