A Plaque Method for Rubella Virus Assay

A method has been described in which suitable dilutions of rubella virus will induce the formation, in a monolayer of green monkey kidney cells, of islets of infected cells which were protected from the effects of Echo 11 challenge virus. The number of islets or “negative” plaques was proportional to the dilution of rubella virus inoculated on to the monolayer. Using this method, it was observed that bentonite adsorption increased the plaque assay values of rubella virus pools. This suggested that rubella virus interference may be mediated by an interferon-like principle.     

Rubella and the Rubella Syndrome—New Epidemiologic and Virologic Observations

The importance of rubella lies in the 15 to 20 per cent incidence of damage to the fetus when infection occurs in the first trimester of pregnancy. The “rubella syndrome” appears as various combinations of congenital defects, chiefly cardiac anomalies, cataracts and impaired hearing.Now that the rubella virus has been isolated and grown in tissue culture, it is possible to study the spread of the disease, to determine apparent and inapparent infection rates and to investigate the nature of fetal infection. It has been found that the disease is a highly contagious one in the family setting, and that inapparent infections are more common than overt cases with rash. Infection of the fetus in the early weeks of intrauterine life may become chronic, and virus has been recovered from placenta and fetal specimens collected at induced abortions many weeks after the maternal disease. Infants born with the rubella syndrome are still shedding virus at birth and may continue to do so for at least several months.Gamma globulin, which is effective in preventing measles and hepatitis, has not been highly effective in the prevention of rubella when given to those exposed to the disease. Successful control of the rubella problem will depend upon the development of an active vaccine, which is a possibility now that the virus can be grown in tissue culture.     

New Japanese Rubella Vaccine: Comparative Trials

A total of 142 seronegative volunteers were given one of the following rubella vaccines: Cendehill, HPV77. DE-5, RA27/3, or a new Japanese vaccine, To-336. To-336 vaccine produced a slightly higher geometric mean antibody titre (G.M.T.) (65·7) than did the HPV77. DE-5 (63·1) or RA27/3 vaccine (61·9) but the G.M.T. induced by Cendehill vaccine was much lower (39·3).Reactions, particularly joint symptoms, occurred least commonly after vaccination with To-336 vaccine. Joint symptoms occurred within seven days of menstruation in 30 out of 37 (81%) vaccines (P <0·01); their incidence was not related to oral contraception.Though there is evidence to suggest that Japanese virus strains may be non-teratogenic further data on the incidence of congenitally acquired infection in Japan must be collected before this conclusion can be supported on epidemiological grounds.     

Full Genome Characterisation of Bluetongue Virus Serotype 6 from the Netherlands 2008 and Comparison to Other Field and Vaccine Strains

In mid September 2008, clinical signs of bluetongue (particularly coronitis) were observed in cows on three different farms in eastern Netherlands (Luttenberg, Heeten, and Barchem), two of which had been vaccinated with an inactivated BTV-8 vaccine (during May-June 2008). Bluetongue virus (BTV) infection was also detected on a fourth farm (Oldenzaal) in the same area while testing for export. BTV RNA was subsequently identified by real time RT-PCR targeting genome-segment (Seg-) 10, in blood samples from each farm. The virus was isolated from the Heeten sample (IAH “dsRNA virus reference collection” [dsRNA-VRC] isolate number NET2008/05) and typed as BTV-6 by RT-PCR targeting Seg-2. Sequencing confirmed the virus type, showing an identical Seg-2 sequence to that of the South African BTV-6 live-vaccine-strain. Although most of the other genome segments also showed very high levels of identity to the BTV-6 vaccine (99.7 to 100%), Seg-10 showed greatest identity (98.4%) to the BTV-2 vaccine (RSAvvv2/02), indicating that NET2008/05 had acquired a different Seg-10 by reassortment. Although Seg-7 from NET2008/05 was also most closely related to the BTV-6 vaccine (99.7/100% nt/aa identity), the Seg-7 sequence derived from the blood sample of the same animal (NET2008/06) was identical to that of the Netherlands BTV-8 (NET2006/04 and NET2007/01). This indicates that the blood contained two different Seg-7 sequences, one of which (from the BTV-6 vaccine) was selected during virus isolation in cell-culture. The predominance of the BTV-8 Seg-7 in the blood sample suggests that the virus was in the process of reassorting with the northern field strain of BTV-8. Two genome segments of the virus showed significant differences from the BTV-6 vaccine, indicating that they had been acquired by reassortment event with BTV-8, and another unknown parental-strain. However, the route by which BTV-6 and BTV-8 entered northern Europe was not established.     

A Conserved E7-derived Cytotoxic T Lymphocyte Epitope Expressed on Human Papillomavirus 16-transformed HLA-A2+ Epithelial Cancers

Human Papillomavirus 16 (HPV-16) has been identified as the causative agent of 50% of cervical cancers and many other HPV-associated tumors. The transforming potential/tumor maintenance capacity of this high risk HPV is mediated by two viral oncoproteins, E6 and E7, making them attractive targets for therapeutic vaccines. Of 21 E6 and E7 peptides computed to bind HLA-A*0201, 10 were confirmed through TAP-deficient T2 cell HLA stabilization assay. Those scoring positive were investigated to ascertain which were naturally processed and presented by surface HLA molecules for CTL recognition. Because IFNγ ELISpot frequencies from healthy HPV-exposed blood donors against HLA-A*0201-binding peptides were unable to identify specificities for tumor targeting, their physical presence among peptides eluted from HPV-16-transformed epithelial tumor HLA-A*0201 immunoprecipitates was analyzed by MS³ Poisson detection mass spectrometry. Only one epitope (E7_11–19) highly conserved among HPV-16 strains was detected. This 9-mer serves to direct cytolysis by T cell lines, whereas a related 10-mer (E7_11–20), previously used as a vaccine candidate, was neither detected by MS³ on HPV-transformed tumor cells nor effectively recognized by 9-mer specific CTL. These data underscore the importance of precisely defining CTL epitopes on tumor cells and offer a paradigm for T cell-based vaccine design.     

Use of Medroxyprogesterone Acetate as a Contraceptive in conjunction with Early Postpartum Rubella Vaccination

During a 12-month period 170 women received early postpartum rubella vaccination. An injectable “depot” progestogen was given to each of these patients for contraceptive purposes at the same time as the vaccine was administered. Subsequent observations showed that the progestogen was effective as a contraceptive in this context and that it did not appear to affect the immune response of the patients to the vaccine.     

Transplacental Transmission of Rubella Virus Infection in Rabbits

Rabbits were inseminated artificially and inoculated 1 week later with rubella virus. The attenuated vaccine strain HPV-77 or strain 67-1127 which had been through 12 cell culture passages was used. Half of the rabbits in each group had been inoculated 1 month prior to insemination with the corresponding strain. Evidence of infection induced by either strain was obtained by immunofluorescence in lung, spleen, and placenta. Rubella virus antigen was also found in the lung of a 2-month-old rabbit of a dam inoculated with strain 67-1127. A high rate of stillbirths and neonatal deaths and poor weight gain occurred in litters of the 67-1127 group.     

Live Attenuated Rubella Vaccine (Cendehill Strain) in School Children

The purpose of this study was to further determine the efficacy and safety in school children of the Cendehill strain of live attenuated rubella vaccine. Parental permission was requested for 255 children in Grades I, II and VI, attending two adjacent schools, to have blood taken for rubella hemagglutination-inhibition studies at the beginning and end of the study, and for each child seronegative on initial testing to participate as a vaccinee or a control. Vaccinees received either 0.5 ml. (full recommended dose) or 0.25 ml. of rubella virus vaccine, live attenuated, Cendehill strain (Smith Kline & French).Eighty-one per cent of the parents consented to have their child take part. Seventy-nine per cent of Grade I and II pupils and 41% of Grade VI pupils were found to be susceptible to rubella at the time of the initial test (HI titres [unk] 8). Eighty children received rubella vaccine and 98.7% showed at least a four-fold rise in antibody titre. One child who received 0.25 ml. showed only a two-fold rise. Clinical reactions to the vaccine were absent or minimal. Thirty-eight controls remained serologically negative during the study.The good response to half-doses of Cendehill vaccine is not significant because there were >3000 TCID₅₀ in a full dose (three times the dose recommended). This information was unknown by the investigators until the termination of the study.     

Rift valley fever virus lacking the NSs and NSm genes is highly attenuated, confers protective immunity from virulent virus challenge, and allows for differential identification of infected and vaccinated animals

Rift Valley fever (RVF) virus is a mosquito-borne human and veterinary pathogen associated with large outbreaks of severe disease throughout Africa and more recently the Arabian peninsula. Infection of livestock can result in sweeping “abortion storms” and high mortality among young animals. Human infection results in self-limiting febrile disease that in ~1 to 2% of patients progresses to more serious complications including hepatitis, encephalitis, and retinitis or a hemorrhagic syndrome with high fatality. The virus S segment-encoded NSs and the M segment-encoded NSm proteins are important virulence factors. The development of safe, effective vaccines and tools to screen and evaluate antiviral compounds is critical for future control strategies. Here, we report the successful reverse genetics generation of multiple recombinant enhanced green fluorescent protein-tagged RVF viruses containing either the full-length, complete virus genome or precise deletions of the NSs gene alone or the NSs/NSm genes in combination, thus creating attenuating deletions on multiple virus genome segments. These viruses were highly attenuated, with no detectable viremia or clinical illness observed with high challenge dosages (1.0 × 10⁴ PFU) in the rat lethal disease model. A single-dose immunization regimen induced robust anti-RVF virus immunoglobulin G antibodies (titer, ~1:6,400) by day 26 postvaccination. All vaccinated animals that were subsequently challenged with a high dose of virulent RVF virus survived infection and could be serologically differentiated from naïve, experimentally infected animals by the lack of NSs antibodies. These rationally designed marker RVF vaccine viruses will be useful tools for in vitro screening of therapeutic compounds and will provide a basis for further development of RVF virus marker vaccines for use in endemic regions or following the natural or intentional introduction of the virus into previously unaffected areas.     

Comparison of Fluorescent Antibody Induced by Rubella Virus in Vaccinee and Convalescent Individuals

Specific rubella antibody detectable by indirect immunofluorescence developed in response to immunization with attenuated rubella vaccine, HPV-77, DK-12. Fluorescent antibody (FA) was found when vaccinee sera were reacted with antigens synthesized in three different acutely infected continuous cell lines: BHK-21, LLCMK-2, and RK-13. FA titers were high, and they correlated with antibody titers obtained by hemagglutination-inhibition tests. Levels of FA in vaccinated individuals were slightly lower than those found in persons recovered from natural rubella infections. Rubella FA persists a long time in convalescent individuals and appears to be maintained for at least 19 months in vaccinees.     

Replicative Capacity of Human Immunodeficiency Virus Type 1 Transmitted from Mother to Child Is Associated with Pediatric Disease Progression Rate

Human immunodeficiency virus (HIV)-infected infants in the developing world typically progress to AIDS or death within the first 2 years of life. However, a minority progress relatively slowly. This study addresses the potential contribution of viral factors to HIV disease progression in eight infants selected from a well-characterized cohort of C clade HIV-infected infants, monitored prospectively from birth in Durban, South Africa. Three infants were defined as “progressors,” and five were defined as “slow progressors.” We observed that slow-progressor infants carry HIV isolates with significantly lower replicative capacity compared to virus from progressors. Furthermore, our data suggest a link between the attenuated viral phenotype and HLA-B* 57/5801 epitope-specific Gag mutational patterns of the transmitted virus and not to coreceptor usage or to the presence of Nef deletions or insertions. These data underline the importance of virus-host interactions and highlight the contribution of viral attenuation through Gag-specific CD8⁺ T-cell escape mutations, among other factors, in the control of pediatric HIV infection.Untreated human immunodeficiency virus (HIV)-infected infants progress more rapidly to AIDS and death than older children or adults (35). This is particularly the case in resource-limited settings, where mortality exceeds 50% by 2 years of age. Viral loads during infancy remain strikingly high, and the rapid reduction in viremia from peak levels characteristic of acute adult infection occurs only slowly over the first few years of life in pediatric infection. This late reduction in viremia, compared to the establishment of viral setpoint within a few weeks in adult infection, may coincide with the normal maturation of infant adaptive immune responses.There are several additional reasons for impaired virological control during infancy. First, HIV-induced T-cell depletion damages the developing immune system before an effective antiviral response can be mounted (13, 23). Second, HIV-infected infants are more likely to possess nonprotective HLA alleles, since at least 50% of the infant''s HLA genotype is shared with the mother, and high maternal viremia is a risk factor for perinatal HIV transmission (35). Finally, the infecting virus may be adapted to maternally and paternally inherited HLA genes (19, 38). However, a minority of infants progress relatively slowly. The immune correlates of slow progression in pediatric HIV infection are still not well understood. In this context, the interactions between characteristics of the maternal virus transmitted but also the CD8⁺ T-cell responses generated by the child are likely to be important factors to HIV control in pediatric infection, as in adults (11, 28).In certain cases described in the literature, the biological properties of the virus have been determined as the primary reason for effective HIV control. Presence of attenuated HIV variants with low replicative capacity (RC) has been linked to nonprogressive disease (12, 36) and elite control (28) in HIV-infected adults. Moreover, transmission of certain HIV Gag CD8⁺ T-cell escape variants to a recipient lacking the same HLA molecules leads to reduced viral set point in acute adult infection and contributes to higher CD4 counts and lower viral load (6, 14). In other cases, control of viremia has been strongly associated with CD8⁺ T-cell responses mediated by “protective” HLA alleles such as HLA-B*57 or B*27 (16). In HIV-infected children, as in adults, there is evidence that CD8⁺ T-cell responses can contribute to viral containment and that the “protective” effect of certain HLA alleles identified in adult HIV infection may also operate in pediatric infection (42). In addition, HIV-infected infants lacking protective HLA alleles but whose mothers express protective HLA alleles such as HLA-B*57, B*5801, or B*8101 tend to progress more slowly, for reasons hypothesized to relate to transmission of virus that has been attenuated by the selection of CD8⁺ T-cell escape mutants in the mother (41).We therefore undertook the present study in perinatally HIV-infected infants in Durban, South Africa, the epicenter of the pediatric epidemic, to investigate the potential role of the viral RC of mother-to-child transmitted virus on pediatric HIV disease progression. We studied eight infants with clade C HIV infection: three defined as progressors (P) and five as slow progressors (SP). To characterize in detail biological properties of the virus, viral variants were isolated from plasma samples in both groups. The RC of viral isolates was measured in vitro in primary cells. In addition, viral tropism was determined for these isolates, together with the presence of polymorphisms in Nef, and of HLA-B*57/5801-associated Gag escape mutants, since these have been additional factors previously linked to viral attenuation and disease outcome.     

Viral Nucleic Acids in Live-Attenuated Vaccines: Detection of Minority Variants and an Adventitious Virus

Metagenomics and a panmicrobial microarray were used to examine eight live-attenuated viral vaccines. Viral nucleic acids in trivalent oral poliovirus (OPV), rubella, measles, yellow fever, varicella-zoster, multivalent measles/mumps/rubella, and two rotavirus live vaccines were partially purified, randomly amplified, and pyrosequenced. Over half a million sequence reads were generated covering from 20 to 99% of the attenuated viral genomes at depths reaching up to 8,000 reads per nucleotides. Mutations and minority variants, relative to vaccine strains, not known to affect attenuation were detected in OPV, mumps virus, and varicella-zoster virus. The anticipated detection of endogenous retroviral sequences from the producer avian and primate cells was confirmed. Avian leukosis virus (ALV), previously shown to be noninfectious for humans, was present as RNA in viral particles, while simian retrovirus (SRV) was present as genetically defective DNA. Rotarix, an orally administered rotavirus vaccine, contained porcine circovirus-1 (PCV1), a highly prevalent nonpathogenic pig virus, which has not been shown to be infectious in humans. Hybridization of vaccine nucleic acids to a panmicrobial microarray confirmed the presence of endogenous retroviral and PCV1 nucleic acids. Deep sequencing and microarrays can therefore detect attenuated virus sequence changes, minority variants, and adventitious viruses and help maintain the current safety record of live-attenuated viral vaccines.Highly effective, safe, and relatively inexpensive, live-attenuated viruses protect against numerous human and animal viral infections. Attenuation is achieved by genetically adapting viruses for replication in a different host species or under nonphysiological conditions, such that viruses lose their pathogenic potential in their original host species while remaining sufficiently antigenic to induce lasting protective immunity. Live-attenuated vaccines are highly efficacious due to the physiologic presentation of native antigen to the host''s immune system and include the earliest human vaccine developed by serial passages of rabies virus in rabbits. In very rare instances, one attenuated viral vaccine, the oral poliovirus vaccine (OPV), can accumulate mutations as well as recombine with other coinfecting enteroviruses and revert to a pathogenic state (18, 24). Attenuated live vaccines also carry a potential risk of contamination with adventitious viruses introduced during the attenuation process, from the cell lines used, and/or from the animal sera or other biologics often used in cell cultures. Very early Theiler''s yellow fever attenuated virus was once “stabilized” with human plasma thought to contain hepatitis B virus, resulting in many cases of hepatitis (5, 28). Some early Sabin poliovirus vaccines were contaminated with the simian virus 40 (SV40) polyomavirus from the monkey cells used to amplify polioviruses. While carcinogenic in rodents, SV40 has no epidemiologic association with human cancers (10). Avian leukosis virus (ALV) and endogenous avian virus (AEV) have been reported in attenuated vaccines grown in chicken embryo fibroblasts (CEF), but extensive testing has also ruled out human infections (14, 15). Vaccine-associated ALV and AEV are thought to originate from endogenous retroviruses in the chicken germ line (14, 15, 17).Because the chemical inactivation used in the manufacture of killed-virus vaccines is also likely to inactivate adventitious viruses, we focused on eight live-attenuated viruses, OPV (Biopolio), rubella (Meruvax-II), measles (Attenuvax), yellow fever (YF-Vax), human herpesvirus 3 (HHV-3) (Varivax), rotavirus (Rotarix and Rotateq), and multivalent measles/mumps/rubella (MMR-II), to resequence the attenuated viruses and test for the presence of adventitious viruses after viral particle purification, massively parallel pyrosequencing, and viral sequence similarity searches. Vaccine nucleic acids were also analyzed using a panmicrobial microarray.     

A Controlled Study of Disturbances Recorded Following the Use of Oral Poliomyelitis Vaccine

A double-blind study of disturbances recorded following the administration of a live trivalent oral poliomyelitis vaccine and an identical-appearing placebo was undertaken. Seven hundred and forty-one persons, 81% of the entire population of a small town, constituted the trial group. The two feedings, with a varied feeding sequence, were eight days apart, and at the second feeding and again eight days later, the participants were investigated under controlled conditions. There were no statistically significant differences in the number, nature or timing of the disturbances reported following the administration of the two vaccines. With both vaccines, significantly fewer reactions were reported among males, among the under-5 year group, among Occupational Class I, and after the first feeding as compared with the second. The Salk vaccine immunization status of the participants made no significant difference. With both active vaccine and placebo “vaccine” 14 to 15% of the participants reported some “reaction”.     

Factors associated with uptake of measles,mumps, and rubella vaccine (MMR) and use of single antigen vaccines in a contemporary UK cohort: prospective cohort study

Objectives To estimate uptake of the combined measles, mumps, and rubella vaccine (MMR) and single antigen vaccines and explore factors associated with uptake and reasons for not using MMR.Design Nationally representative cohort study.Setting Children born in the UK, 2000-2.Participants 14 578 children for whom data on immunisation were available.Main outcome measures Immunisation status at 3 years defined as “immunised with MMR,” “immunised with at least one single antigen vaccine,” and “unimmunised.”Results 88.6% (13 013) were immunised with MMR and 5.2% (634) had received at least one single antigen vaccine. Children were more likely to be unimmunised if they lived in a household with other children (risk ratio 1.74, 95% confidence interval 1.35 to 2.25, for those living with three or more) or a lone parent (1.31, 1.07 to 1.60) or if their mother was under 20 (1.41, 1.08 to 1.85) or over 34 at cohort child’s birth (reaching 2.34, 1.20 to 3.23, for ≥40), more highly educated (1.41, 1.05 to 1.89, for a degree), not employed (1.43, 1.12 to 1.82), or self employed (1.71, 1.18 to 2.47). Use of single vaccines increased with household income (reaching 2.98, 2.05 to 4.32, for incomes of ≥£52 000 (€69 750, $102 190)), maternal age (reaching 3.04, 2.05 to 4.50, for ≥40), and education (reaching 3.15, 1.78 to 5.58, for a degree). Children were less likely to have received single vaccines if they lived with other children (reaching 0.14, 0.07 to 0.29, for three or more), had mothers who were Indian (0.50, 0.25 to 0.99), Pakistani or Bangladeshi (0.13, 0.04 to 0.39), or black (0.31, 0.14 to 0.64), or aged under 25 (reaching 0.14, 0.05 to 0.36, for 14-19). Nearly three quarters (74.4%, 1110) of parents who did not immunise with MMR made a “conscious decision” not to immunise. Conclusions Although MMR uptake in this cohort is high, a substantial proportion of children remain susceptible to avoidable infection, largely because parents consciously decide not to immunise. Social differentials in uptake could be used to inform targeted interventions to promote uptake.     

COXSACKIE VIRUSES—A Review of Pathologic,Epidemiologic, Diagnostic and Etiologic Observations

Coxsackie disease comprises three clinical entities—herpangina, so-called non-paralytic poliomyelitis, and epidemic pleurodynia. Several strains of antigenically-related viruses, Groups A and B, designated as Coxsackie virus have been isolated from stool specimens and from material from the throat of many patients with the diseases mentioned. Inasmuch as the virus has also been recovered from normal persons, there is as yet uncertainty as to causal relationship between the presence of the virus and the disease. Reports of the isolation of Coxsackie virus and poliomyelitis virus from the same patient make difficult the interpretation of the findings.The diagnosis of Coxsackie disease entails animal inoculation and serologic procedures. Emphasis is placed on the necessity of obtaining stool specimens, throat washings, and “paired” blood specimens from patients suspected of the disease.     

Development of a next-generation chikungunya virus vaccine based on the HydroVax platform

Chikungunya virus (CHIKV) is an emerging/re-emerging mosquito-borne pathogen responsible for explosive epidemics of febrile illness characterized by debilitating polyarthralgia and the risk of lethal infection among the most severe cases. Despite the public health risk posed by CHIKV, no vaccine is currently available. Using a site-directed hydrogen peroxide-based inactivation approach, we developed a new CHIKV vaccine, HydroVax-CHIKV. This vaccine technology was compared to other common virus inactivation approaches including β-propiolactone (BPL), formaldehyde, heat, and ultraviolet (UV) irradiation. Heat, UV, and BPL were efficient at inactivating CHIKV-181/25 but caused substantial damage to neutralizing epitopes and failed to induce high-titer neutralizing antibodies in vaccinated mice. HydroVax-CHIKV and formaldehyde-inactivated CHIKV retained intact neutralizing epitopes similar to live virus controls but the HydroVax-CHIKV approach demonstrated a more rapid rate of virus inactivation. HydroVax-CHIKV vaccination induced high neutralizing responses to homologous and heterologous CHIKV clades as well as to other alphaviruses including Mayaro virus, O’nyong’nyong virus, and Una virus. Following heterologous infection with CHIKV-SL15649, HydroVax-CHIKV-immunized mice were protected against viremia, CHIKV-associated arthritic disease, and lethal CHIKV infection by an antibody-dependent mechanism. In contrast, animals vaccinated with Heat- or UV-inactivated virus showed no protection against viremia in addition to demonstrating significantly exacerbated CD4⁺ T cell-mediated footpad swelling after CHIKV infection. Together, these results demonstrate the risks associated with using suboptimal inactivation methods that fail to elicit protective neutralizing antibody responses and show that HydroVax-CHIKV represents a promising new vaccine candidate for prevention of CHIKV-associated disease.     

Inactivation of rubella virus by gamma radiation

The Gilchrist and M-33 strains of rubella virus exposed in the frozen state to ¹³⁷Ce or ⁶⁰Co were inactivated exponentially according to “one hit” kinetics. There was no difference in the radiosensitivity of the two strains. Experimental D₃₇ values for both strains ranged from 1.9 × 10⁵ to 2.9 × 10⁵ rads, and computed radiosensitive molecular weights ranged from 2.6 × 10⁶ to 4.0 × 10⁶ daltons.     

Human Circulating Antibody-Producing B Cell as a Predictive Measure of Mucosal Immunity to Poliovirus

Background

The “gold standard” for assessing mucosal immunity after vaccination with poliovirus vaccines consists in measuring virus excretion in stool after challenge with oral poliovirus vaccine (OPV). This testing is time and resource intensive, and development of alternative methods is a priority for accelerating polio eradication. We therefore evaluated circulating antibody-secreting cells (ASCs) as a potential means to evaluate mucosal immunity to poliovirus vaccine.

Methods

199 subjects, aged 10 years, and previously immunized repeatedly with OPV, were selected. Subjects were assigned to receive either a booster dose of inactivated poliovirus vaccine (IPV), bivalent OPV (bOPV), or no vaccine. Using a micro-modified whole blood-based ELISPOT assay designed for field setting, circulating poliovirus type-specific IgA- and IgG-ASCs, including gut homing α4β7+ ASCs, were enumerated on days 0 and 7 after booster immunization. In addition, serum samples collected on days 0, 28 and 56 were tested for neutralizing antibody titers against poliovirus types 1, 2, and 3. Stool specimens were collected on day 28 (day of bOPV challenge), and on days 31, 35 and 42 and processed for poliovirus isolation.

Results

An IPV dose elicited blood IgA- and IgG-ASC responses in 84.8 to 94.9% of subjects, respectively. In comparison, a bOPV dose evoked corresponding blood ASC responses in 20.0 to 48.6% of subjects. A significant association was found between IgA- and IgG-ASC responses and serum neutralizing antibody titers for poliovirus type 1, 2, 3 (p<0.001). In the IPV group, α4β7⁺ ASCs accounted for a substantial proportion of IgA-ASCs and the proportion of subjects with a positive α4β7⁺ IgA-ASC response to poliovirus types 1, 2 and 3 was 62.7%, 89.8% and 45.8%, respectively. A significant association was observed between virus excretion and α4β7⁺ IgA^- and/or IgG-ASC responses to poliovirus type 3 among immunized children; however, only a weak association was found for type 1 poliovirus.

Discussion

Our results suggest that virus-specific blood ASCs, especially for type 3 poliovirus, can serve as surrogate of mucosal immunity after vaccination. Further studies are needed to evaluate the duration of such memory responses and to assess the programmatic utility of this whole blood-based mucosal ASC testing for the polio eradication program.     

Development of a challenge-protective vaccine concept by modification of the viral RNA-dependent RNA polymerase of canine distemper virus

We demonstrate that insertion of the open reading frame of enhanced green fluorescent protein (EGFP) into the coding sequence for the second hinge region of the viral L (large) protein (RNA-dependent RNA polymerase) attenuates a wild-type canine distemper virus. Moreover, we show that single intranasal immunization with this recombinant virus provides significant protection against challenge with the virulent parental virus. Protection against wild-type challenge was gained either after recovery of cellular immunity postimmunization or after development of neutralizing antibodies. Insertion of EGFP seems to result in overattenuation of the virus, while our previous experiments demonstrated that the insertion of an epitope tag into a similar position did not affect L protein function. Thus, a desirable level of attenuation could be reached by manipulating the length of the insert (in the second hinge region of the L protein), providing additional tools for optimization of controlled attenuation. This strategy for controlled attenuation may be useful for a “quick response” in vaccine development against well-known and “new” viral infections and could be combined efficiently with other strategies of vaccine development and delivery systems.     

Generation by Reverse Genetics of an Effective,Stable, Live-Attenuated Newcastle Disease Virus Vaccine Based on a Currently Circulating,Highly Virulent Indonesian Strain

Newcastle disease virus (NDV) can cause severe disease in chickens. Although NDV vaccines exist, there are frequent reports of outbreaks in vaccinated chickens. During 2009–2010, despite intense vaccination, NDV caused major outbreaks among commercial poultry farms in Indonesia. These outbreaks raised concern regarding the protective immunity of current vaccines against circulating virulent strains in Indonesia. In this study, we investigated whether a recombinant attenuated Indonesian NDV strain could provide better protection against prevalent Indonesian viruses. A reverse genetics system for the highly virulent NDV strain Banjarmasin/010/10 (Ban/010) isolated in Indonesia in 2010 was constructed. The Ban/010 virus is classified in genotype VII of class II NDV, which is genetically distinct from the commercial vaccine strains B1 and LaSota, which belong to genotype II, and shares only 89 and 87% amino acid identity for the protective antigens F and HN, respectively. A mutant virus, named Ban/AF, was developed in which the virulent F protein cleavage site motif “RRQKR↓F” was modified to an avirulent motif “GRQGR↓L” by three amino acid substitutions (underlined). The Ban/AF vaccine virus did not produce syncytia or plaques in cell culture, even in the presence of added protease. Pathogenicity tests showed that Ban/AF was completely avirulent. Ban/AF replicated efficiently during 10 consecutive passages in chickens and remained genetically stable. Serological analysis showed that Ban/AF induced higher neutralization and hemagglutination inhibition antibody titers against the prevalent viruses than the commercial vaccines B1 or LaSota. Both Ban/AF and commercial vaccines provided protection against clinical disease and mortality after challenge with virulent NDV strain Ban/010 (genotype VII) or GB Texas (genotype II). However, Ban/AF significantly reduced challenge virus shedding from the vaccinated birds compared to B1 vaccine. These results suggest that Ban/AF can provide better protection than commercial vaccines and is a promising vaccine candidate against NDV strains circulating in Indonesia.