Immune response to live-attenuated Japanese encephalitis vaccine (JE-CV) neutralizes Japanese encephalitis virus isolates from south-east Asia and India

BACKGROUND

During clinical development of the licensed Japanese encephalitis chimeric virus vaccine (JE-CV), the neutralization capacity of vaccine-induced antibodies was assessed against the vaccine virus and against well characterized wild-type (wt) viruses isolated between 1949-1991. We assessed whether JE-CV-induced antibodies can also neutralize more recent wt Japanese encephalitis virus (JEV) isolates including a genotype 1 isolate.

METHODS

Sera from 12-18 month-old children who received a single dose of JE-CV in a phase III study in Thailand and the Philippines (ClinicalTrials.gov NCT00735644) were randomly selected and pooled according to neutralization titer against JE-CV into eight samples. Neutralization was assessed by plaque reduction neutralization tests (PRNT50) against three recent isolates from JEV genotypes 1 and 3 in addition to four JEV previously tested.

RESULTS

Neutralization titers against the three recent JEV strains were comparable to those observed previously against other strains and the vaccine virus. The observed differences between responses to genotype 1 and 3 viruses were within assay variability for the PRNT50.

CONCLUSIONS

The results were consistent with previously generated data on the neutralization of wt JEV isolates, immune responses induced by JE-CV neutralize recently isolated virus from southeast (SE) Asia and India.

Respiratory syncytial virus-specific cell-mediated immune responses after vaccination with a purified fusion protein subunit vaccine

Vaccination with a respiratory syncytial virus (RSV) fusion protein subunit vaccine (PFP-2) was done to determine if this vaccine induced evidence of cell-mediated immunity to RSV and if cell-mediated immunity prevented RSV reinfection. Healthy children 12-18 months old received 50 micrograms of PFP-2 or a saline control. Lymphocyte transformation (LTF) responses were determined before and 1 and 6 months after vaccination. PFP-2 induced positive LTF responses in 5 (83%) of 6 subjects whose prevaccination samples lacked evidence of cell-mediated immunity. Positive LTF responses in prevaccination samples were not boosted but were more persistent in vaccinees than in controls. Positive LTF responses were not associated with protection against subsequent infection. Immunization with PFP-2 induces correlates of cell-mediated immunity, but this immunity does not appear to be a critical component of protection.

Mapping of a fusion related epitope of the respiratory syncytial virus fusion protein

The region of the fusion glycoprotein of respiratory syncytial virus which reacts with a neutralizing and fusion inhibiting monoclonal antibody, was mapped using a deductive method derived from analysis of Western blot reactivity of proteolytic fragments. Reaction of the whole fusion protein was found to be so conformationally dependent, that complete digestion of the protein with a variety of proteases resulted in fragments which were not sufficiently reactive to permit mapping. For this reason, polyclonal antibodies to synthetic peptides which spanned the fusion protein sequence, were used to map the position of large peptides derived from partial digests, and these peptides were then analysed for their ability to react with the monoclonal antibody. Comparison of the peptides which were reactive with the monoclonal antibody to those which were not, identified a region of non-overlap between residues 283 and 327 in the F1 subunit of the fusion protein. Synthesis of a peptide within this region confirmed the placement of the epitope.

Comparison of antigenic sites of subtype-specific respiratory syncytial virus attachment proteins

A panel of 19 monoclonal antibodies (MAbs) were used to probe the antigenic relationships between the G (attachment) proteins of A and B respiratory syncytial virus (RSV) subtypes (GA and GB). At least three and two antigenic sites were present on GA and GB, respectively, including a shared neutralizing site. Most of the antibodies had some degree of complement-independent neutralizing capacity, but in common was a large neutralization-resistant fraction of virus (range 13 to 78%). Passive administration of MAbs to the cross-reactive antigenic site reduced pulmonary virus titres of both A and B subtype virus in the cotton rat model. Protection with subtype-specific MAbs, however, did not always correlate with in vitro neutralizing capacity. The cross-reactive antigenic site appears to be stable to denaturation by polyacrylamide gel electrophoresis and is present on the unglycosylated and partially glycosylated forms of GA and GB by Western blot analysis of infected cell lysates.

The 14 & 6-associated clinical complex: a rejected hypothesis revisited

The 14 & 6 Hz positive spike phenomenon is generally considered a normal variant finding. Our experience prompted this re-evaluation, which consisted of three parts: In children referred for sleep electroencephalograms (EEGs), 100 children with normal EEG and 100 with 14 & 6--the 14 & 6 correlated with behavior disorder and aggression; In 75 children referred for neurological evaluation and EEG because of behavior problems, 52% had 14 & 6 (excluding those with paroxysmal EEGs); and In 57 symptomatic children having prominent 14 & 6, tabulation of symptoms yielded a complex but coherent clinical picture, including disturbances of temper, mood, attention, learning, and sleep. We conclude that 14 & 6 has clinical associations and deserves study.

Aerosolized ribavirin treatment of infants with respiratory syncytial viral infection. A randomized double-blind study

We evaluated a new antiviral agent, ribavirin, in the treatment of infants hospitalized with lower-respiratory-tract disease from respiratory syncytial virus. Ribavirin or placebo was administered to 33 infants in a double-blind manner by continuous aerosol for three to six days. Seventeen infants were treated with placebo, and 16 with ribavirin. By the end of treatment, infants receiving ribavirin had significantly greater improvement in their overall score for severity of illness, in lower-respiratory-tract signs, and in arterial oxygen saturation. Viral shedding was also diminished in the treated groups as compared with the placebo group. No side effects or toxicity were associated with the aerosol therapy. Isolates of respiratory syncytial virus obtained from the infants over the course of therapy showed no change in sensitivity to ribavirin.