The highly sensitive gamma interferon (IFN-␥) enzyme-linked immunosorbent spot (ELISPOT) assay permits the investigation of the role of cell-mediated immunity (CMI) in the protection of young children against influenza. Preliminary studies of young children confirmed that the IFN-␥ ELISPOT assay was a more sensitive measure of influenza memory immune responses than serum antibody and that among seronegative children aged 6 to <36 months, an intranasal dose of 10 7 fluorescent focus units (FFU) of a live attenuated influenza virus vaccine (CAIV-T) elicited substantial CMI responses. A commercial inactivated influenza virus vaccine elicited CMI responses only in children with some previous exposure to related influenza viruses as determined by detectable antibody levels prevaccination. The role of CMI in actual protection against community-acquired, culture-confirmed clinical influenza by CAIV-T was investigated in a large randomized, double-blind, placebo-controlled dose-ranging efficacy trial with 2,172 children aged 6 to <36 months in the Philippines and Thailand. The estimated protection curve indicated that the majority of infants and young children with >100 spot-forming cells/10 6 peripheral blood mononuclear cells were protected against clinical influenza, establishing a possible target level of CMI for future influenza vaccine development. The ELISPOT assay for IFN-␥ is a sensitive and reproducible measure of CMI and memory immune responses and contributes to establishing requirements for the future development of vaccines against influenza, especially those used for children.

Timely diagnosis of respiratory syncytial virus (RSV) infection is critical for appropriate treatment of lower respiratory infection in young children. To facilitate diagnosis, we developed a rapid, specific, and sensitive TaqMan Respiratory syncytial virus (RSV) is one of the major respiratory pathogens causing lower respiratory tract diseases in children (10,18,23). Based on genetic and antigenic variations in the structural proteins, RSV is classified into two subgroups, A and B (3, 24). At present, there is no vaccine available for prevention of the viral infection, although antiviral therapy is known to be effective in some patients (1, 2, 11). For appropriate treatment of RSV infection, it is crucial to have an accurate and timely diagnostic method for detection of the virus.A number of techniques are available for detection and identification of RSV, including cell culture, enzyme immunoassay (EIA), immunofluorescence (IF), and conventional reverse transcription (RT)-PCR (6,7,8,9,12,16,17,21,22,25). The classical cell culture method requires prompt inoculation of the labile virus and is a time-consuming process. In addition, the test has low sensitivity, detecting only 50 to 60% of RSV infections (17). More rapid immunoassays for the detection of RSV, such as EIA and IF, also have limitations in sensitivity and specificity. The accuracy of EIA, for example, is in the range of 57 to 98%, and that of IF varies from 65 to 92% (12). This wide variability in assay sensitivity and specificity may lead to inaccurate diagnosis of RSV infection, and consequently, the assays may be of limited value in patient care. Furthermore, such rapid immunoassays are rarely capable of differentiating RSV subgroups A and B, which may be associated with different disease severities (28).Conventional RT-PCR, which has recently been developed for the detection of RSV, is a more sensitive and specific diagnostic method that also allows for the subgrouping of the virus in a single reaction (6,7,8,9,17,25). However, it still requires time-consuming post-PCR analysis. Real-time RT-PCR, on the other hand, eliminates post-PCR processing (13). This is achieved by combining conventional RT-PCR with advanced fluorescence detection technology, which allows the fluorescence signals to be analyzed and recorded during PCR cycling. The advanced method also performs automatic sample analysis with enhanced sensitivity and specificity. In this report, we describe the development and application of a TaqManbased RT-PCR assay for simultaneous detection, subgrouping, and quantification of RSV A and B in clinical respiratory specimens. MATERIALS AND METHODSVirus stocks, plaque titration, and virus particle counts. RSV A2 (subgroup A) and 2B (subgroup B) were propagated in Vero cells. About 100 ml each of subgroup A and B virus stocks were prepared, and the stocks were stored in 0.5-ml aliquots for future use. For plaque titration of RSV stocks, confluent Vero cells in 24-well plates were inoculated with 100 l of a serial dilution of each virus at 37°...

CAIV-T was well tolerated and effective in preventing culture-confirmed influenza illness over multiple and complex influenza seasons in young children in Asia.

A large placebo-controlled efficacy trial of the rhesus tetravalent (RRV-TV) and serotype G1 monovalent (RRV-S1) rotavirus vaccines was conducted in 1991-1992 at 24 sites across the United States. Protection was 49% and 54% against all diarrhea but 80% and 69% against very severe gastroenteritis for the two vaccines, respectively. Post-vaccination neutralizing antibody titers to the G1 Wa strain, whose VP7 protein is nearly identical to that of the D strain of rotavirus contained in both vaccines, did not correlate with protection against subsequent illness with G1 strains. This result raised the possibility that in infants who developed post-vaccination neutralizing antibody to Wa, breakthrough (i.e., vaccine failure-the occurrence of rotavirus diarrhea after immunization) may have been due to infection by G1 strains that were sufficiently antigenically distinct from the vaccine strain to evade the neutralizing antibodies elicited by vaccination. To test this hypothesis, we initially compared post-vaccination neutralizing antibody titers of vaccinees against Wa and G1 breakthrough strains using sera from subjects who experienced breakthrough. Post-immunization neutralizing antibody titers to Wa elicited by vaccination were significantly (P< 0.001) greater than to the breakthrough strains subsequently obtained from these subjects. This difference did not, however, correlate with lack of protection since similar differences in titer to Wa and breakthrough strains were found using post-vaccination sera from vaccinees who either experienced asymptomatic rotavirus infections or no infections. To determine the genetic basis for these differences, we compared the VP7 gene sequences of Wa with vaccine strain D, 12 G1 breakthrough strains, and 3 G1 control strains isolated during the same trial from placebo recipients. All breakthrough strains were distinct from Wa and D in antigenically important regions throughout the VP7 protein, but these differences were conserved between breakthrough and placebo strains. Furthermore, a comparative analysis of the deduced amino sequences form VP7 genes of G1 rotaviruses from 12 countries indicated that four distinct lineages have evolved. All breakthrough and control strains from the U.S. vaccine trial were in a lineage different from strain D, the serotype G1 vaccine strain. Although the overall results do not support our original hypothesis that immune selection of antigenically distinct escape mutants led to vaccine breakthrough in subjects with a neutralization response to Wa, it cannot be excluded that breakthrough could be partially due to antigenic differences in the VP7 proteins of currently circulating G1 strains.

Cold-adapted influenza vaccine-trivalent was well tolerated and effective in preventing culture-confirmed influenza illness in children as young as 6 months of age who attended day care.