RESUMEN

The role of secretory IgA in conferring cross-protective immunity was examined in polymeric (p)IgR knockout (KO) mice immunized intranasally with different inactivated vaccines prepared from A/PR/8/34 (H1N1), A/Yamagata/120/86 (H1N1), A/Beijing/262/95 (H1N1), and B/Ibaraki/2/85 viruses and infected with the A/PR/8/34 virus in the upper respiratory tract (RT)-restricting volume. In wild-type mice, immunization with A/PR/8/34 or its variant (A/Yamagata/120/86 and A/Beijing/262/95) vaccines conferred complete protection or partial cross-protection against infection, while the B-type virus vaccine failed to provide protection. The protection or cross-protection was accompanied by an increase in the nasal A/PR/8/34 hemagglutinin-reactive IgA concentration, which was estimated to be >30 times the serum IgA concentration and much higher than the nasal IgG concentration. In contrast, the blockade of transepithelial transport of dimeric IgA in pIgR-KO mice reduced the degree of protection or cross-protection, in parallel with the marked increase in serum IgA concentration and the decrease in nasal IgA concentration (about 20 and 0.3 times those in wild-type mice, respectively). The degree of the reduction of protection or cross-protection was moderately reversed by the low but non-negligible level of nasal IgA, transudates from the accumulated serum IgA. These results, together with the absence of the IgA-dependent cross-protection in the lower RT and the unaltered level of nasal or serum IgG in wild-type and pIgR-KO mice, confirm that the actively secreted IgA plays an important role in cross-protection against variant virus infection in the upper RT, which cannot be substituted by serum IgG.

Asunto(s)

Adyuvantes Inmunológicos/administración & dosificación , Virus de la Influenza A/inmunología , Vacunas contra la Influenza/administración & dosificación , Vacunas contra la Influenza/inmunología , Infecciones por Orthomyxoviridae/genética , Infecciones por Orthomyxoviridae/inmunología , Receptores de Inmunoglobulina Polimérica/deficiencia , Receptores de Inmunoglobulina Polimérica/genética , Administración Intranasal , Animales , Anticuerpos Antivirales/biosíntesis , Anticuerpos Antivirales/química , Toxina del Cólera/administración & dosificación , Toxina del Cólera/inmunología , Femenino , Glicoproteínas Hemaglutininas del Virus de la Influenza/administración & dosificación , Glicoproteínas Hemaglutininas del Virus de la Influenza/inmunología , Inmunización Secundaria , Inmunoglobulina A/biosíntesis , Inmunoglobulina A/química , Inmunoglobulina G/biosíntesis , Inmunoglobulina G/química , Masculino , Ratones , Ratones Endogámicos BALB C , Ratones Noqueados , Ratones Transgénicos , Infecciones por Orthomyxoviridae/prevención & control , Infecciones del Sistema Respiratorio/inmunología , Infecciones del Sistema Respiratorio/prevención & control , Vacunas Combinadas/administración & dosificación , Vacunas Combinadas/inmunología

RESUMEN

To identify penicillin (Pc) and other ß-lactam resistance in 310 clinical isolates of Streptococcus pneumoniae by polymerase chain reaction (PCR), 3 sets of primers were designed to amplify Pc-binding protein (PBP) genes previously detected in Pc-susceptible strains: 1) a 430-bp fragment of the pbp1a gene, 2) a 292-bp fragment of the pbp2x gene, and 3) a 77-bp fragment of the pbp2b gene. The amplified regions of each PBP gene were positioned in highly divergent sequences of Pc-resistant S. pneumoniae. In other words, isolates for which these DNA fragments were detected were regarded as possessing sequences almost the same as that of the susceptible R6 strain and those for which these DNA fragments were not detected were assumed to have mutations. A set of primers that amplify 273 bp of the autolysin (lytA) gene to identify S. pneumoniae was applied as well. Of 166 isolates for which the minimum inhibitory concentration (MIC) of Pc were ≤0.06µg/mL, 83 (50.0%) were confirmed to be true susceptible strains with no PBP gene mutation and most of the remaining strains were found to possess pbp2x mutation. In contrast, most of 109 isolates for which the MIC of Pc were ≥0.5 µg/mL were confirmed to possess mutations in all three PBP genes. Thirty-five strain for which the MIC of Pc ranged from 0.125 to 0.25µg/mL possessed various PBP gene mutations. The relationships between susceptibilities to 9 ß-lactams of S. pneumoniae and PBP gene mutation were analyzed by multiple regression analysis. Antibiotics were classified into 4 types according to the differences in PBP gene mutation affecting their MIC levels, 1) the MIC of Pc and ampicillin were affected by pbp1a and pbp2b mutations; 2) those of cefotaxime, cefpodoxime, and cefditoren were affected clearly by pbp2x mutation; 3) those of cefaclor and cefdinir were affected more strongly by pbp1a mutation than the pbp2x; and 4) the MIC of faropenem and imipenem were affected strongly by pbp2b mutation. These findings suggest that it may be possible to easily determine whether a S. pneumoniae isolate is susceptible or resistant to Pc, cefotaxime, and other ß-lactams by applying PCR using a combination of primers.

RESUMEN

The Working Group for PRSP was organized through the participation of 40 institutions to investigate the incidence of penicillin (Pc)-resistant Streptococcus pneumoniae (PRSP) in Japan. We collected 2410 S. pneumoniae clinical isolates between October 1994 and March 1995. The susceptibility to Pc, erythromycin, and minocycline was determined by an agar dilution method using Mueller-Hinton agar supplemented with 5% sheep blood. Pc-susceptible S. pneumoniae (PSSP) were defined as bacteria for which the minimum inhibitory concentration (MIC) was ≤0.06µg/mL; Pc-intermediate S. pneumoniae (PISP) as those for which the MIC ranged from 0.125 to 0.25µg/mL; PRSP, as those with a MIC≥0.5µg/mL. The incidence of resistant strains including PISP and PRSP was 41.8% in 1994 and 40.8% in 1995. Logistic regression analysis showed that PRSP was significantly more frequent in infants aged 0 to 2 years old than in the general population and PSSP was significantly more frequent in elderly patients aged 60 or older. The rate of PRSP was significantly higher in the throat than in the sputum. Among 10 regions studied nationwide, PRSP was detected less frequently in the areas of Hokkaido and Hokuriku and more frequently in the areas of Chugoku, Shikoku, and Kyushu. Most PRSP were resistant to erythromycin and minocycline. PSSP serotyping using the capsule-quellung reaction indicated a number of types. In contrast, most PISP and PRSP were serotyped to types 19, 23, and 6.

RESUMEN

The in vitro activities of the ß-lactam and quinolone antibiotics panipenem, cefpodoxime, cefdinir, cefditoren, faropenem, tosufloxacin, levofloxacin and grepafloxacin were compared with similar conventional antibiotics against penicillin-resistant Streptococcus pneumoniae (PRSP). Pneumococcal isolates collected from October 1994 to March 1995 (n=1283) consisted of penicillin-susceptible S. pneumoniae (PSSP; 59.2%), penicillin-intermediately-resistant S. pneumoniae (PISP;11.2%), and PRSP (29.6%). The isolates were highly susceptible to panipenem, faropenem and cefditoren with MIC90 values of 0.125µg/mL, 0.5µg/mL and 0.5µg/mL, respectively. Correlation coefficients for the relationships between the MICs of these ß-lactam agents and that of penicillin G ranged from γ=0.7652 to γ=0.8022. These new ß-lactam agents produced excellent bactericidal responses at concentrations greater than their MICs for PSSP concomitant with appropriate cellular morphologic changes. However, the bactericidal action of these antibiotics against PRSP was less pronounced and fewer instances of cell lysis were observed. The MIC90 of cefpodoxime was similar to that of cefaclor, whereas that of cefdinir was between those of faropenem and cefpodoxime. The MIC distribution of the new quinolone agents showed 1 peak, but the MIC90 values of tosufloxacin and grepafloxacin were both 0.5µg/mL and that of levofloxacin was 2.0µg/mL. Only 1% of all isolates demonstrated cross-resistance to all quinolone agents.