Live Respiratory Syncytial Virus Attenuated by M2-2 Deletion and Stabilized Temperature Sensitivity Mutation 1030s Is a Promising Vaccine Candidate in Children.

BACKGROUND: The safety and immunogenicity of live respiratory syncytial virus (RSV) candidate vaccine, LID/ΔM2-2/1030s, with deletion of RSV ribonucleic acid synthesis regulatory protein M2-2 and genetically stabilized temperature-sensitivity mutation 1030s in the RSV polymerase protein was evaluated in RSV-seronegative children. METHODS: Respiratory syncytial virus-seronegative children ages 6-24 months received 1 intranasal dose of 105 plaque-forming units (PFU) of LID/ΔM2-2/1030s (n = 21) or placebo (n = 11). The RSV serum antibodies, vaccine shedding, and reactogenicity were assessed. During the following RSV season, medically attended acute respiratory illness (MAARI) and pre- and postsurveillance serum antibody titers were monitored. RESULTS: Eighty-five percent of vaccinees shed LID/ΔM2-2/1030s vaccine (median peak nasal wash titers: 3.1 log10 PFU/mL by immunoplaque assay; 5.1 log10 copies/mL by reverse-transcription quantitative polymerase chain reaction) and had ≥4-fold rise in serum-neutralizing antibodies. Respiratory symptoms and fever were common (60% vaccinees and 27% placebo recipients). One vaccinee had grade 2 wheezing with rhinovirus but without concurrent LID/ΔM2-2/1030s shedding. Five of 19 vaccinees had ≥4-fold increases in antibody titers postsurveillance without RSV-MAARI, indicating anamnestic responses without significant illness after infection with community-acquired RSV. CONCLUSIONS: LID/ΔM2-2/1030s had excellent infectivity without evidence of genetic instability, induced durable immunity, and primed for anamnestic antibody responses, making it an attractive candidate for further evaluation.

Hypergammaglobulinemia and Impaired Transplacental Transfer of Respiratory Syncytial Virus Antibody in Papua New Guinea.

BACKGROUND: Passively-acquired respiratory syncytial virus (RSV) neutralizing antibody (Ab) can protect against RSV-associated lower respiratory tract illness. Maternal RSV immunization is, therefore, an attractive strategy for protection of very young infants. Vaccines for this purpose are currently being evaluated in clinical trials, but conditions such as preterm birth, placental malaria, maternal hypergammaglobulinemia and HIV infection might threaten this strategy. Each has been shown to impair transplacental Ab transfer for a variety of pathogens, but RSV-specific data are limited. Work in The Gambia demonstrated that placental malaria impaired transplacental transfer of RSV Ab, but a subsequent study in malaria-endemic Papua New Guinea (PNG) indicated that such associations may have been confounded by hypergammaglobulinemia (IgG > 1700 mg/dL). METHODS: Here we confirm and extend those findings by measuring RSV neutralizing Ab and maternal IgG in sera from a larger cohort of 325 mother/infant pairs in PNG, and demonstrate the applicability of a high-throughput assay for assessment of neutralizing Ab. RESULTS: One-third of mother-infant pairs demonstrated impaired RSV Ab transfer. Infants of hypergammaglobulinemic women were more likely to have both impaired transfer [cord-to-maternal titer ratio <1.0, adjusted odds ratio (OR): 3.36 (95% confidence interval: 1.81-6.30)] and the lowest RSV cord titers [adjusted OR: 5.09 (95% confidence interval: 1.95-13.32, P < 0.001)], but neither outcome was associated with placental malaria. CONCLUSIONS: Once maternal RSV vaccines become available, successful implementation will require clear understanding and mitigation of factors that can impair passive protection, necessitating epidemiologic studies of such relationships ahead of vaccine availability. This study underscores the need to focus on hypergammaglobulinemia as a condition of importance.

Live-Attenuated Respiratory Syncytial Virus Vaccine With Deletion of RNA Synthesis Regulatory Protein M2-2 and Cold Passage Mutations Is Overattenuated.

BACKGROUND: The live respiratory syncytial virus (RSV) candidate vaccine LIDcpΔM2-2 is attenuated through deletion of M2-2 and 5 cold-passage mutations. METHODS: RSV-seronegative children aged 6-24 months received a single intranasal dose of 105 plaque-forming units (PFU) of LIDcpΔM2-2 or placebo. RSV serum antibodies, vaccine infectivity, and reactogenicity were assessed. RESULTS: Four of 11 (36%) vaccinees shed vaccine virus with median peak titers of 1.6 log10 PFU/mL by quantitative culture and 4.5 log10 copies/mL by polymerase chain reaction; 45% had ≥4-fold rise in serum-neutralizing antibodies. Respiratory symptoms or fever were common in vaccinees (64%) and placebo recipients (6/6, 100%). CONCLUSIONS: RSV LIDcpΔM2-2 is overattenuated. Clinical Trial Numbers. NCT02890381, NCT02948127.

Live-Attenuated Respiratory Syncytial Virus Vaccine Candidate With Deletion of RNA Synthesis Regulatory Protein M2-2 is Highly Immunogenic in Children.

Background: Live respiratory syncytial virus (RSV) candidate vaccine LIDΔM2-2 is attenuated by deletion of the RSV RNA regulatory protein M2-2, resulting in upregulated viral gene transcription and antigen expression but reduced RNA replication. Methods: RSV-seronegative children ages 6-24 months received a single intranasal dose of 105 plaque forming units (PFU) of LIDΔM2-2 (n = 20) or placebo (n = 9) (NCT02237209, NCT02040831). RSV serum antibodies, vaccine infectivity, and reactogenicity were assessed. During the following RSV season, participants were monitored for respiratory illness and pre- and post-RSV season serum antibodies. Results: Vaccine virus was shed by 95% of vaccinees (median peak titers of 3.8 log10 PFU/mL by quantitative culture and 6.3 log10 copies/mL by PCR); 90% had ≥4-fold rise in serum neutralizing antibodies. Respiratory symptoms and fever were common in vaccine (95%) and placebo (78%). One vaccinee had grade 2 rhonchi concurrent with vaccine shedding, rhinovirus, and enterovirus. Eight of 19 vaccinees versus 2 of 9 placebo recipients had substantially increased RSV antibody titers after the RSV season without medically attended RSV disease, indicating anamnestic vaccine responses to wild-type RSV without significant illness. Conclusion: LIDΔM2-2 had excellent infectivity and immunogenicity, encouraging further study of vaccine candidates attenuated by M2-2 deletion. Clinical Trials Registration: NCT02237209, NCT02040831.

Impact of Placental Malaria and Hypergammaglobulinemia on Transplacental Transfer of Respiratory Syncytial Virus Antibody in Papua New Guinea.

BACKGROUND: Passively acquired respiratory syncytial virus (RSV) neutralizing antibody protects against RSV-associated lower respiratory infections, but placental malaria (PM) and maternal hypergammaglobulinemia might interfere with transplacental immunoglobulin transport. METHODS: We measured RSV plaque-reduction neutralization (PRN) antibody in 300 full-term maternal/cord serum pairs in 2 cohorts in malaria-endemic Papua New Guinea: Alexishafen (2005-2008) and the Fetal Immunity Study (FIS) (2011-2013). We defined impaired transport as a cord-to-maternal titer ratio <1.0 and a protective RSV PRN titer (PRNT) ≥1:200. RESULTS: PM and hypergammaglobulinemia occurred in 60% and 54% of Alexishafen mothers versus 8% and 9% of FIS mothers, respectively. 34% of Alexishafen and 32% of FIS pairs demonstrated impaired transport. Multivariate modeling revealed significant associations between increasing maternal IgG (log2) and impaired transport (adjusted OR, Alexishafen: 2.68 [1.17-6.14], FIS: 6.94 [1.94-24.8]) but no association with PM. 34% of Alexishafen and 31% of FIS cord PRNTs were <1:200. CONCLUSIONS: Impaired RSV antibody transport was observed in approximately one-third of maternal/cord pairs. Hypergammaglobulinemia, but not PM, was associated with impaired transport, particularly among women with low RSV PRNT. Detection of RSV PRNT <1:200 in one-third of cord sera confirms the need to increase levels of RSV neutralizing antibody in pregnant women through maternal immunization.

Evaluation of a Live-Attenuated Human Parainfluenza Type 1 Vaccine in Adults and Children.

We conducted a phase I clinical trial (clinicaltrials.gov identifier, NCT00641017) of the experimental live-attenuated human parainfluenza virus type 1 (HPIV-1) vaccine rHPIV-1/84/del 170/942A sequentially in 3 groups: adults, HPIV-1-seropositive children, and HPIV-1-seronegative children, the target population for vaccination. rHPIV-1/84/del 170/942A was appropriately restricted in replication in adults and HPIV-1-seropositive children but was overattenuated (ie, insufficiently infectious and immunogenic) for HPIV-1-seronegative children.

A gene deletion that up-regulates viral gene expression yields an attenuated RSV vaccine with improved antibody responses in children.

Respiratory syncytial virus (RSV) is the leading viral cause of severe pediatric respiratory illness, and a safe and effective vaccine for use in infancy and early childhood is needed. We previously showed that deletion of the coding sequence for the viral M2-2 protein (ΔM2-2) down-regulated viral RNA replication and up-regulated gene transcription and antigen synthesis, raising the possibility of development of an attenuated vaccine with enhanced immunogenicity. RSV MEDI ΔM2-2 was therefore evaluated as a live intranasal vaccine in adults, RSV-seropositive children, and RSV-seronegative children. When results in RSV-seronegative children were compared to those achieved with the previous leading live attenuated RSV candidate vaccine, vaccine virus shedding was significantly more restricted, yet the postvaccination RSV-neutralizing serum antibody achieved [geometric mean titer (GMT) = 1:97] was significantly greater. Surveillance during the subsequent RSV season showed that several seronegative RSV MEDI ΔM2-2 recipients had substantial antibody rises without reported illness, suggesting that the vaccine was protective yet primed for anamnestic responses to RSV. Rational design appears to have yielded a candidate RSV vaccine that is intrinsically superior at eliciting protective antibody in RSV-naïve children and highlights an approach for the development of live attenuated RSV vaccines.

Evaluation of fast-track diagnostics and TaqMan array card real-time PCR assays for the detection of respiratory pathogens.

Several commercial assays are now available to detect the nucleic acid of multiple respiratory pathogens from a single specimen. Head-to-head comparisons of such assays using a single set of standard specimens provide additional information about key assay parameters such as sensitivity, specificity and lower limits of detection, and help to inform the decision regarding which method to use. We evaluated two real-time PCR platforms: the Fast-track Diagnostics® (FTD) multiplex respiratory panel and a TaqMan array card (TAC) for simultaneous uniplex detection of multiple respiratory pathogens. Two sets of samples were used to evaluate the assays. One set was created by spiking pooled nasal wash or phosphate buffered saline with specified volumes of known concentrations of virus and/or bacteria. Clinical nasal wash specimens from children with lower respiratory tract illness comprised the other set. Thirteen pathogen targets were compared between the two platforms. Testing with a validation panel of spiked samples revealed a sensitivity of 96.1% and 92.9% for the FTD and TAC assays, respectively. Specificity could not be reliably calculated due to a suspected contamination of the sample substrate. Inter-assay agreement was high (> 95%) for most targets. Previously untested clinical specimens tested by both assays revealed a high percent agreement (> 95%) for all except rhinovirus, enterovirus and Streptococcus pneumoniae. Limitations of this evaluation included extraction of the validation samples by two different methods and the evaluation of the assays in different laboratories. However, neither of these factors significantly impacted inter-assay agreement for these sets of samples, and it was demonstrated that both assays could reliably detect clinically relevant concentrations of bacterial and viral pathogens.

Experimental infection of adults with recombinant wild-type human metapneumovirus.

BACKGROUND: Human metapneumovirus (HMPV) causes lower respiratory tract infections in young children. rHMPV-SHs is a recombinant HMPV (rHMPV) based on a biologically derived wild-type HMPV strain. We characterized its infectivity and immunogenicity in healthy adults to determine whether it would be suitable for use as the parent virus for the development of live attenuated rHMPV vaccines. METHODS: Twenty-one healthy adults were inoculated intranasally with 10(6) plaque-forming units of rHMPV-SHs. Respiratory symptoms and shedding of challenge virus were assessed. Neutralizing antibody responses, serum immunoglobulin G and A, and nasal wash specimen immunoglobulin A antibody responses to the HMPV F protein were also measured. Induction of nasal cytokines was assessed with electrochemiluminescence assays. RESULTS: Nine subjects (43%) were infected with challenge virus as determined by virus detection and/or ≥4-fold rise in serum antibody titers. Peak viral shedding occurred on days 7-9 after infection. Four weeks after inoculation, 35% of subjects had any antibody response. Six of 9 infected subjects had respiratory symptoms, and 3 had headache after inoculation. Cytokine patterns differed considerably between subjects with similar illness severity and viral shedding. CONCLUSIONS: The rHMPV-SHs virus is infectious and is a suitable parent virus for development of live-attenuated HMPV vaccine candidates. Clinical Trials Registration. NCT01109329.

Attenuation of live respiratory syncytial virus vaccines is associated with reductions in levels of nasal cytokines.

BACKGROUND: Respiratory syncytial virus (RSV) is a leading cause of lower respiratory tract illness (LRTI) in children. Several promising live-attenuated RSV vaccines are in development. Defining additional markers of attenuation could enhance clinical trials. METHODS: We used clinical data, virologic data, and nasal wash (NW) specimens from 20 RSV-naive children enrolled in studies of 4 live-attenuated RSV vaccines. Seven received minimally attenuated cpts248/955 or cpts530/1009 (group 1), 6 received moderately attenuated cpts248/404 (group 2), and 7 received highly attenuated rA2cp248/404/1030/ΔSH (group 3). NW specimens were tested for cytokines and chemokines via an electrochemiluminescence biosensor assay. RESULTS: Group 1 exhibited 1 instance of LRTI and significantly higher rates of fever than groups 2 or 3; there were no significant differences in peak titers of vaccine virus in NW specimens. In contrast, levels of interferon γ, interleukin 1ß, interleukin 2, interleukin 6, and interleukin 13 were significantly greater in NW specimens from group 1, compared with those from group 3. Maximum increases in levels of most cytokines occurred after peak viral replication but coincided with clinical illness. CONCLUSIONS: Substantial increases in proinflammatory, antiinflammatory, T-helper 1, T-helper 2, and regulatory cytokines were detected in children who received minimally attenuated live RSV vaccines but not in children who received highly attenuated vaccines. Levels of cytokines in NW specimens may be useful biomarkers of attenuation for live RSV vaccines.

An open-label phase I trial of a live attenuated H2N2 influenza virus vaccine in healthy adults.

BACKGROUND: Live attenuated influenza vaccines (LAIV) against a variety of strains of pandemic potential are being developed and tested. We describe the results of an open-label phase I trial of a live attenuated H2N2 virus vaccine. OBJECTIVES: To evaluate the safety, infectivity, and immunogenicity of a live attenuated H2N2 influenza virus vaccine. PARTICIPANTS/METHODS: The A/Ann Arbor/6/60 (H2N2) virus used in this study is the attenuated, cold-adapted, temperature-sensitive strain that provides the genetic backbone of seasonal LAIV (MedImmune). We evaluated the safety, infectivity, and immunogenicity of two doses of 10(7) TCID(50) of this vaccine administered by nasal spray 4 weeks apart to normal healthy seronegative adults. RESULTS: Twenty-one participants received a first dose of the vaccine; 18 participants received a second dose. No serious adverse events occurred during the trial. The most common adverse events after vaccination were headache and musculoskeletal pain. The vaccine was restricted in replication: 24% and 17% had virus detectable by culture or rRT-PCR after the first and second dose, respectively. Antibody responses to the vaccine were also restricted: 24% of participants developed an antibody response as measured by either hemagglutination-inhibition assay (10%), or ELISA for H2 HA-specific serum IgG (24%) or IgA (16%) after either one or two doses. None of the participants had a neutralizing antibody response. Vaccine-specific IgG-secreting cells as measured by enzyme-linked immunospot increased from a mean of 0·5 to 2·0/10(6) peripheral blood mononuclear cells (PBMCs); vaccine-specific IgA-secreting cells increased from 0·1 to 0·5/10(6) PBMCs. CONCLUSIONS: The live attenuated H2N2 1960 AA ca vaccine demonstrated a safety profile consistent with seasonal trivalent LAIV but was restricted in replication and minimally immunogenic in healthy seronegative adults.

Evaluation of two chimeric bovine-human parainfluenza virus type 3 vaccines in infants and young children.

Human parainfluenza virus type 3 (HPIV3) is an important cause of lower respiratory tract illness in children, yet a licensed vaccine or antiviral drug is not available. We evaluated the safety, tolerability, infectivity, and immunogenicity of two intranasal, live-attenuated HPIV3 vaccines, designated rHPIV3-N(B) and rB/HPIV3, that were cDNA-derived chimeras of HPIV3 and bovine PIV3 (BPIV3). These were evaluated in adults, HPIV3 seropositive children, and HPIV3 seronegative children. A total of 112 subjects participated in these studies. Both rB/HPIV3 and rHPIV3-N(B) were highly restricted in replication in adults and seropositive children but readily infected seronegative children, who shed mean peak virus titers of 10(2.8) vs. 10(3.7)pfu/mL, respectively. Although rB/HPIV3 was more restricted in replication in seronegative children than rHPIV3-N(B), it induced significantly higher titers of hemagglutination inhibition (HAI) antibodies against HPIV3. Taken together, these data suggest that the rB/HPIV3 vaccine is the preferred candidate for further clinical development.

The cDNA-derived investigational human parainfluenza virus type 3 vaccine rcp45 is well tolerated, infectious, and immunogenic in infants and young children.

BACKGROUND: Human parainfluenza virus type 3 (HPIV3) is an important yet underappreciated cause of lower respiratory tract illness in children, and a licensed vaccine is not yet available. METHODS: A live-attenuated investigational HPIV3 vaccine virus designated rcp45 was derived from cDNA by using reverse genetics. rcp45 is genetically similar to the biologically derived cp45 vaccine virus and contains all of the known attenuating mutations of cp45, but has the advantage of a short, well-characterized passage history. We evaluated the tolerability, infectivity, and immunogenicity of 2 intranasal doses of rcp45 administered 4 to 10 weeks apart in a placebo-controlled, double-blind trial. A total of 45 infants and children between 6 and 36 months of age participated in this study. Tolerability and antibody responses to vaccine or placebo were assessed in all recipients. Infectivity was assessed by quantitation of vaccine virus shedding in a subset of vaccinated children. RESULTS: rcp45 was well tolerated and highly infectious in HPIV3-seronegative children. A second dose of vaccine administered 4 to 10 weeks after the first dose was restricted in replication and did not boost serum antibody responses. The stability of 9 cp45 mutations, including the 6 major attenuating mutations, was examined and confirmed for viral isolates from 10 children. CONCLUSIONS: The level of attenuation and immunogenicity of cDNA-derived rcp45 is comparable to what was previously observed with the biologically derived cp45 vaccine, and preliminary data suggest that the attenuating mutations in this vaccine virus are genetically stable. Continued clinical development of rcp45 is warranted.

An open label Phase I trial of a live attenuated H6N1 influenza virus vaccine in healthy adults.

BACKGROUND: We describe the results of an open label Phase I trial of a live attenuated H6N1 influenza virus vaccine (ClinicalTrials.gov Identifier: NCT00734175). METHODS AND FINDINGS: We evaluated the safety, infectivity, and immunogenicity of two doses of 10(7) TCID(50) of the H6N1 Teal HK 97/AA ca vaccine, a cold-adapted and temperature sensitive live, attenuated influenza vaccine (LAIV) in healthy seronegative adults. Twenty-two participants received the first dose of the vaccine, and 18 received the second dose of vaccine 4 weeks later. The vaccine had a safety profile similar to that of other investigational LAIVs bearing avian hemagglutinin (HA) and neuraminidase (NA) genes. The vaccine was highly restricted in replication: two participants had virus detectable by rRT-PCR beyond day 1 after each dose. Antibody responses to the vaccine were also restricted: 43% of participants developed a serum antibody response as measured by any assay: 5% by hemagglutination-inhibition assay, 5% by microneutralization assay, 29% by ELISA for H6 HA-specific IgG and 24% by ELISA for H6 HA specific IgA after either 1 or 2 doses. Following the second dose, vaccine specific IgG and IgA secreting cells as measured by ELISPOT increased from a mean of 0.6 to 9.2/10(6) PBMCs and from 0.2 to 2.2/10(6) PBMCs, respectively. CONCLUSION: The H6N1 LAIV had a safety profile similar to that of LAIV bearing other HA and NA genes, but was highly restricted in replication in healthy seronegative adults. The H6N1 LAIV was also not as immunogenic as the seasonal LAIV.

Evaluation of two live attenuated cold-adapted H5N1 influenza virus vaccines in healthy adults.

BACKGROUND: Development of live attenuated influenza vaccines (LAIV) against avian viruses with pandemic potential is an important public health strategy. METHODS AND FINDINGS: We performed open-label trials to evaluate the safety, infectivity, and immunogenicity of H5N1 VN 2004 AA ca and H5N1 HK 2003 AA ca. Each of these vaccines contains a modified H5 hemagglutinin and unmodified N1 neuraminidase from the respective wild-type (wt) parent virus and the six internal protein gene segments of the A/Ann Arbor/6/60 cold-adapted (ca) master donor virus. The H5N1 VN 2004 AA ca vaccine virus was evaluated at dosages of 10(6.7) TCID(50) and 10(7.5) TCID(50), and the H5N1 HK 2003 AA ca vaccine was evaluated at a dosage of 10(7.5) TCID(50). Two doses were administered intranasally to healthy adults in isolation at 4-8 week intervals. Vaccine safety was assessed through daily examinations and infectivity was assessed by viral culture and by realtime reverse transcription-polymerase chain reaction testing of nasal wash (NW) specimens. Immunogenicity was assessed by measuring hemagglutination-inhibition (HI) antibodies, neutralizing antibodies, and IgG or IgA antibodies to recombinant (r)H5 VN 2004 hemagglutinin (HA) in serum or NW. Fifty-nine participants were enrolled: 21 received 10(6.7) TCID(50) and 21 received 10(7.5) TCID(50) of H5N1 VN 2004 AA ca and 17 received H5N1 HK 2003 AA ca. Shedding of vaccine virus was minimal, as were HI and neutralizing antibody responses. Fifty-two percent of recipients of 10(7.5) TCID(50) of H5N1 VN 2004 AA ca developed a serum IgA response to rH5 VN 2004 HA. CONCLUSIONS: The live attenuated H5N1 VN 2004 and HK 2003 AA ca vaccines bearing avian H5 HA antigens were very restricted in replication and were more attenuated than seasonal LAIV bearing human H1, H3 or B HA antigens. The H5N1 AA ca LAIV elicited serum ELISA antibody but not HI or neutralizing antibody responses in healthy adults. (ClinicalTrials.gov Identifiers: NCT00347672 and NCT00488046).

A live attenuated H9N2 influenza vaccine is well tolerated and immunogenic in healthy adults.

Development of live attenuated influenza vaccines (LAIV) against avian strains with pandemic potential is an important public-health strategy. Either 1 or 2 10(7)-TCID(50) doses of H9N2 LAIV A/chicken/Hong Kong/G9/97 were administered intranasally to 50 adults in isolation; 41 participants were H9N2 seronegative, 24 of whom received 2 doses. The vaccine was well tolerated; vaccine shedding was minimal. After 2 doses, 92% of H9-seronegative participants had > or = 4-fold increases in hemagglutination-inhibition antibody, and 79% had > or = 4-fold increases in neutralizing antibody; 100% had responses detected by at least 1 assay. Although replication of the H9N2 LAIV was restricted, 2 doses were immunogenic in H9N2-seronegative adults. Trial registration. ClinicalTrials.gov identifier: NCT00110279 .

Young infants can develop protective levels of neutralizing antibody after infection with respiratory syncytial virus.

Humoral immunity protects against severe respiratory syncytial virus (RSV) disease, but the range and magnitude of antibody responses in RSV-naive children after RSV infection have not been completely defined. We evaluated RSV-neutralizing antibody and immunoglobulin G responses to RSV F and G glycoproteins in 65 RSV-naive Navajo and White Mountain Apache children aged 0-24 months who were hospitalized with RSV infection. In these children, antibody responses developed against RSV F and G and the central conserved region of RSV G. Twenty-seven of 41 infants <6 months old developed reciprocal log(2) RSV neutralizing antibody titers > or =8.0, which correlate with protection of the lower respiratory tract. Multivariate analysis demonstrated that the level of preexisting neutralizing antibody at infection, not age, was the most important factor influencing this response. RSV can induce substantial neutralizing antibody responses in young infants when the titer of preexisting antibodies is low.

The role of neutralizing antibodies in protection of American Indian infants against respiratory syncytial virus disease.

BACKGROUND: Navajo and White Mountain Apache infants have respiratory syncytial virus (RSV) hospitalization rates 2-5 times that of the general U.S. infant population. To evaluate whether these high rates can be attributable to low concentrations of maternally derived RSV neutralizing antibodies, we conducted a case-control study. METHODS: Study subjects enrolled in a prospective, hospital-based surveillance study of RSV disease and a group randomized clinical trial of a 7-valent pneumococcal conjugate vaccine. Cord blood specimens were assayed for neutralizing RSV antibody titers. Infants hospitalized with a respiratory illness had a nasal aspirate obtained to determine whether RSV was present. Infants with an RSV respiratory hospitalization were matched by date of birth and geographic location to infants who did not have an RSV hospitalization before 6 months of age. RESULTS: For every 1 log2 increase in titer of cord blood RSV neutralizing antibodies there was a 30% reduced risk of hospitalization with RSV (OR = 0.69, P = 0.003). However, among infants hospitalized with RSV, there was no association between cord blood RSV neutralizing antibody and the severity of the RSV illness. CONCLUSIONS: These findings indicate that American Indian infants with high concentrations of maternally derived RSV neutralizing antibodies are protected from RSV hospitalization before 6 months of age. However, these antibodies do not modify the severity of illness once disease has occurred. The basis for elevated rates of RSV disease among American Indian infants cannot be attributed to a failure of maternal RSV neutralizing antibodies to confer protection.

C5 modulates airway hyperreactivity and pulmonary eosinophilia during enhanced respiratory syncytial virus disease by decreasing C3a receptor expression.

Enhanced respiratory syncytial virus disease, a serious pulmonary disorder that affected recipients of an inactivated vaccine against respiratory syncytial virus in the 1960s, has delayed the development of vaccines against the virus. The enhanced disease was characterized by immune complex-mediated airway hyperreactivity and a severe pneumonia associated with pulmonary eosinophilia. In this paper, we show that complement factors contribute to enhanced-disease phenotypes. Mice with a targeted disruption of complement component C5 affected by the enhanced disease displayed enhanced airway reactivity, lung eosinophilia, and mucus production compared to wild-type mice and C5-deficient mice reconstituted with C5. C3aR expression in bronchial epithelial and smooth muscle cells in the lungs of C5-deficient mice was enhanced compared to that in wild-type and reconstituted rodents. Treatment of C5-deficient mice with a C3aR antagonist significantly attenuated airway reactivity, eosinophilia, and mucus production. These results indicate that C5 plays a crucial role in modulating the enhanced-disease phenotype, by affecting expression of C3aR in the lungs. These findings reveal a novel autoregulatory mechanism for the complement cascade that affects the innate and adaptive immune responses.

The cysteine-rich region of respiratory syncytial virus attachment protein inhibits innate immunity elicited by the virus and endotoxin.

The attachment protein (glycoprotein) of respiratory syncytial virus (RSV) has long been associated with disease potentiation and respiratory symptoms. The glycoprotein has a conserved cysteine-rich region (GCRR) whose function is unknown and which is not necessary for efficient viral replication. In this report, we show that the GCRR is a powerful inhibitor of the innate immune response against RSV, and that early secretion of glycoprotein is critical to modulate inflammation after RSV infection. Importantly, the GCRR is also a potent inhibitor of cytokine production mediated by several TLR agonists, indicating that this peptide sequence displays broad antiinflammatory properties. These findings have important implications for RSV pathogenesis and describe an inhibitor of TLR-mediated inflammatory responses that could have clinical applications.