Viral etiology of acute respiratory infections with cough in infancy: a community-based birth cohort study

BACKGROUND: Acute respiratory infections (ARI) are a major cause of morbidity in infancy worldwide, with cough and wheeze being alarming symptoms to parents. We aimed to analyze in detail the viral aetiology of ARI with such symptoms in otherwise healthy infants, including rhinoviruses and recently discovered viruses such as human metapneumovirus (HMPV), coronavirus NL63 and HKU1, and human bocavirus (HBoV). METHODS: We prospectively followed 197 unselected infants during their first year of life and assessed clinical symptoms by weekly standardized interviews. At the first ARI with cough or wheeze, we analyzed nasal swabs by sensitive individual real time polymerase chain reaction assays targeting 16 different respiratory viruses. RESULTS: All 112 infants who had an ARI had cough, and 39 (35%) had wheeze. One or more respiratory viruses were found in 88 of 112 (79%) cases. Fifteen (17%) dual and 3 (3%) triple infections were recorded. Rhino- (23% of all viruses) and coronaviruses (18%) were most common, followed by parainfluenza viruses (17%), respiratory syncytial virus (RSV) (16%), HMPV (13%), and HBoV (5%). Together rhinoviruses, coronaviruses, HMPV, and HBoV accounted for 60% (65 of 109) of viruses. Although symptom scores and need for general practitioner (GP) consultations were highest in infants infected with RSV, they were similar in infants infected with other viruses. Viral shedding at 3 weeks occurred in 20% of cases. CONCLUSIONS: Rhinoviruses, coronaviruses, HMPV, and HBoV are common pathogens associated with respiratory symptoms in otherwise healthy infants. They should be considered in the differential diagnosis of the aetiology of ARI in this age group.

The importance of pneumococcal capsule in inate immunity and biofilm formation

Chapter 1 gives an overview about Streptococcus pneumoniae, its role as a human pathogen and its virulence factors. Additionally, biofilm development and its relevance in clinics are introduced, and the innate immune response to pneumococcus as well as bacterial-viral interactions in the upper respiratory tract are also discussed. Chapter 2 emphasizes the three main topics of this thesis: the role of capsule and pneumolysin in the immune response in the respiratory tract, biofilm formation of S. pneumoniae serotypes and commensal streptococci in vitro, and host innate immune responses to RSV and S. pneumoniae during in vitro co-infections. Aims and hypotheses are provided here. Chapter 3 is divided into two parts: First, the release of the pro-inflammatory cytokines CXCL8 and IL-6 from the human pharyngeal epithelial cell line Detroit 562 and from human bronchial epithelial cells (iHBEC) is described in response to S. pneumoniae. Capsule was shown to suppress the release of both cytokines in both cell lines tested, but release was much less from iHBEC cells. During intranasal colonization of mice, suppression of CXCL8 release by the capsule was also observed in vivo, but the effect was only measured in the absence of pneumolysin. Long term, stable nasopharyngeal carriage in a mouse model resulted in the dissemination of nonencapsulated pneumococci into the lungs, whereas encapsulated strains remained in the nasopharynx. The S. pneumoniae capsule thus plays a role in modulation of the pro-inflammatory immune response in the respiratory tract. Second, results on immunological cells and immune regulation in a long term, stable nasopharyngeal carriage mouse model are presented. Mice were infected with encapsulated or nonencapsulated pneumococcal strains, and after 1, 3, 8 and 15 days, were sacrificed to evaluate the numbers of CD45+ cells, neutrophils, macrophages, FoxP3+ regulatory T-cells and CD3+ T-cells in the nasal mucosa as well as the amount of secreted IL-10 in the nasopharynx. Nasopharyngeal colonization which is effectively silent resulted in the stimulation of FoxP3+ regulatory T-cells and IL-10 release associated with immune homeostasis, whereas lung infiltration was required to increase the number of neutrophils and macrophages resulting in a stronger innate immune response in the nasal mucosa. Chapter 4 contains results of mono- and co-stimulation using RSV and pneumococci or pneumococcal virulence factors on the human bronchial epithelial cell line BEAS-2B. An increase in CXCL8 and IL-6 levels was measured for mixed stimulations of RSV and pneumococcus when encapsulated bacteria were used. Increasing pneumolysin concentrations resulted in enhanced CXCL8 levels. Priming of bronchial epithelial cells with RSV opens the door for more severe pneumococcal infections. Chapter 5 is composed of two parts: The first part describes initial biofilm formation of serotypes 6B and 7F in a static model in vitro. Biofilms of both serotypes contained SCVs, but only serotype 6B increased in SCV formation between 16 and 65h of incubation. SCV stability was tested by passaging clones in complex medium, where SCV production is not associated with advantages in growth. Serotype 6B lost the SCV phenotype indicating a fast adaptation to a changing nutritional environment. Limitations of our in vitro model are discussed. The second part is about initial biofilm formation of mixed culture growth of S. pneumoniae with commensal streptococci. Competition dominates this process. S. oralis and pneumococcus compete for nutrients, whereas mixed species growth of S. mitis or S. pseudopneumoniae with S. pneumoniae is mainly influenced by other factors. In Chapter 6 the findings of chapters 3, 4 and 5 are discussed and an outlook for further studies is provided. Chapters 7, 8, 9, 10 and 11 contain the references, the acknowledgements, the curriculum vitae, the appendix and the declaration of originality.

The burden of parainfluenza virus infection in patients with hematological malignancy and hematopoietic stem cell transplant (HSCT) recipients in the absence of active immunization and approved therapy: The role of infection control

Background. Community respiratory viruses, mainly RSV and influenza, are significant causes of morbidity and mortality in patients with leukemia and HSCT recipients. The data on impact of PIV infections in these patients is lacking. Methods. We reviewed the records of patients with leukemia and HSCT recipients who developed PIV infection from Oct'02–Nov'07 to determine the outcome of such infections. Results. We identified 200 patients with PIV infections including 80(40%) patients with leukemia and 120 (60%) recipients of HSCT. Median age was 55 y (17-84 y). As compared to HSCT recipients, patients with leukemia had higher APACHE II score (14 vs. 10, p<0.0001); were more likely to have ANC<500 (48% vs. 10%, p<0.0001) and ALC<200 (45% vs. 23.5%, p=0.02). PIV type III was the commonest isolate (172/200, 86%). Most patients 141/200 (70%) had upper respiratory infection (URI), and 59/200 (30%) had pneumonia at presentation. Patients in leukemia group were more likely to require hospitalization due to PIV infection (77% vs. 36% p=0.0001) and were more likely to progress to pneumonia (61% vs. 39%, p=0.002). Fifty five patients received aerosolized ribavirin and/or IVIG. There were no significant differences in the duration of symptoms, length of hospitalization, progression to pneumonia or mortality between the treated verses untreated group. The clinical outcome was unknown in 13 (6%) patients. Complete resolution of symptoms was noted in 91% (171/187) patients and 9% (16/187) patients died. Mortality rate was 17% (16/95) among patients who had PIV pneumonia, with no significant difference between leukemia and HSCT group (16% vs. 17%). The cause of death was acute respiratory failure and/or multi-organ failure in (13, 81%) patients. Conclusions. Patients with leukemia and HSCT could be at high risk for serious PIV infections including PIV pneumonia. Treatment with aerosolized ribavirin and/or IVIG may not have significant effect on the outcome of PIV infection.^

Respiratory syncytial virus infection in hematopoietic stem cell transplant patients

Respiratory Syncytial Virus (RSV) is a major cause of respiratory tract infections in immunocompromised patients such as children less than 2 years, premature infants with congenital heart disease and chronic lung disease, elderly patients and patients who have undergone hematopoietic stem cell transplant (HSCT). HSCT patients are at high risk of RSV infection, at increased risk of developing pneumonia, and RSV-related mortality. Immunodeficiency can be a major risk factor for severe infection & mortality. Therapy of RSV infection with Ribavirin, Palivizumab and Immunoglobulin has shown to reduce the risk of progression to LRI and mortality, especially if initiated early in the disease. Data on RSV infection in HSCT patients is limited, especially at various levels of immunodeficiency. 323 RSV infections in HSCT patients have been identified between 1/1995 and 8/2009 at University of Texas M D Anderson Cancer Center (UTMDACC). In this proposed study, we attempted to analyze a de-identified database of these cases and describe the epidemiologic characteristics of RSV infection in HSCT patients, the course of the infection, rate of development of pneumonia and RSV-related mortality in HSCT patients at UTMDACC.^ Key words: RSV infections, HSCT patients ^

Seasonality of respiratory syncytial virus infection in Texas

Respiratory syncytial virus (RSV) is a common cause of respiratory infection in infants and children that can result in bronchiolitis or pneumonia. Each year in the United States, it causes up to 400 deaths and 125,000 hospitalizations among children less than one year of age. RSV is transmitted by direct or close contact with contaminated secretions, which may involve droplets and fomites. Monthly administration of a monoclonal RSV antibody, palivizumab (Synagis™, MedImmune, Gaithersburg, MD), in premature infants, infants with chronic lung disease, or congenital heart disease has been shown to significantly reduce the risk of severe RSV infection. The Centers for Disease Control and Prevention's (CDC) National Respiratory and Enteric Virus Surveillance System (NREVSS) is a laboratory based passive reporting system that collects state, regional, and national RSV data. The CDC defines the RSV season onset as “the first of 2 consecutive weeks during which the mean percentage of specimens testing positive for RSV antigen is 10%.” RSV season offset is defined as the last of 2 consecutive weeks during which the percentage of positive specimens is less than or equal to 10%. Annual RSV epidemics generally occur during the winter and early spring months, but the RSV season is known to vary by national regions. Precise delineation of the RSV epidemiology by region could maximize protection from RSV and minimize the cost of RSV immune prophylaxis. ^ The purpose of this thesis is to define the RSV season in Texas over time; compare the RSV season of the state of Texas and its regions with the national norms; and to compare RSV seasonality between the various regions in Texas. ^ This study was a retrospective analysis of data reported to NREVSS to evaluate potential disparities in the onset weeks, offset weeks, and duration of the annual RSV season in Texas. Data were collected from 70 reporting sites, and includes information from the 2004–2005 to 2009–2010 RSV seasons. ^ The observed median onset (week 44) and offset week (week 8) for the Texas were consistent with national estimates for the South. Regional estimates and statistical analysis suggested that the RSV season in Texas would be better represented by regions. Regional seasonal comparisons revealed considerable variation in season offset and duration between many of the geographic regions within Texas. This trend should be studied further.^

Un modelo no paramétrico de evaluación de la eficiencia y la gestión de las redes sociales virtuales : una aplicación a las empresas del sector de las telecomunicaciones en España

Este artículo analiza la relación entre la eficiencia productiva y las Redes Sociales Virtuales (RSV) en las empresas de telecomunicaciones en España. En una primera etapa, se aplica el análisis envolvente de datos (DEA) incorporando varios indicadores de actividad ?Social Media?. En una segunda etapa, se utiliza una regresión logística para caracterizar las empresas eficientes. Los resultados muestran que la capacidad de absorción y utilización de las RSV es un factor determinante en la mejora de la eficiencia productiva. La utilización combinada y las distintas capacidades de gestión de las RSV permiten identificarlas como un recurso heterogéneo. Este trabajo presenta un modelo para la evaluación del desempeño estratégico al abordar su presencia y actividad en RSV. ABSTRACT. This paper analyzes the relationship between the productive efficiency and the Online Social Networks - OSN in the Spanish telecommunications firms. First, a data envelopment analysis (DEA) is used and several indicators of business "Social Media" activities are incorporated. In a second stage, a logistic regression model regression is applied to characteri ze the efficient enterprises. Results show that the company's ability to absorb and utilize this OSN is a key factor in improving the productive efficiency. These results on the combined use and different management capabilities of OSN point to a definitio n of OSN as a heterogeneous resource. This paper presents a model for assessing the strategic performance to address their presence and activity in OSN.

Interferon γ expressed by a recombinant respiratory syncytial virus attenuates virus replication in mice without compromising immunogenicity

Interferon γ (IFN-γ) has pleiotropic biological effects, including intrinsic antiviral activity as well as stimulation and regulation of immune responses. An infectious recombinant human respiratory syncytial virus (rRSV/mIFN-γ) was constructed that encodes murine (m) IFN-γ as a separate gene inserted into the G-F intergenic region. Cultured cells infected with rRSV/mIFN-γ secreted 22 μg mIFN-γ per 106 cells. The replication of rRSV/mIFN-γ, but not that of a control chimeric rRSV containing the chloramphenicol acetyl transferase (CAT) gene as an additional gene, was 63- and 20-fold lower than that of wild-type (wt) RSV in the upper and lower respiratory tract, respectively, of mice. Thus, the attenuation of rRSV/mIFN-γ in vivo could be attributed to the activity of mIFN-γ and not to the presence of the additional gene per se. The mice were completely resistant to subsequent challenge with wt RSV. Despite its growth restriction, infection of mice with rRSV/mIFN-γ induced a level of RSV-specific antibodies that, on day 56, was comparable to or greater than that induced by infection with wt RSV. Mice infected with rRSV/mIFN-γ developed a high level of IFN-γ mRNA and an increased amount of interleukin 12 p40 mRNA in their lungs, whereas other cytokine mRNAs tested were unchanged compared with those induced by wt RSV. Because attenuation of RSV typically is accompanied by a reduction in immunogenicity, expression of IFN-γ by an rRSV represents a method of attenuation in which immunogenicity can be maintained rather than be reduced.

A role for ubiquitin ligase recruitment in retrovirus release

Retroviral Gag polyproteins have specific regions, commonly referred to as late assembly (L) domains, which are required for the efficient separation of assembled virions from the host cell. The L domain of HIV-1 is in the C-terminal p6gag domain and contains an essential P(T/S)AP core motif that is widely conserved among lentiviruses. In contrast, the L domains of oncoretroviruses such as Rous sarcoma virus (RSV) have a more N-terminal location and a PPxY core motif. In the present study, we used chimeric Gag constructs to probe for L domain activity, and observed that the unrelated L domains of RSV and HIV-1 both induced the appearance of Gag-ubiquitin conjugates in virus-like particles (VLP). Furthermore, a single-amino acid substitution that abolished the activity of the RSV L domain in VLP release also abrogated its ability to induce Gag ubiquitination. Particularly robust Gag ubiquitination and enhancement of VLP release were observed in the presence of the candidate L domain of Ebola virus, which contains overlapping P(T/S)AP and PPxY motifs. The release defect of a minimal Gag construct could also be corrected through the attachment of a peptide that serves as a physiological docking site for the ubiquitin ligase Nedd4. Furthermore, VLP formation by a full-length Gag polyprotein was sensitive to lactacystin, which depletes the levels of free ubiquitin through inhibition of the proteasome. Our findings suggest that the engagement of the ubiquitin conjugation machinery by L domains plays a crucial role in the release of a diverse group of enveloped viruses.

A truncated mutant (residues 58-140) of the hepatitis B virus X protein retains transactivation function.

The hepatitis B virus X protein (HBx) sequence (154 aa) has been divided into six regions (A-F) based on its sequence homology with X proteins of other mammalian hepadnaviruses. Regions A, C, and E are more conserved and include all the four conserved cysteines (C7, C61, C69, and C137). To localize the regions of HBx important for transactivation, a panel of 10 deletion mutants (X5-X14) and 4 single point mutants (X1-X4), each corresponding to a conserved cysteine residue, was constructed by site-directed mutagenesis. A HBx-specific monoclonal antibody was developed and used to confirm the expression of mutants by Western blot. Transactivation property of the HBx mutants was studied on Rous sarcoma virus-long terminal repeat (RSV-LTR) in transient transfection assays. We observed that deletion of the most conserved region A or substitution of the N-terminal cysteine (C7) had no effect on transactivation. Deletion of the nonconserved regions B or F also had no deleterious effects. Deletions of regions C and D resulted in a significant loss of function. Substitution of both C61 and C69 present in region C, caused almost 90% loss of activity that could be partially overcome by transfecting more expression plasmid. The fully conserved 9 amino acid segment (residues 132 to 140) within region E including C137 appeared to be crucial for its activity. Finally, a truncated mutant X15 incorporating only regions C to E (amino acids 58-140) was able to stimulate the RSV-LTR quite efficiently, suggesting a crucial role played by this domain in transactivation function.

Peptides from conserved regions of paramyxovirus fusion (F) proteins are potent inhibitors of viral fusion.

The synthetic peptides DP-107 and DP-178 (T-20), derived from separate domains within the human immunodeficiency virus type 1 (HIV-1) transmembrane (TM) protein, gp4l, are stable and potent inhibitors of HIV-1 infection and fusion. Using a computer searching strategy (computerized antiviral searching technology, C.A.S.T.) based on the predicted secondary structure of DP-107 and DP-178 (T-20), we have identified conserved heptad repeat domains analogous to the DP-107 and DP-178 regions of HIV-1 gp41 within the glycoproteins of other fusogenic viruses. Here we report on antiviral peptides derived from three representative paramyxoviruses, respiratory syncytial virus (RSV), human parainfluenza virus type 3 (HPIV-3), and measles virus (MV). We screened crude preparations of synthetic 35-residue peptides, scanning the DP-178-like domains, in antiviral assays. Peptide preparations demonstrating antiviral activity were purified and tested for their ability to block syncytium formation. Representative DP-178-like peptides from each paramyxovirus blocked homologous virus-mediated syncytium formation and exhibited EC50 values in the range 0.015-0.250 microM. Moreover, these peptides were highly selective for the virus of origin. Identification of biologically active peptides derived from domains within paramyxovirus F1 proteins analogous to the DP-178 domain of HIV-1 gp4l is compelling evidence for equivalent structural and functional features between retroviral and paramyxoviral fusion proteins. These antiviral peptides provide a novel approach to the development of targeted therapies for paramyxovirus infections.

Isolation of virus-neutralizing RNAs from a large pool of random sequences.

RNA and ribonuclease-resistant RNA analogs that bound and neutralized Rous sarcoma virus (RSV) were isolated from a large pool of random sequences by multiple cycles of in vitro selection using infectious viral particles. The selected RNA pool of RSV-binding sequences at a concentration of 0.16 microM completely neutralized the virus. Of 19 sequences cloned from the selected pool, 5 inhibited RSV infection. The selected RNA and RNA analogs were shown to neutralize RSV by interacting with the virus, rather than by adversely affecting the host cells. The selection of the anti-RSV RNA and RNA analogs by intact virions immediately suggests the potential application of this approach to develop RNA and RNA analogs as inhibitors of other viruses such as human immunodeficiency virus.

Production of infectious human respiratory syncytial virus from cloned cDNA confirms an essential role for the transcription elongation factor from the 5' proximal open reading frame of the M2 mRNA in gene expression and provides a capability for vaccine development.

Infectious human respiratory syncytial virus (RSV) was produced by the intracellular coexpression of five plasmid-borne cDNAs. One cDNA encoded a complete positive-sense version of the RSV genome (corresponding to the replicative intermediate RNA or antigenome), and each of the other four encoded a separate RSV protein, namely, the major nucleocapsid N protein, the nucleocapsid P phosphoprotein, the major polymerase L protein, or the protein from the 5' proximal open reading frame of the M2 mRNA [M2(ORF1)]. RSV was not produced if any of the five plasmids was omitted. The requirement for the M2(ORF1) protein is consistent with its recent identification as a transcription elongation factor and confirms its importance for RSV gene expression. It should thus be possible to introduce defined changes into infectious RSV. This should be useful for basic studies of RSV molecular biology and pathogenesis; in addition, there are immediate applications to the development of live attenuated vaccine strains bearing predetermined defined attenuating mutations.

Estudo da viabilidade para introduzir na rotina testes de diagnóstico para infecção respiratória aguda

Para avaliar os benefícios da comunicação rápida ao clínico do diagnóstico de vírus respiratórios, foi analisado a viabilidade econômica de 2 testes, com o tempo de entrega de resultado em 2 horas para teste rápido e 48 horas para Biologia Molecular. As amostras coletadas foram processadas utilizando técnicas convencionais e os testes disponíveis no mercado local. Foram escolhidos dois testes rápidos pelo método de imunocromatografia para quatro parâmetros analíticos: Influenza A, Influenza H1N1, Influenza B e Vírus Sincicial Respiratório (RSV) e em Biologia Molecular um teste de RT-PCR multiplex com 25 patógenos entre vírus e bactérias. O tipo de amostra utilizada foi swab e lavado de nasofaringe. A população escolhida para o estudo foi paciente adulto, em tratamento de câncer, que necessita de uma resposta rápida já que a maioria se encontra com comprometimento do sistema imune por doença ou por tratamento. O estudo foi transversal, realizado entre os anos de 2012 e 2013, para avaliar a viabilidade econômica da introdução de testes de diagnóstico da infecção respiratória aguda de etiologia viral a partir de amostras de nasofaringe em pacientes com câncer atendidos no Centro de Atendimento de Oncologia Intercorrência (CAIO ), do Instituto do Câncer do Estado de São Paulo (ICESP), hospital público que atende exclusivamente Sistema Único de Saúde (SUS) e Hospital A.C. Camargo, que atende tanto a pacientes do SUS como da rede privada. O estudo incluiu 152 pacientes em tratamento para qualquer tipo de câncer, predominantemente do sexo feminino (81 mulheres e 70 homens) com idades entre 18-86 anos. Para participar do estudo o paciente era consultado e o critério para escolha do paciente foi ser portador de câncer, com história de febre (ainda que referida) acompanhada de tosse ou dor de garganta, tosse e sintomas respiratórios agudos, atendidos por protocolo padronizado que inclui avaliação na admissão, seguimento e manejo antimicrobiano. Para a avaliação econômica os pacientes foram classificados de acordo com o estado geral de saúde, se apresentavam bom estado de estado de saúde poderiam receber alta e faziam uso da medicação em casa evitando 5 dias de internação se recebessem algum resultado para Influenza ou RSV, no entanto os pacientes que apresentavam outro vírus, resultado negativo ou o estado geral era ruim permaneciam internados por 7 dias em observação e cuidados com medicação adequada. Foram realizadas análises econômicas em dois âmbitos: o sistema de saúde publico e o privado considerando o fator diminuição de dias de internação. A analise de Custo-benefício foi eficiente no Sistema privado mas inadequada para o SUS assim como, qualquer outra medida monetária já que os valores de reembolso do SUS estão defasados do custo de qualquer internação. A análise de Custo-efetividade que olha para outros fatores além do monetário foi efetiva nos dois sistemas que enfrentam falta de leitos além da condição de saúde do paciente de evitar a ingestão desnecessária de antibióticos, evitar os gastos do acompanhante, perda de dias de trabalho e estudo. Não houve correspondência de resultados dos testes rápidos com o multiplex de Biologia Molecular

A sensitive, specific, and cost-effective multiplex reverse transcriptase-PCR assay for the detection of seven common respiratory viruses in respiratory samples

Cell culture and direct fluorescent antibody (DFA) assays have been traditionally used for the laboratory diagnosis of respiratory viral infections. Multiplex reverse transcriptase polymerase chain reaction (m-RT-PCR) is a sensitive, specific, and rapid method for detecting several DNIA and RNA viruses in a single specimen. We developed a m-RT-PCR assay that utilizes multiple virus-specific primer pairs in a single reaction mix combined with an enzyme-linked amplicon hybridization assay (ELAHA) using virus-specific probes targeting unique gene sequences for each virus. Using this m-RT-PCR-ELAHA, we examined the presence of seven respiratory viruses in 598 nasopharyngeal aspirate (NPA) samples from patients with suspected respiratory infection. The specificity of each assay was 100%. The sensitivity of the DFA was 79.7% and the combined DFA/culture amplified-DFA (CA-DFA) was 88.6% when compared to the m-RT-PCR-ELAHA. Of the 598 NPA specimens screened by m-RT-PCR-ELAHA, 3% were positive for adenovirus (ADM), 2% for influenza A (Flu A) virus, 0.3% for influenza B (Flu B) virus, 1% for parainfluenza type I virus (PIV1), 1% for parainfluenza type 2 virus (PIV2), 5.5% for parainfluenza type 3 virus (PIV3), and 21% for respiratory syncytial virus (RSV). The enhanced sensitivity, specificity, rapid result turnaround time and reduced expense of the m-RT-PCR-ELAHA compared to DFA and CA-DFA, suggests that this assay would be a significant improvement over traditional assays for the detection of respiratory viruses in a clinical laboratory.

Modular alpha-helical mimetics with antiviral activity against respiratory syncitial virus

A 13-residue peptide sequence from a respiratory syncitial virus fusion protein was constrained in an alpha-helical conformation by fusing two back-to-back cyclic alpha-turn mimetics. The resulting peptide, Ac-(3 -> 7; 8 -> 12)-bicyclo-FP[KDEFD][KSIRD]V-NH2, was highly alpha-helical in water by CD and NMR spectroscopy, correctly positioning crucial binding residues (F488, I491, V493) on one face of the helix and side chain-side chain linkers on a noninteracting face of the helix. This compound displayed potent activity in both a recombinant fusion assay and an RSV antiviral assay (IC50 = 36 nM) and demonstrates for the first time that back-to-back modular alpha-helix mimetics can produce functional antagonists of important protein-protein interactions.