Improving ability of RSV microneutralization assay to detect G-specific and cross-reactive neutralizing antibodies through immortalized cell line selection.

Respiratory syncytial virus (RSV) is a significant cause of bronchiolitis and pneumonia. Protection against RSV is associated with neutralizing antibodies against the fusion (F) and attachment (G) glycoproteins. Several RSV vaccine candidates are in development, but their immunogenicity is hard to compare due to the little-understood differences between multiple RSV neutralizing antibody assays used. Existing assays utilize primarily Vero or HEp-2 cells, but their ability to detect G-neutralizing antibodies or antibodies against specific RSV strains is unclear. In this work, we developed an RSV microneutralization assay (MNA) using unmodified RSV and immortalized cell line derived from human airway epithelial cells (A549). Performance of A549-, HEp-2- and Vero-based MNA was compared under the same assay conditions (fixed amount of virus and cells) with regards to detection of neutralizing antibodies against RSV A or B viruses, G-reactive neutralizing antibodies, and effect of complement. Our results indicate that A549 cells yield the highest MNA titers, particularly in the RSV A/A2 MNA, are least susceptible to complement-enhancing effect of neutralizing titer readout and are superior to Vero or HEp-2 MNA at recognizing G-reactive neutralizing antibodies when no complement is used. Vero cells, however, can be more consistent at recognizing neutralizing antibodies against multiple RSV strains. The choice of substrate cells thus affects the outcome of MNA, as some immortalized cells better support detection of broader range of neutralizing antibodies, while others facilitate detection of G-targeting neutralizing antibodies, a long-thought prerogative of primary airway epithelial cells.

T-Cell Responses in Adults During Natural Respiratory Syncytial Virus Infection.

Background: The pathogenesis of respiratory syncytial virus (RSV) in older adults may be due to age-related T-cell immunosenescence. Thus, we evaluated CD4 and CD8 T-cell responses during RSV infection in adults across the age spectrum. Methods: Peripheral blood mononuclear cells collected during RSV infection in adults, age 26-96 years, were stimulated with live RSV and peptide pools representing F, M, NP, and G proteins and analyzed by flow cytometry. Results: There were no significant age-related differences in frequency of CD4+ T cells synthesizing interferon (IFN)γ, interleukin (IL)2, IL4, IL10, or tumor necrosis factor (TNF)α or in CD8+IFNγ+ T cells. IL4+CD4+ T-cell numbers were low, as were IL13 and IL17 responses. However, in univariate analysis, CD4 T-cell IFNγ, IL2, IL4, IL10, and TNFα responses and CD8+IFNγ+ T cells were significantly increased with more severe illness requiring hospitalization. In multivariate analysis, viral load was also associated with increased T-cell responses. Conclusions: We found no evidence of diminished RSV-specific CD4 or CD8 T-cell responses in adults infected with RSV. However, adults with severe disease seemed to have more robust CD4 and CD8 T-cell responses during infection, suggesting that disease severity may have a greater association with T-cell responses than age.

Treatment with novel RSV Ig RI-002 controls viral replication and reduces pulmonary damage in immunocompromised Sigmodon hispidus.

Respiratory syncytial virus (RSV) is a significant cause of bronchiolitis and pneumonia in several high health risk populations, including infants, elderly and immunocompromised individuals. Mortality in hematopoietic stem cell transplant recipients with lower respiratory tract RSV infection can exceed 80%. It has been shown that RSV replication in immunosuppressed individuals is significantly prolonged, but the contribution of pulmonary damage, if any, to the pathogenesis of RSV disease in this susceptible population is not known. In this work, we tested RI-002, a novel standardized Ig formulation containing a high level of RSV-neutralizing Ab, for its ability to control RSV infection in immunocompromised cotton rats Sigmodon hispidus. Animals immunosuppressed by repeat cyclophosphamide injections were infected with RSV and treated with RI-002. Prolonged RSV replication, characteristic of immunosuppressed cotton rats, was inhibited by RI-002 administration. Ab treatment reduced detection of systemic dissemination of viral RNA. Importantly, pulmonary interstitial inflammation and epithelial hyperplasia that were significantly elevated in immunosuppressed animals were reduced by RI-002 administration. These results indicate the potential of RI-002 to improve outcome of RSV infection in immunocompromised subjects not only by controlling viral replication, but also by reducing damage to lung parenchyma and epithelial airway lining, but further studies are needed.

Protein S declines during winter respiratory infections.

There is an increase in cardiovascular and cerebrovascular morbidity and mortality in the older adult population during the winter that could be related to prothrombotic changes caused by seasonal effects or acute respiratory tract infections. Therefore, a prospective cohort study was conducted to assess the effect of acute winter respiratory infection on hemostatic parameters including complement 4b-binding protein (C4-BP), functional protein S, total protein S, free protein S, and the inflammatory marker, interleukin-6 (IL-6), in younger and older adults. The changes in the levels of hemostatic and inflammatory markers during winter respiratory infections in the younger and older adults were compared with matched, non-infected controls. In younger and older adults (combined), total protein S increased from 83% [95% confidence interval (CI); 77-88] to 98% (95% CI; 91-106, P < 0.001) while free protein S decreased from 100% (95% CI; 95-105) to 70% (95% CI; 66-75, P < 0.001). There were no significant changes in C4-BP (P = 0.622), functional protein S (P = 0.061) or IL-6 (P = 0.651) from baseline. In a multivariate analysis, only total protein S and free protein S showed significant association with seasonal change after adjusting for the effect of infection. The estimated effect of season on total protein S was 15 +/- 4%, P < 0.001 and on free protein S was -27 +/- 3%, P < 0.001. After adjusting for seasonal effect, only functional protein S showed a significant association with infection, with the estimated effect of -17 +/- 5%, P < 0.001. The results in the younger and older adults were similar to those in the combined groups. Seasonal and infection-related changes in hemostatic parameters including an increase in fibrinogen and a decrease in free protein S, observed in this study, may contribute to thrombotic risk and excess vascular disease morbidity and mortality in older populations in the winter season.

Hepatitis B immunization of healthy elderly adults: relationship between naïve CD4+ T cells and primary immune response and evaluation of GM-CSF as an adjuvant.

The efficacy of granulocyte-macrophage colony-stimulating factor (GM-CSF) to enhance the primary immune response to hepatitis B vaccine was studied in healthy elderly with young volunteers included as controls in this double-blind, placebo-controlled trial of GM-CSF as an immune adjuvant. Naïve T-helper cells (CD4+CD45RA+) were determined at baseline. Forty-five healthy elderly (average age, 74 years) and 37 healthy young controls (average age, 28 years) were randomized. Hepatitis B vaccine was administered at 0, 1, and 6 months. GM-CSF as a single injection of either 80 microg or 250 microg with the first and second doses of hepatitis B vaccine. In this trial GM-CSF did not enhance antibody responses. However, the antibody responses were dramatically different between these two groups: 35/35 young developed a protective titer versus 19/45 elderly (P < 0.0001). In addition, the mean logarithm of anti-hepatitis B antibody level in the 35 young who completed the study was 3.17 (log mIU/ml) but only 2.21 in the 19 elderly responders (P < 0.0001). Naïve T-helper cells differed significantly between the two groups: the mean percentage of CD4+CD45RA+ T cells was 47.9% versus 35.0% (P < 0.0001) in the young and elderly volunteers respectively. Naïve T cells also differed significantly between elderly who did or did not respond to HBV (39.9% vs. 31.7%, P = 0.039). Using linear regression, age, and percent naive, CD4 T cells were determined to significantly influence the anti-hepatitis B antibody response, but sex and dose of GM-CSF did not. For a two-parameter model: logarithm of antibody titer = (-0.038 x age in years) + (0.031 x % naïve CD4T cells) + 2.68; adjusted r2 = 0.605 and P < 0.0001. However, age had a larger effect than naive CD4 T cells, i.e., in comparing young and elderly groups the log antibody titer decreased by 1.73 due to the increase in age but only 0.40 due to the decrease in naive CD4 T cells. Thus, there was a large effect of age that could not be explained by the quantitative change in the naïve T-helper cells.

Response of C-reactive protein and serum amyloid A to influenza A infection in older adults.

Influenza epidemics are associated with significant morbidity and mortality in the elderly, with a substantial proportion of deaths due to cardiovascular events. Elevations of acute-phase proteins have been associated with an increased risk of atherosclerotic events. Therefore, serum amyloid A (SAA) and C-reactive protein (CRP) were measured during influenza illness and 4 weeks later in 7 young persons, 15 elderly outpatients, and 36 hospitalized adults. Striking elevations were seen in mean acute SAA and CRP levels in all groups, but hospitalized patients had the highest levels (SAA, 503 vs. 310 microg/mL [P=.006]; CRP, 120 vs. 34 microg/mL [P<.001]). The presence of dyspnea, wheezing, and fever was also associated with high CRP levels. Influenza infection is associated with significant elevations of SAA and CRP levels in elderly patients, especially those who require hospitalization. It is possible that direct effects of CRP may exacerbate preexisting atherosclerotic lesions and may help explain cardiovascular events associated with acute influenza.

Prothrombotic changes in hemostatic parameters and C-reactive protein in the elderly with winter acute respiratory tract infections.

Mortality rates attributable to cerebrovascular and ischemic heart disease increase among older adults during the winter. Prothrombotic changes in the hemostatic system related to seasonal factors, such as ambient temperature changes, and winter acute respiratory tract infections, may contribute to this excess seasonal mortality. A prospective nested case-control study was conducted to assess the impact of winter acute respiratory tract infections on fibrinogen, factor VII, factor VIIa, D-dimer, prothrombin fragment 1.2, PAI-1, soluble P-selectin and C-reactive protein (CRP) in older adults. The change in laboratory parameters from baseline (fall) to the time of infection in both middle-aged and elderly individuals was compared with matched non-infected controls. In older adult participants with winter acute respiratory tract infections, significant increases occurred in fibrinogen and C-reactive protein, but not in any other markers. The mean fibrinogen increased 1.52 g/L (38%) and the mean CRP increased 37 mg/L (370%) over baseline (both p <0.001). In a multivariate analysis, both infection and season were associated with the increase in fibrinogen, but only infection was associated with the CRP increase. Old age magnified the increase in CRP but not in fibrinogen. Winter acute respiratory tract infections induce an exaggerated inflammatory response in older adults. The associated increase in fibrinogen, an independent risk factor for ischemic heart disease, may be partly responsible for the excess winter vascular mortality.

Reverse transcription polymerase chain reaction (RT-PCR) for diagnosis of respiratory syncytial virus infection in adults: use of a single-tube "hanging droplet" nested PCR.

Rapid diagnosis of Respiratory Syncytial virus (RSV) infection is difficult in elderly persons due to the low quantities of virus shed. Therefore, reverse transcription-polymerase chain reaction (RT-PCR) was used to detect viral RNA in respiratory secretions. A single-tube nested RT-PCR that used primers from a conserved F gene sequence was developed using a "hanging droplet" to physically separate outer and inner primer pairs during the first round of the PCR reaction. This was accomplished by placing the inner primers in a 5 microL droplet on the underside on the reaction tube cap and mixing after the first round of PCR. As few as 0.05 pfu of virus could be detected and gave positive results with RSV strains that represented the major groups and subgroups of RSV grown in tissue culture. The nested PCR was approximately 100-fold more sensitive than standard single primer PCR reactions and equivalent to standard two-tube nested PCR. Viral RNA was detected in nasopharyngeal samples from 12 of 15 culture positive illnesses and in 5 of 17 culture-negative, seropositive illnesses despite specimen volumes less than 1 microL in some samples. The method was also positive in 14 of 25 elderly volunteers inoculated with a live attenuated RSV vaccine candidate, only one of whom was culture positive. Use of a nested RT-PCR significantly improves the ability to detect RSV in respiratory samples and should improve the ability to rapidly diagnose RSV infection in adults, especially in the elderly.

Respiratory syncytial virus infection in adults.

Respiratory syncytial virus (RSV) is now recognized as a significant problem in certain adult populations. These include the elderly, persons with cardiopulmonary diseases, and immunocompromised hosts. Epidemiological evidence indicates that the impact of RSV in older adults may be similar to that of nonpandemic influenza. In addition, RSV has been found to cause 2 to 5% of adult community-acquired pneumonias. Attack rates in nursing homes are approximately 5 to 10% per year, with significant rates of pneumonia (10 to 20%) and death (2 to 5%). Clinical features may be difficult to distinguish from those of influenza but include nasal congestion, cough, wheezing, and low-grade fever. Bone marrow transplant patients prior to marrow engraftment are at highest risk for pneumonia and death. Diagnosis of RSV infection in adults is difficult because viral culture and antigen detection are insensitive, presumably due to low viral titers in nasal secretions, but early bronchoscopy is valuable in immunosuppressed patients. Treatment of RSV in the elderly is largely supportive, whereas early therapy with ribavirin and intravenous gamma globulin is associated with improved survival in immunocompromised persons. An effective RSV vaccine has not yet been developed, and thus prevention of RSV infection is limited to standard infection control practices such as hand washing and the use of gowns and gloves.

Evaluation of the live attenuated cpts 248/404 RSV vaccine in combination with a subunit RSV vaccine (PFP-2) in healthy young and older adults.

The safety and immunogenicity of the live attenuated cold-passaged, temperature-sensitive (cpts) 248/404 respiratory syncytial virus (RSV) A2 and the RSV A2 purified F glycoprotein (PFP-2) vaccine candidates were evaluated in a placebo-controlled trial in 60 healthy young adults and 60 healthy elderly subjects using simultaneous and sequential (cpts 248/404 followed by PFP-2) vaccination schedules. Both vaccines were well tolerated. The cpts 248/404 vaccine was moderately infectious in both young and old volunteers, but was highly restricted in replication in those who were infected. After both vaccines, RSV neutralizing antibody (neut Ab) titers increased fourfold in 22% of young subjects and in 16% of elderly subjects. Of those with low levels of RSV neut Ab (titer <9), 10/12 (83% of) young subjects and six/eight (75% of) elderly subjects had a >/=four fold rise in neut Ab titer. Young and elderly subjects immunized simultaneously had similar serum IgG and IgA postimmunization titers to RSV F (IgG, 16.4 vs 16.2, IgA 11.6 vs 12. 5, respectively) as did those who were immunized sequentially (IgG 17.4 vs 17.0, IgA 13.0 vs 13.5). In both age groups, sequential immunization elicited higher postimmunization RSV F IgG and IgA titers than simultaneous immunization. Further studies that combine the PFP-2 subunit vaccine with a less attenuated RSV vaccine should be performed.

Respiratory syncytial and other virus infections in persons with chronic cardiopulmonary disease.

Respiratory syncytial virus (RSV) has been increasingly recognized as an important cause of serious respiratory illness in some adult populations, including those with underlying cardiopulmonary diseases. However, the precise incidence and the clinical impact of RSV in this group are unknown. Therefore, the incidence and clinical impact of RSV infection in persons with chronic obstructive pulmonary disease (COPD) and congestive heart failure (CHF) who reside in the community were prospectively evaluated over two consecutive winters in 134 persons. Eight RSV (incidence of 4.3 per 100 subject-winters), 13 influenza A (incidence of 7.0 per 100 subject-winters), seven rhinovirus, nine coronavirus, and two parainfluenza virus infections were identified. The clinical illnesses associated with RSV and influenza A virus were similar, causing both upper and lower respiratory signs and symptoms. The clinical impact was significant as three of eight RSV-infected subjects were hospitalized compared with six of 13 influenza A-infected persons and zero of seven rhinovirus-infected persons.

Comparison of respiratory syncytial virus humoral immunity and response to infection in young and elderly adults.

Little information about immunity to respiratory syncytial virus (RSV) and disease pathogenesis in elderly persons exists. Humoral immunity to RSV was assessed in 41 young, 56 healthy elderly, and 49 frail elderly adults by measuring baseline RSV specific IgG by enzyme immunoassay (EIA) and microneutralization assay (MNA) in serum. A comparison of the immune response of 11 young and 28 elderly persons with natural RSV infection was also performed. Despite significant differences in age and functional status, no decreases in RSV antibody levels by either EIA or MNA were noted in the elderly compared with the young. Mean baseline MNA titers expressed as log2 were 10.5 +/- 1.1 for the young, 10.5 +/- 1.5 for the healthy elderly, and 10.9 +/- 1.6 for the frail elderly. The frail elderly who attend a daycare had the highest RSV titers to F by EIA at 16.6 +/- 2.0, compared with 15.4 +/- 1.4 and 15.1 +/- 1.4 in the healthy elderly and young, respectively. This finding may reflect recent infection due to their communal setting or increased production of non-neutralizing antibody. The immune response of older persons to RSV infection was as vigorous as the younger subjects, with 79% having a >/=fourfold rise in MNA titers compared to 64% in the young. These data suggest that the severe clinical manifestations of RSV in the elderly are not due to a significant defect in humoral immunity.

A simple and reproducible method for collecting nasal secretions in frail elderly adults, for measurement of virus-specific IgA.

The standard method for collection of respiratory secretions, by use of a nasal wash (NW) to measure virus-specific IgA, is problematic in frail elderly adults. Therefore, a simplified collection approach using a nasal swab (NS) is described. NW and NS samples were collected from healthy young and frail elderly adults, and IgA titers to respiratory syncytial virus (RSV) fusion and attachment glycoproteins were determined by enzyme immunoassay. Correlation between IgA titers in NW and NS was excellent for each of the antigens (correlation coefficients,.71-.93). In addition, NS results were reproducible when frail elderly subjects were sampled several weeks apart and were nearly equivalent to results from NW samples. The ability to sample nasal secretions by use of an NS when an NW is not technically feasible will facilitate the study of mucosal immunity to RSV as well as the study of mucosal response to candidate RSV vaccines in frail elderly populations.

Evaluation of a handwashing intervention to reduce respiratory illness rates in senior day-care centers.

To decrease respiratory infections in senior day care, staff were educated on viral transmission and the value of hand washing. Fanny packs with alcohol foam supplemented hand washing and were alternated monthly between centers. Infection rates were unchanged with alcohol foam use. The intervention year's infection rate was significantly lower than the previous 3 years, suggesting a benefit of education.

Respiratory syncytial virus infection in older persons.

Respiratory Syncytial Virus (RSV) is an increasingly recognized cause of serious disease in older adults. RSV causes excess morbidity and mortality in older persons residing in nursing homes and in the community. The study of RSV in adults has been hampered by the lack of sensitive methods for the diagnosis of acute infections. Such tools are needed to better understand the epidemiology and immunology of RSV in adults. The immune status of older adults has begun to be explored and preliminary data indicates that low serum neutralizing antibody may predispose to symptomatic RSV infection and that a greater diversity of antibody titres may be seen in the elderly compared to young adults. PFP-2, a candidate RSV subunit vaccine, has been evaluated in healthy and institutionalized elderly and been found to be safe and immunogenic.

Monoclonal antibody neutralization escape mutants of respiratory syncytial virus with unique alterations in the attachment (G) protein.

Five monoclonal antibody (MAb) neutralization escape mutants of respiratory syncytial virus (RSV) were produced by growing the Long strain RSV (group A virus) in the presence of a neutralizing, group cross-reactive MAb specific for the attachment protein (G). Four viruses (RSV-2, -6, -14 and -15) had amino acid replacements clustered within a highly conserved centrally located 13 amino acid region (position 164-176). Reactivity with group A-specific MAbs and with polyclonal anti-G serum was maintained and growth kinetics were unaffected. An additional virus (RSV-3) had four amino acid substitutions in the cytoplasmic tail and transmembrane region of G, and had restricted growth and formed small syncytia. Immunofluorescent and Western blot analysis indicated that G protein was not membrane associated and had reduced incorporation into the virion, thereby escaping neutralization by L9 and polyclonal anti-G serum. The predominant form of G produced by RSV-3 was found in infected cell supernatants, consistent with the size of secreted G.

Relationship of serum antibody to risk of respiratory syncytial virus infection in elderly adults.

The relationship of serum antibody to respiratory syncytial virus (RSV) and risk of RSV infection was prospectively evaluated in frail elderly persons. Baseline blood samples from 22 subjects who developed symptomatic RSV infection during the 26-month study and from 22 control subjects who did not become infected with RSV were compared. The mean serum IgG titer to RSV fusion protein was significantly lower in the RSV-infected group than in the controls (15.4 +/- 1.6 vs. 16.4 +/- 1.8, P = .05), as were the neutralizing titers to group A RSV (12.4 +/- 2.2 vs. 14.2 +/- 2.2, P = .008) and group B virus (9.1 +/- 2.1, vs. 10.3 +/- 1.5, P = .01). These results suggest that older adults with low titers of serum neutralizing antibody may be at greater risk of developing symptomatic RSV infection than those who have high antibody titers.

Safety and immunogenicity of a respiratory syncytial virus subunit vaccine (PFP-2) in the institutionalized elderly.

The safety and immunogenicity of purified fusion protein (PFP-2) respiratory syncytial virus (RSV) vaccine was evaluated in an open label study in 37 frail institutionalized persons over age 65. Vaccination was well tolerated without significant side-effects. Thirty-six of 37 volunteers completed the study. Nineteen of 36 (53%) vaccinees had a greater than or equal to fourfold increase in IgG to F protein at 4 weeks and 17 (47%) had a greater than or equal to fourfold rise in neutralizing titers to either group A or B virus. Although response rate to PFP-2 vaccine in the frail elderly was somewhat diminished compared to results in the healthy elderly, the vaccine was well tolerated and relatively immunogenic.