Prevalence of Antibodies to Four Human Coronaviruses Is Lower in Nasal Secretions than in Serum

Abstract

Little is known about the prevalence of mucosal antibodies induced by infection with human coronaviruses (HCoV), including HCoV-229E and -OC43 and recently described strains (HCoV-NL63 and -HKU1). By enzyme-linked immunosorbent assay, we measured anti-HCoV IgG antibodies in serum and IgA antibodies in nasal wash specimens collected at seven U.S. sites from 105 adults aged 50 years and older (mean age, 67 ؎ 9 years) with chronic obstructive pulmonary disease. Coronaviruses comprise a genus of the family Coronaviridae and are enveloped, single-stranded, positive-sense RNA viruses (30). Four human coronavirus (HCoV) strains have been described, which are associated with a spectrum of disease, from mild, febrile upper respiratory tract illnesses to severe illnesses, including croup, bronchiolitis, and pneumonia, and have a wide geographic distribution (1, 2, 6, 7, 9-14, 16, 20, 25, 26, 31, 32, 35, 39-46). HCoV infection has been a contributor to severe illnesses requiring emergency care and hospitalization of patients with chronic medical conditions (7,9,12,15,16,21,22).The earliest-described HCoV strains, HCoV-229E and HCoV-OC43, which are group I and group II coronaviruses, respectively, have now been joined by the more recently described group I and II strains HCoV-NL63 and HCoV-HKU1 (13,30,42,45,46), which were discovered in the search for other pathogenic coronaviruses after the identification of the coronavirus that causes severe acute respiratory syndrome (SARS) (29). HCoV-NL63 may have infected human populations for a long time, since it diverged phylogenetically from HCoV-229E about 1,000 years ago (33), and seroprevalence would likely be high as a result. Cross-sectional and longitudinal seroepidemiological studies have found large proportions of children and healthy adults to have detectable serum antibodies to the four HCoV strains, and seroconversion occurs often in childhood; seroprevalence increases with age, and reinfections may occur (5,8,23,28,(36)(37)(38). More information is needed about the seroprevalence of these viruses, the durability of the humoral immune response, correlates of immunity, and mucosal antibody responses to HCoV infection. The present study questioned whether the prevalence of antibodies to the four HCoV strains would be different in nasal secretions than in serum of older adult veterans with underlying chronic obstructive pulmonary disease (COPD) who participated in Department of Veterans Affairs Cooperative Study 448 (18). MATERIALS AND METHODSSubjects. A convenience sample of 105 patients who met spirometric criteria for COPD and were enrolled in a larger influenza virus vaccine efficacy trial of patients Ն50 years of age (18) were chosen for analysis in this substudy of the prevalence of antibodies to HCoV, because residual serum and nasal wash specimens collected at the same time for each subject were available for analysis. The 105 subjects were enrolled at seven geographically diverse study sites in the United States, located in the following states: Alabama, Florida,...

Antibodies to coronaviruses are higher in older compared with younger adults and binding antibodies are more sensitive than neutralizing antibodies in identifying coronavirus‐associated illnesses

“…There were 11 RI (six in group 1, five in group 2) with ≥fourfold rise in neutralizing antibody titer to HCoV-229E, six (two in group 1 and four in group 2) to -NL63 and four (one in group 1 and three in group 2) to -OC43, and of these, four RI had an accompanying ≥fourfold rise in neutralizing antibody to both HCoV-229E and -NL63 with one also having a ≥fourfold increase against HCoV-OC43. Therefore, the total number of RI with a rise in neutralization antibody titer to one or more HCoV strains was 16,7 (46.7%) in groups 1 and 9 (33.3%) in group 2. A more than threefold increase in ELISA antibody titer was a predictor in only a minority of illnesses of an increase in neutralizing antibody to HCoV (Table 1).…”

“…Mock antigen was prepared from uninfected cells. 7,8,16 Virus-infected cells were frozen and thawed three times, the supernatant fluid was clarified of cell debris by centrifugation, the virus was concentrated by overnight centrifugation, and the virus pellet was resuspended in phosphate-buffered saline. The concentrated virus was inactivated by psoralen compound (Sigma, St Louis, MO), followed by irradiation by long-wavelength UV light, as described.…”

“…17,18 HCoV-HKU1 has not been grown using standard tissue culture techniques, so His 6 -tagged recombinant nucleoprotein (N) of HCoV-HKU1 and mock antigen that was produced from the same plasmid DNA vector without the N protein gene were used as antigens to detect antibody to -HKU1, as described. 7,8,16 Viral and mock antigens, the same stocks throughout the assays, were used to coat flat-bottom 96-well Maxisorp Immunoplates (Nalge-Nunc International, Rochester, NY) followed by the sequence of serum in serial dilutions, mouse antihuman IgG conjugated with horseradish peroxidase (Accurate Chemical and Scientific, Westbury, NY) and peroxidase substrate (KPL, Gaithersburg, MD). Optical density was measured at 405 nm in a spectrophotometer.…”

“…The anti-HCoV serum antibody titer was calculated by the reference-line least-squares-fit method, as described. 8,16,19 Positive and negative control sera were assayed to confirm consistency between assays. Also, all sera from each subject were evaluated in the same assay to avoid inter-assay variability.…”

“…[2][3][4][5] Hence, serologic reactivity to these common HCoV strains may be different among chronically ill older adults compared to younger adults. In a previous study of older adults with underlying chronic pulmonary disease, 16 we reported that serum immunoglobulin G (IgG) antibodies to all four HCoV strains were prevalent in most study subjects, but mucosal immunoglobulin A antibodies to the four common HCoV strains in nasal wash specimens were detected in a minority of patients. Mucosal immune responses also deserve further study with respect to mitigation of HCoV infections.…”