Comparison of protective effect of neutralizing antibody in serum and nasal secretions in experimental rhinovirus type 13 illness

Identification of Epitopes on Rhinovirus 89 Capsid Proteins Capable of Inducing Neutralizing Antibodies

Rhinoviruses (RVs) are major causes of the common cold, but they can also trigger exacerbations of asthma. More than 160 different RV strains exist and can be classified into three genetic species (RV-A, RV-B and RV-C) which bind to different receptors on human cells including intracellular adhesion molecule 1 (ICAM-1), the low-density lipoprotein receptor (LDLR) or the cadherin-related family member 3 (CDHR3). Epitopes located in the RV capsid have mainly been determined for RV2, a minor-group RV-A strain binding to LDLR, and for RV14, a major-group RV-B strain binding to ICAM-1. In order to study epitopes involved in the neutralization of RV89, an ICAM-1-binding RV-A strain which is highly different from RV2 and RV14 in terms of receptor specificity and sequence, respectively, we analyzed the specificity and epitopes of a highly neutralizing antiserum using recombinantly produced RV89 capsid proteins (VP1, VP2, VP3 and VP4), recombinant fragments and synthetic overlapping peptides thereof. We found that the antiserum which neutralized in vitro RV89 infection up to a dilution of 1:24,000 reacted with the capsid proteins VP1 and VP2 but not with VP3 and VP4. The neutralizing antibodies recognized recombinant fragments comprising approximately 100 amino acids of the N- and C-terminus of VP1 and the middle part of VP2, in particular, three peptides which, according to molecular modeling based on the three-dimensional structure of RV16, were surface-exposed on the viral capsid. Two recombinant fusion proteins containing the identified peptides fused to hepatitis B (HBV)-derived preS as a carrier protein induced upon immunization of rabbits antibodies capable of neutralizing in vitro RV89 infections. Interestingly, the virus-neutralizing epitopes determined for RV89 corresponded to those determined for minor-group RV2 binding to LDL and major-group RV14 belonging to the RV-B species, which are highly different from RV89. Our results indicate that highly different RV strains, even when reacting with different receptors, seem to engage similar parts of their capsid in the infection process. These results may be important for the design of active and passive immunization strategies for RV.

Vaccine strategies to induce broadly protective immunity to rhinoviruses

Rhinoviruses are ubiquitous human pathogens of the upper respiratory tract and are the major cause of acute exacerbations of asthma and chronic obstructive pulmonary disease. At least 160 antigenically distinct serotypes or strains have been identified and protective immunity is largely serotype specific. Attempts to produce vaccines that induce broad immunity have met with limited success which is due in part to this antigenic diversity and a lack of information regarding the ideal protective immune responses. Recent approaches identifying conserved rhinovirus epitopes and better definitions of the immune correlates of protection have raised hope. Here, these newer findings are outlined and the prospects for such a universal rhinovirus vaccine are discussed.

Infant Immune Response to Respiratory Viral Infections

Of all respiratory viruses that affect infants, respiratory syncytial virus (RSV) and rhinovirus (RV) represent the leading pathogens causing acute disease (bronchiolitis) and are associated with the development of recurrent wheezing and asthma. The immune system in infants is still developing, and several factors contribute to their increased susceptibility to viral infections. These factors include differences in pathogen detection, weaker interferon responses, lack of immunologic memory toward the invading pathogen, and T-cell responses that are balanced to promote tolerance and restrain inflammation. These aspects are reviewed here with a focus on RSV and RV infections.

Rhinovirus Biology, Antigenic Diversity, and Advancements in the Design of a Human Rhinovirus Vaccine

Human rhinovirus (HRV) remains a leading cause of several human diseases including the common cold. Despite considerable research over the last 60 years, development of an effective vaccine to HRV has been viewed by many as unfeasible due, in part, to the antigenic diversity of circulating HRVs in nature. Over 150 antigenically distinct types of HRV are currently known which span three species: HRV A, HRV B, and HRV C. Early attempts to develop a rhinovirus vaccine have shown that inactivated HRV is capable of serving as a strong immunogen and inducing neutralizing antibodies. Yet, limitations to virus preparation and recovery, continued identification of antigenic variants of HRV, and logistical challenges pertaining to preparing a polyvalent preparation of the magnitude required for true efficacy against circulating rhinoviruses continue to prove a daunting challenge. In this review, we describe HRV biology, antigenic diversity, and past and present advances in HRV vaccine design.

A polyvalent inactivated rhinovirus vaccine is broadly immunogenic in rhesus macaques

As the predominant aetiological agent of the common cold, human rhinovirus (HRV) is the leading cause of human infectious disease. Early studies showed that a monovalent formalin-inactivated HRV vaccine can be protective, and virus-neutralizing antibodies (nAb) correlated with protection. However, co-circulation of many HRV types discouraged further vaccine efforts. Here, we test the hypothesis that increasing virus input titres in polyvalent inactivated HRV vaccine may result in broad nAb responses. We show that serum nAb against many rhinovirus types can be induced by polyvalent, inactivated HRVs plus alhydrogel (alum) adjuvant. Using formulations up to 25-valent in mice and 50-valent in rhesus macaques, HRV vaccine immunogenicity was related to sufficient quantity of input antigens, and valency was not a major factor for potency or breadth of the response. Thus, we have generated a vaccine capable of inducing nAb responses to numerous and diverse HRV types.

Utility of animal and in vivo experimental infection of humans with rhinoviruses in the development of therapeutic agents for viral exacerbations of asthma and chronic obstructive pulmonary disease

There is an association with acute viral infection of the respiratory tract and exacerbations of asthma and chronic obstructive pulmonary disease (COPD). Although these exacerbations are associated with several types of viruses, human rhinoviruses (HRVs) are associated with the vast majority of disease exacerbations. Due to the lack of an animal species that is naturally permissive for HRVs to use as a facile model system, and the limitations associated with animal models of asthma and COPD, studies of controlled experimental infection of humans with HRVs have been used and conducted safely for decades. This review discusses how these experimental infection studies with HRVs have provided a means of understanding the pathophysiology underlying virus-induced exacerbations of asthma and COPD with the goal of developing agents for their prevention and treatment.

Developing a vaccine for human rhinoviruses

Rhinoviruses (RV's) are common human pathogens of the respiratory tract being the most frequent cause of mild diseases of the upper respiratory tract (common cold) but more importantly they are a major initiator of acute exacerbations of chronic airway diseases. Infections can be life threatening in the latter context however RV -induced common colds have an associated economic cost from loss of productivity due to absence from work or school. There are no appropriate antiviral therapies available and vaccine strategies have failed because of the large number of viral serotypes and the lack of cross-serotype protection generated. Here, approaches past and present for development of a vaccine to these widespread human pathogens are highlighted.

Parenthood and host resistance to the common cold

OBJECTIVE

To determine whether parenthood predicts host resistance to the common cold among healthy volunteers experimentally exposed to a common cold virus.

METHODS

Participants were 795 healthy volunteers (age range = 18-55 years) enrolled in one of three viral-challenge studies conducted from 1993 to 2004. After reporting parenthood status, participants were quarantined, administered nasal drops containing one of four common cold viruses, and monitored for the development of a clinical cold (infection in the presence of objective signs of illness) on the day before and for 5 to 6 days after exposure. All analyses included controls for immunity to the experimental virus (prechallenge specific antibody titers), viral strain, season, age, sex, race/ethnicity, marital status, body mass, study, employment status, and education.

RESULTS

Parents were less likely to develop colds than nonparents were (odds ratio [OR] = 0.48, 95% confidence interval [CI] = 0.31-0.73). This was true for both parents with one to two children (OR = 0.52, 95% CI = 0.33-0.83) and three or more children (OR = 0.39, 95% CI = 0.22-0.70). Parenthood was associated with a decreased risk of colds for both those with at least one child living at home (OR = 0.46, 95% CI = 0.24-0.87) and those whose children all lived away from home (OR = 0.27, 95% CI = 0.12-0.60). The relationship between parenthood and colds was not observed in parents aged 18 to 24 years but was pronounced among older parents.

CONCLUSIONS

Parenthood was associated with greater host resistance to common cold viruses.

Minimum Infective Dose of the Major Human Respiratory and Enteric Viruses Transmitted Through Food and the Environment

Viruses are a significant cause of morbidity and mortality around the world. Determining the minimum dose of virus particles that can initiate infection, termed the minimum infective dose (MID), is important for the development of risk assessment models in the fields of food and water treatment and the implementation of appropriate infection control strategies in healthcare settings. Both respiratory and enteric viruses can be shed at high titers from infected individuals even when the infection is asymptomatic. Presence of pre-existing antibodies has been shown to affect the infectious dose and to be protective against reinfection for many, but not all viruses. Most respiratory viruses appear to be as infective in humans as in tissue culture. Doses of <1 TCID50 of influenza virus, rhinovirus, and adenovirus were reported to infect 50% of the tested population. Similarly, low doses of the enteric viruses, norovirus, rotavirus, echovirus, poliovirus, and hepatitis A virus, caused infection in at least some of the volunteers tested. A number of factors may influence viruses' infectivity in experimentally infected human volunteers. These include host and pathogen factors as well as the experimental methodology. As a result, the reported infective doses of human viruses have to be interpreted with caution.

Vaccination for asthma exacerbations

Most asthma exacerbations are caused by common cold virus infections, predominantly rhinovirus infections. Full protection against repeat infections with the same rhinovirus serotype is given by serum neutralizing antibody, but cross-reactive antibody developed against other serotypes could yield partial protection and result in attenuated cold and airway symptoms. It is proposed that vaccine-mediated induction of cross-reactive antibody might not prevent rhinovirus infections but might reduce severe asthma symptoms and exacerbations.

Epidemiology, pathogenesis, and treatment of the common cold

OBJECTIVE

Reading this article will reinforce the reader's knowledge of the pathogenesis of the common cold. The rationale for current and potential therapies for the common cold are reviewed in the context of current concepts of the pathogenesis of these illnesses.

DATA SOURCES AND STUDY SELECTION

A MEDLINE literature search was done using the search terms common cold, rhinovirus, and viral respiratory infection. The search was restricted to the English language. Articles were selected for review if the title and/or abstract suggested the content was relevant to the subject of this review. The bibliographies of selected articles were used as a source of additional literature.

RESULTS

Recent studies suggest that the host response to the virus is an important contributor to the pathogenesis of the common cold. Inflammatory mediators, especially the pro-inflammatory cytokines, appear to be an important component of this response and present an attractive target for new interventions for common cold therapies. Currently available treatments for the common cold have limited efficacy against specific symptoms. These therapies should be selected to treat the specific symptoms that are perceived to be the most bothersome by the patient.

Clinical and immunological characteristics of the emulsion form of inactivated influenza vaccine delivered by oral immunization

Prophylaxis of human respiratory diseases caused by influenza viruses is actually a problem of infectious pathology because of their wide prevalence. In our investigations, safety, reactogenicity and immunological activity of the orally administered emulsion-inactivated influenza vaccine prepared from influenza virus strains of types A(H1N1), A(H3N2) and B have been studied. Clinical studies of the emulsion-inactivated influenza vaccine on volunteers has shown its safety and nonreactogenicity. The orally administered vaccine did not cause weak, middle or strong general or local reactions including clinical, biochemical, haemotological and immunological reactions. The emulsion-inactivated vaccine has high immunological activity and induces reliable increases in the level of secretory immunoglobulin A to influenza viruses A and B in protective titers in nasal secretions and saliva of volunteers after one oral administration. The obtained results indicate the expediency of further investigation and improvement of inactivated influenza vaccine for oral administration.

Nasal delivery of vaccines

Only relatively recently the significance of inducing not only systemic immunity but also significant local immunity at susceptible mucosal surfaces has become appreciated. A new field of mucosal immunity has been established as information accumulates on mucosal-associated lymphoid tissue (MALT) and on its role in both local and systemic immune responses. This review describes the formation of vaccines to be delivered to one of MALT components, i.e. the nasal-associated lymphoid tissue (NALT), which bears some similarities with the Peyer's patches of the intestine. The association of antigens with adjuvants and particulate carriers such as microparticles, nanoparticles and liposomes is emphasised.

Truncated bovine herpesvirus-1 glycoprotein I (gpI) initiates a protective local immune response in its natural host

Current modified live and killed BHV-1 vaccines have not reduced the incidence of bovine herpesvirus-1 (BHV-1), the principal viral agent in bovine respiratory disease complex. The requirement for production of viral proteins for immune study has resulted in the establishment of a cell line which constitutively expresses BHV-1 gpI. A truncated BHV-1 envelope gpI protein was secreted into the culture supernatant of D17 cells transfected with the gpI gene lacking the coding sequence for the transmembrane region (TMR). The transmembrane domain is essential for gpI stability in the envelope, virus infectivity and, most probably, natural killer cell recognition; however, we have tested the possibility that this domain is not required for inducing an adaptive, protective immune response. Immunization of calves with this truncated gpI protein induced gpI-specific nasal IgA, IgG1, serum neutralizing antibodies and gpI-specific peripheral lymphocyte proliferation. All immunized calves were protected from clinical disease after BHV-1 challenge. Further, nine of ten immunized calves had no intranasal viral shedding. One animal shed a minimal amount of virus following challenge, but produced no antibodies to other viral proteins as evidenced by immunoprecipitation of 35S-labelled viral proteins by sera from virus-challenged animals. This study represents the first evidence that a recombinant truncated gpI subunit vaccine can confer local mucosal immunity and establish a strong protective barrier against disease caused by BHV-1 in the natural host. Also, these data demonstrate the feasibility of preventing initial viral replication in the host and distinguishing vaccinated from wild-type virus-infected animals.

Decreased salivary immunoglobulin A secretion rate after intense interval exercise in elite kayakers

Endurance athletes have been shown to suffer a high incidence of upper respiratory tract infection (URTI; e.g. colds, sore throat) during intense training and after competition. Previous studies have shown that concentrations of secretory immunoglobulin A (IgA), the major effector of host defense against micro-organisms causing URTI, decrease after intense endurance exercise. Many athletes perform intense interval exercise as part of their normal training. The purpose of this study was to determine whether salivary IgA concentrations also decrease after intense interval exercise during the normal training regime in elite athletes. Timed saliva samples were obtained from eight elite male kayakers immediately before and after three on-water training sessions during a 3-week period. The concentrations of IgA, IgG and IgM were determined separately by enzyme-linked immunosorbent assay, and secretion rates calculated for each Ig. The IgA secretion rate (micrograms.min-1) decreased 27%-38% after all three training sessions (P = 0.007); the largest decrease (38%) was noted after the most intense session at the end of an especially intense week of training. The IgA concentration relative to total protein (micrograms.mg protein-1) was significantly lower (P < 0.05) on this training day compared with the other 2 days. Concentrations and secretion rates of IgG and IgM did not change after exercise, indicating a specific effect on IgA. These data would suggest that, in elite athletes, IgA concentration and secretion rate are reduced by intense interval exercise, and that exercise-induced changes in IgA output may be one mechanism contributing to URTI in elite athletes.

Immune response to nasal delivery of antigenically intact tetanus toxoid associated with poly(L-lactic acid) microspheres in rats, rabbits and guinea-pigs

Tetanus toxoid was adsorbed onto poly(L-lactic acid) microspheres. Analyses by sodium dodecyl sulphate-polyacrylamide gel electrophoresis and Western blotting suggest that the formulation procedure does not affect the stability or the antigenic properties of the protein. After nasal administration to guinea-pigs, the resulting preparation enhanced the immune response to the tetanus toxoid when compared with the free antigen. The increase in systemic immunoglobulin G titre was almost immediate in the group treated with the adsorbed tetanus toxoid (time zero, 140; week 2, 1550; week 4, 2760), reaching 36,000 two weeks after the booster (week 7), whereas the free antigen produced an immune response similar to that found in non-treated animals. In a parallel experiment, latex particles of a similar size to poly(L-lactic acid) microspheres, administered to both rats and rabbits, were detected in the blood stream. These findings with tetanus toxoid demonstrate the use of microsphere delivery systems for nasal application of antigens. These had a profound effect on the immune response, and indicate possibilities for overcoming some of the barriers to drug absorption in general.

Respiratory tract infections due to different rhinovirus serotypes and the influence of maternal antibodies on the clinical expression of the disease in infants

Rhinoviruses were isolated from nasopharyngeal secretions of 49 children hospitalized because of severe respiratory tract infection. The isolates were typed using 90 type-specific antisera. No obvious relation between certain serotypes and the severity of illness was found. Serum samples were drawn from all children simultaneously with the nasopharyngeal secretions and screened for the presence of type-specific neutralizing antibodies. Children aged 1 week to 6 months had higher neutralizing antibody titers and revealed a lower degree of morbidity than older children. The decline of neutralizing serum antibodies with increasing age was correlated with a higher incidence of severe disease in those aged 7-12 months. Nevertheless, also in this age group children with mild clinical courses of disease were observed despite a low concentration or an absence of neutralizing serum antibodies. This indicates that not only neutralizing serum antibodies, but other factors also influence the clinical expression of RHV-induced disease.

Cross-protection against influenza B type virus infection by intranasal inoculation of the HA vaccines combined with cholera toxin B subunit

The relationship between the antibody responses to various influenza B type virus HA vaccines and protection against live B virus infection was investigated in Balb/c mice which had been inoculated intranasally with a combination of the HA vaccines and B subunit of cholera toxin (CTB) 4 weeks previously. The inoculation of HA vaccine, prepared from B/Ibaraki/2/85 (B/Ibaraki), B/Nagasaki/1/87 (B/Nagasaki) or B/Aichi/5/88 (B/Aichi) viruses, combined with CTB induced high levels of both nasal IgA and serum HI antibodies to any of B/Ibaraki, B/Nagasaki and B/Aichi viral antigens. Simultaneous inoculation of each CTB-combined HA vaccine provided complete protection against B/Ibaraki virus infection which is demonstrated by both rapid clearance of pulmonary virus and complete survival. On the other hand, the inoculation of HA vaccine prepared from B/Yamagata/16/88 (B/Yamagata) virus together with CTB induced only a low level of nasal IgA antibodies, cross-reactive to B/Ibaraki, B/Nagasaki and B/Aichi viral antigens and protected only partially against B/Ibaraki virus challenge. The involvement of the B type virus-specific immunity in this protection was suggested by the absence of protection against B/Ibaraki virus infection in mice previously inoculated with both A/PR/8/34 (H1N1) virus HA vaccine and CTB. These results suggest that antibodies to various influenza B viruses are cross-reactive to each B type virus antigens and that cross-protection against B virus infection could be conferred depending on the degree of B type virus cross-reactive immunity including secretory IgA antibodies.

The time course of the humoral immune response to rhinovirus infection

The specific humoral immune response of 17 volunteers to infection with human rhinovirus type 2 (HRV-2) has been measured both by neutralization and by ELISA. Six volunteers who had HRV-2-specific antibodies in either serum or nasal secretions before HRV-2 inoculation were resistant to infection and illness. Of the remaining 11 volunteers who had little pre-existing HRV-2-specific antibody, one was immune but 10 became infected and displayed increases in HRV-2-specific antibodies. These antibodies first increased 1-2 weeks after infection and reached a maximum at 5 weeks. All six resistant volunteers who had high pre-existing antibody and eight of the volunteers who became infected maintained their HRV-2-specific antibody for at least 1 year. At this time they were protected against reinfection. Two volunteers showed decreases in HRV-2-specific antibodies from either serum or nasal secretions. They became infected but not ill after HRV-2 inoculation 1 year later.

Recombinant vaccinia virus/Venezuelan equine encephalitis (VEE) virus protects mice from peripheral VEE virus challenge

Mice immunized with recombinant vaccinia virus (VACC) expressing Venezuelan equine encephalitis (VEE) virus capsid protein and glycoproteins E1 and E2 or with attenuated VEE TC-83 virus vaccine developed VEE-specific neutralizing antibody and survived intraperitoneal challenge with virulent VEE virus strains including Trinidad donkey (subtype 1AB), P676 (subtype 1C), 3880 (subtype 1D), and Everglades (subtype 2). However, unlike immunization with TC-83 virus, immunization with the recombinant VACC/VEE virus did not protect mice from intranasal challenge with VEE Trinidad donkey virus. These results suggest that recombinant VACC/VEE virus is a vaccine candidate for equines and humans at risk of mosquito-transmitted VEE disease but not for laboratory workers at risk of accidental exposure to aerosol infection with VEE virus.

Epitope specificity and protective efficacy of the bovine immune response to bovine herpesvirus-1 glycoprotein vaccines

Bovine herpesvirus-1 (BHV-1) envelope glycoproteins gI, gIII and gIV were individually purified on monoclonal antibody affinity columns and injected intradermally into BHV-1 seronegative calves. The calves developed serum neutralizing antibodies that monospecifically precipitated the immunizing glycoprotein from a preparation of 125I-labelled BHV-1 envelope proteins. A competitive radioimmunoassay using the bovine antisera demonstrated that known functional epitopes had been retained in the glycoprotein vaccines. Calves immunized with the gI, gIII or gIV glycoproteins were not protected from intranasal challenge with BHV-1 and had levels and duration of viral shedding in their nasal secretions similar to those of non-immunized control calves.

Immunogenicity and efficacy of orally administered inactivated influenza virus vaccine in mice

The immunogenicity and protective efficacy of formalin-inactivated whole influenza A/Bangkok/79 virus vaccine given to unprimed Swiss mice orally in capsules, in their drinking water, or by direct injection into the duodenum were studied. Virus-specific IgG and IgA antibody responses to all these methods were dose-dependent and varied according to immunization conditions. Following intranasal challenge with live A/Bangkok influenza virus, mice given greater than or equal to 66 micrograms haemagglutinin (HA) of vaccine in drinking water or capsules, and mice injected into the duodenum with greater than or equal to 0.66 microgram HA, had significantly lower virus titres in their noses and lungs than control mice comparably inoculated.

Active synthesis of hemagglutinin-specific immunoglobulin A by lung cells of mice that were immunized intragastrically with inactivated influenza virus vaccine

Intragastric inoculation with whole-virion vaccine of inactivated influenza virus resulted in production of hemagglutinin (HA)-specific immunoglobulin A (IgA) and IgG both in lung lavage fluids and in serum samples of mice. HA-specific IgA was the predominant isotypic antibody secreted in the lung lavage fluids (average IgA/IgG ratio, 13:1), whereas HA-specific IgG was the major antibody class in serum (average IgA/IgG ratio, 0.3:1). These responses were similar to the antibody responses stimulated by intranasal infection with live influenza virus. In vitro cultures of lymphoid cells from lungs and Peyer's patches, but not from spleens, in the presence of homologous antigen, from mice vaccinated intragastrically synthesized mostly HA-specific IgA. Mice immunized parenterally with inactivated influenza virus produced only IgG in lung lavage fluids and sera. Cultures of lymphoid cells from their spleens, but not their lungs, synthesized HA-specific IgG upon antigenic stimulation in vitro; neither synthesized IgA. These in vitro cell culture results, as well as the inverse relationship of IgA/IgG ratios in lung lavage fluids and sera, demonstrated that the IgA antibody in lung lavage fluids was actively synthesized locally in the lungs of intragastrically immunized mice. This finding was consistent with the migratory distribution of antigen-primed lymphoid cells from Peyer's patches to distant lymphoid tissue such as lung. Intragastric vaccination conferred protection against intranasal challenge with a lethal dose of virulent virus.

The effect of exercise on secretory and natural immunity

Secretory immunity. 1. Intense endurance exercise suppresses salivary immunoglobulins. The exercise-induced decrease is specific for the secretory antibodies IgA and IgM. 2. The suppression of secretory Ig is transitory, lasting at least one hour, and returning to pre-exercise levels by 24 hours after a single bout of severe exercise. These results suggest that anecdotal statements by athletes and their coaches of an increased susceptibility to upper respiratory infection after severe exercise could be related to changes in secretory immunity. Natural immunity. 1. Natural killer activity of PBL is suppressed one hour after intense endurance exercise. This effect is transitory, since activity returns to pre-exercise levels by 24 hours after a single bout of exercise. 2. The decrease in NK lytic activity is due to a decrease in the percentage of NK cells (Leu-11a+ cells). When NK cell activity is expressed on a per cell basis, it appears that activity is enhanced after exercise.

Comparison of long-term systemic and secretory antibody responses in children given live, attenuated, or inactivated influenza A vaccine

A comparison of inactivated intramuscular and live intranasal influenza A vaccines in young children undergoing primary immunization might be expected to show differences in serum and local mucosal antibody responses. To demonstrate such differences, serum and local respiratory tract antibody responses of young children vaccinated with intranasal live, attenuated, cold-adapted (H3N2 or H1N1), or intramuscular inactivated (H3N2) influenza A vaccines were examined for one year after vaccination. Antibody responses were measured by hemagglutination-inhibition (HAI) and class-specific enzyme-linked immunosorbent assay (ELISA). One year after vaccination, live intranasal vaccinees had significantly less decay of serum HAI (p = 0.025) and IgG antibody (p = 0.01) directed against the influenza hemagglutinin and neuraminidase than did intramuscular inactivated vaccinees. Nasal secretory IgA developed almost exclusively in live vaccinees and persisted for up to one year. Persistent nasal secretory IgG was detected in both live and inactivated vaccinees. Live vaccination not only stimulates a more durable serum antibody response, but also induces long-lasting local respiratory tract IgA antibody that may play an important role in host protection.

Effect of specific humoral immunity and some non-specific factors on resistance of volunteers to respiratory coronavirus infection

Thirty-three volunteers were inoculated intranasally with coronavirus 229 E, and their responses monitored by antibody rises, symptomatology and virus excretion. These were related to their pre-trial immune status as indicated by concentrations of specific antibodies and non-specific proteins in serum and nasal washings. Both circulating and local specific antibodies were associated with protection from infection and disease, but only specific IgA antibodies of either type appeared to shorten the period of virus shedding. Although total secretory IgA was significantly associated only with reduction of symptoms, total protein in nasal washings appeared to protect against infection also, indicating that other locally produced proteins, not identified, may be associated with resistance. Two of the many factors which may affect the concentration of circulating and local protective proteins and thus influence the outcome of virus inoculation, namely, sex of the volunteer and the interval since the previous cold, were examined. Male volunteers or volunteers who had had evidence of a recent respiratory infection were less likely to be infected, but if they were infected, they had lower clinical scores and stopped shedding virus earlier than the rest. These groups possessed higher concentrations of specific antibodies and non-specific proteins in their pre-challenge sera and/or nasal washings. The significance of these findings is discussed.

Mechanism of neutralization of influenza virus by secretory IgA is different from that of monomeric IgA or IgG

We have found that bile is a useful source of secretory IgA (scIgA) which can specifically neutralize influenza virus infectivity. Using purified scIgA, we compared the mechanism of neutralization with that mediated by IgA monomers (prepared from scIgA by differential reduction) and IgG. At 4 degrees C, scIgA prevented the attachment of neutralized virus, while neither monomeric IgA nor IgG had any affect on this process or on the subsequent stages of infection by which virion RNA accumulates in nuclei. At 25 and 37 degrees C, scIgA permitted the attachment of approximately half the neutralized virus, but the virus was not internalized. Clearly, the neutralization depends on the character of the antibody used. scIgA may act by steric hindrance (with attachment or penetration, depending on temperature), whereas IgA and IgG neutralize infectivity at a stage subsequent to accumulation of the virus genome in the nucleus.

Cross-protection in mice infected with influenza A virus by the respiratory route is correlated with local IgA antibody rather than serum antibody or cytotoxic T cell reactivity

Mice previously infected with an aerosol of A/Rec 31 influenza virus were strongly protected against an aerosol challenge with A/Vic influenza as judged by lung virus titers recovered 2 days after the challenge infection. Such complete homotypic immunity was not achieved by priming with live Rec 31 virus injected i.v. or UV-inactivated Rec 31 virus administered s.c. together with Al(OH)3 and saponin. The reason for the superior protective effect of the natural infection was investigated. The protection induced by respiratory infection with Rec 31 virus was specific for influenza A viruses. It was not correlated with specific serum hemagglutination inhibition antibody titer or cross-reactive cytotoxic T (Tc) cell reactivity. Moreover, the transfer of splenic and lymphoid T cell populations with strong secondary Tc activity did not significantly reduce lung virus titers in recipient mice 3 days after infection. The protection however occurred in parallel with the presence of cross-reactive IgA antibody in the lung washings. It thus appears that local secretory IgA plays a causal role in the prevention of cross-infection by influenza A virus. Serum antibody and Tc cells, on the other hand, may be crucial for recovery from such infection. All mice primed with live Rec 31 virus, administered i.v. or by aerosol and expressing equally high levels of Tc reactivity, survived a lethal challenge with A/PR8 virus. The same challenge, however, killed half of the mice immunized s.c. with inactivated Rec 31 virus which induced only a low level of Tc reactivity.

Protective efficacies of live attenuated and formaldehyde-inactivated Venezuelan equine encephalitis virus vaccines against aerosol challenge in hamsters

Although two investigational vaccines are used to immunize humans against Venezuelan equine encephalomyelitis virus, neither had previously been tested for protective efficacy against aerosol exposure. Live attenuated vaccine (TC-83) protected all hamsters challenged by either aerosol or subcutaneous routes with 4.7 to 5.2 log10 PFU of virulent Venezuelan equine encephalomyelitis virus. Formaldehyde-inactivated vaccine (C-84) failed to protect against aerosol challenge but did protect against subcutaneous challenge. Protection elicited by TC-83 vaccine did not depend solely on serum-neutralizing antibody. These studies suggest that TC-83 vaccine is preferable to C-84 vaccine for protecting laboratory workers at risk to aerosol exposure.

Dose response of A/Alaska/6/77 (H3N2) cold-adapted reassortant vaccine virus in adult volunteers: role of local antibody in resistance to infection with vaccine virus

An attenuated influenza A candidate vaccine virus, derived from the A/Ann Arbor/6/60 (H2N2) cold-adapted (ca) donor virus and the A/Alaska/6/77 (H3N2) wild-type virus, was evaluated in adult seronegative volunteers (serum hemagglutination-inhibiting antibody titer, less than or equal to 1:8) for level of attenuation, infectivity, antigenicity, and genetic stability. Four groups with similar preinoculation mean titers of serum and nasal wash antibodies were inoculated intranasally with 10(4.5), 10(5.5), 10(6.5), or 10(7.5) 50% tissue culture infectious doses (TCID50) of the ca reassortant virus, and eight other seronegative adult volunteers received the wild-type virus. Only 2 of 66 vaccinees developed fever or mild and brief systemic or upper respiratory tract illness or both. Both volunteers with vaccine-related reactions received the highest dose (10(7.5) TCID50) of ca virus, which indicates that the vaccine retains some mild reactogenicity at a high dosage. In contrast, four of eight volunteers infected with the wild-type virus became ill. Each of the 54 isolates tested retained the temperature-sensitive phenotype of the vaccine virus. Thus, the ca reassortant was genetically stable and attenuated at 10(4.5) to 10(7.5) TCID50 for seronegative adults. The 50% human infective dose of ca virus was approximately 10(5.3) TCID50. Ten and one hundred 50% human infectious doses infected 73 and 83% of vaccinees, respectively, and approximately 75% developed an immunological response at these doses. The failure of the vaccine virus to infect some volunteers was correlated with the presence of pre-inoculation nasal wash immunoglobulin A hemagglutinin antibody.

Isolation of rhinovirus intertypes related to either rhinoviruses 12 and 78 or 36 and 58

Many antigenic relationships have been demonstrated among the 90 rhinovirus serotypes. Among these are reciprocal cross-reactions between serotypes 12 and 78 and between serotypes 36 and 58. Neutralizing-antibody titers to homologous virus of the related pairs are generally 16- to 64-fold higher than to the heterologous member, and neutralization by heterologous antiserum in the pools is not seen with prototype viruses. However, a number of isolates were encountered which gave anomolous results when tested with the antiserum pools in fetal tonsil cells. When these strains were tested in fetal tonsil cells against the monospecific antisera composing the pools, it was shown that several isolates were apparently intertypes, neutralized equally by antisera to related types 12 and 78 or 36 and 58. Isolate 1104, an apparent intertype between serotypes 36 and 58, and isolate 9433, intermediate between serotypes 12 and 78, were selected to use as immunogens in rabbits. When tested in HeLa cells, antiserum prepared against isolate 1104 neutralized isolates 1104, 58, and 36 at titers of 1280, 640, and 40, respectively. The k values against isolates 1104, 58, and 36 were 356, 145, and 4, respectively, indicating a much closer relationship of isolate 1104 to type 58 than to type 36. Similar results were obtained with isolate 9433. The neutralizing-antibody titer of anti-9433 serum was 160 against both 9433 and type 78 and was 20 against type 12. The k values of anti-9433 serum against 9433, 78, and 12 were 161, 111, and 2, respectively, indicating that 9433 and 78 were nearly identical. However, the respective neutralizing-antibody titers of anti-78 serum to type 78 and isolate 9433 were 640 and 80, and the respective k values were 172 and 85, demonstrating some antigenic differences. The discovery of intertypes confirms the antigenic variation among rhinoviruses, and the intertypes may represent links in the evolution of types. These observations also demonstrate that isolates in first or second passage in diploid cells may display an antigenic profile different from that seen in HeLa cells at high HeLa cell passage level.

Secretory and systemic immunological response in children infected with live attenuated influenza A virus vaccines

An enzyme-linked immunosorbent assay was used to measure isotype-specific antibody to purified hemagglutinin (HA) of influenza A virus, using serum and nasal-wash specimens from young children undergoing primary infection with live cold-adapted influenza A/Alaska/77 (H3N2) or A/Hong Kong/77 (H1N1) candidate vaccine virus. The serum antibody response followed the pattern expected for a primary viral infection. Each of 17 vaccinated children had a serum immunoglobulin G (IgG) HA antibody response, 16 had an IgM antibody response, and 13 had an IgA antibody response. Nasal-wash HA antibody was detected in the IgA, IgM, and IgG isotypes. Of the 17 vaccinated children, 14 had an IgA response, 13 had an IgM response, and 9 had an IgG response. Most of the IgA and IgM HA antibody was actively secreted locally, whereas only some of the IgG HA antibody could be shown to be actively secreted into the respiratory tract. There was a good correlation between the level of nasal-wash antibodies measured by the HA-specific IgA enzyme-linked immunosorbent assay and by a plaque neutralization assay. These data indicate that intranasal vaccination of susceptible children with live, attenuated, cold-adapted influenza A viruses efficiently stimulates both systemic and local antibody responses.

Use of combined immunization routes in induction of a salivary immunoglobulin A response to Streptococcus mutans in Macaca fascicularis monkeys

Various combinations of immunization routes were examined for ability to elicit or prolong (or both) a salivary secretory immunoglobulin A response to Streptococcus mutans strain Ingbritt (serotype c) in Macaca fascicularis monkeys. Intraductal (i.d.), per os (p.o.), and subcutaneous (s.c.) routes were utilized. Four groups of three to five monkeys each were immunized by the following schedules: group I--p.o., s.c., i.d.; group II--i.d., p.o., i.d.; group III--s.c., p.o., i.d.; and group IV--control. Immune responses in the serum and parotid fluid were quantitated by using passive hemagglutination assays with purified serotype-specific polysaccharide and by indirect immunofluorescent staining assays. Both s.c. and i.d., but not p.o., routes resulted in detectable serum antibody responses. Only i.d. immunization resulted in a measurable salivary response. Indirect immunofluorescent staining revealed specific secretory immunoglobulin A antibodies in the parotid fluid which correlated with passive hemagglutination titers. The p.o. procedures used in this study did not result either in a prolonged immune response or in measurable tolerance related to the humoral or secretory immune system.

Nasal secretory IgA circadian rhythm: a single-dose suppression test

The existence of a clear circadian rhythm in the local secretion of nasal IgA is well-known phenomenon which is confirmed in the present research. Since the temporal pattern of secretory IgA (SIgA) strictly parallels the ACTH-cortisol cycle, a dependence was hypothesized in previous research, but the suppression of adrenal rhythm by means of massive doses of exogenous corticosteroids showed no influence on the SIgA cycle. In the present research a more sophisticated method of corticoid-incretion suppression was used; the single-dose suppression test with dexamethasone, which influences only the impulsive phase of the rhythm. In this case too, however, no influence was demonstrated on nasal SIgA secretion.

Studies of experimental rhinovirus type 2 infections in polar isolation and in England

After five months of total isolation a wintering party of seventeen British Antarctic Survey (BAS) personnel was inoculated under double blind concitions with placebo, or rhinovirus type 2 which had been propagated in tissue culture. The clinical and virological responses of these subjects were compared with those of volunteers in England who received a similar dose of the same strain. The virus used was apparently partly attenuated for man; at the dosage used its effects in England were similar to a smaller dose of an unattenuated strain, but in the Antarctic it caused relatively severe infections. Both the symptoms and the laboratory evidence of virus infection appeared to be more pronounced in the BAS subjects than in the volunteers in England who received the same challenge. In the former group the infection readily spread to those who were originally given placebo. In the BAS subjects serum antibody titres were well maintained during the isolation period but a significant fall in nasal immunoglobulin concentration was recorded during the 5 months of isolation after the virus challenge. Possible mechanisms for the increased sensitivity to rhinovirus of subjects who have been totally isolated in a small closed community are discussed.

Immunization experiments using the rodent caries model

Taken together, the immunization experiments which have been performed in the rat caries model system appear to suggest a correlation between the presence of salivary antibody to S mutans and reductions in caries caused by these bacteria. However, the multifactorial nature of this disease does not permit at present the conclusion that the presence of this antibody is both necessary and sufficient to give rise to the demonstrated effects on pathogenesis. To clarify the role of salivary antibody, several refinements may be required in the current model. Immunization procedures that elicit only a local antibody response would both simplify interpretations of effects and would be more desirable for use as a vaccine. Such procedures might include intraductal installation of antigen in the parotid gland which has been demonstrated to result in this type of response. An additional refinement stems from the knowledge that the kinds of immunization procedures currently used stimulated both cellular immune and soluble antibody systems, potentially giving rise to a rather broad spectrum of immune responses. Therefore, it might be useful to study the effects on S mutans pathogenesis in rats in which certain of these responses have been repressed, for example, by thymectomy, antilymphocyte serum, and so on. Also, each of these approaches would be measurably enhanced by more sensitive techniques to monitor immunological events in the oral cavity. Refinements in the selection and use of relevant antigens of S mutans also are necessary to delineate the in vivo mechanism of immunological interference in the pathogenesis of cariogenic streptococci. Approaches involve the use of purified GTF antigens or cell surface antigens both in the investigation of these mechanisms in in vitro models using antibody specifically directed to these antigens and in rat immunization experiments using immunogenic preparations of these materials. In addition, alterations in the diet and challenge dosage of infecting cariogenic organisms might permit more sensitive detection of effects in vivo. Clearly, the evidence suggests immunological interference with S mutans pathogenesis in the rat model system. However, several gaps exist in our basic understanding of this interference and of the appropriate system in which to observe these effects. The potential significance of this phenomenon should spur efforts to fill these gaps to establish definitively the role of immunity as an ecological determinant in the oral cavity.

Responses of mice immunized with influenza virus by serosol and parenteral routes

Antibody levels in sera and respiratory secretions and resistance to respiratory infections were examined in mice given live infuenza virus in small-particle (2 mum) aerosols, large-particle (10 mum) aerosols, intraperitoneally, and subcutaneously. After parenteral administration antibody was found primarily in the serum, but small amounts were recovered in bronchoalveolar washings after 2 to 3 weeks. Specific antibody was present in both sera and bronchoalveolar washings from mice given virus in small-particle aerosols to achieve virus dissemination throughout the respiratory tract. Immunoglobulin A, immunoglobulin G, and trace amounts of immunoglobulin M, all specific for the infecting virus, were detected in bronchoalveolar washings of small-particle aerosol-infected mice. Virus administration in large-particle aerosols (for primary virus localization in upper respiratory tract) at doses greater than those required to initiate infection with small-particle aerosols failed to stimulate production of antibody in sera or bronchoalveolar washings. Small-particle aerosol-immunized mice were resistant to subsequent challenge with 10(2.0) respiratory median lethal doses of virulent virus, whereas large-particle aerosol-immunized mice were not protected. Parenteral immunization modified the course of the disease in challenged mice and reduce mortality rates but did not prevent reinfection of the respiratory tract.

Pathogenicity of a strain of feline calicivirus for domestic kittens

A strain of feline calicivirus, isolated from a cheetah exhibiting ulcerative glossitis and conjunctivitis, was administered by aerosol to 4 domestic cats and by contact to a fifth cat. Despite the limited number of animals available for the experiment, the pathogenicity of the virus strain for domestic cats was established. In aerosol-infected animals, clinical signs were referable to infection of both upper and lower respiratory tracts. The virus produced an interstitial pneumonia which, early in infection, was uncomplicated by secondary bronchopneumonia. The in-contact cat exhibited clinical signs referable to infection of the oral cavity only and no lesions were noted in the lower respiratory tract at autopsy. Ulcerative glossitis was a feature of the disease in aerosol-infected and in-contact cats. The virus was isolated from the pharynx of all cats for up to 21 days after infection and from the tonsils at autopsy. The tonsils were considered to be a probable site of multiplication of virus in "carrier" cats.

Clinical aspects of protective immunity of the respiratory tract

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