Interleukin 12 administration enhances Th1 activity but delays recovery from influenza A virus infection in mice

Interleukin 12 (IL-12) directs the differentiation of undifferentiated T helper (Th0) cells to T helper type 1 (Th1) cells and induces a cell-mediated immune response. To evaluate the effect of IL-12 on the course of influenza A virus infection, BALB/c mice were administered a daily intraperitoneal dose of 1000 ng of IL-12 or saline on days -1 to +4 for a total of six treatments. The treatment generally enhanced Th1-mediated responses. IFNgamma lung concentrations were 1193 +/- 275 pg/100 microl in controls and 3693 +/- 745 pg/100 microl in IL-12-treated mice at day 5. IFNgamma levels were undetectable at day 13 in controls and 1335 +/- 220 pg/100 microl in IL-12-treated mice. Cytokine production was also assessed at the single-cell level for mediastinal lymph nodes. IL-12 treatment increased the number of IL-2- and IFNgamma-producing cells and decreased the number of IL-4- and IL-10-producing cells. IL-12 treatment decreased the anti-influenza antibody response, especially anti-influenza IgG1 antibody resulting in an increased IgG2a/IgG1 ratio. Primary pulmonary CTL activity on day 5 was low for both groups (10% specific lysis). Secondary CTL activity at day 11 was higher for control mice than for IL-12-treated mice on day 11 (44 versus 34%), but not on day 13. Despite this overall enhancement of Th1-mediated immune functions, the IL-12 treatment increased severity of the disease. Following infection, control and IL-12-treated mice decreased their body weight to approximately 75% of their initial weight. After day 5, the control mice started to recover, while IL-12-treated mice did not begin recovering until day 9. Pulmonary viral titers were 1.6 +/- 0.3 TCID50 in controls at day 5 compared to 2.4 +/- 0.3 for IL-12-treated mice (P < 0.01). In addition, control mice had significantly less severe inflammation and damage on histologic examination. Serum TNFalpha concentrations, undetectable in control mice, were elevated by IL-12 treatment up to 80 pg/ml at day 5 and decreased to zero at day 13. It is concluded that IL-12 administration to influenza-infected mice induces a switch from a Th2- to a Th1-mediated response, but inhibits recovery probably through induction of TNFalpha.

Oral immunization with a replication-deficient recombinant vaccinia virus protects mice against influenza

Mice immunized with two intragastrically administered doses of a replication-deficient recombinant vaccinia virus containing the hemagglutinin and nucleoprotein genes from H1N1 influenza virus developed serum anti-H1 immunoglobulin G (IgG) antibody that completely protected the lungs from challenge with H1N1. Almost all of the mice given two intragastric doses also developed mucosal anti-H1 IgA antibody, and those with high anti-H1 IgA titers had completely protected noses. Intramuscular injection of the vaccine protected the lungs but not the noses from challenge. We also found that the vaccine enhanced recovery from infection caused by a shifted (H3N2) influenza virus, probably through the induction of nucleoprotein-specific cytotoxic T-lymphocyte activity. A replication-deficient, orally administered, enteric-coated, vaccinia virus-vectored vaccine might safely protect humans against influenza.

Induction of a secretory IgA response in the murine female urogenital tract by immunization of the lungs with liposome-supplemented viral subunit antigen

This study demonstrates that liposomes administered to the lower respiratory tract of mice have the capacity to stimulate secretory IgA (s-IgA) antibody production in the female urogenital system. Total respiratory tract immunization of mice with influenza virus subunit antigen simply mixed with negatively charged liposomes induced antigen-specific s-IgA in vaginal secretions, in addition to systemic IgG and s-IgA in the respiratory tract. Immunization of the upper respiratory tract alone or oral immunization were ineffective. These observations demonstrate that, upon stimulation with liposomes, the lymphoid tissue associated with the lung can act as an inductive site for migration of IgA-committed B cells to distant mucosal tissues, including the female urogenital tract. It is concluded that liposomes administered to the lower respiratory tract provide a promising adjuvant system for stimulation of both systemic and mucosal antibody responses against coadministered antigen, including production of s-IgA at distant mucosal sites.

Enteric immunization of mice against influenza with recombinant vaccinia

Intrajejunal administration to mice of a recombinant vaccinia virus containing the influenza virus hemagglutinin gene induced IgA antibody in nasal, gut, and vaginal secretions. It also induced IgG antibody in serum and cell-mediated immunity. The immunization provided significant protection against an influenza virus challenge. This work suggests that enteric-coated recombinant vaccinia could be an orally administered, inexpensive, multivalent, temperature-stable, safe, and effective vaccine for children that could be particularly useful in developing nations, where multiple injections are not easily administered. Oral administration of vaccines should also reduce children's fear of shots at the doctor's office.

Effects of influenza virus-specific cytotoxic T-lymphocyte responses induced by a synthetic nucleoprotein peptide on the survival of mice challenged with a lethal dose of virus

Even though virus-induced cytotoxic T lymphocytes (CTLs) recognize antigens as peptides presented on infected cells, short synthetic peptides without any modifications are generally considered unsuitable for inducing antigen-specific CTLs in vivo. Our results demonstrate rapid induction of influenza virus-specific CTLs in Balb/c mice by an unmodified core protein peptide known to be a dominant H-2d-restricted CTL epitope. Additionally, the immunization procedure we employed in these studies produced significant influenza virus-specific CTLs in lymph nodes, spleen and lungs. When challenged with a lethal dose of influenza virus, a statistically significant delay in the day of death was observed in peptide-immunized mice. However, viral clearance was only slightly different from that in control mice. While these results are encouraging, they suggest a requirement for multiple CTL-inducing peptides, helper T cell-inducing peptides and/or virus-specific IgA responses in order to achieve protection from influenza infection.

Class I major histocompatibility complex-restricted cytotoxic T lymphocytes are not necessary for heterotypic immunity to influenza

Mice transgenic for beta 2-microglobulin deletion (beta 2M-/-) were immunized intranasally with either a recombinant vaccinia virus that expressed both nucleoprotein and interleukin-2 or by infection with H3N2 influenza virus; 3-4 weeks later they were challenged with H1N1 influenza virus. The immunized beta 2M-/- mice had increased survival and enhanced clearance of virus relative to nonimmune controls. This protection correlated with the development of class II major histocompatibility complex-restricted pulmonary cytotoxic T lymphocyte activity and nasal IgA anti-nucleoprotein antibody. Heterotypic immunity can therefore be generated by a mechanism that does not involve class I major histocompatibility complex-restricted T cells.

Heterotypic immune mice lose protection against influenza virus infection with senescence

Influenza causes significant morbidity and mortality in the elderly. To determine whether this could be due to loss of heterotypic immunity, young and aged BALB/c mice were made heterotypically immune by H3N2 influenza virus infection and then challenged, while anesthetized, with H1N1 virus. Viral clearance was delayed by 2 days in the aged mice. Naive and heterotypic immune mice were next challenged with H1N1 virus while awake. Under these conditions, initial infection was restricted to the nose in all animals. The virus spread to the lungs of the young and aged naive mice but not of heterotypic immune young mice. Heterotypic immunity of aged mice did not prevent spread of the virus to the lungs. The impaired recovery of aged mice correlated with lower antiinfluenza cytotoxic T lymphocyte (CTL) activity. Thus, a possible explanation for the increased severity of influenza in elderly humans is loss of CTL-mediated heterotypic immunity.

Use of incompatible plasmids to control expression of antigen by Salmonella typhimurium and analysis of immunogenicity in mice

Salmonella spp. have been investigated as live vaccine vectors because they are heat stable and can elicit humoral, cellular, and secretory immune responses. However, the expression of some foreign antigens is toxic to bacterial vectors. We therefore studied an approach for the controlled expression of antigen in Salmonella typhimurium wherein the antigen is not expressed in vitro but is expressed in vivo. A model antigen, beta-galactosidase, was expressed from the trc promoter on one plasmid, while repression was achieved by Lacl expressed in trans from a second plasmid. The second repressor plasmid was incompatible with the expression plasmid encoding beta-galactosidase. Loss by segregation of the repressor plasmid in vitro correlated with increased expression of beta-galactosidase. Oral inoculation of mice with salmonellae containing both plasmids induced serum IgG but not nasal, salivary, or biliary IgA antibody to beta-galactosidase. Serum IgG as well as biliary IgA anti-S. typhimurium antibody, but not salivary or nasal IgA, were also detected. This salmonella vector system for the controlled expression of recombinant antigens may be of value for inducing systemic but not mucosal immunity to antigens that are toxic to bacterial vectors.

Recombinant vaccinia immunization in the presence of passively administered antibody

Mice were injected with immune serum to vaccinia and/or influenza virus and then immunized by scarification with a recombinant vaccinia virus expressing the influenza haemagglutinin H1. The serum IgG antibody response to the foreign gene product, influenza H1, was suppressed by the passively administered anti-influenza antibody in a dose-dependent manner. Anti-vaccinia antibody alone had no effect on the anti-haemagglutinin antibody response to the recombinant vaccinia and did not suppress an anti-vaccinia antibody response. Secondary cytotoxic T-lymphocyte killing of influenza virus-infected target cells was relatively low in all animals that were immunized with the recombinant vaccinia, and showed some dose-dependent suppression by the passively administered antibody. The dose dependence of the inhibition suggests that while immunization with recombinant vaccinia viruses may not be effective at birth, they may be useful at several months of age.

Transgenic mice lacking class I major histocompatibility complex-restricted T cells have delayed viral clearance and increased mortality after influenza virus challenge

To investigate the role of CD8+ T lymphocytes in recovery from influenza pneumonia, we used transgenic mice either homozygous (-/-) or heterozygous (+/-) for beta 2-microglobulin (beta 2-M) gene disruption. These mice lack major histocompatibility complex-restricted class I (CD8+) T cells. We found that after challenge with a nonlethal influenza virus, the beta 2-M (-/-) mice had significantly delayed pulmonary viral clearance. Furthermore, after challenge with a more virulent influenza virus, the beta 2-M (-/-) mice had a significantly higher mortality rate than did control mice. Thus, CD8+ T cells are important in recovery from virulent influenza infections, but other host defense mechanisms can clear the respiratory tract of more benign infections.

Influenza: pathogenesis and host defense

Our understanding of the host defense and pathogenesis of influenza has come from parallel studies in animal models and humans. Infection is initiated by deposition of influenza particles on either the upper respiratory tract epithelium or directly into the alveoli, with the former method having a lethal dose several orders of magnitude greater than the latter. The virus attaches to its cellular receptor by its hemagglutinin (HA); if this step is blocked by specific antibody, infection does not take place. The major role of antibody is in the prevention of disease. Even though serum antibody (primarily antihemagglutinin, but also antineuraminidase) has been known for decades to prevent viral pneumonia, it has only more recently been shown that passive administration of anti-influenza serum to virgin mice prevents pneumonia, but not rhinotracheitis. Further, intravenously administered anti-influenza IgA has been shown to be specifically transported into the nasal secretions and protect the murine nasopharynx against influenza infection. Whereas antibody is clearly required for protection against influenza, cytotoxic T-lymphocyte (CTL) activity is both necessary and sufficient for recovery from influenza. This was best shown in studies using nude (athymic) mice. Influenza-infected nude mice shed virus from their lungs indefinitely. Adoptive transfer of anti-influenza CTLs to influenza-infected nude mice will clear the virus from their lungs, whereas administration of anti-influenza antibody will lead to a cessation of viral shedding only as long as antibody is present. Influenza in aging presents a serious clinical problem. Recent studies suggest that the age-related decrease in anti-influenza CTL activity causes both prolonged viral shedding and increased viral spread through the respiratory tract.

Influenza immunization: intranasal live vaccinia recombinant contrasted with parenteral inactivated vaccine

To compare the efficacy and duration of the immune response to local and systemic vaccination, Balb/c mice were vaccinated either intraperitoneally (i.p.) with an inactivated A/PR/8/34 (H1N1) vaccine or intranasally (i.n.) with a vaccinia recombinant containing the H1 gene of influenza. The i.p. inactivated vaccine stimulated high serum IgG anti-influenza titres and protected the lungs against viral challenge for the duration of the experiment (17 months). Little nasal wash IgA was induced and the noses were susceptible to challenge. Animals vaccinated i.n. with the recombinant had lower serum IgG titres and the lungs showed poor protection against challenge. Nasal wash IgA titres were higher, however, and the noses were largely protected from viral challenge for 17 months.

Influenza in senescent mice: impaired cytotoxic T-lymphocyte activity is correlated with prolonged infection

Influenza and pneumonia are leading causes of death in the elderly. Cytotoxic T-lymphocyte activity is responsible for viral clearance after infection and declines with age. We hypothesized that following intranasal infection with influenza virus, aged mice would have decreased anti-influenza cytotoxic T-lymphocyte activity that would correlate with prolonged pulmonary viral shedding. To test this, young (1.5-4.0 month) and aged (22-25 month) BALB/c mice were infected intranasally with influenza A/Port Chalmers/1/73(H3N2). Mice were killed at 3-19 days following infection. Their splenic cytotoxic T-lymphocyte activity was measured by a secondary in vitro chromium release assay. Pulmonary viral titres were quantified by growth of titrated lung specimens in fertilized hens' eggs. Serum antibody titres were measured by an ELISA. Young mice responded in a relatively homogeneous fashion. They developed maximal cytotoxic T-lymphocyte activity of 60.9 +/- 2.0% by Days 11-13, and all except one cleared virus from the lung by Day 7. In contrast, old mice were heterogeneous. Their cytotoxic T-lymphocyte activity peaked at 46.9 +/- 5.0% and was delayed by 5-7 days. Forty-five per cent were still shedding virus at Days 7 and 8, and shedding persisted for at least 13 days in some mice. There was a strong correlation in both young and aged mice between the presence of virus in the lungs and decreased splenic cytotoxic T-lymphocyte activity (chi 2 = 30.2, P much less than 0.001). No significant difference was found between young and aged animals in serum IgG1 anti-H3 antibody titres. We conclude that following influenza infection in aged mice, impaired cytotoxic T-lymphocyte activity leads to prolonged duration of infection. These observations may lead to a better understanding of the excess morbidity and mortality in elderly persons that occur with influenza.

Passive transfer of local immunity to influenza virus infection by IgA antibody

Secretory IgA is presumed to be the mediator of mucosal immunity based on many studies that show a correlation between protection and secretory IgA titers; however, a causal relationship has not yet been established. Classically, passive transfer of antibody has been used to demonstrate causality, but the passive transfer of local immunity with physiologically transported IgA has not been previously reported. In this study mice were injected intravenously with polymeric IgA (pIgA), monomeric IgA (mIgA), or IgG1 mAb specific for the H1 hemaglutinin of PR8 influenza virus. pIgA was shown to be specifically transported into nasal secretions relative to the mIg. The transported pIgA was functional, as evidenced by its ability to bind to virus in an ELISA assay and to protect nonimmune mice against intranasal infection with H1N1 but not H3N2 influenza virus. Intravenous injection of similar virus-neutralizing doses of anti-influenza IgG1 mAb did not protect against nasal viral challenge. IgA-mediated protection could be abrogated by the intranasal administration of antiserum against the alpha chain of IgA. These data demonstrate the passive transfer of local immunity by the i.v. administration of pIgA antibody and show that the IgA in secretions can protect against influenza virus infection. This general approach could provide a model for the evaluation of the role of local IgA in host defense against other pathogens.

Passive transfer of local immunity to influenza virus infection by IgA antibody

Secretory IgA is presumed to be the mediator of mucosal immunity based on many studies that show a correlation between protection and secretory IgA titers; however, a causal relationship has not yet been established. Classically, passive transfer of antibody has been used to demonstrate causality, but the passive transfer of local immunity with physiologically transported IgA has not been previously reported. In this study mice were injected intravenously with polymeric IgA (pIgA), monomeric IgA (mIgA), or IgG1 mAb specific for the H1 hemaglutinin of PR8 influenza virus. pIgA was shown to be specifically transported into nasal secretions relative to the mIg. The transported pIgA was functional, as evidenced by its ability to bind to virus in an ELISA assay and to protect nonimmune mice against intranasal infection with H1N1 but not H3N2 influenza virus. Intravenous injection of similar virus-neutralizing doses of anti-influenza IgG1 mAb did not protect against nasal viral challenge. IgA-mediated protection could be abrogated by the intranasal administration of antiserum against the alpha chain of IgA. These data demonstrate the passive transfer of local immunity by the i.v. administration of pIgA antibody and show that the IgA in secretions can protect against influenza virus infection. This general approach could provide a model for the evaluation of the role of local IgA in host defense against other pathogens.

Influenza: pathogenesis and host defense

Why does influenza virus variously eventuate in mild upper respiratory tract infection, bacterial pneumonia, or rapidly fatal viral pneumonia? The depth of infection is important. So is competence of immunologic effectors--local antibody (secretory IgA) for preventing URI, systemic antibody for preventing pneumonia, and cellular immunity for recovery from either.

Enhancement of anti-influenza cytotoxic T-lymphocyte activity in senescent mice by vaccination early in life

The elderly suffer significantly from influenza and respond poorly to influenza vaccines. This may be due to the fact that cytotoxic T-lymphocyte (CTL) activity is responsible for recovery from viral infections and is decreased in the elderly. We hypothesized that vaccination early in life might increase activity in senescence. To test this, groups of BALB/c mice were infected with influenza virus and/or vaccinated with an inactivated vaccine. CTL activity was measured by 51Cr release from H1N1-infected P815 cells. We found that aged mice have low CTL activity when initially vaccinated at 22 months (4 +/- 4% vs. 23 +/- 6% for vaccinated young mice). However, CTL activity was significantly increased when animals were initially vaccinated when young and then re-vaccinated when old (28 +/- 10% vs. 13 +/- 17% for mice vaccinated twice in old age). We next measured CTL activity in response to infection. We found a very high level of activity (57 +/- 11%) in animals vaccinated at 1.5 months and then infected at 23 months. This was indistinguishable from young controls (56 +/- 7%). These data suggest that primary inoculation at an early age induces a relatively larger number of precursor CTLs than does inoculation in senescence.

Intranasal immunization with proteoliposomes protects against influenza

Worldwide, influenza virus remains a serious disease which has successfully eluded numerous attempts to design a consistently effective vaccine. In part, these attempts have been thwarted because of a lack of basic understanding of the mechanisms which mediate protection and recovery from influenza infection. A better understanding of the roles of secretory antibody, serum antibody and cell mediated immunity vis-à-vis protection and recovery from influenza infection has allowed us more rationally to approach the design and administration of a vaccine for influenza. We have constructed a vaccine composed of glycoproteins from the envelopes of either influenza of Sendai virus embedded in a lipid bilayer (immunosomes) mimicking the presentation of the virus to the cells during natural infection. Intranasal immunization with these immunosomes induces an adequate systemic Ir compared with intramuscular immunization and a superior local IgA response. These animals were specifically protected from virus challenge.

Virus infection as a stressor: influenza virus elevates plasma concentrations of corticosterone, and brain concentrations of MHPG and tryptophan

Balb/c mice were infected with influenza virus PR8 (H1N1) by the intranasal route. At various subsequent times, brain samples were examined for their content of catecholamine and indoleamine metabolites, and plasma corticosterone was measured. Virus infection was associated with a progressive loss of body and thymus weights, and an increase in plasma corticosterone. Spleen weight initially increased then decreased. There were also increases in the cerebral content of free tryptophan throughout the brain, and of MHPG, a major catabolite of norepinephrine, especially prominent in the hypothalamus. Thus influenza virus can be regarded as a stressor because, like behavioral stressors, it activates the hypothalamic-pituitary-adrenal axis, and increases cerebral concentrations of tryptophan and norepinephrine catabolites. These changes resemble those observed following administration of sheep red blood cells and Newcastle disease virus, noninfectious activators of the immune system, suggesting that noradrenergic and HPA activation are common concomitants of antigenic stimulation. The mediator of these effects may be interleukin-1 released by activated macrophages. It should be noted that animals infected with viruses can be expected to exhibit stress-like endocrine and neurochemical changes.

Passive serum antibody causes temporary recovery from influenza virus infection of the nose, trachea and lung of nude mice

BALB/c normal and nude mice were infected with a non-lethal mouse-passaged A/PC/1/73 (H3N2) influenza virus in order to assess the role of T cells on the course of disease of the nose, trachea and lung. The tracheal epithelium of both mouse strains was desquamated by 3 days after infection. Although normal regeneration began, nude mice never completed that regeneration whereas normal mice had fully regenerated tracheas by Day 14. This failure to complete the recovery was also evident from the continued virus shedding by the nude mouse. In order to assess the role of serum antibody on recovery from infection, ferret, goat or mouse antibody to H3N2 influenza virus was passively administered to nude mice after infection. It resulted in a transient decrease in virus shedding from the nose, trachea and lung, and complete but temporary regeneration of the tracheal epithelium. However, later in the course of the infection, when serum antibody levels were no longer detectable, the tracheal epithelium of these animals redesquamated and large amounts of virus were again shed from nose, trachea and lungs. We conclude that: (i) desquamation of the ciliated epithelium of the trachea is not T-cell dependent; and (ii) serum antibody can contribute to temporary recovery from infection, but by itself is insufficient for permanent recovery of the nose, trachea or lung.

Effect of upper respiratory infection on hearing in the ferret model

In an effort to develop an adult animal model for acquired viral-induced hearing loss, three groups of mature ferrets were inoculated intranasally with respiratory viruses (influenza A/Port Chalmers, influenza B/Mass, and parainfluenza I), which have been implicated as causative agents in idiopathic sudden hearing loss (ISHL). All ferrets challenged with influenza A/Port Chalmers (A/PC) exhibited clinical signs of infection, but neither of the other two groups exhibited such signs. Conductive and/or sensorineural hearing losses were demonstrated in eight of 15 ferrets challenged with influenza A/PC and four of 10 ferrets in the group challenged with influenza B/Mass by brainstem auditory-evoked responses (BAERs) and acoustic immittance. None of the four ferrets infected with parainfluenza I demonstrated auditory dysfunction. When auditory changes were observed, nasal washes were performed, and tissues of the middle and inner ears were collected for viral assay and morphologic examination. All ferrets demonstrating auditory changes were shown to be infected by isolation of virus from nasal tissues. Virus was isolated from eustachian tube tissue in six of the eight ferrets infected with influenza A/PC, which also demonstrated altered BAERs and one of the four infected with influenza B/Mass, which also had auditory changes. Virus was isolated from the middle ear of two ferrets infected with influenza A/PC and from the inner ear of another two ferrets from the same group. These data suggest that influenza A/PC has a greater effect on auditory function in the ferret model than either influenza B/Mass or parainfluenza I and that the ferret may be an appropriate adult model to examine the etiologic role of viral upper respiratory tract infections in some acquired hearing impairments.

Effect of passive maternal antibody on influenza illness in children: a prospective study of influenza A in mother-infant pairs

To determine the effect of passive antibody on the incidence of influenza in infants, infants born to mothers with serum antibody to influenza A (immune) and those born to mothers without evidence for this serum antibody (non-immune) were followed during the influenza H1N1 epidemic of 1979. Immune mothers had higher H1-specific antibody titers before the epidemic (P less than 0.001), were less frequently culture positive, showed fewer titer rises (P less than 0.001) and were less symptomatic than were nonimmune mothers. Infants of immune mothers had higher H1-specific passive antibody titers that correlated with their mother's antibody titers. Although infants of both groups showed no difference in incidence of influenza infection, infants of immune mothers had influenza symptoms that were delayed in onset (P = 0.02) and were of shorter mean duration compared with infants of nonimmune mothers. These findings suggest that passive maternal antibody delays the onset and decreases the severity of influenza disease in young infants.

Protection and recovery in influenza virus-infected mice immunosuppressed with anti-IgM

BALB/c mice, immunosuppressed from birth with goat anti-mouse IgM, were able to recover from influenza virus infection in the absence of detectable serum and nasal antibody. Recovery was delayed a few days when compared with control animals. Antibody-deficient mice, that had recovered from an initial influenza virus infection, i.e., convalescent mice, were subsequently rechallenged with homologous influenza virus in order to study the importance of nasal and serum antibody in prevention of infection. Convalescent mice were susceptible to reinfection when nasal and serum antibody were not detectable. The mice were resistant to reinfection when serum and/or nasal antibody was detectable by radioimmunoassay. Normal mice that were passively immunized with high titer mouse anti-influenza virus serum were susceptible to challenge with homologous influenza virus. The serum antibody levels in these mice were higher than most of those found in the immune convalescent mice suppressed with anti-IgM, thereby suggesting that the serum antibody, found in convalescent suppressed mice, is not protective. We conclude that 1) mice can recover from influenza virus infection in the absence of detectable levels of nasal and serum antibody, thus indirectly confirming the role of cell-mediated immunity in recovery; 2) serum IgM, IgG2A, IgG2B, IgG3, and probably IgG1 antibody levels are not responsible for protection against influenza virus infection of the upper respiratory tract; and 3) nasal IgA antibody correlates best with protection against reinfection of the upper respiratory tract, but some other locally protective agent cannot be excluded.

Protection and recovery in influenza virus-infected mice immunosuppressed with anti-IgM

BALB/c mice, immunosuppressed from birth with goat anti-mouse IgM, were able to recover from influenza virus infection in the absence of detectable serum and nasal antibody. Recovery was delayed a few days when compared with control animals. Antibody-deficient mice, that had recovered from an initial influenza virus infection, i.e., convalescent mice, were subsequently rechallenged with homologous influenza virus in order to study the importance of nasal and serum antibody in prevention of infection. Convalescent mice were susceptible to reinfection when nasal and serum antibody were not detectable. The mice were resistant to reinfection when serum and/or nasal antibody was detectable by radioimmunoassay. Normal mice that were passively immunized with high titer mouse anti-influenza virus serum were susceptible to challenge with homologous influenza virus. The serum antibody levels in these mice were higher than most of those found in the immune convalescent mice suppressed with anti-IgM, thereby suggesting that the serum antibody, found in convalescent suppressed mice, is not protective. We conclude that 1) mice can recover from influenza virus infection in the absence of detectable levels of nasal and serum antibody, thus indirectly confirming the role of cell-mediated immunity in recovery; 2) serum IgM, IgG2A, IgG2B, IgG3, and probably IgG1 antibody levels are not responsible for protection against influenza virus infection of the upper respiratory tract; and 3) nasal IgA antibody correlates best with protection against reinfection of the upper respiratory tract, but some other locally protective agent cannot be excluded.

A case report of the successful treatment of recurrent aphthous stomatitis with some preparations of orally administered transfer factor

A patient with severe disabling recurrent aphthous stomatitis (RAS) was treated with four different preparations of oral human transfer factor (TF), as well as placebo, following a double-blind protocol. Two of the TF preparations had a significant effect upon the course of the patient's illness by prolonging the interval between attacks and decreasing the severity of attacks. No side effects attributable to any of the preparations were noted by the patient. Thus, some but not all preparations of human transfer factor given orally are an effective therapy for RAS.

Influenza infection in the infant mouse

A nonlethal influenza infection [A/PC/1/73 (H3N2)] was given to infant mice to determine (1) the pathology of tracheal epithelium and lung, (2) the time course of viral shedding from the nose and lung, and (3) the subsequent development of protective immunity during adulthood. Both desquamation of the tracheal epithelium and lung pathology similar to that described in adults after influenza infection were observed in the infant. Animals infected at 3 days of age show virus shedding in 12 of 13 infant mice that persists for at least 2 days longer than in the adult. This longer duration of influenza infection did not result from either malnutrition or from intralitter transmission of virus. Recovery from virus shedding in both the upper and lower airway occurred in the absence of detectable serum antibody in six of seven mice. Infants that recover from infection, when rechallenged during adulthood, manifest complete protection in 11 of 13 mice after nonlethal challenge and no mortality after lethal challenge.

Maternal-infant transfer of influenza-specific immunity in the mouse

The effects of maternal-infant transfer of influenza-specific antibody on influenza infection in the infant mouse were studied by following mortality, hemagglutination inhibition antibody, virus shedding from the nose and lung, and pathology of the upper and lower airway. By cross-fostering infants, influenza-specific antibody was shown to be acquired mainly by breast-feeding. Mice acquiring specific antibody survived lethal influenza infection (p less than 0.001) and had no evidence of influenza pneumonitis. There was variable suppression of nasal virus shedding and tracheal desquamation. Infected infants that initially acquired high levels of serum antibody also showed no evidence for serum antibody 10 wk later. Infant mice surviving initial influenza infection were lethally rechallenged 10 wk later. Rechallenged mice had a higher survival rate when compared to control mice (p less than 0.001) in spite of the absence of anti-influenza antibody and the presence of high lung virus titers in both groups 1 day after rechallenge. Rechallenged mice showed evidence for both significantly lower nasal virus titers (p less than 0.001) and a secondary serum antibody response with associated decline in lung virus titer. These results suggest maternal influenza-specific antibody a) is transferred to the infant mouse; b) is transferred mainly by breast-feeding; c) is life saving and lowers lung virus titers in the infant; and d) suppresses the infant's serum antibody production after challenge without affecting local immunity or the ability to mount a secondary antibody response.

Maternal-infant transfer of influenza-specific immunity in the mouse

The effects of maternal-infant transfer of influenza-specific antibody on influenza infection in the infant mouse were studied by following mortality, hemagglutination inhibition antibody, virus shedding from the nose and lung, and pathology of the upper and lower airway. By cross-fostering infants, influenza-specific antibody was shown to be acquired mainly by breast-feeding. Mice acquiring specific antibody survived lethal influenza infection (p less than 0.001) and had no evidence of influenza pneumonitis. There was variable suppression of nasal virus shedding and tracheal desquamation. Infected infants that initially acquired high levels of serum antibody also showed no evidence for serum antibody 10 wk later. Infant mice surviving initial influenza infection were lethally rechallenged 10 wk later. Rechallenged mice had a higher survival rate when compared to control mice (p less than 0.001) in spite of the absence of anti-influenza antibody and the presence of high lung virus titers in both groups 1 day after rechallenge. Rechallenged mice showed evidence for both significantly lower nasal virus titers (p less than 0.001) and a secondary serum antibody response with associated decline in lung virus titer. These results suggest maternal influenza-specific antibody a) is transferred to the infant mouse; b) is transferred mainly by breast-feeding; c) is life saving and lowers lung virus titers in the infant; and d) suppresses the infant's serum antibody production after challenge without affecting local immunity or the ability to mount a secondary antibody response.

Outcome of influenza infection: effect of site of initial infection and heterotypic immunity

An infection established throughout the total respiratory tract of mice with a highly lung adapted influenza virus (H0N1) led to death from viral pneumonia. The 50% lethal dose (LD(50)) was approximately the same as the 50% infectious dose (ID(50)). An infection with the same virus initiated in the nasal mucosa spread to the trachea and lungs over a 3- to 5-day period but was not lethal except at very high infecting doses. The LD(50) was 30,000 times the ID(50). Mice that had recovered from a prior infection with A/PC/73(H3N2) demonstrated enhanced recovery (heterotypic immunity) when challenged with A/PR/8/34(H0N1). Heterotypically immune mice infected while anesthetized with this potentially lethal virus stopped shedding virus from the nose, trachea, and lungs by day 7 and recovered. Heterotypically immune mice, infected awake, stopped shedding virus from the nose by day 5, and, in fact, the virus did not spread to the trachea or lungs. Thus, some of the variation in the severity of influenza infections may be explained by two factors: the site of initial infection and previous infection with heterotypic influenza virus.

Autopsies on two native American Mummies

An interdisciplinary team performed autopsies on an adult male and an infant male mummy from the American Southwest. Cause of death has not been determined for the infant. The presence of an unhealed skull fracture associated with an apparent hematoma in the adult male is suggestive of trauma as the cause of death in the adult. Evidence of disease is minimal. Analysis of powder thought to be dried blood from the thoracic cavity of the adult suggests the presence of human IgG. The instability of this protein may indicate the presence of proteolytic activity by enzymes that degrade immunoglobulins upon rehydration. The possibility of enzymatic degradation of proteins will be an important factor in future studies of such immunoglobulins in mummy remains and also indicates the importance of maintaining the desiccated condition of mummy tissues.

Heterotypic immunity to influenza in ferrets

Heterotypic immunity to influenza virus in ferrets operated against heterotypic influenza viruses but not heterologous viruses. Contrary to prior reports, the protection conferred lasted for at least 18 months. This type of immunity limited virus shedding but did not prevent infection. These results suggest that this phenomenon could play a role in determining the severity of infections caused by type A influenza viruses in humans.

Adherence of Pseudomonas aeruginosa to tracheal cells injured by influenza infection or by endotracheal intubation

Adherence of Pseudomonas aeruginosa to normal, injured, and regenerating tracheal mucosa was examined by scanning electron microscopy. Uninfected and influenza-infected murine tracheas were exposed to six strains of P. aeruginosa isolated from human sources and one strain of platn origin. All of the strains tested adhered to desquamating cells of the infected tracheas, but not to normal mucosa, the basal cell layer, or the regenerating epithelium. Adherence increased when the incubation time of the bacteria with the trachea was prolonged. Strains isolated from human tracheas appeared to adhere better than strains derived from the urinary tract. After endotracheal intubation of ferrets, P. aeruginosa adhered only to the injured cells and to areas of exposed basement membrane. We call this phenomenon "opportunistic adherence" and propose that alteration of the cell surfaces or cell injury facilitates the adherence of this bacterium and that adherence to injured cells may be a key to the pathogenesis of opportunistic Pseudomonas infections.

Murine influenzal tracheitis: a model for the study of influenza and tracheal epithelial repair

The murine model of influenza virus infection is generally a lethal pneumonitis produced by a highly mouse-adapted virus. However, we infected mice with a less adapted virus and produced a nonlethal disease that involved the airways without producing gross pneumonitis. Changes that occurred in the tracheal epithelium were studied by scanning and transmission electron microscopy. Complete desquamation of the epithelium occurred within 3 days after infection, regeneration began within 5 days, and repair was complete within 2 wk after infection. This model is proposed as an alternative to the lethal pneumonitis for the study of murine influenza and also as a model for the study of repair of the respiratory ciliated epithelium.

Experimental IgA nephropathy

An animal model for IgA immune complex nephritis was developed. IgA immune complexes formed in vitro with an IgA anti-dinitrophenyl (DNP) derived from MOPC-315 plasmacytoma, and dinitrophenylated bovine serum albumin (DNP-BSA) produced mild focal glomerulonephritis in mice. Similar, but more severe pathological changes were produced with complexes formed in vivo either in normal mice or MOPC-315 tumor-bearing mice. In contrast to the focal nature of the PAS-positive glomerular lesions observed by light microscopy, immunofluorescent examination revealed IgA deposits in all glomeruli. This discrepancy between immunofluorescent and histopathologic findings as well as the distribution of the immune complexes within the affected glomeruli, are some of the features which bear resemblance between this experimental model and human IgA nephropathy. Fixation of complements by DNP-BSA-IgA immune complexes, formed in vitro or in vivo, was shown to occur in the glomeruli of mice with IgA immune complex nephropathy. The pattern of C3 glomerular deposits was similar to that of IgA. However, complement proved to be nonessential for complex deposition. This conclusion is based on the observation that decomplemented mice, although showing no deposition of C3 in their glomerulus, developed glomerular immunohistological changes similar to those observed in experimental mice that were not decomplemented. Polymeric IgA was observed to be critical for renal deposition of complexes and induction of nephritic histological changes. In contrast, monomeric IgA immune complexes failed to produce glomerular deposits. This finding raises the possibility that secretory IgA, which is predominantly polymeric, may play a role in human IgA-associated glomerulonephritis.

Serum antibody prevents lethal murine influenza pneumonitis but not tracheitis

This paper reports studies showing the effects of serum antibody upon influenza infection at two different sites: the trachea and lung. Tracheal desquamation, pulmonary consolidation, death, and virus shedding were examined after infection of mice with a lethal A/Port Chalmers/1/73 (H3N2) influenza virus. Immune serum administered intraperitoneally before infection prevented death and pulmonary consolidation and also significantly lowered lung virus shedding as compared with controls receiving normal serum. However, this protection did not extend to the ciliated epithelium of the trachea because serum antibody did not prevent desquamation of the trachea or significantly decrease viral yield from the trachea. These results indicate that serum antibody is protective against severe pulmonary parenchymal disease but not for disease of the ciliated epithelium.