Induction and characterization of delayed-type hypersensitivity to influenza virus in mice

The emerging role of probiotics as a mitigation strategy against coronavirus disease 2019 (COVID-19)

COVID-19 is an acute respiratory infection accompanied by pneumonia caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which has affected millions of people globally. To date, there are no highly efficient therapies for this infection. Probiotic bacteria can interact with the gut microbiome to strengthen the immune system, enhance immune responses, and induce appropriate immune signaling pathways. Several probiotics have been confirmed to reduce the duration of bacterial or viral infections. Immune fitness may be one of the approaches by which protection against viral infections can be reinforced. In general, prevention is more efficient than therapy in fighting viral infections. Thus, probiotics have emerged as suitable candidates for controlling these infections. During the COVID-19 pandemic, any approach with the capacity to induce mucosal and systemic reactions could potentially be useful. Here, we summarize findings regarding the effectiveness of various probiotics for preventing virus-induced respiratory infectious diseases, especially those that could be employed for COVID-19 patients. However, the benefits of probiotics are strain-specific, and it is necessary to identify the bacterial strains that are scientifically established to be beneficial.

The induction and control of delayed type hypersensitivity reactions induced in chickens by infectious bronchitis virus

Infectious bronchitis virus (IBV) was shown to induce delayed type hypersensitivity (DTH) reactions in the wattle, or to inhibit migration in a macrophage migration inhibition test (MIT) in sensitised birds. The magnitude of the reactions was related to the sensitising dose of the virus. The optimal dose for the cold attenuated A3-IBV was 10(3 .5) EID50, higher doses giving lower responses. Birds given a similar dose of T-IBV had negative DTH reactions, but the spleen non-adherent lymphocytes from these unreactive birds, and also birds sensitised with 10(6.5) EID50 of A3 virus, on transfer to allogeneic birds sensitised with the optimal dose of A3 virus (10(3.5) EID50) suppressed their DTH response. Treatment of birds with dexamethasone, 6-mercaptopurine, or cyclophosphamide, before vaccination with the dose of A3 virus which suppressed the DTH reaction (10(6.5)EID50), abrogated the DTH unresponsiveness. Drug treatment before optimal sensitisation (10(3 .5) EID50) did not increase the magnitude of the DTH response, but prolonged the time over which the DTH response could be elicited. MIT results mirrored the DTH responses. The antigens elicitating the response, or the transferred cells suppressing the response, derived from chickens immunised with any of the three strains of IBV studied had similar effects on DTH and MIT responses in A3 virus sensitised birds.

Oral intake of Lactobacillus fermentum CECT5716 enhances the effects of influenza vaccination

OBJECTIVE

We studied the coadjuvant capability of oral consumption of the breast-milk-isolated strain Lactobacillus fermentum (CECT5716) for an anti-influenza vaccine.

METHODS

A randomized, double-blinded, placebo-controlled human clinical trial including 50 volunteers (31 male and 19 female) was performed to address the immunologic effects of an intramuscular anti-influenza vaccine in adults (33.0 +/- 7.7 y old). Fifty percent of volunteers received an oral daily dose of methylcellulose (placebo) or probiotic bacteria (1 x 10(10) colony-forming units/d) 2 wk before vaccination and 2 wk after vaccination.

RESULTS

Two weeks after vaccination there was an increase in the proportion of natural killer cells in the probiotic group but not in the placebo group. The vaccination induced an increase in T-helper type 1 cytokine concentrations and in T-helper and T-cytotoxic proportions in both groups; however, the probiotic group showed a significant higher induction in some of these parameters. Regarding the humoral effects, induction of antibody response in the placebo group could not be detected. In the case of the probiotic group, a significant increase in antigen specific immunoglobulin A was detected. Although an increase in total immunoglobulin M was observed, changes in anti-influenza antigen specific immunoglobulin M were not observed. The incidence of an influenza-like illness during 5 mo after vaccination (October to February) was lower in the group consuming the probiotic bacteria.

CONCLUSION

Oral administration of the strain L. fermentum CECT5716 potentates the immunologic response of an anti-influenza vaccine and may provide enhanced systemic protection from infection by increasing the T-helper type 1 response and virus-neutralizing antibodies.

Erythrocytes enhance the immunogenicity of oral vaccination with gamma irradiated influenza virus: increasing the dose of irradiation results in a significant diminution of lung IgA response

Previous studies have demonstrated that the ability of gamma-irradiated whole influenza virus to prime for specific anti-influenza antibody responses was dramatically enhanced when delivered in a complex with chicken red blood cell ghosts (cRBC). The purpose of this study was to investigate the effect of increasing the dose of gamma irradiation used to inactivate A/Queensland/6/72 virus on the ability of the virus-cRBC complex to prime for specific influenza responses. Spleen cell proliferation studies confirmed the enhancing effect of the cRBC carrier for oral vaccination with irradiated virus. Cells from mice vaccinated with 30 kGy-irradiated virus only did not respond to influenza stimulation in vitro, whereas cells from mice vaccinated with irradiated virus+cRBC showed significant increases in proliferation to antigen exposure. No significant antibody response or challenge virus clearance was observed in mice orally vaccinated with irradiated (13.1 or 30 kGy) virus alone, even when the dose was increased significantly. Oral vaccination with live virus (+/-cRBC) primed for significant influenza specific IgA responses in the lungs, in addition to IgG responses in the lungs and sera. The dose of irradiation used to inactivate the virus was found to be critical to the profile of antibody response when the virus was delivered in a complex with cRBC. Oral vaccination of Swiss mice with 13.1 or 30 kGy virus (+cRBC) primed for significant serum and lung IgG responses. Lung IgA responses for 13.1 kGy+cRBC vaccinated mice were detected, but 30 kGy+cRBC vaccinated Swiss and CBA/H mice had no significant lung IgA response. The abrogation of IgA response, however, did not lessen the clearance of live challenge virus in outbred mice, suggesting a primary role for IgG and/or CTL response in the control of influenza virus infection post oral vaccination. To ensure direct comparison of virus alone and virus+cRBC treatments, the concentration of virus complexed to the cRBC was determined.

Antibodies raised against peptide fragments of CD16 reacting with membrane and soluble form of CD16. I: Production and characterization

Monoclonal antibodies (MAbs) were generated against human CD16 (Fc gamma RIII) by fusion of NS1 myeloma cells with spleen cells from BALB/c mice immunized with synthetic peptide sequences derived from the CD16 genes. After screening, four hybridomas secreting MAbs (2 IgM and 2 IgG) were selected, cloned and characterized for their activity against CD16 by ELISA test, flow cytometry, rosette inhibition and immuno-blotting. MAbs reacted strongly in ELISA with a soluble form of CD16 (sCD16) present in human serum and to a lesser degree with soluble recombinant CD16 (srCD16). The binding characteristics of the four antibodies to the sCD16 were different, implying that the antibodies recognize different CD16 epitopes. FACS analysis of peripheral blood from healthy volunteers demonstrated that these MAbs are highly reactive with membrane CD16 of neutrophils cells (70-95%) and with a subset of lymphocytes (6-14%). These MAbs seem interesting and may lead to the purification of the soluble human CD16 and to the knowledge of its functions, its physiological role and the cellular polymorphism.

The influence of different adjuvants on the immune response to a synthetic peptide comprising amino acid residues 9-21 of herpes simplex virus type 1 glycoprotein D

The immuno-modulating properties of different adjuvant systems on the murine humoral and cellular immune response to a synthetic peptide comprising amino acid residues 9-21 of glycoprotein D of herpes simplex virus type 1 (HSV-1) were investigated. For immunization, the peptide was conjugated to ovalbumin or bovine serum albumin by glutaraldehyde and the adjuvants used in this study were Freund's complete adjuvant (FCA), aluminium hydroxide, the Ribi adjuvant system (RAS) and two non-ionic block polymer surfactants, viz. L101 and 31R1, in oil in water emulsions. High anti-peptide antibody titers were obtained after immunization with FCA, aluminium hydroxide, RAS and L101. All adjuvants, except RAS, stimulated the induction of delayed type hypersensitivity obtained after immunization with peptide 9-21 coupled to ovalbumin and elicited by injection of purified HSV-1 virions in the footpad. Challenge with a lethal dose of HSV-1 showed that mice immunized with peptide 9-21 coupled to ovalbumin in combination with FCA, RAS and L101, respectively, were significantly protected. Although immunization with peptide 9-21 coupled to ovalbumin combined with aluminium hydroxide stimulated induction of delayed type hypersensitivity, no significant protective immunity against the challenge was generated.

Murine helper T lymphocyte response to influenza virus: recognition of haemagglutinin by subtype-specific and cross-reactive T cell clones

Helper T cel lines specific for influenza virus were established by continuous culture of Mem 71-Bel (H3) virus-immune spleen cells in the presence of virus and antigen-presenting cells and their specificity assessed in proliferation experiments. A line stimulated in vitro with Mem 71-Bel virus was able to proliferate in response to viruses of the same, and also of different, type A haemagglutinin (HA) subtypes as the immunizing virus but not to a type B influenza virus. A component of this cross-reactivity was due to recognition of the HA molecule. Lines stimulated in vitro with purified disrupted H3 or H2 viruses showed a higher degree of cross-reactivity. Of nine clones isolated from these lines, seven were directed against the HA molecule and recognized the HA1 chain. The HA-specific T cell clones were either subtype-specific T cell clones were either subtype-specific, recognizing only viruses of the H3 subtype, or cross-reactive, also recognizing viruses of the H2 subtype of type A (but not type B). Subtype-specific and cross-reactive T cell clones were shown to function as helper T cells in vitro. In addition to collaborating with H3 virus-primed B cells responding to H3 virus in culture, the cross-reactive T cell clone could also provide help for H2 virus-primed B cells making anti-HA antibody in response to H2 virus.

Host antigens associated with haemagglutinin

A delayed-type hypersensitivity (DTH) test has been used to detect the presence of host-specific antigen(s) is highly purified egg-grown influenza virus, virus components and isolated haemagglutinin. Cyclophosphamide-treated mice, primed with an extract from allantoic fluid, showed DTH reactions when challenged with preparations containing envelope lipid or polymer-type subunits, whereas lipid-free derivatives such as internal virus protein complexes and monomer haemagglutinin preparations lacked the activity. This approach has been extended to demonstrate the presence of associated host antigens in SV40-vector expressed haemagglutinin produced in simian cells.

The effect of prenatal chlordane exposure on specific anti-influenza cell-mediated immunity

Previous studies in our laboratory have documented that in utero chlordane exposure caused a significant enhancement in the survival of the offspring to influenza A virus infection, and a depressed delayed type hypersensitivity (DTH) response to oxazolone. To correlate these 2 effects, we assayed influenza A virus-specific DTH response, and found that it was significantly decreased in chlordane-treated offspring. Virus-specific T-cell blastogenesis was also assayed in chlordane-treated animals. No significant differences due to the chlordane treatment were found in virus-specific T-cell blastogenesis, suggesting that the DTH depression did not result from a paucity of antigen-reactive T-cells. To determine whether enhanced survival was due, in part, to the effects of chlordane on virus replication, rather than on immunological alteration alone, the kinetics of influenza virus replication in the lungs of chlordane- and vehicle-treated animals were determined. In utero chlordane treatment caused no significant differences in in vivo virus replication. These data suggest that increased survival was due to a decrease in virus-specific DTH and its associated pathology.

The estimation of host antigen in experimental and commercial influenza subunit preparations by delayed-type hypersensitivity reaction

A delayed-type hypersensitivity (DTH) test has been used to detect the presence of host-specific antigen(s) in highly-purified egg-grown influenza virus and virus components. Cyclophosphamide-treated mice, primed with an extract from allantoic fluid, showed DTH reactions when challenged with whole virus, spikeless virus particles or polymer-type subunits. All commercial egg-grown influenza vaccines showed the presence of host antigen, whereas lipid-free derivatives such as internal virus protein complexes and monomer HA preparations lacked the activity. These findings are discussed in relation to vaccine application.

Specific suppression of humoral and delayed hypersensitivity responses by cyclophosphamide in an experimental model of autoimmunity

The aim of this report is to investigate the effect of cyclophosphamide (CY) in an experimental model of autoimmunity to rat male accessory glands. The results indicated that 100 mg/kg of this drug suppressed humoral immune response that persisted for at least 45 days when administered 3 days after the first immunization of rats with modified rat male accessory glands (MRAG) in complete Freund's adjuvant (CFA). Administration of the drug 3 days before ID injection of antigen caused a shorter suppression of antibody formation. Delayed type hypersensitivity (DTH) studied 13 days after the first immunization was suppressed only in the animals that were administered CY after the antigen. The specificity of the immunosuppression was studied in rats treated with CY after the first immunization with MRAG using aggregated human gamma-globulin (AHGG) as an unrelated antigen. The studies demonstrated significant suppression of DTH (p less than 0.005) and humoral immunity only against MRAG. On the contrary, the response to AHGG was not significantly modified.

Inhibition of pathogenic effect of effector T cells by specific suppressor T cells during influenza virus infection in mice

Mice infected with an aerosol of influenza type A virus, or immunized with purified UV-inactivated whole virus or with viral subunits, develop a transient delayed-type hypersensitivity (DTH) which peaks 5-7 days after immunization. The intensity of DTH is greatly enhanced and sustained when mice are pretreated with cyclophosphamide. The reaction is maximal 24 h after elicitation, has classical tuberculin-type histology and is transferable by immune H-21 region restricted Lyt-1+2- T cells (Td) but not by immune serum. These Td cells not only fail to protect mice against influenza virus infection, but increase the mortality rate due to influenzal pneumonia following challenge with homologous lethal virus. On the other hand, antigen-specific suppressor T (Ts) cells which inhibit DTH are readily generated during influenza virus infection, and are detectable for at least 40 days thereafter. The ease with which they are induced and maintained during the infection may be of evolutionary advantage. In support of this, we now report that these Ts cells can reverse the pathogenic effect of Td cells thereby demonstrating a beneficial influence of Ts cells in a viral disease.

Delayed-type hypersensitivity in mice after infection with avirulent Semliki Forest virus. Brief report

After subcutaneous infection of mice with Semliki Forest virus, a delayed-type hypersensitivity (DH) could be demonstrated by footpad swelling. Pretreatment with cyclophosphamide resulted in enhanced DH if neutralizing antibodies were undetectable in serum.

Unusual restriction of a proliferative line reacting with influenza A and B viruses

A human T-cell line, B3, has been obtained by cloning spleen cells at limiting dilutions in the presence of influenza-A-virus-infected autologous cells. B3 cells were OKT 3+4+8-, E rosetting+, Sig- and were HLA-DR (+) after stimulation and HLA-DR (-) when resting. They proliferate specifically in the presence of influenza-virus-infected cells. Remarkable is that (a) the proliferation was obtained with viruses of both A and B types and (b) only autologous cells seem to be able to present the viral antigen to B3 cells.

Delayed hypersensitivity to herpes simplex virus: murine model

Cell-mediated immunity has been shown to be clinically important in recovery from herpes simplex virus (HSV) infections. To investigate the role of delayed hypersensitivity (DH) in immunity and protection against HSV, we developed a murine model using the ear-swelling assay. Mice were infected subcutaneously with HSV-1 and ear-challenged, and the swelling was quantified. Significant ear swelling was detected by 3 to 4 days postinfection and peaked at 6 days. The kinetics of development of ear swelling were typical of DH: maximal swelling occurred 24 h post challenge and was diminished by 48 h, and the cellular infiltrate was predominantly mononuclear. Four-hour swelling, indicative of antibody-mediated, immediate-type hypersensitivity, was not detected until 15 days post immunization. The DH response was virus specific and could be transferred to normal recipients with lymph node T cells, but not with B cells or immune serum. This system will provide a useful model for evaluating the protective role of DH in HSV infection and for studying the specificity and interaction of T cells which mediate the response.

Regulation of delayed-type hypersensitivity to pathogens and alloantigens

Recent studies reinforce the notion that delayed-type hypersensitivity plays a key role in the host defence against microbial and intracellular parasitic infection, and in the rejection of skin allografts. F. Y. Liew reviews these studies and discusses the observation that this T-cell mediated immunity is profoundly regulated by antigen-specific suppressor T cells, some of which are restricted by products of the I-J subregion of the MHC.

Specificity of the helper T cell for the cytolytic T lymphocyte response to influenza viruses

We have described a model system in which helper T cells are required to mount a primary antiviral cytolytic T lymphocyte response. The radioresistant helper cell can be found in the spleens of mice that have been immunized subcutaneously with influenza viruses 6-8 d previously. These helper cells appear to be type specific but cross-reactive among the subtypes of influenza A viruses. The phenotypes of the interacting cell populations were determined.

Biological properties of an influenza A virus-specific killer T cell clone. Inhibition of virus replication in vivo and induction of delayed-type hypersensitivity reactions

We tested two biological properties of a continuously growing mouse cytotoxic T cell line, L4, which is specific for influenza A virus and has been cloned and recloned many times. We previously reported that L4 cells are H-2 restricted and cross-reactive for all type A influenza viruses, whereas they do not recognize type B influenza viruses. They bear Thy-1 and Lyt-2 markers. In the present study, we show that L4 cytotoxic T cells protect mice against a lethal influenza infection on transfer to syngeneic recipients, and reduce virus titers in the lungs of mice challenged with a heterologous type A influenza virus. This provides further support for the active role of cytotoxic T cells in limiting virus replication in influenza infection. We could also demonstrate that the cloned cytotoxic T cells induce a delayed-type hypersensitivity skin reaction in the footpads of mice challenged with live or inactivated influenza virus. This reaction can be observed at 24 h, but has declined by 48 h. A clone of cells derived from L4 that has lost its cytotoxic potential and its ability to recognize infected cells did not induce a delayed-type hypersensitivity reaction in the presence of virus. Thus, cytotoxic T cells actively killing influenza virus-infected cells are able to induce a delayed-type hypersensitivity skin reaction to homologous and heterologous type A influenza viruses.

The spread and persistence of influenza viruses in normal and cyclophosphamide-treated mice

The persistence and extrapulmonary spread of three strains of influenza virus, the mouse neuro-adapted A/NWS virus, the wild-type strain A/Victoria/75, and a recombinant virus RIT4050, bearing surface antigens derived from A/Victoria/75, were studied in both normal and cyclophosphamide-treated CBA mice following either intranasal or intracerebral inoculation. All three viruses showed increased lethality in mice in the presence of cyclophosphamide but exhibited distinctive patterns of replication and spread. The recombinant virus RIT4050 showed a reduced ability to replicate, persist, and spread in CBA mice compared to either A/NWS or A/Victoria/75 viruses, and in general, the A/NWS virus persisted to a greater extent than the A/Victoria/75 virus in both normal and treated mice. However, in the presence of cyclophosphamide, no extrapulmonary spread of A/NWS virus was observed. The reasons for the differences are discussed.

Cells mediating delayed-type hypersensitivity in the lungs of mice infected with an influenza A virus

Effector cells that demonstrate delayed-type hypersensitivity (DTH) on transfer with antigen to naive mice can be recovered from the lungs of mice inoculated intranasally 6 days earlier with a lethal dose (usually 5x10(1)EID50) of influenza A virus. The activity recovered was proportional to the dose of virus instilled intranasally and the extent of lung consolidation observed. Active cells could also be recovered from the draining lymph nodes and from the peripheral blood. The effector cells were identified as T lymphocytes of Ly 1 phenotype and required I-region sharing between donor and recipient for activity to be elicited. They were cross-reactive within the A group of influenza viruses. Two experiments are reported in which immune cell preparations that expressed DTH activity but had very little cytotoxic T cell activity were transferred to mice inoculated 1 or 2 days earlier with a lethal dose of virus. The mice were not protected from death, and in both experiments, the recipient mice died more rapidly than the controls. These results contrast with earlier results in which cell preparations with high cytotoxic T-cell activity were shown to protect recipient infected mice from death.

Cell cooperation in antibody responses to influenza virus. I. priming of helper t cells by internal components of virion

T cells recognizing internal components of the influenza virion can cooperate with B cells recognizing hemagglutinin to enhance the hemagglutinin inhibition (HAI) antibody response. Cooperation occurs only when the internal proteins and hemagglutinin are subsequently presented in association. The effect enhances the production of both 2-mercaptoethanol-resistant and -sensitive antibodies. The cooperating cells express the Thy-1+, Ly-1+2- surface phenotype and thus are characteristic of helper T cells. Immunization of mice with the internal components of the virion increases survival after exposure to lethal influenza infection. Mice primed with purified matrix protein produce enhanced amounts of HAI antibody after infection with influenza. These results may help to explain reports on the effects of heterotypic infection on antibody production, and also heterotypic immunity.

Delayed-type hypersensitivity to influenza virus. Induction of antigen-specific suppressor T cells for delayed-type hypersensitivity to hemagglutinin during influenza virus infection in mice

Mice infected with A/England/939/69 X A/Puerto Rico/8/34 (Rec 31) influenza virus by aerosol develop significantly lower levels of delayed-type hypersensitivity (DTH) to A/Hong Kong/1/68 X A/Puerto Rico/8/34/ (X31) virus compared to uninfected mice. The suppression of DTH to the hemagglutinin appears to be mediated by suppressor T cells which carry Lyt-1 membrane antigen marker, and not by sy serum antibody. The suppressor T cells for DTH induced by Rec 31 virus (H3N1) infection suppress the DTH response to the variants of the H3 subtype of influenza viruses, but have no effect on the DTH responses to A/Puerto Rico/8/34 virus (H0N1), a B influenza virus or the matrix protein of type A influenza virus. Suppressor T cells for DTH appear 2 wk after infection and are detectable in the spleen for at least 40 d thereafter. T-helper cells for antibody response to hemagglutinin are induced concomitantly with the T-suppressor cells for DTH. Possible implications of the present findings on the regulation of the immune response to viral infection are discussed.