The role of IL-2 and T4+ cells in the generation of human influenza virus-specific CTL activity

Influenza virus vaccination of patients with chronic lung disease

STUDY OBJECTIVES

To evaluate the safety of, and mucosal and systemic immune responses induced by two influenza virus vaccine regimens in subjects with COPD.

DESIGN

Single-center, blinded, randomized, prospective clinical trial evaluating two vaccine regimens.

SETTING

Outpatient clinics of St. Louis Department of Veterans Affairs Medical Center.

PARTICIPANTS

Volunteers (age range, 42 to 88 years) had preexisting COPD with severe obstruction to airflow on average, were male, and were not receiving immunosuppressive medication.

INTERVENTIONS

Twenty-nine volunteers were randomly assigned to receive either bivalent live attenuated influenza A virus vaccine (CAV) or saline solution placebo intranasally. All subjects also received an i.m. injection of trivalent inactivated influenza virus vaccine (TVV) simultaneously.

MEASUREMENTS AND RESULTS

Clinical status and pulmonary function measured by spirometry did not change significantly after vaccination. Using hemagglutinins (H1 and H3 HA) which more closely resembled those in CAV, mean levels of anti-HA immunoglobulin A (IgA) antibodies in nasal washings increased significantly after vaccination with CAV and TVV compared to prevaccination, but they did not increase significantly after TVV and intranasal placebo. Mean levels of influenza A virus-stimulated interleukin-2 and -4 produced by peripheral blood mononuclear cells in vitro increased significantly after administration of the combination vaccine regimen and to a lesser extent after TVV and intranasal placebo compared to respective prevaccination levels. The timing of the cytokine response appeared different following CAV and TVV compared to TVV and intranasal placebo.

CONCLUSIONS

Intranasally administered CAV was safe when given with i.m. administered TVV and there may be an immunologic advantage to administration of the combination vaccine regimen compared to TVV with intranasal placebo.

Human CD4+ T-cell recognition of influenza A virus hemagglutinin after subunit vaccination

We have examined human CD4+ T-cell recognition of influenza A/Beijing/32/92 (H3N2) virus hemagglutinin following influenza virus HANA subunit vaccination. CD4+ T-cell repertoires were dominated by recognition of epitopes located in conserved regions of the molecule, in a major histocompatibility complex class II haplotype-dependent manner, analogous to that observed following natural infection.

The heterogeneity of the age-related decline in immune response: impairment in delayed-type hypersensitivity and cytotoxic T-lymphocyte activity occur independently

Aged mice are known to have a heterogeneous cytotoxic T-lymphocyte (CTL) response to an influenza challenge. We sought to determine whether delayed-type hypersensitivity (DTH) to sheep red blood cells (SRBC) was also heterogeneous in aging and, if so, whether this correlated with anti-influenza CTL activity. Aged mice developed mean footpad swelling of 0.24 +/- 0.09 mm following SRBC challenge and mean CTL activity of 35 +/- 18%. Even though these values were significantly lower than those from young mice (0.54 +/- 0.10 mm and 51 +/- 2%, respectively), no correlation was found between anti-influenza CTL activity and DTH to SRBC (r = 0.01). We believe the most likely reason for this independent decline in immune response is because different activation signals are required for DTH and CTL activity. Our data thus suggest an age-related functional mosaicism in the immune system.

Activity of CD4+ T-cell clones of type 1 and type 2 in generation of influenza virus-specific cytotoxic responses in vitro

The activity of distinct CD4+ T-helper cell (Th) clones in promoting secondary A/PR/8/34/Mt.S.(H1N1) (A/PR8) influenza virus-specific, class I-restricted cytotoxic T-lymphocyte (CTL) responses in vitro was examined. CD8+ T cells which had been purified by fluorescence-activated cell sorter from spleen cells of A/PR8-primed mice were used as responders. On their own, purified CD8+ T cells were unable to generate cytotoxic activity upon in vitro culture with A/PR8-infected stimulator cells. Significant cytotoxic activity was generated in cultures that were additionally supplemented with A/PR8-specific Th clones or cell-free supernatant from these clones. Although there were large differences among individual Th clones in this function, Th clones of type 1 (Th1) promoted, on average, significantly stronger cytotoxic responses than Th clones of type 2 (Th2). The differences in promotion of a cytotoxic response correlated with the amount of interleukin-2 (IL-2) or IL-4 secreted by individual Th clones. These two lymphokines accounted for the CTL-promoting activity of the respective Th clones, since addition of recombinant IL-2 (IL-2) or rIL-4 to Th-free cultures substituted fully for the respective Th clones. As observed with Th clones, rIL-2 was significantly more effective than rIL-4 in promoting a cytotoxic response. When used in combination, Th2 clones had an antagonistic effect on the generation of a CTL response by Th1 clones. This effect could be partially transferred with cell-free supernatant from activated Th2 clones and could be reversed by addition of excess rIL-2. Both consumption of IL-2 by Th2 and secretion of an inhibitory factor(s) appear to be involved in this phenomenon.

Bovine recombinant interleukin-2 augments immunity and resistance to bovine herpesvirus infection

The in vivo administration of bovine recombinant interleukin-2 (rIL-2) was evaluated in calves vaccinated and then challenged with bovine herpesvirus-1 (BHV-1). In Experiment 1, 24 calves were allotted to four groups: control; bovine rIL-2; BHV-1 vaccine (modified-live); and bovine rIL-2 + BHV-1 vaccine. Serum neutralizing antibody titers to BHV-1 were increased sixfold, and virus shedding was fourfold less in calves vaccinated and treated with rIL-2 (25 micrograms/kg, intramuscularly) when compared to calves that received vaccine only. Treatment with rIL-2 induced lymphokine-activated killer activity that was eliminated by pretreating effector cells with complement and a monoclonal antibody (B26A) specific for the sheep red blood cell receptor. The rIL-2 treatment in BHV-1-vaccinated calves increased the calves' ability to withstand a BHV-1 challenge. However, during treatment with rIL-2, calves developed diarrhea and mild fever that abated after IL-2 treatment was stopped. A second experiment was then conducted to determine a dose of rIL-2 that would enhance immunity to BHV-1 without causing adverse side effects. Twenty-five calves were allotted to five groups that received injections of rIL-2 at 0.0, 25.0, 2.5, 0.25, or 0.025 micrograms kg-1 day-1 for 5 days. All calves received a modified-live BHV-1 vaccine. Calves treated with 25.0 micrograms kg-1 day-1 showed similar adverse side effects as in the first experiment but all other calves were normal. Compared to control calves, those treated with 25.0, 2.5, and 0.25 micrograms kg-1 day-1 of rIL-2 had higher (P less than 0.05) serum antibody titers to BHV-1 and following challenge lower (P less than 0.05) BHV-1 titers in nasal secretions; additionally, clinical disease as evidenced by nasal and ocular discharge was less severe (P less than 0.05). In vitro cytotoxic responses against BHV-1-infected bovine kidney cells were increased (P less than 0.05) in calves treated with rIL-2 in a dose dependent manner. These data suggest that bovine rIL-2 at 2.5 to 0.25 micrograms/kg may be an effective adjuvant to immunization.

Role of different lymphocyte subsets in human anti-viral T cell cultures

We have systematically studied uncloned human cell lines derived from anti-influenza A virus or anti-Epstein-Barr virus (EBV) bulk cultures, or from cultures highly enriched for CD4+ or CD8+ lymphocytes. The most noteworthy results are the following: (1) Anti-viral bulk cultures consisted of more than 90% of CD8+ cells in all cases. In contrast, anti-HLA cell lines are composed of approximately 50% CD8+ and 50% CD4+ cells. All of the CD8+ and CD4+ cells present in the culture were also 4B4+/2H4-. (2) In anti-viral bulk cultures, the cytolytic activity was restricted by HLA class I molecules and almost exclusively through a single HLA class I molecule. (3) Positively or negatively selected CD8+ lines showed the same restriction pattern. They grew less efficiently than bulk cultures but could be maintained in the absence of CD4+ cells. The CD4+ cells were however necessary at the beginning of the culture for the development of cytolytic anti-influenza virus CD8+ cells, whereas they were not required for the development of cytolytic anti-EBV CD8+ cells. (4) The CD4+ cell lines grew more actively than bulk cultures. A cytolytic activity for virus-infected cells was constantly detected in these culture from the third passage onward and it was always restricted by HLA class II molecules. This activity was maintained throughout the culture period. However, class II-restricted cytolytic cells were not detected during primary or secondary responses in vitro.

Recognition of influenza virus-infected B-cell lines by human influenza virus-specific CTL

The cytotoxic activity on influenza virus-infected Epstein-Barr virus (EBV)-transformed B-lymphoblastoid cell lines (LCL-Flu) and influenza virus-infected phytohemagglutinin lymphoblasts (PHA-Flu) was compared with the use of influenza-A virus-specific cytotoxic T lymphocytes (CTL), generated in short-term bulk cultures. Cold-target inhibition experiments showed that the lysis of PHA-Flu was completely blocked by both cold LCL-Flu and cold PHA-Flu whereas the lysis of LCL-Flu was completely inhibited by cold LCL-Flu, but only partially by cold PHA-Flu, indicating that structures can be recognized on LCL-Flu which are absent from PHA-Flu. Monoclonal antibody (McAb) directed against a monomorphic determinant of major histocompatibility complex (MHC) class I molecules inhibited the lysis of PHA-Flu more strongly than the lysis of LCL-Flu. Since LCL have a high expression of MHC class II molecules compared to PHA lymphoblasts, we examined whether class II-restricted CTL activity was responsible for the (anti)class I McAb-resistant lysis of LCL-Flu. Neither anti-CD4 McAb nor anti-class II McAb inhibited the lysis of LCL-Flu which argues against a contribution of MHC class II-restricted CTL. Depletion of CD16+ cells, containing the majority of the nonspecific cytotoxic cells, did not affect the lysis of LCL-Flu, indicating that the remaining lysis on LCL-Flu was also not due to a nonspecific component. We suggest that cell-type-dependent variations exist in the nature of the immunogenic determinants to which CTL respond.