Participation of lymphocytes in viral infections

Therapeutic approaches to disease modifying therapy for multiple sclerosis in adults: an Australian and New Zealand perspective: part 3 treatment practicalities and recommendations. MS Neurology Group of the Australian and New Zealand Association of Neurologists

In this third and final part of our review of multiple sclerosis (MS) treatment we look at the practical day-to-day management issues that are likely to influence individual treatment decisions. Whilst efficacy is clearly of considerable importance, tolerability and the potential for adverse effects often play a significant role in informing individual patient decisions. Here we review the issues surrounding switching between therapies, and the evidence to assist guiding the choice of therapy to change to and when to change. We review the current level of evidence with regards to the management of women in their child-bearing years with regards to recommendations about treatment during pregnancy and whilst breast feeding. We provide a summary of recommended pre- and post-treatment monitoring for the available therapies and review the evidence with regards to the value of testing for antibodies which are known to be neutralising for some therapies. We review the occurrence of adverse events, both the more common and troublesome effects and those that are less common but have potentially much more serious outcomes. Ways of mitigating these risks and managing the more troublesome adverse effects are also reviewed. Finally, we make specific recommendations with regards to the treatment of MS. It is an exciting time in the world of MS neurology and the prospects for further advances in coming years are high.

Reduced efficacy of hemorrhagic enteritis virus vaccine in turkeys exposed to avian pneumovirus

Avian pneumovirus (APV) is an immunosuppressive respiratory pathogen of turkeys. We examined the effect of APV infection on the vaccine efficacy of hemorrhagic enteritis virus (HEV) vaccines. APV was inoculated in 2-wk-old turkeys. Two or four days later, an attenuated HEV vaccine (HEVp30) or marble spleen disease virus (MSDV) vaccine were administered. Virulent HEV challenge was given 19 days after HEV vaccination. APV exposure compromised the ability of HEVp30 and MSDV to protect turkeys against virulent HEV. The protective index values were as follows: MSDV (100%) versus APV + MSDV (0%) (P < 0.05); HEVp30 (60%) versus APV + HEVp30 (30%) (P < 0.05) (Experiment I) and HEVp30 (56%) versus APV + HEVp30 (20%) (P < 0.05) (Experiment II). These data indicated that APV reduced the efficacy of HEV vaccines in turkeys.

Reactive oxygen species and nitric oxide in viral diseases

Metabolites derived from superoxide (O2.-) and nitric oxide (NO.) play an important role in antimicrobial and antitumoral defense, but may also harm the host. Low levels of such metabolites can also facilitate viral replication because of their mitogenic effects on cells. Most viruses grow better in proliferating cells, and indeed, many viruses induce in their host cell changes similar to those seen early after treatment with mitogenic lectins. Influenza and paramyxo-viruses activate in phagocytes in the generation of superoxide by a mechanism involving the interaction between the viral surface glycoproteins and the phagocyte's plasma membrane. Interestingly, viruses that activate this host defense mechanism are toxic when injected in the bloodstream of animals. Mice infected with influenza virus undergo oxidative stress. In addition, a wide array of cytokines are formed in the lung, contributing to the systemic effects of influenza. Oxidative stress is seen also in chronic viral infections, such as AIDS and viral hepatitis. Oxidant production in viral hepatitis may contribute to the emergence of hepatocellular carcinoma, a tumor seen in patients after years of chronic inflammation of the liver. Antioxidants and agents that downregulate proinflammatory cytokines and lipid mediators may be a useful complement to specific antiviral drugs in the therapy of viral diseases.

Preferential cytotoxic effect of Newcastle disease virus on lymphoma cells

Susceptibility of lymphoma cells (Daudi, HD-Mar) to Newcastle disease virus toxicity was found to be higher than that of lymphoblastoid cells (Milstein) and of resting peripheral blood lymphocyte (PBL). Phytohemagglutinin- and/or pokeweed-mitogen-activated PBL however, exhibited, elevated sensitivity, similar to that of lymphoma cells. The level of cytotoxicity was monitored by cell viability, inhibition of DNA synthesis and release of 51Cr. When Daudi cells were mixed with PBL they were significantly more sensitive to the killing effect of the virus (70% mortality compared to 30% 30 h after infection, P < 0.05). The degree of sensitivity to viral cytotoxicity was unrelated to the efficacy of adsorption, which was similar for all cell lines as shown by immunofluorescent staining and flow cytometry. Also an influenza strain A/PR/8/34 (H1N1) adsorbed but did not affect the viability of any of the cells tested. Our results demonstrate that New-castle disease virus caused preferential damage to lymphoma cells as compared to non-cancerous normal cells.

Direct interactions of coxsackievirus B3 with immune cells in the splenic compartment of mice susceptible or resistant to myocarditis

In vitro replication of coxsackievirus B3 (CVB3) in cells of the immune system derived from uninfected adolescent A/J and C57BL/6J mice and replication of CVB3 in and association with immune cells from spleens of infected animals in vivo were assessed. Nonstimulated or mitogen-stimulated spleen cells were minimally permissive for viral replication during an 8-h period. Three days postinfection (p.i.), CVB3 RNA was localized in vivo to B cells and follicular dendritic cells of germinal centers in both A/J and C57BL/6J mice; however, extrafollicular localization was greater in C57BL/6J mice (P = 0.0054). Although the pattern of CVB3 RNA localization was different, the total load of infections virus (PFU per milligram of tissue) was not different. Splenic CVB3 titers (PFU per milligram of tissue) in both strains were maximal at day 3 or 4 p.i. and were back to baseline by day 7 p.i., with most infectious virus being non-cell associated. CVB3 titers (PFU per milligram of tissue) correlated directly with in situ hybridization positivity in splenic follicles and extrafollicular regions in both murine strains; however, follicular hybridization intensity was greater in A/J mice at day 5 p.i. (P = 0.021). Flow cytometric analysis demonstrated that 50.4% of total spleen cells positive for CVB3 antigen were B cells and 69.6% of positive splenic lymphocytes were B cells. Myocardial virus load in C57BL/6J mice was significantly lower than that in A/J mice at days 4 and 5 p.i. These data indicate that CVB3 replicates in murine splenocytes in vitro and in B cells and extrafollicular cells in vivo.

Pathogenesis of type II avian adenovirus infection in turkeys: in vivo immune cell tropism and tissue distribution of the virus

Hemorrhagic enteritis virus (HEV), a type II avian adenovirus, causes intestinal hemorrhages and immunosuppression in turkeys. In this study, we exposed turkeys to virulent HEV and examined fractionated spleen cells for the presence of viral DNA by in situ hybridization and amplification of DNA extracted from virus-infected cells by PCR. HEV replication was detected only in the immunoglobulin M-bearing B lymphocytes and macrophage-like cells but not in the CD4+ or CD8+ T lymphocytes. The inability to infect T cells distinguishes type II avian adenoviruses from lymphotropic mammalian adenoviruses which infect and replicate in T cells. Furthermore, these data suggested that HEV-induced immunosuppression in turkeys may be due to the effect of the virus on B lymphocytes and macrophages. We also examined tissue tropism of HEV by in situ hybridization conducted on sections of lymphoid and nonlymphoid tissues. Large numbers of HEV-positive cells were detected in spleen and cecal tonsils. Diminutive viral activity was present in the intestines, the principal site of HEV-induced pathology. Thus, intestinal pathology was not associated with local cytopathic viral replication. This result and our previous observation that cyclosporin A abrogated intestinal hemorrhaging in HEV-infected turkeys strongly suggested that intestinal lesion induced by this virus may be immune system mediated.

T cells causing immunological disease

Evidence is summarized that genetically encoded self peptides may not be considered immunological as self when expressed solely extrathymically on non-lymphohemopoietic cells; nevertheless, they are antigenic and are recognized by induced effector T cells. An immune response is readily induced against such "nonimmunological" self (as against foreign) by an appropriate presentation of these self peptides on proper antigen-presenting cells. If it is substantial, such an immune response causes a disease resembling an autoimmune disease, which is more appropriately called an "immunopathological T cell-mediated disease" rather than a T cell autoimmunity. These pathogenetic considerations may be incorporated into a revised-extended Gell and Coomb's classification of immunopathologies. If this view of immunopathological T cell-mediated diseases against nonimmunological self is correct, such diseases should be amenable to the same prevention (i.e., vaccination) and treatment principles, as are T cell immune responses to foreign antigens.

Virally induced immunosuppression

A mouse model of virus-triggered, T-cell mediated acquired immunosuppression is analyzed. Lymphocytic choriomeningitis virus initially infects mostly macrophages and antigen-presenting cells; these are destroyed by lymphocytic choriomeningitis virus specific cytotoxic T cells resulting in immunosuppression. Similar immunopathological mechanisms may play a role in acquired immune deficiency syndrome.

Suppression of virus-specific antibody production by CD8+ class I-restricted antiviral cytotoxic T cells in vivo

The question of whether virus-induced immunosuppression includes the antibody response against the infecting virus itself was evaluated in a model situation. Transgenic mice expressing the T-cell receptor (TCR) specific for peptide 32-42 of lymphocytic choriomeningitis virus (LCMV) glycoprotein 1 presented by Db reacted with a strong transgenic cytotoxic T-lymphocyte (CTL) response starting on day 3 after infection with a high dose (10(6) PFU intravenously [i.v.]) of the WE strain of LCMV (LCMV-WE); LCMV-specific antibody production in the spleen was suppressed in these mice. Low-dose (10(2) PFU i.v.) infection resulted in an antiviral antibody response comparable to that of the transgene-negative littermates. The induction of suppression of LCMV-specific antibody responses was specifically mediated by CD8+ TCR transgenic CTLs, since the LCMV-8.7 variant virus (which is not recognized by transgenic TCR-expressing CTLs because of a point mutation) did not induce suppression. In addition, treatment with CD8 monoclonal antibody in vivo abrogated suppression. Once suppression had been established, it was found to be nonspecific. The abrogation of antibody responses depended on the relative kinetics of the antibody response involved and the kinetics of the anti-LCMV CTL response. Analysis of T- and B-cell subpopulations showed no significant changes, but immunohistochemical analysis of spleens revealed extensive destruction of follicular organization in lymphoid tissue by day 4 in transgenic mice infected with LCMV-WE but not in those infected with the CTL escape mutant LCMV-8.7. Impairment of antigen presentation rather than of T or B cells was also suggested by adoptive transfer experiments, showing that transferred infected macrophages may improve the anti-LCMV antibody response in LCMV-immunosuppressed transgenic recipients; also, T and B cells from suppressed transgenic mice did respond in irradiated and virus-infected nontransgenic mice with antibody formation to LCMV. Such virus-triggered, T-cell-mediated immunopathology causing the suppression of B cells and of protective antibody responses, including those against the infecting virus itself, may permit certain viruses to establish persistent infections.

Immunosuppression in mice by lymphocytic choriomeningitis virus infection: time dependence during primary and absence of effects on secondary antibody responses

The kinetic study of immunosuppression caused by infection of mice with lymphocytic choriomeningitis virus WE (LCMV-WE) was assessed in DBA/2 (H-2d) and C57BL/6 (H-2b) mice. Infection with LCMV caused suppression of the Day 4 IgM response (complete in DBA/2 and incomplete in C57BL/6) and completely suppressed IgG responses on Days 9 and 42 to vesicular stomatitis virus (VSV) injected 2-11 days after LCMV. Suppression was partial when VSV was injected 16-28 days after LCMV-WE infection. The observed suppression between Day 2 and Day 11 was complete and nonspecific as revealed by the fact that these mice could not mount a secondary response to VSV when reinjected with the same VSV 42 days later. Nonspecificity of suppression was further indicated by the finding that the kinetics of recovery from suppression of the anti-VSV response were comparable for the VSV serotype used during the 2- to 11-day period after LCMV infection as for the serologically noncross-reactive second VSV serotype; both anti-VSV responses had recovered by Days 56-82 after LCMV infection. Once an anti-VSV antibody response was established, a subsequent LCMV-WE infection had no suppressive effect on Day 2 or Day 42 after a primary VSV infection. Also, the capacity of VSV-primed mice that were LCMV infected to respond to VSV in a secondary challenge infection with the same VSV was not impaired.

Virus-lymphocyte interactions: inductive signals necessary to render B lymphocytes susceptible to vesicular stomatitis virus infection

We examined the inductive signals necessary to render B lymphocytes capable of supporting a productive vesicular stomatitis virus infection. Small murine splenic B cells in the G0 phase of the cell cycle were cultured with stimulators which allow progression through various stages in the activation and/or differentiation pathway leading to antibody secretion. We found that vesicular stomatitis virus expression is dependent on the state of B-cell activation and that three distinct phases can be defined. A nonsupportive state, which is defined by the failure to produce infection centers, viral proteins, or PFUs, is characteristic of freshly isolated small B cells, B cells cultured 48 h without further stimulation, or B cells in the G1 phase of the cell cycle induced by culture with T-cell-derived lymphokines. This refractory state was not due to a failure of virus uptake. Activation of G0 B cells with anti-immunoglobulin at doses which allow entry into the S phase rendered them capable of synthesizing viral proteins and increased the number of B cells producing infection centers, without enhancing PFU production on a per cell basis. In contrast, B cells stimulated with multiple inductive signals provided by anti-immunoglobulin and lymphokines showed increased infectious particle production (7 PFU per infection center). Lipopolysaccharide stimulation, acting through another induction pathway, caused the maximum increase in the number of infected B cells and production of infectious particles (25 PFU per infection center).

Enhanced tumor susceptibility of immunocompetent mice infected with lymphocytic choriomeningitis virus

Mice infected i.v. with high doses of lymphocytic choriomeningitis virus (LCMV; 10(5)-10(6) plaque-forming units) 8-10 days prior to challenge with the methylcholanthrene-induced fibrosarcoma tumor cell line MC57G or the melanoma cell line B16 tumor cells showed an enhanced tumor susceptibility with respect to both growth kinetics of the tumor and the minimal dose necessary for tumor take. After transient initial growth, MC57G tumor cells were all rejected by uninfected C57BL/6 mice by day 14. Mice preinfected i.v. with LCMV 3 weeks before or at the time of tumor challenge, but not those infected 2 months before or 7 days after, showed increasing tumor growth, the tumor take being 100% for 10(6), 50% for 10(5) and 37% for 10(4) MC57G tumor cells injected into the footpad compared with resistance to 10(6) cells in normal mice. B16 melanoma cells also grew more rapidly in LCMV-preinfected mice and by day 40 tumors were established with about 100 times fewer cells, i.e. about 10(3) compared with 3 x 10(4)-3 x 10(5) for uninfected mice. Analysis of the growth of tumor cells in normal and in LCMV-carrier mice revealed that the latter mice were not more susceptible to LCMV-infected than to uninfected MC57G. Since LCMV-carrier mice fail to mount LCMV-specific T cell responses, these results suggest that anti-LCMV-specific T cells may be responsible for acquired immunodeficiency hampering immune surveillance against the tumors studied.

Enhanced virus replication and inhibition of lymphocytic choriomeningitis virus disease in anti-gamma interferon-treated mice

The role of gamma interferon (IFN-gamma) induced during a viral infection in the ability of the host to acquire antiviral immunity was studied in mice. They were injected subcutaneously daily with an ammonium sulfate-precipitated sheep anti-IFN-gamma antibody preparation able to neutralize 10(4) U of IFN-gamma. Specificity of the anti-IFN-gamma antiserum was demonstrated by absence of detectable activity against natural IFN-alpha and -beta. Controls were treated with a similarly prepared normal sheep serum. Treatment with the IFN-gamma-specific antibody preparation had no influence on the ability of mice to generate anti-vaccinia virus- or anti-vesicular stomatitis virus (VSV)-specific cytotoxic T-cell (CTL) responses or T helper-dependent immunoglobulin G responses to VSV. In contrast, treatment of mice with sheep anti-IFN-gamma impaired CTL responses against lymphocytic choriomeningitis (LCM) virus (LCMV, Aggressive isolate); in addition, under the experimental conditions used, it prevented lethal LCM. Cytotoxic T-cell activity measured in the spleens of anti-IFN-gamma-treated mice was comparable to that found in mice initially infected with a 100-fold-larger dose of LCMV. Evaluation of the effects of treatment on the kinetics of virus replication revealed that in both euthymic and athymic nude C57BL/6 mice, anti-IFN-gamma treatment led to an increase of virus titers up to 100-fold compared with control mice. Therefore, IFN-gamma may play a role in controlling viruses with tropism for lymphocytes and monocytes/macrophages, such as LCMV.

Virus-triggered immune suppression in mice caused by virus-specific cytotoxic T cells

Normal mice infected with 10(5) infectious doses of lymphocytic choriomeningitis virus (LCMV, WE isolate) generated a reduced or no T cell-independent IgM and/or T cell-dependent IgG response to a subsequent vesicular stomatitis virus Indiana (VSV-IND) injection; this transient immune suppression lasted for weeks to months. Connatally infected LCMV-carrier mice or acutely infected T cell-deficient nude mice had normal anti-VSV IgM and IgG or IgM responses respectively. LCMV-infected nude mice transfused with helper cell-depleted LCMV-specific immune spleen cells were immunosuppressed. Normal mice infected with LCMV but treated with a rat anti-CD8 mAb (that had been shown previously to eliminate cytotoxic T cells in vivo) and then infected with VSV exhibited a normal anti-VSV IgM and IgG response. Since no IFN-alpha or -beta was detected on, or after, day 6 of LCMV infection, neither LCMV alone, nor IFN induced by it caused the observed immune suppression; the presented evidence suggests that LCMV-immune CD8+ T cells were responsible for it. It is conceivable that a similar pathogenesis where virus-specific cytotoxic T cells may destroy virus-infected cells essentially involved in an immune response (APC, T helper cells, etc.) may be involved in other virally triggered immune suppression or in AIDS.

An acquired immune suppression in mice caused by infection with lymphocytic choriomeningitis virus

A murine model of virally induced acquired immunodeficiency was analyzed in mice. The effect of systemic infection with various isolates of lymphocytic choriomeningitis virus (LCMV) on the capacity of mice to mount a T cell-independent IgM and a T cell-dependent IgG neutralizing antibody response against a subsequent infection with vesicular stomatitis virus (VSV) was analyzed. DBA/2 mice infected with the LCMV-WE isolate were impaired in their IgM and IgG responses to VSV. Immune suppression was not caused by interferons inhibiting proper VSV antigen expression, since responses to inactivated VSV were also suppressed. The higher the dose of the LCMV and the lower the dose of the challenging VSV infection the more drastic was the apparent lack of immune responsiveness and the longer it lasted. Kinetics of induction of suppression of the T cell-independent IgM responses closely followed that of a normal cytotoxic T cell response to LCMV-WE, starting on day 6 and reaching maximal levels by day 8 to 10. The T cell-dependent IgG response to VSV was suppressed with a kinetics that was shifted by about 6 days when compared with suppression of IgM responses, i.e. LCMV infection on the same day or before (but not after) VSV infection led to suppression of IgG responses that are usually first detected by day 6-7 after initiation of the VSV infection. Severity and duration of immunosuppressiveness depended upon the LCMV isolate and the mouse strain used: LCMV-WE and LCMV-Docile were most, whereas LCMV-Armstrong was in general least immunosuppressive. Antibody responses to VSV-NJ seemed to be more subject to LCMV-induced immune suppression than VSV-IND-specific responses. Mouse strains differed considerably with respect to extent of suppression, dependent upon both major histocompatibility genes (MHC) and non-MHC genes. DBA and Swiss type mice were generally more susceptible than C57BL and CBA mice, and H-2q and H-2k seemed to be more susceptible than H-2b or H-2d mice. Mice infected with LCMV-WE showed signs of acquired immunodeficiency diseases since they were more susceptible to superinfection with VSV and developed paralytic disease and tended to die from VSV infection. Since LCMV is basically a noncytopathic virus, this murine model of virally induced immune suppression may serve to analyze immune pathogenesis of virus-induced acquired immunodeficiency.

The decreased antibacterial activity of oral polymorphonuclear leukocytes coincides with the occurrence of virus-carrying oral lymphocytes and epithelial cells

Patients suffering from periodontitis or periodontosis were selected for the study. Further subdivision of these groups was based on the presence or absence of herpes and/or adenoviruses in their oral lymphocytes and epithelial cells. The phagocytic and bactericidal activities of oral leukocytes isolated from the same individuals were compared with virus carriage. In the periodontitis group, 60.5%, and in the periodontosis group 61.5% of patients carried viruses, while this was established only in 21.1% of control cases. On the other hand, emigration and sulcular gathering of the less viable polymorphonuclear leukocytes was elevated but their phagocytotic activity was decreased among periodontitis patients. Bactericidal capacity was significantly lowered among those subjects who carried viruses in their cells, as compared with virus-free persons, especially in the periodontitis group. The functions of the polymorphonuclear leukocytes accumulated in the sulcus gingivalis may be modified by mediators released from the virus-carrying cells. These mediators could achieve a greater concentration locally, and the damaged leukocytes would not be able to eliminate the microbes continuously so that the accumulation of bacterial products, among them endotoxins, could lead to periodontal inflammation.

Human T-lymphoblastoid cell lines with high and low abilities to produce interferon-gamma constitutively and their susceptibilities to interferon

A human T-lymphoblastoid cell line, TCL-Fuj, produces large amounts of interferon (IFN)-gamma constitutively. A variant cell line, 2M, was derived from it. Both cell lines express similar surface antigen markers, but differ in surface morphology. Compared with the parent TCL-Fuj cell line, 2M produced less IFN-gamma constitutively but more in response to IFN inducers. The IFNs produced constitutively and on stimulation with inducers were analyzed by SDS-polyacrylamide gel electrophoresis. In TCL-Fuj cells, the constitutive and induced IFNs consisted of the same molecular species (22K and 39K). In 2M cells, smaller IFNs were produced constitutively (18K and 32K) and induction resulted in a marked increase of 22K molecules. These two cell lines also differed in sensitivity to the antiviral activity of IFN. Other T-lymphoblastoid cell lines, HPB-ALL and TCL-Fuj 4 cells, which did not produce IFN-gamma were permissive for vesicular stomatitis virus (VSV) replication; its growth was markedly suppressed by IFN-gamma and -alpha. TCL-Fuj cells were also permissive for VSV, but were not susceptible to the antiviral effect of the IFNs. In contrast, in 2M cells the multiplication of VSV was restricted; the viral yield was further reduced by the IFNs and increased by treatment with anti-human IFN-gamma serum. Several clonal cell lines derived from TCL-Fuj and 2M cells had characteristics similar to the respective parent cell lines. The growth of both cell lines was not affected by IFN-gamma or by -alpha. The separation of antiviral and anti-proliferative susceptibilities was peculiar to 2M cells unlike other cell lines.

Growth of malignant rabbit fibroma virus in lymphoid cells

To understand better the immunosuppressive capacity of malignant rabbit fibroma virus (MV), we characterized MV growth in lymphoid cells. Replication of MV occurs in unstimulated normal spleen cells in vitro and is enhanced by adding T- or B-lymphocyte mitogens. In splenic T-lymphocyte preparations, comparable results are found: virus growth in the absence of mitogen, augmented by adding Con A. Unlike mature T cells, thymic lymphocytes support MV replication only when mitogen is added. When spleen cells from rabbits infected with MV in vivo are removed and cultured without mitogen, MV growth is again observed, with virus titer increasing about 10-fold per day of culture. In spleen cell populations from MV tumor-bearing rabbits, MV grows best in T lymphocytes, moderately in B lymphocytes, and least efficiently in adherent cells. When spleen cells are examined immediately following sacrifice, MV antigens are expressed solely on T lymphocytes from rabbits infected in vivo with MV 7 days previously. However, following overnight incubation in vitro a population of non-T lymphocytes displays cell membrane virus antigens. MV adapts itself somewhat to growth in lymphocytes, showing significantly greater growth in lymphocytes following passage in lymphocytes than is observed for non-lymphocyte-propagated virus. MV-infected lymphocytes also elaborate a factor that enhances MV growth in lymphocytes. Thus, MV replicates preferentially in mature T lymphocytes but will grow well in B cells as well. In vivo infection produces relatively small amounts of recoverable virus. However, when these lymphocytes are cultured in vitro virus replicates very well without added mitogens. These growth patterns may help to understand MV-induced immunologic dysfunction.

Poliovirus infection of established human blood cell lines: relationship between the differentiation stage and susceptibility of cell killing

The replication of type 1 poliovirus in 13 established human blood cell lines differing in the differentiation stage and cell lineage was investigated. Three T (CCRF-CEM, CCRF-HSB-2, and Molt-3) and three B (Raji, CCRF-SB, and RPMI 8226) cell lines showed no cytopathic effects (CPE) or virus production. CPE associated with virus production were detected in the other seven cell lines: HL-60, ML-1, and KG-1 (granulocytic lineage), U-937 and THP-1 (monocytic lineage), K-562 (erythroid lineage), and Molt-4 (T cell lineage). These susceptible cell lines greatly differed in the speed at which the CPE progressed. The progression of CPE was faster in relatively well-differentiated cell lines such as HL-60 and U-937, independently of the multiplicity of infection, than in less differentiated cell lines such as K-562, KG-1, and THP-1. Thus, for the same lineage, the speed at which CPE progressed became proportionally higher with subsequent differentiation stages. In the K-562 cell culture, CPE were not observed until at least 5 days postinfection (p.i.), while more than 80% of HL-60 cells were killed within 3 days p.i. There were no significant differences between infected HL-60 and K-562 cells in the efficiency of infection determined at 8 hr p.i. by the indirect immunofluorescent technique, the rate of virus growth, or the amount of viral capsid protein synthesized. This indicated that there were similar viral replication cycles in the two cell lines. These observations suggest that the killing function of the virus is expressed more slowly in K-562 cells than in HL-60 cells.

Viruses disrupt functions of human lymphocytes. Effects of measles virus and influenza virus on lymphocyte-mediated killing and antibody production

We present experimental data that offer, in part, a better understanding of the immunosuppression that accompanies measles virus infection. We note that measles virus "silently" infects human lymphocytes and that the infection does not alter lymphocyte survival in vitro. Yet such infected lymphocytes fail to generate natural killer (NK) cell activity or synthesize immunoglobulins (Ig). Thus, the presence of virus within lymphocytes impairs their specific immune functions in the absence of cytolysis. Influenza virus also infects human lymphocytes. In contrast to measles virus infection of resting lymphocytes in which viral antigen is rarely expressed, influenza virus infection of these cells yields viral antigens expressed in the cytoplasm and on the cell surface. Influenza virus-infected lymphocytes have normal NK cell activity but fail to synthesize IgG or IgM.

Mechanisms of enhanced resistance of Mycobacterium bovis BCG-treated mice to ectromelia virus infection

The mechanism of enhanced resistance of Mycobacterium bovis BCG-treated mice to ectromelia virus infection was investigated by determining the effect of splenectomy, antithymocyte serum, and antimacrophage serum on resistance. It was greatly reduced by these treatments, not only in normal mice, but also in mice treated with live or heat-inactivated BCG. Production of circulating interferon by ectromelia virus and Newcastle disease virus was augmented in BCG-treated mice and was markedly depressed by splenectomy and antithymocyte and antimacrophage serum treatments in both BCG-treated and normal mice. Carbon clearance activity was activated in BCG-treated mice, but splenectomy did not influence phagocytic activity. These results suggest that augmented interferon production in the spleens of BCG-treated mice plays a major role in enhanced resistance. Other possible mechanisms are discussed.

Levamisole exacerbates coxsackievirus B3-induced murine myocarditis

Levamisole administration to several strains of adolescent mice at the time of or up to 4 days post-inoculation (p.i.) with a myocarditic variant of coxsackievirus B3 (CVB3m) increased the number of myocarditic lesions above that found in CVB3m-inoculated mice. Virus replication in heart tissues in vivo was not affected by levamisole administration to the mice, nor was production of neutralizing antibody to CVB3m. Lymphocytes from nodes of virus-inoculated mice treated with levamisole at 2 days p.i. exhibited an increased reactivity to phytohemagglutinin on days 6 and 8 p.i., compared with respective responses by nodal T lymphocytes from CVB3m-inoculated mice. Levamisole treatment of CVB3m-inoculated mice also increased the reactivity of splenic and peripheral blood T lymphocytes to phytohemagglutinin on day 8 p.i., but not day 6 p.i., compared with the respective responses by lymphocytes from CVB3m-inoculated mice. The proportion of theta antigen-bearing lymphocytes in the total lymphocyte population in peripheral blood of CVB3m-inoculated mice was not altered by levamisole treatment. However, CVB3m-induced reduction in this subpopulation of lymphocytes in the nodes was restored to control levels by levamisole treatment. Reactivities of cytotoxic T lymphocytes from CVB3m-inoculated mice were increased against both normal and CVB3m-inoculated target cells after levamisole treatment of these mice. The results suggest that levamisole may contribute to CVB3m induction of myocarditis by several mechanisms, such as increasing the blastogenic activity of the phytohemagglutinin-responding subset of T lymphocytes, by possibly altering T-lymphocyte distribution in the body and by nonspecifically increasing reactivities of cytotoxic T lymphocytes.

Levamisole therapy: clinical and immunological evaluation in herpetic keratitis

Thirty patients with herpetic keratitis, recurrent in 17, were examined and submitted to an immunological evaluation for cell-mediated immunity (E rosette forming cells, absolute number of T lymphocytes, skin tests). A group of 15 patients was treated with Levamisole (2.5 mg/kg body weight, 3 days a week), while the control group received no Levamisole. The observation period varied from 6 to 24 months. The clinical follow-up showed a reduction in the severity and duration of herpetic attacks and in the frequency of relapses compared with the control group. The immunological findings indicated a normalization of E rosettes in all the patients (treated and controls).

Mitogenic activity of Sindbis virus and its isolated glycoproteins

Purified preparations of Sindbis virus, a member of the togavirus family, are mitogenic for lymphocytes from a number of different mouse strains. Cell separation techniques, as well as studies using lymphocytes from the congenitally athymic BALB/c nu/nu mouse, showed that Sindbis virus is a T-cell-independent B-cell mitogen. Additionally, the envelope glycoproteins of Sindbis virus, isolated by Triton X-100 extraction and butanol precipitation, stimulated lymphocytes to incorporate five times as much [3H]thymidine into their DNA as did the Sindbis virion. These results are similar to those previously reported for vesicular stomatitis virus and herpes simplex virus types I and II and for the purified glycoproteins of vesicular stomatitis virus and influenza virus.

Increased incidence of bovine papular stomatitis in neonatal calves

A high incidence of bovine papular stomatitis (BPS) occurred in neonatal calves following neonatal thymectomy and antilymphocyte globulin treatment, sham thymectomy, treatment with normal horse globulin and in untreated calves. The source of BPS virus was not identified but was suspected to be latent in the calves and activated by thymectomy although no experimental evidence directly supported this conclusion. The potential for activation of a latent BPS infection was indicated by an apparent relationship between the stress of surgery or foreign protein inoculation and the severity of lesions. Subsequent bovine viral diarrhea virus infection did not result in recrudescence.

Target cells for malignant catarrhal fever virus in rabbits

Lymphocytes from lymph nodes and spleens of malignant catarrhal fever virus (MCFV) infected rabbits were tested for MCFV infectivity in secondary calf thyroid cell monolayers. Most infectivity was demonstrated in the lymphocytes. Some infectivity was also detected in macrophages/monocytes. It was thus concluded that lymphocytes form the major target cell for the herpesvirus of malignant catarrhal fever in rabbits.

Immunological and virological investigations in Down's syndrome

Lymphocyte responsiveness to phytohaemagglutinin and viral antigens was studied in children with Down's syndrome and in controls. Mitogen-responsiveness in the patients was significantly reduced as compared to the control values. Using the lymphocyte transformation test, trisomic patients showed more than a twofold increase in sensitivity to herpes simplex virus as compared to controls. The same test did not show any essential difference between the two groups when adeno- and influenza viruses were used. Immunofluorescence technique, with specifically conjugated antiviral sera, permitted the detection of specific fluorescence in 30% of the patients with Down's syndrome indicating the presence of oncogenic adenovirus type 12 antigen in the circulating lymphocytes. No antibodies--or only very low titres--against adeno- and herpes simplex viruses were demonstrated in the sera of trisomic patients. Mononuclear leukocytes from these patients often showed structural alterations. The incidence of infectious herpes simplex virus and Candida albicans in the saliva of patients was higher than in the control group. It seems that Down's syndrome involves partial disturbance of both the cellular and humoral immune functions--at least with respect to certain viral antigens.

Mumps virus replication in human lymphoid cell lines and in peripheral blood lymphocytes: preference for T cells

The replication of mumps virus was studied in human continuous lymphoblastoid cell lines (LCLs) with T or B characteristics and in lymphocyte subpopulations derived from peripheral blood. T-LCLs supported effective virus replication as shown by high titers of free and cell-associated virus over 1 to 4 days after infection. By immunofluorescence analysis, the majority of cells were positive for mumps virus antigens. In contrast, the B-cell lines produced low titers of infectious virus, and only a small percentage expressed viral antigens. This resistance of the B-LCLs was found with several mumps virus strains. Cultures of peripheral blood mononuclear cells also supported mumps virus replication. Very high titers of infectious virus (10(8) PFU/ml) were observed in cultures prestimulated with phytohaemagglutinin. Studies with enriched T and B cells point to the activated T lymphocyte as the major virus-producing cell.

Replication of poliovirus and measles virus in cultures of human lymphoblastoid and of Burkitt lymphoma cell lines

Poliovirus type 1 replicated in 4 different human lymphoblastoid cell lines (LBL) transformed in vitro by EBV virus or isolated from cases of mononucleosis. Maximum virus titers were reached 2--4 days after inoculation. There was a decrease in percentage of viable cells in the infected cultures but a considerable fraction of cells was not destroyed by virus replication. A persistent low grade replication of virus was observed and demonstrable during 56 days after inoculation in one LBL cell line. Presumably a small fraction of cells supporting virus replication is continuously recruited from refractory cells. No virus propagation was demonstrable in 4 Burkitt lymphoma (BL) cell lines. Measles virus grew efficiently in both types of cell lines. Using indirect immunofluorescent technique poliovirus and measles virus antigen could be demonstrated in the cytoplasm of LBL cells in parallel with disappearance of F-actin containing microvilli.

Immediate loss of cell-mediated immunity to murine cytomegalovirus upon treatment with immunosuppressive agents

Splenic lymphocytes from cytomegalovirus-infected mice lost their in vitro proliferative responses to cytomegalovirus antigen within 3 h after in vivo treatment with antilymphocyte globulin and prednisolone. The response was inhibited when the agents were administered separately or together, and inhibition persisted through a 2-week course of immunosuppression. Circulating specific antibodies were depressed by multiple injections of antilymphocyte globulin alone or with prednisolone, but not by prednisolone alone. Mitogen-induced blast transformation was immediately depressed by immunosuppression with both agents. Although the response to lipopolysaccharide returned briefly, it declined with continuing treatment. Cytomegalovirus infection augmented the depressive effect of immunosuppression on the lipopolysaccharide proliferative response. Prednisolone treatment of infected animals did not affect the concanavalin A response, and lipopolysaccharide stimulation decreased more slowly and to a lesser extent than it did in mice treated with antilymphocyte globulin or both agents. Loss of specific cell-mediated immunity and simultaneous depression of humoral immunity indicated that immunosuppression immediately created an inability to respond to an active cytomegalovirus infection.

Comparison of in vitro lymphocyte proliferations induced by cytomegalovirus-infected human fibroblasts and cell-free cytomegalovirus

In vitro lymphocyte reactivity (LR) to cytomegalovirus (CMV)-infected human fetal fibroblasts (CMVFF) and cell-free CMV were measured by using lymphocytes from healthy donors. Lymphocytes from all seropositive donors were stimulated by CMVFF, whereas lymphocytes from negative donors were not. The optimal stimulator cell-to-lymphocyte ratio was in the range of 1:5 to 1:50, dependent on the virus dose used. LR to cell-free CMV was positive for 15 out of 18 seropositive donors and negative for 14 out of 16 seronegative donors. In most cases LR to CMVFF was considerably higher than LR to cell-free CMV. Within the CMV seropositive group there was no significant correlation between the LR to either CMVFF or cell-free CMV and the levels of antibodies to CMV early antigens or CMV late antigens. There was no strict correlation between LR to CMVFF and to cell-free CMV, especially not in tests with lymphocytes from two patients with CMV mononucleosis. Our data suggest that CMVFF and cell-free CMV are recognized (partly) by different subpopulations of CMV-specific memory lymphocytes. We conclude that the use of CMV-infected cells, in addition to cell-free CMV, in LR tests gives more reproducible and possibly also additional information about CMV-specific cellular immunity.

Activation of mouse lymphocytes by vesicular stomatitis virus

Vesicular stomatitis virus (VSV) is a mitogen for mouse spleen cells, and infectious virus is not required for mitogenesis. At concentrations between 10 and 100 microgram per culture, VSV stimulated DNA synthesis and blast transformation. Maximal activation by VSV occurred 48 h after culture initiation. Spleen cells depleted of T-lymphocytes by treatment with anti-Thy 1.2 and complement and those obtained from congenitally athymic BALB/c nu/nu mice were activated by VSV, suggesting that VSV is a B-cell mitogen. Activation of spleen cells was independent of the host in which the virus was grown, since VSV grown in BHK-21, HKCC, or MDBK cells was mitogenic. The mitogenesis was specific for VSV, since MDBK cell-grown WSN influenza virus was not a mitogen in this in vitro activation system, VSV-specific antibody prevented VSV mitogenesis, and VSV was mitogenic for spleen cells from C3H/HeJ mice which were resistant to mitogenesis by endotoxin.

Humoral and cellular immune responses of seronegative children vaccinated with a cold-adapted influenza A/HK/123/77 (H1N1) recombinant virus

Humoral and cell-mediated immune responses of young, seronegative children were assessed after intranasal vaccination with a cold-adapted influenza. A/HK/77 (H1N1) CR 35 recombinant virus. Vaccines shedding influenza virus experienced a rise in hemagglutinin-inhibition antibody 15 to 30 days after vaccination. Vaccinees showed low but significant lymphocyte transformation to A/USSR (H1N1) by day 8 after vaccination, which decreased to prevaccination levels at 30 to 34 days. The lymphocyte transformation response occurred before serum antibody rises were detected by hemagglutinin-inhibition assay. No change in lymphocyte responsiveness was observed after vaccination as measured by phytohemagglutinin stimulation. Lymphocytes responded to in vitro incubation with inactivated influenza (H1N1) virus by producing interferon. The interferon produced was of type I and was observed in vaccinees and nonvaccinees both before and after vaccination.

Suppression by progesterone of nonspecific in vitro lymphocyte stimulation in mice as a mechanism for the enhancement of herpes simplex virus type 2 vaginal infection

The role of antibody, interferon, and cell-mediated immunity (CMI) were studied to determine the mechanisms for progesterone enhancement of vaginal herpes simplex virus type 2 (HSV 2) infection in mice. Three groups of mice were studied: nonpregnant control, pregnant, and nonpregnant progesterone-treated mice. Vaginal infection with HSV 2 did not elicit a neutralizing antibody or a systemic interferon response in any of the groups tested. Splenic lymphocytes from noninfected and infected mice were stimulated in vitro with a nonspecific T-cell mitogen concanavalin (Con A) to measure the proliferative phase of CMI in these groups of mice. No suppression of (3H) thymidine (3HTdR) uptake was found in the pregnant or nonpregnant, progesterone-treated animals as compared to nonpregnant control mice. When progesterone was added directly to the splenic lymphocytes and continuously present during Con A stimulation a statistically significant depression of 3HTdR incorporation was found. We concluded that progesterone depresses Con A stimulation of murine lymphocytes, but progesterone must be continuously present to do so.

Activation of measles virus from silently infected human lymphocytes

Lymphocytes were incubated with measles virus for 4 days in the absence of a lymphocyte stimulating agent. Such nonstimulated lymphocytes, infected with measles virus, did not express the virus antigens that are detectable by cytotoxic antibodies. Approximately 1 out of 5,000, or even fewer, of such lymphocytes produced virus as demonstrated by the infectious center assay; in the supernate only 10--100 infectious viruses per milliliter were detected. No virus structures could be observed by means of an electron microscope. However, such lymphocytes showed no reaction to phytohemagglutinin (PHA) in terms of DNA synthesis in a subsequent culture in the presence of antibodies against measles to prevent spreading of the infection to other cells. Although stimulation by PHA did not result in a significant increase in [3H]thymidine incorporation, measles virus was activated; 32 h after the addition of PHA nearly 80% of the cells were killed by measles virus antibodies and complement. The number of virus-producing cells increased to approximately 1 in 300 or more, and at 72 h the virus titer in the supernate had risen to 10(6) infectious particles per ml. This reactivation of measles virus was still obtained when PHA was added as late as 8 or more days after the initial infection.

The treatment of herpetic reinfection with levamisole

The effect of levamisole on both clinical disease and virus recovery was studied in rabbits that were first infected with herpes simplex virus in one eye and then reinfected 14 days later by inoculation of the second eye. Reinfected rabbits treated with levamisole before reinfection developed significantly milder and smaller lesions than untreated controls. Virus recovery from the corneas was also less in the levamisole-treated animals than in the untreated controls.