B-cell activation in the mesenteric lymph nodes of resistant BALB/c mice infected with the murine nematode parasite Trichuris muris

Immune responses in resistant BALB/c mice infected with the murine nematode parasite Trichuris muris were examined. Following the establishment of infection, worm burdens of T. muris were expelled by BALB/c mice by day 21 postinfection (p.i.). Specific immunoglobulin G1 (IgG1) antibodies to T. muris excretory/secretory (E/S) antigens were detected in sera from infected mice, though specific IgG2a antibodies were not observed during infection. Ig-producing cells increased in the mesenteric lymph nodes (MLN) of infected mice on days 7, 14, and 21 p.i., with the greatest increase in numbers of IgG- and IgA-producing cells occurring on day 14. Marked increases in the relative percentages of B220+ and surface Ig+ (sIg+) cells were observed in the MLN of infected mice on days 14 and 21 p.i. Furthermore, cellular expansion of the MLN in infected mice resulted in an increase in the absolute numbers of B220+ and sIg+ cells. The levels of interleukin 2 (IL-2), IL-4, and interferon-gamma (IFN-gamma) detected in the supernatants from concanavalin A-stimulated MLN cells of infected mice were higher than those found in normal mice. Consequently, the expulsion of T. muris in resistant BALB/c mice was concomitant with cytokine production and B-cell activation in the MLN of infected mice. These results suggest the involvement of B-cell responses in protective immunity to T. muris infection.     

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Monoclonal antibodies (mAbs) against bovine leukocyte antigens specific for T cells (CD2, CD4, CD8 and gammadelta receptor) and B cells (surface IgM) were used in samples from one week and one-, three- and seven-month-old goats to study the evolution of lymphocyte subsets by flow cytometry in peripheral blood and the lymphoid organs: thymus, jejunal (JPP) and ileal (IPP) Peyer's patches, spleen and mesenteric lymph nodes. An increase in the values of alpha/beta receptor T cells with age was recorded whereas the gammadelta receptor T cells fell in number. In peripheral blood and in all tissues, except IPP the values for B cells (sIgM+) were low. The CD4+ and CD8+ cells predominated in JPP while B cells were the most important subpopulation in IPP. In the spleen, as in JPP, the CD4/CD8 ratio was less than one and the gammadelta T cells values were high. In mesenteric lymph nodes, CD8+ and B(sIgM) cells predominated in the youngest animals.     

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The effect of recombinant porcine interferon-gamma (IFN-gamma) on the immunogenicity in vivo of inactivated suid herpesvirus-1 (SHV-1, Phylaxia strain) was studied applying two successive i.m. immunizations. The animals were injected with inactivated virus alone or inactivated virus supplemented with 10(4) or 10(6) U IFN-gamma. After the first immunization, none of the animals responded with measurable virus-neutralizing antibody (VNAb), virus-specific IgG or IgA. Following a second immunization 4 weeks later, a significantly increased VNAb response was noted in animals that had received vaccine doses containing 10(4) U IFN-gamma (p < 0.05). These animals also had significantly augmented serum levels of IgG (p < 0.01) and IgA (p < 0.05). Inclusion of 10(6) U IFN-gamma in the vaccine preparation did not affect the antibody response. In one experiment, the pigs were challenged oronasally with 10(5) TCID50 of the 75V19 strain of SHV-1, 7 weeks after administration of the second vaccine dose. Those that had received 10(4) U IFN-gamma in the vaccination developed less fever during the postchallenge period (p < 0.004). In all challenged pigs, growth performance was compromised during the first week after challenge. However, the only animals retaining an average net increase in body mass were those covaccinated with 10(4) U IFN-gamma (p < 0.05). Nasal excretion of virus was not significantly different between groups that had been vaccinated with or without IFN-gamma. Multiple linear regression analysis of variables from individual vaccinated animals revealed the VNAb response to be correlated with serum IgG levels (p < 0.025) and with postchallenge growth performance (p < 0.0001) but not with serum IgA levels (p > 0.5). On the other hand, serum IgA appeared to be inversely correlated with early nasal virus excretion after challenge (p < 0.006). Taken together, our data suggest that addition of IFN-gamma to inactivated SHV-1 vaccine may be a useful tool for enhancement of both mucosal and systemic immune responses in pigs.     

Dietary calcium modulates Mycobacterium paratuberculosis infection in beige mice

A 6-month study was conducted to evaluate the effects of feeding different levels of dietary calcium (Ca) on the persistence of Mycobacterium paratuberculosis infection using a mouse model. Beige mice, averaging 8 weeks of age, were randomly assigned to one of the following dietary treatments: 1) 0.02% Ca, 2) 0.15% Ca, 3) 0.45% Ca, and 4) 1.0% Ca. Mice were infected intraperitoneally with 10(8) CFU viable M. paratuberculosis for 1, 3, and 6 month periods. Plasma Ca levels was unaffected by dietary Ca (x = 7.3 mg/dl). Plasma levels of 1,25(OH)2D3 was elevated significantly in 0.02% and 0.15% Ca groups compared to other treatments at the end of each period, with the highest levels observed for 0.02% Ca mice and intermediate values for 0.15% Ca mice. One month after infection, numbers of viable M. paratuberculosis cultured from the spleen were significantly reduced for 0.15% Ca mice, whereas the number of bacteria isolated from the liver and mesenteric lymph node (MLN) were higher for the 0.02% Ca group. There were no differences in bacterial numbers in the ileum although they tended to be higher for the 0.02% Ca group. Three months after infection, bacterial numbers in the spleen, ileum, and MLN did not differ across treatments, however, significantly lower numbers were found in the liver of 1.0% Ca mice. Reduced bacterial counts were also observed in the liver of 0.15%. 0.45%, and 1.0% Ca mice after a 6-month infection period compared to the 0.02% Ca group, with the lowest numbers isolated from the 1.0% Ca mice. Numbers of viable bacteria cultured from the ileum and MLN after 6 months of infection were also significantly reduced in 1.0% Ca mice. These results suggest that Ca metabolism is an important modulator of M. paratuberculosis infection.     

Mesenteric lymph node T cells but not splenic T cells maintain their proliferative response to concanavalin-A following peroral infection with Toxoplasma gondii

The suppression of T cell responsiveness which occurs after infection with Toxoplasma gondii in mice has been widely studied using spleen cells. Because the natural route of infection with T. gondii is the peroral route, we examined the proliferative responses of mesenteric lymph node (MLN) cells, in addition to spleen cells, to Concanavalin-A (Con-A) in mice perorally infected with T. gondii. Proliferative responses of spleen cells were significantly suppressed seven and ten days after infection when compared with spleen cells from uninfected mice (62% and 91% reduction, respectively). In contrast, proliferative responses of MLN cells from these infected mice did not differ from those of normal MLN cells. Since IFN-gamma-induced reactive nitrogen intermediate (RNI) production has been reported to play a major role in suppression of proliferative responses in spleen cells of infected mice, we compared production of IFN-gamma and RNI by spleen and MLN cells following infection. MLN cells produced as much IFN-gamma as did spleen cells, but produced 70% less nitrite (as a measure of RNI) after Con-A stimulation. Proliferative responses of MLN cells were suppressed when co-cultured with spleen cells from infected mice, and addition of an inhibitor of RNI to these co-culture inhibited this suppression, suggesting that reduced RNI production by MLN cells contributes to their maintenance of higher proliferative responses. These results demonstrated a clear difference in activity of T cells in the MLN and spleen during the acute stage of the infection.     

Quantitative assessment by flow cytometry of T-lymphocytes producing antigen-specific gamma-interferon in Brucella immune cattle

Peripheral blood mononuclear cells (PBMC) isolated from cattle infected with Brucella secreted gamma-interferon (IFN-gamma) after antigen-specific stimulation with Brucellergene, which is a mixture of cytoplasmic proteins of rough Brucella melitensis B115. Following the depletion of the monocyte-macrophages from the PBMC, the enriched lymphocyte populations stimulated with Brucellergene did not produce IFN-gamma. Two-colour immunofluorescence staining of intracellular IFN-gamma and bovine cell surface molecules identified the cells producing IFN-gamma among the PBMC stimulated with Brucellergene. Moreover, this method could be used to estimate the number of T-cells specifically producing IFN-gamma. For a given animal, there is a significant correlation (p < 0.05) between the production of IFN measured by an ELISA of the supernatant of whole blood stimulated with Brucellergene and the number of T-cells producing IFN-gamma after in vitro stimulation with Brucellergene. The development of the immunofluorescence staining technique provides a new tool for analysing and for measuring the T-cell immune response in cattle.     

Arginine-supplemented diets inhibit endotoxin-induced bacterial translocation in mice

We studied the effects of supplemental dietary arginine (ARG) on endotoxin-induced bacterial translocation. Mice were fed a 20%-casein diet (control) or a 20%-casein diet supplemented with 2% or 4% ARG and then injected with lipopolysaccharide (1 mg/500 microliters). The incidence of bacterial translocation was noted by the recovery of viable organisms from the mesenteric lymph node (MLN) and spleen. The mortality rates of the mice were 40%, 10%, and 20% in the control group and 2%- and 4%-ARG groups, respectively. Of the surviving mice, bacterial translocation occurred in 100% of the control group, in 56% (MLN) and 56% (spleen) in the 2%-ARG group, and in 36% (MLN) and 25% (spleen) in the 4%-ARG group. Quantitative colony counts and median numbers of viable bacteria were lower (p < 0.05) in the 2%-ARG group and slightly lower in the 4%-ARG group compared with the control group. MLN and spleen weights expressed as a percentage of body weight were heavier (p < 0.05) only in the 2%-ARG group. These results support the concept that bacteria may translocate from the gut to other organs and be a potential source of lethal infection after injury, and that supplementation with 2% or 4% ARG could improve outcome.     

Vaccination with glutaraldehyde-fixed bovine respiratory syncytial virus (BRSV)-infected cells stimulates a better immune response in lambs than vaccination with heat-inactivated cell-free BRSV

The lamb model was used to investigate the possible protective effects of vaccination with inactivated viral antigens against experimental infection with bovine respiratory syncytial virus. Two groups of eight lambs were vaccinated with either glutaraldehyde-inactivated cell-associated virus or heat-inactivated cell-free virus and subsequently challenged with live virus, along with a group of naive lambs. The virus was shed for significantly longer periods, and the virus titres in nasal secretions were significantly higher in the group of naive lambs than in the two groups of vaccinated lambs. The period of virus-shedding in nasal secretions and virus titres was significantly lower (p < 0.01) in the group of lambs immunized with the cell-associated preparation. The same antigen stimulated better cellular immune responses as measured by virus-specific cytotoxicity or by virus-specific lymphocyte proliferation. However, priming with inactivated vaccines had no significant effect on lymphocyte responses to phytohaemagglutinin, which was found to be significantly reduced (p < 0.01) following challenge with live virus.     

Peripheral cell-mediated immune response to mycobacterial antigens in inflammatory bowel disease

A mycobacterial etiology has been proposed in Crohn's disease (CD). We have sought evidence of increased or modified T lymphocyte immune responses to Mycobacterium tuberculosis and Myco, paratuberculosis in patients with CD (n = 13), compared with ulcerative colitis (UC; n = 17) and controls (n = 17). Peripheral blood cells were cultured with phytohaemagglutinin (positive mitogen control), mycobacterial purified protein derivative (PPD) preparations, lysates, column fractions and whole, heat-killed bacteria. Responses of T cells and T cell subsets were assessed by expression of activation markers (CD25, CD69), coupled with blastogenesis assays (3H-thymidine uptake) and estimates of proliferation. Virtually all patients responded to Myco. paratuberculosis and Myco. tuberculosis antigens. There were no significant differences between patient groups, although there was a very high overall correlation (r = 0.95; P < 0.0001) between responses to the two mycobacterial species. Most of the activation and proliferative responses resided in the CD4+ (T helper) subset. Although up to 15% of CD8+ (suppressor/cytotoxic) cells also became activated, the CD8+ cells did not proliferate subsequently. Cells expressing the alternate gamma delta form of the T cell receptor (TCR gamma delta+) did not activate or proliferate in response to mycobacterial antigens. There were no differences in any of these parameters between patient groups. We conclude that there is no specific increase or alteration in cell-mediated anti-mycobacterial immunity in inflammatory bowel disease (IBD). Thus our data do not support a mycobacterial etiopathology of Crohn's disease.     

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Mycobacterium avium subspecies paratuberculosis (M. paratuberculosis) is the etiologic agent of paratuberculosis (Johne's disease), a chronic granulomatous enteritis in ruminants. Currently, there is a need for improved diagnostic tests because of the lack of methods for accurate, rapid and reliable detection of M. paratuberculosis infection. A M. paratuberculosis gene (hspX) was cloned, sequenced, and a 30 bp species-specific oligonucleotide was synthesized. As an internal control to identify mycobacterial strains, a 33 bp Mycobacterium genus-specific oligonucleotide was synthesized based on the conserved 5' terminus of the mycobacterial recA gene. Dioligonucleotide hybridization (dOH) analysis identified 28/28 (100%) mycobacterial strains and specifically identified 14/14 (100%) reference (ATCC 19698), bovine, ovine and human isolates of M. paratuberculosis. The M. paratuberculosis-specific oligonucleotide distinguished M. paratuberculosis isolates from related mycobacteria, including all closely related members of the Mycobacterium avium complex (MAC) tested in this study. The members of MAC tested in this study included Mycobacterium avium subspecies avium (M. paratuberculosis, Mycobacterium avium subspecies silvaticum (M. silvaticum) and Mycobacterium intracellulare strains. Hybridization was not observed with DNA extracted from a selected group of other bacterial pathogens. The experiments indicate that the dOH analysis is a useful diagnostic tool to detect mycobacterial infection, specifically M. paratuberculosis. The dOH method could be a good alternative to existing assays and will be adapted for specific identification of M. paratuberculosis from faecal samples, mixed bacteriologic cultures, tissue specimens and whole blood.     

L-selectin and beta7 integrin synergistically mediate lymphocyte migration to mesenteric lymph nodes

Mesenteric lymph nodes (MLN) drain the gut where nutritive antigens and pathogens are encountered by lymphocytes of the gut-associated lymphoid tissue. We sought to determine how lymphocytes enter the MLN by studying mice double deficient for beta7 integrins and L-selectin. beta7/L-selectin double-deficient lymphocytes did not migrate into MLN. Most importantly, MLN formation was drastically impaired in beta7/L-selectin double-deficient mice. Lymphocyte numbers in MLN from beta7/L-selectin double-deficient mice were tenfold reduced compared to control mice. A high percentage of the few lymphocytes still detected in MLN from beta7/L-selectin double-deficient mice were CD44hi CD18hi, suggesting alternate migration pathways independent of L-selectin and beta7 integrin for these cells. We conclude that the combination of both molecules, L-selectin and beta7 integrin, is indispensable for MLN formation and that these molecules may mediate lymphocyte migration to MLN in a sequential and synergistical manner.     

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The ability of Mycobacterium avium subsp. paratuberculosis to survive in bovine monocytes was studied using radiometric (BACTEC) culture, standard plate counting and microscopic counting of acid-fast stained monocyte monolayers. Results of microscopic counts sharply contrasted with results of viable counts determined both by plate counting and radiometric counting. We observed an early phase (the first 6 d after in vitro infection) of intracellular bacillary growth, followed by a later phase of mycobacteriostasis or killing (up to 12 d after in vitro infection) in monocytes from non-infected cows. The data suggest that multiplication and death of M. avium subsp. paratuberculosis occur simultaneously in bovine monocytes infected in vitro. Using the BACTEC method, we compared the ability of bovine monocytes from normal cows and cows infected with M. avium subsp. paratuberculosis and showing evidence of a strong Thl-like cellular immune response to ingest and inhibit the intracellular growth of M. avium subsp. paratuberculosis. There was a trend toward greater phagocytosis and faster killing of Mycobacterium avium subsp. paratuberculosis by monocytes from the infected, immune responder cows. However, the observed numbers of viable M. avium subsp. paratuberculosis at each time after monocyte infection were not significantly different between normal and infected cows.     

Immunity to Cryptosporidium muris infection in mice is expressed through gut CD4+ intraepithelial lymphocytes

The role of gut intraepithelial lymphocytes (IEL) in immunity to cryptosporidial infection was investigated with a murine infection model involving Cryptosporidium muris. Oocyst shedding was monitored in severe combined immunodeficiency (SCID) mice infected with C. muris following intravenous injection of mesenteric lymph node (MLN) cells or intestinal IEL from BALB/c donor mice which were naive or previously infected with C. muris. SCID mice receiving no lymphoid cells developed chronic infections and excreted large numbers of oocysts until the end of the experiment. SCID mice injected with IEL from immune animals, however, were able to overcome the infection, and furthermore, these animals produced fewer oocysts and recovered sooner than ones which received IEL or MLN cells from naive BALB/c donors. Similar levels of protection were obtained in SCID mice injected with either 2 X 10(6) IEL or MLN cells from immune donor mice. Depletion of CD4+ cells from immune IEL, however, abrogated the ability to transfer immunity to SCID mice, while depletion of CD8+ cells only marginally reduced the protective capacity of immune IEL. Finally, control SCID mice which received no lymphocytes had < or = 1% CD4+ cells in the IEL from the small intestine, whereas the IEL from SCID mice recovered from infection, as a result of injection with immune IEL, contained 15% CD4+ cells. Thus, the ability to control C. muris infection correlated with the presence of the protective CD4+ cells in the gut epithelium.     

Infection with Salmonella typhimurium modulates the immune response to Schistosoma mansoni glutathione-S-transferase

Immune response polarization is controlled by several factors, including cytokines, antigen-presenting cells, antigen dose, and others. We have previously shown that adjuvants and live vectors play a critical role in polarization. Thus, immunization with the Schistosoma mansoni 28-kDa glutathione-S-transferase (Sm28-GST) in aluminum hydroxide induced a type 2 cytokine profile and the production of immunoglobulin G1 (IgG1)- and IgE-specific antibodies. In contrast, mice infected with recombinant Salmonella typhimurium expressing Sm28-GST developed a type 1 cytokine profile and produced IgG2a-specific antibodies against Sm28-GST and Salmonella antigens. In this study, to determine if S. typhimurium not expressing Sm28-GST would still influence the type of the response against this antigen, we compared the profiles of the immune responses generated against Sm28-GST administered in alum in mice infected and not infected with S. typhimurium. Infected mice generated both IgG1 and IgG2a antibodies against Sm28-GST, while noninfected mice produced only IgG1 anti-Sm28-GST antibodies. Moreover, interleukin-4 (IL-4) mRNA expression in infected mice was near background levels, while gamma interferon (IFN-gamma) mRNA expression in coinfected mice was significantly higher than in mice immunized with Sm28-GST in alum only. However, after antigen-specific stimulation in vitro with Sm28-GST, levels of IL-4 and IFN-gamma cytokine production were similar in the two groups of mice. These results suggest that (i) the immune milieu produced during an infection may modify the response against an irrelevant antigen and (ii) isotype switching may be influenced by the cytokine environment of a bystander immune response, even though the specific antigen-driven cytokine production is not modified. Thus, the isotypic profile is not always an absolute reflection of the cytokines produced by antigen-specific Th cells.     

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OBJECTIVE: To find out if lactulose can prevent the bacterial translocation that is induced by obstructive jaundice in rats. DESIGN: Laboratory experiment. SETTING: Teaching hospital, Turkey. MATERIAL: 50 male Wistar-albino rats. INTERVENTIONS: 10 rats were not operated on and used as controls; 20 rats underwent laparotomy and sham ligation of the common bile duct (CBD); 20 had the CBD ligated alone; and 20 had the CBD ligated and were given oral lactulose 2 ml/day until death. All rats were killed after 14 days. MAIN OUTCOME MEASURES: Presence of Escherichia coli in mesenteric lymph nodes (MLN), and bacterial overgrowth as indicated by counts of E coli in the caecum. RESULTS: There was significantly less bacterial translocation to MLN in the group that had been given lactulose compared with CBD-ligated and lactulose not given (2/20 compared with 8/20, p = 0.06). There was also a significant reduction in the number of Gram negative bacteria in that group (p = < 0.01). CONCLUSION: Lactulose seems to reduce the incidence of translocation from the gut to MLN in rats with obstructive jaundice.     

Paratuberculosis

Paratuberculosis (Johne's disease) is a chronic, wasting, widespread mycobacteriosis of ruminants. It involves extensive mycobacterial shedding, which accounts for the high contagiousness, and ends with a fatal enteritis. Decreases in weight, milk production, and fertility produce severe economic loss. The DNA of the etiological agent (Mycobacterium paratuberculosis) has a base composition (66 to 67% G+C) within the range of that of mycobacteria (62 to 70% G+C), a size (4.4 x 10(6) to 4.7 x 10(6) bp) larger than that of most pathogenic mycobacteria (2.0 x 10(6) to 4.2 x 10(6) bp), and a high relatedness (> 90%) to Mycobacterium avium DNA. However, the DNAs of the two organisms can be distinguished by restriction fragment length polymorphism analysis. M. paratuberculosis genes coding for a transposase, a cell wall-associated protein (P34), and two heat shock proteins have been cloned and sequenced. Nucleic acid probes (two of which are species specific) are used, after PCR amplification, for M. paratuberculosis identification in stools and milk. As in leprosy, with disease progression, cellular immune reactions decrease and humoral immune reactions increase. Cutaneous testing with sensitins, lymphocyte proliferation assays, and cytokine tests are used to monitor cellular immune reactions in paratuberculosis, but these tests lack specificity. Complement fixation, immunodiffusion, and enzymometric tests based on antibodies to M. paratuberculosis extracts, to mycobacterial antigen complex A36, to glycolipids, and to proteins help identify affected cattle but are not species specific. The carboxyl-terminal portion of the 34-kDa cell wall-associated A36 protein (P34) carries species-specific B-cell epitopes and is the basis for an enzyme-linked immunosorbent assay. Diagnostic tests for paratuberculosis are also used in Crohn's disease, a chronic human ileitis mimicking Johne's disease, in which isolates identified as M. paratuberculosis have been found.     

Study of T-lymphocyte subsets of healthy and Mycobacterium avium subsp. paratuberculosis-infected cattle

The relative contributions of T-lymphocyte subsets to host defense in cattle infected with Mycobacterium avium subsp. paratuberculosis is reported. The subsets were purified with appropriate monoclonal antibodies and a magnetic bead column separation system, and their purity was verified by flow cytometry. Biological activity of each subset, expressed as lymphoproliferation and gamma interferon (IFN-gamma) production, was measured in response to phytohemagglutinin (PHA) and an M. avium antigen preparation (A-PPD). IFN-gamma was measured by antibody capture enzyme-linked immunosorbent assay. The results showed a correlation between proliferation and IFN-gamma production in response to A-PPD but not to PHA. In response to PHA, CD4+ lymphocytes were the most prolific producers of IFN-gamma. CD8+ lymphocytes produced IFN-gamma to a lesser extent, whereas gammadelta+ T lymphocytes produced little or no IFN-gamma. Differences observed between the amount of IFN-gamma produced by CD4+ versus CD8+ cells and CD4+ versus gammadelta+ cells were significant (P < 0.01), but those between peripheral blood mononuclear cells (PBMC) and CD4+ T cells were not. Similar responses to A-PPD were observed except that PBMC produced higher levels of IFN-gamma than did CD4+ T cells. These data for cattle are similar to observations made for other animal species, where CD4+ cells are the major type of T lymphocytes producing IFN-gamma. They further suggest that whatever the role gammadelta+ T cells may play in paratuberculosis, it is not likely to be mediated by IFN-gamma production.     

Cellular dynamics and cytokine responses in BALB/c mice infected with Eimeria papillata during primary and secondary infections

BALB/c mice were infected with the intestinal intracellular parasite Eimeria papillata to characterize lymphocyte responses and cytokine profiles throughout primary and secondary infections. Lymphocytes from the mesenteric lymph node (MLN) and the gastrointestinal tract (GIT) of infected mice were phenotypically analyzed using flow cytometry and immunofluorescence microscopy, respectively. Lymphocytes isolated from the MLN during primary infections of BALB/c mice with E. papillata do not proliferate, compared to day 0 uninfected controls, when stimulated in vitro with conconavalin A and express TH2-type cytokines (interleukin [IL]-4 and IL-10) on day 3 PI followed by the release of TH1-type cytokines (IL-2 and interferon-gamma) during patency. In the small intestine, significantly more T cells and their subsets were observed during primary infection. During secondary infections, IL-2 was the only 1 of the 4 cytokines that was expressed earlier and at higher levels in the MLN when compared to primary infections. In the small intestine, significantly more alphabeta+ and CD8+ T lymphocytes were observed in mice during secondary infection. Oocyst antigens did not induce cellular proliferation at any time point during primary or secondary infections. We conclude that primary oral infection of BALB/c mice with E. papillata is associated with localized immunosuppression that may be mediated, in part, by early TH2-type cytokines. Immunity to secondary infection may be mediated by intestinal alphabeta+ CD8+ T lymphocytes through an IL-2-dependent mechanism.     

Antibody-secreting cells specific for simian immunodeficiency virus antigens in lymphoid and mucosal tissues of immunized macaques

OBJECTIVES: To examine whether the route of immunization affects the induction of antibody-secreting cells (ASC) in the circulation of macaques. The distribution of ASC in the rectal mucosa and lymphoid tissues following challenge with simian immunodeficiency virus (SIV) was investigated. DESIGN: Macaques were immunized with recombinant SIV gp120 and p27 antigens by the targeted iliac lymph node (TILN) route of immunization or the nasal and rectal route, augmented by intramuscular immunization [naso-rectal intramuscular (NRI)]. The macaques were challenged with live SIV by the rectal route and ASC were assayed in the circulation before and after SIV challenge, and in the tissues removed at post-mortem. METHODS: ASC were examined in the circulation by Elispot assay. Mononuclear cells were prepared from peripheral blood, iliac and axillary lymph nodes and spleen. Rectal tissue was treated by enzyme digestion to elute mononuclear cells. RESULTS: TILN and NRI immunization induced circulating IgA and IgG ASC to both gp120 and p27. Following rectal challenge with SIV, TILN macaques were protected from infection whereas NRI route-immunized and unimmunized controls became infected. IgA ASC to p27 were increased significantly in the iliac lymph nodes of the TILN immunized macaques compared with unimmunized controls (P < 0.05). Only IgA ASC were found in the rectal mucosa of the immunized protected macaques but both IgA and IgG ASC were detected in the unimmunized infected macaques. Overall the number of IgG ASC specific for p27 was significantly higher in the infected NRI and control macaques than in the protected macaques (P < 0.02). A progressive increase in IgG but not IgA ASC was detected in the peripheral blood mononuclear cells of the unimmunized infected macaques. CONCLUSIONS: The results suggest that cells secreting IgA antibodies to p27 in the iliac lymph nodes of the TILN immunized macaques correlate significantly with protection from infection. The unimmunized infected macaques showed a progressive increase in IgG ASC in the peripheral blood after SIV challenge; this was found in the iliac and axillary lymph nodes and also in the spleen, suggesting that it is an immune response to the SIV infection.