Changes in the peripheral blood T-Cell receptor V beta repertoire in vivo and in vitro during shigellosis

A clinically parameterized mathematical model of Shigella immunity to inform vaccine design

We refine and clinically parameterize a mathematical model of the humoral immune response against Shigella, a diarrheal bacteria that infects 80-165 million people and kills an estimated 600,000 people worldwide each year. Using Latin hypercube sampling and Monte Carlo simulations for parameter estimation, we fit our model to human immune data from two Shigella EcSf2a-2 vaccine trials and a rechallenge study in which antibody and B-cell responses against Shigella′s lipopolysaccharide (LPS) and O-membrane proteins (OMP) were recorded. The clinically grounded model is used to mathematically investigate which key immune mechanisms and bacterial targets confer immunity against Shigella and to predict which humoral immune components should be elicited to create a protective vaccine against Shigella. The model offers insight into why the EcSf2a-2 vaccine had low efficacy and demonstrates that at a group level a humoral immune response induced by EcSf2a-2 vaccine or wild-type challenge against Shigella′s LPS or OMP does not appear sufficient for protection. That is, the model predicts an uncontrolled infection of gut epithelial cells that is present across all best-fit model parameterizations when fit to EcSf2a-2 vaccine or wild-type challenge data. Using sensitivity analysis, we explore which model parameter values must be altered to prevent the destructive epithelial invasion by Shigella bacteria and identify four key parameter groups as potential vaccine targets or immune correlates: 1) the rate that Shigella migrates into the lamina propria or epithelium, 2) the rate that memory B cells (B_M) differentiate into antibody-secreting cells (ASC), 3) the rate at which antibodies are produced by activated ASC, and 4) the Shigella-specific B_M carrying capacity. This paper underscores the need for a multifaceted approach in ongoing efforts to design an effective Shigella vaccine.

Applying mathematical tools to accelerate vaccine development: modeling Shigella immune dynamics

We establish a mathematical framework for studying immune interactions with Shigella, a bacteria that kills over one million people worldwide every year. The long-term goal of this novel approach is to inform Shigella vaccine design by elucidating which immune components and bacterial targets are crucial for establishing Shigella immunity. Our delay differential equation model focuses on antibody and B cell responses directed against antigens like lipopolysaccharide in Shigella’s outer membrane. We find that antibody-based vaccines targeting only surface antigens cannot elicit sufficient immunity for protection. Additional boosting prior to infection would require a four-orders-of-magnitude increase in antibodies to sufficiently prevent epithelial invasion. However, boosting anti-LPS B memory can confer protection, which suggests these cells may correlate with immunity. We see that IgA antibodies are slightly more effective per molecule than IgG, but more total IgA is required due to spatial functionality. An extension of the model reveals that targeting both LPS and epithelial entry proteins is a promising avenue to advance vaccine development. This paper underscores the importance of multifaceted immune targeting in creating an effective Shigella vaccine. It introduces mathematical models to the Shigella vaccine development effort and lays a foundation for joint theoretical/experimental/clinical approaches to Shigella vaccine design.

Progress and pitfalls in Shigella vaccine research

Renewed awareness of the substantial morbidity and mortality that Shigella infection causes among young children in developing countries, combined with technological innovations in vaccinology, has led to the development of novel vaccine strategies in the past 5 years. Along with advancement of classic vaccines in clinical trials and new sophisticated measurements of immunological responses, much new data has been produced, lending promise to the potential for production of safe and effective Shigella vaccines. Herein, we review the latest progress in Shigella vaccine development within the framework of persistent obstacles.

Antigen-specific CD8(+) T cells fail to respond to Shigella flexneri

CD8(+) T lymphocytes often play a primary role in adaptive immunity to cytosolic microbial pathogens. Surprisingly, CD8(+) T cells are not required for protective immunity to the enteric pathogen Shigella flexneri, despite the ability of Shigella to actively secrete proteins into the host cytoplasm, a location from which antigenic peptides are processed for presentation to CD8(+) T cells. To determine why CD8(+) T cells fail to play a role in adaptive immunity to S. flexneri, we investigated whether antigen-specific CD8(+) T cells are primed during infection but are unable to confer protection or, alternatively, whether T cells fail to be primed. To test whether Shigella is capable of stimulating an antigen-specific CD8(+) T-cell response, we created an S. flexneri strain that constitutively secretes a viral CD8(+) T-cell epitope via the Shigella type III secretion system and characterized the CD8(+) T-cell response to this strain both in mice and in cultured cells. Surprisingly, no T cells specific for the viral epitope were stimulated in mice infected with this strain, and cells infected with the recombinant strain were not targeted by epitope-specific T cells. Additionally, we found that the usually robust T-cell response to antigens artificially introduced into the cytoplasm of cultured cells was significantly reduced when the antigen-presenting cell was infected with Shigella. Collectively, these results suggest that antigen-specific CD8(+) T cells are not primed during S. flexneri infection and, as a result, afford little protection to the host during primary or subsequent infection.

Adaptive immune responses during Shigella dysenteriae type 1 infection: an in vitro stimulation with 57 kDa major antigenic OMP in the presence of anti-CD3 antibody

An effort was made to understand the role of the 57 kDa major antigenic fraction of Shigella outer membrane protein (OMP) in the presence of T-cell antigen receptor in activation of adaptive immune responses of the cell mediated immune (CMI) restored patients. The expression of HLA-DR/CD4 out of CD3(+) T-cells was significantly dominant over the HLA-DR/CD8 and comparable to unstimulated cells of infected or healthy controls. CD4(+) T-cell activation together with HLA-DR is associated with the expression of CD25(+) (IL2Ralpha) for IL-2 growth factors with decreased IL-4 levels, required for maintaining the homeostasis of CD4(+) T cell. Furthermore, the positive expression of the CD45 antigen is possibly required for acquiring the memory for CD4(+) cells signals and facilitates the interaction with CD54 antigen. As a result, antigen-specific secondary signal is generated for B-cell activation to produce IgG2a and IgG2b. This suggests that antibody mediated-adaptive immune responses are generated due to anti-CD3 induced helper T-cell activity. The above mentioned findings reflect that the antigen alone might not exacerbate the selective T-cell responses. But these antigens in the presence of anti-CD3 antibody might help to elicit adaptive immune response via T-cell receptor (TCR) activation.

Th17 cells are the dominant T cell subtype primed by Shigella flexneri mediating protective immunity

The T cell response to Shigella, the causative agent of bacillary dysentery, remains poorly understood. Using a murine model of infection, we report that Shigella flexneri primes predominately IL-17A- and IL-22-producing Th17 cells. Shigella-specific Th1 cells are only significantly induced on secondary infection, whereas specific Th2 and CD8(+) T cells are undetectable. Apart from Th17 cells that are primed in a MHC class II- and IL-6-dependent, but IL12/23p40-independent manner, we identified gammadelta T cells as an additional but minor source of IL-17A. Priming of IL-17A(+) gammadelta T cells is dependent on IL12/23p40, but independent of MHC-class II and IL-6. Th17 cells have emerged as important players in inflammatory, autoimmune, and infectious diseases. Among the yet unresolved questions is their role in long-term immunity to pathogens. In this study, we show that the elicited S. flexneri-specific Th17 pool gives rise to an enhanced recall response up to 12 mo after priming, suggesting the presence of a long-term memory state. The clearance of primary infection is impaired in the absence of T cells, but independently of IL-17A. However, after reinfection, IL-17A produced by S. flexneri-specific Th17 cells becomes important to ultimately restrict bacterial growth. These findings bring new insights into the adaptive immune response to Shigella infection and highlight the importance of pathogen-specific Th17 cell immunity for secondary immune protection.

T cell activation profiles in Kawasaki syndrome

Superantigens (SAgs) are potent stimulators of T cells bearing specific Vbeta T cell receptors (TCR) and may play a role in the pathogenesis of Kawasaki syndrome (KS), although despite 15 years of intense study this area remains controversial. Because SAgs can cause Vbeta restricted T cell activation in the absence of Vbeta skewing the aims of this study were to describe a flow cytometric protocol to study both CD4 and CD8 Vbeta repertoires, and CD69 expression across the CD4 and CD8 Vbeta repertoire in children with KS. Sixteen children with KS were studied. There was no significant increase in overall peripheral blood CD4 or CD8 T cell activation as determined by CD69 expression. However, Vbeta restricted CD4 and/or CD8 activation was observed in eight of 11 (72%) of the KS patients, a finding not observed in healthy controls. Thirteen of 16 (81%) of the KS patients had evidence of either Vbeta skewing (particularly CD4 Vbeta2 and Vbeta5.1) and/or Vbeta restricted activation. Three patients had Vbeta restricted activation in the absence of skewing. We suggest that these preliminary observations highlight the many layers of complexity when considering T cell activation in KS, which could explain some of the conflicting studies regarding peripheral blood T cell activation and Vbeta skewing. It is likely that in order to move forward with this debate a combination of detailed microbiological, immunological and molecular techniques applied to individual patients will be required ultimately to prove or refute the SAg hypothesis of KS.

Clinical trials of Shigella vaccines: two steps forward and one step back on a long, hard road

More than 50 years of research has yielded numerous Shigella vaccine candidates that have exemplified both the promise of vaccine-induced prevention of shigellosis and the impediments to developing a safe and effective vaccine for widespread use, a goal that has yet to be attained. This Review discusses the most advanced strategies for Shigella vaccine development, the immune responses that are elicited following disease or vaccination, the factors that have accelerated or impeded Shigella vaccine development and our ideas for the way forward.

Shigella’ s ways of manipulating the host intestinal innate and adaptive immune system: a tool box for survival?

Shigella, a Gram-negative invasive enteropathogenic bacterium, causes the rupture, invasion and inflammatory destruction of the human colonic epithelium. This complex and aggressive process accounts for the symptoms of bacillary dysentery. The so-called invasive phenotype of Shigella is linked to expression of a type III secretory system (TTSS) injecting effector proteins into the epithelial cell membrane and cytoplasm, thereby inducing local but massive changes in the cell cytoskeleton that lead to bacterial internalization into non-phagocytic intestinal epithelial cells. The invasive phenotype also accounts for the potent pro-inflammatory capacity of the microorganism. Recent evidence indicates that a large part of the mucosal inflammation is initiated by intracellular sensing of bacterial peptidoglycan by cytosolic leucine-rich receptors of the NOD family, particularly NOD1, in epithelial cells. This causes activation of the nuclear factor kappa B and c-JunNH(2)-terminal-kinase pathways, with interleukin-8 appearing as a major chemokine mediating the inflammatory burst that is dominated by massive infiltration of the mucosa by polymorphonuclear leukocytes. Not unexpectedly, this inflammatory response, which is likely to be very harmful for the invading microbe, is regulated by the bacterium itself. A group of proteins encoded by Shigella, which are injected into target cells by the TTSS, has been recently recognized as a family of potent regulators of the innate immune response. These enzymes target key cellular functions that are essential in triggering the inflammatory response, and more generally defense responses of the intestinal mucosa. This review focuses on the mechanisms employed by Shigella to manipulate the host innate response in order to escape early bacterial killing, thus ensuring establishment of its infectious process. The escape strategies, the possible direct effect of Shigella on B and T lymphocytes, their impact on the development of adaptive immunity, and how they may help explain the limited protection induced by natural infection are discussed.

Immunization of volunteers with Salmonella enterica serovar Typhi strain Ty21a elicits the oligoclonal expansion of CD8+ T cells with predominant Vbeta repertoires

CD8(+) T cells are likely to play an important role in host defense against Salmonella enterica serovar Typhi by several effector mechanisms, including lysis of infected cells (cytotoxicity) and gamma interferon (IFN-gamma) secretion. In an effort to better understand these responses, we studied the T-cell receptor (TCR) repertoire of serovar Typhi-specific CD8(+) T cells in humans. To this end, we determined the TCR beta chain (Vbeta) usage of CD8(+) T cells from three volunteers orally immunized with Ty21a typhoid vaccine by flow cytometry using a panel of monoclonal antibodies. Although TCR Vbeta usage varied among volunteers, we identified oligoclonal Vbeta subset expansions in individual volunteers (Vbeta 2, 5.1, 8, 17, and 22 in volunteer 1; Vbeta 1, 2, 5.1, 14, 17, and 22 in volunteer 2; and Vbeta 3, 8, 14, and 16 in volunteer 3). These subsets were antigen specific, as shown by cytotoxicity and IFN-gamma secretion assays on Vbeta sorted cells and on T-cell clones derived from these volunteers. Moreover, eight-color flow cytometric analysis showed that these clones exhibited a T effector memory phenotype (i.e., CCR7(-) CD27(-) CD45RO(+) CD62L(-)) and coexpressed gut homing molecules (e.g., high levels of integrin alpha4beta7, intermediate levels of CCR9, and low levels of CD103). In conclusion, our results show that long-term T-cell responses to serovar Typhi in Ty21a vaccinees are oligoclonal, involving multiple TCR Vbeta families. Moreover, these serovar Typhi-specific CD8(+) T cells bearing defined Vbeta specificities are phenotypically and functionally consistent with T effector memory cells with preferential gut homing potential.

Role of anti-CD3 in modulation of Th1-type immune response in Shigella dysenteriae infection

A murine model was used to evaluate the role of anti-CD3 in modulating a Th1-type response by restimulation of T-cells after immunization with the 57 kDa immunodominant antigen of Shigella dysenteriae 1 outer-membrane proteins (OMPs), followed by Shigella infection after immunization. To observe the effect of anti-CD3, other T-cell cultures were also established following anti-CD1, anti-IL2 and phytohaemagglutinin stimulation. Anti-CD3 stimulation of reconstituted T-cells showed 'mean' levels of CD4 and CD25 were enhanced by 34.5 and 31.1 % in immunized mice, which was comparable to 53.2 and 50.7 %, respectively, in challenged-immunized mice, and were dominant over CD8+ T-cells. Levels of IL2 generated by anti-CD3-stimulated T-cells of immunized mice were greater than those of unstimulated T-cells and were significantly elevated in challenged-immunized mice. The reactivity of T-cells indicated their complete responsiveness, as anti-CD3 antibody might not inhibit the migration of the macrophages but rather inhibit IL4. These macrophage factors synergistically act with anions towards an activated response, which in turn provokes IL2 secretion with a low degree of internalization of its receptor. Thus, sharing of IL2 to form a high-affinity receptor complex with CD4+ T-cells through motive signals suggested a generalized T-cell activation with increased humoral responses. Macrophage migration inhibition factor (MIF) and IL4 responses during anti-CD3 stimulation of immunized mice indicated that the role of anti-CD3 in generation of O2- is due to a synergistic effect by Th1 subsets of Th0 cells. The above findings should have implications for understanding the immunoregulatory role of anti-CD3 associated with 57 kDa antigen in immunoprophylactic measures.

Role of 57 kDa major antigenic component of Shigella dysenteriae outer membrane proteins in induction of major histocompatibility complex II-restricted T-cell response

BACKGROUND

In the past, many Shigella surface antigens were used to activate both T and B lymphocytes but failed to induce antigen-specific responses in Shigellosis. Our objective was to identify in vitro T-cell components using 57 kDa major antigenic fraction of Shigella dysenteriae 1 (IPC-31) outer membrane proteins (OMPs) in modulating specific T-cell subset responses against Shigellosis.

METHODS

Antigen-specific T- and B-cell activation was studied in immunized Balb/c mice against 57 kDa antigen by proliferative responses using [3H]-thymidine incorporation and avidin-biotin complex (ABC) peroxidase staining for CD4, CD8, CD3, CD22, and CD25 followed by IL-2 and IL-4 estimation. Macrophage functional assays for migration inhibition factors (MIF) and superoxide (O2-) anions were also performed against 57 kDa antigen, whole OMPs, and phytohemagglutinin (PHA) stimulation.

RESULTS

Greater increase of lymphocyte proliferation was observed after 57 kDa antigen stimulation than post-OMP and -PHA stimulation. Proportionately, CD4+ and CD25+ expression of total CD3+ T-cells was significantly dominant (p >0.05) over CD8+ T-cells. On day 7 of this stimulation, it was found to increase % MIF and O2- anions with decrease of IL-2 leading to activation of MHC-II antigens. Later, on day 28 of immunization, IL-2 levels were more increased than on days 7 and 14 but insignificant with non-immunized mice stimulated with 57 kDa. Levels of IL-2 were also noted with low degree of internalization to its IL-2R receptors rather than to IL-4 receptors. In parallel, expression of CD22 was also recorded higher in this stimulation than in PHA, indicating a T-cell-dependent humoral response.

CONCLUSIONS

Our results suggested that 57 kDa major antigenic OMP is immunogenic for MHC II-restricted T-cell response to acquire host defense against Shigella infection.

Shigella flexneri infection: pathogenesis and vaccine development

Shigella flexneri is a gram-negative bacterium which causes the most communicable of bacterial dysenteries, shigellosis. Shigellosis causes 1.1 million deaths and over 164 million cases each year, with the majority of cases occurring in the children of developing nations. The pathogenesis of S. flexneri is based on the bacteria's ability to invade and replicate within the colonic epithelium, which results in severe inflammation and epithelial destruction. The molecular mechanisms used by S. flexneri to cross the epithelial barrier, evade the host's immune response and enter epithelial cells have been studied extensively in both in vitro and in vivo models. Consequently, numerous virulence factors essential to bacterial invasion, intercellular spread and the induction of inflammation have been identified in S. flexneri. The inflammation produced by the host has been implicated in both the destruction of the colonic epithelium and in controlling and containing the Shigella infection. The host's humoral response to S. flexneri also appears to be important in protecting the host, whilst the role of the cellular immune response remains unclear. The host's immune response to shigellosis is serotype-specific and protective against reinfection by the same serotype, making vaccination a possibility. Since the 1940s vaccines for S. flexneri have been developed with little success, however, the growing understanding of S. flexneri's pathogenesis and the host's immune response is assisting in the generation of more refined vaccine strategies. Current research encompasses a variety of vaccine types, which despite disparity in their efficacy and safety in humans represent promising progress in S. flexneri vaccine development.

Persistence of mucosal mast cells and eosinophils in Shigella-infected children

Cells of the innate immune system and their mediators were studied at the single-cell level in the rectums of pediatric and adult patients with Shigella infection to better understand why children are at higher risk for severe infection. Adult patients had increased infiltration of mucosal mast cells (MMC) at the acute stage (3 to 5 days after the onset of diarrhea) and eosinophils in early convalescence (14 to 16 days after onset). Increased expression of stem cell factor and prostaglandin H synthase-1 (PGHS-1) was associated with increased tryptase-K(i)67-double-positive MMC in the acute stage and increased apoptosis of MMC, which led to a rapid decline in early convalescence. The eosinophils demonstrated increased expression of major basic protein (MBP), eotaxin, and CCR3, as well as increased necrotic death. The neutrophils showed enhanced alpha-defensin and lactoferrin expression in the acute phase. In contrast to adults, the pediatric patients demonstrated delayed accumulation of mast cells and eosinophils, while alpha-defensin expression persisted during convalescence. In contrast, neutrophil counts and lactoferrin expression were reduced in children compared to adults. The results suggest that children with shigellosis have a persistent activation of the innate immune response in the convalescent phase, indicating delayed elimination of Shigella antigens compared to adults.

Parameters underlying successful protection with live attenuated mutants in experimental shigellosis

Because the use of live attenuated mutants of Shigella spp. represents a promising approach to protection against bacillary dysentery (M. E. Etherridge, A. T. M. Shamsul Hoque, and D. A. Sack, Lab. Anim. Sci. 46:61-66, 1996), it becomes essential to rationalize this approach in animal models in order to optimize attenuation of virulence in the vaccine candidates, as well as their route and mode of administration, and to define the correlates of protection. In this study, we have compared three strains of Shigella flexneri 5--the wild-type M90T, an aroC mutant, and a double purE aroC mutant--for their pathogenicity, immunogenicity, and protective capacity. Protection against keratoconjunctivitis, induced by wild-type M90T, was used as the protection read out in guinea pigs that were inoculated either intranasally or intragastrically. Following intranasal immunization, the aroC mutant elicited weak nasal tissue destruction compared to M90T and achieved protection correlated with high levels of local anti-lipopolysaccharide immunoglobulin A (IgA), whereas the purE aroC double mutant, which also elicited weak tissue destruction, was not protective and elicited a low IgA response. Conversely, following intragastric immunization, only the M90T purE aroC double mutant elicited protection compared to both the aroC mutant and the wild-type strain. This mutant caused mild inflammatory destruction, particularly at the level of Peyer's patches, but it persisted much longer within the tissues. This could represent an essential parameter of the protective response that, in this case, did not clearly correlate with high anti-lipopolysaccharide IgA titers.

The pathogenesis of Shigella flexneri infection: lessons from in vitro and in vivo studies

Shigella flexneri is a Gram-negative facultatively intracellular pathogen responsible for bacillary dysentery in humans. More than one million deaths occur yearly due to infections with Shigella spp. and the victims are mostly children of the developing world. The pathogenesis of Shigella centres on the ability of this organism to invade the colonic epithelium where it induces severe mucosal inflammation. Much information that we have gained concerning the pathogenesis of Shigella has been derived from the study of in vitro models of infection. Using these techniques, a number of the molecular mechanisms by which Shigella invades epithelial cells and macrophages have been identified. In vivo models of shigellosis have been hampered since humans are the only natural hosts of Shigella. However, experimental infection of macaques as well as the murine lung and rabbit ligated ileal loop models have been important in defining some of the immune and inflammatory components of the disease. In particular, the murine lung model has shed light on the development of systemic and local immune protection against Shigella infection. It would be naive to believe that any one model of Shigella infection could adequately represent the complexity of the disease in humans, and more sophisticated in vivo models are now necessary. These models require the use of human cells and tissue, but at present such models remain in the developmental stage. Ultimately, however, it is with such studies that novel treatments and vaccine candidates for the treatment and prevention of shigellosis will be designed.

Production of IFN-gamma and IL-10 to Shigella invasins by mononuclear cells from volunteers orally inoculated with a Shiga toxin-deleted Shigella dysenteriae type 1 strain

Volunteers were orally administered invasive, non-Shiga toxin-producing Shigella dysenteriae 1 to establish a challenge model to assess vaccine efficacy. In stepwise fashion, four separate groups were given 3 x 10(2), 7 x 10(3), 5 x 10(4), or 7 x 10(5) CFU. Using PBMC, proliferative responses and cytokine production were measured to S. dysenteriae whole-cell preparations and to purified recombinant invasion plasmid Ags (Ipa) C and IpaD. Anti-LPS and anti-Ipa Abs and Ab-secreting cells were also evaluated. Preinoculation PBMC produced considerable quantities of IL-10 and IFN-gamma, probably secreted by monocytes and NK cells, respectively, of the innate immune system. Following inoculation, PBMC from 95 and 87% of volunteers exhibited an increased production of IFN-gamma and IL-10, respectively, in response to Shigella Ags. These increases included responses to IpaC and IpaD among those volunteers receiving the lowest inoculum. No IL-4 or IL-5 responses were detected. Whereas there were no Ab or Ab-secreting cell responses in volunteers receiving the lowest inoculum, other dose groups had moderate to strong anti-LPS and anti-Ipa responses. These results suggest that in humans, type 1 responses play an important role in mucosal and systemic immunity to S. dysentariae 1.

Increased usage of TCR V-beta8 in kidney transplant recipients with aberrant immune reconstitution and clinical complications

BACKGROUND

The efficiency of immunosuppressive drugs prescribed after organ transplantation is mostly monitored through clinical and biological signs of organ rejection or infection. However, it may be expected that some patients develop subtle alterations of their reconstituting immune system, not immediately associated with clinical events. Identification of such anomalies could be useful to alert clinicians for possible future complications.

METHODS

A systematic follow-up of peripheral lymphocyte subsets, performed in a cohort of 89 kidney transplant recipients, identified severely skewed CD4/CD8 ratios in 32 patients. For 19 patients, the expression of specific T cell receptor fragments was examined using a panel of 10 monoclonal antibodies. Abnormal control of spontaneously Epstein Barr virus-infected B cells was tested by investigating for the generation of spontaneous lymphoblastoid cell lines in 17 cases. The incidence of rejection and infectious episodes was monitored.

RESULTS

A bias in T cell receptor fragments usage was detected in 14/19 cases, involving Vbeta8 in all cases. Spontaneous lymphoblastoid cell lines of Epstein Barr positive B blasts developed in 9 of 17 cases. Eleven patients had early rejection episodes and 16 presented with viral primo-infection or reactivation. The incidence of rejection and infectious episodes was higher in the group of 32 patients who developed such abnormal patterns than in the 57 who did not.

CONCLUSION

Transient bias in the T cell receptor repertoire may be observed during immune reconstitution after kidney transplantation, perhaps related to abnormal lymphocyte functions and associated to an impaired control of rejection and/or infectious agents.

Biased TCR Repertoire in Infiltrating Lesional T Cells in Human Bancroftian Filariasis

To investigate the hypothesis that T cells recognizing specific Ags localize to the site of disease activity in human bancroftian filariasis, we have compared the repertoire of TCR Vβ gene segments in lesions vs blood in individual patients by RT-PCR ELISA. Vβ14 and Vβ24 were overrepresented (5% greater in tissue compared with PBMCs and/or tissue/PBMC ratios in the highest 5% of all tissue/PBMC ratios for all Vβs for all subjects) in 50% and 40% of study subjects, respectively. Overrepresentation of these two Vβs did not occur in any control subject. In comparing three patient groups, the proportion of individuals meeting at least one criterion for Vβ14 overrepresentation was shown to increase in tandem with our current concepts of disease progression (asymptomatic filariasis = 25%; clinical filariasis with active infection = 60%; clinical filariasis without active infection = 71%). In 6 of the 10 individuals with Vβ14 overrepresentation, Vβ14 represented >20% of the entire lesional Vβ repertoire. All but one of the 20 study subjects had at least one Vβ gene segment that was overrepresented in tissue compared with PBMCs. Only a small number of Vβs, usually three or less, were overrepresented in any single filariasis patient. However, in the same tissue, no differences between patient groups were found when IFN-γ, TNF-α, IL-4, IL-5, and IL-12 mRNA expression were examined. Taken together, these findings suggest that, in principle, in essentially all patients, whether with subclinical or with clinical filariasis, distinct and limited T cell populations are concentrated in affected tissue.

Higher proportion of CD8+ T cells in the blood in healthy adults from Ethiopia and Bangladesh compared with Sweden

The phenotypic composition of peripheral blood lymphocytes in 45 healthy adults (15 each from Bangladesh, Ethiopia and Sweden) was analysed as an indicator of the influence of environment and/or ethnic background on the human immune response. The possible interference of technical factors was minimized by highly standardized handling of samples and by use of a similar simultaneous 3-colour flow cytometry analysis technique for all samples. The percentage of CD4+ cells was lower, and the percentage of CD8+ cells was higher, in Bangladeshi and Ethiopian subjects than in those from Sweden. A higher percentage of CD57+/CD8+ T cells was also found in these 2 groups than in Swedish subjects. The percentage of gamma delta T cells was higher in Bangladeshi subjects and a difference in T cell receptor V beta expression was also noted between Bangladeshi and Swedish subjects. The data suggest that environmental or genetic factors are important bias factors to be considered in immunophenotyping studies. Possibly differences in the pattern or level of microbial challenge, as well as nutritional factors, may lead to different adaptive changes in the immune response. The potential influence of such immune adaptation on the response to vaccination or pharmaceutical therapy may be important in the development of new strategies of medical intervention in different geographical regions or ethnic groups.