FR104, an antagonist anti-CD28 monovalent fab' antibody, prevents alloimmunization and allows calcineurin inhibitor minimization in nonhuman primate renal allograft.

Selective targeting of CD28 might represent an effective immunomodulation strategy by preventing T cell costimulation, while favoring coinhibition since inhibitory signals transmitted through CTLA-4; PD-L1 and B7 would not be affected. We previously showed in vitro and in vivo that anti-CD28 antagonists suppress effector T cells while enhancing regulatory T cell (Treg) suppression and immune tolerance. Here, we evaluate FR104, a novel antagonist pegylated anti-CD28 Fab' antibody fragment, in nonhuman primate renal allotransplantation. FR104, in association with low doses of tacrolimus or with rapamycin in a steroid-free therapy, prevents acute rejection and alloantibody development and prolongs allograft survival. However, when FR104 was associated with mycophenolate mofetil and steroids, half of the recipients rejected their grafts prematurely. Finally, we observed an accumulation of Helios-negative Tregs in the blood and within the graft after FR104 therapy, confirmed by Treg-specific demethylated region DNA analysis. In conclusion, FR104 reinforces immunosuppression in calcineurin inhibitor (CNI)-low or CNI-free protocols, without the need of steroids. Accumulation of intragraft Tregs suggested the promotion of immunoregulatory mechanisms. Selective CD28 antagonists might become an alternative CNI-sparing strategy to B7 antagonists for kidney transplant recipients.

Bortezomib, C1-inhibitor and plasma exchange do not prolong the survival of multi-transgenic GalT-KO pig kidney xenografts in baboons.

Galactosyl-transferase KO (GalT-KO) pigs represent a potential solution to xenograft rejection, particularly in the context of additional genetic modifications. We have performed life supporting kidney xenotransplantation into baboons utilizing GalT-KO pigs transgenic for human CD55/CD59/CD39/HT. Baboons received tacrolimus, mycophenolate mofetil, corticosteroids and recombinant human C1 inhibitor combined with cyclophosphamide or bortezomib with or without 2-3 plasma exchanges. One baboon received a control GalT-KO xenograft with the latter immunosuppression. All immunosuppressed baboons rejected the xenografts between days 9 and 15 with signs of acute humoral rejection, in contrast to untreated controls (n = 2) that lost their grafts on days 3 and 4. Immunofluorescence analyses showed deposition of IgM, C3, C5b-9 in rejected grafts, without C4d staining, indicating classical complement pathway blockade but alternate pathway activation. Moreover, rejected organs exhibited predominantly monocyte/macrophage infiltration with minimal lymphocyte representation. None of the recipients showed any signs of porcine endogenous retrovirus transmission but some showed evidence of porcine cytomegalovirus (PCMV) replication within the xenografts. Our work indicates that the addition of bortezomib and plasma exchange to the immunosuppressive regimen did not significantly prolong the survival of multi-transgenic GalT-KO renal xenografts. Non-Gal antibodies, the alternative complement pathway, innate mechanisms with monocyte activation and PCMV replication may have contributed to rejection.

Preclinical efficacy and immunological safety of FR104, an antagonist anti-CD28 monovalent Fab' antibody.

Antagonist anti-CD28 antibodies prevent T cell costimulation and differentiate from CTLA4Ig since they cannot block CTLA-4 and PDL-1 coinhibitory signals. They demonstrated efficacy in suppressing effector T cells while enhancing regulatory T cells function and immune tolerance. However, anti-CD28 antibodies devoid of immunotoxicity and with a good pharmacokinetic profile have not yet been developed. Here, we describe FR104, a novel humanized pegylated anti-CD28 Fab' antibody fragment presenting a long elimination half-life in monkeys. In vitro, FR104 failed to induce human T cell proliferation and cytokines secretion, even in the presence of anti-CD3 antibodies or when cross-linked with secondary antibodies. Furthermore, in humanized NOD/SCID mice adoptively transferred with human PBMC, whereas superagonist and divalent antibodies elicited rapid cytokines secretion and human T cell activation, FR104 did not. These humanized mice developed a florid graft-versus-host disease, which was prevented by administration of FR104 in a CTLA4-dependent manner. Interestingly, administration of high doses of CTLA4-Ig was ineffective to prevent GVHD, whereas administration of low doses was partially effective. In conclusion, we demonstrated that FR104 is devoid of agonist activity on human T cells and thus compatible with a clinical development that might lead to higher therapeutic indexes, by sparing CTLA-4, as compared to CD80/CD86 antagonists.

Antibody-mediated depletion of lymphocyte-activation gene-3 (LAG-3(+) )-activated T lymphocytes prevents delayed-type hypersensitivity in non-human primates.

Lymphocyte-activation gene-3 (LAG-3, CD223) is a marker for recently activated effector T cells. Activated T lymphocytes are of major importance in many autoimmune diseases and organ transplant rejection. Therefore, specifically depleting LAG-3(+) T cells might lead to targeted immunosuppression that would spare resting T cells while eliminating pathogenic activated T cells. We have shown previously that anti-LAG-3 antibodies sharing depleting as well as modulating activities inhibit heart allograft rejection in rats. Here, we have developed and characterized a cytotoxic LAG-3 chimeric antibody (chimeric A9H12), and evaluated its potential as a selective therapeutic depleting agent in a non-human primate model of delayed-type hypersensitivity (DTH). Chimeric A9H12 showed a high affinity to its antigen and depleted both cytomegalovirus (CMV)-activated CD4(+) and CD8(+) human T lymphocytes in vitro. In vivo, a single intravenous injection at either 1 or 0·1 mg/kg was sufficient to deplete LAG-3(+) -activated T cells in lymph nodes and to prevent the T helper type 1 (Th1)-driven skin inflammation in a tuberculin-induced DTH model in baboons. T lymphocyte and macrophage infiltration into the skin was also reduced. The in vivo effect was long-lasting, as several weeks to months were required after injection to restore a positive reaction after antigen challenge. Our data confirm that LAG-3 is a promising therapeutic target for depleting antibodies that might lead to higher therapeutic indexes compared to traditional immunosuppressive agents in autoimmune diseases and transplantation.

Tsetse elimination: its interest and feasibility in the historical sleeping sickness focus of Loos islands, Guinea.

Guinea is the West African country which is currently the most prevalent for sleeping sickness. The littoral area is the region where most of the recent sleeping sickness cases have been described, especially the mangrove sleeping sickness foci of Dubreka and Boffa where Glossina palpalis gambiensis is the vector. Loos islands constitute a small archipelago 5 km apart from the capital, Conakry. Medical, animal, and entomological surveys were implemented in these islands in Oct-Nov 2006. No pathogenic trypanosomes were found in these surveys. The locally very high tsetse densities (up to more than 100 tsetse/trap/day) linked to pig rearing, constitute a high potential risk for humans (taking into account populations movements with neighboring active sleeping sickness foci of the Guinea littoral, and the history of sleeping sickness on these islands), and for the economically important pig rearing, as well as a danger for tourism. This situation, associated to the possibility of elimination of these tsetse populations due to low possibility of reinvasion, led the National Control Program to launch a tsetse elimination project following an "area wide" strategy for the first time in West Africa, which participates in the global objective of the PATTEC (Pan African Tsetse and Trypanosomosis Eradication Campaign).

Effects of urbanization on transmission of human African trypanosomiasis in a suburban relict forest area of Daloa, Côte d'Ivoire.

The epidemiological risk of human African trypanosomiasis transmission was evaluated from entomological parameters (apparent trap density, female teneral rates, daily survival rates, proportion of human feeds) of tsetse (Glossina palpalis palpalis) populations in the town of Daloa, Côte d'Ivoire. High tsetse densities were found in the town outskirts, where the calculated risk of transmission was greatest. Environmental changes brought about by urbanization did not result in the disappearance of tsetse, or the interruption of sleeping sickness transmission. The few cases of sleeping sickness detected (32) in the years 1990-95 indicated that transmission was unrelated to tsetse density.

[Integration of demographic factors in the characterization of risk areas for sleeping sickness in Côte d'Ivoire]. / Intégration des facteurs démographiques à la caractérisation d'un espace à risque de maladie du sommeil en Côte d'Ivoire.

The purpose of this study was to classify the risk for transmission of African human trypanosomiasis (sleeping sickness) according to population and settlement densities in four different areas of Zoukougbeu, Cote d'Ivoire, where the exact location of cases reported since 1990 is known. Epidemiological risk indexes were calculated from entomological data obtained from three surveys and analyzed with respect to presence of patients and occupancy rate in each area. Results indicated that there was a risk of transmission near the village of Bahigbeu II where the population density is between 30 and 40 inhabitants per km2 and settlement density is 4 per km2. There was also a risk in less inhabited areas such as Ouatigbeu where the population density is less than 30 inhabitants per km2 and dwelling density less than 4 per km2. In fact, cases are regularly reported in Ouatigbeu but never in Bahigbeu II. Based on these findings, we conclude that, while land occupancy can be considered as a risk factor for sleeping sickness, other factors such as human mobility must be taken into account to characterize risk areas and predict outbreaks.

[Contribution to studies on the modern health care system in the Republic of Congo: geographical approach]. / Contribution aux études sur le système de soins modernes en République du Congo: approache géographique.

We carried out a geographic analysis of the modern health care system in the rural areas of Kouilou and Niari (Republic of Congo). Spatial differences in physical (e.g. vegetation, relief) and human (social and demographic profiles) factors must be characterized because they have an effect on the organization and spatial distribution of the health care system. The location of health care structures depended on the structure of the local environment. The health care system seemed primarily to be a component of the economic development determining population distribution in the forest area. In the savannah, it was part of the local administrative framework, the key factor determining the structure of the local space. Health care services were most used in areas with average to large population densities, in which there were the largest number of health care structures. Areas with "marginal" population densities and health care center distributions had the lowest rates of health care use. Health care zones can be defined by considering geographical characteristics and the characteristics of the health care system. This makes health planning (e.g. opening of health centers, improvement of health centers) much easier to undertake.

[Geographic approach to urinary schistosomiasis in an average African town, Daloa (Ivory Coast)]. / Approche géographique de la schistosomiase urinaire dans une ville moyenne africaine, Daloa (Côte d'Ivoire).

Agricultural activity occurs within many medium size towns in developing countries. Rural influences and urbanization, which may be well or poorly managed, combine to create new health problems. A geographical approach is useful for evaluating the ability of the health care system to deal efficiently with these problems. Such an approach should take into account the urban environment and human population, health care and spatial differentiation factors. Relevant health indicators were selected to analyze the geographical patterns of health risk and of the health care system. These factors were analyzed according to area, at various levels. Field studies were carried out and aerial photographs and the various available maps were also studied. Results were compared to determine whether the health care system was appropriate for the health needs of the town. Urinary schistosomiasis is a useful example for assessing the value of the suggested methodology. The risk of transmission of this disease is high so its early detection is vital. The ability of the health care system to detect infection was assessed.

Xenotransplantation of galactosyl-transferase knockout, CD55, CD59, CD39, and fucosyl-transferase transgenic pig kidneys into baboons.

Galactosyl-transferase knockout (GT-KO) pigs represent the latest major progress to reduce immune reactions in xenotransplantation. However, their organs are still subject to rapid humoral rejection involving complement activation requiring the ongoing development of further genetic modifications in the pig. In a pig-to-baboon renal transplantation setting, we have used donor pigs that are not only GT-KO, but also transgenic for human CD55 (hCD55), hCD59, hCD39, and fucosyl-transferase (hHT). We studied kidney xenograft survival, physiological and immunologic parameters, xenogeneic rejection characteristics, as well as viral transmission aspects among two groups of baboons: control animals (n = 2), versus those (n = 4) treated with a cocktail of cyclophosphamide, tacrolimus, mycophenolate mofetil, steroids, and a recombinant human C1 inhibitor. Whereas control animals showed clear acute humoral rejection at around day 4, the treated animals showed moderately improved graft survival with rejection at around 2 weeks posttransplantation. Biopsies showed signs of acute vascular rejection (interstitial hemorrhage, glomerular thrombi, and acute tubular necrosis) as well as immunoglobulin (Ig)M and complement deposition in the glomerular and peritubular capillaries. The low level of preformed non-Gal-α1.3Gal IgM detected prior to transplantation increased at 6 days posttransplantation, whereas induced IgG appeared after day 6. No porcine endogenous retrovirus (PERV) transmission was detected in any transplanted baboon. Thus, surprisingly, organs from the GT-KO, hCD55, hCD59, hCD39, and hHT transgenic donors did not appear to convey significant protection against baboon anti-pig antibodies and complement activation, which obviously continue to be significant factors under a suboptimal immunosuppression regimen. The association, timing, and doses of immunosuppressive drugs remain critical. They will have to be optimized to achieve longer graft survivals.

[Mobility in the Sahel, especially in the triangular frontier area covering parts of Mauritania, Senegal, and Mali]. / Mobilite sahelienne dans le triangle frontalier Mauritanie-Senegal-Mali

PIP: Migration trends in the frontier area of Mauritania, Senegal, and Mali are described. Data on migration in colonial times are used as an introduction to the study of more recent migration streams between the independent states of the region.^ieng

Impact of the development of agricultural land on the transmission of sleeping sickness in Daloa, Côte d'Ivoire.

Although tools to control sleeping sickness do exist, their use is difficult; areas where intervention is most required often cannot be targeted for lack of appropriate risk indicators. The importance of human behaviour and habits in the manifestation of the disease is clear. In the development of effective new approaches to the control of the disease, information must be gathered about human populations, and their interaction with the environment, in rural as well as in urban and peri-urban areas. The results of a study carried out in Daloa show that use of some methods for the development of agricultural land leads to increased human-vector contact and, as a result, increased risk of sleeping sickness. Such land-management methods may therefore be useful as risk indicators for transmission. Transmission does not occur in the town of Daloa itself but in surrounding areas under cultivation. The use of the epidemiological risk index seems to be inappropriate in urban (and perhaps peri-urban) areas. The results emphasise not only the importance of environmental and demographic data in elucidating the epidemiology of human trypanosomiasis but also the need for further investigations in peri-urban areas.