Frequent vaccination and immune complex deposition in unilateral nephrectomized mice

Assessment of Circulating Immune Complexes During Natural and Experimental Canine Leishmaniasis

Canine leishmaniasis (CanL) is a disease characterized by a large variety of clinical alterations, the majority of which being due to immune mediated mechanisms. Sick dogs usually produce high levels of Leishmania-specific immunoglobulins which may give rise to circulating immune complexes (CICs) whose defective clearance by scavenging macrophages induces vasculitis and their deposition in specific organs. The aim of this study was to assess the serum level of CICs in dogs exposed to natural and experimental infection. Fifty-two sera were examined, belonging to untreated groups of naïve beagles previously studied to assess the performance of anti-leishmanial vaccines under natural (no. 22 dogs) or experimental (no. 30 dogs) transmission. Sera were classified in five groups according to the dog's health condition, IFAT titer, and the bone marrow (BM) nested (n)-PCR result. A: no.10 healthy dogs before the experimental infection; B: no.10 clinically healthy dogs infected experimentally, IFAT negative (= reciprocal titer <160) and n-PCR positive; C: no.10 clinically healthy dogs naturally infected, IFAT positive at titers 160-320 and n-PCR negative; D: no.10 sick dogs experimentally infected, IFAT positive at titer >320 and n-PCR positive; E: no.12 sick dogs naturally infected, IFAT positive at titer >320 and n-PCR positive. CICs levels were assessed by ELISA method (canine CIC assay-Cloude-Clone Corporation, USA). The two groups characterized by negative IFAT (A and B) had the lowest median level of CICs (16.09 and 12.78 μg/ml, respectively). CICs value increased progressively in the group C and reached the highest levels in the groups D and E, both characterized by high antibodies titer and severe disease, independently from the mode of infection. Significant differences in CICs concentration (p < 0.0001) were demonstrated between A, B, and C groups when compared with D or E groups of dogs. No differences were found inside the first three groups, while differences were recorded between the last two groups of sick dogs. CICs serum concentration increased with the progress of leishmaniasis, being significantly correlated with the increase of specific antibodies over time. High CICs levels detectable by commercial ELISA proved specific to an established Leishmania infection in dogs in the absence of other concomitant infections, as demonstrated by the similar trend assessed in experimentally and naturally infected dogs.

Safety and biocompatibility of injectable vaccine adjuvants composed of thermogelling block copolymer gels

Injectable thermogelling polymers have been recently investigated as novel adjuvants and delivery systems for next generation vaccines. As research into natural and synthetic biocompatible polymers progresses, the safety and biocompatibility of these compounds is of paramount importance. We have developed cationic pentablock copolymer (PBC) vaccine adjuvants based on Pluronic F127, a thermogelling triblock copolymer that has been approved by the FDA for multiple applications, and methacrylated poly(diethyl amino)ethyl methacrylate outer blocks. These novel materials have been demonstrated to effectively create an antigen depot, minimally impact antigen stability, and enhance the immune response to antigens (i.e., adjuvanticity) in mice. In this work, we investigated the safety and biocompatibility of the parent triblock Pluronic gels and the cationic PBC gels in mice. Histological analysis showed no injection site reactions and no damage to the liver or kidneys was observed upon administering the block copolymer formulations. However, the subcutaneous injection of a thermogelling Pluronic solution induced increased levels of lipids in the blood, with no further deleterious effects observed from the addition of the cationic outer blocks. This hyperlipidemia resolved within 30 days after the administration of the Pluronic formulation. To mitigate this adverse effect, the vaccine adjuvant formulations were modified by adding poly(vinyl alcohol), which allowed gelation, while reducing the amount of Pluronic in the formulation. This modified formulation abrogated the observed hyperlipidemia and no adverse effects were observed in the serum through biomarker analysis or at the injection site (i.e., inflammation) in comparison to the responses induced by administration of saline or incomplete Freund's adjuvant. These studies provide a foundation to developing these gels as adjuvants for next generation vaccines. © 2019 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 107A: 1754-1762, 2019.

Histopathological observation of immunized rhesus macaques with plague vaccines after subcutaneous infection of Yersinia pestis

In our previous study, complete protection was observed in Chinese-origin rhesus macaques immunized with SV1 (20 µg F1 and 10 µg rV270) and SV2 (200 µg F1 and 100 µg rV270) subunit vaccines and with EV76 live attenuated vaccine against subcutaneous challenge with 6×10(6) CFU of Y. pestis. In the present study, we investigated whether the vaccines can effectively protect immunized animals from any pathologic changes using histological and immunohistochemical techniques. In addition, the glomerular basement membranes (GBMs) of the immunized animals and control animals were checked by electron microscopy. The results show no signs of histopathological lesions in the lungs, livers, kidneys, lymph nodes, spleens and hearts of the immunized animals at Day 14 after the challenge, whereas pathological alterations were seen in the corresponding tissues of the control animals. Giemsa staining, ultrastructural examination, and immunohistochemical staining revealed bacteria in some of the organs of the control animals, whereas no bacterium was observed among the immunized animals. Ultrastructural observation revealed that no glomerular immune deposits on the GBM. These observations suggest that the vaccines can effectively protect animals from any pathologic changes and eliminate Y. pestis from the immunized animals. The control animals died from multi-organ lesions specifically caused by the Y. pestis infection. We also found that subcutaneous infection of animals with Y. pestis results in bubonic plague, followed by pneumonic and septicemic plagues. The histopathologic features of plague in rhesus macaques closely resemble those of rodent and human plagues. Thus, Chinese-origin rhesus macaques serve as useful models in studying Y. pestis pathogenesis, host response and the efficacy of new medical countermeasures against plague.