Adoptive Transfer of Immune Cells Into RAG2IL-2Rγ-Deficient Mice During Litomosoides sigmodontis Infection: A Novel Approach to Investigate Filarial-Specific Immune Responses

Abstract

Despite long-term mass drug administration programmes, approximately 220 million people are still infected with filariae in endemic regions. Several research studies have characterized host immune responses but a major obstacle for research on human filariae has been the inability to obtain adult worms which in turn has hindered analysis on infection kinetics and immune signalling. Although the Litomosoides sigmodontis filarial mouse model is well-established, the complex immunological mechanisms associated with filarial control and disease progression remain unclear and translation to human infections is difficult, especially since human filarial infections in rodents are limited. To overcome these obstacles, we performed adoptive immune cell transfer experiments into RAG2IL-2Rγ-deficient C57BL/6 mice. These mice lack T, B and natural killer cells and are susceptible to infection with the human filaria Loa loa. In this study, we revealed a long-term release of L. sigmodontis offspring (microfilariae) in RAG2IL-2Rγ-deficient C57BL/6 mice, which contrasts to C57BL/6 mice which normally eliminate the parasites before patency. We further showed that CD4+ T cells isolated from acute L. sigmodontis-infected C57BL/6 donor mice or mice that already cleared the infection were able to eliminate the parasite and prevent inflammation at the site of infection. In addition, the clearance of the parasites was associated with Th17 polarization of the CD4+ T cells. Consequently, adoptive transfer of immune cell subsets into RAG2IL-2Rγ-deficient C57BL/6 mice will provide an optimal platform to decipher characteristics of distinct immune cells that are crucial for the immunity against rodent and human filarial infections and moreover, might be useful for preclinical research, especially about the efficacy of macrofilaricidal drugs.

ILC2s Control Microfilaremia During Litomosoides sigmodontis Infection in Rag2-/- Mice

“…A similar increased susceptibility to L. sigmodontis infection was described for Rag2IL-2Rγ -/- C57BL/6 mice, which additionally lack NK cells and importantly ILC2s ( 9 ). Thus, the adaptive immune system is a crucial part for the elimination of L. sigmodontis in C57BL/6 mice with CD4 + T cells being important mediators, as shown by previous studies with L. sigmodontis ( 36 – 38 ). Additional specific depletion of ILC2s in L. sigmodontis -infected Rag2 -/- mice did not increase the recovery of adult worms at 63dpi, but significantly enhanced the microfilarial load in the peripheral blood compared to the isotype controls.…”

Comparative development of human filariae Loa loa, Onchocerca volvulus and Mansonella perstans in immunocompromised mouse strains

“…Therefore, we aim to establish a murine model of M. perstans based on the knowledge of the established animal models of onchocerciasis, lymphatic filariasis and loiasis. Immunocompromised mouse strains that lack adaptive immunity pathways like RAG2 −/− ( 27 , 28 ), IL-4/5 −/− ( 32 ) and NSG strains ( 26 , 36 ) have been proven suitable for human filarial infections and recently, NSG mice have been also proven to be susceptible to infection with the dog heartworm Dirofilaria immits ( 47 , 48 ). Indeed, a 62-66% L3 recovery rate could be obtained upon Loa loa L3 inoculation, whereas M. perstans and O. volvulus L3 were absent in all immunocompromised mouse strains.…”

“…Thus, in vivo rodent models for Loa loa and O. volvulus have been established using immunocompromised rodents ( 26 – 30 ), whereas no in vivo model for M. perstans has been implemented until now. Since RAG2- ( 27 , 28 , 31 , 32 ) and IL-4/5-deficient ( 33 – 35 ), as well as NOD scid gamma mouse (NSG) strains ( 26 , 36 ), have been proven to enhance susceptibility to filarial infections, we elucidate if M. perstans infections can be maintained in these mouse strains in comparison to Loa loa and O. volvulus infection.…”

A dirofilariasis mouse model for heartworm preclinical research

“…For instance, NOD mice are deficient in complement humoral immunity due to a 2-bp deletion in the hemolytic complement (Hc) gene, which encodes the C5 complement protein [45]. Our model now affords an opportunity for reconstitution of innate or adaptive immune cell types and humoral immune components to dissect the mechanisms of immunity to D. immitis migrating larvae, as has recently been attempted for L. sigmodontis with CD4+ T cell transfers into RAG2 -/-c -/mice [46]. This application of the model may be useful in determining minimally sufficient immune pathways necessary to mediate sterilising immunity.…”