Nasir, G. | bioRxiv Science

bioRxiv2022

Transport of Antibody into the Skin is Only Partially Dependent Upon the Neonatal Fc-Receptor

The dermis is the portal of entry for most vector-transmitted pathogens, making the hosts immune response at this site critical in mitigating the magnitude of infection. For malaria, antibody-mediated neutralization of Plasmodium parasites in the dermis was recently demonstrated. However, surprisingly little is known about the mechanisms that govern antibody transport into the skin. Since the neonatal Fc receptor (FcRn) has been shown to transcytose IgG into various tissues, we sought to understand its contribution to IgG transport and antibody-mediated inhibition of Plasmodium parasites following mosquito bite inoculation. Using confocal imaging, we show that the transport of an anti-Langerin mAb into the skin is only partially reduced in mice lacking FcRn. To understand the relevance of FcRn in the context of malaria infection, we use the rodent parasite Plasmodium berghei and show that the protective efficacy of a passively-administered anti-malarial antibody is reduced in the skin in FcRn deficient mice, but not to the same extent that we have previously observed in wildtype mice. Overall, our data suggest that FcRn plays a role in the transport of IgG into the skin but is not the major driver of IgG transport into this tissue. These findings have implications for the rational design of antibody-based therapeutics for malaria as well as other vector-transmitted pathogens.

immunology↗

bioRxiv2019

Experimental Determination of the Force of Malaria Infection Reveals a Non-Linear Relationship to Mosquito Sporozoite Loads

Plasmodium sporozoites are the infective stage of the malaria parasite. Though this is a bottleneck for the parasite, the quantitative dynamics of transmission, from mosquito inoculation of sporozoites to patent blood-stage infection in the mammalian host, are poorly understood. Here we utilize a rodent model to determine the probability of malaria infection after infectious mosquito bite, and consider the impact of mosquito parasite load, blood-meal acquisition, probe-time, and probe location, on infection probability. We found that infection likelihood correlates with mosquito sporozoite load and, to a lesser degree, the duration of probing, and is not dependent upon the mosquitos ability to find blood. The relationship between sporozoite load and infection probability is non-linear and can be described by a set of models that include a threshold, with mosquitoes harboring over 10,000 salivary gland sporozoites being 7.5 times more likely to initiate a malaria infection. Overall, our data suggest that the small subset of highly infected mosquitoes may contribute disproportionally to malaria transmission in the field and that quantifying mosquito sporozoite loads could aid in predicting the force of infection in different transmission settings.\n\nAuthor SummaryMalaria is a leading cause of death in many parts of the world. Infection is initiated when infected Anopheles mosquitoes inject sporozoites as they look for blood. Though transmission is a bottleneck for the parasite and thus a good point for intervention, many aspects of transmission remain poorly understood. In this study, using a rodent model of malaria, we found that less than 20% of infectious bites result in disease, demonstrating that the majority of infective bites do not result in malaria infection. Furthermore, we found that the bites of mosquitoes with heavy parasite burdens are 7.5 times more likely to result in disease. These data have important implications for designing interventions targeting transmission stages of the malaria parasite as they suggest that reducing parasite loads, even without completely eliminating them, could be effective against disease spread. We also found that mosquitoes that probe but do not succeed in finding blood are equally likely to initiate infection, an important finding for human vaccine trials. Together, this work adds to our understanding of malaria transmission dynamics and our capacity to develop malaria elimination strategies.

microbiology↗