Hanna J. Laukaitis

Bio: Hanna J. Laukaitis is an academic researcher from University of South Alabama. The author has contributed to research in topics: Medicine & Ixodes scapularis. The author has an hindex of 1, co-authored 2 publications receiving 2 citations.

Dynamic gene expression in salivary glands of the cat flea during Rickettsia felis infection.

Abstract: The cat flea, Ctenocephalides felis, is an arthropod vector capable of transmitting several human pathogens including Rickettsia species. Earlier studies identified Rickettsia felis in the salivary glands of the cat flea and transmission of rickettsiae during arthropod feeding. The saliva of hematophagous insects contains multiple biomolecules with anticlotting, vasodilatory and immunomodulatory activities. Notably, the exact role of salivary factors in the molecular interaction between flea-borne rickettsiae and their insect host is still largely unknown. To determine if R. felis modulates gene expression in the cat flea salivary glands, cat fleas were infected with R. felis and transcription patterns of selected salivary gland-derived factors, including antimicrobial peptides and flea-specific antigens, were assessed. Salivary glands were microdissected from infected and control cat fleas at different time points after exposure and total RNA was extracted and subjected to reverse-transcriptase quantitative PCR for gene expression analysis. During the experimental 10-day feeding period, a dynamic change in gene expression of immunity-related transcripts and salivary antigens between the two experimental groups was detected. The data indicated that defensin-2 (Cf-726), glycine-rich antimicrobial peptide (Cf-83), salivary antigens (Cf-169 and Cf-65) and deorphanized peptide (Cf-75) are flea-derived factors responsive to rickettsial infection.

Croquemort elicits activation of the immune deficiency pathway in ticks.

Abstract: The immune deficiency (IMD) pathway directs host defense in arthropods upon bacterial infection. In Pancrustacea, peptidoglycan recognition proteins sense microbial moieties and initiate nuclear factor-κB-driven immune responses. Proteins that elicit the IMD pathway in non-insect arthropods remain elusive. Here, we show that an Ixodes scapularis homolog of croquemort (Crq), a CD36-like protein, promotes activation of the tick IMD pathway. Crq exhibits plasma membrane localization and binds the lipid agonist 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphoglycerol. Crq regulates the IMD and jun N-terminal kinase signaling cascades and limits the acquisition of the Lyme disease spirochete B. burgdorferi. Additionally, nymphs silenced for crq display impaired feeding and delayed molting to adulthood due to a deficiency in ecdysteroid synthesis. Collectively, we establish a distinct mechanism for arthropod immunity outside of insects and crustaceans.

Metabolic disruption impacts tick fitness and microbial relationships

Abstract: Arthropod-borne microbes rely on the metabolic state of a host to cycle between evolutionarily distant species. For instance, arthropod tolerance to infection may be due to redistribution of metabolic resources, often leading to microbial transmission to mammals. Conversely, metabolic alterations aids in pathogen elimination in humans, who do not ordinarily harbor arthropod-borne microbes. To ascertain the effect of metabolism on interspecies relationships, we engineered a system to evaluate glycolysis and oxidative phosphorylation in the tick Ixodes scapularis. Using a metabolic flux assay, we determined that the rickettsial bacterium Anaplasma phagocytophilum and the Lyme disease spirochete Borrelia burgdorferi, which are transstadially transmitted in nature, induced glycolysis in ticks. On the other hand, the endosymbiont Rickettsia buchneri, which is transovarially maintained, had a minimal effect on I. scapularis bioenergetics. Importantly, the metabolite β-aminoisobutyric acid (BAIBA) was elevated during A. phagocytophilum infection of tick cells following an unbiased metabolomics approach. Thus, we manipulated the expression of genes associated with the catabolism and anabolism of BAIBA in I. scapularis and detected impaired feeding on mammals, reduced bacterial acquisition, and decreased tick survival. Collectively, we reveal the importance of metabolism for tick-microbe relationships and unveil a valuable metabolite for I. scapularis fitness.

Mycobacterium leprae Infection in Ticks and Tick-Derived Cells.

Abstract: Leprosy is a zoonosis in the southern United States involving humans and wild armadillos. The majority of patients presenting with zoonotic strains of Mycobacterium leprae note extensive outdoor activity but only rarely report any history of direct contact with wild armadillos. Whether M. leprae is transmitted to new vertebrate hosts through the environment independently or with the aid of other organisms, e.g., arthropod vectors, is a fundamental question in leprosy transmission. The objectives of this study were to assess the potential for ticks to transmit M. leprae and to test if viable M. leprae can be maintained in tick-derived cells. To evaluate tick transmission, nymphal Amblyomma maculatum ticks were injected with isolated M. leprae. Infection and transmission were assessed by qPCR. Ticks infected as nymphs harbored M. leprae through vertical transmission events (nymph to adult and adult to progeny); and, horizontal transmission of M. leprae to a vertebrate host was observed. Mycobacterium leprae DNA was detected in multiple tick life cycle stages. Likewise, freshly isolated M. leprae (Thai-53) was used to infect a tick-derived cell line, and enumeration and bacterial viability were assessed at individual time points for up to 49 days. Evaluations of the viability of long-term cultured M. leprae (Thai-53 and Br4923) were also assessed in a mouse model. Tick-derived cells were able to maintain viable M. leprae over the 49-day course of infection and M. leprae remained infectious within tick cells for at least 300 days. The results of this study suggest that ticks themselves might serve as a vector for the transmission of M. leprae and that tick cells are suitable for maintenance of viable M. leprae for an extended period of time.

The role of cofeeding arthropods in the transmission of Rickettsia felis

Abstract: Rickettsia felis is an emerging etiological agent of rickettsioses worldwide. The cosmopolitan cat flea (Ctenocephalides felis) is the primary vector of R. felis, but R. felis has also been reported in other species of hematophagous arthropods including ticks and mosquitoes. Canines can serve as a bacteremic host to infect fleas under laboratory conditions, yet isolation of R. felis from the blood of a vertebrate host in nature has not been realized. Cofeeding transmission is an efficient mechanism for transmitting rickettsiae between infected and uninfected fleas; however, the mechanism of transmission among different orders and classes of arthropods is not known. The potential for R. felis transmission between infected fleas and tick (Dermacentor variabilis) and mosquito (Anopheles quadrimaculatus) hosts was examined via cofeeding bioassays. Donor cat fleas infected with R. felis transmitted the agent to naïve D. variabilis nymphs via cofeeding on a rat host. Subsequent transstadial transmission of R. felis from the engorged nymphs to the adult ticks was observed with reduced prevalence in adult ticks. Using an artificial host system, An. quadrimaculatus exposed to a R. felis-infected blood meal acquired rickettsiae and maintained infection over 12 days post-exposure (dpe). Similar to ticks, mosquitoes were able to acquire R. felis while cofeeding with infected cat fleas on rats infection persisting in the mosquito for up to 3 dpe. The results indicate R. felis-infected cat fleas can transmit rickettsiae to both ticks and mosquitoes via cofeeding on a vertebrate host, thus providing a potential avenue for the diversity of R. felis-infected arthropods in nature.

Using Proteomic Approaches to Unravel the Response of Ctenocephalides felis felis to Blood Feeding and Infection With Bartonella henselae

Abstract: Among the Ctenocephalides felis felis-borne pathogens, Bartonella henselae, the main aetiological agent of cat scratch disease (CSD), is of increasing comparative biomedical importance. Despite the importance of B. henselae as an emergent pathogen, prevention of the diseases caused by this agent in cats, dogs and humans mostly relies on the use of ectoparasiticides. A vaccine targeting both flea fitness and pathogen competence is an attractive choice requiring the identification of flea proteins/metabolites with a dual effect. Even though recent developments in vector and pathogen -omics have advanced the understanding of the genetic factors and molecular pathways involved at the tick-pathogen interface, leading to discovery of candidate protective antigens, only a few studies have focused on the interaction between fleas and flea-borne pathogens. Taking into account the period of time needed for B. henselae replication in flea digestive tract, the present study investigated flea-differentially abundant proteins (FDAP) in unfed fleas, fleas fed on uninfected cats, and fleas fed on B. henselae-infected cats at 24 hours and 9 days after the beginning of blood feeding. Proteomics approaches were designed and implemented to interrogate differentially expressed proteins, so as to gain a better understanding of proteomic changes associated with the initial B. henselae transmission period (24 hour timepoint) and a subsequent time point 9 days after blood ingestion and flea infection. As a result, serine proteases, ribosomal proteins, proteasome subunit α-type, juvenile hormone epoxide hydrolase 1, vitellogenin C, allantoinase, phosphoenolpyruvate carboxykinase, succinic semialdehyde dehydrogenase, glycinamide ribotide transformylase, secreted salivary acid phosphatase had high abundance in response of C. felis blood feeding and/or infection by B. henselae. In contrast, high abundance of serpin-1, arginine kinase, ribosomal proteins, peritrophin-like protein, and FS-H/FSI antigen family member 3 was strongly associated with unfed cat fleas. Findings from this study provide insights into proteomic response of cat fleas to B. henselae infected and uninfected blood meal, as well as C. felis response to invading B. henselae over an infection time course, thus helping understand the complex interactions between cat fleas and B. henselae at protein levels.

Pathogenicity and virulence of Rickettsia

Abstract: ABSTRACT Rickettsiae include diverse Gram-negative microbial species that exhibit obligatory intracellular lifecycles between mammalian hosts and arthropod vectors. Human infections with arthropod-borne Rickettsia continue to cause significant morbidity and mortality as recent environmental changes foster the proliferation of arthropod vectors and increased exposure to humans. However, the technical difficulties in working with Rickettsia have delayed our progress in understanding the molecular mechanisms involved in rickettsial pathogenesis and disease transmission. Recent advances in developing genetic tools for Rickettsia have enabled investigators to identify virulence genes, uncover molecular functions, and characterize host responses to rickettsial determinants. Therefore, continued efforts to determine virulence genes and their biological functions will help us understand the underlying mechanisms associated with arthropod-borne rickettsioses.