Clofazimine, a Promising Drug for the Treatment of Babesia microti Infection in Severely Immunocompromised Hosts

Comparison of the Efficacy of Longer versus Shorter Pulsed High Dose Dapsone Combination Therapy in the Treatment of Chronic Lyme Disease/Post Treatment Lyme Disease Syndrome with Bartonellosis and Associated Coinfections

Twenty-five patients with relapsing and remitting Borreliosis, Babesiosis, and bartonellosis despite extended anti-infective therapy were prescribed double-dose dapsone combination therapy (DDDCT), followed by one or several courses of High Dose Dapsone Combination Therapy (HDDCT). A retrospective chart review of these 25 patients undergoing DDDCT therapy and HDDCT demonstrated that 100% improved their tick-borne symptoms, and patients completing 6-7 day pulses of HDDCT had superior levels of improvement versus 4-day pulses if Bartonella was present. At the completion of treatment, 7/23 (30.5%) who completed 8 weeks of DDDCT followed by a 5-7 day pulse of HDDCT remained in remission for 3-9 months, and 3/23 patients (13%) who recently finished treatment were 1 ½ months in full remission. In conclusion, DDDCT followed by 6-7 day pulses of HDDCT could represent a novel, effective anti-infective strategy in chronic Lyme disease/Post Treatment Lyme Disease Syndrome (PTLDS) and associated co-infections, including Bartonella, especially in individuals who have failed standard antibiotic protocols.

Babesia microti Variant With Multiple Resistance Mutations Detected in an Immunocompromised Patient Receiving Atovaquone Prophylaxis

We report Babesia microti genomic sequences with multiple mutations in the atovaquone-target region of cytochrome b, including a newly identified Y272S mutation, plus 1 mutation of undetermined significance in the azithromycin-associated ribosomal protein L4. The parasite was sequenced from an immunocompromised patient on prophylactic atovaquone for Pneumocystis pneumonia before diagnosis of babesiosis.

Temporal metabolic profiling of erythrocytes in mice infected with Babesia microti

BACKGROUND

Babesiosis is an emerging zoonosis worldwide that is caused by tick-borne apicomplexans, Babesia spp., which threatens the health of domesticated and wild mammals and even humans. Although it has done serious harm to animal husbandry and public health, the study of Babesia is still progressing slowly. Until now, no effective anti-Babesia vaccines have been available, and administration of combined drugs tends to produce side effects. Therefore, non-targeted metabolomics was employed in the present study to examine the temporal dynamic changes in the metabolic profile of the infected erythrocytes. The goal was to obtain new insight into pathogenesis of Babesia and to explore vaccine candidates or novel drug targets.

METHODS

C57BL/6 mice were infected with B. microti and erythrocytes at different time points (0, 3, 6 , 9, 12, and 22-days post-infection) were subjected to parasitemia surveillance and then metabolomics analysis using liquid chromatography-mass spectrometry (LC-MS). Multivariate statistical analyses were performed to clearly separate and identify dysregulated metabolites in Babesia-infected mice. The analyses included principal components analysis (PCA) and orthogonal partial least squares-discrimination analysis (OPLS-DA). The time-series trends of the impacted molecules were analyzed using the R package Mfuzz and the fuzzy clustering principle. The temporal profiling of amino acids, lipids, and nucleotides in blood cells infected with B. microti were also investigated.

RESULTS

B. microti infection resulted in a fast increase of parasitemia and serious alteration of the mouse metabolites. Through LC-MS metabolomics analysis, 10,289 substance peaks were detected and annotated to 3,705 components during the analysis period. There were 1,166 dysregulated metabolites, which were classified into 8 clusters according to the temporal trends. Consistent with the trend of parasitemia, the numbers of differential metabolites reached a peak of 525 at 6-days post-infection (dpi). Moreover, the central carbon metabolism in cancer demonstrated the most serious change during the infection process except for that observed at 6 dpi. Sabotage occurred in components involved in the TCA cycle, amino acids, lipids, and nucleotide metabolism.

CONCLUSION

Our findings revealed a great alteration in the metabolites of Babesia-infected mice and shed new light on the pathogenesis of B. microti at the metabolic level. The results might lead to novel information about the mechanisms of pathopoiesis, babesisosis, and anti-parasite drug/vaccine development in the future.

A combination of clofazimine‒atovaquone as a potent therapeutic regimen for the radical cure of Babesia microti infection in immunocompromised hosts

Human babesiosis caused by Babesia microti can be fatal in immunocompromised patients, and the currently used drugs are often ineffective. A recent study found that clofazimine clears B. microti Munich strain in immunocompromised mice. In the present study, we investigated the efficacies of clofazimine and two-drug combinations involving clofazimine, atovaquone, and azithromycin against B. microti Peabody mjr strain in immunocompromised mice. Treatment with clofazimine alone, clofazimine plus azithromycin, and atovaquone plus azithromycin was ineffective and failed to eliminate the parasites completely, while a 44-day treatment with clofazimine plus atovaquone was highly effective and resulted in a radical cure.

Treatment of Human Babesiosis: Then and Now

Babesiosis is an emerging tick-borne disease caused by apicomplexan parasites of the genus Babesia. With its increasing incidence worldwide and the risk of human-to-human transmission through blood transfusion, babesiosis is becoming a rising public health concern. The current arsenal for the treatment of human babesiosis is limited and consists of combinations of atovaquone and azithromycin or clindamycin and quinine. These combination therapies were not designed based on biological criteria unique to Babesia parasites, but were rather repurposed based on their well-established efficacy against other apicomplexan parasites. However, these compounds are associated with mild or severe adverse events and a rapid emergence of drug resistance, thus highlighting the need for new therapeutic strategies that are specifically tailored to Babesia parasites. Herein, we review ongoing babesiosis therapeutic and management strategies and their limitations, and further review current efforts to develop new, effective, and safer therapies for the treatment of this disease.

Tafenoquine Is a Promising Drug Candidate for the Treatment of Babesiosis

Due to drug resistance, commonly used anti-Babesia drugs have limited efficacy against babesiosis and inflict severe side effects. Tafenoquine (TAF) was approved by the U.S. Food and Drug Administration in 2018 for the radical cure of Plasmodium vivax infection and for malaria prophylaxis. Here, we evaluated the efficacy of TAF for the treatment of Babesia infection and elucidated the suspected mechanisms of TAF activity against Babesia parasites. Parasitemia and survival rates of Babesia rodhaini-infected BALB/c and SCID mice were used to explore the role of the immune response in Babesia infection after TAF treatment. Parasitemia, survival rates, body weight, vital signs, complete blood count, and blood biochemistry of B. gibsoni-infected splenectomized dogs were determined to evaluate the anti-Babesia activity and side effects of TAF. Then, to understand the mechanism of TAF activity, hydrogen peroxide was used as an oxidizer for short-term B. rodhaini incubation in vitro, and the expression levels of antioxidant enzymes were confirmed using B. microti-infected mice by reverse transcription-quantitative PCR (qRT-PCR). Acute B. rodhaini and B. gibsoni infections were rapidly eliminated with TAF administration. Repeated administration of TAF or a combination therapy with other antibabesial agents is still needed to avoid a potentially fatal recurrence for immunocompromised hosts. Caution about hyperkalemia should be taken during TAF treatment for Babesia infection. TAF possesses a babesicidal effect that may be related to drug-induced oxidative stress. Considering the lower frequency of glucose-6-phosphate dehydrogenase deficiency in animals compared to that in humans, TAF use on Babesia-infected farm animals and pets is eagerly anticipated.

Cytochrome b Drug Resistance Mutation Decreases Babesia Fitness in the Tick Stages But Not the Mammalian Erythrocytic Cycle

Human babesiosis is an emerging tick-borne malaria-like illness caused by Babesia parasites following their development in erythrocytes. Here, we show that a mutation in the Babesia microti mitochondrial cytochrome b (Cytb) that confers resistance to the antibabesial drug ELQ-502 decreases parasite fitness in the arthropod vector. Interestingly, whereas the mutant allele does not affect B. microti fitness during the mammalian blood phase of the parasite life cycle and is genetically stable as parasite burden increases, ELQ-502-resistant mutant parasites developing in the tick vector are genetically unstable with a high rate of the wild-type allele emerging during the nymphal stage. Furthermore, we show that B. microti parasites with this mutation are transmitted from the tick to the host, raising the possibility that the frequency of Cytb resistance mutations may be decreased by passage through the tick vector, but could persist in the environment if present when ticks feed.

Case Report: Overwhelming Babesia Parasitemia Successfully Treated Promptly With RBC Apheresis and Triple Therapy With Clindamycin, Azithromycin, and Atovaquone

Babesiosis with high-grade parasitemia is life-threatening, especially in asplenic hosts. We report an asplenic patient with parasitemia >50% who was successfully treated with prompt red blood cell apheresis and triple therapy with clindamycin + azithromycin + atovaquone. This regimen may be an alternative to poorly tolerated clindamycin + quinine in severe cases.

Vector-borne diseases in pregnancy

Vector-borne infections cause a significant proportion of world-wide morbidity and mortality and many are increasing in incidence. This is due to a combination of factors, primarily environmental change, encroachment of human habitats from urban to peri-urban areas and rural to previously uninhabited areas, persistence of poverty, malnutrition and resource limitation in geographical areas where these diseases are endemic. Pregnant women represent the single largest ‘at risk’ group, due to immune-modulation and a unique physiological state. Many of these diseases have not benefitted from the same level of drug development as other infectious and medical domains, a factor attributing to the ‘neglected tropical disease’ title many vector-borne diseases hold. Pregnancy compounds this issue as data for safety and efficacy for many drugs is practically non-existent, precluding exposure in pregnancy to many first-line therapeutic agents for ‘fear of the unknown’ or overstated adverse pregnancy-foetal outcomes. In this review, major vector-borne diseases, their impact on pregnancy outcomes, current treatment, vaccination and short-comings of current medical practice for pregnant women will be discussed.

Activities of artesunate-based combinations and tafenoquine against Babesia bovis in vitro and Babesia microti in vivo

BACKGROUND

Babesiosis represents a veterinary and medical threat, with a need for novel drugs. Artemisinin-based combination therapies (ACT) have been successfully implemented for malaria, a human disease caused by related parasites, Plasmodium spp. The aim of this study was to investigate whether ACT is active against Babesia in vitro and in vivo.

METHODS

Mefloquine, tafenoquine, primaquine, methylene blue and lumefantrine, alone or in combination with artesunate, were tested in vitro against Babesia bovis. Parasite growth was verified using a SYBR green I-based fluorescence assay. Mice infected with Babesia microti were treated with mefloquine or tafenoquine, alone or in combination with artesunate, and parasitemia was verified by microscopy and PCR.

RESULTS

All drugs, except lumefantrine, showed in vitro activity against B. bovis, with methylene blue showing the most potent activity (concentration 0.2 μM). Combination with artesunate led to improved activity, with mefloquine showing a striking 20-fold increase in activity. Tafenoquine (10 mg/kg, base), combined or not with artesunate, but not mefloquine, induced rapid clearance of B. microti in vivo by microscopy, but mice remained PCR-positive. Blood from mice treated with tafenoquine alone, but not with tafenoquine-artesunate, was infective for naive mice upon sub-inoculation.

CONCLUSIONS

Tafenoquine, and most likely other 8-aminoquinoline compounds, are promising compounds for the development of ACT for babesiosis.