Many studies have revealed the ability of the endosymbiotic bacterium Wolbachia to protect its arthropod hosts against diverse pathogens. However, as Wolbachia may also increase the susceptibility of its host to infection, predicting the outcome of a particular Wolbachia-host-pathogen interaction remains elusive. Yet, understanding such interactions and their eco-evolutionary consequences is crucial for disease and pest control strategies. Moreover, how natural Wolbachia infections affect artificially introduced pathogens for biocontrol has never been studied. Tetranychus urticae spider mites are herbivorous crop pests, causing severe damage on numerous economically important crops. Due to the rapid evolution of pesticide resistance, biological control strategies using entomopathogenic fungi are being developed. However, although spider mites are infected with various Wolbachia strains worldwide, whether this endosymbiont protects them from fungi is as yet unknown. Here, we compared the survival of two populations, treated with antibiotics or naturally harboring different Wolbachia strains, after exposure to the fungal biocontrol agents Metarhizium brunneum and Beauveria bassiana. To control for potential effects of the bacterial community of spider mites, we also compared the susceptibility of two populations naturally uninfected by Wolbachia, treated with antibiotics or not. In one population, Wolbachia-infected mites had a better survival than uninfected ones in absence of fungi but not in their presence, whereas in the other population Wolbachia increased the mortality induced by B. bassiana. In one naturally Wolbachia-uninfected population, the antibiotic treatment increased the susceptibility of spider mites to M. brunneum, but it had no effect in the other treatments. These results suggest that natural Wolbachia infections may not hamper and may even improve the success of biological control using entomopathogenic fungi. However, they also draw caution on the generalization of such effects, given the complexity of within-host-pathogens interaction and the potential eco-evolutionary consequences of the use of biocontrol agents for Wolbachia-host associations. | 3869ZÉLÉ et aL.

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Despite the control measures implemented all over the world, Coronavirus Disease 2019 (COVID-19) continues to spread. [1] According to the data of the World Health Organization (WHO) dated 14 August 2021, 205.338.159 cases and 4.333.094 deaths were reported, and 4.428.168.759 doses of vaccine were administered. [2] COVID-19 causes humoral immune response and antibody production against specific viral antigens such as N protein and S protein. [3] Since the beginning of the outbreak, more than 198 vaccines developed or in clinical development for COVID-19 have been reported. [4] Objective: Antibodies against the S protein are used to investigate post-vaccine and post-infection immunity. In this study, it was aimed to determine the antibody levels and the efficacy of the vaccine after the CoronaVac vaccine in healthcare workers.Methods: Data from 96 healthcare workers who had the CoronaVac vaccine were analyzed. From the first dose, monthly antibody measurements were made over a 5-months period with an interval of 28 days between two vaccine doses. Total antibodies (IgM and IgG) against SARS-CoV-2 were detected by the Electrochemiluminescence method using the Elecsys ® Anti-SARS-CoV-2 S kit, which contains recombinant protein representing the receptor-binding site of the S1 antigen.Results: 51% (n=49) of the volunteers aged 22-69 (39.75±11.19) were female. The mean antibody concentration was 8.93 U/mL one month after the first vaccine dose, 171.30 IU/ mL one month after the second vaccine dose, 125.90 IU/mL two months after the second dose, 98.57 IU three months later, and 89.85 IU/mL after four months. Increase in antibody levels in the first and second months; The decreases in antibody levels in the in the following months were statistically significant. The proportion of subjects with antibody positivity ≥0.8 IU/mL and developing neutralizing antibodies (≥15 IU/mL) was 68.75% and 5.21% after the first dose of vaccination. The rate of individuals developing neutralizing antibodies were 100%, 93.8%, 91.7%, and 89.6% with regard to the months after the second dose of vaccination. One person had SARS-CoV-2 D3L-containing variant (UK variant) PCR positivity 9 weeks after the second vaccine dose. Conclusion:In the long-term follow-up, the neutralizing antibody level was found to be significantly higher even at the end of the 5th month, indicating that the vaccine is protective. The decrease in post-vaccination antibody concentrations and the emergence of new SARS-COV-2 variants suggest that a booster dose may be beneficial.

Spider mites are severe pests of several annual and perennial crops worldwide, often causing important economic damages. As rapid evolution of pesticide resistance in this group hampers the efficiency of chemical control, alternative control strategies, such as the use of entomopathogenic fungi, are being developed. However, while several studies have focused on the evaluation of the control potential of different fungal species and/or isolates as well as their compatibility with other control methods (e.g., predators or chemical pesticides), knowledge on the extent of inter‐ and intraspecific variation in spider mite susceptibility to fungal infection is as yet incipient. Here, we measured the mortality induced by two generalist fungi, Beauveria bassiana and Metarhizium brunneum, in 12 spider mite populations belonging to different Tetranychus species: T. evansi, T. ludeni, and T. urticae (green and red form), within a full factorial experiment. We found that spider mite species differed in their susceptibility to infection by both fungal species. Moreover, we also found important intraspecific variation for this trait. These results draw caution on the development of single strains as biocontrol agents. Indeed, the high level of intraspecific variation suggests that (a) the one‐size‐fits‐all strategy may fail to control spider mite populations and (b) hosts resistance to infection may evolve at a rapid pace. Finally, we propose future directions to better understand this system and improve the long‐term success of spider mite control strategies based on entomopathogenic fungi.

Many studies have revealed the ability of the endosymbiotic bacteria Wolbachia to protect its arthropod hosts against diverse pathogens. However, as Wolbachia may also increase the susceptibility of its host to infection, predicting the outcome of a particular Wolbachia-host-pathogen interaction remains elusive. Yet, understanding such interactions is crucial for disease and pest control strategies. Tetranychus urticae spider mites are herbivorous crop pests, causing severe damage on numerous economically important crops. Due to the rapid evolution of pesticide resistance, biological control strategies using generalist entomopathogenic are being developed. However, although spider mites are infected with various Wolbachia strains worldwide, whether this endosymbiont protects them from fungi is as yet unknown. Here, we compared the survival of two populations, treated with antibiotics or harbouring different Wolbachia strains, after exposure to the fungal biocontrol agents Metarhizium brunneum and Beauveria bassiana. In one population, Wolbachia affected survival in absence of fungi but not in their presence, whereas in the other population Wolbachia increased the mortality induced by B. bassiana. To control for potential effects of the bacterial community of spider mites, we also compared the susceptibility of two populations naturally uninfected by Wolbachia, treated with antibiotics or not. The antibiotic treatment increased the susceptibility of spider mites to M. brunneum in one naturally Wolbachia-uninfected population, but it had no effect in the other treatments.These results highlight the complexity of within-host pathogens interactions, and the importance of considering the whole bacterial community of arthropods when assessing the effect of Wolbachia in a particular system. KEY-WORDSTetranychus urticae; entomopathogenic fungi; parasite-induced mortality; endosymbionts; bacterial community; antibiotic treatment.