Tick-borne rickettsioses are considered important emerging zoonoses worldwide, but their etiological agents, rickettsiae, remain poorly characterized in northeastern China, where many human cases have been reported during the past several years. Here, we determined the characteristics of Rickettsia spp. infections in ticks in this area. Ticks were collected by flagging vegetation from Jilin and Heilongjiang provinces of northeastern China followed by morphological identification. The presence of Rickettsia spp. in ticks was detected by PCR targeting the 23S-5S ribosomal RNA intergenic spacer, citrate synthase (gltA) gene, and 190-kDa outer membrane protein gene (ompA). The newly-generated sequences were subjected to phylogenetic analysis using the software MEGA 6.0. The overall infection rate of Rickettsia spp. was 6.12 %. Phylogenetic analyses based on the partial gltA and ompA genes demonstrated that rickettsiae detected in the ticks belong to four species, including “Candidatus Rickettsia tarasevichiae”, Rickettsia heilongjiangensis, Rickettsia raoultii, and a potential new species isolate. The associated tick species were also identified, i.e. Dermacentor nuttalli and Dermacentor silvarum for R. raoultii, Haemaphysalis concinna and Haemaphysalis longicornis for R. heilongjiangensis, and Ixodes persulcatus for “Ca. R. tarasevichiae”. All Rickettsia spp. showed significantly high infection rates in ticks from Heilongjiang when compared to Jilin Province. Rickettsia heilongjiangensis, R. raoultii and “Ca. R. tarasevichiae” are widely present in the associated ticks in northeastern China, but more prevalent in Heilongjiang Province. The data of this study increase the information on the distribution of Rickettsia spp. in northeastern China, which have important public health implications in consideration of their recent association with human diseases.

Trichinella infection can induce macrophages into the alternatively activated phenotype, which is primarily associated with the development of a polarized Th2 immune response. In the present study, we examined the immunomodulatory effect of T. spiralis thioredoxin peroxidase-2 (TsTPX2), a protein derived from T. spiralis ES products, in the regulation of Th2 response through direct activation of macrophages. The location of TsTPX2 was detected by immunohistochemistry and immunofluorescence analyses. The immune response in vivo induced by rTsTPX2 was characterized by analyzing the Th2 cytokines and Th1 cytokines in the peripheral blood. The rTsTPX2-activated macrophages (M_rTsTPX2) were tested for polarization, their ability to evoke naïve CD4⁺ T cells, and resistance to the larval infection after adoptive transfer in BALB/c mice. The immunolocalization analysis showed TsTPX2 in cuticles and stichosome of T. spiralis ML. The immunostaining was detected in cuticles and stichosome of T. spiralis Ad3 and ML, as well as in tissue-dwellings around ML after the intestines and muscle tissues of infected mice were incubated with anti-rTsTPX2 antibody. Immunization of BALB/c mice with rTsTPX2 could induce a Th1-suppressing mixed immune response given the increased levels of Th2 cytokines (IL-4 and IL-10) production along with the decreased levels of Th1 cytokines (IFN-γ, IL-12, and TNF-α). In vitro studies showed that rTsTPX2 could directly drive RAW264.7 and peritoneal macrophages to the M2 phenotype. Moreover, M_rTsTPX2 could promote CD4⁺ T cells polarized into Th2 type in vitro. Adoptive transfer of M_rTsTPX2 into mice suppressed Th1 responses by enhancing Th2 responses and exhibited a 44.7% reduction in adult worm burden following challenge with T. spiralis infective larval, suggesting that the TsTPX2 is a potential vaccine candidate against trichinosis. Our study showed that TsTPX2 would be at least one of the molecules to switch macrophages into the M2 phenotype during T. spiralis infection, which provides a new therapeutic approach to various inflammatory disorders like allergies or autoimmune diseases.

In the last decade, the emergence of QYYZ-like porcine reproductive and respiratory syndrome virus (PRRSV) has attracted increasing attention due to the high incidence of PRRSV mutation and recombination. However, the endemic status and genomic characteristics of the QYYZ-like strains are unclear. From 2018 to October 2021, 24 QYYZ-like PRRSV isolates were obtained from 787 PRRSV-positive clinical samples. Only one QYYZ-like positive sample was from a northern province, and the rest were from central and southern provinces. We selected 9 samples for whole-genome sequencing, revealing genome lengths of 15,008–15,316 nt. We retrieved all the available whole-genome sequences of QYYZ-like PRRSVs isolated in China from 2010 to 2021 (n = 28) from GenBank and analyzed them together with the new whole-genome sequences (n = 9). Phylogenetic tree analysis based on the ORF5 gene showed that all QYYZ-like PRRSV strains belonged to sublineage 3.5 but were clustered into three lineages (sublineage 1.8, sublineage 3.5, and sublineage 8.7) based on whole-genome sequences. Genomic sequence alignment showed that QYYZ-like strains, have characteristic amino acids insertions or deletions in the Nsp2 region (same as NADC30, JXA1 and QYYZ) and that thirteen strains also had additional amino acid deletions, mostly between 468 and 518 aa. Moreover, QYYZ-like strains (sublineage 3.5) have seven identical characteristic amino acid mutations in ORF5. Recombination analysis revealed that almost all QYYZ-like complete genome sequences (36/37) were products of recombination and mainly provided structural protein fragments (GP2-N) for the recombinant strains. Overall, QYYZ-like strains were mainly prevalent in central and southern China from 2018 to 2021, and these strains provided recombinant fragments in the PRRSV epidemic in China.