Plasmodium vivax merozoite surface protein-1 (PvMSP-1) is one of the major polymorphic markers for molecular epidemiological purposes. In particular, the interspecies conserved block 5–6 (ICB 5–6) of PvMSP-1 is a region exhibiting extensive genetic polymorphism. In this study, we analyzed polymorphic characters of the pvmsp-1 ICB 5–6 region from P. vivax isolates collected in 4 provinces of Vietnam (Dak Lak, Dak Nong, Gia Lai, and Khanh Hoa) between 2018 and 2022. A comparative analysis of pvmsp-1 ICB 5–6 sequences was also conducted between Vietnam and other endemic regions. A total of 139 pvmsp-1 ICB 5–6 sequences were obtained from 117 Vietnamese P. vivax isolates. Vietnam pvmsp-1 ICB 5–6 were clustered into 34 distinct haplotypes at the amino acid level, with the recombinant types being predominant. The pvmsp-1 ICB 5–6 from the Central Highlands, Dak Lak, Dak Nong, and Gia Lai, exhibited high genetic polymorphism, while the sequences from the South-Central region, Khanh Hoa, were less polymorphic. Highly diverse patterns of poly-glutamine (poly-Q) variants were identified in Vietnam pvmsp-1 ICB 5–6. Comparable features of genetic polymorphism were also identified in the global pvmsp-1 ICB 5–6 populations. Phylogenetic analysis of global pvmsp-1 ICB 5–6 revealed no significant country- or region-specific clustering. This study suggests that Vietnam pvmsp-1 ICB 5–6 exhibited a substantial genetic diversity with regional variations, implying the genetic heterogeneity of the Vietnamese P. vivax population. These findings emphasize the importance of continuous molecular surveillance to understand the genetic nature of the parasite in the country.

Vertical transfer of maternal antibodies can provide passive protection to offspring against specific pathogens. In this study, we detected antibodies in the sera of uninfected offspring born to chronically Trichinella spiralis-infected female mice. Immunoblotting consistently revealed a distinct band at ~38 kDa in both T. spiralis excretory-secretory products and total somatic extracts. This band was identified by MALDI-TOF/TOF mass spectrometry as a cystatin-like protein of T. spiralis (Ts-CLP). Structural modeling and domain analysis indicated a typical cystatin-like fold comprising a central α-helix and an antiparallel β-sheet core. To confirm antigen identity, recombinant Ts-CLP protein was expressed and used to generate a polyclonal anti-recombinant Ts-CLP protein antibody. This antibody specifically recognized a ~38 kDa band in T. spiralis excretory-secretory products and total somatic extracts, consistent with that detected by offspring sera. Collectively, these findings demonstrate that maternal antibodies specific to Ts-CLP are vertically transferred and detectable in uninfected offspring. Although the functional significance remains to be determined, this observation provides a basis for future studies on passive immunity and host-parasite interactions.

The incidence of immune system diseases is increasing globally, particularly in developed countries. The hygiene and old friend hypotheses suggest that the decreased incidence of helminth infections in these countries may underlie the rising prevalence of autoimmune, allergic, and inflammatory diseases. The preventive and therapeutic potential of Trichinella spiralis, a helminthic parasite, has been well demonstrated in animal models of immune dysregulation-mediated diseases. This review comprehensively analyze how T. spiralis modulates immune responses across a spectrum of immune dysregulation. We systematically review the key research findings on the effects of T. spiralis infection on immune-related disease. T. spiralis has shown the ability to regulate host immune responses in autoimmune, allergic, and inflammatory disorders, exerting anti-inflammatory effects and restoring immune homeostasis through various immunological pathways. Given its significant immunomodulatory potential, T. spiralis represents a promising candidate for therapeutic interventions against immune-mediated diseases, warranting further molecular investigations and clinical applications.