The PvCelTOS, PvCyRPA, and Pvs25 proteins play important roles during the three stages of the P. vivax lifecycle. In this study, we designed and expressed a P. vivax recombinant modular chimeric protein (PvRMC-1) composed of the main antigenic regions of these vaccine candidates. After structure modelling by prediction, the chimeric protein was expressed, and the antigenicity was assessed by IgM and IgG (total and subclass) ELISA in 301 naturally exposed individuals from the Brazilian Amazon. The recombinant protein was recognized by IgG (54%) and IgM (40%) antibodies in the studied individuals, confirming the natural immunogenicity of the epitopes that composed PvRMC-1 as its maintenance in the chimeric structure. Among responders, a predominant cytophilic response mediated by IgG1 (70%) and IgG3 (69%) was observed. IgM levels were inversely correlated with age and time of residence in endemic areas (p < 0.01). By contrast, the IgG and IgM reactivity indexes were positively correlated with each other, and both were inversely correlated with the time of the last malaria episode. Conclusions: The study demonstrates that PvRMC-1 was successfully expressed and targeted by natural antibodies, providing important insights into the construction of a multistage chimeric recombinant protein and the use of naturally acquired antibodies to validate the construction.

The Plasmodium vivax Cysteine-Rich Protective Antigen (PvCyRPA) has an important role in erythrocyte invasion and has been considered a target for vivax malaria vaccine development. Nonetheless, its genetic diversity remains uncharted in Brazilian malaria-endemic areas. Therefore, we investigated the pvcyrpa genetic polymorphism in 98 field isolates from the Brazilian Amazon and its impact on the antigenicity of predicted B-cell epitopes. Genetic diversity parameters, population genetic analysis, neutrality test and the median-joining network were analyzed, and the potential amino acid polymorphism participation in B-cell epitopes was investigated. One synonymous and 26 non-synonymous substitutions defined fifty haplotypes. The nucleotide diversity and Tajima’s D values varied across the coding gene. The exon-1 sequence had greater diversity than those of exon-2. Concerning the prediction analysis, seven sequences were predicted as linear B cell epitopes, the majority contained in conformational epitopes. Moreover, important amino acid polymorphism was detected in regions predicted to contain residues participating in B-cell epitopes. Our data suggest that the pvcyrpa gene presents a moderate polymorphism in the studied isolates and such polymorphisms alter amino acid sequences contained in potential B cell epitopes, an important observation considering the antigen potentiality as a vaccine candidate to cover distinct P. vivax endemic areas worldwide.

Oral manifestations of HIV infection can be an early sign of the disease and may indicate progression to AIDS. Although antiretroviral therapies, especially highly active antiretroviral therapy (HAART), have reduced the prevalence of HIV-related oral lesions, ongoing updates in diagnosis and treatment are essential due to the extended life expectancy of individuals living with HIV. Periodontal disease is a significant concern in these patients, influenced by altered immune responses and microbial dynamics, though the mechanisms are not fully understood. This exploratory study aimed to investigate the oral microbiota and periodontal disease prevalence in HIV-positive individuals by analyzing subgingival plaque samples from 24 patients. We identified 12 bacterial species using Polymerase Chain Reaction (PCR) and amplicon sequencing. Seven species were detected, with Filifactor alocis, Tannerella forsythia, and Porphyromonas endodontalis being the most common. Porphyromonas gingivalis was present in only 13.6% of samples, while T. forsythia was found in 58.3%. Genetic diversity was also observed in P. endodontalis and Selenomonas sputigena amplicons, with specific single nucleotide polymorphisms (SNPs) identified in both species. These results highlight the complex microbial interactions in the oral environments of people living with HIV, emphasizing the need for personalized diagnostic and therapeutic strategies for managing oral health in this population.