Toxoplasma gondiiis an obligate intracellular parasite infecting humans and other warm-blooded animals, resulting in serious public health problems and economic losses worldwide. Rhoptries are involved inT. gondiiinvasion and host cell interaction and have been implicated as important virulence factors. In the present study, a DNA vaccine expressing rhoptry protein 13 (ROP13) ofT. gondiiinserted into eukaryotic expression vector pVAX I was constructed, and the immune protection it induced in Kunming mice was evaluated. Kunming mice were immunized intramuscularly with pVAX-ROP13 and/or with interleukin-18 (IL-18). Then, we evaluated the immune response using a lymphoproliferative assay, cytokine and antibody measurements, and the survival times of mice challenged with the virulentT. gondiiRH strain (type I) and the cyst-forming PRU strain (type II). The results showed that pVAX-ROP13 alone or with pVAX/IL-18 induced a high level of specific anti-T. gondiiantibodies and specific lymphocyte proliferative responses. Coinjection of pVAX/IL-18 significantly increased the production of gamma interferon (IFN-γ), IL-2, IL-4, and IL-10. Further, challenge experiments showed that coimmunization of pVAX-ROP13 with pVAX/IL-18 significantly (P< 0.05) increased survival time (32.3 ± 2.7 days) compared with pVAX-ROP13 alone (24.9 ± 2.3 days). Immunized mice challenged withT. gondiicysts (strain PRU) had a significant reduction in the number of brain cysts, suggesting that ROP13 could trigger a strong humoral and cellular response againstT. gondiicyst infection and that it is a potential vaccine candidate against toxoplasmosis, which provided the foundation for further development of effective vaccines againstT. gondii.

Since the SARS-CoV-2 outbreak, pharmaceutical companies and researchers worldwide have worked hard to develop vaccines and drugs to end the SARS-CoV-2 pandemic. The potential pathogen responsible for Coronavirus Disease 2019 (COVID-19), SARS-CoV-2, belongs to a novel lineage of beta coronaviruses in the subgenus arbovirus. Antiviral drugs, convalescent plasma, monoclonal antibodies, and vaccines are effective treatments for SARS-CoV-2 and are beneficial in preventing infection. Numerous studies have already been conducted using the genome sequence of SARS-CoV-2 in comparison with that of other SARS-like viruses, and numerous treatments/prevention measures are currently undergoing or have already undergone clinical trials. We summarize these studies in depth in the hopes of highlighting some key details that will help us to better understand the viral origin, epidemiology, and treatments of the virus.

Host cell invasion byToxoplasma gondiiis tightly related to microneme protein 6 (MIC6) andT. gondiiperforin-like protein 1 (TgPLP1). In this study, we constructed a DNA vaccine expressing a TgPLP1/MIC6 fusion protein using the pIRESneo vector, and we evaluated the immune response induced by this vaccine in Kunming mice. Levels of IgG antibody, gamma interferon (IFN-γ), interleukin 2 (IL-2), IL-12, IL-4, and IL-10 were examined. Five mice were chosen randomly from every group (vaccinated groups or the nonvaccinated control group) and were challenged intragastrically with 80 cysts ofT. gondiistrain PRU (genotype II) in order to observe mortality daily. To analyze protection against a less-virulent challenge, eight mice of each group were orally infected with 20 cysts of strain PRU at the 14th day after the last immunization. The brain parasite load was evaluated 6 weeks after infection. The results demonstrated that immunization with pIRESneo/MIC6/PLP1 resulted in the lowest brain cyst count and prolonged the survival time of immunized mice. The levels ofToxoplasma-specific IgG, IFN-γ, IL-2, and IL-12 increased significantly, and the numbers of cysts in brains decreased more obviously, in the group immunized with plasmid pIRESneo/MIC6/PLP1 than in the other groups (P< 0.05). Compared with pIRESneo/MIC6/PLP1, coimmunization with pIRESneo/MIC6/PLP1 and adjuvant murine IL-18 promoted cellular and humoral immune responses but did not contribute significantly to cyst reduction (65.43% versus 61.60%) or the survival of immunized mice (45.0 ± 2.9 days versus 42.8 ± 2.9 days) (P> 0.05). Furthermore, the study also showed that the immune efficacy induced by pIRESneo/MIC6/PLP1 was better than that induced by pVAX/PLP1 or pVAX/MIC6 alone.

The frequency of Toxoplasma gondii antibodies in stray and household dogs in Guangzhou, China was examined by ELISA on serum samples from 150 animals (36 strays and 114 from households) and the overall prevalence was 21.3%. The extent of infection in stray dogs (33.3%) was significantly higher (P < 0.05) than in household dogs (17.5%). Infection in male and female dogs of both groups was not significantly different (P ≥ 0.05), i.e., 31.8% versus 35.7% for male and female in stray dogs, and 14.5% versus 22.2% in household dogs. The results of the present investigation indicate that the seroprevalence of T. gondii infection in dogs was high in Guangzhou, especially in strays. Therefore, it is essential to implement integrated strategies to prevent and control T. gondii infection in both stray and household dogs.