Evaluation of three formulations based on Polymorphic membrane protein D in mice infected with Chlamydia trachomatis.

The significant impact of Chlamydia trachomatis(Ct) infections worldwide highlights the need to develop a prophylactic vaccine that elicits effective immunity and protects the host from the immunopathological effects of Ct infection. The aim of this study was to evaluate a vaccine based on a fragment of the Polymorphic membrane protein D (FPmpD) of C. trachomatis as an immunogen using a heterologous DNA prime-protein boost strategy in female mice Three different formulations were evaluated as protein boost: free recombinant FPmpD (rFPmpD) or rFPmpD formulated with a liposomal adjuvant alternatively supplemented with CpG or a cationic gemini lipopeptide as immunostimulants. The three candidates induced an increase in the cervicovaginal and systemic titers of anti-rFPmpD antibodies in two strains of mice (BALB/c and C57BL/6), with no evidence of fertility alterations. The three formulations induced a rapid and robust humoral immune response upon the Ct challenge. However, the booster with free rFPmpD more efficiently reduced the shedding of infective Ct and prevented the development of immunopathology. The formulations containing adjuvant induced a strong inflammatory reaction in the uterine tissue. Hence, the prime-boost strategy with the adjuvant-free FPmpD vaccine formulation might constitute a promissory candidate to prevent C. trachomatis intravaginal infection.

Antibodies to SARS-CoV2 induced by vaccination and infection correlate with protection against the infection.

The COVID-19 pandemic remained worldwide for almost three years, but little is known about the dynamics of humoral immune response to the third dose over time and its protection from infection. Our aim was to assess the humoral immune response after the third dose of the different vaccines administered to SARS-CoV-2 naive and previously infected individuals, and its correlation with protection in an academic community. For each person studied (185), three blood samples were taken between December 2021 and July 2022, one month apart. Anti-S antibodies were quantified by ELISA, while anti-N antibody levels were determined by ECLIA. Most of the participants had received two doses of viral vector-based, mRNA-based and virus-inactivated vaccines. Although anti-N antibody levels revealed that 80% of the individuals had been exposed to the virus before or during the study, only 42% reported having been diagnosed. When anti-S IgG levels were measured 3-5 months after the second dose of any vaccine, they were higher in those previously infected individuals. The same results were observed for anti-N IgG levels in those who received 2 doses of the virus-inactivated vaccine. When analyzing the dynamics of anti-S antibodies we observed that, although positive IgG antibody levels were detected 5-6 months after the second dose administration, those observed 30-60 days after the third dose were significantly higher and remained so for at least 8 months. Higher levels of anti-S IgG antibodies at the first sampling were associated with a lower incidence of subsequent infection. The same association was seen in people who received the booster compared with those who received two doses. This study provides further evidence that anti-S IgG antibodies remained at high levels over time, and both anti-S levels and the third dose of anti-SARS-CoV-2 vaccine correlate with protection against the infection. It also shows that infection acts as a booster of immunization, increasing levels of both anti-N and anti-S IgG.