Unconjugated
Mycobacterium tuberculosis (M. tb) is emerging as a more serious pathogen due to the increased multidrug-resistant TB and co-infection of human immunodeficiency virus (HIV). The development of an effective and sensitive detection method is urgently needed for bacterial load evaluation in vaccine development, early TB diagnosis, and TB treatment. Droplet digital polymerase chain reaction (ddPCR) is a newly developed sensitive PCR method for the absolute quantification of nucleic acid concentrations. Here, we used ddPCR to quantify the circulating virulent M. tb-specific CFP10 (10-kDa culture filtrate protein, Rv3874) and Rv1768 DNA copy numbers in the blood samples from Bacille Calmette-Guerin (BCG)-vaccinated and/or virulent M. tb H37Rv-challenged rhesus monkeys. We found that ddPCR was more sensitive compared to real-time fluorescence quantitative PCR (qPCR), as the detection limits of CFP10 were 1.2 copies/µl for ddPCR, but 15.8 copies/µl for qPCR. We demonstrated that ddPCR could detect CFP10 and Rv1768 DNA after 3 weeks of infection and at least two weeks earlier than qPCR in M.tb H37Rv-challenged rhesus monkey models. DdPCR could also successfully quantify CFP10 and Rv1768 DNA copy numbers in clinical TB patients' blood samples (active pulmonary TB, extrapulmonary TB (EPTB), and infant TB). To our knowledge, this study is the first to demonstrate that ddPCR is an effective and sensitive method of measuring the circulating CFP10 and Rv1768 DNA for vaccine development, bacterial load evaluation in vivo, and early TB (including EPTB and infant TB) diagnosis as well.
The search for a universal filovirus vaccine that provides protection against multiple filovirus species has been prompted by sporadic but highly lethal outbreaks of Ebolavirus and Marburgvirus infections. A good prophylactic vaccine should be able to provide protection to all known filovirus species and as an upside potentially protect from newly emerging virus strains. We investigated the immunogenicity and protection elicited by multivalent vaccines expressing glycoproteins (GP) from Ebola virus (EBOV), Sudan virus (SUDV), Taï Forest virus (TAFV) and Marburg virus (MARV). Immune responses against filovirus GP have been associated with protection from disease. The GP antigens were expressed by adenovirus serotypes 26 and 35 (Ad26 and Ad35) and modified Vaccinia virus Ankara (MVA) vectors, all selected for their strong immunogenicity and good safety profile. Using fully lethal NHP intramuscular challenge models, we assessed different vaccination regimens for immunogenicity and protection from filovirus disease. Heterologous multivalent Ad26-Ad35 prime-boost vaccination regimens could give full protection against MARV (range 75%-100% protection) and EBOV (range 50% to 100%) challenge, and partial protection (75%) against SUDV challenge. Heterologous multivalent Ad26-MVA prime-boost immunization gave full protection against EBOV challenge in a small cohort study. The use of such multivalent vaccines did not show overt immune interference in comparison with monovalent vaccines. Multivalent vaccines induced GP-specific antibody responses and cellular IFN? responses to each GP expressed by the vaccine, and cross-reactivity to TAFV GP was detected in a trivalent vaccine expressing GP from EBOV, SUDV and MARV. In the EBOV challenge studies, higher humoral EBOV GP-specific immune responses (p = 0.0004) were associated with survival from EBOV challenge and less so for cellular immune responses (p = 0.0320). These results demonstrate that it is feasible to generate a multivalent filovirus vaccine that can protect against lethal infection by multiple members of the filovirus family.