Seroconversion after three doses of intramuscular rabies vaccine as a post-exposure treatment

Real-world evidence of rabies post-exposure prophylaxis in Serbia: Nation-wide observational study (2017-2019)

BACKGROUND

Rabies remains a deadly zoonotic disease, primarily prevalent in Eastern European countries, with a significant global burden in Asia and Africa. Post-exposure prophylaxis (PEP) is critical to prevent clinical rabies. Serbia, a country with a relatively low animal rabies incidence, has been implementing a 4-dose Essen PEP regimen for 13 years. This real-world study aimed to assess the effectiveness of the 4-dose Essen regimen, considering demographic and clinical factors, after WHO Category III exposure.

METHOD

The study included 601 patients who received the 4-dose Essen PEP and 79 who received an additional 5th dose.

RESULTS

Age emerged as a critical factor influencing seroconversion rates after the 4-dose regimen, with older individuals exhibiting lower RVNA titers. Logistic regression indicated a 3.18% decrease in seroconversion odds for each added year of age. The Cox proportional hazards mixed model highlighted age-related risks, with age groups 45-60 and 75-92 at the highest risk of non-seroconversion. Human Rabies Immune Globulin (HRIG) administration was associated with lower RVNA values after the 4-dose regimen, suggesting interference with vaccine immunogenicity among people who received larger doses of HRIG.

CONCLUSIONS

This study provides valuable real-world evidence for rabies PEP in a non-homogeneous population with potential comorbidities. The results underscore the importance of optimizing PEP strategies, particularly in older individuals, and reconsidering HRIG dosing to improve seroconversion rates.

Evaluating the benefit of serology during potential Australian bat lyssavirus and rabies post-exposure prophylaxis

Post-exposure prophylaxis (PEP) for potential lyssavirus exposures consists of wound management, rabies vaccination and may include rabies immunoglobulin (RIG). Rabies serology is sometimes indicated if there is risk of PEP failure.

OBJECTIVES

Evaluate the benefit of serology by indication.

METHODS

Chart review of potential lyssavirus exposures managed at a Public Health Unit (June 2015 - December 2022) where serology was requested was conducted. The proportion of non-therapeutic titres was compared by sex, age, Indigenous status, serology indication, and whether RIG was given.

RESULTS

46 notifications with serology were included. Males (5/19) and people over 40 (3/16) were more likely to demonstrate a non-therapeutic response. 2/3 of cases where vaccine doses were not given in the deltoid were non-therapeutic. The rate of non-therapeutic titres was similar for RIG given into the ipsilateral arm (2/11) and given excess RIG for weight (1/4). Although this small sample was inconclusive in isolation, it was also noted that all cases who did not receive RIG had therapeutic serology, whereas 6/35 of those receiving RIG had non-therapeutic serology.

CONCLUSIONS

This study supports broader literature questioning the utility of systemic RIG administration as likely limited and potentially detrimental considering the increased risk of immune interference.

IMPLICATIONS FOR PUBLIC HEALTH

Highlights a need to review Australian national guidelines to align with World Health Organization advice recommending local RIG administration only.

Unmodified rabies mRNA vaccine elicits high cross-neutralizing antibody titers and diverse B cell memory responses

Licensed rabies virus vaccines based on whole inactivated virus are effective in humans. However, there is a lack of detailed investigations of the elicited immune response, and whether responses can be improved using novel vaccine platforms. Here we show that two doses of a lipid nanoparticle-formulated unmodified mRNA vaccine encoding the rabies virus glycoprotein (RABV-G) induces higher levels of RABV-G specific plasmablasts and T cells in blood, and plasma cells in the bone marrow compared to two doses of Rabipur in non-human primates. The mRNA vaccine also generates higher RABV-G binding and neutralizing antibody titers than Rabipur, while the degree of somatic hypermutation and clonal diversity of the response are similar for the two vaccines. The higher overall antibody titers induced by the mRNA vaccine translates into improved cross-neutralization of related lyssavirus strains, suggesting that this platform has potential for the development of a broadly protective vaccine against these viruses.

Clofazimine derivatives as potent broad-spectrum antiviral agents with dual-target mechanism

Thirty-two clofazimine derivatives, of which twenty-two were new, were synthesized and evaluated for their antiviral effects against both rabies virus and pseudo-typed SARS-CoV-2, taking clofazimine (1) as the lead. Among them, compound 15f bearing 4-methoxy-2-pyridyl at the N5-position showed superior or comparable antiviral activities to lead 1, with the EC₅₀ values of 1.45 μM and 14.6 μM and the SI values of 223 and 6.1, respectively. Compound 15f inhibited rabies and SARS-CoV-2 by targeting G or S protein to block membrane fusion, as well as binding to L protein or nsp13 to inhibit intracellular biosynthesis respectively, and thus synergistically exerted a broad-spectrum antiviral effect. The results provided useful scientific data for the development of clofazimine derivatives into a new class of broad-spectrum antiviral candidates.