An overview of the immunogenicity and effectiveness of current human rabies vaccines administered by intradermal route

Current Status of Vaccines for Porcine Reproductive and Respiratory Syndrome: Interferon Response, Immunological Overview, and Future Prospects

Porcine reproductive and respiratory syndrome (PRRS) remains a formidable challenge for the global pig industry. Caused by PRRS virus (PRRSV), this disease primarily affects porcine reproductive and respiratory systems, undermining effective host interferon and other immune responses, resulting in vaccine ineffectiveness. In the absence of specific antiviral treatments for PRRSV, vaccines play a crucial role in managing the disease. The current market features a range of vaccine technologies, including live, inactivated, subunit, DNA, and vector vaccines, but only modified live virus (MLV) and killed virus (KV) vaccines are commercially available for PRRS control. Live vaccines are promoted for their enhanced protective effectiveness, although their ability to provide cross-protection is modest. On the other hand, inactivated vaccines are emphasized for their safety profile but are limited in their protective efficacy. This review updates the current knowledge on PRRS vaccines' interactions with the host interferon system, and other immunological aspects, to assess their current status and evaluate advents in PRRSV vaccine development. It presents the strengths and weaknesses of both live attenuated and inactivated vaccines in the prevention and management of PRRS, aiming to inspire the development of innovative strategies and technologies for the next generation of PRRS vaccines.

Rabies post-exposure prophylaxis delivery to ensure treatment efficacy and increase compliance

Objectives

Since rabies is lethal once symptoms appear, its prevention including community awareness, mass dog vaccination and post-exposure prophylaxis (PEP) is crucial. Although safe and potent rabies vaccines have long been available, the global rabies burden is still high and access to adequately-delivered PEP remains challenging. Here we offer healthcare providers up-to-date, simple, exhaustive, visual guidance on how to perform PEP steps correctly.

Protocol

PEP consists of 1) washing the wound with water and soap for 15 min, 2) assessing the need for rabies biologicals based on specific criteria; 3) administering, if required, rabies immunoglobulin or monoclonal antibodies deep in and around all wounds; 4) starting, if necessary, the WHO-recommended intradermal 1-week vaccination regimen; 5) informing patients adequately throughout the PEP process to increase compliance and avoid dangerous misconceptions about animal bite treatment and rabies risk.

Discussion

The intradermal 1-week vaccination regimen recommended by WHO is as safe as other regimens but carries important cost-, dose- and time-sparing benefits. As fundamental as the correct administration of rabies biologicals is clear doctor-patient communication and sharing of up-to-date knowledge among healthcare professionals.

Conclusions

This resource will help ensuring that no life is lost to rabies, an incurable yet preventable disease.

Side-by-side Comparative Study of the Immunogenicity of the Intramuscular and Intradermal Rabies Post-exposure Prophylaxis Regimens in a Cohort of Suspected Rabies Virus Exposed Individuals

All World Health Organization (WHO) pre-qualified rabies vaccines for humans are inactivated tissue culture rabies virus formulations produced for intramuscular (IM) administration. Due to costs and vaccine shortage, dose-saving intradermal (ID) administration of rabies post-exposure prophylaxis (PEP) is encouraged by WHO. This study compared the immunogenicity of the ID 2-site, 3-visit Institut Pasteur Cambodge (IPC) PEP regimen to the IM 1-site, 4-visit 4-dose Essen regimen using Verorab vaccine (Sanofi). The development of neutralizing antibodies (nAbs) and T cell response was assessed in 210 patients with a category II or III animal exposure in a rabies-endemic country. At day 28, all participants developed nAbs (≥0.5 IU/mL), irrespective of PEP scheme, age, or administration of rabies immunoglobulin. T cell response and nAb titers were similar for both PEP schemes. This study demonstrated that the 1-week ID IPC regimen is as effective as the 2-week IM 4-dose Essen regimen in inducing an anti-rabies immune response under real-life PEP.

Addressing vaccine-preventable encephalitis in vulnerable populations

PURPOSE OF REVIEW

Vaccinations have been pivotal in lowering the global disease burden of vaccine-preventable encephalitides, including Japanese encephalitis, tick-borne encephalitis, measles encephalitis, and rabies encephalitis, among others.

RECENT FINDINGS

Populations vulnerable to vaccine-preventable infections that may lead to encephalitis include those living in endemic and rural areas, military members, migrants, refugees, international travelers, younger and older persons, pregnant women, the immunocompromised, outdoor, healthcare and laboratory workers, and the homeless. There is scope for improving the availability and distribution of vaccinations, vaccine equity, surveillance of vaccine-preventable encephalitides, and public education and information.

SUMMARY

Addressing these gaps in vaccination strategies will allow for improved vaccination coverage and lead to better health outcomes for those most at risk for vaccine-preventable encephalitis.

Safety of purified Vero cell rabies vaccine manufactured in Pakistan: A comparative analysis of intradermal and intramuscular routes

BACKGROUND

Rabies vaccines are conventionally given via the intramuscular (IM) route; however, switching the route of administration from IM to intradermal (ID) without affecting efficacy can be advantageous in terms of cost, dosing, and time. Hence, it is indispensable to evaluate its safety along different routes. This study was carried out to ascertain the frequency of adverse drug events (ADEs) and associated factors, as well as to compare safety based on the IM and ID routes.

METHODS

A prospective observational study was carried out on 184 individuals with rabies exposure. The vaccination schedules for post-exposure prophylaxis (PEP) included 0.2 milliliter (ml) of purified Vero cell rabies vaccine (PVRV) administered ID at two different sites with 0.1ml each on days 0, 3, and 7 in first group (3-dose regimen ID) and 0.5 ml administered IM on days 0, 3, 7, 14, and 28 in the second group (5-dose regimen IM). The safety of the vaccines was determined by reviewing ADEs during physical examinations and follow-up. ADEs were characterized by local and systemic effects.

RESULTS

Of the total, 99 (53.80%) patients reported ADEs. Those who reported local and systemic ADEs were 80 (43.48%) and 59 (32.06%), respectively, while simultaneous occurrence was reported in 40 (40.40%) patients. The most frequent local ADE 76 (41.30%) reported was pain followed by erythema 18 (9.78%). Additionally, fever was in highest proportion 25 (13.59%) for systemic effects, followed by headache 15 (8.15%). The patients reported with ADEs by the IM and ID routes was comparable (p > 0.05). Similarly, both local and systemic effects were also comparable (p > 0.05).

CONCLUSION

Half of the study participants reported ADEs. Almost similar proportions of local and systemic effects were observed. Likewise, the ADEs recorded were comparable for both routes. PVRV carries very low safety concerns with either route for administration.

Development and Evaluation of an Enzyme-Linked Immunosorbent Assay Targeting Rabies-Specific IgM and IgG in Human Sera

Immunity from rabies depends on rabies virus neutralizing antibodies (RVNA) induced after immunization; however, the influence of antibody isotype switching has not been extensively investigated. This has become particularly relevant with changes in World Health Organization (WHO) recommended rabies vaccine regimens that may influence RVNA isotype kinetics, potentially affecting the peak, and longevity, of RVNA immunoglobulin (IgG) levels. We developed rapid and reliable assays for quantifying the anti-rabies IgM/IgG class switch in human serum based on an indirect ELISA technique. The immune response was tracked in ten individuals naïve to the rabies vaccine by quantifying serum titers weekly, from day seven to day 42 post-immunization, using a serum neutralization assay and the ELISA IgM/IgG assays. The average RVNA IU/mL levels were at D0 ≤ 0.1, D7 0.24, D14 8.36, D21 12.84, D28 25.74 and D42 28.68. Levels of specific IgM antibodies to rabies glycoprotein (EU/mL) were higher, on average, at D7, 1.37, and from D14, 5.49, to D21, 6.59. In contrast, average IgG antibodies (EU/mL) predominated from D28, 10.03, to D42, 14.45. We conclude that levels of anti-rabies IgM/IgG at D28 characterize the isotype class switch. These assays, combined with serum neutralization assays, distinguished the RVNA levels in terms of the IgM/IgG responses and are expected to add to the diagnostic repertoire, provide additional information in establishing rabies vaccine regimens, both post- and pre-exposure prophylaxis, and contribute to research efforts.

Immunogenicity and reactogenicity of accelerated regimens of fractional intradermal COVID-19 vaccinations

Introduction

This phase I study explored the immunogenicity and reactogenicity of accelerated, Q7 fractional, intradermal vaccination regimens for COVID-19.

Methods

Participants (n = 60) aged 18-60 years, naïve to SARS-CoV-2 infection or vaccination, were randomly allocated into one of four homologous or heterologous accelerated two-dose, two-injection intradermal regimens seven days apart:(1) BNT162b2-BNT162b2(n= 20),(2) ChAdOx1- BNT162b2 (n = 20), (3) CoronaVac-ChAdOx1 (n = 10), and (4) ChAdOx1-ChAdOx1 (n = 10). CoronaVac and ChAdOx1 were 20%, and BNT162b2 17%, of their standard intramuscular doses (0.1 mL and 0.05 mL per injection, respectively). Humoral immune responses were measured through IgG response towards receptor binding domains (RBD-IgG) of ancestral SARS-CoV-2 spike protein and pseudovirus neutralization tests (PVNT50). Cellular immune responses were measured using ELISpot for ancestral protein pools.

Results

Immunogenicity was highest in regimen (2), followed by (1), (4), and (3) 2 weeks after the second dose (P < 0.001 for anti-RBD-IgG and P= 0.01 for PVNT50). Each group had significantly lower anti-RBD IgG (by factors of 5.4, 3.6, 11.6, and 2.0 for regimens (1) to (4), respectively) compared to their respective standard intramuscular regimens (P < 0.001 for each). Seroconversion rates for PVNT50 against the ancestral strain were 75%, 90%, 57% and 37% for regimens (1) to (4), respectively. All participants elicited ELISpot response to S-protein after vaccination. Adverse events were reportedly mild or moderate across cohorts.

Discussion

We concluded that accelerated, fractional, heterologous or homologous intradermal vaccination regimens of BNT162b2 and ChAdOx1 were well tolerated, provided rapid immune priming against SARS-CoV-2, and may prove useful for containing future outbreaks.

Delays in initiating rabies post-exposure prophylaxis among dog bite victims in Wakiso and Kampala districts, Uganda

Background   Although rabies in dog bite patients is preventable through timely initiation of post-exposure prophylaxis (PEP), a number of barriers to achieving PEP exist. This study investigated the delays to initiation of PEP among dog bite patients in the emergency departments of two PEP centers in Uganda. Methods A cross-sectional study was conducted among dog-bite patients that presented to two selected rabies PEP centers. A semi-structured questionnaire was used to collect data. Delay to receive PEP was defined as reporting for PEP beyond 24 hours after the bite event. Generalized linear models were used to calculate prevalence ratios and the 95% confidence intervals as a measure of association between delay and patient factors. Results Out of 376 participants, just over half (53.5%) were males. The majority of participants (54.0%) were 15 years or older and 28.5% had no formal education. Just over three-quarters (77.9%) had category II dog bite wounds. Nearly 40% delayed to receive PEP, and median (inter quartile range) lag time between bite event and seeking medical care of 18 (41) hours. Compared to education level of secondary or above, patients with no formal education (adj. PR=4.06, 95% CI: 2.69 -  6.10) or primary education (adj.PR=2.15, 95% CI: 1.37 -  3.35), belonging to the lowest socio-economic tertile as compared to the highest (adj.PR=1.58, 95% CI: 1.10 - 2.28), knowing the owner of the biting dog (adj.PR=1.30, 95% CI: 1.02 - 1.65) and having category II wounds (adj.PR=2.31, 95% CI: 1.43 - 3.71) were all associated with delayed presentation for PEP. Conclusions and recommendations Delays to receive PEP are common and are associated with poor level of education or low socio-economic status, knowledge of who the dog owner is and less severity of bite wounds. Seeking care irrespective of wound severity or knowledge of dog owner should be promoted.

Comparative immunogenicity analysis of intradermal versus intramuscular immunization with a recombinant human adenovirus type 5 vaccine against Ebola virus

The proper route for vaccine delivery plays an important role in activating a robust immune response. Several viral vector-based vaccines against Ebola disease administered intramuscularly have been found to have excellent immunogenicity and protectiveness. In this study, we evaluated different vaccine routes for Ad5-EBOV delivery by comparing humoral and cellular responses, germinal center reactions, dendritic cell activation and antigen expression. Mice injected intramuscularly with the vaccine exhibited an advantage in antigen expression, leading to more robust germinal center and humoral responses, while intradermal injection recruited more migrating DCs and induced a more polyfunctional cellular response. Our study provides more data for future use of viral vector-based vaccines.

One-week intramuscular or intradermal pre-exposure prophylaxis with human diploid cell vaccine or Vero cell rabies vaccine, followed by simulated post-exposure prophylaxis at one year: A phase III, open-label, randomized, controlled trial to assess immunogenicity and safety

Shorter rabies pre-exposure prophylaxis (PrEP) regimens may offer improved convenience and feasibility over classic 3-week regimens, for example in regions with poor access to vaccines or for travelers to rabies-endemic regions. In this multicenter, open-label, controlled trial, 570 healthy participants aged 2-64 years were randomized to receive: 1-week PrEP (vaccination days [D]0 and 7; Group 1) or classic 3-week PrEP regimen (D0, D7, and D21; Group 2) with one 1.0 mL intramuscular [IM] dose of human diploid cell culture rabies vaccine (HDCV) at each visit; 1-week PrEP with two 0.1 mL intradermal (ID) HDCV doses at each visit (Group 3); or 1-week PrEP with one 0.5 mL IM dose (Group 4) or two 0.1 mL ID doses (Group 5) of Vero cell rabies vaccine (PVRV) at each visit. Participants received simulated post-exposure prophylactic (PEP) vaccination (two IM or ID doses of HDCV or PVRV three days apart) one year later. Rabies virus neutralizing antibody titers and seroconversion (titers ≥ 0.5 IU/mL) rates were assessed 14 days and up to 1 year post-PrEP, and pre- and post-PEP. Safety was assessed throughout the study. Seroconversion rates were high 14 days post-last PrEP injection (ranging from 96.7 % to 97.2 % across groups 1, 3-5; 1-week PrEP) and reached 100 % in Group 2 (3-week PrEP). Non-inferiority of Group 1 versus Group 2 in terms of seroconversion rates 14 days post-last PrEP injection (primary objective) was not demonstrated. After simulated PEP, all groups showed rapid and robust immune responses, with all but one participant achieving seroconversion (titers ≥ 0.5 IU/mL). There were no safety concerns, and the tolerability profiles of the vaccines were similar across the groups. A 1-week, IM or ID PrEP regimen with HDCV or PVRV provided efficacious priming, enabling rapid robust anamnestic responses to simulated PEP 1 year later across age groups. ClinicalTrials.gov number: NCT03700242. WHO Universal Trial Number (UTN): U1111-1183-5743.

Delays in initiating rabies post-exposure prophylaxis among dog bite victims in Wakiso and Kampala districts, Uganda

Background: Although rabies in dog bite patients is preventable through timely initiation of post-exposure prophylaxis (PEP), a number of barriers to achieving PEP exist. This study investigated the delays to initiation of PEP among dog bite patients in the emergency departments of two PEP centers in Uganda. Methods: A cross-sectional study was conducted among dog-bite patients that presented to two selected rabies PEP centers. A semi-structured questionnaire was used to collect data. Delay to receive PEP was defined as reporting for PEP beyond 24 hours after the bite event. Generalized linear models were used to calculate prevalence ratios and the 95% confidence intervals as a measure of association between delay and patient factors. Results: Out of 376 participants, just over half (53.5%) were males. The majority of participants (54.0%) were 15 years or older and 28.5% had no formal education. Just over three-quarters (77.9%) had category II dog bite wounds. Nearly 40% delayed to receive PEP, and median (inter quartile range) lag time between bite event and seeking medical care of 18 (41) hours. Compared to education level of secondary or above, patients with no formal education (adj. PR=4.06, 95% CI: 2.69 -  6.10) or primary education (adj.PR=2.15, 95% CI: 1.37 -  3.35), belonging to the lowest socio-economic tertile as compared to the highest (adj.PR=1.58, 95% CI: 1.10 - 2.28), knowing the owner of the biting dog (adj.PR=1.30, 95% CI: 1.02 - 1.65) and having category II wounds (adj.PR=2.31, 95% CI: 1.43 - 3.71) were all associated with delayed presentation for PEP. Conclusions and recommendations: Delays to receive PEP are common and are associated with poor level of education or low socio-economic status, knowledge of who the dog owner is and less severity of bite wounds. Seeking care irrespective of wound severity or knowledge of dog owner should be promoted.

Delays in initiating rabies post-exposure prophylaxis among dog bite victims in Wakiso and Kampala districts, Uganda

Background: Although rabies in dog bite patients is preventable through timely initiation of post-exposure prophylaxis (PEP), a number of barriers to achieving PEP exist. This study investigated the delays to initiation of PEP among dog bite patients in the emergency departments of two PEP centers in Uganda. Methods: A cross-sectional study was conducted among dog-bite patients that presented to two selected rabies PEP centers. A semi-structured questionnaire was used to collect data. Delay to receive PEP was defined as reporting for PEP beyond 24 hours after the bite event. Generalized linear models were used to calculate prevalence ratios and the 95% confidence intervals as a measure of association between delay and patient factors. Results: Out of 376 participants, just over half (53.5%) were males. The majority of participants (54.0%) were 15 years or older and 28.5% had no formal education. Just over three-quarters (77.9%) had category II dog bite wounds. Nearly 40% delayed to receive PEP, and median (IQR) lag time between bite event and seeking medical care of 18 (41) hours. Compared to education level of secondary or above, patients with no formal education (adj. PR=4.06, 95% CI: 2.69 -  6.10) or primary education (adj.PR=2.15, 95% CI: 1.37 -  3.35), belonging to the lowest socio-economic tertile as compared to the highest (adj.PR=1.58, 95% CI: 1.10 - 2.28), knowing the owner of the biting dog (adj.PR=1.30, 95% CI: 1.02 - 1.65) and having category II wounds (adj.PR=2.31, 95% CI: 1.43 - 3.71) were all associated with delayed presentation for PEP. Conclusions and recommendations: Delays to receive PEP are common and are associated with poor level of education or low socio-economic status, knowledge of who the dog owner is and less severity of bite wounds. Seeking care irrespective of wound severity or knowledge of dog owner should be promoted.

Natural-Product-Based Solutions for Tropical Infectious Diseases

About half of the world's population and 80% of the world's biodiversity can be found in the tropics. Many diseases are specific to the tropics, with at least 41 diseases caused by endemic bacteria, viruses, parasites, and fungi. Such diseases are of increasing concern, as the geographic range of tropical diseases is expanding due to climate change, urbanization, change in agricultural practices, deforestation, and loss of biodiversity. While traditional medicines have been used for centuries in the treatment of tropical diseases, the active natural compounds within these medicines remain largely unknown. In this review, we describe infectious diseases specific to the tropics, including their causative pathogens, modes of transmission, recent major outbreaks, and geographic locations. We further review current treatments for these tropical diseases, carefully consider the biodiscovery potential of the tropical biome, and discuss a range of technologies being used for drug development from natural resources. We provide a list of natural products with antimicrobial activity, detailing the source organisms and their effectiveness as treatment. We discuss how technological advancements, such as next-generation sequencing, are driving high-throughput natural product screening pipelines to identify compounds with therapeutic properties. This review demonstrates the impact natural products from the vast tropical biome have in the treatment of tropical infectious diseases and how high-throughput technical capacity will accelerate this discovery process.

A broad-spectrum and highly potent human monoclonal antibody cocktail for rabies prophylaxis

Post-exposure prophylaxis (PEP) is highly effective in preventing disease progression of rabies when used in timely and appropriate manner. The key treatment for PEP is infiltration of rabies immune globulin (RIG) into lesion site after bite exposure, besides wound care and vaccination. Unfortunately, however, RIG is expensive and its supply is limited. Currently, several anti-rabies virus monoclonal antibody (mAb) products are under development as alternatives to RIG, and two recently received regulatory approval in India. In this study, fully human mAbs that recognize different rabies virus glycoprotein conformational antigenic site (II and III) were created from peripheral blood mononuclear cells of heathy vaccinated subjects. These mAbs neutralized a diverse range of lyssavirus types. As at least two anti-rabies virus mAbs are recommended for use in human PEP to ensure broad coverage against diverse lyssaviruses and to minimize possible escape variants, two most potent mAbs, NP-19-9 and 11B6, were selected to be used as cocktail treatment. These two mAbs were broadly reactive to different types of lyssaviruses isolates, and were shown to have no interference with each other. These results suggest that NP-19-9 and 11B6 are potent candidates to be used for PEP, suggesting further studies involving clinical studies in human.

Intradermal Vaccination: A Potential Tool in the Battle Against the COVID-19 Pandemic?

This narrative review is the final output of an initiative of the SIM (Italian Society of Mesotherapy). A narrative review of scientific literature on the efficacy of fractional intradermal vaccination in comparison with full doses has been conducted for the following pathogens: influenza virus, rabies virus, poliovirus (PV), hepatitis B virus (HBV), hepatitis A virus (HAV), diphtheria-tetanus-pertussis bacterias (DTP), human papillomavirus (HPV), Japanese encephalitis virus (JE), meningococcus, varicella zoster virus (VZV) and yellow fever virus. The findings suggest that the use of the intradermal route represents a valid strategy in terms of efficacy and efficiency for influenza, rabies and HBV vaccines. Some systematic reviews on influenza vaccines suggest the absence of a substantial difference between immunogenicity induced by a fractional ID dose of up to 20% and the IM dose in healthy adults, elderly, immunocompromised patients and children. Clinical studies of remaining vaccines against other pathogens (HAV, DTP bacterias, JE, meningococcal disease, VZV, and yellow fever virus) are scarce, but promising. In the context of a COVID-19 vaccine shortage, countries should investigate if a fractional dosing scheme may help to save doses and achieve herd immunity quickly. SIM urges the scientific community and health authorities to investigate the potentiality of fractionate intradermal administration in anti-COVID-19 vaccination.

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End of year editorial: hot topics in travel medicine

COVID-19 will reshape travel medicine, in particular in relation to business travellers and the use of digital technologies. Although the hot topic in travel medicine was the COVID-19 pandemic, travel-associated measles, yellow fever and rabies deserve some special attention.

Intradermal rabies pre-exposure vaccination schedules in older travellers: comparison of immunogenicity post-primary course and post-booster

BACKGROUND

Intradermal (ID) rabies vaccination for pre-exposure prophylaxis (PrEP) has become increasingly popular; however, there is limited evidence about the effectiveness of different ID PrEP schedules in travellers aged > 50 years or their response to ID boosters. This study aimed to compare across different ID vaccine schedules and age groups the proportion of travellers who were seropositive after (i) primary course of ID PrEP and (ii) a booster.

METHODS

Travellers who received ID PrEP at a travel medicine clinic in South Australia from 2000 to 2016 were included. Three schedules were examined: 1IDx3 (1 × 0.1 ml on days 0, 7, 21-28), 2IDx2 (2 × 0.1 ml on days 0, 7) and 4IDx1 (4x0.1 ml on day 0). The 4IDx1 is a non-standard schedule that has been previously explored in research settings, but not endorsed by WHO for PrEP. Antibody titres of ≥0.5 IU/ml were considered seropositive. The proportion seropositive after a primary course or post-booster was estimated for each schedule and age category. Predictors of seronegative status after a primary course were examined using multivariable logistic regression models.

RESULTS

Overall, 835 travellers (median age 37.5 years; 37.1% > 50 years) were included in the analyses of seropositivity after a primary course. Another group of 771 travellers (median age 45.9 years; 43.5% > 50 years) was included in the analyses of seropositivity post-booster. The proportion seropositive after primary course was 92.5% (95%CI: 90.5-94.1%) and highest with the 1IDx3 schedule (93.4%; 95%CI: 91.4-95.0%). After adjusting for age and timing of the serology, the odds of seronegative status were four times higher (OR 4.17; 95%CI: 1.43-12.18) with the 4IDx1 schedule compared to 1IDx3. Overall, 98.7% (95%CI: 97.6-99.3%) were seropositive post-booster. Of 46 travellers who received a booster ≥3 years after PrEP, all were seropositive post-booster.

CONCLUSIONS

In older travellers, the 1IDx3 schedule was the most effective, and a high proportion were seropositive post-booster even many years after a primary course.

Structures of the Mononegavirales Polymerases

Mononegavirales, known as nonsegmented negative-sense (NNS) RNA viruses, are a class of pathogenic and sometimes deadly viruses that include rabies virus (RABV), human respiratory syncytial virus (HRSV), and Ebola virus (EBOV). Unfortunately, no effective vaccines and antiviral therapeutics against many Mononegavirales are currently available. Viral polymerases have been attractive and major antiviral therapeutic targets. Therefore, Mononegavirales polymerases have been extensively investigated for their structures and functions.

Mononegavirales, known as nonsegmented negative-sense (NNS) RNA viruses, are a class of pathogenic and sometimes deadly viruses that include rabies virus (RABV), human respiratory syncytial virus (HRSV), and Ebola virus (EBOV). Unfortunately, no effective vaccines and antiviral therapeutics against many Mononegavirales are currently available. Viral polymerases have been attractive and major antiviral therapeutic targets. Therefore, Mononegavirales polymerases have been extensively investigated for their structures and functions. Mononegavirales mimic RNA synthesis of their eukaryotic counterparts by utilizing multifunctional RNA polymerases to replicate entire viral genomes and transcribe viral mRNAs from individual viral genes as well as synthesize 5′ methylated cap and 3′ poly(A) tail of the transcribed viral mRNAs. The catalytic subunit large protein (L) and cofactor phosphoprotein (P) constitute the Mononegavirales polymerases. In this review, we discuss the shared and unique features of RNA synthesis, the monomeric multifunctional enzyme L, and the oligomeric multimodular adapter P of Mononegavirales. We outline the structural analyses of the Mononegavirales polymerases since the first structure of the vesicular stomatitis virus (VSV) L protein determined in 2015 and highlight multiple high-resolution cryo-electron microscopy (cryo-EM) structures of the polymerases of Mononegavirales, namely, VSV, RABV, HRSV, human metapneumovirus (HMPV), and human parainfluenza virus (HPIV), that have been reported in recent months (2019 to 2020). We compare the structures of those polymerases grouped by virus family, illustrate the similarities and differences among those polymerases, and reveal the potential RNA synthesis mechanisms and models of highly conserved Mononegavirales. We conclude by the discussion of remaining questions, evolutionary perspectives, and future directions.

Modern biologics for rabies prophylaxis and the elimination of human cases mediated by dogs

Introduction: Rabies is a major viral zoonosis and neglected tropical disease, with a global distribution. Humans, domestic animals, and wild mammals are susceptible to infection. Etiological agents reside in the Order Mononegavirales, Family Rhabdoviridae, Genus Lyssavirus. This acute, progressive encephalitis causes the highest case fatality of any conventional infectious disease. Tens of millions of humans become exposed annually to the bites of infected mammals, predominantly in Asia and Africa. Despite the existence of effective vaccines and immune globulins, tens of thousands of people, typically children in the developing world, succumb. Areas covered: Concentrating upon both historical and major published references from the peer-reviewed literature over the past 5 years, we describe current biologics for rabies prevention, newly recommended principles for prophylaxis, and relevant future products in the developmental pipeline. Expert opinion: Modern human rabies biologics are pure, potent, safe, and efficacious, when used in a timely and appropriate manner. Few individuals survive after clinical signs. Anti-viral compounds are not licensed. Experimental therapy, while obviously desirable, is highly controversial. Education on bite prevention and integrated risk management are critical. Access to affordable care, dose-sparing, and shortened regimens of human rabies biologics remain key.

Emerging viruses and current strategies for vaccine intervention

During the past decade several notable viruses have suddenly emerged from obscurity or anonymity to become serious global health threats, provoking concern regarding their sustained epidemic transmission in immunologically naive human populations. With each new threat comes the call for rapid vaccine development. Indeed, vaccines are considered a critical component of disease prevention for emerging viral infections because, in many cases, other medical options are limited or non‐existent, or that infections result in such a rapid clinical deterioration that the effectiveness of therapeutics is limited. While classic approaches to vaccine development are still amenable to emerging viruses, the application of molecular techniques in virology has profoundly influenced our understanding of virus biology, and vaccination methods based on replicating, attenuated and non‐replicating virus vector approaches have become useful vaccine platforms. Together with a growing understanding of viral disease emergence, a range of vaccine strategies and international commitment to underpin development, vaccine intervention for new and emerging viruses may become a possibility.

Stable Immune Response Induced by Intradermal DNA Vaccination by a Novel Needleless Pyro-Drive Jet Injector

DNA vaccination can be applied to the treatment of various infectious diseases and cancers; however, technical difficulties have hindered the development of an effective delivery method. The efficacy of a DNA vaccine depends on optimal antigen expression by the injected plasmid DNA. The pyro-drive jet injector (PJI) is a novel system that allows for adjustment of injection depth and may, thus, provide a targeted delivery approach for various therapeutic or preventative compounds. Herein, we investigated its potential for use in delivering DNA vaccines. This study evaluated the optimal ignition powder dosage, as well as its delivery effectiveness in both rat and mouse models, while comparing the results of the PJI with that of a needle syringe delivery system. We found that the PJI effectively delivered plasmid DNA to intradermal regions in both rats and mice. Further, it efficiently transfected plasmid DNA directly into the nuclei, resulting in higher protein expression than that achieved via needle syringe injection. Moreover, results from animal ovalbumin (OVA) antigen induction models revealed that animals receiving OVA expression plasmids (pOVA) via PJI exhibited dose-dependent (10 μg, 60 μg, and 120 μg) production of anti-OVA antibodies; while only low titers (< 1/100) of OVA antibodies were detected when 120 μg of pOVA was injected via needle syringe. Thus, PJI is an effective, novel method for delivery of plasmid DNA into epidermal and dermal cells suggesting its promise as a tool for DNA vaccination.

The Cellular Immune Response to Rabies Vaccination: A Systematic Review

The effectiveness of rabies vaccines is conventionally determined by serological testing. In addition to this assessment of humoral immunity, cellular immunity could help assess effectiveness and protection through a broad range of parameters. Therefore, this study aimed to systematically review all literature on the kinetics and composition of the cellular immune response to rabies vaccination in humans. A total of 1360 studies were identified in an extensive literature search. Twenty studies were selected for inclusion. In a primary response, plasma cells are detectable from day 7 to day 14, peaking at day 10. Memory B-cells appear from day 10 up to at least day 28. After revaccination, natural killer (NK) cells are the first detectable cellular parameters. Further research is required to assess cellular parameters in relation to long-term (serological) immunity. This review was registered in the International Prospective Register of Systematic Reviews (PROSPERO) under registration number CRD42019134416.

Cost Savings of Using Updated Thai Red Cross Intradermal Regimen in a High-Throughput Anti-Rabies Clinic in New Delhi, India

Replacement of the Essen intramuscular (EIM) by the updated Thai Red Cross intradermal (UTRCID) regimen for rabies post-exposure prophylaxis (PEP), in high-throughput hospitals of India, has been advocated since 2006 thanks to its cost-effectiveness. However, several anti-rabies clinics in India and other parts of the world have not initiated this switchover of regimens because of the paucity of financial literature, generated in realistic settings, regarding the same. We calculated the procurement costs of various items required for providing rabies vaccinations via the EIM regimen and UTRCID regimen, on an annual basis, a year before and after the switchover. From a healthcare provider’s perspective, the cost of vaccination per patient was calculated to be 5.60 USD for the EIM regimen and 2.40 USD for the UTRCID regimen. The switchover to the UTRCID regimen from the EIM regimen reduced the financial burden of the rabies vaccination by almost 60%. Procurement of vaccine vials contributed to the majority of the cost (>94%) in both of the regimens. Procurement of syringes with fixed needles contributed negligibly (<6%) to the financial burden in both the regimens. A policy to progressively switch over to the UTRCID regimen from the EIM in all high-throughput anti-rabies centers of India would dramatically reduce the economic burden of running a successful anti-rabies program.