Shampur Narayana Madhusudana

Antemortem diagnosis and prevention of human rabies.

Human rabies still continues to be a significant health problem in India and other developing countries where dogs are the major vectors of transmission. Rabies in humans can present in two clinical forms, i.e., furious and paralytic. While diagnosis of furious rabies can be made based on the typical symptoms and signs, paralytic rabies poses a diagnostic dilemma to the neurologists who may encounter these cases in their practice. Although there are certain clinical features that distinguish this disease from other forms of Guillain-Barre syndromes, confirmation of diagnosis may require laboratory assistance. Conventional techniques such as antigen detection, antibody assays and virus isolation have limited success. The recently introduced molecular techniques show more promise in confirming the cases of paralytic rabies. There has not been much success in the treatment of confirmed rabies cases and recovery from rabies is extremely rare. Therefore, preventive measures of this dreaded disease after an exposure become extremely important. The present article reviews the current status of human rabies with regard to antemortem diagnosis, disease management and post-exposure prophylaxis.

Role of Apoptosis in Rabies Viral Encephalitis: A Comparative Study in Mice, Canine, and Human Brain with a Review of Literature

To evaluate the role of apoptosis in rabies encephalitis in humans and canines infected with wild-type street virus, in comparison with rodent model infected with street and laboratory passaged CVS strain, we studied postmortem brain tissue from nine humans, six canines infected with street rabies virus, and Swiss albino mice inoculated intramuscularly (IM) and intracerebrally (IC) with street and CVS strains. Encephalitis and high rabies antigen load were prominent in canine and human brains compared to rodents inoculated with street virus. Neuronal apoptosis was detectable only in sucking mice inoculated with CVS strain and minimal in street virus inoculated mice. In a time point study in suckling mice, DNA laddering was noted only terminally (7 days p.i.) following IC inoculation with CVS strain but not with street virus. In weanling and adult mice, apoptosis was restricted to inflammatory cells and absent in neurons similar to human and canine rabies-infected brains. Absence of neuronal apoptosis in wild-type rabies may facilitate intraneuronal survival and replication while apoptosis in inflammatory cells prevents elimination of the virus by abrogation of host inflammatory response.

A comparative study on the safety and immunogenicity of purified duck embryo cell vaccine (PDEV, Vaxirab) with purified chick embryo cell vaccine (PCEC, Rabipur) and purifed vero cell rabies vaccine (PVRV, Verorab)

Rabies is a fatal but preventable disease. Cell culture vaccines (CCV) and purified duck embryo vaccines (PDEV) are currently recommended by WHO for post-exposure prophylaxis. In India, a PDEV (Vaxirab) is being manufactured and is in use since 2003. In the present study, we have evaluated the safety, immunogenicity and tolerance of this vaccine with two other WHO approved CCVs, viz., purified chick embryo cell vaccine (PCEC, Rabipur) and purified vero cell rabies vaccine (PVRV, Veroroab). This study was an open label, randomized phase IV comparative clinical trial. A total of 152 people bitten by dogs and other animals were recruited from 4 different centres from India. They were randomly assigned to receive one of the vaccines by Essen intramuscular regimen (52 subjects received Vaxirab and 50 each Rabipur and Verorab) and rabies immunoglobulin was also administered in all category III exposures. Their blood samples were collected on day 0 (prior to vaccination), 14, 28, 90 and 180. Side effects if any were monitored. The rabies neutralizing antibody titers in their blood samples were estimated by the rapid fluorescent focus inhibition test (RFFIT). Subjects in all three groups had neutralizing antibody titers by day 14 (>0.5 IU/mL) and geometric mean titers (GMT) observed for different vaccines on all days tested did not vary significantly (p>0.5). Side effects observed were minimal and did not vary significantly among the groups. The results of the present study indicate that PDEV (Vaxirab) is as safe, tolerable and immunogenic as both PCEC (Rabipur) and PVRV (Verorab). Thus this vaccine can be a good alternative to WHO approved CCVs for rabies post-exposure prophylaxis.

Safety and immunogenicity study of a new purified chick embryo cell rabies vaccine Vaxirab-N (Pitman–Moore strain) manufactured in India

Zydus Cadila Health care, India developed a new purified chick embryo cell rabies vaccine (PCECV, Vaxirab-N; 1 mL) by adapting Pitman–Moore strain of virus on to the chick embryo fibroblast cell line in 2006. During 2007–10, a series of safety and immunogenicity studies were conducted as per ICH-GCP guidelines after obtaining permission from Drug Controller General of India. In the first study, Vaxirab-N was administered to 35 healthy adult volunteers by intramuscular (IM) route using pre exposure regimen. The geometric mean concentration (GMC) of rabies virus neutralizing antibody (RvnAb) of 7.5 IU/mL on day 35. In the second study, Vaxirab-N was administered to 35 healthy adult volunteers using simulated post- exposure prophylaxis regimen by IM route. A GMC of 6.3 IU/mL on day 14, 13.2 IU/mL on day 28 and 8.6 IU/mL on day 90 was obtained. In the third study, Vaxirab-N administered by intradermal (ID) route using Updated Thai Red Cross (TRC) regimen in 36 healthy adult volunteers showed GMC of 7.8 IU/mL on day 14, 11.5 IU/mL on day 28 and 6.0 IU/mL on day 90. The 4th study was multi centric and Vaxirab-N was administered to 129 animal bite cases by IM route using post-exposure Essen regimen. The GMC following this schedule was 8.2 IU/mL on day 14, 13.01 IU/mL on day 28, 7.92 IU/mL on day 90 and 3.72 IU/mL on day 180. Mild to moderate adverse events were reported to Vaxirab-N but no serious adverse events were reported in any of these studies. In conclusion, Vaxirab-N developed by Zydus Cadila was found to be safe and immunogenic by both intramuscular and intradermal route and is recommended for rabies prophylaxis (CTRI No. 2010/091/000055 and 2010/091/000509).

Rabies viral encephalitis with proable 25 year incubation period

We report a case of rabies viral encephalitis in a 48-year-old male with an unusually long incubation period, historically suspected to be more than 20 years. The case was referred for histological diagnosis following alleged medical negligence to the forensic department. The histology and immunocytochemical demonstration of rabies viral antigen established the diagnosis unequivocally. The case manifested initially with hydrophobia and aggressive behavior, although he suddenly went to the bathroom and drank a small amount of water. History of dog bite 25 years back was elicited retrospectively following clinical suspicion. There was no subsequent history to suggest nonbite exposure to a rabid dog to consider recent event causing the disease, although this cannot be totally excluded.

Comparative study on the immunogenicity and safety of a purified chick embryo cell rabies vaccine (PCECV) administered according to two different simulated post exposure intramuscular regimens (Zagreb versus Essen)

Despite availability of effective rabies vaccines, India has the highest global mortality rate for rabies. Low socio-economic communities are most affected due to lack of awareness of the disease and poor compliance to post-exposure prophylactic regimens. Currently, the only approved intramuscular regimen for post-exposure prophylaxis (PEP) against rabies in India is the Essen regimen, which consists of 5 injections administered over 5 separate days in a period of one month. The high number of doses and clinical visits, however, are major reasons for non-compliance, and thus a shorter regimen would be beneficial. In a simulated PEP trial in healthy, adult subjects, this study evaluated whether purified chick embryo cell vaccine (PCECV), administered according to the WHO-recommended 4-dose/3 visit Zagreb vaccination regimen is of equal immunogenicity and safety as the standard Essen regimen in Indian subjects. Two hundred and 50 healthy adults were enrolled and randomized into a Zagreb or Essen group, each receiving PCECV according to their respective regimen. Blood samples were collected on Days 0, 7, 14 and 42 and analyzed using the rapid fluorescent focus inhibition test (RFFIT). By Day 14, all subjects across both groups attained rabies virus neutralizing antibody (RVNA) concentrations of ≥ 0.5IU/ml. The Zagreb regimen was then demonstrated to be immunologically non-inferior to the Essen regimen by Day 14, which was the primary endpoint of the study. No safety issues were noted and the occurrence of adverse events was similar in both groups (17% and 15%, respectively). NCT01365494. CTRI No.: CTRI/2011/07/001857

Tracking the footprints of the rabies virus: are we any closer to decoding this elusive virus?

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