Acta Microbiologica Bulgarica

108-113

Authors: Nehra, C., Marwal, A., Gaur, R. K.

Begomoviruses are plant-infecting viruses, which are transmitted by the whitefly vector Bemisia tabaci and have been known to cause extreme yield reduction in a number of economically important vegetables around the world. They are abundant in tropical and subtropical environments, where insects that transmit these viruses are abundant. Identification of plant viruses, monitoring for new viral diseases, understanding the vectors that transmit viruses, and determining viral and vector impacts on the growth and development of crop cultivars and lines is vital to managing and controlling these diseases. In addition to damaging crops and causing yield losses, plant viruses interact with vectors and other diseases to increase the damage from the diseases/pests. The crops and weeds growing close to the crop fields are potential reservoirs of begomoviruses, but it is not known whether the same viruses infect several host species or co-infect any of the hosts. This increases the difficulty of controlling both the plant virus and the interacting pathogen or vector. In a survey carried out in 2011-14 we observed several cultivated crops, ornamental plants and weeds with leaf curling, vein yellowing and growth stunting - typical symptoms of begomovirus. The DNA was isolated from the infected samples and the presence of begomovirus was confirmed by PCR using component specific primers. Further, rolling circular amplification (RCA) was performed to get the full-length sequence of the isolates. The full length sequence showed genome arrangement typical of monopartite/ bipartite begomovirus. Some of the infected samples showed association of a betasatellite responsible for the epidemic diseases in the case of monopartite. Phylogenetic analysis confirmed the diversity of begomovirus in India. Our result also indicates that begomovirus has broaden its host range by recombination process. Expression of various full length or truncated or defective proteins of the virus has been effective in accomplishing pathogen-derived resistance. We analyzed the recombination parmeters of begomovirus strains and developed the RNAi strategy for the disease management.

121-125

Authors: Stoev, A.

The paper deals with the particularities in the manifestation of aggressiveness by phytopathogenic viruses and the methods of its tracing out and evaluation. Aggressiveness is a property of phytopathogens. We present some examples of viral pathogens which cause economically important diseases in the agroecosystems of Bulgaria. We have considered the manifestation of virus aggressiveness in association with other properties which characterize plant pathogens.

133-138

Authors: Dimitrova, A., Mileva, M., Krastev, D., Gegova, G., Galabov, A. S.

Influenza is a highly contagious viral infection of the respiratory system. Many studies provide compelling evidence that the abnormal production of reactive oxygen species is a crucial mediator of acute lung injury in influenza A virus infection. Therefore, antioxidants are potentially useful against this ongoing clinical problem. Our studies showed that S-adenosyl-L-methionine (SAM) has a protective effect in a model of influenza infection in mice. This substance converts into glutathione - the main antioxidant in the body, through a multistep biochemical cycle. In the present study, we report the effect of combined treatment with SAM and the antiviral agent oseltamivir in infected with influenza A virus mice. SAM was given as a single daily dose of 50 and 100 mg/kg in different mice groups, starting from 5 days before infection until day 4 after infection. Oseltamivir was given in a dose of 2.5 mg/kg daily in two intakes for 5 days, starting from 4 h before infection. End-point evaluation was 14 - day survival. Survival was 70% in the treatment with oseltamivir and rose to 90% in the treatment with oseltamivir and SAM in both doses. SAM alone did not show any antiviral activity. The present findings suggest that therapy with molecules converted into antioxidants in the body increases survival by modulating the host defense mechanisms and by a direct antioxidant effect against oxidative stress associated with viral infections. This study demonstrated the effectiveness of combining agents that act through different mechanisms - antiviral drug oseltamivir as a specific neuraminidase inhibitor of influenza virus, and SAM as a precursor of the most important antioxidant - glutathione.

142-147

Authors: Simeonov, K. B., Sirakov, I. N., Gergova, R. T., Koburova, K., Todorov, T. G.

In this study, the CPsittF(R) and Or1(2) primers, targeting the ompA gene of Chlamydia psittaci, were used for PCR detection of Chlamydia abortus DNA in clinical samples from aborted animals. The sensitivity and specificity of the reaction were compared with those achieved by C. abortus-specific primers CpsiA(B). The comparative analysis of the results showed that all samples that were positive for C. abortus in PCR, performed with primers CpsiA(B) also gave a positive result in the PCR using the CPsittF(R) primers, generating a 1041 bp specific amplification product. PCR amplification using the Or1(2) primers was uncertain and produced an amplification product of 212 bp, which was different from the expected length of 245 bp. In an attempt to improve these primers, their sequence was modified at the 11th and the 21st nucleotide. Although the sensitivity of the reaction performed with the modified primers was improved, it was still lower compared to that achieved with the original C. abortus-specific primers CpsiA(B) and primers CPsittF(R). The results show that the primer pair CPsittF(R), developed for the detection of C. psittaci could be successfully used in the diagnosis of abortions, induced by C. abortus, while the primer set Or1(2) is less effective.