Similarities between pandemic influenza viruses

Scientists from the Mount Sinai School Medicine (New York) recently publish an interesting paper about the similarities between two viruses, namely the Spanish influenza virus and H1N1. The Spanish influenza virus caused a incredible number of death in 1918 during the first world war, worldwide. This virus is formerly extinct and for this reason it could be used as a bioterrorist agent. The comparison between the Spanish influenza virus and H1N1 demonstrates an homology of antigenic sites of haemagglutinin A. This observation induced scientists to investigate whether mice and humans previously vaccinated against H1N1 were also immunized against the Spanish influenza virus. Human sera containing antibodies anti-HA were collected and passively transferred into mice infected with the Spanish influenza virus and protected them from lethality. Thus, immunization against H1N1 protects also from the Spanish influenza virus infection. In case of bioterrorist attack or accidental virus escape from scientific laboratories the emergency could be easily managed. This study is pionieristic and other researches could be done to identify similarities between viruses. Such as approach, it could be useful to validate current therapies against other viral target, diminishing the cost of clinical trial required to market new anti-viral drugs.

December 1st, the AIDS day

December 1st is the AIDS day and around the world conferences, events and discussions remember us what serious consequence on human health has this epidemics. December 1st has been chosen because the first case of AIDS was diagnosed in 1981 on this date. Since 1980s, numerous information about HIV infection have been collected and published in scientific literature. Acquired immunodeficiency syndrome is a condition in which the immune system is less efficient because of viral infection and human body is more susceptible to opportunistic diseases and tumours. Everyone knows the modality of contamination through infected blood or seminal liquid or breast milk; everyone knows about the possible therapies to arrest viral infection.

Nevertheless, AIDS still kill a lot of people, specially in poorer countries such as Sub Saharan Africa where more the one million victims were counted in 2007. Education and prevention are challenges that poor countries must gain if they want to survive. Of course, the contribution of developed countries is not dispensable. Giving the difficult management of the infection with antiretroviral drug and keeping in mind that the vaccine is not available yet, unique way to fight this pandemics is the sensitization to acquire a preventing behaviour. Promotion of safe sex and needles exchange is an attempt to slow virus spread, whereas to limit mother to child infection, breast feeding should be stopped as soon as possible or not started at all. A lot of work should be done because infected people don’t know to be sick or how to protect the life of their parents or children. Humanitarian organizations, either institutional or no-profit, try to overcome all cultural and logistic problem for helping people to take care themselves. Several research laboratories continue their study to better understand the complex biology of retrovirus and specially the human immunodeficiency virus. HIV firstly infects CD4+ T cells, dendritic cells and macrophages and kills them by causing apoptosis, necrosis or activating CD8+ cytotoxic lymphocytes to eliminate infected cells. Clarifying the mechanism of infection has allowed to develop some specific anti-retroviral drugs that interfere and block crucial steps during the infection. It could be useful and ethical that all works would be published and available for free for all scientists around the world in order to fast the scientific advances in this field. Again, it could be also useful that the patents of anti-HIV drugs should be shortened and generic and less expensive drugs should be available for everyone to prolong survival. A sick person could die within one year during diagnosable AIDS phase in absence of antiretroviral treatment, so it’s really important that these therapies would be immediately provided in large scale. Despite the actual measures to fight AIDS, few years ago AIDS denialism was sustained by some governments and scientists, causing an unforgettable delay to save population. We hope that December 1st still induce us to reflect about AIDS, its victims and its social implications.

Comparison between Baculovirus and E. Coli, as expression system

Baculovirus expression system is commonly used for protein expression, in particular it is used for eukaryotic proteins that cannot be correctly folded in E. Coli. This virus, not infectious for human, infect insect cells, such as Sf9, Sf21 or Hi5, and are isolated to performed high amount of recombinant proteins. Indeed, Baculovirus genome could be easily modified with current molecular biology techniques –molecular cloning, following by recombination and transposition- and propagated in normal cellular biology lab, not P2 or P3 chambers are necessary to use this virus. It’s possible to insert long fragment of exogenous DNA into virus genome, this aspect is important and represent a good advantages in respect of E. Coli because eukaryotic proteins are usually codified by long genes.

Another significant advantage is the capability to introduce post-translational modifications, such as phosphorylation, glycosilation that are necessary to obtain the complete functionality of the recombinant protein. Thus, proteins produced with this system could be employed for instance in biochemical assays, after purification, and in screening of pharmacological compounds. By contrast, the main disadvantages associated with Baculovirus are the cost and the yield: insect cells culture is more expensive than E. Coli culture, because of the media, sera and molecular reagents necessary to make the transfection. Furthermore, the yield is lower and if 1 mg of recombinant protein can be produced form 1 litre of E. Coli culture, much more litres of insect cells are necessary to produce the same amount of protein.
What are the parameters important to choose one type of expression system in respect of another one? Firstly, it has to be known very well the protein that has to be produced: literature review gives interesting suggestions and the most common expression system is usually the best one. Secondarily, the aim of the study is important, indeed if a functional study has to be performed, it’s crucial to have an active protein also in a little amount, by contrast for crystallization study is important to consider that milligrams of protein have to be purified. Finally, both Baculovirus and E. Coli are tool easy to use, but in the case of Baculovirus some experience in cellular biology rather than biochemistry is important. The timing has also to be considered because Baculovirus-insect cell system requires at least one month, after cloning, to perform first infections; by contrast, E. Coli needs only cloning procedures to express the protein of interest. Both recombinant viruses and bacteria can be frozen, in order to have reagents ready to use, it’s important keep sterility and a great classification if numerous proteins are studied at the same time in the lab: special software are commercially available for this purpose. In conclusion, both techniques are useful in biochemistry, structural biology and molecular biology and in respect of the aim of the study is crucial to choose the more convenient one.

miRNomics

Recent studies demonstrate an increased importance of miRNA in regulating cell function, in particular in stem cells or during embryo development, otherwise deregulated expression of miRNA often causes diseases, such as cancer. miRNAs have been identified in viruses, plants and animals and regulate protein expression by inducing degradation of mRNA target.
miRNA are short RNA sequences that recognize from ten to hundred mRNA targets, usually identified by computational analysis. Several software based on homology search and/or other parameters (free energy of folding, length of symmetric stem, A C G U content) allow us to identify mRNA targets and recognize miRNA sequence inside the genome. In April 2009 (Curr Biol. 2009 Apr 15) Dr Hervè Seitz form the University of Massachusetts Medical School proposes a new role of messenger, target of miRNA.

He wrote: “Many computationally identified miRNA targets may actually be competitive inhibitors of miRNA function, preventing miRNAs from binding their authentic targets by sequestering them”. He proposed a new model to explain the regulation of miRNA activity, based on expression of mRNA target and not on expression of miRNA itself. Once again, it’s fundamental the synergy between biological experiments and computational analysis to obtain straightforward data and enrich our knowledge of miRNome.