“It’s an honor to announce that we’ve successfully discovered, cloned & characterized the densonucleosis virus (DNV) Antigen, which will be able to infect Anopheles gambiae. That will hinder its ability to transmit Malaria parasite, Plasmodium or, at least, reduce its lifespan. I’ve to tell you this: This will be the latest in Malaria control.” Well.. those are my words but, of course, it is not my discovery. It’s the team of researchers from Johns Hopkins who discovered it. To realize how big it’s; we first need to know the previous approaches & trials in Malaria control.

To think, just think, about control/ prevention of any of those vector-borne parasites; automatically researchers think about these:
1- Prevent infection – disease – transmission.
2- By looking at: the parasite’s life cycle – the mosquito – the human immune system.
3- So, it’ll look like that: get humans vaccinated – develop genetically modified mosquitoes incapable of transmitting the parasite or simply “I was so naive to think that it’s simple” kill them with insecticides (anti-vector measures) – target the parasite at any stage of its life cycle.

For decades, DDT (dichloro-diphenyl-trichloroethane) & Chloroquine were successfully used in eradication of Anopheles & Plasmodium respectively, “I do like this word, makes me sound like a pro”. Chloroquine was used in treatment as well as prevention, till the emergence of chloroquine-resistant Plasmodium parasites and DDT-resistant Anopheles mosquitoes. Yes, they overcame the humans’ arsenal. So, preventing spread of resistant parasites is the #1 priority.

We can’t talk about all control strategies today, so we’ll talk about anti-vector measures. What do they use in control programs as anti-vector measures?
1- Insecticide-treated bednets (ITNs) & long-lasting ITNs (LLINs) it helped kids to survive. The only allowed insecticides to be used in ITNs are pyrethroid insecticides, so when the pyrethroid resistance emerged, as usual, it was really bad.
2- Indoor residual spraying (IRS) using DDT
One word about the mechanism of action of DDT & pyrethroids, both target voltage-gated Na-channels. So, when a set of mutations change the protein structure; Congratulations! It’s resistance to both DDT & pyrethroids.
3- New approach: Molecular talk; Know more about “blood meal” host selection. Yes, Anopheles smells the host, so researchers want to identify that pathway.
4- Another new approach: They are investigating genes which encode proteins that may interrupt the development of the parasite in the Anopheles.

The latest as an anti-vector measure is using Paratransgenesis or “the genetic manipulation of insect symbiotic (mutualistic, commensal or parasitic) microorganisms”, I can’t get the term or the definition. I’ll say it like that: “Any other m.o. has a relationship with the vector”. The steps are:
1- Know the Ag (Pick the gift)
2- Get the gene(s) engineered to be successfully expressed (Wrap the gift)
3- Delivery to Anopheles (Deliver the gift)
So the gift will be the non-enveloped ssDNA virus called (DNV). Its genome is very small, when they say for a viral genome that it’s small, so it has to be small (4–6 kb). The entire genome can be placed in a plasmid.

Back to the story of the discovery, they were doing a totally unrelated experiment when they found that strange band/ zone. They isolated it from the gel, cloned, sequenced, ran through BLAST which showed that it looks like DNV of Aedes aegypti (AeDNV) but not the man himself. They did multiple tests to identify the Ag, e.g. Immunofluorescence assay. There was a trial to infect Anopheles gambiae with DNV of Aedes aegypti which wasn’t successful in infecting adults from Anopheles gambiae. But the novel “AgDNV is highly infectious to An. gambiae larvae, disseminates to adult tissues, and is passed on to subsequent generations.”

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Aetiology and epidemiology

Meninigococcal meninigits and septicemia are devastating diseases caused by Neissieria meningitidis. Although infants and young children are the most susceptible to the disease, adults are also affected but with less incidence. N.meningitidis is a gram negative capsulated bacterium that has been classified into five serogroups (A, B, C, Y, W135)  based on their polysaccharide capsule.

The challenge

Over forty years, developing a vaccine against this dangerous bacterium proceeded with little success. In 1960, the purified polysaccharide antigens were used to develop a vaccine against four groups (A, C, Y, W135) . Unfortunately, this vaccine was highly effective in adults but didn’t give protection to young infants and children who represent the age group most susceptible to the disease. Another challenge is that this vaccine didn’t show success against serogroup B (known as:MenB).

More attempts to overcome the new challenge

Using capsular polysaccharide antigen, as a vaccine against MenB, wasn’t a very good idea. This is due to the fact that MenB capsular polysaccharide is highly similar (nearly identical) to N-acetyl neuraminic acid which is widely distributed in human tissue and that means it is a self antigen. The new vaccine was poorly immunogenic (and thus provide poor protection) and also it might elicit auto-antibodies.

As scientists never give up, they switched into the new trend in vaccinology: Reverse vaccinology. Due to the formerly mentioned, N.meningitidis was expected to be a very promising candidate for reverse vaccinology.

RV provides help

Using in silico technique (computational biology), the genome sequence was fed into a computer, 570 proteins of the bacterium surface were predicted. Going for more refinement, only 350 of these proteins were successfully expressed in E.coli and and used to immunise mice. The sera assays allowed the identification of certain proteins that elicit bactericidal antibodies and surprisingly, were conservative among different strains and this meets the criteria for a good vaccine.

Going forward

As research is proceeding to deprive our pathogen from enjoying its life inside our bodies, this work suggested further research of other pathogens such as: Streptococcus pneumoniae, Chlamydia pneumoniae, Bascillus anthracis, T.B and group B Streptococcus. 

Reference:

A universal vaccine against serogroup B meningococcus.

For many decades, conventional vaccinology has faced many obstacles. One major problem is that among several antigens of the microbe, you have to identify the most immunogenic (and thus protective) antigens (such as virulent factors, toxins, surface-associated proteins, etc.) suitable for vaccine development. This process is very fastidious and costs a lot as it relies mainly on traditional biochemical and microbiological methods. As a summary, it is carried out as following:

• Firstly, you have to cultivate the microbe and harvest proteins.
• Then you have to identify the antigens one by one.
• After that you can pass to vaccine development stage.

Introducing genomics has greatly contributed to providing a new impulse to vaccinology field. The major role it plays is in the antigen discovery stage. As the genome sequence of many microbes has been identified, the integration between the sequence, proteomics and microarray has introduced what is called “reverse vaccinology” . Reverse vaccinology (RV) means to identify and characterise the antigen using bioinformatics. In RV, you start from the genome and not from the pathogen itself i.e.  you start from the opposite direction, that’s why it is called “reverse”.

RV will provide solutions to some problems that usually come up during vaccine development as:

• It will provide fast access to almost all antigens including:less common antigens and antigens not expressed in vitro.
• It represents a new approach for non culturable microorganisms.

On the other hand, the major disadvantage of RV is that it cannot be applied to non-proteinaceous antigens such as lipopolysaccharides and glycolipids.

Two years ago, the project of sequencing the Neanderthal genome started. They (Max Planck Institute & 454 Life sequencing) promised to end by this year. Well, they kept their promise. Frankly, some mitochondrial DNA sequences (mtDNA) have been published but contamination was the major defect in those published sequences. They collected more than 60 bone specimens from museums (We’re talking about 38,000-year-old bone); they repeated the sequencing for 35 times in the same clean room of extraction to avoid contamination with human DNA.

From the total 13 protein-encoding genes of the sequenced mtDNA, they identified only one with amino acids difference than the human sapien version. It is cytochrome c oxidase subunit 2 (COX2 – part of the respiratory chain), but even this difference has no significant effect on the functional domain of COX2. They hope to answer this questions in a few months: Why Neanderthals died out & human didn’t?!

We already know that Neanderthals & humans share 99.5% of the sequence, but answering questions about having a common ancestor & extinction through absorption (bred with humans) needs lots & lots of researches, collecting & sequencing samples at different time intervals to come with hypotheses. The mtDNA is not enough as Trinkaus (an expert on Neanderthal biology and human evolution) said: “The genome sequence data may tell us something about the selection of a couple of proteins, but it tells us nothing about language or social behavior.”

Image credits:
Reconstruction of a Neanderthal child from Gibraltar: http://en.wikipedia.org/
First complete Neanderthal genome sequenced: http://www.nature.com/

Once upon a time, in 2003, a French team discovered a giant virus infects amoeba. It was isolated from a cooling tower in the UK. They were so excited because it was so huge with a genome contains 900 protein-encoding genes (The words giant/ huge are totally hilarious. It’s not “Hulk”, it’s just a virus). It’s visible under the optical microscope. They named it Acanthamoeba polyphaga mimivirus (APMV). The prefix “mimi” is for mimicking microbe. Now, the same team “Raoult’s team” reported the isolation of another strain of those giant viruses but this time it was isolated from a cooling tower in Paris. They named it “mamavirus” because it was slightly larger than the previous giant virus (APMV), but it wasn’t alone. It was associated with its satellite, a small virus has 21 protein-encoding genes infects it, hijacks its viral factory making copies of itself, hindering the ability of the mamavirus to replicate/ make its own copies, so the number of the mamavirus drops in the infected amoebae. They named it Sputnik after the first man-made satellite. It’ll be the first isolated “Virophage”. How did I know about it? From the amazing blog of Dr. Ramy K. Aziz, “Microbes“.

The story won’t stop at this discovery. The discovery of the virophage will strongly suggest that “Viruses are alive” because they share something with other living domains of life, they can be infected, they can get sick, what makes all health-care providers totally thrilled because there’s something stronger than viruses which could be used to fight them, but “It’s too early to say we could use Sputnik as a weapon against big viruses or to modify them,” says co-author Bernard La Scola.

One more thing about Sputnik, 3 of its genes are closely related to APMV which suggests horizontal gene transfer between giant viruses caused by Sputnik. This is so “bacteriophagic”, reminds me with the whole insertion/ lysogenic mechanism between phages & bacteria. The isolated sequences from the ocean are closely related to the genome sequences of giant viruses & their satellite (Sputnik) . They infect plankton. “It suggests there are other representatives of this viral family out there in the environment,” Koonin says.

Image credits:
Giant mamavirus particles (red) and satellite viruses of mamavirus called Sputnik (green). http://www.nature.com/

To be frank, I was really underestimating these bacteria. Streptococcus iniae, bacteria bothering fish, what’s the big deal? But when I read that it cause them meningoencephalitis due to systemic dissemination resulting in death, it made me sad. They’re fish, you know, they don’t deserve such destiny. (We can’t say that about eating them, right?) Back to scientific details, S. iniae was isolated from Amazon dolphins (Inia) but it has a very wide host range, it can infect fresh & saltwater species like salmon, yellowtail & hybrid striped bass (HSB). It also can infect immunocompromised as well as elders from humans.

S. iniae are beta-hemolytic streptococci, they have M protein (present in cell membrane) then the capsular polysaccharide which interfere with phagocytosis. They also have phosphoglucomutase which make their cell wall rigid & resistant to peptide antimicrobials, besides their streptolysin S. I’ve to tell you this, this iniae is a walking disaster, just like the human version S. pyogenes.

So what scientists tell us this time? Thanks to 454 pyrosequencing & bioinformatics, they identified extra virulence factors of S. iniae. Regulations in S. iniae are done through a Mga-like Mgx loci (multiple gene regulator of group A streptococci). It regulates the virulence factors. It’s used to be known that M-protein is a component of that Mga. This time, discovery of extra components takes place, the M-like surface protein (simA) & C5a peptidase (scpI). A word about scpI, its role is to inactivate C5a (the complement component) to hinder the complement reaction & also has a role in adhesion to epithelial cells.

Actually they’re looking forward to using the mutant delta-simA as a live attenuated vaccine against S. iniae. (Vaccine for fish?) They made mutations in both C5a-like peptidase & simA, apparently simA had the leading role in the virulence of the studied strain of S. iniae. So a new approach of vaccination will be developed instead of the old M protein vaccination strategy which requires multimeric vaccination (to provide protection against several serotypes) & showes autoimmune response. Unlike the ordinary M protein vaccination, vaccination with the mutant delta-simA will result in development of humoral as well as cell-mediated immunity.

Image credits:
Fish – Cartoon: http://www.robdoyle.co.uk/