impaginato piccolo - Società Italiana di Parassitologia (SoIPa)

Parassitologia 50: 137-140, 2008
The role of research in molecular entomology in the fight
against malaria vectors
A. della Torre 1, B. Arca 2, G. Favia 3, V. Petrarca 4 , M. Coluzzi 1
1 Sezione di Parassitologia, Dipartimento di Scienze di Sanità Pubblica, Università “La Sapienza”, Italy; 2 Dipartimento di
Biologia Strutturale e Funzionale, Università Federico II, Napoli, Italy; 3 Dipartimento di Medicina Sperimentale e Sanità
Pubblica, Università di Camerino, Italy; 4 Dipartimento di Genetica e Biologia Molecolare, Università “La Sapienza”, Italy.
Abstract. The text summarizes the principal current fields of investigation and the recent achievements of
the research groups presently contributing to the Molecular Entomology Cluster of the Italian Malaria
Network. Particular emphasis is given to the researches with a more direct impact on the fight against malaria
vectors.
Key words: Anopheles gambiae, genomics, vector control, malaria epidemiology.
In 1990, the UNDP/World Bank/WHO Special
Programme for Research and Training in Tropical
Diseases (TDR), together with the John D. and
Catherine T. MacArthur Foundation and the University
of Arizona, convened a meeting in Tucson, Arizona,
where specialists in entomology, genetics and biochemistry
were brought together to discuss the prospects for
malaria control by genetic modification of the vector
competence of natural vector populations. That meeting
can be considered as the birth of modern medical entomology
and, since then, an extraordinary amount of
research has been carried out on malaria vectors, with
particular focus on Anopheles gambiae, the principal
vector of malaria in sub-Saharan Africa. Studies carried
out in the last two decades led to major scientific
advances, such as the genome sequencing and the stable
germ-line transformation of A. gambiae, the engineering
of laboratory strains refractory to Plasmodium infection
and, overall, to a deeper understanding of
Plasmodium/Anopheles interactions. Moreover, beside
these achievements - which are directed towards the
development of novel malaria control strategies that are
probably many years from reaching implementation -
several progress have been made in areas of molecular
entomology that are likely to have a more near-term
impact on malaria control. These include, among others,
the understanding, detection and monitoring of
some of the mosquito resistance mechanism against
insecticides, the determination of the genetic structure
of vector populations, the development of molecular
tools for the identification of cryptic taxonomic units
and a preliminary understanding of the molecular bases
of their ecology and behaviours.
Molecular entomology in Italy stemmed from the pioneering
studies by Mario Coluzzi and his first collaborators
in the University of Roma “La Sapienza” who,
Correspondence: Alessandra della Torre
Department of Public Health Sciences, Parasitology Unit,
"Sapienza" - University of Rome, P.le Aldo Moro, 5,
00185, Rome, Italy
Tel +39 06 4969 4268; Fax +39 06 4991 4653
e-mail: ale.dellatorre@uniroma1.it
since the years ’60, dedicated a large part of their scientific
career to the study of the genetic structure of
natural A. gambiae populations through the analysis of
the banding patterns of polytene chromosomes of the
nuclei of the ovarian nurse cells of half-gravid females.
The polytene chromosome map developed by Coluzzi’s
group has represented the basis for the international
effort leading to the A. gambiae genome sequencing
(Holt et al., 2002). Moreover, Coluzzi’s work has provided
the first molecular method for identifying the
members of the A. gambiae complex, differentially
involved in the malaria vector system, as well as
revealed the existence of intra-specific genetic variations
based on paracentric inversion polymorphisms
(reviewed in Coluzzi et al., 2002). In the last 15 years,
the group in Rome has been involved in a large variety
of molecular studies on A. gambiae, ranging from the
identification of sub-structuring within the major vector
species, A. gambiae sensu stricto (s.s.), the development
of molecular methods for the identification of
novel Operational Taxonomic Units (OTUs), the study
of their genetic and ecological divergence, the monitoring
of insecticide resistance spreading and the molecular
basis of Plasmodium/Anopheles interactions. The
groups presently contributing to the Molecular
Entomology Cluster of the Italian Malaria Network all
originated from the group in Rome, although had differentiated
their scientific targets. A brief description
of their principal current fields of investigation and of
their recent achievements is provided below, with particular
reference to those with a more direct impact on
the fight against malaria vectors.
The group of the University of Roma “La Sapienza” has
continued the studies initiated by Coluzzi by integrating
the cytogenetic approach with the molecular one.
The main result coming out from these combined
approaches has been the description of two “molecular
forms” (namely, M- and S-form) within A. gambiae s.s.
(della Torre et al., 2001; 2002). These forms have been
shown to be largely sympatric throughout west-Africa
and to be characterised by a high level of gene-flow
restriction and by a low degree of inter-form genetic
differentiation; moreover, paracentric inversions on